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Author Topic: Spindle speed control  (Read 4167 times)

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Spindle speed control
« on: October 13, 2010, 11:14:33 PM »
This past weekend I decided to try the spindle calibration procedure...that was a mistake... Prior to doing this I could type in a spindle speed and use the slider to raise or lower the speed but after the calibration the spindle only goes full speed. If I re run the calibration it will start slow and speed up so some kind of control is possible but just not usable. Does the calibration change something in a file that I can either disable or fix?

Bill
Re: Spindle speed control
« Reply #1 on: October 14, 2010, 12:21:00 AM »
I was able to fix it - I deleted the linearity.dat file and pressed reset (not sure if that really did the trick but after my original post I continued to search the forum and found a post that mentioned deleting the linearity.dat file. A new one was created wihen I started Mach3. I ended up getting the speeds to correspond to the input by change the max speed on pulley 1. my spindle seems to get to 4500RPM (although it should go to 6000) and I used 11000 as the max RPM for pulley1. This gave me measured numbers pretty close to the set speeds. Now my question is why does the max speed have to be 2.44 times the actual max speed, what is causing this ...the ratio?  I think I changed it once and the measured speed did not change...but I'm getting a bit fuzzy...
Re: Spindle speed control
« Reply #2 on: October 14, 2010, 10:18:28 AM »
11000rpm a speed you say you cannot attain you say it should run at 6000

4500rpm the speed you say its running at

11000 divide by 4500 = 2.44
The Good Thing About Mach3, Is It's very Configurable

The Bad Thing About Mach3, Is It's Too Configurable
Re: Spindle speed control
« Reply #3 on: October 14, 2010, 11:12:34 AM »
What I meant was that to be able to get the speed to run close to the speed input I had to set the pulley max speed to 11000. For example I want the spindle to turn at 1200 RPM. When I use 11000 as the maximum pulley speed the actual motor speed is around 1200 when I tell it to go 1200. If I put the max pulley speed at 6000 an input of 1200 would have me running very close to around 3000 rpm.
Re: Spindle speed control
« Reply #4 on: October 14, 2010, 11:46:30 AM »
What figures have you got for the spindle motor on the motor tuning tab ?

The Good Thing About Mach3, Is It's very Configurable

The Bad Thing About Mach3, Is It's Too Configurable
Re: Spindle speed control
« Reply #5 on: October 14, 2010, 01:11:42 PM »
I would say that the numbers in that tab  haven't been changed - and probably should be . From memory the steps/per is set to 20000 and the velocity is set to 60. This is probably the area I need to investigate. I read that for a 3600 RPM motor 60 is a good number so for a 6000 RPM motor 100 seems to be the number. The one problem I need to address is why my 6000 RPM Motor is only going to 4500 RPM. Could this be contributing to the factor of 2.44 that requires me to put 11000 in the max pulley speed?

The one area of my mill that is more capabile  is the spindle. I am using a Control Techniques Spindle drive and probably need to tune there and within Mach3. For example the spindle drive can be set up to provide full torque at low speeds but I can stop the spindle by hand at 30 RPM
Re: Spindle speed control
« Reply #6 on: October 15, 2010, 04:13:46 AM »
I don't profess to know all the answers about speed control except that the pulley speeds should be set to what the machine is capable of achieving.

This includes the minimum speed so you don't lose torque and stall the motor when running.

The figures on the motor tuning control page are/can be completely made up is so far as they do not need to match the motor speed displayed in Mach3

What you need to do is enter figures in STEPS PER an VELOCITY that give 10v

Now if you are getting 10v to the VFD but are not getting the rated speed maybe the frequency is set wrong on the VFD

So in your case set the max speed pulley number one to 6000 min at 500, as 30rpm is way too low on a single speed machine.

Set the velocity to 60 x 2.4 = 144 and see if that gets you closer to the correct  figure if not adjust again but the best way is to measure the magic 10v

If you are using a Smooth Stepper then you may need to alter the pulse width on the spindle tab mine is set to 8.6 which is the only thing that i altered to get anywhere the correct figures the steps per and velocity made no difference This is on the Smooth Stepper config tab

Let us know how you get on
« Last Edit: October 15, 2010, 04:15:25 AM by M250cnc »
The Good Thing About Mach3, Is It's very Configurable

The Bad Thing About Mach3, Is It's Too Configurable

Offline thosj

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Re: Spindle speed control
« Reply #7 on: October 15, 2010, 07:22:31 AM »
Is this discussion about step/dir or PWM spindle control? Or are the settings being discussed applicable to both?
Re: Spindle speed control
« Reply #8 on: October 15, 2010, 08:15:48 AM »
Is this discussion about step/dir or PWM spindle control? Or are the settings being discussed applicable to both?

Good question, my answer relates to using step and direction as that was what the op mentioned

I have just read an excellent write up in the members docs (Very Under Used Part Of The Forum) and it explains the PWM mode

The author notes there are some bugs with Mach in that the commanded speed only works after a second commanded speed  ???

Step and dir works just fine for me using PP and SS ports and is a lot less complicated it has no bugs and is very simple and is very very accurate.

But maybe if it was explained as well as the PWM method i referred to earlier then everybody could do it.  ;D

This is using a C11G from http://www.cnc4pc.com SO IT CAN BE DONE  ;)
« Last Edit: October 15, 2010, 08:21:18 AM by M250cnc »
The Good Thing About Mach3, Is It's very Configurable

The Bad Thing About Mach3, Is It's Too Configurable