going into the unknown of CNC PCB milling

[Simon]

After a few prototype PCB constructions I'm starting to see that with another option available it might just not be worth the trouble of fiddling with those chemicals that will need desposing of and trying to get that perfect printout on tracing paper only to make the odd prototype.

I know about the possibility of using a miniature CNC mill and its looking ever more attractive, while it will mean an investment I'm thinking of making it up to a certain point.

I've come across another good looking happyseed listing: http://cgi.ebay.com/CNC-Router-Engraver-Machine-PCBs-engraving-Free-Post_W0QQitemZ360224514338QQcmdZViewItemQQptZLH_DefaultDomain_0?hash=item53df0de122 that is a complete setup for a reasonable sum but would like some advice or rather opinions. the PCB software I'm currently using will only output image files or prints but the machine comes with MACH3 software that from what I can tell from their website will accept JPEG images and the like using a freely supplied conversion utility.

I'm also not impressed by the fact that it uses a parallel port but hey even my current workstation still has one so maybe thats not an issue ?

There is another unit on ebay but it is more exspensive although it does not say what port it uses http://cgi.ebay.co.uk/Sable-2015-CNC-ROUTER-ENGRAVER-mill-PCBs-engraving_W0QQitemZ200426268706QQcmdZViewItemQQptZLH_DefaultDomain_0?hash=item2eaa562822
but I think its going to work out a tad over my budjet and the software I think is linux software although I don't have a huge issue with that as I have a spare PC I can run linux on.

Well I'd just like your opinions and advice and maybe stories on how you started up with cnc pcb production

my idea is that with the much reduced cost of making the boards as the blanck boards are cheaper if not photosensitive and I won't need the chemicals anymore.

[eswets]

Why not DIY CNC machine?  I am working on that right now.  Lot cheaper than those you listed.  Just etched my board for the controls, program is free for hobby use.  Looking for stepper motors and designing my rails.  Let me know I can find some links on this.
Eric

[charliex]

cnczone.com is a good place to talk about them, i read a lot on there before i picked up mine.  People seem to buy the sable, say i'll be back soon with reports and never reappear.

the fireball v90 is popular too http://www.probotix.com/FireBall_v90_cnc_router_kit/  http://Fireballcnc.com

CNC PCB gets pricey really fast, the bits aren't usually cheap and they're easy to break, but its a lot of fun, decide on board size, number to produce, smallest trace size etc you want to achieve as well as price and that'll limit the options available.

Also have you looked at the laser toner transfer method ? seems slightly less messy and easier.

[Simon]

If I'm using laser toner methods I might as well use the current UV exposure method.

I'm not really equiped to make my own CNC machine, I don't want to have another hobby to serve my main hobby i just need to get the machine, but need to know what I'm looking for. the fireball V90 machines are as costly as the ones on ebay like the sable and like the sable the photo shows a nice complete machine but you just buying an MDF frame, at least the sable is made of metal

[charliex]

Yeah you're looking at probably around $1,200 for a completed build, that red/blue one you posted looks complete just well used, but i'd be concerned about the play. Parallel port is pretty common as it cuts the cost down and its all existing tech. I think you might be let down with that red/blue one though, it looks a bit shonky.

I feel the after support is pretty important with these, the fireball might be mdf but it has a lot of users.

cheers

[Brett]

Wow, this is exactly what I'm looking into as well!  Over the holiday break I stumbled upon DIY Milling Machines conversions to CNC, and it's just went nuts from there.  I've personally been thinking I'll get the most use out of a desktop CNC Milling Machine, which could have a high speed rotary tool attachment put on it for engraving.  I just didn't think it looked that reliable at the time to route PCBs.  I hope I'm because that would be a great benefit to having one of these machines.

As stated, that cnczone.com is about the best place for cnc everything.

Littlemachineshop.com has some nice conversion kits for the harbor freight mini milling machine, which would be a really cheap option to start if you used one of those 20% off coupons.  It would be about $400 for the milling machine, and who knows how crazy expensive it can go from there!  Literally, the sky is the limit... beware.  Hahaha.

I've seen the router type tables as well, but they feel too light duty to me.  If I got one of those, I'd probably end up getting mill and a lathe in addition eventually.  I was also looking at a benchtop laser etching/cutting machines... now those start at $3500 or so for the Chinese ones.  I wonder if they can do PCBs as well?

Good luck on your hunt.  I'd like to hear how your PCBs turn out.

EDIT: I was going to also say they make USB to Parallel port converters... that seems like it should work, although there's nothing like a REAL parallel port... lol

[charliex]

Unfortunately usb parallel to convertors, aren't really that they're generally usb to centronics or just work with printers only. they're worse than usb to serial. usb isn't really well suited to either.

Parallel ports are really useful since you can bitbang on them (switch on and off digital out ) but the timing  is very important, thats one of the reasons you see a lot of linux based cnc's because they don't know how to do it on windows, since the motors are directly being controlled by the parallel port, so if it needs a 1ms pulse, it can;t be different.

The PCMCIA adapters usually work, i recently picked up a PCI one, and it was a usb chip on a PCI card !

[Simon]

hm this looks like something I'll be keeping my eyes on and investing in later maybe, I can't really spend more than 400-500 GBP.

why does the red/blue one look "rickety" ? he has stated that the motor(s) is/are used but I don't know how durable these mtotrs are. I presume the sable is new and it looks like a supperior machine but if you think size etc then the price of this one seems to be in line.

[Simon]

Regarding the Sable (that maybe is worth it but after some saving and learning) I've found the below quote on cnczone ( http://www.cnczone.com/forums/showthread.php?t=62815 )

OK, it has come. The Sable 2015 is finally here. What did I find in the box?

First, what did I order? I purchased the CNC for $499, the power supply, driver board the milling motor and everything else with it. I was originally going to use a driver board that I had prior to purchasing the CNC, because it was my plan to put one together myself. That option will be done, later. So, let us go back to the CNC machine.

The framework for the CNC could not be any better. It is made entirely of metal. Steel and aluminum are used; everything is a nice and tight fit, with everything working, as it should. I am impressed with the machine so far. I had thought I would get a basic CNC with quite a bit of MDF, but a metal machine showed up with nice tight tolerances, so there is no rattling of the machine.

From what I can tell, so far, the machine looks like it is an excellent machine. The only thing I found to complain about is its size. It is very small, but it will be good enough for my needs, and can be used to manufacture small parts. (6 – 9 inches). Oh, one more problem just popped into my head. It does not come with instructions. I say that with a qualification. It does not come with instructions written in English.

Most of you folks already know how to set up a machine. The machine configuration is simple and intuitively obvious, so there really is no need to include them. HOWEVER, since this is priced in the starter range, it would have been nice if he had included instructions in English. He did make one misleading statement in his eBay pages. You will NOT have to fabricate your own cables. If you buy everything as I did, the cables come with it.

I have a coworker who is planning to build a small machine so that he can fabricate the parts to build a larger one. That would be entirely possible with the machine.

Luke Chen sells a quality machine, made entirely of metal. I am very satisfied with the product. I do recommend this machine.

Once I get it running this weekend, I will write more. Work just takes it out of me, so I turn into a vegetable when I get home.

JimB
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looks like a good machine from what he says. I'm wondering if they are for sale elsewhere outaside of ebay (realy the crazy ebay fees do push prices up), another worry is the possibility of import tax

[charliex]

The red blue one just looks a bit loose, any play/excess runout will result in large errors in the cutting, you may end up having to replace the router and motors in it. Obviously its hard to tell from pictures, but i'd think twice about it.

I'm just suprised that we haven't seen more reviews on the sable, a few people bought them, I did the same thing as you mid last year, and it was one i was considering, but it couldn't cut the traces i wanted ( 8 mil ).

If i recall there was a lot of talk about the sable's table being bowed/not level ? which is fixable

[Simon]

I've thought maybe I'd best stay away from the red and blue one. I think happyseeds just sells what he gets and does not know much about it, I'm best going for the sable (and I can get one from europe if I'm worried about the import costs). if the Sable's table is not level (and that was mentioned a year ago) surely something can be put on it like a thick sheet of metal and then machine it flat with the machine itself ?

[Jim]

For what it's worth, I have some extensive experience with CNC PCB milling. I purchased a purpose-built mill (Proxxon MF70) with a tidy CNC interface and software, a couple of sets of tool bits of various sorts, and a kit of accesories to hold PCBs down, etc. Came to around Euro1000.

I've also worked with iron-on toner, spray-on developer, and several other methods.

My conclusion: The CNC mill has some significant limitations.

The good things:

1. I can make a PCB when I feel like it.
2. I don't feel like I am getting chemical poisoning when I make a PCB
3. I can make really interesting shaped PCBs, milled out to precise dimensions. Did one in a crazy Xmas tree shape a few years ago for the festive season. Went down a treat.
4. Most important - I can use the CNC for lots of other projects, like milling front panels, and a bunch of other little bits and bobs for other hobbies and stuff around the house which would otherwise be impossible to do. Wins big praise from my wife and family.

The bad things:

1. Much depends on the software you use. I use PC-NC from a German outfit. It was cheap (Euro70?) but it is not easy to use, and it requires a bit of relearning each time I go back to do another PCB. I don't make many - maybe one or two each month - and I have to just go over a few things each time to make sure the settings are right each time. Yes, other software is available, but it takes a considerable time to get a package up and running. It takes less time to review where I was up to with this stuff and make the board than mess around with something new.

2. The PCB must be absolutely dead flat i.e. within about 0.1mm from side to side, corner to corner, centre to edge, you name it. On small PCBs (30mm x 30mm) this is no problem. And this must be repeatable i.e. sustained as the mill head goes up and down, maybe a few hundred times on the average PCB. Backlash can be an issue, but mostly, its getting the milling table and the PCB(!!) flat, and keeping it flat. Any offset larger than this will likely result in a PCB which is not going to work out. I aim for 0.05mm. Yes, really.

3. Tools must be sharp, and the table/mill must not vibrate while in use. My carbide tools seem to last about five times (PCBs avg of 50 x 100mm in size, fibreglass) Phenolic PCBs will let you use the tools for maybe up to twice this time.

4. Every PCB needs a clean-up with a very sharp pointer. This has to be run around every track by hand while you look at it though the biggest magnifying glass you possess and under the brightest light you can find. Otherwise you will be plagued by tiny, near-invisible scraps of copper which seem to be left by the mill. Some PCBs are better than others, sometimes this doesn't take too long. Other times, it's an absolute curse. Keep Valium to hand.

5. It takes time. On average, a couple of hours. Yes, I see you laughing. How can it take so long? Well, usually it takes longer! you have to take the PCB layout, convert it into a suitable format for the machine, set up the PCB, check every setting and the flatness, and then let it run. It takes time.

6. There are limits to the size of PCB that the machine can handle.

7. It makes a mess. Milled copper and PCB material go everywhere. I use a vacuum cleaner hose held close to the job to keep this under control. So, having given up poisoning by chemical etching, I now expose myself to lung cancer from particulates. Go figure.

8. The boards do not look like the perfect ones you see in the ads. Sometimes, maybe, but mostly not. They tend to be a tad rougher in my experience. Once they are in the final box, it's all out of sight. Still, I'd like them to look nicer.

9. There is a limit on the sort of PCB that can be made. 15mil conductor widths are just not possible. Sorry, no. Not even on the really expensive CNC mills, despite what the ads say. Doing surface mount stuff on a CNC mill is a good way to stress yourself out. But, hey, don't believe me. Go try it for yourself.

All in all, I'd pause before going down this avenue again. I'm thinking about trying laser milling, myself. Maybe that's the answer....

But, hey, maybe you guys have answers to all these things....

[Simon]

You make some very valid points Jim and the reason i started this thread was to hear this sort of thing.

As you say a cnc mill is very useful for many things, hey I just told my sister she could emboss cake decorations ! (got a funny look of course !)

I'd like to have a CNC mill available for a variety of things and so far I've not got into SMD, the other thing is my current stage of pcb etching with chemicals I can't do thin traces anyhow !

[Simon]

Of course there is another "angle" to this method, what about using the cnc mill to "plot" the pcb with a permanent marker pen ? that would eliminate the problem of a bowed board to some extent. not sure of other advantages, anyone got any thoughts ?

[Jim]

I doubt the permanent marker pen method will work either if the board is not flat. Same basic issues apply: Variable track width is the biggest problem, plot file conversion might still be an issue, and then you are still faced with the dreaded chemical etching process. Also, I've had different results with using permanent pens. Sometimes they worked well, other times they didn't. Never got consistent results.

I did try using an A4 laminator along with laser printer plots on glossy paper to make PCBs. This is also described in glowing terms on some websites. Well, it works well for me for PCBs that are about 30 x 30mm, or maybe just a little larger. Anything bigger, and it just plain doesn't work. It seems that larger boards cannot reach a suitably high temperature to get proper fusing to the PCB. Shame. That one had real potential since laminators are really cheap.

The objective of my CNC mill purchase was to get a simple solution to one-off PCB production which was also consistent and (reasonably) safe. But I just have not succeeded in that objective. I can make it work, but it's not easy, consistent, or cheap. Clearly cost was never going to be low. After all, how many boards do I have to make to get payback on my purchase? Let's not go there!

I have heard/read good things about the CNC mill kitset offered via Elektor magazine in Europe a year or three ago, but I suspect it will also suffer similar problems to mine in reality. I think that people who have gone down this costly CNC milling path are seldom willing to admit the real truth about these machines, given their financial, time, and, in some cases, emotional investment. Or maybe it really is a good solution.

I do like the idea of converting a printer into a PCB printer which I've seen discussed elsewhere. In theory, this addressed many of the problems of one-off board production. However, when I've opened a couple of old printers of mine, they always seem to be too different from those discussed/shown to allow me to easily modify my printer(s). And then there seemed to be reports of different results with ink cartridges from various vendors, etc.

[charliex]

a lot of people use carpet tape or superglue to hold down the PCB, i use sellotape which has worked for me, you have to tape down all four sides, everytime.

Once i've got my gerber's cam'd out from eagle, it takes about 5 minutes to setup the cnc software, then however long it takes to cut, a few minutes to flip the board, then about 5 minutes to align it for the second cut (but i have a registration camera)

the cnc i use integrates a small shop vac with a remote that goes directly into the routing head so most of the waste material is picked up during cutting, only when i'm cutting the FR4 does it leave waste behind but its in the channel so easy to suck out ( you don't want too much vacuum or the head might get stuck )

i wanted to produce larger boards with 8mil traces and make some other things too like bezels etc. my working area is 16x12x2.5 inches
 
i use bits from precisebits since i like their customer support a lot,, some places  sell resharpened bits which are a lot cheaper. It takes some time to get the boards to be repeatable, and you pick up things, like i'd been using a V90 bit and switching to a V60 made things a bit easier.

scotchbrite grey/red(carefully) pads are what i use to clean off the swarf, and having software than can do unused copper removal helps too.

i'm pretty happy with the results of my machine, and the problems i 've had with it are operator error, its a lot more versatile than chemicals but as i said it is a really expensive initial outlay.

I think CNC's are like boats, its great to own one, but its better to have a friend who has one.

[Simon]

it looks like the biggest issue is with tools wearing our quikly ? and the cost of replacement. I'm also doing one offs and possibly a few of a board in the future. I suppose I'll plod on with chemicals and then think of CNC's later as I'm interested in milling (they have to kick me out of the machine shop at work !).

[Jim]

Charliex, sorry to be so dim, but can you explain more about the "registration camera". Not something I've come across.

I tried the idea of holding the board down with tape, but it didn't seem to be quite good enough for the larger boards (100mm x 70mm) I tried. As the tool got to the edges, the vibration seemed to work the PCB out of alignment. I stuck with the hold-down clamps from Proxxon, but these have the disadvantage of holding down the edges. The problem then is that, the tighter you hold down the edges, the more likely it is for the centre of the board to flex upwards. It's a classical 'lever' action thing.

So, I have this tradeoff between balancing 'just enough' downward force on the edges with resultant upward flexing of the PCB. Phenolic is bad for this, while fibreglass PCB is much better at resisting this flex.

[charliex]

superglue might help you out there.  Did you use carpet tape ? i've held down decent sized boards.

the video registration is just a way of realigning the board after you flip it to cut the second side, you basically use the video cameta to give it two reference points and the software determines the new position and rotation of the gcode. you find a drill hole, tell it which hole on the gerber it belongs too, the software moves the gcode, then a second hole away from the first, and it does a move/rotation of the gcode to match up.

you can mostly see it how it works here, about halfway through

[Jim]

Ah, now I see what the camera is doing. I think your setup represents a significantly increased investment than my simple CNC system. 

No, I've not tried the carpet tape approach. My initial reactions to that suggestion, and to the Superglue, are:

1. Is it tough to get the finished PCB off the milling table?
2. Is there any tape/glue residue left after the process? - This could be a problem for the next time around, and I'm not terribly keen on using scrapers on my milling bed to get off any residue.

But are my fears really groundless?

[charliex]

Yeah i got lucky and got a free camera upgrade, but the base unit is a hefty price tag, but its a lot less than others.

you use a sacrificial material and bond to that, acetone removes the superglue.

the chap over at millpcbs.com has a few videos where he uses superglue

too much acetone for too long is bad for FR4, but you can work with it for a suprising amount of time, when reverse engineering boards that are enclosed in something, i've submerged whole pcbs in acetone for 6 hours with no problems, removing glue is a lot faster. i use whats available at ace hardware. I've even used MEK with no problems.

if any residue of tape is left, goof off or goop remover etc works great, they're usually a petroleum distillate mixed with some oranges or something

[badSCR]

..... I'm thinking about trying laser milling, myself. Maybe that's the answer....

you can laser mill a PCB ?   
what kind of conductor widths are possible with laser mill a PCB ?   



http://www.cnczone.com/forums/ 
http://www.cncinformation.com/

[Macka]

I know this thread is getting a bit old, but anyway...

Just a few weeks a go I was looking in to building a CNC machine myself, did heaps of reading and even started looking at prices of things. The deal breaker for me was the drill/dremmel and the price of the drillbits, though I may look into it again this time next year, if I manage to get a part time job to pay for it.


Anyway, the point of my post:

I have seen some very good CNC setups, homemade and prebuilt and hybrids; all turning out results between quite good and brilliant. The better ones were more expensive or had more advanced pieces to them (and weren't necessarily prebuilt). Things I picked up that made these particular machines better were floating heads, prelevelling, use of CNC linux and correct setup of the software.

Floating heads help with uneven boards, apparently PCBs can vary significantly in substrate thickness across the entire board, so the drillhead is setup to detect the surface of the PCB.

Prelevelling involves placing a sheet of MDF on the table and drilling out an area of a consistent depth and placing the PCB into it.

CNC Linux is a realtime linux distro that helps prevent problems the parallel port faces under windows. Perosnally, If I get around to building a CNC machine, I want to use a PIC as the controller and eliminate the PC altogether from the actual milling. I'd add SD card and USB support to allow the Gcode to be loaded to the MCU and then it can process it instead of relying on the PC to do it for me, also makes it more portable; I'm not sure if it will work as expected though.

[Veramacor]

I built this one from this guys plans.

http://www.solsylva.com/

I have to say I dont miss etching with chemicals.

As far as traces,  precisebits.com has what he calls a mechanical etching bit that produces SMOOTH trace lines.  I've never had to clean the trace up with one of those bits,  but they are expensive.

It is a steep learning curve - I still don't know much about CNC after this build, but if you like to DIY,  I can't say enough on how gratifying it is.

I would suggest not building a 24"x48" table to do PCB though!  I was thing about building a table top version, but my current one does a good enough job.

The drilling is what makes it really worth it.  You can setup Eagle to generate both the trace and drill gcode files using and add-on called PCB-Gcode.

I limit myself to one-sided boards currently.  I havent attempted anything more complex than that.  Two sided boards can be a pain on a cnc, but again I haven't really tried! 

[onesixright]

Hi,

Anyone know what is the max. size (width/height) of a PCB you can place under the MF70?

Thanks.