Theres a lot of these out there on the net, with some major
disadvantages-too crappy, or too expensive, generally.
No reason why you couldn't do one of these, or adapt them for your own
However, I just picked up a book, "CNC Robotics, Build your own workshop
bot" by Geoff Williams. I've only skimmed it so far, but it seems to
cover everything about building your own gantry style CNC router. He
claims under $1,500.00, but he does use some salvage parts, and makes
his down PC boards, so you might have to spend more for those things
new. He seems to include everything, including the board layouts. But
But like I said, I've only skimmed it so far.
The book is $35.00 though, but if its as comprehensive as it looks, it'd
be worth it.
one other thing is that its a TAB book which means it'll probably be on
the market LONG after the chips and any other special pieces are
obsolete and no longer on the market. :)
Lots of good info here: http://www.cnczone.com /
This yahoo group: http://groups.yahoo.com/group/CAD_CAM_EDM_DRO /
A related links page:
I'm just starting on a small one of my design. Mainly for making parts
for rc planes, but some light woodworking also.
It's still hard and expensive to build CNC machines, because there are
still no cheap positioning devices. I'd start by looking at
industrial scrapyards and seeing if I could find some sort of
ready-built 2 axis robert. If it has stepper motors, then you can
make a drive for it.
Friend of mine has a Sherline mill, which they're using for CNC
jewellery. Damned expensive though.
Die Gotterspammerung - Junkmail of the Gods
There are now stepper motors that are commanded by RS-485 serial
communications ... the driver electronics are built into the motor. These
same motors are available with built-in encoders that can ensure that when
you tell the motor to step so many counts, that it actually does so. This
eliminates most of the problems with positioning. Size 34 frame, and the
largest has over 1000 inch/ounces of torque. Cost is about the same as a
bare stepper motor from Grainger or McMaster ($400-450 each). Following the
ShopBot design, you'll need 2 motors for X axis , one for Y axis and one for
Z axis. All the RS-485 comms lines daisy-chain from one motor to the next
... each motor is given it's own address (you can address up to 31 motors
with one RS-485 interface). Of course, you'll need a pretty hefty power
supply (72 volts, 4 amps) per motor, but again ... off the shelf.
There are a number of people selling used CNC machines ... a google search
as well as an E?A? search should get you on your way.
The PRT96 ShopBot is a rack and pinion driven system that uses home switches
to recalibrate should you need to. The ONLY time I've had to recalibrate is
when I've been manually readjusting the home position to accomodate material
flaws, or the one time I ran the traveling speed too fast and actually
skipped a step (changed to the correct router bit, and slowed the traveling
speed to a more appropriate speed corrected both of these issues).
With the rack and pinion, I've sufficient repeatability to stop a job,
restart from the beginning, and hit the same mark (within approximately
.005"). Slowing the travel speed down sufficiently allows me to use the
machine to engrave text as small as 14 point that rivels anything New Hermes
could do with their panograph engravers.
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