Question about circle diameter when engraving vs cutting


#1

I probably need more (or less caffeine) today… can someone help me understand the concept behind this?

I have a circle that I cut that fits a small magnet inside it perfectly. But when I engrave the same circle, it is significantly smaller and the magnet doesn’t fit at all.

The cut circle is .225” in diameter, but the engrave has to be .25” for the magnet to fit. (This has been in thick :proofgrade: walnut, but that shouldn’t make a difference, I don’t think…)

What is the principle I’m missing for why a cut and engrave are so different in actual size?


#2

Shape of the beam?

If you want to have it engrave large enough though, duplicate the shape and run a Score around the edges. Cleans up all the buildup in the lower regions. (I use it a lot for engraved slots and whatnot.) :grinning:


#3

it’s probably your SVG file. You can’t have Responsive turned on when you export the SVG, otherwise this kind of thing can happen.

Is the rest of the part scaled correctly?

EDIT: Responsive can’t be ON… thanks @jbmanning5


#4

I think it might be algorithmically different. Cut and score both travel on the stroke line so half the kerf width gets burned away on both sides. Today neither of these operations pays any attention to inside and outside.

For engrave though even for vector objects it ends up rasterizing it since eventually it is a set of waveforms that describe a raster image (lines made up of varying power or pulsing lasers on each line). The raster into waveforms pays attention to dot on or off and this is based on inside or outside the shape.


#5

For a perfect raster image with no bleed or aliasing it would be smaller by a kerf width (1/2 in each side), but I’m sure it isn’t perfect since it isn’t entirely predictable how much overlap on the burned pixels there is going to be (material dependent) so the cut will be bigger but probably by some number between 0 and kerf width.


#6

Other way around - responsive should be unchecked (off). Responsive removes the width and heights tags from the SVG which will result in undesirable scaling.


#7

For things like that, I score around my engravings to give them a sharper edge.


#8

I was thinking the same thing: raster vs vector operations maybe.