Acceleration on vector engraving - not decelerating for tight curves

Numbers are in mm/s and are speed of that vector engraving layer.

I have tried changing the machine settings “Cut Parameters” acceleration max + min down to 15mm/s and it does not fix this problem because Lightburn does not consider these very tight curves in the middle of the M to be worth decelerating for.

Vector engraving continues along at whatever speed the laser has accelerated to around these very sharp corners. My Y axis is fairly large and heavy on this 900x1200 machine so the fast direction changes cause vibration in the belts.

The sharp 90deg corners at the ends of the W are fine because the motion planner is applying decel/accel settings to those movements.

I have tried searching for this issue and it seems like there is no compensation for curves below a certain radius to need slower speeds?

Really like the software - hope there is a fix in the settings I am just not seeing for this - or maybe it is a new feature that needs to be implemented to treat curves below a certain radius as new line joints for deceleration/acceleration calculations?

Or maybe the choice between treating those small curves as worth decelerating / accelerating is handled by the Ruida controller? I am not sure exactly what handles what yet?

For productivity sake I want to engrave at 30mm/s at least - but these errors that only show up on some specific shapes are limiting my speed. It does fine with straight square shapes because the s

Acceleration and speed management is handled entirely by the controller. If you run the job from RDWorks you’ll likely find it does exactly the same thing.

Are you saying you put both max and min acceleration down to 15 mm/sec^2 and it’s still doing this? Did you write the setting back to the controller?

Yes it still does it - written to controller - it is because it never senses that the curve in the middle of the W is small enough that it should slow down - still continues on at full speed as if it was a straight line.

There is no other compensation for this that you know of?

I built this machine from scratch 2 years ago. Considering switching to a G code based system because of this issue and others with the Ruida controller. I don’t do any raster engraving only vector cutting and vector engraving. Thinking of a Duet3 or a Klipper based controller right now. Just converted both of my 3d printers to Klipper and the configurability + smooth motion control is like a dream… I would not consider an 8 bit solution (grbl on ATMEGA) at this time based on my extensive experience with their limited capabilities in 3d printers. Klipper does not explicitly support laser cutters but I am pretty sure it will work or else it is open source so I can of course fork it…

Any insight on the gcode route?

The biggest issue you’ll have with GCode is power control - as the laser slows for corners, you generally want the power reduced to compensate for the lower speed, but if it goes too low the beam will shut off completely. This is why DSP controllers allow Min and Max power settings. GCode systems generally don’t, at least, not per-cut. Some will let you set it globally.

Can you post a screen shot of all your settings? I’m surprised that this is happening. RDWorks does have a section for ‘small circle speed limit’ that I haven’t investigated, though my assumption is that it’s handled in the software. I could potentially mimic that behavior, but I haven’t seen a need for it up to this point.

As a test, I produced this shape and ran it with the ‘Small Circle Speed’ limits enabled in RDWorks:

It limited the speed of the entire path, not just the corners, so this is basically useless.

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Thanks for the hints I appreciate it.

I just decreased the accelerations to 20 (the lowest it will let me set them) and it still does it in the middle as it has accelerated to a fairly fast speed by then. It’s also starting at a ridiculously slow speed… It’s not the acceleration that’s the issue - it’s entirely the fact that it does not bother to apply those calculations to the tight curves in this shape. I can export the M shape for you if you want to experiment.

I’m not too worried about decreasing power in corners as the tube is RECI W4 100w and increasing to W6 130w soon = not very good for fine engraving anyway… I’m only interested in dark lines so it’s always a fairly deep engraving like in my first image. But I will experiment with keeping the power min/max the same and see if the results are acceptable for my application.

Here is a DXF export of the M.

I just saw your other post about the small circle options. Thanks for testing that! That is too bad it does not detect the corners and change speed… Interesting.

I am wondering how firmware like GRBL or Klipper handle small radius curves too - have not searched for that info yet but it may be the same or maybe they do proper accelerations on small curves which seems like you would want.

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