Small CNC machine for drilling PCBs

[Robotics Guy]

I'm going to build a small CNC machine to drill the PCBs I'm planning on making. I'm sure as I start building this that I'll have more questions, but right now I just have one.

For a *very* small low speed, low torque CNC machine what would be better:

1) Small DC motors with shaft encoders on them
or
2) Stepper motors

Thanks for the advice!

[BobF]

Steppers are easier to implement for DIY. They give no feedback, which is not near as big a deal as it may seem. There are many machines here that use steppers.

[analogman]

When I was looking at PCB milling, the fireball V90 sure had my eye.

http://www.fireballcnc.com/machines-...terceptor.html


Have you seen the site:

http://pminmo.com/millingpcbs/milledpcb.htm

[Drools]

I started into this the exact same way, needing a something to drill and mill PCBs. I started reading and reading and....
Finially I decided if I'm in for a penny I might be in for a pound and make something I can do larger wood engraving with. I'm making a 2'x3' router which eventually I hope will be able to make the pieces for a smaller 12"x12" PCB mill. I think steppers should be just fine for what you have in mind.
You might find this link interesting.
http://hi.baidu.com/niejh/blog/item/...6562c84a0.html

Brent

[Robotics Guy]

Thanks for the links, I hadn't seen those websites.

I'm actually not planning on using this as a router at all. Essentially I just want an automated drill

I'm thinking about using some cheap NEMA 23 steppers, and I bought some super-cheap threaded rod yesterday at the hardware and I think it will actually work really well.

[DarrenV]

Hello Robotics Guy,

I have been working on a 4-axis controller for a pick and place machine. One of my design requirements was a simple drill for test fixtures, which is very close to your needs. The controller is 50v 3.5a per phase with USB or Parallel Port interface. I really wasn't designing this to sell, but I couldn't find any cheap alternatives so I had to design my own.

I was designing it for Nema 23 steppers, running open loop. I don't think the torque requirements for your drill would cause a Nema 23 stepper to lose steps.

The USB software isn't done yet(I can control the motors from software, but I don't have a parser for the drill or part files yet). But I brought out the step/direction signals to a header for Parallel Port control so others would be able to use existing software.

Anyway, since I assume if your drilling PCBs you must have at least a fundamental knowledge of electronics I would be happy to share my design with you, or if you want, I can sell you a finished version at cost ($40-$60), I haven't looked at the BOM costs in a while so I am not sure what my cost is.

Let me know if your interested in the design files
Darren Vandervort
darren@opencapitalist.org

[Robotics Guy]

Thanks for the offer Darren, but a big part of this project for me is the learning experience, so I think I'd prefer to make the electronics board myself.

I do appreciate the offer though.

[Robotics Guy]

I'm still trying to figure out the best way to build the X and Y axis. I need to use cheap materials, and so far these are the only two ways that I've been able to find:


Using steel rods:





http://www.engadget.com/2006/07/04/h...achine-part-2/


And,

Using aluminum U channels:




http://www.instructables.com/id/Easy...hine/?ALLSTEPS


It sure seems like both of those designs are going cause a lot of friction, and maybe binding, though. Any ideas on a better - but still cheap - way to do this?

[jalessi]

Robotics Guy,

These are very inexpensive.

http://tinyurl.com/kllb2v

Jeff...

[Robotics Guy]

Thanks for the link, but I'm not sure that those will be sturdy enough. All of the drawer slides I've seen also wiggle around a lot, which would be disastrous for a CNC machine :-)

[kvcummins]

Have you thought about using bearings on aluminum angle riding on aluminum angle?

[Robotics Guy]

Interesting.. That might work really well!