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IndustryArena Forum > Other Machines > PCB milling > Designing CNC router for PCB milling
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  1. #1
    Join Date
    Apr 2012
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    159

    Designing CNC router for PCB milling

    I've got a Shapeoko 2 I mostly use for making printed circuit boards. But I'd like to design and build a small CNC router that's specifically designed for milling PCBs. I am going to design it using Fusion 360. I've only been using Fusion for a couple months and I think this would be a good project to improve my Fusion skills. I also want to improve my metal working skills and I think this would be a good project for doing that. I don't have any metalworking equipment of my own, but I have access to some pretty good stuff and can get help using it. I'll have access to a Bridgeport milling machine, Hardinge lathe, surface grinder, even a Haas vertical CNC milling machine (I haven't used this yet), and other stuff, but those are the highlights.

    I want to make the frame and everything out of metal I machine myself, probably aluminum. I don't want to use anything like the 8020 aluminum extrusions. Not that there's anything wrong with that, but I want do the machining so I can learn from it. I also want it to be pretty rigid. Not that I really need it that rigid for PCB work, but maybe I'll make another CNC that needs to cut aluminum so this would be good experience. Plus, I like to do things a bit overkill. I'm not too worried about cost. That doesn't mean the sky's the limit, I'm got going to be buying $1500 a precision spindle or $1000 linear rails. I hope I can keep the cost less then $2k, but if that's not realistic for the machine I want, I could spend up to $3k.

    There are two machine style's I'm considering, one is where the table is fixed like this WidgetMaster and the other is where the table moves from to back like the Sable-2015. I'm leaning towards a fixed table design.

    Some of the specs and features I'm considering
    • Ball screws with anti-backlash nuts
    • NEMA 23 steppers or servo motor like the Teknik Clearpath
    • Vacuum table
    • High Frequency spindle, at least 30,000 RPM, 60,000 would be better
    • Relatively quiet spindle
    • TIR on spindle + collet 0.0002"
    • Working area 6 x 8 inch


    I'm not sure what to do for liner rails. I could use a fully supported linear rail like these from GMT or linear guides like these from NSK. Note: I'm just linking to GMT and NSK to show the style, not that this brand or model is the right choice.

    I do need advice on the right type of bearings and how to mount the ball screws properly so they are not over constrained. Hopefully, I can assemble everything and have it be square and true without using shims. That's something to keep in mind while designing it.

    My main goal is to go through the process of designing and building a PCB CNC router myself. I don't want to buy a CNC router and modify and/or upgrade it.

    I'd appreciate any tips, suggestions, guidance etc.
    "You can't teach stuff in a school that you would learn in real life unless the real life people are in charge of the school." - Gene Sherman

  2. #2
    Join Date
    Apr 2004
    Posts
    733

    Designing CNC router for PCB milling

    Building something similar too. Will be using it for small milling and engraving of non ferrous material

    Look for C3 or better ground ballscrews off eBay for cheap. This is similar to what I purchase. C1 grade too. Expect to pay many times more for new.

    http://pages.ebay.com/link/?nav=item...obalID=EBAY-US

    I buy all of my linear components on eBay. If you look long enough, you can get new THK or NSK for great prices. My most recent purchase was a pair of 45" NSK LS20 (two rails, four carriages) for $80 free shipping. Brand new still factory sealed in original box. Much longer than I need so I will cut them down to length. For that price, it doesn't matter if I do.

    Mine will be servo driven and I picked up some new applied motion brushless drivers for $40 each. I think they are $600 new. The CMC brushless servo motors were also eBay, $40 for two of them.

    Im using a Taig ER20 spindle with a Parker brushless Servo motor and matching Parker 160volt driver. Only 10K RPM though.

    You don't really have to spend alot of money if you go the eBay route. You can end up with some very high end components for ridiculously cheap prices.

  3. #3
    Join Date
    Apr 2012
    Posts
    159

    Re: Designing CNC router for PCB milling

    I've been reading a lot of forum posts from people buying ball screws and linear rails on ebay. It seems all the THK and NSK stuff is fake, even if it's stamped with the manufacturer's logo. Apparently this is a pretty big counterfeit market. That said, people feel the quality they are getting is pretty good and it's a great value for the price. But it's a bit of a crap shoot, sometimes you get a dud. I think if you go the ebay route you should be prepared place an duplicate order if it doesn't work out the first time. I'm not sure how returns work with most of these guys; it seems returning something to China would be a pain. The chances of getting a dud appear to be on the low side though, most people seem pretty satisfied with their purchase. I don't know anything about getting servo motors or steppers on ebay. I suspect it's a similar situation. Since these prices are so cheap, it's still a good way to go. I do expect I'll be getting some, maybe all, of my stuff on ebay, but I won't be ready for purchasing for a while - I still have all the designing to do.

    Regarding the spindle, there are a couple ways to go. First is get an integrated using where the spindle and motor are one unit. Second, have the motor be separate then you can use a belt drive and increase the speed. This is how the Othermill works. I'm not sure what the issues are with a belt-pulley setup are at high speeds like 60k RPM. The Othermill doesn't go that fast, only 16.5k RPM. I'd prefer an integrated unit, but I'm open to either.
    "You can't teach stuff in a school that you would learn in real life unless the real life people are in charge of the school." - Gene Sherman

  4. #4
    Join Date
    Apr 2004
    Posts
    733

    Re: Designing CNC router for PCB milling

    Where did you read that there are fakes of THK and NSK? I've bought plenty of the stuff on eBay, if any of it is fake than it is a pretty darn good fake. The machining and tolerance to make a linear rail run smooth etc. is very high. I think it would be easy to spot. I know there are fakes of hiwin rails on eBay so I avoid them. Many have noted them to run very rough and with left over swarf inside the carriages.

    Having bought over 20 high end linear rails/ballscrews on eBay over the years, I'm fairly positive none of mine are fake. The machining and high quality is just to nice for any of them to be. They would all have to be fake then......and i would still be satisfied since they are perfect copies.

    Steppers are fairly cheap so I don't buy them on eBay. Mostly from Stepper Motor |CNC Router | Laser Machine | 3D Printers For Sale Stepper Motor | Stepper Motor Driver | CNC Router | Laser Machine | 3D Printers For Sale

    China made still. The ones I have do work pretty good. Plenty of members here have purchased Chinese made steppers. Very rarely have I seen a post of a bad one but it does happen. Again they are cheap so no sense of buying used on eBay

    Good servo motors are expensive so all of mine are eBay. Stick with known manufacturing brands. I test everything when it arrives. So far I have been lucky. I only been burned once on a bad motor drive. But it didn't cost me very much.

  5. #5
    Join Date
    Apr 2012
    Posts
    159

    Re: Designing CNC router for PCB milling

    Quote Originally Posted by jfong View Post
    Where did you read that there are fakes of THK and NSK? I've bought plenty of the stuff on eBay, if any of it is fake than it is a pretty darn good fake. The machining and tolerance to make a linear rail run smooth etc. is very high. I think it would be easy to spot. I know there are fakes of hiwin rails on eBay so I avoid them. Many have noted them to run very rough and with left over swarf inside the carriages.
    Mostly on forums like this one. Next time I come across some posts about it I'll send them to you. Are their specific ebay sellers you like to deal with?
    "You can't teach stuff in a school that you would learn in real life unless the real life people are in charge of the school." - Gene Sherman

  6. #6
    Join Date
    Apr 2004
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    733

    Designing CNC router for PCB milling

    Quote Originally Posted by scott216 View Post
    Mostly on forums like this one. Next time I come across some posts about it I'll send them to you. Are their specific ebay sellers you like to deal with?
    No specific sellers. I've bought so much linear components over the years. Very rarely from the same person.

    For my gantry CNC. I bought all the components even before I designed the CNC. I had a rough idea in my head but no exact size. Hard to order up a specific component on eBay., unless you buy new. Once I received my ballscrews and linear rails, that is what dictated the size of the machine.

  7. #7
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    Apr 2004
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    733

    Designing CNC router for PCB milling

    Quote Originally Posted by scott216 View Post

    Regarding the spindle, there are a couple ways to go. First is get an integrated using where the spindle and motor are one unit. Second, have the motor be separate then you can use a belt drive and increase the speed. This is how the Othermill works. I'm not sure what the issues are with a belt-pulley setup are at high speeds like 60k RPM. The Othermill doesn't go that fast, only 16.5k RPM. I'd prefer an integrated unit, but I'm open to either.

    Still up in the air on what kind of spindle I am going to use. I got the Taig with two pairs of pulleys for $80. If I find something better on eBay, I will buy it.

    We do have a t-tech quick circuit 5000 pcb engraving machine that was scrapped. We got it for free, the external driver box was missing. I changed it to servo drive and put a new spindle on it. Probably works better than the original. I gave it to my brother who still works in the electronics industry. It been a long time since I milled out a pcb. We send them out now.

  8. #8
    Join Date
    Aug 2012
    Posts
    3

    Re: Designing CNC router for PCB milling

    That depends on the materials you can get for your project. Since it is a DIY you can dictate on any parameter want. Both GMT and NSK linear rails can be used. There just used to guide and hold the circuit board. The size of the PCB board you are planning to use will also dictate the size of your rails.

    Regards,
    Dave J.
    Blog

  9. #9
    Join Date
    Apr 2012
    Posts
    159

    Re: Designing CNC router for PCB milling

    PCBs I'm milling will be 4x6 inches
    "You can't teach stuff in a school that you would learn in real life unless the real life people are in charge of the school." - Gene Sherman

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