Try the driver test are varying kernels to see how it looks, you may get a lot more than 25KHz.
Presume you are geared 2:1 mechanically with a 5mm pitch ballscrew? What size/make of lathe is it?
Hood

Hi Hood

Firstly many thanks for your help - I can see how much expertise you contribute to this forum.

You are almost right (and I got my maths wrong) mechanical gearing by toothed belts is 4:1. The lathe is a Harrison M250 professionally converted to CNC from new by Anilam for a college. I discovered that the anilam electronics and coolant did not mix well.....there is a snapped off boring bar in the roof of my shed just to prove it!

Ha ha, yes lathes can be dangerous, first time I tried CSS for facing a 19 inch dia hauler plate I forgot to limit the rpm and it got a bit frightening as it started spinning upwards of 1000rpm

Hood

You know Hood I wish you were closer you may not as I could knock on your door and ask another stupid question each day lol I'm in Hull east ridding.

Small world, my Computurn 290 lathe came from Hull Uni.
Hood

wow that is a small world. I have to go to cardiff for mine lol

Hi Guys,

I was searching the forum and found this topic. Did you ever make any progress? I am having the same issue with the same setup- two DC Servos running off one Granite DualDC drive. And the same results- never loses position during straight moves, but arcs will throw it off every time. A lot. Diagonal moves also seem to cause trouble, though not as severe.

Any ideas? I was thinking I may be better off going to separate drives.

Thanks,

Kevin

Hi

Well I found the answer and it was using the multiplier in the servo drive. Once I set that to a multiplier of 1 I get 100% accuracy. The only difficulty that gave me was that I needed to increase the kernal speed in Mach3 to get decent rapids... in the end I changed my computer for a more modern one and all works very well. I still keep my rapids to less than 1M/m just to (hopefully) avoid big crashes.

Other than that the Granite servo driver seem superb - I have not even opened the enclosure in 9 months.

Quite a lot of drives have these issues when using electronic gearing, thats why I suggested trying 1:1, the more Industrial ones seem fine but its not something I like using.
Hood

I checked and my step multiplier was already set to 1. One other thing I tried was setting the X and Z axes accel and velocity to the same settings. That actually helped quite a bit, but I'm still losing position about .005" during a 1/32" radius corner round. As I said before straight line moves in both X and Z come out perfect every time.

Kevin