Help needed for ABS machining

[suspension]

I am a new to CNC machine and my first project was to machine a small plastic enclosure for a (possibly commercial) product I am prototyping now.
As the materiel I used 5mm thick ABS board bought from ebay. (Please search ebay.co.uk for '5mm White Smooth ABS Sheet A6 A5 A4 A3 Acrylonitrile Butadiene Styrene Sheet').

I used a cheap HSS 4mm end cutter with 4 flutes for most of the machining except the two pockets.
For pockets I used 1mm 2 flute carbide cutter. I used GWizard to calculate feeds and speeds.

I faced three issues during milling.

1. With 4 mm cutter there was lot of burring and even melting. I had to stop the machine and clean the cutter multiple times.
2. The surface finishing was very rough and does not look nice
3. The side cut edges were rough as well (From the side)

Please see some pictures below.

What have I done wrong here?

Thank you
Sus


http://www.cnczone.com/forums/attach...d=333902&stc=1

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[awerby]

What kind of a machine are you trying to do this on? Something you built yourself, or a commercial unit? What kind of spindle are you running the tools in? What feeds and speeds did you try? How were you holding onto the workpiece, and did you notice any movement in it as the cut progressed?

ABS is a rather low-melting thermoplastic, so too much spindle speed will cause the material to soften and stick to the cutters, especially if you're trying a deep cut with slow feeds. Single or 2-flute cutters will work better than 4-flutes, and light fast cuts work better than slow heavy ones. You generally want to use the largest tool you can to get most of the material out of the way, before getting in there with small cutters to remove the last of it as a finish cut. Air cooling helps a lot when cutting thermoplastics, preferably with an air chiller powered by a compressor.

[suspension]

I used a latest Chinese built 6040 CNC.
Spindle is 2.2KW water cooled one that came with the machine. I tried the feeds and seeds suggested by GWizard. It suggested high RPM's like 17000 to 24000 as speeds and around 450 mm/m as the feed. I never noticed any movement of the piece while machining however.
I will try your suggestions in my next try. thank you for the information.
Do you have any suggestions for compressors and air chillers for hobbyist work? Preferably in UK?

Thank you.

[warrenb]

Use single flute cutters. Onsrud has nice cutters for plastics. You'll have to move fast or the plastic will melt right behind the cutters. Ditch the HSS cutters too. Use carbide. If possible put a air nozzle to blow against the cutter.