cutting data for Delrin and High Molecular Weight Polyethylene

[carlnpa]

Jedi-
I'll try to help with specific mill selection.
What size parts are you tring to make?
What is your spindle rpm(range)?
What size collets do you have?
What milling operations, surfacing, pockets (need corner radius), cut out?
What is the maximum depth of cut?
Can you change tools during the process?
How will you hold the part?
In general cutting plastics is all about the cutting tool, specific cutting tools.
The good ones will have a sweet spot but tend to work over a wide range of rpm and feed speeds.
You must always be moving while in contact with the part, no movement will instantly cause the material to melt and gum up the cutting edge.

In inches small mills
Onsrud 40-101 and 40-101L 1/4 shank by 1/8 about $7
Onsrud 40-103 1/4 shank by 3/16 - excellent for plastics $7

[jedioliver]

Hi guys,

Thank you once again for your help.

Paul, it seems that a 45° helix is better than a 30°. I think I will try them as it seems to be more efficient.
Did you already use such mills? What is your opinion?

BTW, I also red that some helixes are going downside. It seems that the chip goes donwside with such mills. Does it really offer an advantage?

Carl, here are the answers to your questions:

- parts are going to be from 10x10x12 mm to 150x100x35 mm.
- spindle rpm: from 8000 to 24000
- size collet: from 3mm to 6 mm (from 0.11" to 0.23")
- milling operations: all you can imagine...unfortunately...lol...
- depth of cut max: 40mm (+/-1.6")
- I can change the tools, no problems
- the parts is on the 4th axis wich can be indexed or continuous


From your comments, I think I will choose the following end mills:

- 1 flutes, 30° helix, center-cut, upside helix
- 2 flutes, 45° helix, center-cut, upside helix

I am waiting your comments on downside helix. I planed to buy 1 flute and 2 flutes mills with such helix in 30°.

Feel free to contact me if needed.

Thanks ones again.

Olivier

[pced]

If anybody needs help with machining plastics, please check out my website www.cncplastics.com Lots of great technical info. Physical properties and machining information. You can also call us at 1-800-265-7351 for small and large quantities of plastic rods, plate and cut to size blocks.

[Paul_S]

Paul, it seems that a 45° helix is better than a 30°. I think I will try them as it seems to be more efficient. Did you already use such mills? What is your opinion?

I have typically used 2 flute 30° helix HSS or carbide cutters cutting delrin.

[I have used 60° helix 3 flute for roughing and finishing a 1/4 dia post in 17-4 steel. Using a RobJack tuffy brand 3/16, 3/4 flute cut length. Other brand cutters would just shatter. It would cut nice and straight with little or no taper. If this works this well in steel, plastic should be like butter. Also in plastic that brand would not be required.]

[pced]

Go here http://www.cncplastics.com/PDFs/Mach...l%20Delrin.pdf for detailed info on machining Delrin. Other great info available at www.cncplastics.com in the physical properties section.