RE: Low cost Servo Controller

Dan (Falck), It seems as though you have a fair amount of experience in the area I am exploring. Others may also have this kind of experience as well. You have run CNC without ballscrews. You said you tried this and upgraded to ballscrews after running without them for a few months. Aside from the cutter sucking the table out of position, as it can in manual milling, was a major part of the NO FUN aspect of working with the backlash, the fact that you had to program in a manner to adjust for it. That is, before changing directions, add steps to the program just to deal with the backlash? Was that less fun than what you had to do to keep the cutters from sucking the work into themselves? Your third experience of loosing steps I suppose meant that you had to reduce the feed rates to reduce the torque required from the stepper motors? Did you experience the steppers loosing steps because of fast table moves, such as Home, jog or power supply overloads?

If you had more speed and no lost steps, in your case, how important and how expensive is the ballscrew? Was the aspect of the cutter sucking into the work a major or a minor issue in the attention required to work around that problem?

When Fred got EMC up for steppers, did you bring up EMC for your shop? If not, what operating system do you run and what software and hardware do you run in your shop? When you move into servo systems, what cost effective options sound good to you? What does it take to make that transistion?

Thanks for your help.

David Howland



-----Original Message-----
From: Dan Falck [SMTP:dfalck@...]
Sent: Monday, September 13, 1999 7:01 PM
To: CAD_CAM_EDM_DRO@onelist.com
Subject: RE: [CAD_CAM_EDM_DRO] Low cost Servo Controller

From: Dan Falck <dfalck@...>



David,

EMC will run either servos or steppers. Jon and Matt can give you the
details on the servos, because it was written for servos in the first place
and I believe they were the original beta testers on it. The rest of us,
who run stepper systems currently, bugged the crap out of Fred Proctor to
make it run steppers too. He did and now he has several dozen beta
testers. I have been running steppers for several years now and want to
move on to servos. My side business is picking up and I need the speed.

Running a CNC without ballscrews can be done- but you have to be careful.
I did it for a couple of months, right after setting up the mill, but
switched to ballscrews ASAP. Pulling the table around with .030" backlash
was no fun. It was just like machining by hand, except I had to really
watch it because the cutter could pull the workpiece into itself. Couple
that with losing some steps and you're in real trouble.

Dan Mauch and Bill Wainwright are running a hybrid step & direction/ servo
motor system and Dan is able to get 130 ipm rapids on a mill/drill. That
seems pretty good to me for a system that all together costs around $1200.
He's running Clifton Precision motors from "The Surplus Center" of Nebraska
($20 ea) and using Maxnc as the control software on a 486 DX/66.
I agree that the STG card is really the ultimate way to go, but I want to
set up multiple machines in my shop and don't want to spend $800 for each
PC control- right now. Maybe later. Of course, maybe Dan and Bill will
come up with their own control card by then too.

Dan Falck


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