Author Topic: China CNC routers - 3020 oldschool vs. 3018 GRBL control  (Read 33691 times)

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Offline TinkeringSteveTopic starter

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China CNC routers - 3020 oldschool vs. 3018 GRBL control
« on: March 17, 2018, 08:23:25 am »
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?
« Last Edit: March 17, 2018, 08:29:15 am by TinkeringSteve »
 
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Offline Magnum

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Re: China CNC routers - 3020 oldschool vs. 3018 GRBL control
« Reply #1 on: March 17, 2018, 11:38:33 pm »
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.
 
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Offline Magnum

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Re: China CNC routers - 3020 oldschool vs. 3018 GRBL control
« Reply #2 on: March 18, 2018, 12:18:43 am »
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.
 

Offline Bryce

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Re: China CNC routers - 3020 oldschool vs. 3018 GRBL control
« Reply #3 on: March 20, 2018, 02:25:17 pm »
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.
 

Offline TinkeringSteveTopic starter

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Re: China CNC routers - 3020 oldschool vs. 3018 GRBL control
« Reply #4 on: March 20, 2018, 07:36:16 pm »
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:



Quote
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?

Quote
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.

Quote
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.

Quote
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.
 

Offline TinkeringSteveTopic starter

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Re: China CNC routers - 3020 oldschool vs. 3018 GRBL control
« Reply #5 on: March 21, 2018, 11:03:52 pm »
Btw, maybe someone can say something about this:
The 3020 / 6040 apparently have no limit switches? (Endlagenschalter, for the germans).
That sounds kinda insane.
 

Offline Magnum

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Re: China CNC routers - 3020 oldschool vs. 3018 GRBL control
« Reply #6 on: March 23, 2018, 07:30:27 pm »
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).
 

Offline TinkeringSteveTopic starter

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Re: China CNC routers - 3020 oldschool vs. 3018 GRBL control
« Reply #7 on: March 23, 2018, 09:16:54 pm »
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
 

Offline Magnum

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Re: China CNC routers - 3020 oldschool vs. 3018 GRBL control
« Reply #8 on: March 24, 2018, 08:58:01 am »
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.
 

Offline Magnum

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Re: China CNC routers - 3020 oldschool vs. 3018 GRBL control
« Reply #9 on: March 24, 2018, 08:58:57 am »
More pics
 

Offline Magnum

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Re: China CNC routers - 3020 oldschool vs. 3018 GRBL control
« Reply #10 on: March 24, 2018, 09:03:19 am »
The last
 

Offline Magnum

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Re: China CNC routers - 3020 oldschool vs. 3018 GRBL control
« Reply #11 on: March 24, 2018, 09:18:00 am »
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.
 

Offline TinkeringSteveTopic starter

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Re: China CNC routers - 3020 oldschool vs. 3018 GRBL control
« Reply #12 on: March 24, 2018, 10:51:04 am »
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)
« Last Edit: March 24, 2018, 11:26:01 am by TinkeringSteve »
 

Offline Magnum

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Re: China CNC routers - 3020 oldschool vs. 3018 GRBL control
« Reply #13 on: March 24, 2018, 11:37:16 am »
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
 

Offline TinkeringSteveTopic starter

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Re: China CNC routers - 3020 oldschool vs. 3018 GRBL control
« Reply #14 on: March 24, 2018, 06:47:25 pm »

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 ;)
 

Offline Magnum

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Re: China CNC routers - 3020 oldschool vs. 3018 GRBL control
« Reply #15 on: March 24, 2018, 09:29:58 pm »
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.
 

Offline TinkeringSteveTopic starter

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Re: China CNC routers - 3020 oldschool vs. 3018 GRBL control
« Reply #16 on: March 25, 2018, 10:47:00 am »
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?
 

Offline Magnum

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Re: China CNC routers - 3020 oldschool vs. 3018 GRBL control
« Reply #17 on: March 25, 2018, 11:49:15 am »
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
 

Offline Kjelt

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Re: China CNC routers - 3020 oldschool vs. 3018 GRBL control
« Reply #18 on: March 25, 2018, 04:48:03 pm »
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.
« Last Edit: March 25, 2018, 04:50:55 pm by Kjelt »
 

Offline TinkeringSteveTopic starter

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Re: China CNC routers - 3020 oldschool vs. 3018 GRBL control
« Reply #19 on: March 25, 2018, 05:51:28 pm »
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.
« Last Edit: March 25, 2018, 05:54:41 pm by TinkeringSteve »
 

Offline Magnum

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Re: China CNC routers - 3020 oldschool vs. 3018 GRBL control
« Reply #20 on: March 25, 2018, 05:53:27 pm »
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:

 

Offline TinkeringSteveTopic starter

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Re: China CNC routers - 3020 oldschool vs. 3018 GRBL control
« Reply #21 on: March 25, 2018, 06:45:14 pm »
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?
« Last Edit: March 25, 2018, 06:47:22 pm by TinkeringSteve »
 

Offline Kjelt

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Re: China CNC routers - 3020 oldschool vs. 3018 GRBL control
« Reply #22 on: March 25, 2018, 06:51:01 pm »
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.

 

Offline Kjelt

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Re: China CNC routers - 3020 oldschool vs. 3018 GRBL control
« Reply #23 on: March 25, 2018, 06:53:56 pm »
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.

 

Offline Kjelt

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Re: China CNC routers - 3020 oldschool vs. 3018 GRBL control
« Reply #24 on: March 25, 2018, 06:56:34 pm »
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.
 


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