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Author Topic: Couple of funnies...  (Read 187 times)
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MarkW
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« on: March 29, 2020, 05:40:29 PM »

I have finally got back to this CNC Laser project and have made some good progress.  When I left off about a year ago, I was having no luck getting my PWM power control figured out.  I was successfu l getting variable power fixed only to find that I was engraving mirror images.  Y axis was reversed.  Fixed that. Vector engraving is going well so I took another stab at raster engraving images.  I have made some significa nt improveme nts in the past few days.  I will post some pics in the next few days to get some critical observati ons and recommend ations.  In the meant time....

I have noticed 3 things that seem odd.  The first one is kind of scary. 

I found that if I set my PWM period down in the 2Khz range my laser turns on at very very low power (won't touch a piece of paper) immediate ly when I issue an M3 command.  No movement nor FIRE button required.  If I move or FIRE manually, the laser fires at the called for power.  The machine works fine otherwise .  I was able to vector and raster ok because the extremely low power doesn't have any affect on the media.  When I set the PWM freq at the default Engine/Parameter value of 0.0002 (5KHz) it doesn't exhibit this unexpecte d result. Once I identifie d the culprit while using at 500Hz I went back to the default of 5K, verified proper operation and then increment ally stepped the freq down until it failed to work "properly".  I think that was someplace south of 3.3Khz but just don't recall exactly.    Sorry, I should have taken better notes.  I can go back and replicate this with pen in hand if that helps.

I discovere d the second funny as a result of the first one.  When I use the AUG function, generate code and execute it through completio n, I noticed that the laser stays on.  Auto on still blinks.  FIRE turns works at the called for power %.  Any subsequen t move lights the laser off.   At the end of the gcode file there is an M30 to end the code before the M5 to disable the laser and then another M30.  If I knew where the post processor was I could probably sort this one out by myself.

The last one I haven't really investiga ted much.  When I set Setup in Metric to TRUE in the Engine/Planner I got some very strange results. I will look into this a bit more when I have more time to document the effects accuratel y.  Right now I just home and then issue a G20 command to get to INCH units.  Works fine.

Mark
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ArtF
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« Reply #1 on: March 30, 2020, 06:28:45 AM »

Hi Mark:

   Lowering the PWM can have unexpecte d results due to the
setting of the Tickle pulse being set at 1ms. Various lasers
will repond different ly to the tickle. Id turn it off and see what
that does, the setting for the tickle is in the Setup for LaserMini mum
power.
  One of my lasers has autotickl e and doesnt use this at all, so
results will vary.  The problem is that the Pokeys only has power setting
of 0 - 100, so if the tickle is set to 1, that "1" is longer and longer
as you lower the khz for the PWM.. 1/100th of a 1 second period
is a lot more time on than 1/100th of a 200us period.

  So if you want lower frequency PWM, kill the tickle pulse.

>>ere is an M30 to end the code before the M5 to disable the laser

 M30 means rewind, not stop. Nothing after an m30 will be performed .

Art





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MarkW
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« Reply #2 on: March 30, 2020, 08:27:20 AM »

Thanks Art.

I had the tickle ser to 0  Yesterday when I was having this fun, with tickle set to 0 I noticed that free axis 4 display bounced between .9999 and 1 whenever the M3 was run.   That value did not change as I changed tickle from 0 a 3.  I'll confirm again today when I have some time.

The first M30 in the code appears just BEFORE the M5 which it's followed by a 2nd M30.  So the program is rewinding before the M5 disables the laser power. 

Mark

* Macie Pondering EDITED FOR BREVITY.tap.txt (0.64 KB - downloaded 9 times.)
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ArtF
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« Reply #3 on: March 30, 2020, 10:38:19 AM »

Mark:

  Thx, Ill change that in Auggie, it outta know the m30 has to come last.

Ill also check that tickle to see if I can see anything screwy..

Thx
Art
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