Thunder laser cutting tips:How to cut smooth acrylics

Today we're going to talk about how to improve your cut smoothness when you're cutting acrylic and encounter a cut that isn't smooth.
For an even weaker blowing effect, it is recommended to use it with the 6mm nozzle in the toolbox.
1. Laser tube：80W glass tube
Blowing Intensity： Strong
Speed: 6mm/s
Power:50%
2. Laser tube：80W glass tube
Blowing Intensity： Week
Speed: 6mm/s
Power:50%
3. Laser tube：80W glass tube
Blowing Intensity： Week
Speed: 10mm/s
Power:90%

By slowing down and reducing blowing, you can cut smooth acrylic!

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[hjartland]

This is the most helpful acrylic cutting video by far. Thank you for making it!

[SarbarMultimedia]

Please do not think my comment is in any way critical of what is demonstrated here. The facts are essentially correct but it is rather misleading in that this demonstration is not universally applicable. I can see that the material is 8mm thick CAST acrylic and the lens is probably thei2" standard focal length. It appears that Thunder laser are demonstrating an accidental discovery of parameters for 8mm acrylic and the effect of air assist and speed on cut quality. Try this on 2 mm thick cast acrylic and it wont work.

Let me take a few second to describe the properties of CAST acrylic. It melts at 160 C and then boils/evaporates into acrylic "steam" at 200 C Imagine laser cutting a block of ice and you can then visualize that just behind the laser beam there will be a film liquid water on the kerf edges until the water freezes again.. That is exactly what happens to acrylic. Cutting is by evaporation and not by any chemical mechanism.. In the same way, provided the kerf wall is above 160 C there will be an acrylic self-leveling liquid you disturb it and accelerate cooling with full air assist. You will then get a non-transparent edge. as in test 1

Stop test 1 at 25 sec and note three things. the bottom of the cut is trailing behind the top (say 10 degrees), The first 2mm depth is very "disturbed" because of the air flow. the bottom of the cut is
rather "frilly"

Stop test 2 at 45 sec and because there is little air flow to disturb the top of the cut its clean. However although there is little or no air assist, note how powerfully the fumes are exiting the BOTTOM of the cut. Note also that for no change of speed or power. the "beam drag" angle has decreased (maybe 5 degrees?) and there is no "frilliness" to the bottom of the cut.

Stop test 3 at 1 min. The power and speed have both doubled but this cut is right on the edge of failure. The beam drag is back to about 10 degrees and there is a frilly bottom edge

The reason test 2 produces a flame burnished transparent edge is because this is thick acrylic and has to be cut slowly. Thus the the heat of "cutting" has a chance to build up in the kerf to keep it above 160 C for several mm behind the cut. You can often observe this film cooling and solidifying. If you cut 2mm thick cast acrylic you will run much faster and there will not be the heat retention in the kerf to create the self-leveling film. That is why you need to understand this this is not a universal solution.

The other interesting observation is the angle of the cut (beam drag). What causes that? Many suggest that the beam is being reflected by the acrylic surface, . That's not the way 10.6 micron light works . It ALWAYS wants to travel in a straight line. This is very easy to prove if you pause the cut. Now press the pulse button for about 1 second and observe how the beam does NOT reflect around the angled material but straightens the cut to 90 degrees. If THIS is a light beam cut then why the angled cut? Recall the observation in Test 2 about how powerful the fumes were exiting the BOTTOM of the cut. Well .only the first mm or so of cut is happening because of the laser beam . The superheated acrylic gas created within the kerf is flowing downwards and eroding (evaporating) the surface as it goes . Right at the bottom of the cut the frilly edge is caused by eddying gas.

One final interesting point is that this video only applies to CAST acrylic when the material is above 5mm thick. If you use EXTRUDED acrylic, although exactly the same chemical composition, it's mechanical properties and thermal conductivity are different to cast acrylic. Extruded acrylic is more than 10% more thermally conductive and that means it absorbs heat faster and therefore retains heat in the kerf wall much longer. Therefore you can use full air assist (or not) from the thinnest material and you will still achieve a crystal clear edge.

These are just a few interesting details about acrylic cutting. There is much more to know.
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[MichaelAnson]

On your channel, you have taught me a lot, thank you from the bottom of my heart!

[rmvmdxb]

is that CAST Acrylic or Extruded Acrylic?
I have a 100W laser and had a very very difficult time cutting 6mm CAST Acrylic.
…Is it possible that my maybe I need to change my Focal Length lens to make this work?

[waleedantar]

Just question, is the laser can cut the clear acrylic without any painting on the side of acrylic ??

[darshilpanchal]

Can Co2 4KW Sheet Metal Laser Machine cut these kinds of materials?

[sadeemalshaban]

thank you so so Mach for that information

[demodelbouwloods]

very usefull information, wich lens do you use? (focus distance)

[dawnbreaker]

Can you please explain weak and strong in numbers or values ??? How many psi (bar) is weak or strong ??

[waleedantar]

I reading about laser S9 this info "90W Effect Beam Shaping Technology: S9 uses the latest 5.5W beam shaping technology diode " and I don't know why the two deferent value of watt in this info ?

[TheScaleBuilder]

Am i able to get some help for cutting some christmas stuff? i am getting flashback and white smoke on my acrylic when im cutting it. i have air assist and im using an upgraded pump, not a compressor. I always get white smoke on my acrylic i can never cut like this

[dwaynevarnell]

Tried this on the bolt and at 90% power and 3mm/sec. not sure how hard the air is blowing but turned it down but still jagged edges. .23" thick cast acrylic clear.

[santosherram]

Thank good Information
What is blow can you explain pls

[zozoart]

I went to sight and just moved on real quick when I don't see any pricing.

[johnbugman]

When I cut 1/4 acrylic I see lines on the flame polished edge any way to stop that? It looks like many lines spanning top to bottom it’s not a smooth edge . It only happens on the y axis

[matteoaprea]

Thanks for the informations! But is there a way to prevent tiny raised edges while cutting extruded PMMA with a C02 laser? I'm cutting a 3mm sheet and the final piece turns out to be 3mm + the height of the raised edge (both sides!). I'm crafting a box and for finger joints is not the best because I have to manually polish every "male" with a metal spatula!

[wilgbn]

I am using a 120w CO2 laser to cut PMMA, our aluminium grid tend to leave marks on the PMMA when the laser hit the grid, does the honeycomb grid works better ? Thanks :D

[chiudavid]

What is the thickness in rhr demo? Thanks

[spideyprince]

I only have a 10W Xtool M1, how can i cut Acrylic clean? More Passes and also Slow will it work? Thank you!

[jeffstewart]

I TRIED CUTTEIN CLEAR PLEX THIS WINTER. TH SURFACE IS GETING A FOR SEALED IN TO TH SURFACE DO YOU KNOW WHY?