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Author Topic: Odd spindle speed hesitation problem  (Read 2561 times)

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Odd spindle speed hesitation problem
« on: July 22, 2012, 09:56:07 PM »
I just upgraded my X2 minimill to enable spindle speed and flood coolant control. I'm using a Gecko G540. I immediately started experiencing a strange issue when running a program. The spindle periodically decreases speed momentarily. It doesnt completely stop, just slows for a split second. When I run the spindle from the original speed control pot it Is steady.

Then I tried control from the mdi. I entered an M3 S5000 on the mdi and the spindle spins up and is rock stable - just like when I use the pot manually. Then, I clicked the coolant on button and the spindle momentarily hesitated. Turning the flood on and off sporadically does this but not every time. Then I excersised movement with G0 command and that worked fine. Then I loaded a program and cut air with the coolant off. For most movements, the spindle was fine but for some arc moves (I cut a lot of disks and rings) I occasionallY get hesitations when the line of code executes.

If I run the spindle from the pot and turn the flood on and off there is no change. So it appears not to be an electronic issue I think but maybe a Mach issue. My kernel speed is at the lowest although the machine most likely culd support greater. I was going to try that but Mach warns that all axis will have to be recalibrated if I change the kernel speed. I have a lot of parts to cut in the next week so I can't mess with that right now.

What do you think about the above behavior? I wouldn't think that turning the flood on would take that much processing pow to cause a momentary stall on the spindle. As I write this I realize that flood has a 3 second pause to allow time for it to flow. I will turn that off (to 0) and see if that has any effect.

Cheers and thanks for the help.

Michael
Re: Odd spindle speed hesitation problem
« Reply #1 on: July 22, 2012, 10:18:53 PM »
Hi,

Could be acouple of things going on here.

On possibility is that electrical interference generated from the flood starting up is interfering with the PWM signal to the G540. If that was the case, I'd also expect that the step/dir lines would also be affected.

The other more likely possibility, is that Mach3 is momentarily turning of the spindle PWM when it turns on the flood output. A scope would verify that. I don't know how to check it otherwise.

Cheers,

Peter.
----------------------------------------------------
Homann Designs
http://www.homanndesigns.com
email: peter at homanndesigns.com
Re: Odd spindle speed hesitation problem
« Reply #2 on: July 22, 2012, 10:28:34 PM »
Thanks Peter. I don't notice any issues with the step/dir lints. As for the other possibility the hesitation is intermittent (doesn't happen every time I turn on/off flood) and more importantly, it sometimes happens when turning the flood off. And also, the situation that when cutting arcs also causes the hesitation so it isn't isolated to just turning flood on/off. In fact, once the program is running, flood is turned on at the start and off at the end so that probably wasn't the source that was causing my initial observation that led me to diagnose this.

Unfortunately, I don't have a scope.

cheers,
Michael
Re: Odd spindle speed hesitation problem
« Reply #3 on: July 22, 2012, 10:36:48 PM »
Forgot to mention, the flood relay is one I bought from you maybe 2 years ago that I just got around to using. I did not install the diode as my understanding is the G540 does not need it.

regards,
Michael
Re: Odd spindle speed hesitation problem
« Reply #4 on: July 23, 2012, 01:44:34 AM »
Hi Michael,

It is unlikely to be the relay, more the flood motor. My guess that it is in Mach3 somewhere.

You could try disconnecting the flood motor and see if it still occurs. If so, disconnect the relay from the G540. That may help narrow it down.

Cheers,

Peter.
----------------------------------------------------
Homann Designs
http://www.homanndesigns.com
email: peter at homanndesigns.com
Re: Odd spindle speed hesitation problem
« Reply #5 on: July 23, 2012, 08:56:36 AM »
Thanks Peter. Here's more info.

When I disconnect the flood relay and disable it in Mach the spindle still hesitates periodically when "complex" sections of gcode execute - it seems only at the beginning of the line of code for arcs. If I run the spindle manually it is stable during this same code segment.

(the flood motor is a little aquarium pump)

cheers,
Michael