HI, as mentioned in my last post, I am a laser newbie and am LOVING Lightburn. It makes it so much easier for newbies!
Up until now, I have only been using the software to engrave or burn through powder coating. My latest project, however, is to cut plexiglass into a shape. Can anyone help me on what settings I would need to use to cut all the way through? I really don’t even know where to begin.
Thanks for any help you guys can provide!
Sondra
we need to know what kind of machine you have
Hi,
Is the plexiglass cast acrylic or extruded?
Secondly, what thickness are you going to use?
I have a Chinese Laser 60 watt with a Ruida controller. I don’t know if it is cast or extruded, it is the cheap stuff from Home Depot and is .093" thick.
Hi Sondra, I would suggest that you find some leftover pieces of the materials that you want to work with and do some testing. It’s not because I do not want to help you, contrary. The best experience you can get with different materials and your specific machine will come from these tests. If you start with e.g. 4mm acrylic you could use 50% power and start with 750 mm / min speed, depending on the result, throttle or set the speed up until you get a fine glossy cutting surface. When you feel a little more confident, you can of course also turn up the power. I do tests of all the materials I work with and save a reference piece with the optimal settings gravered on this piece. Good luck and I hope you also enjoy the learning process itself.
I think @Bernd is spot on and good advice. .093" thick is less than 2.5mm thick to will cut at low power and high speed. In this case start testing around 12mm/sec at 60% power (you’ll have to calculate that into the old money 
) and speed up from there until it just gets through it.
Remember, all lasers, even the same spec, will perform differently so test test ten. It’s worth investion the time.
Hopefully you’re not material called ‘Plexiglass’ but is really polycarbonate (eg Lexan). Polycarbonate is a material that blocks your CO2 Laser light (it’s used as the window on most lasers) and won’t cut, but will catch fire. Cast Acrylic sheet can be safely cut with a laser.
Plexiglass is acrylic. It was a brand name which became a generic term. Hence my question.
Sorry but you really should check before stating things as fact to anyone, especially newcomers who come to learn.
Thanks David and Bernd…I did as you guys suggested and played with the settings. What I found was that if I made several passes of the shape, it cut all the way through! I’m not sure if this is the best way to do it, but it worked! LOL Where there is a will there is a way! LOL
Thanks guys for the patience and support!
You are correct, I sit corrected. I was confused with Lexan which is polycarbonate and will catch fire if you try to cut it with a CO2 laser.
Thanks Tom, 
Hi,
What you are looking for is efficiency unless its just a hobby (like me, mostly). That is the best cut in the quickest time. For the thickness you have there you should be able to cut with a good finish in a single pass and quickly. What were your cut settings?
Yes I will admit it took a bit longer to cut through. My settings were 3 in/s and 95% power but it only scored the acrylic…these were the only two variables I played with, but added passes when it didn’t cut through. It took 6 passes to finally cut through. Am I missing something?
Wow! That is very quick and why it’s only scoring. I would have to guess it needs turning down to under 1 inch/s. First try with say 1 in/sec and 60% power. If it cuts through easily you have a baseline. Speed it up to the point where is stops cutting all the way through and back it off a bit. Bedtime for me here so may see your response tomorrow.
Sondra, in your profile is 50 Watt laser, if we are talking about a CO2 laser with this effect it should be able to cut without any problems acrylic with a single pass and especially when it is so thin. In fact, you may find that the material melts back together if you are too slow. Also check if the focus of the laser is set correctly. Acrylic is the same as Plexiglas and it is ok to use with our laser machines. Diode lasers are not suitable for processing acrylic due to their wavelength. You could also try searching for this topic here in the forum, there are many interesting posts that deal with CO2 laser and acrylic, I mean I have done something with pictures once …
Hi Bernd!
Thanks for all of the info! I actually upgraded to a 60w so I’ll make that change in my profile. I’ll be playing with it again today so I’ll let y’all know about my progress!!!
Thanks again for your help!
Get a new laser? Your profile says ‘50 watt’ 
Get used to figuring this out on your own. It’s nice to have a starting place, but…
I draw a line at a starting speed/power. Use a piece to cut the line. Near the edge but it’s nice to make a complete cut so you can examine the edge quality. You can cut lots of line in an inch of material and pick what you like. I cut with a 4", but it’s way closer to the work piece and a wider kerf because of that. I find it cuts with less power…
They have given you good point.
It will change with natural materials since their composition varies.
I use a lot of this to make things like drill templates.
Wow … I did not know that.
And like the Bumble Bee that dont know its to heavy to fly I went ahead and did it anyway.
I cut 16mm washers out of 1/16 and 1/8 plexiglass (acrylic) … works great … no fires.
Have cut all colors solid and transparent.
I use air assist with low power 30% and a speed of 30 - 35.
Have the plexiglass on standoffs about 3" high.
It makes two to four passes but the last pass the washers just kinda fall out.
These are used as decorative rings in the pens I make.
I fixed my previous post which misstated the problem… It’s Polycarbonate that is the problem material. Sorry for the confusion.
The technical or scientific name for acrylic is polymethylmethacrylate.
Most of us that use CO2 machines are in mm/s but if you convert 3 in/s, it’s 76mm/s. I cut Acrylic at 14mm/s at 60%. You are probably ‘speeding’. Mine is a 50 watt (lol), just cut a .75" disk out for a project. One pass with this material
If the material passes (or reflect) the emissions of the laser it will NOT do any damage to the material. The material must absorb (block) the energy to excite (heat) the molecules.
Any material that blocks the transmission of the emf from a laser, will suffer damage to the material. How much damage depends on the amount of emf absorbed. My glasses are polycarbonate, makes good safety glasses and can be cut. Polycarbonate does not produce good edge results and isn’t used very often. It is very durable and is used in fighter canopies. It is as safe as acrylic to cut.
The window in my machine is acrylic as far as I can tell. Polycarbonate is more expensive, so I doubt these low cost machines put that in the window, where acrylic does just as well.
I keep a pair of polycarbonate safety glasses around for visitors who don’t wear glasses.
What isn’t absorbed is UVB that is sometimes generated.
