Machsupport Forum
Mach Discussion => General Mach Discussion => Topic started by: jaja on August 22, 2010, 02:44:11 PM
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Situation: disk with one reflecting part and an opto sensor.
It gives a nice stable RPM DRO.
But when I let the machine rotate under 38 RPM, the S-true DRO shows wrong numbers in a random way (like 1546 rpm).
Does someone know how to solve this problem and make it possible to measure under 38 rpm????
gr jaja
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jaja,
That was fixed in version 3.042.032, .033 or so. You are required to turn the spindle on with a M3/4 and that also tells Mach to start looking for
the index so low rpm's would show. Did you try a different / lower Index Debounce setting?
RICH
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Rich,
Thanks for your fast reply.
Just went to the lathe and tried your ideas.
Changing the width of the reflecting surface and changing the debounce interval and index debounce did not make any difference.
The lowest S-TRUE I can get is 37. Lower is not possible.
What more could I try???
gr jaja
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You may try unchecking spindle speed averaging and see what happens. I always have that on and may not make any difference
anyway if not threading. I just tried turning the spindle by hand and my DRO was reading down to 3 rpm ( kind of hard to get constant turning by hand).
My index debounce is set at 10, can go lower but works fine there for me.
Don't know what else to suggest.
RICH
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Rich,
I tried all you suggestions but no results.
Changed the kernel from 100kHz to 25000Hz,,, no result.
The input signal from the optosensor is nice and straight, so it seems to me that it is something in mach that's working not good.
Still the lowest RPM i get is 37. Higher is no problem at all.
If I go lower Ill get much higher numbers, who are by the way stable.
So it changes from 37 to something like182 or something like that.
I'm running out of ideas, do you have some left?
gr jaja
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As a test to see if Mach is screwing things up go to Ports and Pins, Inputs and choose to emulate the spindle and then choose a keyboard key, maybe 5 as I dont think that will be used for anything else.
You will need to disable your spindle drive if you can then press the spindle button in Mach. Next press the 5 key (or whatever you used) once every 10 seconds, the RPM should read 6.
Hood
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Not realy jaja.
Maybe somone else will chime in here.
RICH
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Hood,
I'll get the idea, but in ports and pins, input signals,, which signal stands for the spindle? Do you mean the "index"?
gr jaja
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Yes sorry, emulate the Index.
Hood
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Hallo Hood,
First I tried you idea and emulated the index input. But no result.
Later, with some help, I found out that the "spindle pulley configuration" probably messed things up. Changed some things, and now for the first time, mach tries to match the S- true with the demanded speed. Great, never got this far!
The minimum measured RPM is now under 38 RPM. Was this also caused by the pulley settings?
There are still a lot of things that must be configured.
Right now I'm trying to figure out how the P I D is optimised.
And how must the spindle pulley's be configured in the best way. Pulley number four is the standard pulley?? And what are the numbers that must be entered there? The minimum and maximum spindle speed?
Are the ratio's of the other pulley's to be measured very exactly, or is it not stringent?
Thanks for your help, without it I would never got this far
gr jaja
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jaja
afraid I am unable to advise about the PID as I have never used a VFD spindle in Mach.
Pulleys however should be easy enough. If you only have one physical pulley then just set up Pulley 1 with the Max speed of the spindle. You can change the Pulley number on the Settings page by typing directly into the DRO, so set that to 1.
Hood
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Thanks Hood,
There are six pulley's. But the problem at this moment is that there is no correct RPM number at all. The number is much higher than it should be. And Mach is totally not reacting the way it is supposed to be. It never reaches the RPM which is asked for.
I just came out of the workshop, tried all kind of settings for a long time, but it just doesn't work.
There must be something wrong at the basis I think
How does the "calibrate spindle" work?
There is on thing on this screen that has a wrong setting. In the middle of the calibrate screen it says: "Pulses per revolution, Zero if 1 per rev".
I've got one pulse per revolution, since I have one reflecting slot, but the number in the screen is 1, and not 0.
Does this mean I did something wrong? You cannot change the 1 into a 0.
In the "calibrate spindle" screen you can enter a number under control. What is the meaning of this? Is it possible to measure the real RPM's with a device and enter this number there?
gr jaja
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I am afraid I cant help with that as I have only ever had Servo spindles under Mach control. I am sure someone who has used and set up a VFD control spindle will jump in and help.
Hood
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Thanks
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Have a look at the link below and see if it helps you out ( i have never fooled with the spindle calibration).
http://www.machsupport.com/forum/index.php/topic,14223.msg94223.html#msg94223
RICH
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Thanks a lot Rich,
This is about a servo spindle motor I think, but there is a lot of information I can use.
I start trying right now.
gr jaja