Feed Speeds for MDF on PRS Standard

[jdervin]

I was cutting 3/4" MDF on a PRS Standard at 3ips when half way through a file, the Gecko driver for the Y axis failed (fortunately, SB tech support helped me get it fixed). I asked what they felt the top speed should be and they suggested that 3ips is near the limit, but that it should be able to cut it. In addition to the driver failure, the noise from cutting was screaming loud. I'm wondering what speed other PRS Standard users are cutting MDF at and would appreciate any insight.

These were my settings:
PRS Standard with HSD 4hp Spindle
3ips
1/4" End Mill (Onsrud 52-910)
Stepdown = .25"
Chip Load = .006
Spindle RPM = 15,000

[Gary Campbell]

John...
Techs are correct. 3ips is near the limit, but some have gone faster, you will have to perform some speed tests to see what woks on your machine. I wouldnt reccommend going much faster due to the Standards inability to stop if you push it over its limits. If you get good cut quality, you may be able to cut at those speeds full depth as MDF doesnt load the bit much. Due to this light loading try reducing the rpm, this will reduce the scream AND let your bit live longer.

For comparison, I could cut with a 3/8 bit, 13500 rpm full depth at 10 ips with an onionskin added for small parts.
Gary

[meatbal80]

I also have a standard and was doing some computations this is what i came up with.
- full depth cut in mdf or ply
- cutter - 1/4 inch single flute compression
- rpm - 21000
- cutting speed - 2.8 inch a sec (168 inch a min)
- chip load - .008

Reading all of the information i could get from onsrud and speaking with their tech support everything looked good. I compensated the chip load based upon cut depth being 3 times cutter diameter. Does this make sense and sound plausable? I dont want to do any damage to the bot or break a cutter, this just seems counter intuative with my general wood working back round.

[Gary Campbell]

Joel...
I have not used that single flute compression, but do know they are a good solution when conservative move speeds are mandated, such as with the standard. I also think that MDF and plywood will take significantly different rpm settings as you should be able to keep the feed speed at 3 ips. I personally would try rpm in the 12K to 15K range, make a 1' cut and measure the chips. Turning a bit at 21K will smoke it in a few seconds if you slow down for corners, etc.

I didnt understand which aspect of your post is counter intuitive.

BTW, I do believe in chipload, it makes the bit last a long time. Here is an example of .015 chips:

[meatbal80]

Gary,
Thinking of pushing something harder to get a better result just has been a little hard to wrap my mind around.

Joel