Laser firing outside engraving area during fill operation

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Christian Meyer

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Jan 4, 2020, 9:31:55 AM1/4/20
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During fill operations our laser fires accidentally at the end of lines outside the actual engraving area. In the picture you can see the spots at the right edge of the letter. We are using the 14.04 lasersaur board with a BBB and the latest version of the driveboardapp.

I searched the forum and found that thread: https://groups.google.com/d/topic/lasersaur/1i36ZNAvRFo/discussion

But it's for the (old) lasersaur app and as far as I understand the commit is already part of the driveboard app.

How can this happen and how can we get rid of it ? Thanks!
laser.jpg

Martin Renold

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Jan 4, 2020, 12:31:21 PM1/4/20
to 'Ray Debs' via lasersaur
The old thread you found was fixed with  https://github.com/stefanix/LasaurApp/pull/64 and new versions are actually derived from lasaurapp, the firmware was never rewritten from scratch AFAIK.

Judging from your photo you could probably trigger on the laser output pulse width using an oscilloscope. An old arduino with a few wires as "door sensors" should be enough hardware to debug this.

I'm not familiar with the current firmware any more. Maybe it could be a new symptom of doing too much work in the stepper ISR? Even during normal use, microsteps sometimes get delayed because the CPU is doing too much work during acceleration/deceleration inside the IRQ handler. If this is the case, then it should go away with a lower feedrate.
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Christian Meyer

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Jan 5, 2020, 4:44:32 AM1/5/20
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The old thread you found was fixed with  https://github.com/stefanix/LasaurApp/pull/64 and new versions are actually derived from lasaurapp, the firmware was never rewritten from scratch AFAIK. 

Yes, I know !
 
Judging from your photo you could probably trigger on the laser output pulse width using an oscilloscope. An old arduino with a few wires as "door sensors" should be enough hardware to debug this.

Okay, but what can we learn from the result?
 
I'm not familiar with the current firmware any more. Maybe it could be a new symptom of doing too much work in the stepper ISR? Even during normal use, microsteps sometimes get delayed because the CPU is doing too much work during acceleration/deceleration inside the IRQ handler. If this is the case, then it should go away with a lower feedrate.

We tested different feedrates and it's always there, same spots in the same places.

If this is a firmware issue I would expect that there are more people having this problem?!

 
Am Sa, 4. Jan 2020, um 15:31, schrieb 'Christian Meyer' via lasersaur:
During fill operations our laser fires accidentally at the end of lines outside the actual engraving area. In the picture you can see the spots at the right edge of the letter. We are using the 14.04 lasersaur board with a BBB and the latest version of the driveboardapp.

I searched the forum and found that thread: https://groups.google.com/d/topic/lasersaur/1i36ZNAvRFo/discussion

But it's for the (old) lasersaur app and as far as I understand the commit is already part of the driveboard app.

How can this happen and how can we get rid of it ? Thanks!


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Martin Renold

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Jan 5, 2020, 8:08:37 AM1/5/20
to 'Ray Debs' via lasersaur
I'm suspecting firmware because you seem to have single pulse that looks stronger than the line itself. Maybe it's also plausible to send valid commands for that by mistake, it just looks similar to what you would get from a PWM glitch or related bugs.
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