Initial offering - functional pen plotter

A project log for PCB mill for under $10

pcb mill built from garbage using basic hand tools and little money

shlonkinshlonkin 03/04/2014 at 02:003 Comments

This plotter was actually a project from years ago and the details are documented on my blog here:

It's capable of fairly precise drawing. Certainly precise enough for a simple pcb. The z-axis, on the other hand, is just a dc motor that I pulse on for a few hundred ms. I may need more precise control for milling, so I might swap it for a similar dvd player part that uses a stepper motor. But I've been wondering, since I'm only working with one type of material with consistent thickness, and I'm only trying to mill off a very thin layer of copper, I really only need two z-axis positions: up and down. The up position doesn't even need to be precise at all. I could, perhaps, just set a tightly adjustable stop for the down position and run the tool down until it hits the stop. What do you think?

The next thought is the spindle and bit. I have a whole box full of DC motors from various junk. I picked out a 12V one that spins quickly with decent torque. I even had a little coupler, a sleeve with two set screws, that snugly fits the shaft and a 2mm drill bit. I tried it out by drilling some plastic. It works as long as I don't put a ton of pressure on it. Of course a drill bit is far too long and not designed for this sort of thing. I have an angle grinder and files. Could I chop the bit down to a short piece and carefully shape the end into about a 60 degree taper? I know the metal quality will be a significant factor, but it doesn't hurt to experiment with dollar store drill bits.

Oh, I had another idea. Rather than a milling bit, how about an abrasive "diamond" bit with a tiny ball end. I've seen those in the dollar store too. If I mounted it at an angle, it could grind away the copper. Hmm... It doesn't sound too precise, but it's an idea.


willbaden wrote 03/06/2014 at 00:11 point
The biggest problem with PCB milling is making sure the Z axis is at a consistent height throughout the entire board. If you have a wider angle of a cutting tool then the more change in the width of milled path when the z axis changes height.

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shlonkin wrote 03/09/2014 at 04:34 point
Whoa, I just realized there were comments along the side of the page. They should be more visible. Anyway, that's a good point. I'm thinking about the z-axis right now, so I'll have to keep that in mind. Thanks.

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willbaden wrote 03/06/2014 at 00:08 point
I had to machine some fiberglass material that ate up HSS and HQCS bits. We had to use carbide to prevent excessive tool wear. Granted it was for a higher production run.

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