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Author Topic: Why is it running off at random?  (Read 10370 times)

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Re: Why is it running off at random?
« Reply #10 on: June 01, 2010, 06:12:57 PM »
IF you will notice there was a total SHIFT in the offset as when it shifted it shifted on the Center point of an arc/circle. AND stayed on the exact center of that arc/circle.  AND still cut a good arc/circle I have seen it shift IN and I have seen it shift OUT.

 THAT is not lost steps or NOISE as if it was the arc would have been offset by the amount of the missing steps AND it would have still cut the same radius as the code here it did none of the above.


I realize the WORDS are English but this make no sense at all to me. Could I get a "G-Code for Dummies" explanation of this.

Offline Hood

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Re: Why is it running off at random?
« Reply #11 on: June 01, 2010, 06:13:33 PM »
Do you reckon  this the same problem as you were always talking about on Yahoo? Do you still get it?

Hood

Offline Hood

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Re: Why is it running off at random?
« Reply #12 on: June 01, 2010, 06:15:48 PM »
IF you will notice there was a total SHIFT in the offset as when it shifted it shifted on the Center point of an arc/circle. AND stayed on the exact center of that arc/circle.  AND still cut a good arc/circle I have seen it shift IN and I have seen it shift OUT.

 THAT is not lost steps or NOISE as if it was the arc would have been offset by the amount of the missing steps AND it would have still cut the same radius as the code here it did none of the above.


I realize the WORDS are English but this make no sense at all to me. Could I get a "G-Code for Dummies" explanation of this.

What Terry is saying is if you look at the pics you see the axis moves out one way then back the other, if it was lost steps then it would tend to just go one way, well that is if it was exactly on the apex.
Hood
Re: Why is it running off at random?
« Reply #13 on: June 01, 2010, 06:26:19 PM »
How does that help me with my problem?

Is it some sort of computer setting?

The computer is a dedicated machine with no internet or network connections. I stripped out all the extra windows crap. There is no anti-virus software running.

Neil

Offline Hood

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Re: Why is it running off at random?
« Reply #14 on: June 01, 2010, 06:35:24 PM »
If its the same problem that Terry gets then I dont think its ever been found and if I remember the only way he could get things back up and running was a fresh install of Mach, but Terry will advise.

If however the DROs dont show this movement then it is not likely to be the same and although Terry says it cant be  lost steps because it goes one way then the next that would only be true if it was at the apex, if it was not then it could well be lost steps.
  So do you think the line goes off directly at the apex, from your pic it looks to me that it is before. Also looks to me like the line going up seems to be at the max height that the circle would be, so that does suggest lost steps to me.
Hood
Re: Why is it running off at random?
« Reply #15 on: June 01, 2010, 07:30:58 PM »
So do you think the line goes off directly at the apex, from your pic it looks to me that it is before. Also looks to me like the line going up seems to be at the max height that the circle would be, so that does suggest lost steps to me.
Hood

It does appear that it starts to go wrong just before the apex. The Y axis seems to be functioning but the X axis is falling behind.

I just did the driver test and it is flat line up through 75mHz. At 100 it gets some minor noise. Is there any advantage to upping the Kernal speed?

Neil

Offline RICH

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Re: Why is it running off at random?
« Reply #16 on: June 01, 2010, 08:44:19 PM »
Neil,
I haven't had that happen to me in a long time. My cure back whenever was to  slow the velocity down. Conservative here at 30 to 40 % of max velocity.
When steps are missed the steppers  may just go off with a mind of their own.  If the motors are getting hot then they can start to act funny and do strange things, same for a drive that is very close to it's max amp rating for the stepper being used.
Sorry, i don't have an exact answer for you.

FWIW...
RICH

Offline ger21

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Re: Why is it running off at random?
« Reply #17 on: June 01, 2010, 09:55:27 PM »
It looks like the X axis practically stopped. Do you have any resonance on your machine, or dampers on the motors? My xylotex was practically unusable until I made dampers for the motors. Now it's rock solid.

As for binding, it can occur at any time. Do you lubricate your screws? They can get dry and start to bind. Also, if you see this lowering the acceleration 25% or so, and see if it helps.
Gerry

2010 Screenset
http://www.thecncwoodworker.com/2010.html

JointCAM Dovetail and Box Joint software
http://www.g-forcecnc.com/jointcam.html
Re: Why is it running off at random?
« Reply #18 on: June 01, 2010, 10:24:27 PM »
The max speed is set to 60 ipm on Xylotex 425 motors. The spindle doesn't appear to be moving all that fast when it goes nuts.

I don't have any dampers on my motors but have been planning on building some. I cut back the speed when I was having resonance issues before. I have also added an optp-isolater board to cut out noise.

Every time I fix one issue, another pops up and I am beginning to hate this machine.

Neil

Offline ger21

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Re: Why is it running off at random?
« Reply #19 on: June 01, 2010, 10:35:43 PM »
What kind of screws do you have, and how fast are you going when it happened? The Xylotex 425 oz motors will not spin very fast. Coupled with a poor choice in screws, it could be that you're trying to go faster than the machine is capable of, resulting in a stalled axis.
Gerry

2010 Screenset
http://www.thecncwoodworker.com/2010.html

JointCAM Dovetail and Box Joint software
http://www.g-forcecnc.com/jointcam.html