I did several passes on both, playing with settings as I went deeper and deeper.
I would say yes to both different lpi and torch, however I have not tested either. After seeing recent activity with the 3D settings I decided to give it a try. There is lots of potential for sure.
You can actually use a heat gun to polish acrylic but flame polishing with a torch is the more common (and likely faster) method.
Ooh. Another justification for the rarely used oxy-acetylene torch set that I “absolutely needed”.
“Never glue a flame polished edge,” they say. Isn’t every laser cut edge essentially flame polished?
Just scuff it first with some 120 grit sandpaper before applying the glue.
I believe so. I didn’t watch that video, but saying “polished edges may give undesired results” would have been more informative than “never do that”.
IIRC, extruded acrylic has more of a tendency to craze than cast, but it’s possible with both. And a polished surface might not be as conducive to the capillary action that some gluing techniques rely on.
People say annealing the acrylic helps/solves the crazing problem.
The issue is not the roughness, but that the flame induces residual stresses into the plastic that cause small cracks (crazing) when in contact with glue.
Never experienced that, and I’ve flame polished tons of plexi/acrylic.
You just haven’t run across it yet. The video above shows clearly what happens, but the issue is a “can happen” thing, not necessarily a “will happen” thing. The time that the acrylic is exposed to liquid solvent plays into it as well. Faster evaporating solvents tend to have less impact on crazing.
@Scott.Burns is correct about the roughness not being the issue. The smooth faces of acrylic weld/bond just fine.
Very cool. The spiral cut is really interesting.
Very good experimenting, thanks! 
For solvent bonding for items like boxes or any right angle construction, a laser cut edge isn’t 90 degrees from the face, and will present less contact surface area. A saw cut is better for a flush fit and strength of the joint.
Stop fooling around, we all know these are just ice cubes! 
Of course, if they were, I guess this would be just as impressive, really…Great job!
That jingle makes my eyes bleed. hahaha.
Do you know if that acrylic is cast or extruded. The reason engraving on cast looks good is because leaves a frosted surface. But if you wanted something polished like this extruded might be better.
Hi. I love your project. 3D grayscale like those can be found on internet but I always prefer to understand how things works. Is it a complex process to do those type of images? With what kind of software have you done those?
And finally. are you french with a ame like this?
Cordialement
Marc SIMON
The grid pattern I created in Adobe Photoshop and the spiral was something I found online and then modified for my needs. The same type thing could be created in many photo editing programs (GIMP is free) and even in vector programs like Illustrator or Inkscape (also free).
You can also make depth maps using 3D software. There are various methods of doing this and some experimentation has been done and shared on this forum. Tutorial - Creating a Depth Map from a 3D Model for 3D Engraving!
There have also been some experimentation making depth maps from physical objects. Thinking out of the bottle!
The French side of my family is quite a few generations back. We have visited Paris and look forward to exploring more of France.
thanks a lot
Did you use the original image or a solid image for the defocused pass?
Just the same image I was using for the engrave. A solid image would be an interesting test. It might make a more consistent finish across the entire surface. I also like the torch idea that was mentioned earlier.