How to mill-cut PVC with a cnc?

[Chris01]

Hi!
I'm not sure if this post is in the right place, sorry if not.
I have a mii cnc machine for PCB fabrication, it works very well for me.
I have some issue to mill-cut PVC sheet. If I try to cut out a square form in a PVC sheet with a thickness of maybe 1.5mm
the end mill melt the pvc edges.

The rpm is around 6000 and the feed rate is 5cm/min.

I'm new to this stuff so any help how to cut PVC with a cnc this type would be nice.

Thank you.

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[machinehop5]

Try looking here for more information. Good Luck.
https://www.usplastic.com/knowledgeb...contentkey=423

[Chris01]

Thank you for this valuable link.
I don't understand clearly two thinks:

What means this from the link:
Cutting speed up to 500 m/min
Feed 0.1 to 0.5 mm/ rev

Are the cutting speed and Feed rate the same just in different measuring unit?
Cutting speed is in m/min ( I assume there is an error in the original writing because 500 meter/min would be really hard...).
Feed is in mm/rev

I think the cutting speed is actually the feed rate.

I have no cutting speed setup in my app which is the opensource Candle software.

Can somebody clarify this to me?

[machinehop5]

Cutting Speed = SFPM
https://en.wikipedia.org/wiki/Surface_feet_per_minute

Feed = Chip Load
https://en.wikipedia.org/wiki/Speeds_and_feeds

[burbingus]

Hi Chris - I haven't milled PVC but have worked with other plastics and have melted them before. In general, I think you will want a 2 flute end mill versus 4. Also, you want to lower the spindle RPM by a lot. I would guess maybe 800-1000 RPM for 5cm/min. Some of this will also depend on how big your end mill is. Also, try to vacuum the chips out as they're formed if possible. What is happening is that your end mill is not cutting large enough pieces of plastic out but instead is shaving small bits off and creating a lot of heat by rubbing excessively against the material. Increasing your feedrate, decreasing your spindle speed, and using less flutes should help.

Micah