Optimization, cut Offset, cut Lead-in, Layers subtilty

Often times when building a design for plasma cutting I have a need to create a separate layer simply to change the tool path lead-in length from the optimal 5-4mm to something less such as 3-2, in order to fit the lead-in inside a skinny shape while continuing to use a 90deg lead-in angle. 90deg is best for plasma lead-ins since it minimizes a blowout when the shape cut finishes by ensuring there is maximum metal remaining at the cut termination corner formed by the lead-in; the arc is always looking for a conductive surface and thus less of a corner means the arc may jump to the save-side of the part being cut, not good, so 90deg solves that.

Anyway, back to the discovery… So on interior shapes that require a shorter lead-in, I would simply select the shape, change it to a new layer, copy the prior layer’s settings to the new one, then make Lead-in changes. Then I would preview the cut to see how the new layer was going to handle Offset and Lead-in, to ensure it in fact would occur inside the shape. Every now and then, I would have to adjust the cut Offset from Outer to Inner or visa versa, and same with Lead-in Angle from positive to negative or visa versa, in order to get the desired behavior of the tool path. Then sometime later in the design process, usually while previewing the tool path, I’d remember to check and maybe adjust Optimization Settings.

So I just discovered that removing Order by Layer in fact has the (assuming intentional) side effect of flipping the Offset and Lead-in behaviors from inside to outside or visa versa, but just for the usually interior shapes that I had moved to the new layer. I use to get frustrated when the flip would happen assuming it was a bug but then I could not reproduce it for the purpose of submitting to LB support.

Anyway, I thought I’d pass this on in case others have had similar frustrations with Layers, Offsets, Lead-ins, and Optimization Settings. I’m not suggesting this is a bug, the behavior as is seems repeatable and consistent with documentation as to how “Order by…” optimization occurs.


If you have “Order by Layer” set, it considers only shapes on a given layer for determining inside / outside order. If you don’t have that set, it looks at the entire design. It’s partly intentional / part side effect.

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