Machsupport Forum

Mach Discussion => General Mach Discussion => Topic started by: SWATH on November 13, 2013, 08:45:52 PM

Title: Spindle calibration problems
Post by: SWATH on November 13, 2013, 08:45:52 PM

I can't seem to get the spindle calibration function to work correctly.  When I start the spindle it starts fine but then when I click Autocal it immediately stops the spindle and says "Autocal terminated, spindle stopped".  Trying to do the autocal without the spindle running just asks me to start it at any speed.  I'm trying to get an accurate actual speed to commanded speed relationship but right now it is pretty far off.  For example, S200 gives me 300rpm, S1000 gives me 930rpm, S4000 gives me 5140rpm.  I've plotted the curve every 200rpm and it is not linear (especially around the base frequency of the motor at 1800rpm).

My spindle motor is an inverter duty AC motor with VFD.  I'm using a ethernet smoothstepper.  The motor also has an encoder that I have run the Z channel to the ESS to give me a 1ppr index pulse and this is working fine.  The displayed RPM in Mach is exactly the actual rpm confirmed with a laser tach.  The pulley is a 1:1 ratio and I would like to accurately go from 200rpm to 5000rpm.  Oh and the VFD frequency is controlled with a C41 card which converts the PWM to a 0-10v analog signal.

Can anyone walk me through the set up and procedure for this and tell me why it isn't working?  I've broken my brain trying to figure it out and am feeling a bit lost and burned out.

Thanks for the help.

Title: Re: Spindle calibration problems
Post by: slowtwitch on November 14, 2013, 06:02:11 AM

Hi Swath, The auto spindle calibration feature is somewhat suspect in Mach. You probably have to delete the linearity.dat file. Then read Peter Homann's post here.....

http://www.machsupport.com/forum/index.php/topic,23468.0.html (http://www.machsupport.com/forum/index.php/topic,23468.0.html)


pete

Title:
Post by: SWATH on November 15, 2013, 07:58:13 PM

Thanks Pete,
So Mach can't do it?
It's hard for me too accept that out of all to cool and complex things that Mach3 does, it can't control the speed of your Spindle.  That just seems like such an important and fundamental aspect of a cnc control program where virtually everything is based off Spindle speed.

So do I need to remember my Spindle speed "offset" at every rpm and program in bogus S numbers to get the correct rpm?

I guess I'm also perplexed why VFDs seem to base everything on frequency instead of rpm.  I've never programmed anything based on frequency, all I care about is rpm.

Sent from my SCH-I545 using Tapatalk

Title: Re: Spindle calibration problems
Post by: cncalex on November 16, 2013, 03:42:56 PM

Hi Swath,

in members docs you can find a helpful PDF file named   PWM SPINDLE CONTROL_CHRIS.pdf


http://www.machsupport.com/forum/index.php/topic,15457.0.html

hope that helps.

alex