Author Topic: Spindle calibration setup  (Read 3295 times)

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Offline native34

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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.

Offline native34

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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
> --
>

Offline native34

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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?