View Full Version : CNC question
09-13-2005, 11:16 AM
Hey guys, I'd like to learn a bit about cnc, maybe build a cutting table, or a small mill to carve foam patterns for casting.
I was looking at ebay last night and saw this:
Would I be able to use these driver boards with a mach2 or similar setup, or are they for some other industrial application?
Also seem to remember someone (ibewgypsie?) mentioning canibalizing old printers/plotters for their driver boards? Can anyone elaborate on this?
09-13-2005, 01:49 PM
you are jumbling together a couple of different technologies - that link is a dc motor and controller, disk drives controllers are for stepper motors.
you can use dc for cnc, but you need to affix encoders on the motors (or linear)to tell the controller where it is, steppers on the other just get told (via the controller) to move cw/ccw so many steps
its a fundemental design decision on what to use.
as far disk drive conrollers go, its possible to use them IF they are capable of handling your stepper motor (and you can hack them) - ie disk drives have small stepper motors and their controllers won't handle the power of something larger that you might need for a mill table axis. however there are open source stepper motor boards you can build
its difficult to adequately address your question without righting a book (not that I could write it, mind you) here are some links to some sites put up by very cool people who have done so to help guys like us
[This message has been edited by Mcgyver (edited 09-13-2005).]
09-13-2005, 02:11 PM
Start with the basics if you want to learn.
http://www.kleinbauer.com/ most the cnc projects here run with tip120 transistors and wave drive. A stepper with a transistor and coil for each "phase" of the stepper motor. A drive cost about $15..
www.geckodrive.com (http://www.geckodrive.com) download Mariss's whitepaper on stepper drives. Read all the tech manuals he has online.
HIS drives just blow away old technology in power and speed, but kinda pricy to start learning with. Blowing up a expensive drive can really put a damper on your learning process. Or at least it does mine.
Servo drives are better, but much harder to set up and tune to work.
FREE cnc software thou he suggests you register it www.dakeng.com (http://www.dakeng.com) turbocnc another good learning site, he has plans at his website on rebuilding the cheapie mini-mill from harbor freight.
COnfusious said: The longest journey begins with a single step.
Also while learning?
It's a big bad world out there, lots of people wanting to make a dollar off your/my ignorance in things. Start out cheap..
09-13-2005, 02:32 PM
David, have you checked out the following site for open source controllers? I'm building some of the controller boards and opto isolator now, I think its good stuff, no annoyance charge and Phil gets a kick out of helping people put trying to build his stuff.
09-13-2005, 03:01 PM
Using a flip=flop logic gate? I wonder why? 74hct was in the parallel controller (homebuilt plc) I built years ago. Or I have some brain cells not working..
Seems it was a 7400 nand gate you tied two logic signals to a output pin on the parallel port then out the backside to a tip120 transistor. it had some bias resistors on the board, but that was it.. not a whole lota parts.. You could perf build them easily. A parallel port sends out a high signal then pulls it low, using the nand gate inverted the output.
With a wave drive, you pulse the individual coils in sequence stepping the magnetic field around the armature, the magnets in the armature followed the moving fields.. hence stepping.. (over simplified but how it works) The Mighty bridgeport BOSS system worked like this too.. it has quite a few more parts than that tho.
Them old transitor boards are slow, but tough. Cheap to build and play with.