I am not 100% certain of the feeds and speeds used on the spiral demo, since I only have the gcode handy. Whatever was in there, it pulled the tool out badly (I know it is 8500 rpm). I got through the demo part by cutting feedrate to 50%, which worked well enough.
On my own part, also out of Delrin, I have used a couple of values below.
All if this is done with the Harvey 52508 1/8 single flute for hard plastic milling. Which unfortunately is now broken.
I had some success for a couple of hours of machining with the next parameters, but the tool eventually pulled out about 2mm on 26mm initial extension.
F 15.8 in/min (400mm/min)
FPT. .0008"/t. ( .02mm/t)
Optimum load 0.75mm
Roughing stepdown 2mm
These parameters caused pullout in a couple of minutes:
Optimum load 1mm
Roughing stepdown 4mm
I got better results at the 20k spindle speed, should I push to 35 or 40k?
Is that stepdown/ radial engagement just too high for a v2-50?
I can turn it down 2x but seems so close to the edge even if I do. It makes me nervous sitting a factor 2 away from failure, and even then the MMR goes down very low.
The 20k nearly successful numbers are leads than the Harvey table recommends. They suggest
.0056"/t for Delrin at 800-1200SFM.
.35xdia which is just over 1mm at
1x diameter. Which would be 3.1mm
For my nearly successful parameters, am nearly 8x down in FPT at less radial engagement and stepdown. I get the spindle doesn't have that much power, but still I thought I was being conservative. The spindle sounded fine.
The other thing about my system is that this is a used one I picked up recently, it wasn't that old when I bought it. It looks brand new, was barely used. But I wonder if the CHB collet is ok. If these speeds/feeds seem reasonable, I may try a new collet. I have cleaned this one meticulously.
It would also be helpful to know what others are getting away with, so that I can troubleshoot.
Thanks for any help.