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Offline spunk

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Mach3 and stopping
« on: September 28, 2009, 05:00:01 AM »
Dear all

Having a little problem with mach3.

sometimes mach3 just stalls, losing several steps while doing it altough the steppermotors stop in an instant.
There are no led's flashing nothing. Just a stop at a random place.

Do have a Pokeys hooked up to the machine but the stop button has several other funstions hooked up trough a brain so if there was some interference these functions would also be activated.

When the machine has stopped it can be easily started again with the start button but several steps are gone.

Second problem is that when i do hit the stop button it also loses some steps... perhaps this is related to the 4000mm/min i'm running?
there are no milling forces because i'm not milling, just dispencing silicone.


anyone? just let me know if you need additional information.

Offline Hood

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Re: Mach3 and stopping
« Reply #1 on: September 28, 2009, 07:10:16 AM »
Stop button acts like an E-Stop in the respect that it is instant and no deceleration is used so you are very likely to lose position if the axis is in motion. The procedure when an axis is moving is to press Feed Hold first then  if required press Stop after the motion has halted.

Your E-Stop problem could be a few things, is there any message in the ticker window when it happens? Brains may not always pick up an input if it is a very short input as Brains only work at 10Hz so if the signal is short duration it can easily fall in between scans.

If there is no message in the ticker I would disable the Brains and PoKeys and run without them to see if the problem is still present, if it is then you know its not them, if it is not then you know it is and either way will know where to start looking to see where the problem lies.

Hood

Offline spunk

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Re: Mach3 and stopping
« Reply #2 on: September 29, 2009, 03:08:13 AM »
I tried the feedhold button but still it loses some steps.
perhaps the acceleration of the axis is set too high?

problem of stopping isn't happening anymore since I upgraded to more stable power supplies and made correct earth connections

thanks for the answer

Offline Hood

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Re: Mach3 and stopping
« Reply #3 on: September 29, 2009, 04:35:53 AM »
If pressing feedhold causes lost steps then, yes, it is likely to be too high acceleration set. However I would expect to also see lost steps when accelerating rather than just decelerating.
 How do you know you are losing steps?
Hood

Offline spunk

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Re: Mach3 and stopping
« Reply #4 on: September 29, 2009, 05:35:22 AM »
When stopped the next cycle has a different position.

always small differences but still to much. would need a repeatability of 0.05mm

what would a good acceleration value be?

when running the machine the axis do seem to drift from time to time so acceleration could be to guilty one?

Offline Hood

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Re: Mach3 and stopping
« Reply #5 on: September 29, 2009, 06:02:06 AM »
Afraid no one can tell you what the velocity and acceleration should be set to unless they have an identical machine to yours. Motor type/size, Drive type, gearing, ballscrew/leadscrew, axis weight etc etc all have a bearing on this so its a case of finding out yourself by trial and error.
 Easiest thing to do is drop the acceleration by maybe 25% and see if the problem still happens then work from there.

Hood

Offline spunk

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Re: Mach3 and stopping
« Reply #6 on: December 07, 2009, 06:47:40 AM »
Perhaps this should be in the pokeys section but here's the latest

Disconnected the Pokeys and all problems disappeared...

anyone got a clue about this one?

Offline Hood

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Re: Mach3 and stopping
« Reply #7 on: December 07, 2009, 06:53:03 AM »
To be honest I had issues with the last few PoKeys plugins I tried so ended up going back to a previous one that worked fine, now however I dont use the PoKeys at all as I grabbed a bargain of analogue inputs for my PLC.
Hood

Offline spunk

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Re: Mach3 and stopping
« Reply #8 on: December 17, 2009, 11:13:22 AM »
what release of pokeys worked best for you?

Offline Hood

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Re: Mach3 and stopping
« Reply #9 on: December 17, 2009, 04:13:56 PM »
Will have a look on the mill tomorrow as I should still have the plugin loaded, if you dont hear back bump the post to remind me.
Hood