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Author Topic: Still being driven mad by arcs  (Read 7695 times)

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Offline Hood

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Re: Still being driven mad by arcs
« Reply #10 on: October 11, 2010, 08:03:55 AM »
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
Re: Still being driven mad by arcs
« Reply #11 on: October 11, 2010, 08:10:36 AM »
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!

Offline Hood

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Re: Still being driven mad by arcs
« Reply #12 on: October 11, 2010, 08:13:19 AM »
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

Offline Kai

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Re: Still being driven mad by arcs
« Reply #13 on: October 14, 2010, 11:56:54 AM »
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.

Offline Hood

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Re: Still being driven mad by arcs
« Reply #14 on: October 14, 2010, 02:03:24 PM »
Small world, my Computurn 290 lathe came from Hull Uni.
Hood

Offline Kai

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Re: Still being driven mad by arcs
« Reply #15 on: October 14, 2010, 02:26:28 PM »
wow that is a small world. I have to go to cardiff for mine lol
Re: Still being driven mad by arcs
« Reply #16 on: December 29, 2011, 07:32:09 PM »
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
Re: Still being driven mad by arcs
« Reply #17 on: December 30, 2011, 04:26:48 AM »
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.

Offline Hood

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Re: Still being driven mad by arcs
« Reply #18 on: December 30, 2011, 07:10:09 AM »
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
Re: Still being driven mad by arcs
« Reply #19 on: December 31, 2011, 12:52:50 PM »
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