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Spindle calibration setup
« on: February 21, 2010, 03:58:30 PM »
I am having problems getting my spindle calibrated i have it setup in mach and it runs with m3/m4/m5 commands but when i put in a value of say s1000 the actual spindle is running 1900 rpm. how can i get this running correctly. I was told that art posted how to manually enter the spindle curve as my setup is open loop right now. Please can someone shed some light on this problem.
Re: Spindle calibration setup
« Reply #1 on: February 21, 2010, 08:24:39 PM »
Come on somebody has to have an idea of how to get this working?

Offline RICH

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Re: Spindle calibration setup
« Reply #2 on: February 21, 2010, 10:01:02 PM »
I will call this reply the blind leading the one that can see.
The only spindle stuff i have done is using steppers on  my lathe............
Just something i found on the Yahoo group, FWIW, as it's almost a year old.....


RICH

--- In mach1mach2cnc@yahoogroups.com, Steve Blackmore <steve@...> wrote:
>
> On Mon, 09 Mar 2009 00:41:36 -0000, you wrote:
>
> >I am using the latest dev version, downloaded it a few days back. Its very
broken as far as I can see.
>
> Just a thought - There are a few tuning things that you need to do to
> get anywhere like an "as designed" speed response anyway.
>
> The following is taken from many emails testing with Art and assuming
> Mach is set for 25kHz (I've edited out some of the settings peculiar to
> my setup and the cursing ;)
>
> Before doing anything else, delete the linearity.dat file, Mach will
> create a new one.
>
> >Set 1000 steps / unit for the spindle, set the velocity slider 99% of the
> >way up, slide the accel slider so it reads .1 seconds when the first ramp is
> >straightening out on top. Save that. ( it shoudl be about 1000steps/unit,
> >vel 1450, accel 220 , .022G's.. )
> >
> > Set Pulley 1 for a max speed of 20,000 RPM, min speed of zero.
> >
> >Now command a M3S20000 .
> >
> >Let the spindle speed up and measure its actual RPM, ( from the screen or a
> >tach..whatever.. :) )
> >
> >Now enter that number in the pulley cfg as the max RPM, so it may be 1300RPM
> >or whatever.
> >
> >Now, when you command 1300, youll be getting close to 25Khz,
> >( this is (velocity/60)*accel = freq )
>
> Try the above - it won't do any harm and may improve things.
>
> BTW - restart Mach before testing.
>
> >The difference may be quite large between vfd's in how they react to
> >frequency and ramping.
>
> > Analysing it though, any vfd shoudl be tuned by sending it max frequency,
> >( hence the S20,000 test which will put out 25Khz) and then telling the
> >pulley max what the max frequency actually gives you.. hence the tach or rpm
> >reading at max. ). The code then takes a command like S600, and if the max
> >freq gives 1200RPM, then it seems reasonable that 12.5khz should give 600RPM
> >and thats what mach will do. Now spindle linearity is meant to correct for
> >small discrepancies between a 1:1 relationship and some non-linear responce,
> >but Im wondering if that 8Khz limitation is really making the vfd work too
> >hard at regulating.. Is there any literature on the VFD to say what
> >frequency range it expects or is it justa 0-5 volt analogue in the end?
>
> Explanation here - my VFD seems to max out at 8-10kHz or so!!
>
> > Now run a series of speed tests, say 100,200, 400, 600, 800..ect..
>
> From this we did find a problem peculiar to step/dir spindles that has
> been fixed in a pre-release version but we also know from this and other
> tests that the calibrator is definitely screwed, but the above should
> get you as close as you can get for now.
>
> What I have found so far is the calibrator does not wait (or wait long
> enough) for the spindle speed to settle before commanding the next speed
> step in the calibration sequence and it is on the list for a fix. As you
> can guess, this completely screws up the linearity file. It's
> particularly bad on some high inertia spindles that are slow to respond.
> The object of all of this is to get as linear response as possible,
> without calibration, on a wide a selection of VFD/spindles, then to fix
> calibration, finally to fine tweak PID so it doesn't have to work too
> hard.
>
> Steve Blackmore
> --
>
Re: Spindle calibration setup
« Reply #3 on: February 22, 2010, 08:36:04 AM »
Thanks Rich i have my steps per set at 2000 and my velocity set to 1350 accel is set at 400. Step and dir US is set at 4 this is the only way i can get the 0 to 10V needed for the spindle. I have tried different settings with out results when using the 1000 Steps per i get 7.8V max readout when running the motor. I have a bridgeport type clone and the variable drive pulley is set at 3300RPM and when i command M3 S1000 from Mach The spindle speed reads about 2000RPM and this is with my vfd reading 36.6hz. maybe i am doing something very wrong but this spindle calibration stuff is very complicated. Does anybody have any formulas for figuring this stuff out?