Best Bits and Techniques for Cutting Acrylic - Ask a Tech #57

Some useful tips for cutting plastic (acrylic) using a router or CNC machine are discussed in this video.

Some Tips:
Freeze material for an hour before cutting
Use ice water in spray bottle to cool cutting
Larger diameter bits are better at cutting cleanly
Special acrylic cutting bits perform well
Acrylic come as cast or extruded. Cast cuts better!
You can use the flame method on the edge of cuts to smooth them over.
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Your Name: Petur
Title of Question: CNC

The Question: Hi, I´m using router table and hand held router to cut acrylic mostly 5mm, what bit is best for good result (smooth edges).
Regards, Petur.
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Links to pages show in video:

Best Bits and Techniques for Cutting Acrylic - Ask a Tech #57

All Materials Found Here (c) The Guru Brew Tech Web Show

[TunaSoda]

First thing is to figure out what type of acrylic it is, either cast or extruded. Cast cuts much better on a cnc. I cut mine just fine using 18000rpm/35ipm with short pauses in the gcode between cut runs. I just cut some 0.227" router plates yesterday that came out clean in two depth passes. (This was a 1/4" shank 1/8" cutter) Now making those cut edges clear and smooth is another story in itself lol

[siamaklighvani]

I think if you pass in stages there is less load on the bit and acrylic sheet, for instance if the thickness of your sheet is 10 mm . First you cut 2 mm them 4 mm 6, 8 and at finial extend the bit to 10 or 11 mm and finish up the job.

[acerjuglans]

For cutting plastics with a router bit, you want to avoid creating heat as much as possible. You need to move fast with the router (called feedrate), and you want to turn the spindle rpm speed low. You'll also want to take shallow depths of cut, especially with harder plastics like acrylic (something like PVC is more forgiving).

Youll need the appropriate router bit, usually a diameter of 1/8" or 1/4". It needs to be an "O-flute", upcut spiral endmill, usually with 1 flute/cutting edge.

[BGP]

try an upcut, slow the RPM down and dont cut too deep. Make shallow cuts and take breaks between cut passes. You could also rig up an air compressor to jet out air into the cutting area, which will help cool down all surfaces. I would avoid any straight bit as its too aggressive for fine cutting. I use a Tommy Global TG1113 and it seems to work fine for both Acrylic and Wood. Am considering a compression bit to skip the upcut burr though, so i dont have to worry about doing precut scoring, which is quite annoying.

[williampowell]

Hi Guys,
we sell routers and cutting tools and by far the best tool for acrylic are upcut spirals.  In the states I guess the LMT Onsrud 65 series Super O with polished flute will be a good investment. Cuts cast and extruded beautifully. Bill - Maxicam UK

[xxkissmeketutxx]

Great tips and video, from Australia, thanks for posting

[arizonacustomwooddesigns]

Thanks! Very helpful.! I cut this stuff on a table saw but I have a guy that wants me to try and cut mirrored acrylic, with curves.

[tomjdesigns]

its second time when your tips helped me, top man

[Val_Halla]

That only happens with extruded acrylic. Cell cast cuts much better and no melting.

[hopower]

When cutting plastics if you get a cheap flood coolant system all your problems will go away, plus I use Harvey Tool cutters for plastic and they are so sharp that you have to actually be careful when handling them as they will cut you.

[joseluisruiz]

I know this video is a few years old but its still very helpful. I started cutting ABS plastic at 1/4" thick and found that the 1/4" Spiral Flush Trim bit i bought from mobile solutions seems to somewhat get stuck. For example it tends to want to push the abs sheet away from me vs wanting to cut it. I am using a Dewalt DW618 router and have tried the first 3 speeds on it and it seems to give me similar crappy cuttinf results. I tried this bit with 1/4" wood and it cuts very smoothly so I was wondering if Acrylic would be much better to cut with a router. On the website for mobile solutions they claim that the bit I purchased is made for Plastics/Abs but its excellent for wood. Im wondering if it really does work well. Im new to all of this and started custom making stuff for my vehicle car audio gear like speaker brackets etc. So thats why I went with ABS but wondering if I should try Acrylic or get a 1/2" thick Spiral bit and see if that one would cut better. 🤷🏽‍♂️

[adenmhed]

Thanks for these fantastic tips ! . Dealing with extruded acrylic is really annoying but it's price compared with the cast acrylic makes it desirable for me :) . I usually use cooking oil during my CNC cut, mill or engrave that's will cease melting and gives a better crystalline look . 

[simonlyons]

Useful vid, thanks.
Shame the professionals at Professional Plastics can't spell 'Plexiglas' :-O

[ChickenJoe]

Thanks for the info. Any tips for cutting 1"+ thickness acrylic?

[VintageGearMan]

May be off topic but no mention of cutting lexan. Same deal?

[mariamonroe]

Do you recommend cutting 3/8 thick acrylic with a jigsaw?  If so, what size blade is best?

[eric]

Feed rate and RPM would be helpfull with your 2 flute up bit. what have you found to work?

[flyingdutchman]

Thank you very much for the help! Great video!

[antigen]

you can avoid the 'welding' due to overheating by using a slow speed

[Sabi-Math]

Am new to this business, i try cutting or engraving an acrylic but i the spindle goes up once i click on cycle start. Please sir what do i do ?