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Author Topic: Spindle Speed Jumping on Axis Rapid Movement  (Read 3157 times)

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Offline tjhj

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Spindle Speed Jumping on Axis Rapid Movement
« on: January 10, 2010, 04:19:15 PM »
Hello All,
This is happening on both my X3 mill, and 7x14 Lathe that are CNC. They are both hooked to the same computer, So only one runs at a time.
Simply when an Axis makes a full speed rapid, the displayed speed in mach 3 jumps up to around 6-8k plus. No matter what the current spindle speed is set at. Then returns to normal once the rapid is done.

Details.
Mill - Using an adjustable opto reflector sensor looking at a sanded and black line on the spindle pulley. Happens on any axis rapid movement.
Lathe - Using an opto interrupter style sensor looking at a missing tooth type wheel for its pulse. Happens only on the X axis.
The mill and lathe are on different parallel ports. Mill - On the mother board, Lathe - PCI board.
I am using shielded cable on all the sensors.
The pull up voltage is being supplied from the PC via USB for 5v.
My motor drives are enclosed separately using a xylotec 4 axis box for the mill, and probotix side step drivers for the lathe. Both use a common 24v supply.
Index De-bounce Lathe - 20 Mill - 10 I have tried all the way up to 50 on both with no change.
The mill spindle is speed controlled via cnc4pc's C6 - Variable Speed Control Board normally. I tested this with just manual control hooked up no change.

Notes,
I am using the most recent version of Mach 3. (Just downloaded and installed before coming here. )
Spindle Speed Averaging is turned on.

This has not been an issue that has affected anything I have done until now, but doing more threading work on my lathe, sometimes mid macro it will randomly change its Feed/rev rate. Consistent to the run, but no pattern as far as I can tell. Per example, two runs of 7/8 32tpi. The code did not change, just hit start again.
27 passes 3 spring passes
Run 1 results.
Pass 1-10 - Feed Ok @ .03 in/rev
Pass 11 - Feed changed to .06
Pass 12-14 - Feed .03
Pass 15 - Feed .06
Pass 16-30 - Feed .03

Run 2 Results
Pass 1-7 - Feed Ok @ .03 in/rev
Pass 8 - Feed changed to .02
Pass 9-20 - Feed .03
Pass 21 - Feed .02
Pass 21-24 - Feed .03
Pass 24 - Feed .02
Pass 25-30 - Feed .03

Any help, advice, suggestions or ideas would be greatly appreciated.

Thank you for your time,
TJ

Edit : Note the Turn Diagnostics plugin does not seem to show this as a variation.

« Last Edit: January 10, 2010, 04:22:57 PM by tjhj »

Offline Hood

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Re: Spindle Speed Jumping on Axis Rapid Movement
« Reply #1 on: January 10, 2010, 05:14:41 PM »
I dont think Turn diagnostics works with the last few drivers, think Art has written another which will be included wit the next revision.
 Have you always had this problem or is it just since you installed the latest version?

Hood

Offline tjhj

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Re: Spindle Speed Jumping on Axis Rapid Movement
« Reply #2 on: January 10, 2010, 06:44:31 PM »
Thanks hood,
I have always had this problem but I have only been using Mach about a year now. Ive had the mill spindle sensor installed about 9 months now, and the lathe about 2. So I am not sure where in the version set I started.

TJ

Offline Hood

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Re: Spindle Speed Jumping on Axis Rapid Movement
« Reply #3 on: January 10, 2010, 06:50:53 PM »
Afraid I have never had a VFD conbtrolled spindle so cant help wit the setup of that, just wondering however if your CPU is pegged at 100% when things like this happen?
Hood

Offline tjhj

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Re: Spindle Speed Jumping on Axis Rapid Movement
« Reply #4 on: January 11, 2010, 06:06:18 PM »
Hood,

Just a note, I thought I might be getting back feed from the stepper drivers, through the PC-VFD board since its on the same power supply, but disconnected it still happens.

As for CPU processing, running a program it floats around 50-55%, and I see no spikes during rapid movement. At idle it is around 12-14% with a jump to around 20% when a rapid jog is initiated.

Also to clarify, the physical spindle speed does not change, it remains constant, only the reading in mach.

Thank you,
TJ

Offline Hood

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Re: Spindle Speed Jumping on Axis Rapid Movement
« Reply #5 on: January 11, 2010, 06:20:49 PM »
Ah OK was thinking it was the actual speed, need to learn to read more thoroughly. Sounds like you are getting noise on the index input but I see you already have shielded cables and have some index debounce. I am wondering however if you maybe have too much Index debounce, , have you tried with it lower? Also is the shielding grounded only at one end?
 Dont know what else to suggest other than maybe try a different type of sensor as a last resort or even a different input pin if you have one spare..
Hood

Offline tjhj

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Re: Spindle Speed Jumping on Axis Rapid Movement
« Reply #6 on: January 15, 2010, 04:27:20 PM »
Thanks for the Help Hood,
I will break it all down and see if I can come up with anything usefull. If I do Ill post it, in case someone else has the same problem.

Thanks,
TJ