Having trouble joining the ends of shapes

I have’nt changed any settings since the last time I used LightBurn, and it usually cuts/burns perfect circles, squares, polygons etc and joins the start and finish.

Today I tried to cut some shapes and none of them are joining up at the start and finish position.
I may have a setting wrong somewhere but I can’t find anything wrong.

Also tried in T2Laser and it works fine.

This is what happens in LightBurn.

This is with T2Laser.

Any help would really be appreciated.

T2 Laser is probably using ‘constant power’ mode (M3) and LightBurn is using variable power mode (M4). You can switch to using the M3 device in LightBurn to make it behave like T2, but then you get the burnt start / end points and corners like T2 is giving you.

Type $$ in the console and press enter, and paste the settings it spits out here. It’s probably laser mode not on ($32=1) or the spindle rate setting in the controller and LightBurn don’t match. Read the ‘Short Version’ here for details: https://github.com/LightBurnSoftware/Documentation/blob/master/CommonGrblSetups.md#common-grbl-setups

Here are my settings, same as always, nothing has changed.

Double click your line layer - do you have ‘Perforation mode’ enabled?

You can reset a cut setting completely by clicking the ‘Reset to default’ button on the bottom left of the cut setting window.

Thanks Oz but I already tried that. Also tried different power and speed settings and got strange results.
Some settings let it burn longer and almost joined the shape ends, but then it was burnt too much.
Other settings and I ended up with just half a circle or square. It’s really strange.

What are your Device Settings? (post a screen shot?)

Had to take a photo cos it’s on a different pc to the one I’m on now. Hope ya can see it ok.

$120 and $121 are set to 10mm/sec^2 - that is really low for acceleration. Did you re-flash your controller recently? I can’t see that causing what you’re seeing here, but it would certainly have an impact when using variable power.

You also haven’t showed what settings you tried to use for this cut. Can you show those too?

Acceleration has always been set to that and it’s usually fine. Not re-flashed since GRBL 1.1h came out in August I think it was.

I don’t believe this. I’ve been using the same type of paper for all the trials.
I just swapped for a different type and it’s absolutely fine.

Cut every shape all the way round and all the way through.

Thanks very much for your time and patience Oz.

Hahah - I actually thought of that (white paper with a diode), but you showed the cut with T2, so I figured it was the same material. You’re welcome.

Yeah it was only cheap paper but bright white, the other piece I tried was slightly darker.
I don’t really use T2 but it’s there if I need to compare things.
I really like LightBurn.
Thanks again Oz.

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