Re: Digest Number 12

Jon wrote:

> A dedicated
> card (currently ISA) with quadrature encoder counters and servo DACs
> interfaces to the motion hardware.

Who makes this card? Is this the 'servo2go' card I have heard mentioned
on this list?

> I don't know what jerk control is - do you mean backlash compensation?

Jerk control is limiting the rate of change of acceleration. I was not
thinking of the right thing when I wrote that as jerk control is part of
the feedback loop (you feedback 3rd derivative of delta position), not
feed forward. Actually, it sounds like the EMC control system needs
some work if the PID filter is not working and you are using feed
forward to compensate (feed forward is an open loop compensator).



Don wrote:

>
> I would like to know if some of you kind folk would take a moment out of
> a busy period and do something for me, and maybe some of the newer
> members here that are still in the huge learning curve such as myself.
>
> I would like to know briefly what the majority of members here have for
> their setups. Please take me from the PC(including all hardware and
> software) all the way to the cutting head. This is just to be ensure
> that I have the grasp that I feel I am starting to get up to this point.
>
> I hope this is not being too demanding of the members.
>

I have a completely homemade 3 axis CNC mill/router I originally built
it as a senior project in college (I decided to build it after reading
an article on home built CNC machines in Nuts and Volts authored by Dan
Mauch). The travel is 2' x 2' x 8" X,Y,Z, respectively. I have several
controllers for it. The one I use most is an SGS Thomson L297 & L298
stepper chopper drive. I used to use one of Dan Mauch's chopper boards,
but I accidentally blew it up when the control lines got cut on a sharp
piece of metal (hate it when that happens). Since then I built up a new
controller with basically the same design. I am currently working on a
closed loop servo controller that reads step and direction bits and
drives brush DC motors. I use Dancam, MaxNC and most recently DeskNC
to read NC code. To generate NC code, most of the time I create 3d
bodies in Solidworks and use either Mastercam or Virtual Gibbs to post
to a file.

I am the type who would rather redesign and rebuild a machine than use
it. Hence most of the time my CNC is in pieces all over my garage.
Given I now work at a robotics company, much of my fascination with CNC
machines has been lost as I now have to work on them for a living. But
I have been in the mood to build a new machine lately, and have enough
scrap precision parts to do it.

If you are interested, you can see my machine at
http://members.home.com/mromine. The web server for my project page is
on my computer which is not always on, hence you may have to try a few
times before you can reach it.

Mike Romine