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Spindle speed varies when moving axis
« on: March 06, 2011, 04:56:43 AM »
Hi All,

I've just replaced my CNC4PC 11G breakout board following a failure of the original.

When I move the axis (Z or X), the spindle speed increases. The amount the speed increases seems to depend on the speed of the axis, with about a 500 rpm increase when rapiding.

The problem was not there before the board failed, but that was about 18 months ago.

I have tried changing settings in 'ports and pins' for the X and Z axis as I recall that that might be a fix, but no joy.

I'm using the 0-10v analogue output from the 11G to a Mitsubishi VFD. 

Has anyone experienced this problem or know of a fix?

Cheers,

Paul

Offline Hood

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Re: Spindle speed varies when moving axis
« Reply #1 on: March 06, 2011, 05:28:36 AM »
Try increaing the Step Pulse and Dir Pulse to 5 if not already done.
Hood

Offline ger21

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Re: Spindle speed varies when moving axis
« Reply #2 on: March 06, 2011, 06:54:09 AM »
Are your steppers wires possibly introducing noise into the 0-10V line?
Gerry

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Offline Tweakie.CNC

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Re: Spindle speed varies when moving axis
« Reply #3 on: March 06, 2011, 07:15:13 AM »
Paul,

I trust you set up the spindle output according to the instructions.

I am sure you did but it is just a thought.

Tweakie.
Success consists of going from failure to failure without loss of enthusiasm.  Winston Churchill.
Re: Spindle speed varies when moving axis
« Reply #4 on: March 06, 2011, 08:47:54 PM »
Ho All,
thanks for your replies.
I've had another look this morning and tried your suggestion Hood - unfortunately, it didn't make a difference.

Gerry,

I don't think it's noise from the steep/direction lines to the stepper drives.  I've used a good quality screened pair cable that has been grounded in the middle of it's length.

Tweekie, I've rechecked the setup - I can get a stable and proportional signal on the 0-10v connection.  When rapiding, this value increases.  e.g. 5v at 1000 rpm. Rapiding increase this to about 7v and 1440 rpm.

I've monitored the 5 and 12 volt supplies with a DVM, and these look rock steady.

Enabling spindle feedback control works - sort of!  Ther's a momentary change of speed at the start and end of a rapid movement, while the controller gets a grip.  But I feel this is fixing the symptoms rather than the problem....

Has anyone seen this sort of fault before?


Regards,

Paul

Offline Tweakie.CNC

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Re: Spindle speed varies when moving axis
« Reply #5 on: March 07, 2011, 03:20:39 AM »
Paul,

As the previous worked OK and this one doesn't it sounds as though you should be talking to CNC4PC as they may have made subtle changes to this function when introducing the later version board.

If you have, or know someone who has, an oscilloscope you could monitor the signal from Mach to the board and see if there is any fluctuation there that could be causing the speed variation.

Tweakie.
Success consists of going from failure to failure without loss of enthusiasm.  Winston Churchill.
Re: Spindle speed varies when moving axis - resolved
« Reply #6 on: March 16, 2011, 05:10:23 PM »
Hi All,

Just a quick update to let you know the current position.

After a number of emails with Arturo from CNC4PC, the board is being returned as faulty.  No amount of tweeking or reseating of chips made the slightest difference.

The replacement boards are from Peter Homman.

Regards,

Paul