Laser vs. CNC Mill for deep acrylic engraving/3D work

mill
tools
x-carve

#1

For those who know, since I will have a GF and my x-carve, curious about where to use each in a project. If I wanted to deep engrave a custom piece of acrylic (for argument let’s make it 1cm thick). It would seem that thinking about each machine, the GF would be the tool of choice to make a smooth side cut, while the CNC mill would be better at carving out deep engraving (say many mm deep). And if this is true, one would need to set this up in CAM to say cuts are with the laser and pockets are with the mill?


#2

It seems to me you would have to export only what you want cut to a file for the glowforge and what you want to mill to the CNC mill. Depending on how fine of work you’re talking about, because of the camera positioning system I think milling it first and then placing it in the glowforge for both positioning the cut file over the milled piece and final tweaking of the cut file because of any imprecision of the mill would be the best order of operations.


#3

I agree with @caribis2 's assessment. While you could define both attributes in the CAM file and ignore the cut through path, it’d be simpler and smarter workflow to define the pockets for CAM and then finish with cuts on the laser. You could potentially also use the laser as a smoothing pass on the CNC cuts to clear up the acrylic (similar to how you’d use heat on a cut edge to return it to clear). That would take some experimentation, but I’m sure it’s doable.


#4

Literally came in to suggest this, haha.


#5

Nice. Thanks for the suggestions @caribis2 @JLabs . Now when one does smoothing, do you have to account for the kerf? Or is the GF going to focus on the “surface” to melt it even though it’s already milled?


#6

I can’t speak to GF specific setup for doing this, but on another laser I would start experimenting with a low-power, high-speed defocused pass across the CNC milled pocket and then adjust until I got the result I want. If/when GF implements 2.5d greyscale engraving it would simplify the focus and then you’re just experimenting with speed and power. If you can do a focus offset that may be helpful too. When you’re doing soft-surface heating you don’t necessarily want a perfectly focused spot, you’re better off with a wider spot with more falloff to heat more smoothly across the surface.

There are quite a few different paths and orders to take to do this. You may find doing less power and less speed gets a better result, while you might prefer a tighter focus and more power, etc. Best option is to experiment on test pieces until you get the results you want, then write them down and share with the rest of us!


#7

I’ve never used a laser but have been using a fairly large CNC mill for the past 8 years, often on acrylic. For me the choice of which tool to use (mill vs GF) will mostly depend on appearance, speed, and special features or requirements. If it is significantly faster to use mill, then that’s what will get used, though fixturing time may play a role there. It’s pretty attractive to think about just laying a sheet of acrylic down on the bed and pressing the big GF button as opposed to trying to fixture a blank in the mill vise or fixture plate and cut the part without the need to deal with tabs or parts getting damaged as they drop out of the stock. Then too, the GF might allow for much thinner slots than can be accommodated by a milling cutter. OTOH, the GF won’t work well for threading or cutting through > 1/2-in thick material and perhaps not even > 1/4-in thick depending on how well the flip-over registration works. It would be very cool if the GF could be used to “polish” the bottoms of machined pockets and make them clear.


#8

Seems like a perfect application for the laser in a defocused mode.


#9

I’ve done this by hand on a previous laser and it worked well. I believe it will work on GF; only issue is if you have enough focal range to fully defocus it.


#10

Thanks @jbv and @dan - It’s on my list of things to try with the GF.