Machsupport Forum

Mach Discussion => General Mach Discussion => Topic started by: Rimmel on July 16, 2014, 05:26:57 PM

Title: Spindle speed crossover eliminating
Post by: Rimmel on July 16, 2014, 05:26:57 PM
Mach3 turn 062 .

I have the spindle setup on a spindle v4 card, all working good - however I have some speed crossover. E.g set the spindle at 300rpm and it will read 280, set to 1600 and it will read 1640, with a sweet spot of approx 800 rpm where s800 yields an actual speed of 800 rpm.

Is there any way or something I am missing to get the crossover lower or even eliminated?

Thanks
Rimmel
Title: Re: Spindle speed crossover eliminating
Post by: rcaffin on July 18, 2014, 05:43:05 AM
It sounds as though you don't have a sync signal coming back from the Lathe to mach, or maybe you just haven't enabled the sensing of it. Does threading work for you?

Cheers
Title: Re: Spindle speed crossover eliminating
Post by: mc on July 18, 2014, 01:19:07 PM
I think this depends on what motion controller you're using. I know with my old Smoothstepper setup that I just had to live with it, as there was no way to calibrate the spindle. I think even the Parallel Port spindle calibration doesn't actually do anything, so it's just a case of working around it.
Title: Re: Spindle speed crossover eliminating
Post by: rcaffin on July 18, 2014, 06:06:11 PM
Quote
I think this depends on what motion controller you're using. I know with my old Smoothstepper setup that I just had to live with it, as there was no way to calibrate the spindle. I think even the Parallel Port spindle calibration doesn't actually do anything, so it's just a case of working around it.
Strange. Mine seems reasonably well calibrated.
I repeat: do you have the sync signal operating?

Cheers
Title: Re: Spindle speed crossover eliminating
Post by: mc on July 18, 2014, 06:43:12 PM
I know my old setup was a step-dir to 0-10V converter controlling a KBIC board, and given it was done via a SmoothStepper, Mach itself couldn't close the loop, and the SS plugin never had any sort of calibration.
The only area I noticed a major variation was below around 500rpm, as the spindle would struggle to start at anything below 100rpm requested, and would spin around 80rpm if requested to do 200rpm getting to about 50rpm difference at 500rpm, before being within 20rpm for the rest of the range from around 700rpm up. I never worried about it, as the speed was very repeatable so I just altered commanded speeds in my code files to suit.

Anytime you add open loop analogue into the circuit, you have potential for variation.

My new lathe has a KFlop which closes the loop perfectly, however that's a far more capable controller than the PP or SS.
Title: Re: Spindle speed crossover eliminating
Post by: Rimmel on July 25, 2014, 06:33:25 AM
It sounds as though you don't have a sync signal coming back from the Lathe to mach, or maybe you just haven't enabled the sensing of it. Does threading work for you?

Cheers

That sort of doesn't make sense to me, if i didn't have the signal coming back from the lathe then I wouldn't know the actual rpm at all.
Title: Re: Spindle speed crossover eliminating
Post by: Rimmel on July 25, 2014, 06:41:50 AM
Sorry been in Majorca for a week with the family. Boy it was hot! 35c in the shade one day!

I am using a spindle V4 board and it does exactly the same with the parallel port, a UC100 and a ESS (ethernet SS).



Title: Re: Spindle speed crossover eliminating
Post by: cncalex on July 25, 2014, 12:46:29 PM
I do not know exactly but I think the glitch lies in  the last mach3 versions when using G96.
I have seen this in the past. ( PWM controlled spindle USB SS ) Try using G97.
Alex
Title: Re: Spindle speed crossover eliminating
Post by: Rimmel on July 25, 2014, 01:07:54 PM
Will do  - thanks