Robert Hedan wrote:
> Thanks Alan.
>
> I knew I could compensate for the total distance, that was figured out
> already. I thought a thou or two on the platform, two more on the gantry,
> another on the drilling rail and you ended up with one big sloppy machine.
>
Only precision needed is X and Y, taken care of in the rails and screw. Z is
critical in the alignment, so that the shaft of a drill travels precisely in
through the hole cut by the tip. Distance up and down is fairly non-critical.
Board being flat is fairly non-critical. A rail on either side of the board,
and make sure that they are precisely aligned. Couldn't care less what lies
between them as long as they are aligned, the rest of the machine rides on their
alignment, not what they rest on etc.
>
> I've read posts (somewhere) that had really made this application turn into
> a woodworker's nightmare. Maybe when I said I'd like to do mild CNC
> (plastic) didn't help. But I do need a drilling station and fast. Your
> comments are encouraging in that it is within the reach of an ordinary
> do-it-yourselfer to build this.
>
> Robert
> :)
>
I think people doing it in wood are nuts :). Or maybe just love woodworking.
I sort of figured why make a straight surface when you can go buy one,
probably about as cheap as the wood too. Plus for me drilling a hole and
putting a screw and nut through it about 100 times easier than making wood joints.
http://home.nc.rr.com/alan69/CNC/Board is the first hmm no second time I drilled a pattern, on a junk board.
Only etched that board because it was the first one to have enough transfer
pattern to etch and see. Next board was useable. I didn't know what I was
doing yet eye-balling it, so the upper right holes have a few misaligned. After
that it did ok, all off but that's me not the machine they're all about the same
off. I didn't bother much either it was just a test.
Controller is my own controller, MOSFETs and PIC and not much else. Works good
enough, have done a better layout since it needed a bit of improvement. New
layout can take 10 FETs per motor and run 5 phase too. Or just 8 or just 4,
depends on what you need to run.
Motor is a motor mount and coupler, total of about $5 including the motor,
coupler, and mount. Coupler has two set screws on the other side.
Whole is the whole thing. Really need to cap off the vertical rails, I cut them
off and they're sharp, usually keep a box over them. Hasn't been used much in a
while, the board is out of the clamp. Just clamp the board and PC board and go.
Does 1'x1'x2 or 3 inches, could make it more easily by mounting the side rails
up a bit and extending the Z axis. Only used 1 8' piece of aluminum angle, and
the inner 2 rails from 3 packs of the KV drawer slides. Note that they are
really the straightness, the angle is simply for 90 degree mounting and has two
holes in it the rail is screwed through.
Xaxis is the gantry. Easiest to access the board from the open end, so the side
rails become the Y. Motor is mounted in box with cutout for shaft, other end is
just a bearing mount.
Yrail is just the end of one of the rails.
Zaxis is two metal electrical boxes. Easier and fills more space so more
accurate, the rail would only go up 1 1/2". Boxes are all kinds of not square,
but board travel is the only thing that matters so they're just canted slightly
vs the X rails to bring the mounting board into square.
I could probably eliminate 90% of the play that is there, simply by canting
things just slightly to work the parts against each other. But never bothered,
it basically centers itself within the play, and with everything aligned right
there is very little force acting to push it out of line.
Alan