Re: VEX CNC

> Posted by: "Chuck Merja" chuckm@... ebiz_59
> Date: Thu Sep 11, 2008 7:46 am ((PDT))
>
> Thanks for the comments. It looks like I am trying to fit a round peg in a
> square hole, maybe?? I'm interested in VEX stuff because we have it and we
> have a little expertise in programming it. The controller has a Microchip
> PICmicroR PIC18F8520 and uses PIC C, and we use EasyC to do the programming.
>
>
> Am I getting from you that the controller and C might not fit CNC use? I
> didn't see a way to interpret shapes, especially without a fair amount of
> programming, which isn't the goal. The goal was to find yet another use for
> use the VEX platforms we have (or understand why they aren't the best fit) -
> I just added the part in parentheses, cuz that looks to be where we are
> headed:o))
>

VEX would be an excellent choice for making something like a pen
plotter. The controller with it is more than capable of the job, much
more so than a PicAXE chip.

I think the issue is that a servo, the kind in VEX kits, are not very
accurate for position control. They have a short arm that only operates
over less than 180 degrees. They are also essentially analog devices, as
they are controlled by a pulse width.

A couple small steppers, even those salvaged out of old floppy drives
should work fine, and should be easy to interface to the VEX controller.

It will be a programming project. The mechanics are nearly trivial,
programming it will be the trick. To draw circle you need to look up
Bresenhams algorithm. It converts the circle into a series of short X
and Y steps.

ron ginger