CNC plexiglass cut problem:
I need to cut 2mm and 3mm acrylic on my DIY CNC machine. The plexiglass rounds around the tool making it thick and destroys the final shape. I tried 1 mm ‘fish tale’ tool with various (12-25k) spindle speeds, 600-800 mm/min. and air cooling. White (milky) acrylic goes ok, but transparent is every time a crap.
Do you have any experience/advice?
Try faster spindle and I use oil to keep cooler…old motor oil or and then a soft cleaner to get oil off…dawn dish soap is best as it will not destroy the nice shine finish…fish tail should be ok as it is what I use as well…small can motor oil works wonders…a buffer will clean out any oil in holes…if need be finish out with Drexel or like tool with small sander head…
I know nothing but I was just reading this yesterday http://m.instructables.com/id/Cutting-Acrylic-With-Your-Industrial-CNC-Router/
You could try running coolant. I don’t know about used motor oil myself. I would tend to stick with a more traditional coolant. Something like an emulsified oil, and water mixture perhaps? If a mess is an issue you can get a mister for coolant. So you are not flood cooling your work, and slinging coolant all over the place either. At the spindle speeds you are running you’d be measuring throw distance in yards with a liquid coolant.
@sszafran Hi, I had the same problem and was able to figure this out on my own because no one else could give me a hand.
You need this type of CNC bit: http://www.ebay.com/itm/5pcs-CNC-Router-Bits-Single-Flute-Tools-4mm-Cutting-Acrylic-17mm-/121343212194?hash=item1c409e7aa2
Some will say “oh those cheap China bits are no good” but trust me, they are good for that price.
Look around eBay for the ones you like. E.G. for 2-3mm you may buy 8-10mm cutting length. I had success cutting the 20mm acrylic with 22mm bit. The spindle speed I was using was like 15K and the cutting speed depends on the material. The 2-3mm I’d cut in 2 passes with speed of 40-70mm per second.
This should work, Let me know if you need any further help.
oh, and you don’t need any coolant or anything else…
Use tabs and low as possible spindle speed.
the Plexiglass are Cast or Extrusion?
Extrusion or XT its a crap to cut, bend etc…
if Cast then good to bend, cut etc…
i used a one flute at 16000RPM and about 1500mm/minute feedrate and cut 6 milimeters thick one pass, i hope help you 
see my page videos cutting acrylic.
Cheers!
I dont cut acrylic but with acetal I use Harvey tools
And I make cut at 140ipm 30k, and the deep 3/32 same size of tools
See video
I have some another video on my YouTube account
Dear all,
Thanks a lot for all valuable information. I will give it another try next days and post my findings.
@Eugenio_Villaverde I use cast acrylic, tried with extruded (which is easier to get here) before but it was just waste of time and efforts.
@Max_Kalin I have no single flute bits lying around so I have to order some according to your advice.
Will keep you posted.
@Denis_Seguin sorry but can´t open your vídeo and am interested. Can you pls check the link. Thank you.
Jose I change the link
@Denis_Seguin Thank you. Great vídeos, i was amazed with the speed of the router. I didnt knew acetal but seems a polymer very similar to acrylic but with higher resistence so cutting results probably will be very similar. Am i wrong? 
140ipm is in/min aprox 3600mm/min
30k is 30 000 rpm of spindle
Jose I think acrylic is more strong of acetal
See this link for more information
And click on plastic
Cutting
http://www.harveytool.com/prod/Browse-Our-Products/Application-Specific-Designs/Plastics---Composites_191/Plastic-Cutting-End-Mills---Square-Upcut-Single-Flute_113.aspx
Hi, after reading last post from YARA, i remembered of this site:
http://accesorios-carpinteria.com/gb/21440-fresas-aluminio-y-pvc.
It´s a Spanish shop where you can see those tools with one cutting side
and they recomend them for PVC and Aluminium.
I was looking up milling bits and saw something saying that the chips disperse heat. It suggested using a single flute bit so the chips would be bigger and disperse the heat faster. I think it also said the cut would be worse. I imagine that any way of dispersing heat should work, but that part is just my guess.
@Max_Kalin I cut 3 mm thick acrylic in one pass at 60 mm minute 12k spindle speed and a 2 mm diameter end mill bit. It comes of nice. I use no coolant and perfect matt finish. I suppose a single flute might give you a smoother finish I will have to try later. Last of all, there are different grades of acrylic some of which are very good to CNC and some are crap.