Kerf - Understanding and Suggestions for improvement

Hi all,

Wondering if anyone has figured out a way to force Kerf outwards/inwards? I often nest multiple object inside each other which I am trying to apply Kerf adjustments to. Would this be the correct way to force the correct Kerf adjustments or is there a better way.

I have tried to create a separate layers in order to try force this: (No Kerf - Black, Out 0.07mm - Blue, In 0.07mm - Red, Out 0.07mm - Green) - To help understand what this is - Its an example of the 10 penny puzzle (circles are pennies and the square is the frame, so both need to be 100% accurate).

I need to set both the square line and the circles to have kerf offset outwards:

From my tests I observe the following:

  1. If you keep objects on separate layers you can force the offset inwards or outwards
  2. the Red layer did not work because the circle was within the square and therefor Lightburn automatically push the circle to be an inwards adjustment because it assumed in side of the circle was the waste object.

I think the issue is that the default behavior of assuming that an outwards Kerf adjustment in nested objects needs to go in opposite directions should not be a universal assumption. Personally if I set something as outwards I would expect it to always go on the outside of the line (it works in the Doughnut example in the user guide), and for box joints but nowhere else when trying to optimise design.

@LightBurn I know this topic has been discussed numerous times before and not trying to burden you but is there any work planned on the Kerf tools in Lightburn? A couple on the wishlist:

  1. Have a setting that turns off the automatic logic going in lightburn, so that if I set out its always on the outside of the selected object
  2. Having a way to preview the lines from kerf adjustment in the standard view.

Look forward to hearing how everyone is dealing with kerf adjustments.

You’re on the right approach to use different layers to isolate behavior and settings. Now add optimization setting ‘Order by Layer’ and you will see a difference in that the kerf offset and its alternating IN/OUT behavior of nested shapes will be isolated to each layer. Perhaps build your test case with larger shapes and use 2mm kerf offsets, will be easier to see the differences in Preview.

And I agree completely with your suggestion to show the kerf width relative to the shape outline in the Preview window, would be extremely helpful. Even more helpful would be a ‘Show Kerf’ button on the main shape construction window. Reference SheetCAM to see this in action.

vote here: Kerf Indicators in editor window · LightBurn

We noticed this a long time ago and now we just add or subtract to the base object and do not use the kerf offset anymore. This negates the logic in the software this is how we have overcame this obstacle. It is not as convenient but gets rid of issues that randomly pop up because you have an offset in a double cut box or some random thing.

When I use this, I usually use the lean in option and it will clearly show you what/where the software thinks is the kerf position.

This might be a good addition for feature suggestions and let us vote on it…

:smile_cat:

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