Homebrew PCBs

Hi David,

You're where I was sitting a few months ago.  If you look around you, I'm
not that far away...  :D

Ok, what I've gathered so far on the 'mostest easy' system for us schmucks:


- PIC control, if that's the MCU you are familiar with, as in my case, if
not, just about ANY MCU will do as long as it has PWM feature (pulse width
modulation, I think).

- stepper motors, unipolar or bipolar, I can't really comment on which is
better, I think bipolar is the 'newer' stuff.  For a drilling station,
unipolar is plenty strong and $5 a stepper here in Montreal.

- motion is determined by motor rotation, that's why they use steppers, they
turn in 'steps', or fixed increments, they are NOT like a conventional
motor.

- PC-side software like Mach 2 using parallel port to download movement,
free version with 1000 step limit.


And that's about it,  I'm going to use what I described above personally.
I'm buying Mach2 once budget permits, but I'm using the demo in the
meantime.

If you don't want to bother with making your controller, I suggest you check
out www.xylotex.com.  They have 3 and 4 axis controllers, as well as a DIY
4-axis unipolar circuit kit (I might get that for testing and learning).

There are MANY products out there, Gecko being about the Cadillac for the
DIY folks.  Steppers can get about as big as your pocketbook can afford,
same with the bells and whistles on the controllers.  Larger systems use a
main controller, and a driver circuit for each motor.  The nice thing about
the Xylo is that it is all on one board.  It is not as powerful, but I think
it suits our needs fine.

And most definitely a chicken before the egg scenario.

Robert
:)






-----Message d'origine-----
De : Homebrew_PCBs@yahoogroups.com [mailto:Homebrew_PCBs@yahoogroups.com] De
la part de David McNab
Envoyé : juin 11 2005 10:13
À : Homebrew_PCBs@yahoogroups.com
Objet : [Homebrew_PCBs] CNC drills/routers


Hi all,

Firstly, thanks to those who have helpfully responded to my earlier
questions with suggestions to use CNC drills/routers.

I'm forming ideas for the mechanics of a CNC transport:
 - PIC micro controlling the thing, talking to PC via serial
 - looting the x-y rotation counter bits from an old mouse
 - implementing the x-y board transport via PWM-controlled motors,
   driving threaded rods which have the mouse rotation counters attached

I could see this achieving a resolution of 0.25mm or better.

(Shame about the chicken/egg scenario - I'd love to have the CNC apparatus
already in place to help me manufacture the PIC logic board it depends on :P
)

Software on the PC side could then have basic primitives:
 - goto (x,y) - board movement
 - goto (z) - raise/lower drill or router
 - calibrate (x,y) - allow user to check/adjust calibration relative
   to a known 'origin' on board
 - turn drill/router on/off

Where I'm stuck is with the router - what kind of bit could I use to
guarantee good results and clean polished cuts?

And, any feedback on the above?

-- 
Cheers
David




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