Slow and weak Power in corners while lasering

Mostly Printed CNC - MPCNC Troubleshooting
1

Hey there,

i bought a Neje A40640II and installed it. Everything works fine until i ramp up the speed. In corners the power and speed is reduced.

I searched the internet a long time and it seems to be some kind of fault of acceleration, feedrate and junktion deviation.

I played around with the values and i cant make it to work properly.

If i go faster than 500mm/min there are gaps in the corners like shown in the image.

Is there any setting i’m missing out, or is there any other solution to it?

Best regards
Corners
ezgif-7-9359ae35d71

2

There might be an overcut setting you can play with.

Edit: that’s a 12W laser and you’re cutting some thick material there so yes, you maybe just can’t do that sort of speed with that power of laser.

MDF board 8mm cut ———— 120mm/min,S1000, 3 pass
https://neje.wiki/doku.php?id=laser_module_406040w#wood_engraving

3

you bought a laser and installed it on what? What firmware are you running on your thing you installed it on?

Is it a switch acceleration issue? The laser is moving clockwise, opposite what i was thinking. I was wondering if it wasn’t turning on until it reached speed, but it is turning off early before it stops to turn for the corner. Can you up your accelerations? Not knowing the mass of the thing it is connected to, that may or may not be a bad idea.

4

I am assuming you are running this on a MPCNC Primo based on the section of the forum and what looks like the bottom of the Z for a primo.

I run a Laser on my primo as well and have never had the issue you are seeing. What software are you running? If lightburn post some screen shots of your settings so we can compare. Also what control board are you running? And what firmware version on that control board?

1 Like
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Both grbl and Marlin firmware support a laser mode setting where laser intensity is reduced as the tool slows down for corners - this prevents burning in the corners. It also removes pauses after intensity changes, which are needed for spindles to settle at the new speed while laser intensity changes are essentially immediate. Assuming counter-clockwise motion (from the video clip), it looks to me like the laser is stopping as it approaches the corner and starts up again after the turn in direction.

Ideally, the laser mode setting should turn the power down, but not off. Does your laser support PWM power control? That’s a requirement (as I understand things) for laser mode to work as designed.

Is there a minimum current your laser needs to keep firing? Perhaps the power setting is dropping below that threshold. I use Lightburn, this documentation page explains the effect of the Minimum Power setting.

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Im not trying to cut throu. Just to engrave a full square.

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Its a MPCNC Primo with the latest Firmware. I tried to play with acceleration, feedrate and junction deviation. Nothing helped

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Yes it supports PWM

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I was editing my reply while you posted these answers. Check out my link on explaining Minimum Power setting in Lightburn - there may be a similar setting you need to put in whatever is generating your gcode.

10

Are you sure it’s a closed vector? I gave had this happen on a open vector and the delay on excleration

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What controller? The Jackpot controllers run fluidNC, a grbl decendent, while SKRs run Marlin.

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@ttraband Its a SKR. From what i googled a few days ago, minimum Power is not available for Marlin. I cant seem to find the option in Lightburn.

@timonjkl Yes its closed. I made a square in Illustrator and one directly in Lightburn. Both with the same result.

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Here’s the link I found searching the Lightburn documentation site - Corners Are Too Dark, Too Light, Or Missing - LightBurn Documentation.

My controller users grbl, so can’t help with the Marlin setting.

3 Likes
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Thanks @ttraband i saw the page before, but as i was rechecking the machinesettings in Lightburn i saw the “Tool starting acceleration” setting that i missed before.

After i bumped up those the cut was perfect!

Thanks for all your help!

4 Likes
15

Glad you got it sorted out!