MDF Feed Rates?

[clamps]

I'm trying to figure out an optimal feed rate for cutting 3/4" thick MDF.

Currently, my machine uses a Hitachi M12VC with a up spiral 1/4" end mill. I've tried quite a few combinations of rpm, feed rate and pass depth. All to varying degrees of success. I'm curious what others have tried.

Sorry if this is a repost subject, pointing me in the right direction is much appreciated.

-clamps

[FandZ]

It's going to come down to the stiffness of your machine. I have a weak Z axis so I can only take cuts of about 50 ipm at a .07 depth. That's on the sad side but I'm happy. Any deeper and I end with bad edges. Others can do it at 125 ipm and in 2 passes. I think the best formula for your tool life is going to be the deepest you can go at the lowest RPM and fastest IPM. The bigger the MDF particles you create the longer your tool will stay sharp. Bigger particles will take more heat with them keeping your tooling sharp. Too low of a feed rate and your just dulling your endmill because of all the friction. That's how I understand it.

[clamps]

It's going to come down to the stiffness of your machine. I have a weak Z axis so I can only take cuts of about 50 ipm at a .07 depth. That's on the sad side but I'm happy. Any deeper and I end with bad edges. Others can do it at 125 ipm and in 2 passes. I think the best formula for your tool life is going to be the deepest you can go at the lowest RPM and fastest IPM. The bigger the MDF particles you create the longer your tool will stay sharp. Bigger particles will take more heat with them keeping your tooling sharp. Too low of a feed rate and your just dulling your endmill because of all the friction. That's how I understand it.

FandZ : Thanks for the feedback. That is what I've been finding. Right now I've been running fairly fast: 80 IPM at only 0.125" depth cuts. I may try backing off the RPM next.

I'm quite surprised with how cool the end mill is staying. After running it for 10+ minutes, when the tool slows to a stop, its only mildly warm to the touch.

Yes dulling is my biggest annoyance at the moment. Its making running the machine quite expensive. Optimizing tool life is my goal.

Thanks again for the reply.

-clamps

[ger21]

FandZ : Right now I've been running fairly fast: 80 IPM at only 0.125" depth cuts. I may try backing off the RPM next.

That's actually very slow. My machine also has a bit of flex in the Z axis, so I limit my depth to .125-.188 per pass. I cut at 135-150ipm, and about 12,000 rpm. I get pretty decent tool life. 150ipm is as fast as my machine can go, or I'd cut faster.

Depth of cut really depends on how rigid your machine is, as well as the power of your router. If your machine can take it, try cutting the 3/4" in either 2 or 3 passes at at least 125ipm, and 10,000-12,000 rpm. You should get much better tool life.

[FandZ]

fe. 150ipm is as fast as my machine can go, or I'd cut faster.

Gerry, how many starts are on your lead screw? I'm thinking about upgrading to a faster screw on my next machine.

[ger21]

1/2-8 2 start.

[randyf1965]

What kind of endmills HSS or carbide? I used a few HSS but found they dulled fairly quick. Switched to solid carbide, they seem to last forever.

[posix]

I've done some tests today cutting a slot, 1000mm/min at around 10000rpm using a 4mm spiral upcut (albeit with a rather "slow" helix, better for steel than mdf) at 3mm depth and I've created the worlds first zipper out of mdf! hehe, the little hairs from both sides of the cut slot intermesh so nicely it looks like a zipper. no this is too slow I'm thinking. the finish is horrible, all dust has remained in the cut, nothing has been evacuated which is odd.
mdf is a pain to cut cleanly.

[ger21]

I cut at 3500mm/min at 10,000 rpm with a 6.35mm upcut spiral. You always get some dust in the cut with MDF, unless you blow compresses air on it while cutting. The smaller the bit, the worse it'll be.

[FandZ]

Another odd thing about MDF, I swear each sheet of MDF cuts differently than the next. I'm useing the same tooling, speeds etc, and the edges are coming out nearly perfect. Last board of mdf I got required me to hit it with a sanding block around the edges with every piece.

[clamps]

Is there a definitive way to tell the "sharpness" of a tool?

The end mill I've been using feels sharp to the touch, but it is clearly making different sounds through the same cuts I've been making and I think slowing down the router during fast straight passes.