CNC feed Rates

[steveeverson]

Hi Everyone
Just a quick question. What sort of feed rate do you use with a 3mm bit
cutting acrylic or MDF parts (about 3mm depth).
Cheers
Steve

[tomenglish2000]

It will depend on the RPM of the mill.
I cant remember what RPM I use, but it is probably in the region of about 17000 RPM.
I have a 2mm bit, 3 flutes, up cut.

I use 3mm cutting steps and a feedrate of 300mm/pm, but it can handle at least 6mm cutting steps but I tend not to push my luck.

Tom

[Westozy]

Hi Steve,
I usually do 3mm steps with a 3mm endmill at a rate of 200mm/min which gives good results on PVC. For acrylics I would slow it down to about 150mm/min and I cool the tool occasionally with lube oil spray like CRC or WD40. In general use your ears! Listen to the router and if it loses excess RPM and loads up in a cut you will be going too fast. Another good tip if you have a compressor, is to set up an air nozzle fixed to the router with an adjustable airflow. This helps with cooling and clears swarf to see what is happening easier. I am assembling a fence and collector around my machine so all the swarf falls into a collection bin!

Cheers, Gwyn

[tomenglish2000]

Please be cautious about cutting Acylic too slowly. The speeds I quoted are for Acylic. Cutting it too slowly allows heat to build up along the cut which will stress the plastic, leading to paint cracking in a few years after manufacture. Faster feed rates mean that the heat is carried away in the off cut acylic which keeps your working piece cooler.
A friend (who make pro panels) uses a thick solution of washing up liquid in a spray bottle. He puts this on his piece and the off cut chips stick to it keeping them away from the bit, plus this helps cool the plastic. It is also easy to wash off!

Tom

[steveeverson]

Brilliant. thanks for some Great advice gents :D