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Author Topic: Spindle calibration, how I manage to get it working  (Read 10545 times)

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Offline rcaffin

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Re: Spindle calibration, how I manage to get it working
« Reply #20 on: August 24, 2016, 05:55:11 PM »
Ah so!   :-*
What an excellent idea. I must try that out myself.
Thank you.
Roger
Re: Spindle calibration, how I manage to get it working
« Reply #21 on: September 20, 2016, 06:43:41 PM »
Yet another update:
Spindle calibration works fine in MILL mode.
I am still having a few issues in LATHE mode. I usually have to issue a spin command twice to get close to the calibrated spin, otherwise it runs faster - sometimes a little faster, sometimes a lot. Sigh.

The comment was made somewhere that there is little difference between spinning at 1500 RPM and 1600 RPM. This may be so on a Mill, but on a Lathe it can mean the difference between sitting right on tool/part resonance and being way off resonance and quiet. Mumble.

Cheers And Happy New Year
Roger


The spreadsheet is excellent and has done a great job of calibrating my lathe spindle speed. I have the same issue that you have regarding having to request the spindle speed twice. Did you ever find a fix for this?

Thanks davidimurray, good to know the spreadsheet was useful to someone!
Sorry I haven't been checking this post for a while...
You know, this need of  setting-speed-twice have been annoying me too. Sure it is not the best way to use workarounds, but the info you guys posted really helped me to make it work!
Cheers!
Re: Spindle calibration, how I manage to get it working
« Reply #22 on: November 11, 2016, 06:33:54 AM »
Thanks resalles for the script.

I got Spindle calibration to work with your script.

Here are the step i took to get it to work.
1. I set the pulley to 1, min to 0, max to 1000.
2. turn on the spindle, set speed from S0 till the spindle start to move. note the speed (mine is about 110 to 120 RPM)
3. Max out the motor speed by type S1000 into the MDI, speed was about 12928
4. change the min spped to 120 and max to 12928 ( I think can set to 12500 or anything max speed toy like)
5. key in the min and max in the spreadsheet
6. Type the speed from from the spreadsheet and key in the measured speed, repeat 100 times.
7. generate the Linearity.dat file.

it works within 200rpm + -
Re: Spindle calibration, how I manage to get it working
« Reply #23 on: March 17, 2017, 09:54:54 PM »
Thanks resalles for the script.

I got Spindle calibration to work with your script.

Here are the step i took to get it to work.
1. I set the pulley to 1, min to 0, max to 1000.
2. turn on the spindle, set speed from S0 till the spindle start to move. note the speed (mine is about 110 to 120 RPM)
3. Max out the motor speed by type S1000 into the MDI, speed was about 12928
4. change the min spped to 120 and max to 12928 ( I think can set to 12500 or anything max speed toy like)
5. key in the min and max in the spreadsheet
6. Type the speed from from the spreadsheet and key in the measured speed, repeat 100 times.
7. generate the Linearity.dat file.

it works within 200rpm + -

Thank you very much!
Spindle calibration, how I manage to get it working
« Reply #24 on: March 22, 2017, 05:02:00 AM »
I have a 3 axix CNC converted Conquest mill (from Chester UK) controlled by Mach3/Geckodrive G540 and recently got quite happy to make it work with the VFD (RPM controlled by Mach3).

For that I simply disconnected the potentiometer from the mill speed control  and replaced it by an analog optocoupler and a resistor. I know G540  VFD is already isolated, but the mill circuit board was powering the low voltage electronics directly from the 220V using a voltage divider... so it got me scared to simply plug the G540 directly.

The advantage of this approach is that I got a working VFD almost for free. The disavantage is that it is highly non-linear. The spindle only starts to turn at about 30 RPM when I command 400 RPM, it  gets close to the commanded value at about a 1000RPM then it undershoots.

So I thought "Lets use the Mach3 spindle calibration and it will work fine"... Well, wrong... for some reason the calibration, at least in my version of Mach3 would not work. Probably it works for correcting small deviations but for my cheapo VFD it was hopeless...

So I read some threads here about this problem and it seems somewhat usual. People referred to a file named "Linearity.dat" so I could not resist taking a look at it.

Long story short, the linearization strategy implemented in Mach3 is actually works great. The problem seems to be the function that generates the file, it probably does not assume that a VFD could be as bad as mine  :D.

So I wrote an Excel table that takes as input the commanded RPM vc Real RPM and produces a  "Linearity.dat" file that works fine.

I am attaching the Excel file so that you guys can try it out. CanĀ“t guarantee anything but that it worked for me. But if some of you have the same issue, I hope it helps.

The way it works is the following:

1- Only make changes to the GREEN cells.
2- Enter your min and max RPM. It will generate a list with 101 input values for you to fill.
3- For each entry, command your machine to spin at the COMMANDED column (blue), take note of the real RPM it is spinning and enter it in the MEASURED column (green)
4- Click the CREATE FILE button. It will run a macro that writes a linearization file. That is the  "Linearity.dat" file that Mach3 is able to read.
5- Shut down Mach3 and copy that file as to replace the one you have. In my case it happens to be at "C:\Mach3\macros\Mill_RS".
6- Start Mach3 and try to see if the RPM is correct now.

Hope it helps.


 
Could someone send me a copy of VB macro in this spreadsheet?  The one used to create the .dat file. Everytime I download the spreadsheet excel tells me macro is corrupt and deletes it.

Thanks,
Kelvin

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