Homebuilt CNC Router?

[shovelhead]

anybody built one or know of plans for one?

[John Thompson]

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 needs though.

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. :)

John

[Mark Hopkins]

[Phil]

Lots of good info here:

This yahoo group: related links page: 'm just starting on a small one of my design. Mainly for making parts for rc planes, but some light woodworking also.

Phil

shovelhead wrote:

[Andy Dingley]

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

[Clint Neufeld]

Is there a reason why guys named Robert are better at this than guys named Phil? Or Sam? Kind of a demeaning life, too, I'd guess, standing around my shop, waiting to route things for me...

Clint

[Tom]

[Rick]

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.

HTH,

Rick

[George]

Good point on the book (re: parts availability)...so, what IS the copyright date of it?