I’ve been consumed by the “puzzle bug” lately, and one thing I constantly encounter is that simple (proofgrade) cuts results in pieces that will only slide together one way. This is a result of the cut being slightly tapered - cut, of course, is not what’s happening, but rather the annihilation of material nearer the surface is more significant than that down below.
In pondering this conundrum, I was thinking - wouldn’t a “straight cut” proofgrade setting be useful? Pretty sure it’s a simple matter of splitting the cut into multiple passes, which I plan to experiment with, but has anyone else spent time thinking about this?
… and another thought I’ve had, is whether the laser could be “modulated” at a high frequency, dependent on feed speed, so that it mimics the effects of multiple passes in a single pass?
actually, that’s exactly what’s happening. the laser isn’t a perfectly straight light. it’s cone shaped. that’s why the focal point is so important. it focuses the narrowest point of the beam at the surface of the material.
if you defocus significantly, you’ll exaggerate that tapering of the cut. i’ve used that intentionally sometimes to make a less flat cut. once when i made a replacement air grate for my HVAC and once when i made tapered dots that i used on the back of a piece of acrylic that slid into a hole cut in a board. that allowed the piece to slide in until snug.
I meant it’s not really “cutting” - it’s blasting the material into the next dimension, but in order to get thru the material, the precise focal point is somewhat of a compromise.
Trying to figure out if we could “fool” it with multiple passes at different focus heights…
It gets complicated. Because if the beam isn’t in focus at the surface of the material, then the part of the beam that doesn’t fit through the kerf never makes it through to the lower levels. And you get additional cutting/charring/melting at the surface. Meanwhile, if the beam is in focus at the surface, you get a mirror effect that bounces a bunch of the beam to the bottom of your cut. So you might be able to do a little alteration of depth, but I’m not sure how much before things go sideways (so to speak).
You’ll get the “straightest” up and down cut by focusing the beam at the midpoint of the material.
But it’s going to leave a wider kerf at the top and the bottom of the material, and your pieces are going to fit more loosely.
I would leave the FP focused on the surface, go as fast as you can to get just barely through the material, then maybe try a second pass at MUCH lower power focused at the midpoint. You don’t want to focus at the base, it will leave the freaking Grand Canyon at the surface. (AMHIK).
To clarify again, I have “puzzle pieces” that need to fit together, but cut using PG settings, they will only fit together a certain way. i.e. Part A must be lowered into Part B, you can’t get Part B to drop into Part A without significant force.
Jules’ feedback might be the key - focus in the middle. I don’t need a “lock in place” fit, but a “snug” fit…
Again, don’t use PG settings. Focus just below the surface, cut at 100 power, and use the appropriate number of passes to cut through the material. For thick PG, it will probably be 3 passes at around speed 180.
