delrin. how fast is too fast?

[justanotherguy]

Here at the sign shop, we wanted to try and machine a large piece of delrin...
But we are unsure of how hard to run the router.
5/16" cutter, low helix...max 24k spindle...
We figured 15k at 60 IPM, one diameter deep would be fine, multiple steps to finish.... but the manager wants a fraction of that.
Whats the point of a high speed machine if your going to run it at a .001" chipload? (well something close to that....)
Where to start for speeds and feeds?
Thanks for reading,
frank

[Caprirs]

YouTube - CNC machining delrin
Here's a video of a delrin part I made for a customer. Max rpm is 7500 in this program. I think the feed was at least 100ipm.

[DSIF]

10,000 to 15,000 RPM at 80-120 IPM roughing. Blow cold air on the cutter. Take less in Z,~.200 per pass and work from the outside inward. Delrin will chip off the corners if machined from inside to outside. Leave ~.010 for cleanup in XYZ and go about 40 IPM. Tool must be sharp!
Dan

[justanotherguy]

Thanks guys. I imagine a roughing pass is key to a good finish, which is a major goal. Even feeding it slow you can hear the chips rattling around in there.
and I mean slow.
100 ipmR and then even 40 ipmF should save a ton of time and still give a good finish...