Again this is a plea for help! I posted before, but I need someone with a good understanding of computers and drivers for help. I have a Dyna 2800 running Mach3 with original motors and driver boards. I have tried all the motor tuning and pulse setting changes I can think of. Whenever the machine tries to round a circular cut right before and after the X and Y change over areas the motors growl and chatter, the machine jumps and I can actually see the X movement table jump back. It sounds like a grinding bearing, but I know it is not. I have increased the pulse time to 10 and turned off the tool path but little is gained if anything.  Mechanically this machine is great so I feel that maybe my computer is not up to the job and I am in the process of securing a faster one for it, but I may also need to change the driver boards and maybe even the motors. They are half step. Please does anyone have some suggestions for what will correct the problem, is it just the computer or do I need to order a new set of driver boards?

The second issue is; if I stop the circular cutting program before it is finished and tell it to “go to Zero” it runs off to a different spot and resets “0” maybe as much as an inch or more away from where Zero should be.

I have a second slightly lighter machine with different driver boards and motors running Mach3 in the lab at work and it works great. So I know how it performs when everything is correct.

Please help!!!!!!

Fred Fulmer

Fred, firstly I do not know the Dyna 2800, so if I type something stupid, just ignore it. I am going to attempt helping. Have you got backlash on any of the axis? I need to establish this before proceeding. Also check for loose ballscrew worm etc on any of the axis. It may sound irrelevant, but trust me, there is relevance.

Whacko

Fred - You have said a lot, but nothing. You have a computer running Mach3, and you have (I assume) connected the printer port of the computer to a milling machine, which, you say, has the original driver boards in it - running the original motors.

Are they motors stepper motors or servos with a feedback readout ??
I assume you have set up the steps per unit correctly. and also tackled the feedback on each axis - and got that as accurate as possible.

How does the machine perform on straight cuts - is it OK - is it accurate.

The problem with cutting circles is the direction of each axis changes twice in the circle, that means Mach3 has to stop all movement on both axis, take up the feedback on the axis that is changing, then start both axies again - and has to do this four times. To keep accuracy, it has to decelerate and accelerate each axis together. If you listen to Mach3 doing feedback, it certainly sounds different to ordinary running. The speed is different and the motor seems hesitant - but it certainly seems to put it on correctly - mine is to within 1 thou.

What I would do is try running without feedback and see what happens. Your circle will be out, but see if the noise and odd behavious is any different.

As far as the zeroing problem is concerned - I take it this a a software zero, not zeroing to swithes. If you are stopping before your program is finished, have you cancelled all offsets before sending the machine to what it thinks is zero???

I'm going with stalling motors. See if the gib are too tight, or if you have not enough voltage for the motors, or if the motors themselves are too small. Also, turn the aacceleration down a bit, that might help you out but still is not really the cure.
          DaveA.

Hello Whacko ; sorry but if it was a simple mechanical problem I would have sniffed it out long ago. I checked the screws motors and backlash first and this machine is solid.

Hello DaveA; No the tables slide smooth as silk, this machine has an automatic oiler and the ball lead screws are protected by full length bellows. Very solid little machine. The motors are Escap eight wire Swiss made disk stepper motors with 1.8 degree step (I believe they are rare earth magnets) about 3 1/2" Diameter and I would believe these are adequate for a 6" wide table with 10" travel.

Jimpinder; the motors areeight wire Escap (Swiss made) 1.8 degree angle disk type steppers. I can't see any torque spec's but they are a little over 3 1/2" in diameter.

The machine does fine on straight cuts. Went I set it up and tested it with Jo blocks it repeated perfectly.

Where do you turn off the feedback?

Other machines I run with Mach3 software will return to Zero from where ever they are but this one goes off somewhere else and resets a new zero position. The software I am using is the circle pocket from the wizards program that I bought with Mach3.

Fred Fulmer

You say "Disc stepper motors", if the torque isn't known, I am trying to imagine what these look like, and I don't think they are very powerful for what I know of them. Are they NEMA sized, or, what length are they?

Hello Jim

These are Swiss made Escap or Portescap motors. Here is what I have on them; the rotor is designed as a disc with rare earth magnets. This type has some advantages such as very low inertia and a optimized magnetic flow path with coupling between the two stator windings. These qualities are essential in some applications.

Like I said I couldn't find the torque for these motors, but from working with them I know they are defiantly strong. you won't turn them with your fingers.

Well, we still don't know what torque your motors are, other than that you can't turn them with your fingers, which isn't saying anything, and that we don't know what voltage you are feeding these motors with. in Jim's words, "Fred - You have said a lot, but nothing." Write back when you know both of these major details.

Can you post a picture of the cuts it is making with x and y +s and -s marked?

Brett