China CNC routers - 3020 oldschool vs. 3018 GRBL control

[TinkeringSteve]

Hello there!

I hope, and I can imagine, that this is the right forum where to find people who have gained some experience with devices like this.
I've done some little research lately about those different kinds of chinese CNC *routers*.


Basically, there seem to be two kinds:

1) newer, usually weaker ones, sold as wood engravers, which already have support for GRBL control, and you can see people on youtube runnig open source software that captures a heightmap of e.g. a copper board with a simple electrical contact, befor the actual milling, to get more precise results and all that.
These are called e.g. cnc 1610, 3018 (for 16x10 or 30x18 cm² max. work piece size)
and have something like a 150W motor driving the tool. Often there are many plastic parts holding the corners together.

2) older style, usually more metal, less plastic, at least 300W, up to 2.2kW motor, sometimes up to 4 axes, and people do actually use them to mill softer metals.
They are called e.g. CNC 3020, or 6040, for their resp. sizes in cm.
They come with either parallel port or USB control, but as I understand, they get direct commands via their comm port and if the host OS has timing issues, this might mess up the routing accuracy.
Which is why you can buy, on ebay china, arduino based PCBs with motor drivers as addons that implement GRBL control (buffering data on the controllers - or so I'd hope, LOL!).


Now what I want to do with it, and the questions.

My best compromise of size vs. price is the 3018 or 3020 one, I pretty much settled on that rough format.
I could mill PCBs for most of my devices' front panels.
And, given the stronger one, 3020, perhaps even actually mill fader slits, and rectangular openings for e.g. LCDs, into some 2mm aluminium sheet?

I started off wanting one of those 3018 cheaper things (between 160..300 EUR, depending on seller... I tried dealextreme and now cancelled, boy have they sunken low with their service, totally unable to understand basic english to solve problems... *sigh* I digress...),
then discovering the sturdier 3020.

Note: comments about "use OSHpark or Seeed studio, you fool!" are 100% off topic and *not* appreciated. I know what I want in this regard, for certain scenarios, which do not involve waiting 2 weeks for a supposed weekend circuit that I don't want to wild-wire solder without DRC, or paying insane money for even 2-layer PCBs of front panel size like 30x18 cm² - and then shipping for those...

Now, the 3018 seems pretty much ready-to-go and will do the most important of the jobs, i.e. milling PCB layouts. Time involved getting things up and running *is* relevant, as of course taking time out of my freetime for projects if the tool is it self too much of a project is a disadvantage.
*BUT* if the 3020 "full metal" thingy with, say 300W motor and 3 axes, could *realistically* do things like making aluminium panel cutouts for me without the direct-connection-no-bearings motor breaking after doing 10 panels (but still in hobby quantities), and perhaps as a bonus, mill some plastic parts (even if it's just voxel style "3D" with 3 axes ) this would be a really nice thing and would perhaps make me willing to invest the time & money to get all the extra stuff mentioned to improve their control hard- & software.
As for axes - so if I had 4 instead 3, does that mean I could do really smooth curves along one axis? (I don't think it's that important to me, but nice to know, should I encounter a good offer somewhere)

Also I wonder about accuracy of those both models against each other.
The 3018 has the base plate as one of the moving axes, whereas the 3020 moves the tool / motor spindle on both axes. I imagine this results in potentially more play vs. the flat base plate comfily sliding on 2 "threaded rods" ? With the 3018 or 1610 routers, I saw people doing traces for even QFP parts, hell I would be happy if it did SOIC well, at least I may not have to mess with UV-lighting hand-applied soldermask or nasty stuff like that with that format ;-) (I mean to aid soldering ICs. Spraying the whole board with cheap PCB insulation spray after assembly will probably solve the oxidation, and "I can make shorts easily"  problem).


So - I'd like to know:
Is my general perception of these things about right?
What can you say about the points I am not sure about?

[Magnum]

I have had a Stepcraft 420 first (https://www.stepcraft-systems.com/en/products/desktop-systems) and after that bought a Chinese 3040 which I modified.

It all depends on the precision you want. I was milling PCBs with the Stepcraft, but the backlash was quite big (approx. 0.1 - 0.2 mm, depending on how much you already milled with the machine). They claim 0.08mm, but that is not achievable with this machine (trapezoid screws), even after heavy tuning. So I bought the 3040 with ball screws, and backlash is < 0.02mm. But these Chinese machines don't have supported rails, so the overall precision goes down to approx. 0.1-0.2mm when milling. I modified mine with supported rails and linear guides, now I am below 0.05mm. So repeatability is quite good, but only when milling PCBs with very low forces on the machine (milling depth for PCBs around 0.1mm). If you want to mill aluminium, the forces go up and precision is around 0.1-0.2mm. Usually good enough for aluminium faceplates. Plastics are not a problem at all.

I wouldn't try the 3018, as it will be much weaker than a 3020. Find a 3020 with ball screws, otherwise you can only mill PCBs for through hole components IMHO. If you find one with supported rails, go for it. The spindle motor power is not that important, as you can only use a milling depth of 0.2-0.3mm for aluminium - it is more grinding than milling because these machines are not stiff enough. For real aluminium milling I use this machine:

https://www.paulimot.de/fraesmaschinen/mit-vario-antrieb/192/bohr/fraesmaschine-f205-v-mit-frequenzgesteuertem-deutschen-motor?c=8

No CNC, but I can mill a depth of 4mm with a 6mm flute in aluminium easily. I used this machine to modify my 3040 CNC. Weight is more than 100kg and made of steel.

For the connection to the PC I use the UCCNC software (https://cncdrive.com/UCCNC.html) and the UC100 USB motion controller (http://www.shop.cncdrive.com/index.php?productID=310). This way I don't have to worry about timing issues, and the software is really good (IMHO better than Mach3).

As spindle I use a Kress 1050 which goes up to 25.000 RPM. You'll need a high RPM for small flutes and drills. Don't buy one which is below 10.000 RPM.

I hope this help a bit.

[Magnum]

For PCBs I use a vacuum table with some rubber with holes or "pressed cardboard" (normally used for the back of cabinets) in between. Holds the PCB really good down and you can cut through. To mill double sided PCBs I have a camera installed for perfect alignment. As the rubber or cardboard is usually not 100% flat I use a software tool with UCCNC to measure the exact height before milling.

[Bryce]

Note: comments about "use OSHpark or Seeed studio, you fool!" are 100% off topic and *not* appreciated. I know what I want in this regard, for certain scenarios, which do not involve waiting 2 weeks for a supposed weekend circuit that I don't want to wild-wire solder without DRC, or paying insane money for even 2-layer PCBs of front panel size like 30x18 cm² - and then shipping for those...

Props to you for saying this. I am tired of people asking DIY PCB questions (not here specifically, in general on the net) and getting comments like you describe. They're 100% not helpful unless the person is talking about production and doesn't seem to know that PCB houses are a practical option.

That being said, my experience with isolation milling has been iffy. I did have success with it using my Chinese 6040 router (I made two boards for an EE class project in grad school, comprising a four-channel microvolts-to-volts active filter / amplifier to interface with thermopiles) but it took a lot of effort to get the boards flat. That's just a tremendous issue, these inexpensive routers do not have perfectly flat beds to begin with, and 100 microns of warp will ruin all but the crudest boards. So you basically need to surface a spoilboard first, and have some way to keep the board extremely flat, and start with high-quality PCB stock. Also, unless you have good dust collection, you shouldn't mill ordinary FR-4 stock because of the fiberglass dust hazard.

I've gone back to etching with ferric chloride for most needs. I still have the router to drill vias and throughholes, though, which is definitely nice.

Making PCBs in house is a huge pain, but there's no substitute for that turn-around time... at least not unless you have $1000s to blow on domestic quick turn-around PCB makers and overnight shipping.

[TinkeringSteve]

That being said, my experience with isolation milling has been iffy. I did have success with it using my Chinese 6040 router (I made two boards for an EE class project in grad school, comprising a four-channel microvolts-to-volts active filter / amplifier to interface with thermopiles) but it took a lot of effort to get the boards flat. That's just a tremendous issue, these inexpensive routers do not have perfectly flat beds to begin with, and 100 microns of warp will ruin all but the crudest boards. So you basically need to surface a spoilboard first, and have some way to keep the board extremely flat, and start with high-quality PCB stock.

Does not creating height maps for compensation alleviate that, like so?


I don't know the hardware of this guy, but he mills for QFP parts:

Also, unless you have good dust collection, you shouldn't mill ordinary FR-4 stock because of the fiberglass dust hazard.

Oh! I sure don't want to breathe that.
I planned on spraying a board with "cutting oil" beforehand, would that help somewhat? (make dust stick)
And at some point, also because of noise reduction, I'd like to build some case out of a frame of wood, and then maybe some plexiglass, with a lid on top and foamy stuff where lid and lower part of the case
meet. So if the mill worked in there, and when it's done, I open it and manually go everywhere with the vacuum cleaner hose, would that work?

I've gone back to etching with ferric chloride for most needs.

That makes quite crude etchings and underetches traces, no? I still have some Na2S2O8, but it's harder to buy these days. But I don't want to bother with stuff like toner transfer or other not so great but nontheless immensely messy methods, including the UV lighting and then trating with chemicals and all that.
Even more crude layouts done with CNC seems nicer than that.

I still have the router to drill vias and throughholes, though, which is definitely nice.

Yes, not having to do drilling would be a nice plus.

Making PCBs in house is a huge pain, but there's no substitute for that turn-around time... at least not unless you have $1000s to blow on domestic quick turn-around PCB makers and overnight shipping.

Exactly.

[TinkeringSteve]

Btw, maybe someone can say something about this:
The 3020 / 6040 apparently have no limit switches? (Endlagenschalter, for the germans).
That sounds kinda insane.

[Magnum]

Mine didn't have limit switches either. But I installed them myself, there were 4 unused digital channels on the controller PCB (I am using the fourth for probing).

[TinkeringSteve]

Mine didn't have limit switches either. But I installed them myself, there were 4 unused digital channels on the controller PCB (I am using the fourth for probing).

Hmm, and your software, whatever you are using, supports that, just adding some "free channels"?
You will notice, I don't have a good idea yet of how this all works together exactly, and what the options are there. Btw, does your "oldschool" 3020/6040 variant support auto-leveling and stuff?

I guess what would be immensely helpful is, if there was some sort of system diagram of a whole setup. All hardware, software (& firmware), what does what, what can be replaced with other options...
Has anyone anywhere done such a thing? :-D

[Magnum]

I am using UCCNC as software, it is approx. the same like Mach3. There are more plugins available for Mach 3, but I like UCCNC better. To connect to the PC I use their UC100 USB adapter. See www.cncdrive.com

So the UCCNC software talks to the UC100 USB adapter. This adapter (motion controller) is plugged into the parallel port of the CNC control box. This parallel port is on the breakout board inside the control box. All the servo drives are connected to this breakout board, and in my case I have 4 unused pins on this board for the limit switches available. The servo drives are then connected to the servos on the machine.

In my case I have a speed controller for the spindle built in, too. It also connects to the breakout board.

You can use such a CNC control box directly with the parallel port of a PC (without the UC100 USB motion controller in between), but in that case the PC timing is critical (e.g. if you want to mill an arc). With the UC100 USB motion controller, all commands are buffered in this controller and then sent to the parallel port.

The setup of the software for the ports is easy. Usually the settings for the servo drives are supplied with the machine. If you have more pins available on the breakout board, you can find the pin number with trial and error. The UCCNC software has a diagnose screen, and if you connect a pin to ground you should see it. Just make sure that it is a input pin (connect a multimeter and it should read high, when you look at the PCB there should be a pullup resistor).

The UCCNC software supports the use of a camera, but there is other software available too. In the picture I put a "meter" on the table, the dashes are 1mm apart.

A pendant can be used with the software, too.

[Magnum]

More pics

[Magnum]

The last

[Magnum]

Btw, does your "oldschool" 3020/6040 variant support auto-leveling and stuff?

Auto probing of the used mill is supported by UCCNC (I use the fourth additional channel for that). Auto leveling is done by modifying the G-code, so every control software and machine will handle it (as long as it has a probing pin). For UCCNC a plug in is available, so before you start milling it will automatically measure the exact height of the surface, modifies the the G-code and you can start.

[TinkeringSteve]

Ah, thanks for the info and all the pics!
The white plastic things look interesting. So I guess when milling out pieces like that, those little leftover holding "threads" along the edges are necessary for the stability of the remaining base material while milling out the remaining parts?

What's the air pressure(?) stuff for?

Arches, can you even really mill them with only 3 axes?
(edit: oh well, I guess in the plane you can, I was thinking of more complicated ones ^^)

The software packages you mention, they are all commercial? (prices roughly?)
I remember some people talking about using some open source stuff, but I can't remember the YT videos, I watched too many in a chaotic manner, damn side bar

What I am wondering about is, how hard it would be to write extensions or modifications yourself, of program functionality. Or maybe that's not even necessary, I guess you'd just need some script that spits out the corresponding G-code to make the machine do something you want, right?

For instance - could you use the machine also to plot ink (like white 'edding') onto a surface, e.g. to label a front panel's controls? (asking also from a practical, mechanical perspective, I have zero experience with that kind of thing)

[Magnum]

Ah, thanks for the info and all the pics!
The white plastic things look interesting. So I guess when milling out pieces like that, those little leftover holding "threads" along the edges are necessary for the stability of the remaining base material while milling out the remaining parts?

You mean in pic 219? It is a aluminium part, and the leftovers are to hold the piece in place. You can specify it in the CAM software (I use Fusion 360, it has a post processor for UCCNC)

What's the air pressure(?) stuff for?

It is vacuum for the vacuum table as you can see in pic 216 and 219. The vacuum holds the material in place, it is better than using double sided tape.

Archs, can you even really mill them with only 3 axes?

Sorry, I meant arcs.

The software packages you mention, they are all commercial? (prices roughly?)
I remember some people talking about using some open source stuff, but I can't remember the YT videos, I watched too many in a chaotic manner, damn side bar

UCCNC is commercial, I think it costs around EUR 150 with the UC-100 motion controller. You can use Mach 3, too, that costs IMHO around the same. To mill PCBs I use Eagle and a free G-Code converter. For other constructions (e.g. Tool Box inlays out of foam) I use Fusion 360. It is free for one year and can be extended for free another year.

What I am wondering about is, how hard it would be to write extensions or modifications yourself, of program functionality. Or maybe that's not even necessary, I guess you'd just need some script that spits out the corresponding G-code to make the machine do something you want, right?

For instance - could you use the machine also to plot ink (like white 'edding') onto a surface, e.g. to label a front panel's controls? (asking also from a practical, mechanical perspective, I have zero experience with that kind of thing)

Mach3 and UCCNC use a script where you can program things like probing. But you don't need to program anything to use the CNC for a plotter. Just a software which exports G-Code

[TinkeringSteve]

There is one not unimportant aspect I neglected so far:

How loud is this thing really? (given the 300 W spindle)
Assuming I build a complete enclosure for it, would it even be feasible to use if you don't have a garage or something? There is reasonable sound isolation from the neighbors, not perfect, but not as bad as in early 20th century houses. E.g. I only hear them vacuuming when they are above me, because it's directly on the floor, never heard it from the sides.
I have heard an industrial CNC milling plastic, but that thing was almost as big as my bathroom I think

[Magnum]

I don't have a 300W spindle. The Kress makes some noise, but with a enclosure it is IMHO no problem. Or you can use a water cooled spindle, that isn't that noisy either.

[TinkeringSteve]

Hmmm, cooling you say.

https://www.ebay.de/itm/4-3-Achse-CNC-Fr%C3%A4se-Fr%C3%A4smaschine-400W-800W-1500W-Graviermaschine-6040-3040-3020/253419641752

I don't see any cooling on the standard spindle motor that comes with this (300W option).
Would you say that's too crappy to be useful?

My plan so far is to stop fricking juggling with a million options now and actually buy something, e.g. that thing linked above as a first start. Get it running, maybe even without additions like new controller boards. Maybe I even try LinuxCNC with an old PC that runs only that, nothing else.
And then with coming months (and new salaries ;-)) buy some additional stuff that improves things, as needed.
(though I wonder, they have USB option which would seem easier to get things running for now, but your linked site apparently has only LPT parallel port g-code buffering box, not USB?)

Bad idea?

[Magnum]

A fan makes noise. So if you use a water cooled spindle it will be less noisy. I don't know if the 300W spindle has a fan and how noisy it is.
For PCBs you won't need much power, but a high RPM (20.000 should be fine).

With the USB version you should have a motion controller already built in. I went with the parallel port as I already had the USB-> parallel motion controller and knew that it works really good. IMHO UCCNC needs a motion controller from CNCdrive, otherwise it won't run.

If you buy one of the cheap Chinese CNCs take one with ball screws, that gives a much better repeatability. And you will have to swap out the T-slot plate, as the original one is crap.
https://www.vakuumtisch.de/Cast-aluminum-T-slot-plates-Tiny

[Kjelt]

Would you buy a brand new chinese car for $2500 and drive your family with it?
These machines are crap, useless for any precision pcb jobs, useless for aluminium milling, I don't understand why anyone buys this junk.
If you want pcb millimg you need a very small ultra precise cnc machine, decent ones starting at $4000.
If you want to mill aluminium you need linear guides, good steppers pref closed loop, a hard metal good brand ballscrew 16mm, good mill with rpm adjustable, etc. etc.

I bought a German cnc machine 10 years ago for $4500 and that is also meeehh quality, no linear guides only round guides unsupported, small 10mm ballscrew, no pcb able, and aluminium only thin front plates.
The manufacturer promises all these great numbers but in practice it is not up to it.

I joined a cnc forum, read all I could, talked and visited people that have been doing this for tens of years and now building my own cnc machine. Parts alone costs over $7000.
So better be warned than disappointed, there are no Harry Potters in China, they can sell you stuff 50% cheaper than in the US or EU but don't be surprised if the quality is also less than half.

[TinkeringSteve]

Would you buy a brand new chinese car for $2500 and drive your family with it?

No.
Boy! Am I glad that I don't need to drive my family nor cat with the "CNC 3020 ShenZen edition"!!!
Very bad analogy. Apparently, a more appropriate one would lack the oomph for the argument?

These machines are crap, useless for any precision pcb jobs, useless for aluminium milling, I don't understand why anyone buys this junk.

Plenty of youtube evidence seems to disagree with that sweeping generalization.
I have seen amazing things being done with that "crap".
(Even the 3018, held together by plastic parts, seems to have a lot of uses, enjoyed by many. Digest that one.)

I am not expecting to be doing all of the stuff that people are doing with "regular" CNCs.
There *can* be a reduced set of use cases with a product compared to the idea that people have in their heads when thinking of a certain class of product,
that can still be useful.
People who make such broad dismissive comments usually make the error of assuming everyone wants to do everything that is associated with "CNC mill" (or router, in this case).

I've heard the same with chinese oscilloscopes.
Yet my Rigol at home beats the hell out of standard Tek DSOs I've had to use at work, while shooting off to the moon,  circling around 3 times, and coming back. For less than 1/2 the price.
You can philosophize all day long about how the magicians over there are doing that.

Perhaps, a somewhat less sloppy look at those things would be adequate?

I do appreciate the warning of spending money and being disappointed.
Spending several k on something I'm rarely going to use would be immensely dumb, though.
And it's not going to happen, period.

See. There comes the next relaxation of requirements. This is not for churning out parts to sell 5 days / week, year after year.
On some weekends, I will be doing stuff...
So equipment that is built for pro workshop use, causing a higher price because of that very requirement, would be the wrong choice of tool for my situation. Because I do not have that requirement.

You also don't put precision measurement amplifier circuits into a consumer mp3 player audio path and expect to sell the thing. Wrong design choice / wrong market.

[Magnum]

Would you buy a brand new chinese car for $2500 and drive your family with it?
These machines are crap, useless for any precision pcb jobs, useless for aluminium milling, I don't understand why anyone buys this junk.
If you want pcb millimg you need a very small ultra precise cnc machine, decent ones starting at $4000.
If you want to mill aluminium you need linear guides, good steppers pref closed loop, a hard metal good brand ballscrew 16mm, good mill with rpm adjustable, etc. etc.

I bought a German cnc machine 10 years ago for $4500 and that is also meeehh quality, no linear guides only round guides unsupported, small 10mm ballscrew, no pcb able, and aluminium only thin front plates.
The manufacturer promises all these great numbers but in practice it is not up to it.

I joined a cnc forum, read all I could, talked and visited people that have been doing this for tens of years and now building my own cnc machine. Parts alone costs over $7000.
So better be warned than disappointed, there are no Harry Potters in China, they can sell you stuff 50% cheaper than in the US or EU but don't be surprised if the quality is also less than half.

Kjelt, it is not as bad as you think. Milling aluminium is not what these machines are built for, I have another machine for that (used it to improve my Chinese machine). But if you want to mill some aluminium panel cutouts for example you can do it, but only with 0,2-0,3mm milling depth. As I mentioned in another post before it is more grinding than milling, but doable for hobby use.

The forces for milling PCBs are not very high, I mill them with approx. 0.1mm depth. The ball screws in my Chinese machine have a repeatability of approx. 0.01mm, that is more than needed for PCBs. You also don't need closed loop steppers, the ones they put in are strong enough that they don't loose steps. My system runs with only 24V and so the steppers run slower of course, I have them set up for 2800mm/min. But changing the electronic later is not a problem.
I put linear guides and supported rails in my machine, so precision is fine. If you only have unsupported rails you will get problems with the z-axis, but that can be solved with software (see above). Even with a very good machine you should use the software compensation, as the PCBs are not always perfectly flat.

But of course this is a machine for hobby use. If you want to spent EUR 7.000, have a look at these machines: All linear guides, ball screws and well built. They are made of aluminium, so there are limitations, too, but IMHO stronger than others in that price region. The one in the link weighs 95kg and with electronics you'll have to pay around EUR 4.000:
https://www.sorotec.de/shop/Portalfr-se-ALU-Line-0605-Bausatz.html
Milling aluminium:

[TinkeringSteve]

By the way,

how much of an asset is a 4-axis model really?
From my newbie understanding of what it might be good for, I don't really need it that badly...
Yet the ebay offers for the chinese 3020 that do have ball screws (starts at 560 W), do have 4 axes. I don't know why, it's the same for every seller I looked at so far...
Could this machine actually drill holes from 90° angle? The X motor or whatever it is and the mechanics would need to be strong, eh?

I don't really feel like paying extra for a 4th axis as I don't currently see a good use, but those sellers do have the advantage vs. ordering from someone directly from china, that they are somewhat more bound by warranty law and they ship from - and you could ship back to - a German address :-)

Or are there other good places than ebay to get those from?

[Kjelt]

As long as you know what you're getting into.
I have friends very disappointed with their $500 + €200 tax 3d printer from China, repeatability errors etc. wishing they spent the extra $1200 for an european one with guarantee and support.
Saw posts of CNC machines that couldn't even do 3mm of wood.

My self built CNC has some parts from China as well , but very miticulously selected parts that are just 20% cheaper there or even can't be bought.
Even than I get burnt. I got Leadshine closed loop easy servo's, 4 of them were exactly the same, the 5th pair was deviation in color and stickers etc. They were fakes.
These fakes last about 10% of the original ones and then let the magic smoke escape.
You really have to know what you are getting, as long as that is the case I shut up 
But remember the costs don't stop with the machine. Good endmills costs $15 a piece and esp in the starting process you'll break a few.

[Kjelt]

But of course this is a machine for hobby use. If you want to spent EUR 7.000, have a look at these machines: All linear guides, ball screws and well built. They are made of aluminium, so there are limitations, too, but IMHO stronger than others in that price region. The one in the link weighs 95kg and with electronics you'll have to pay around EUR 4.000:

If I am not mistaken that is just the mechanics, no motors, no electronics, no software. I know such machines also from Haas very good and well built but at the end costing around EUR 9000 easy.
Mine is designed by the forum members, really top notch, if it would have been all built by a company it would easy go >EUR15000.- even more. But it takes time to built the thing, but then you know what you have built how it works and how to fix it 
Building a CNC makes you understand everything you need to know.

[Kjelt]

By the way,
how much of an asset is a 4-axis model really?

From the people on the cnc forum that have one, most used it a couple of times then never used it anymore.
It ofcourse depends on what you will be doing , 4th axis is for 3D CNC'ing like sculptures.
AFAIK 2,5D which can be done with 3 axis is around 95% of all jobs worldwide. So if money is an object I would wait till you really need one and then you can always built something yourself, as long as the electronics are prepared for the 4th axis.

[Koen]

Have you finished your build Kjelt ?

[Kjelt]

Have you finished your build Kjelt ?

No thats going to take some more time, I got ill (flue) for the last two weeks, still in the process of getting better.
But almost all the parts are now in tha house, it is now making time to assemble and adjusting.
I am currently placing the electronics in the cabinet, since the cabinet is steel drilling and cleaning the holes for the connectors is a PITA.

[TinkeringSteve]

Kjelt:

Hey, I'm not asking you to "shut up" ;-)
I am about as mechanical as your average software dev. I am glad of being warned here about some things.
After watching dozens of youtube videos and what people were able to do with those chinese things, reading them being called "useless" seemed unduly harsh.

Guess I have read (more than) enough of the ramblings of experienced, older pro EEs on forums, telling the kiddies who try to get into their new hobby to either spend $ $ $ $ on their gear - or die.

Slightly bemused after watching the recent discussions on how many 100 bucks to spend on a device that heats a metal rod with the mass of a penny (soldering iron with heating *inside* the tip?),
I continue to work with the 70 € hobby-Weller, with the tip I bought 2011, which doesn't look like I need to replace it anytime soon.
For some weird reason, it seems to do the job. So someone doing repair work every day may have a different experience, but I'm not that someone.
My whole setup here probably costs less than 1500€. Including the DIY workbench, lol.
Bought used, older lab PSUs, granted.

I'm not sure I'd dare to buy a used "real" CNC mill, though. Not to mention I couldn't buy a big one that is going to displease the neighbors more, I also probably couldn't tell if there's something slightly wrong immediately, and there's no warranty...

And what you spent on your machine is almost what my Hyundai car cost *new*, incl. climate control! ;-)
A more feasible option than that would be to have everything made by others, but that quickly adds up also to a high cost, with another set of drawbacks.
So I will try with the cheap stuff.
Should I learn that it really does not perform to my (not hugely high) expectations, and I do not manage to break them, I can still sell them and go other routes.

You know. To be able to get prototype  front panels accurately drilled, even if it was just plastic, not aluminium, would be quite awesome. As one of many examples of the more "light uses" I'd have for that.
This would beat the hell out of me sitting at the desk with the battery drill, going hole by hole, with roughly 1mm and 5° accuracy (no I don't have a proper drill, for critical stuff I need to visit my father, the distance is inconvenient )

[TinkeringSteve]

"Supported rails" were mentioned.

Could you retrofit that? Is it difficult / expensive?

[Kjelt]

You're correct, every application and budget has its valid domain.
I did react from my own experience having bought a rather decent 4,5k$ german cnc that promised all kinds of high accuracy specs that in the end was unable to deliver and ending up with lots of frustration has coloured my experience and response.
That machine is highly featured on YT and some people make incredible things with them, but overall it is just not what I really would like, namely a machine where the operator is the weakest link 

The same with soldering irons, if it can not transfer the heat quickly enough in the solder joint you will fry off the copper traces from the pcb.
Also the 3D printer that makes a vase which takes 4 hours, due to a small deviation it results in the tower of Pisa instead of a nice vase.
In that case those companies that let you use their (better) equipment, the makerfairs etc are really a good alternative, although only found in larger cities.

So hope you will enjoy your machine and that you are not getting frustrated by it as I did with my previous machine.

[Kjelt]

"Supported rails" were mentioned.

Could you retrofit that? Is it difficult / expensive?

You have round guidance bars that are only supported on the ends, those are the worst since they bent but for short distances (small machines) they are okish.
You have the same round bars but at the bottom they are connected to a metal bar, these are better since they have a support under the entire round bar, so less bending.
These both do have a drawback being "play" on the construction, you can wiggle them they are not very sturdy.
The best are linear rail guideways, these are hardened steel rods in a special shape where special matching block carriages fit onto. These have almost no play and are made to last also with high mechanical stress.

Can you retrofit? In theory yes. In practice all the mechanical distances esp in vertical direction should match exactly. With tolerances of <0,1 mm that can be tricky.

[Kjelt]

Is it expensive?
Depends on the quality.
You can buy chinese linear guiderails with carriages for <$100 for a meter.
If you buy HiWin Taiwanese brand linear guiderails you pay $200 for a meter with two carriages.
If you buy Rexroth you pay $1000 a meter and two carriages.

Now these three are not the same, but the Chinese you need luck for a decent manufacturer, the HWin are very good and good enough for my machine, the Rexroth is for the Dubai people 

[flolic]

"Supported rails" were mentioned.

Could you retrofit that? Is it difficult / expensive?

It is possible. But there is no sense buying something that you already know is not good enough, than investing more money to make it better. You know what? It will be better, but not good enough.
Those machines are good enough to do cuts in plastic and light cuts in aluminium. But ask yourself, are you buying CNC machine only for cutting holes in front panels? If yes, you'll be ok with it.
But soon you will want to machine some heavier part, like custom Al housing, and will find out that machine is simply not rigid enough for that job.

The best way into CNC world is to build your own machine. But that can be easy or hard way, depending on your knowledge and possibilities. I have built my own machine few years ago and it cost me
around 2000 to 2500 EUR to the point I can fully use it (it's not 100% finished). Critical parts are sourced from ebay, like (used) NSK linear rails, Kuroda grounded ballscrews, stepper motors and drivers,
USB motion controller, water cooled 2.2kW spindle... Other mechanical parts (T-slot profiles, plates, fasteners...) are sourced locally or within EU. Machine working envelope is 300x300x150mm.

I can cut in aluminium just as easy as in plastic with final part tolerances of 0.01mm. And machining speed can be insane

Check this video:

[flolic]

And finished parts:

[TinkeringSteve]

flolic:

As for retrofitting - yeah, I was expecting that it would probably not be worth it.
But better ask than just assume

Sure, being able to do that (like your custom alu case) would be nice.
But it's not what I started out with as requirements, and I should slowly but surely put a stop to the scope creep that has already infected this endeavor

The more of an own project the CNC becomes, the more useless it is to me - because it takes time off the very reason why I want it in the first place.
I do not plan to start what I actually want to do only in 3 years or so...

I have no mechanical workshop. I will not buy some 1000s worth of tools anytime soon. And no room to have an actual work shop either.
For those who haven't guessed by now - I do not have a house, I live in an appartment with 2 rooms  (not counting the bathroom).
So forget about any monstrous "real CNC". It will have to be the 3020/40 or so. (plus enclosure I build).

I will note things mentioned here about better, somewhat costlier options, though.
My father may actually be interested. He has more room than I do.
But there's the (not so) little problem that he doesn't understand English, so most of the software (or information about hardware modding) will be difficult to use for him. I guess it's easier if he has roughly the same gear I have and I can always help him with stuff.

[ironcurtain]

I don't want to hijack the thread but it's interesting. I have been looking into small CNCs that can work with 3mm aluminum and smaller gauge soft steel for front panels and such... tired of drilling my hand though it works and I have a vertical drill press. So far nothing clear as to what is available that can work with plastic/ABS/PP, aluminum and soft steel at a small scale. I got puff already from Chinese industrial rigs when I saw the IR reflow ovens they sell cheaply...

[TinkeringSteve]

As for Air vs. Water cooling:

So this means for air cooling, high pressured air is blown onto the spot where the routing is taking place, like it would be with water?

For what materials is that necessary?
Would just spraying the surface with cutting oil help much?

[Kjelt]

As for Air vs. Water cooling:

So this means for air cooling, high pressured air is blown onto the spot where the routing is taking place, like it would be with water?

For what materials is that necessary?
Would just spraying the surface with cutting oil help much?

AFAIK air only is solely used in milling plasticks/acryl/polycarbonate that kind of material.
For light aluminium you usually use a mist being generated by compressed air blowing small amounts of water mixed with some additive, aka minimalschmierung.
For steel you use a flood what looks like a waterfall.

[TinkeringSteve]

But you could use the water thing for alu? It looks like that's what the somewhat more expensive (for China kit ) have. If that's less loud than air pump, as was hinted at earlier in the thread, I would prefer it.

I have seen some people just spray "cutting oil" onto a PCB before milling, no other means of lowering temperature was used.

Btw, are there tools for, and would it be feasible, to use the router also for polishing a piece of wood? Like, before you apply linseed oil treatment to darken wood, for instance, it needs to be reasonably finely polished. Heh, I guess to polish the edges at 45°, 5 axes would be nice, but that'd be overkill :-) Hmm, or are there maybe tools that are angled 45° themselves...

(please help me find more types of work I could push onto the machine, to help me justify to myself  getting the bigger model, ok? LOL! And again, it may take hours, if I'm not doing it by hand, I don't care)

[Kjelt]

You mean a waterflood for alu?
Yes could be done but you need some form of tray to collect the water, filter it and pump back, recycle.
I never saw that on affordable machines only at the pro cnc stations >$60k but I haven't seen everything of course, Perhaps someone working in cnc could advise.

Polishing, that is a different ballgame AFAIK, milling is high speed small surfaces, polishing is low speed big surfaces. Never saw it check youtube if you see something like that. Polishing needs a steady downforce, I would prefer to do it by hand or polishing machine by hand, more control.

More types of work, you could put a pencil in it and make drawings, put a rotating cutting tool in it and cut plastick stickers, perhaps some kind of laser for etching   

[langwadt]

Is it expensive?
Depends on the quality.
You can buy chinese linear guiderails with carriages for <$100 for a meter.
If you buy HiWin Taiwanese brand linear guiderails you pay $200 for a meter with two carriages.
If you buy Rexroth you pay $1000 a meter and two carriages.

Now these three are not the same, but the Chinese you need luck for a decent manufacturer, the HWin are very good and good enough for my machine, the Rexroth is for the Dubai people 

you can get mgn12 much cheaper, I think since they begun to use them in some 3D printers, e.g.

https://www.robotdigg.com/product/493/GCr15-MGN12-1H-500,-MGN12-1H-600-or-MGN12-1H-1000-Linear-Rail-and-Carriage

$54 for 3*500mm with carriages

[TinkeringSteve]

Hehe, "more types of work", it wasn't fully meant serious, I already have some ideas

About the spindle:

I found out that the china spindles, if you apply enough sideways force, e.g. 18N, can have play of up to 0.2mm, as there apparently is some rubber dampening that holds things inside.
I guess for PCBs, the effect would maybe not there, as there isn't much sideways force(?).
For milling plastic, maybe more so. Then again, I perhaps won't need super fine accuracy for plastic parts.

But just playing this in my mind: Say I was to buy the Kress spindle, which is said to have max 0.015 mm play: It apparently only  has a few fixed speed settings which cannot be controlled via software.
While the china box does not come ready-to-go in that regard, I saw someone open the controller box - and their PCB is prepared for that, you just need to solder some additional parts and wires, and snap, you have PWM control via software.

In what scenarios would it be advantageous for the milling software to control the spindle speed?

(P.S. as I saw some DIYers do buy such china spindles, so *if* I was to get the Kress, I guess I could sell the china spindle to get some money back. Just would suck if it later turned out something not immediately obvious is wrong with the kit and I need to return it Damn it, there's always something...)

[Kjelt]

I used the Mk1 Kress for many years, it is ok for starter. Disadvantage was the incredible noise and that the rpm started at 10k-30k while esp for wood and plastick you like lower speeds like 3k or the wood can burn or you have to increase the feed.
Current Kress can be bought with 5k start rpm which is better.

Most persons on the cncforum buy a chinese spindle with vfd, same price but way better than the Kress, lower noise, lower runout.
But I hear the quality does vary so you have to be lucky.
Second is the watercooling in a few years leads to leakages in the o-rings, rusting the bearings.
So I would advise an aircooled spindle but this has disadvantage of overheating at lower rpm since the fan is mounted on the axis. So if you go to lower rpm often you need to mount a high air force fan ontop of the spindle and ofcourse extra dustcover since it attracts huge amounts of dust.

I also heard of EU "companies" that buy the chinese spindles and then modify them with good western bearings even ceramic bearings and reduce the play. But quite costly almost doubles the price.

If you go china spindle you need to know just as with any other pro spindle that you can not run the spindle at 24k rpm from the start.
You first need to warm it up, starting at low rpm increasing slowly in a few minutes till 20krpm then you are set to go. Otherwise the bearings will not appreciate it.

[flolic]

I have water cooled 2.2kW chinese spindle on my machine, but currently I am running it dry. For majority of jobs in alu it only needs few hundred watts of power, so 2.2kW spindle is really an overkill.
But that capacity helps when you reduce the speed, because those spindles have low torque. I am running it from my LS industries (LG) vector drive VFD. It is running warm to the touch after a hour of use,
so no problem with (lack of) cooling. Spindle is very quiet, on pair with the steppers. What's really making a noise is end mill cutting action.

[TinkeringSteve]

Ah! Some important newbie tips, thanks guys, very useful, e.g. letting it run warm before high RPM, maybe there's a chance now I won't destroy my gear in a month *g*

Rusty bearings? Lol. Damn. Could you pump oil through it instead water? :-D Probably dissolves their O-rings.
But I guess I might try air cooled.
I have found ebay sellers who sell apparently better chinese spindles with "4 bearings" and claimed < 0.01 mm runout. They are called "ER11". (or is that a size? lol. Chinese things not always have product names...)

They also come with "VFD inverter" control box, I guess if I buy a kit that already has VFD for the crappier motors, I don't need to buy that also, are those usually compatible so I can use the kit's own one?

EDIT:
Btw, what kind of tasks would you need low RPM for, so that air cooling may be a problem (unmodded)?

[langwadt]

Ah! Some important newbie tips, thanks guys, very useful, e.g. letting it run warm before high RPM, maybe there's a chance now I won't destroy my gear in a month *g*

Rusty bearings? Lol. Damn. Could you pump oil through it instead water? :-D Probably dissolves their O-rings.
But I guess I might try air cooled.
I have found ebay sellers who sell apparently better chinese spindles with "4 bearings" and claimed < 0.01 mm runout. They are called "ER11". (or is that a size? lol. Chinese things not always have product names...)

They also come with "VFD inverter" control box, I guess if I buy a kit that already has VFD for the crappier motors, I don't need to buy that also, are those usually compatible so I can use the kit's own one?

EDIT:
Btw, what kind of tasks would you need low RPM for, so that air cooling may be a problem (unmodded)?

ER11 is the size of the the collet chuck

[Kjelt]

Yes ER11 can handle shafts upto 8mm diameter (sorotec.de has a 8mm collet) so that is the limit.

Slow rpm jobs : wood if it burns at higher rpm but you can increase the feedrate also.
Plasticks, they are tricky, if the  milling cutter runs hot the plastick melts sticks to the cutting surface and bam your cutter breaks off. The same can happen with aluminium if it sticks to the cutter that is why for alu you want some kind of cooling spray with some additive and for plastick forced air to blow away chips and keep the cutter cool.

The chinese sets with vfd are nice esp for their price. The vfd takes some time to program and understand, i have to start with that also soon.

[TinkeringSteve]

One thing I don't understand yet (at least ;-) ;-) )

Earlier in the thread, Magnum mentioned getting a better "base plate", linking to one at vakuumtisch.de.
With lots of holes. Because, it's actually a vacuum table, i.e. a table that holds something on it with vacuum?
But if you need some sacrifice plate anyway, under your actual material (at least if you need to drill / route through it), then you could just clamp it on the base plate/table (whatever that's really called) and be done?
Why vacuum?

I guess the recommendation was maybe not mainly due to the vacuum, but because it looks way more massive than the one that comes with the kit, right? That one looks like "more air, less metal"
But if I put some MDF (or plastic?) sacrificing plate on the table, won't that give the whole setup more stability than a flimsy "alu profile" table alone?

EDIT:
Oh and by the way, I saw the CNC kit comes also with a Lathe - an extra stepper and a thing to hold tools that are then rotated.
Does someone know what that is *practically* good for, in this china CNC edition?
One thing would be just for positioning something round to then drill holes into or cut something out.
But could you actually do lathe work with that, i.e. get a cutting tool for the Z-axis that, say, cuts away the 90° edge of a cylindrical piece of soft alu or plastic to 45° and stuff like it?

EDIT #2:
Hah! If the "lathe" motor is too weak, why not do it the other way around - fixed blade, rotating workpiece?
Just that you probably cannot use a very long cylinder material, as the forces on the spindle would get too high... But funny idea ^^

[Kjelt]

Normally you mount a t nut alu plate as a first base.
Then you can:
Or place mdf plate on it and mill it level with your machine
Or place 4mm or so PVC strips with thin two sided sticky tape and mill it level with your machine.
     Place and mount mdf on the pvc

After that you can put a vacuumplate on it, mostly used for items that can not be easily clamped down or need to be very flush with the machine such as pcbs, thin plasticks.

You need a high volume vacuumpump for it not a deep vacuuum low volume since each leak will blow out the vacuum
If you need to cut through the object then place Between the vacuumplate and the object some special rubber sheet that passes the vacuum and to preserve the vacuum plate.

[TinkeringSteve]

Hey,

so I ordered one with the ball screws, it came with water cooled, but I bought an additional air cooled 800W spindle with 4 ball bearings.
I need to assemble it now ;-) (and first, build a damn table that's big enough )

Seeing in a YT assembly vid that the side motors are already on there, although with some protection material around them, I can imagine that if the transport service ignored the "this side UP" arrows, there could have been angular strain on those...

So:
After assembly, what initial tests should I do to make sure everything is allright, including accuracy, nothing bent or whatever?


Btw, I ordered a beginner CNC book now, so I don't need to bother you all with more n00b questions
Just that those books don't talk about specifics of the china cncXXYYt models. (there is one book that's more a stepcraft manual than generic cnc router book, that's not the one I ordered...)

For now, I ordered some cheap mechanical switches which will arrive soon, which should work for limit switches for now, but I don't want to drill threaded holes yet to mount anything until I know I don't need to return it... maybe wire straps or something will do...
I also found cheap (< 2 € !) chinese inductive sensors (shipping 2 months ) which trigger ~ at 4mm. Sounds nicer (no bounce?) and more long living - good idea, or do they have their own problems?

Some ppl on YT said they don't use limit switches for Z axis, they use soft limits. Really? Why? The motor is not homed then?

Also, from what I gathered, the controller expects normally-open switches for limit switches.
I do not like that. Broken cable -> crash. How about inverting it 1) at the sensor, and 2) again in the controller box, to have normally-closed logic? Makes sense?

Anyway, thanks a lot to you few guys who have been doing all the answering here!
Is there a CNC forum where there are people with specific china CNC router experience, and where they don't chase you away if you mention you have a china one? (i.e., not like going to HAM radio meeting and shouting "BAOFENG!"...)

[Kjelt]

So:
After assembly, what initial tests should I do to make sure everything is allright, including accuracy, nothing bent or whatever?

Manually feel if the guides move smoothly, check the axis visually for bends.
Then place a Clock gauge against the axis turn them and see if they have acceptable run.
Then check motor parameters, move everything in the middle so you don't run to the limits.
Place paper or carton on the machine bed.
Place a pencil or something else in the z axis and lower it till it marks the paper.
Let the mchine run a specific length on the x axis for instance 50mm and check with measurement.
Repeat for Y.
Then check the alignment between x and Y by making a two point opposite corner rectangle marks where x and y are choosen so you can easily measure the corners distance as with Pythagoras law.
 
Those kind of things.

also found cheap (< 2 € !) chinese inductive sensors (shipping 2 months ) which trigger ~ at 4mm. Sounds nicer (no bounce?) and more long living - good idea, or do they have their own problems?

They detect iron better than aluminium so you might need to add a small iron piece.
The ones with a flat sensor are nice, the one where it is sticking out could be more sensitive for surroundings. But these are often used as proxys (proximity sensors).

Some ppl on YT said they don't use limit switches for Z axis, they use soft limits. Really? Why? The motor is not homed then?

Limit is not home switches 
If you have closed loop steppers and good soft limits if you gomoutside and the motor encounters a physical limit it shuts down with a driver error since the servo has a stepencoder on its axis.

[Magnum]

Get something like this
https://www.paulimot.de/messen-und-pruefen/messuhren/686/fuehlhebelmessgeraet-feintaster-0-bis-0-8-mm

and / or this
https://www.paulimot.de/messen-und-pruefen/messuhren/461/messuhr-0-bis-10-mm-fuer-messstativ?c=88

and this

https://www.paulimot.de/messen-und-pruefen/flachwinkel/384/flachwinkel-900-200-x-130-mm-rostfrei-inox?c=84

That makes it easy to check the machine.
You might need to manufacture something to fix it to the machine.

[TinkeringSteve]

"Limit is not home switches "

Well. Where I encountered limit & homing switches before, namely in an automation to assemble some parts we built at my old employer's place, one of the limit switches of each linear motor was also used for homing, so in my mind it was almost the same (no it was not I who designed the overall setup, it was a mechatronics guy).

Magnum:
Ah, thanks. Hm, what's the difference between the first two? DE wiki says it's especially good to check runout, I don't get why, though. Apparently you can make measurement errors also, if measuring at an angle. I bought something like the first second for now.

[Magnum]

IMHO the first one is better for checking the machine. It doesn't need much force for the measurement and the measurement point is quite small. Also good to check runout, as you mentioned. But the measurement range is not as big as the second one.

[Kjelt]

Well to clarify the difference:
A hard limit switch is a last resort safety mechanism to protect the machine for damage, you need two per axis and it should be hardware based (safety)
A home sensor is the location where the machines 0 point is located, this can be arbitrary placed but usually it is a for a human logic location in the left corner. You need one per axis and it is software based.

[TinkeringSteve]

Btw, that "armored vehicle chain" with the cables inside to move alongside the whole thing: it's also plastic of course.
Would it make sense to apply a drop of silicon oil to every joint, or has those plastic parts rubbing against each other not yet resulted in problems for anyone?

Ah, status report

I finally built a table to put this monster onto ;-) So the base and the "portal" are in place, after I figured out which screws need to go where (no instructions, and some screws have same diameter and threading, but differ in other parameters )-
But it's not all done yet, still some mounting going on.
I also had trouble with getting to install LinuxCNC.
Am also entertaining the idea of getting one of those cheaper motion controllers from China. Just need to find out whether there are some with not crappy algorithms inside, I guess. They have some nice oones with ethernet support that one could mount in place of the printer port module inside the controller box. Or cheaper ones just with USB.

I have not 100% given up on LinuxCNC yet, though. But should I learn about a cheap-ish chinese (or otherwise) motion controller, I might try both more or less "at the same time" to find out which route I like better, let's see...

(I must admit I find the idea of a whole PC with real-time linux as "the motion controller" a bit weird, it is theoretically very flexible, but also from some other angles, inefficient solution to the problem, probably with worse performance than using a fast microcontroller with bare metal firmware on it ...
But I'll give it a chance I guess)

[Kjelt]

No need to lube the chain AFAIK.
Do check the cables for in the chain though, better buy quality chainflex quality cables.
Good brands are:
- Igus chainflex cables shielded ofcourse
- Lapp Ollflex
Check which you need, nr of wires, gauge etc. They are made for these applications.

[TinkeringSteve]

Ah. I guess if they are not quality flexible cables, they will go bad after some movements, eh?

I think I should look for some aquarium pump or something for the water cooled spindle. (yes I also bought a weaker one with air cooling, but in case I should need the 1,5 kW one at some point)...
I can't get over the fact that they want you tu put this pump into a bucket and then run 230VAC into it. Double insulated my butt, I do not want to get used to this as looking normal, a wall outlet cable going into a bucket of water, lol!

[Kjelt]

Well these cables are designed for this purpose to last >6 million bends and only cost about one € more per meter.
I can't see much difference besides that it is more flexible (smaller bends possible) and when stripping the outside plastick jacket came off real easy, it looked like the inner cables which are quit sturdy wrapped together and shield could move inside the jacket.

[TinkeringSteve]

Yeah, at some point, I'll probably buy shielded cables. At the latest when these here fail
For now, I will install the limit switches, connecting them as a current loop requiring some mA flow for a closed switch, which hopefully means the controller won't be confused by PWM crosstalk from the crappy cables

Different topic:
Early in the thread, Magnus strongly recommended getting a sturdier aluminum base T-slot plate, and I at least agree that the one that came with the chinese contraption seems somewhat flimsy.

The moderately priced suggested replacement at vakuumtisch.de has a wider slot interval than the chinese one, though (50 vs 30 mm).
Which means I could not use that nice big bag of "clamps" anymore, flat pieces of cast aluminum with one screw in a threaded hole, and another one in a wider slit, with a wingnut attached to it, such that you can fix the thing at a 45° angle onto the slot plate and thus easily attach square shaped objects of "any" dimensions to the plate.

Are there similar utilities available for bigger plates, or is this maybe not the best way to fix something for milling? But *something* gets mounted into the slots of such a plate, eh? I just don't know what. I guess I could fix a machining vise that way, but that's only for smaller work pieces.

[TinkeringSteve]

I also just realized that that aluminum slot table has exactly the 60 x 40 dimensions, not "made for 'cnc6040'"  I overlooked that at first.
Since 60x40 is the working area of the CNC, the real plate size is of course bigger, and I don't think anyone has such plates with those rather peculiar dimensions (77 x 48).
I am guessing that something custom made is prohibitively expensive, nonetheless I will inquire as to the price of just that, and report back here for anyone who cares. (presumably someone in the position I am in now, in 2 or so years, stumbling upon this thread )

[Kjelt]

You don't need the tslot plate to exactly match the machines dimensions unless you need to work on a workpiece that is the same size minus 3cm on the sides for clamping. Most machines have a way small tplate. If you do need it you better bought a bigger machine 

Clamping, look at the same vacuumtish site they have a lot of clamping tools, i will order there also soon 
If you need extra clamps like a box full with different nuts, bolts etc you have to look at ebay, ali-x or a local shop that has cheap clamping assortments boxes.
In our country such a cheap shop is hbm-machines.com

[TSL]

Milling PCBs is something I've done for quite a while now. I have a Carving-CNC 6040 that I added home/limit switches to it and added an output to turn the water pump on and off with the VFD. The water pump is required with my 800w water cooled spindle that does up to 24,000 rpm.

Half the trouble is engineering your PCB to make it suitable for milling on such things. The other half is making the mill as rigid as possible and the mill bed as flat as possible.

You have to pay attention to speeds and feeds + acceleration since any sharp movements can quite easily break a 0.5mm end mill or snap the tip off a 0.1mm v bit.

I use both end mills and v bits for routing but prefer the end mills since they give a superior finish. I also use a bit called a "chip breaker" that is designed for cutting through PCB.

I author my PCBs in Diptrace, output the gerbers and import to CopperCam which creates the mill Gcode and cut profile for the board. The drill output comes directly form Diptrace as a Mach3 compatible file. Mach3 is the software that controls my mill.

I then check the output of CopperCam in NC Corrector which is a Gcode editor and virtual mill. This allows me to see what is going to happen in the milling process and allows me to make adjustments to the Gcode if needed.

Once I have the final output, if its the first prototype, I "cut air" This is where you set Z to 10mm or so above the bed and run the code to see what the mill is going to do without actually cutting anything. This some times exposes nasty moves that might break a bit or shows up moves that should be faster than they are.

I secure a piece of MDF or aged pine to the CNC bed for use as a spoil board, clamp that tightly and then mill a pocket into the wood using a finishing profile. This makes for a almost perfectly flat surface on which to mount the PCB and gives something for the drills to go into when you do your drill run. You don't want holes all over your mill bed, do you ?

I mount the PCB to the wood using double sided Bear tape. This is only about 0.1mm thick and as sticky as hell. I use a roller or block to press down on the PCB to make sure its adhered to the spoil board.

The process is then mill, drill, cut

Pictures of my rig attached

[TSL]

My preferred tooling is from Kyocera, they come with depth rings so that tool changes are all accurate once you have set initial Z.

Here's the box off drills and bits I use

The larges drill in that box is 1/8", the smallest mill bit there is 0.4mm

[TSL]

Whether your building your mill or not, one of the first things you should do after you have tuned the motors to the software, is run a standard test pattern.

The most common is called circle, diamond square. More info here...

https://timf.anansi-web.com/wp/circle-diamond-square/

This test pattern will enable you to check the accuracy of the cut and it will expose any non linearity in your mill quite quickly.

It will also expose over acceleration since the arc cuts stress the drives nicely and they will miss step if your acceleration is to high.

I've attached the pattern for your use.

[TSL]

Here's a few pics of my design process and the resultant boards.

You will notice the boards are different from what is on the screen which was version 1.0.

While I was initially going to have a two part board I decided to make it a single board with a cut out for the FET and mounting holes to secure the heat spreader.

So the boards are actually v2.3

On the screens, from left to right, is Diptrace, NC Corrector and CopperCam

The boards are prototypes for an LDMOS FET amp at 1296 Mhz.

If the FR4 behaves as I expect and they work as I expect then I'll redo the boards on Rogers 4003, test that and maybe then I'll send to fab.

[TinkeringSteve]

Hey TSL, or shall I say alien cook?
Thanks for your info!
I'll digest that on the weekend.

For now my plan is to try it with LinuxCNC first, and if that doesn't do it for me, well to (successfully) use Mach3 I'd have to buy a motion controller first.
The PC I put aside for this tests well on the LinuxCNC real-time test, although the speed is still poor (like 30 kHz) and with still huge jitter compared to even cheaper embedded motion controllers. But some people are happy with it, so let's see.

I haven't really tried anything but the spindle motor yet, as I have not yet installed the limit sensors, and was busy building the table, and designing a noise reducing enclosure which I now also need to build :-D
And still waiting for the replacement water pump for the spindle, as they sent me a broken one, so for now I can't let this run for all too long I guess.

[TinkeringSteve]

Btw,

I recently made that other thread, about grounding the spindle motor to protective earth, I guess Kjelt's DIY machine is all so massive that it's earthed by itself
Anyway I'm curious, what does the ground connection for the AC motor look like on your machines?
(my china CNC had none, so I need to retrofit one. The other thread, with more generic title, has some suggestions, but I'm still curious what your setup looks like)

[Kjelt]

I also have a China spindle. My CNC machine frame will get its own litze wire to PG. PG from the mains cable as well to the controlsystemboxes.
Since the VFD cause lots of EMC noise I keep those wites seperate from the motors and control cables and will let them drop down from the ceiling with the dusthose and mist cooling hose.

The spindle cable is 4x1,0 shielded cable. three are motor cables, one PG.
The shield is connected to PG in the control box and in the connector will be connected to the PG wire to return to the box. There will be no connection to the spindle of the PG in order to prevent groundloops.
The spindle is itself bolted to the Z axis with 8 bolts and that should be PG from the chassis but I have to check that.
My machine is still in the build phase currently it looks like this, the stand is from iron it was welded by a friend of mine. The feet have been replaced by heavy duty feet.

[TSL]

My spindle has a 4 pin connector in the top and a 3 core cable , one of which is earth. I took the top off the control unit to check and its wired back to mains earth.
I've never had electrical noise issues with mine.

[Kjelt]

My spindle has a 4 pin connector in the top and a 3 core cable , one of which is earth. I took the top off the control unit to check and its wired back to mains earth.
I've never had electrical noise issues with mine.

Is the frame of your machine seperately grounded, if no than that flimsy cable is your PG of the whole machine, just that you know it 

[TinkeringSteve]

Whoa! Ground loops, I hadn't even thought about that in this context. Something I still need to look at.

About the separation of VFD and control cables... by control cables you really mean cables that have control voltages, not big currents yet to the ...steppers I was going to say, wait, you have servos, right? Or at least some sort of closed loop system, so that's different from my simpler setup.
I have only cables to the steppers, where all the pulsed current is flowing, I would assume that they will not be impressed by some 400Hz 3-phase AC crosstalk running alongside?

Thanks for the photos.  That's quite a massive beast you have there I see, that won't bend so easily.

EDIT:
For the record, I *can* hear my VFD in a medium wave radio, but it's not as bad as I would have expected.

[Kjelt]

Ah ok, in your case no, the motorpower cables are pretty noisy themselves as long as you use also a shielded cable for them and they are good flexible quality (we discussed that already) than you don't have to worry about them.
For my situation I have easy servo steppers that have an encoder cable, those need to be pretty good shielded from noise or the drivers might go berserk.
I have also the homing sensorcable which is an open collector cable so also not that prone to noise and I have a lighting behind the spindle that is also not a problem.

Grounding is something to look at. Pretty much create one star ground in the controlbox and run all shields from the shielded cables to that point and don't connect the shields on the machine side. That is pretty much the generic advise given in the cnc community. Ofcourse grounding the machine itself properly would be advisible esp when high voltages like the spindle might make contact to the chassis somewhere.
Also if you have a VFD use a proper mains filter, or the rest of your house or neighbours might suffer, the radio is the least of your problems 
Then some people have problems with the VFD and the Earth Leakage Circuit Breaker, there is a whole topic about that on this forum. I would advise first see how it goes, if it runs keep it like that, if problems arise take a look at that topic.

[TSL]

Is the frame of your machine seperately grounded, if no than that flimsy cable is your PG of the whole machine, just that you know it 

You know I never really thought of that and I should know better!! I’ll see about putting a nice heavy ground back to the control box

[TinkeringSteve]

Ok, some reporting back here. As I now had some time to play with this thing again.

One thing people who also buy this thing (my "exact model"  is the CNC 6040 by "CNCEST" as sold by chinese ebay sellers, that name is on a sticker on the device) -

the longest (Y) axis' ballscrew is wobbling around.

I have not read about this as a problem anywhere else, where people mention the "by design" shortcomings of these chinese CNC routers, so probably "my" manufacturer just screwed this one up.

To demonstrate:
Running - note the motor coupling to the right:


Stopping after some steps, so you can better see how the distance between ballscrew and the steel angle thingy changes, depending on rotation angle of the motor:


Here my crude attemt at measuring the deviation, roughly 35/100 mm total, at the edge of the coupling anyway:


Looking at the ballscrew itself, it looks like a lot more than just 0.35mm, though.
So this will probably break the bearings if I use it that way, I wonder how they managed to get it that bad.
The frame of the whole thing seems relatively sturdy as such. Then again, the gantry and all the stuff on it are pretty heavy. Maybe I was less lucky than others when moving the whole thing around on the desk, and the whole setup warped somewhere?
Or they just screwed up, tired at end of working day or so

Now, I am currently struggling with the ebay seller to make him understand the problem, and he's playing dumb, of course He already did that when I showed him a photo of the ingenious re-design of his water pump - the brass connector piece for the output hose was solid, i.e. no hole for water to come through, and never mind the broken off pieces of plastic from the side of the pump - I guess more water comes in, as compensation for the "tight" output!

I reminded him that paypal protection is still on for a number of weeks, suggesting he makes better suggestions than so far.
Let's see how that turns out...

From what I gathered by a post in another forum about the proper setup procedure for such a ballscrew and bearings, it sounds like I could never possibly do such a thing myself, as bulky, complicated, expensive precision parts are required.

So the only real option is that I send the base with the Y-axis parts back for repair, eh? (apart from returning the whole thing).

[Kjelt]

How "long" is this ballscrew axis and does the linear guide not compensate ?
So if you move the Y axis do you notice the change in height of the table that is moved or does it get stuck move less easy etc. etc.

[TinkeringSteve]

How "long" is this ballscrew axis and does the linear guide not compensate ?
So if you move the Y axis do you notice the change in height of the table that is moved or does it get stuck move less easy etc. etc.

That axis is about 75cm long.
The "linear guide" are those 2 big round steel axes on the sides of the whole setup?
I have not seen the table move up/down, and it does not appear to be impaired in its movement throughout the whole length of the ballscrew.
The reason why I even found this at all is that I was moving back and forth along that axis and heard occasional clicking sounds. I didn't know what they were, thought "oh no, is it the bearings?" and looked under the thing...
But now I actually think the clicking comes from the plastic cable chain elements / hinges, making noises as the chain unfolds.

By "compensate", what do you mean exactly? If the rail guides on the sides force the whole thing to remain within the Z=0 plane, but the ballscrew wobbles, doesn't that mean it will crack the stepper motor's bearings at some point? Or the "sliding" one, when it's close to the wobbling source.

[TopLoser]

Google ‘oldham coupling’

Ideally the shaft would be better supported at the driven end, but you get what you pay for.

[Kjelt]

Yes toploser you're right i didn't see it before but there is no support behind the motor to axis coupling, 
That is insane. All designs I know off have the ballscrew axis supported at both sides and after the support the motor is connected and mounted.

[TopLoser]

Looking closer I'm not 100% sure it is a proper oldham coupling, probably just some flexible coupling pressed in between the two halves so removing the need for the support at the driven end.

It's shoddy and cheap but works, I can see why it's been done that way. I wouldn't lose any sleep about it in that application, even with the bit of wobble.

[Kjelt]

It is not devistating indeed but not as it is supposed to be. Probably the results are ok'ish, you get what you pay for.
Usually you have two sides supported with bearings where the side of the motor is supported with a fixed bearing (screw mounted) and the other side is loose (just stuck in a bearing). The motor side is usually fixed because that is the mechanically driven side of the axis having the most mechanical forces on it.
I can't see the entire construction so can't comment further.

[TopLoser]

I guess they saved a bearing and are using the motor bearing as the support. Shoddy, but there's not a lot of radial load (that flexible coupling absorbs most of it) so nothing should fall apart.

Can't see if it's possible but if the OP is concerned about the wobble then loosen the motor fixing bolts and move it about till the wobble is minimised.

But for the money....

[TinkeringSteve]

I just found a blog post by someone who also has a Chinese "CNC 6040" machine, visibly of the same basic design, alas the coupling isn't on any of the photos. He wrote that his machine was, after 8 years, still "going strong", and he did some aluminium with that...  (no mention of frequency of use, though)
I mailed him about whether his has an extra bearing there or not, out of curiosity

Looking closer I'm not 100% sure it is a proper oldham coupling, probably just some flexible coupling pressed in between the two halves so removing the need for the support at the driven end.

It's shoddy and cheap but works, I can see why it's been done that way. I wouldn't lose any sleep about it in that application, even with the bit of wobble

Hrm, and what about the sliding bearing that takes the wobble? Probably also some "plastic buffer" in there or what?
Looky there... that also looks interesting:


Reminds me of when I first unboxed a KitchenAid 550W blender and seeing the coupling: "why is there plastic???" (or even rubber, IIRC)

[TinkeringSteve]

Can't see if it's possible but if the OP is concerned about the wobble then loosen the motor fixing bolts and move it about till the wobble is minimised.

LOL! So that's what the seller meant, after showing the factory my video, by saying "remove Y-axis board, adjust the position".
Ok I still don't get the "remove the board" part, but if they mean the X,Z motor position (he did not mention the motor...), that reply suddenly jumps from "0% sense" to "makes some sense"

[TinkeringSteve]

Btw., the basic setup of such a device can be seen here:
http://inventorartist.com/cnc-machine/

Now there are different variations of them around with some details different, resulting in different prices. But that's roughly what I have here.
Ah, my motor clamp is somewhat different:
http://i.ebayimg.com/images/i/131982947836-0-1/s-l1000.jpg
And see, it has "structural stability"! Lol.

[TopLoser]

I think you have to manage your expectations of what you’re going to get by paying a crazy low price to an unknown Chinese company. One that’s competing against countless other Chinese companies all trying to save pennies trying to be the lowest priced.

I’d be happy it arrived and worked at all.

Remind me never to sell you anything lol

[SparkyFX]

To calculate the actual influence of the wobble on the result, you would need to get the cosine error (the distance the leadscrew pushes or pulls the gantry for this amount of runout at this angle).
Of course you measure 35/100mm runout, but if your ball screw is at 0° angle, it might not move the gantry at all, depending on the bearing position and gantry position.

I assume based on the very shallow angle there is not much movement side to side or up/down, probably below the amount of play. So it does not directly influence the work. The gantry itself has more bearing surfaces holding it in place.

[TinkeringSteve]

I think you have to manage your expectations of what you’re going to get by paying a crazy low price to an unknown Chinese company. One that’s competing against countless other Chinese companies all trying to save pennies trying to be the lowest priced.

I’d be happy it arrived and worked at all.

Well, I chose a seller who had many ratings and almost 100% good on ebay, and the ratings came from devices such as that, not a lot of 1$ articles All the different varieties floating around have some differences by which they can be told apart. More or less. And I found a couple people who had "exactly that" and were content. But I guess they clone even that. Anyway, the buyers of such machines of the very seller seemed to be content. So "glad that it works at all" may be slightly exaggerated

I'm not sure about it being a "crazy low" price for a bunch of parts like that, with a minimalistic design. People who buy the "real machines", made e.g. in Europe, pay something like my car costs - new. I think my car is a bit more complicated than such a router, and also has some critical tolerances somewhere.
I was aware that that kind of thing would not be usable in the way heavier machines can manage. But they could at least pay attention to set up things as well as they can actually manage, not less

Remind me never to sell you anything lol

I very rarely buy stuff even remotely in that price range, let alone from China. There were no viable alternatives. I had to try, there was at least some good precedents to be found on the net

[Kjelt]

The cheap K40 china lasers are also usable but not good, there are whole lists of improvements from users you can make, doubling the total money spent.
However cnc routers depending on the material can get large forces on the machine parts. So I would stay away from ferro metals. Wood, plasticks are fine but even aluminium might be too much. You will know it when you are missing steps or the machine makes too much noise.

[langwadt]

I guess they saved a bearing and are using the motor bearing as the support. Shoddy, but there's not a lot of radial load (that flexible coupling absorbs most of it) so nothing should fall apart.

Can't see if it's possible but if the OP is concerned about the wobble then loosen the motor fixing bolts and move it about till the wobble is minimised.

But for the money....

stepper can take take quite a bit of radial load, they have to when used with a belt and they use normal ball bearings
they can't take axial load but that should taken up by the bearing at the other end of the screw

[TinkeringSteve]

Kjelt, btw., the seller himself clearly listed steel as a no no for this machine, so they're at least that honest

The guy with his machine that lasted 8 years replied to me. He said his does have support bearings on both sides, but he also bought an extra machine more recently, which is noticeably lighter, "but still ok", for his purposes. Interesting, so that's probably the "make things yet cheaper" of the past years. His aluminum profiles do look thicker, for instance.

[Kjelt]

I hope it will serve you well over the time you need

[spiritburner]

Tinkering Steve

I have just found this post and I am going through the same as you.....Did you actually get a definitive answer to your questions on which model to go through, i see the post now is quite old and the machines now have moved up a little,,, what did you do in the end.....tx for any help Neil