Corners won't cut

[rogermeier]

The solution post suggests increasing the min power level of the laser. Is there a way to do the same for a diode laser? The field to adjust the min power level in the cut settings is grayed out for me.

[Rick (Technical Evangelist)]

@rogermeier

The field to adjust the min power level in the cut settings is grayed out for me. - …a diode laser

Note: On GCode based systems, you only get “Max Power” - the power the laser will use when running at the chosen speed. Cut Settings Basics - LightBurn Software Documentation

Min Power is only used when using the Grayscale image mode, and is the minimum power of the laser for pure white. Increasing this value beyond your lasers firing threshold will allow the laser to fire for absolute white. Image Settings - LightBurn Software Documentation

[rogermeier]

Thanks for your quick reply. This makes sense.

The problem I’m trying to solve is that it seems that when the laser approaches corners the amount it dims as it slows down is a little bit too much. I get nice cuts all the way through the plywood, but I end up with these tiny tabs in the corners (on the bottom side) that hold the cut piece in place preventing it from just dropping out unless I run several more passes.
I’m new to your software and am still learning. I’m trying the “overcut” option right now to see if that helps.

[rogermeier]

Since a picture speaks a thousand words, here are photos of my test coupon with 10x20mm rectangles, each with a different number of passes (as indicated by the numbers in the top view). The issue can be seen in the bottom view where at the tail end (in the direction the laser moves) of each straight line there is a little bit where it didn’t quite cut through, not even after 18 passes.

The laser is a 3500mW/445nm diode laser, BTW, and I’m running at 400mm/min.

[Rick (Technical Evangelist)]

Have a read of this post:

Corners Not Cut, Some Lines Missing

The corners aren’t cutting and some lines are missing. It seems to be the lines that are at lower speeds. From what I have read on the forums I need to increase my min power % however it is greyed out and unavailable. I am running an Acro 1510 GRBL with a Jtech 7W laser. Thank you for your help.

[rogermeier]

Thanks. I did try constant power mode as one of the posts suggest, and, as that post points indicates, the results aren’t pretty as the corners are burnt too much.

[Afcj1993 (Alex)]

Hi, @rogermeier have you tried increasing your acceleration settings? By increasing how fast your machine gets back up to your set speed when going into and coming out of corners it should make the laser come back to its set power even faster while still allowing a slight power fluctuation in the very tip of corners so you don’t get those burns.

[Rick (Technical Evangelist)]

Yes, @Afcj1993 is on to it, as mentioned in the post I shared.

@LightBurn

Your acceleration might be incorrectly set.

Edit: I have moved and started a new post, as the other post was for a different issue and control system.

[rogermeier]

@Rick

Yes, @Afcj1993 is on to it, as mentioned in the post I shared.

@LightBurn

That is likely the problem. Paper is white, and white reflects the majority of the light from a visible light diode. Try cardboard or something off-white. Though, when you say the laser isn’t turning on at the corners at all, that’s strange - Is it moving really slowly on those corners? Your acceleration might be incorrectly set.

Ah, yes. Thanks to both of you for the suggestion. I was too focussed on laser power settings and missed the comment regarding acceleration in the post you shared. It’s currently set to 10 (I believe the default). I’ll give it a try with 100.

[rogermeier]

@rogermeier

Ah, yes. Thanks to both of you for the suggestion. I was too focussed on laser power settings and missed the comment regarding acceleration in the post you shared. It’s currently set to 10 (I believe the default). I’ll give it a try with 100.

Yup, changing the acceleration from 10 to 100 works dramatically better. I get cleaner cuts with fewer passes.

Thanks!

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