Running into a consistent issue cutting 1/2" clear acrylic rods.
My inclination was ‘it’s melting’ but I don’t think so…
Consistently the right edge of the cut is perfectly vertical but the left edge has a noticeable slope.
No matter how many passes or speeds it happens to the point where I plan my cuts but it’s causing a lot of waste.
What am I doing wrong?
Can you give a little information about your setup? I assume you are doing this without the crumb tray? Using a jig? How are you setting focus?
My newness is showing itself…
Basic model
I left the crumb tray in
Power full
Speed 140
3 passes
Focus anywhere from 0.2-0.5 but never varied between passes.
It’s melting and cutting unevenly. I did the same thing a while back and could never solve it. I decided to cut them with a conventional saw.
Super strange that it’s melting on just one side… (isn’t it?)
It is melting where it is heating the most. If you had a jig or even used bed pins that you could rotate the rod between cuts without lifting the lid you might get what you are looking for.
which direction is the laser traveling, left to right or right to left?
Not sure why that would matter, but worth asking.
Front to back and vice versa… only because of the length of my initial material but would be worth trying side to side.
Not sure why I haven’t tried that.
It does the same thing. Always cutting a slope to one side. I don’t agree with it being a melting issue or it wouldn’t be uniform over every cut and where I cut in the length of material would also impact it.
If it is melting (always to one side) then it has to do with the laser’s limitations and not the material.
It’s going to come down to physics either way.
Pictures would probably help us make guesses, I tested this a long time ago and my conclusion was “the cut isn’t clean enough, moving on”. I didn’t put a lot of effort into assessing why.
remember, your laser beam isn’t a flat shape. it’s a conical hour glass. the focal point is generally on the surface. so depending on the focal length a lens is set at and the thickness of your material, you will always have some slope in your cut. i don’t know how much of an angle you’re seeing, but that could account for some of it.
as far as melting on 1/2" acrylic, you’re definitely going to get some slump cutting it as slow as you need to on a 40w laser. i haven’t gotten the same kind of clean cuts on the GF that i do on the 75w universal. there’s just not enough power to go through quickly enough to avoid some of that heat melt.
And even that’s “ideally”. There’s no guarantee that we’re starting with a uniformly circular diffuse laser before focusing down, the effective shape might not be a perfect cone but maybe some sort of oblong thing that I don’t even know how to name.
I was wondering about that… figured I’d try with the tray out next to reduce (at least somewhat) any potential hour glass.
The last alternative option is just to pause between cuts to fully cool but then again that’s not really practical. Guess I should have sprug for a pro! (o:
I was thinking a cone tipped to a its side…
not sure what that gets you. you can manually change the focal point whether the tray is in there or not.
that 5w wouldn’t make as much difference as you think. 40w or 45w lasers are not the best tools for 1/2" acrylic. it can work, but you’re really pushing the limits of that power level and you’ll have to live with the downsides.
Here 's what the beam looks like:
… and here’s an example of how focus height can change the cut (end view of 3/8" maple which is actually .39"). Each of these pairs of cuts are at the same speed, but the right cut is focused on the surface, the left (deeper) one is focused at 1/2 that height:
That’s really helpful, thank you… I’m now without answers again (o:
Now if I could figure out why my rod only cuts strait on one side (always the same side, regardless of where the cut is made).
Any thermo dynamics engineers on here?
Pictures or it never happened at this point 
And I’m going to go back to the start of the thread at this point and say “right tool for the job”. I’d cut them with a saw.