Help with face milling...

[peter.blais]

Hi guys, I recently picked up a small 2" 5 insert face mill. Just spent some time trying to get some decent results out of it and am not having too much luck.

This is 3600 rpm, like, slooooow, 12ipm or something... .005 DOC. When I feed it faster, it makes nasty sounds and some chatter.

Heres what I'm getting out of it right now, this last cut on this block I happened to try making 3 passes using about 50% of the cutter. I'm just screwing around with jogging the tool right now so its not exact.

Its funny because it looks to me (a total newb) that I need to play with the head, like the spindle isn't totally perpendicular to the table. However, with large end mills, even up to 1", and this 2.75" shell mill I was playing with, its totally even... Not to mention its a bridgeport Ridgid Ram machine.

Thoughts? Is there anything special I need to do putting the inserts in? People talk about needing a 2-4-6 block or something, but this mill uses a torx screw with a pretty major taper on it, between that and the seat, it seems the insert is basically non adjustable.

[big_mak]

Peter,

Looks like a vibration issue to me. is your part sitting on slim parallels, or supported over the full width of the part?

What material are you cutting? What condition are your inserts in after the cut? Are you using the manufacturers specs for surface speed? Does your machine have a quill? is it all the way up and locked?

With a few more answers to some of my questions, more guys may be able to help you out.

[peter.blais]

Ok... haha, its a little block of 6061. Sitting on 1/8" parallels almost all the way out of the vise. Its an inch thick though.

The inserts look brand new after the cut / a bunch more like it... I don't know what the manufacturers recommendation is for surface speed, the tool didn't come with any info at all. The RPM recommendation is from ME Consultant Pro actually it recommended 3800 rpm and like 133 IPM (.007ipt) but my machine doesn't go 133IPM.

I turned the spindle and feed way down in MEPro and ended up with like 2000rpm and 25IPM, slowing down the feed and upping the RPM seemed to be going in the right direction, going the other way (larger IPT) was definantly worse!

Its a big big powered quill (this is a dedicated CNC machine from the factory), I was running it about 1" extended out of 5", but honestly I never have a problem with the quill even all the way out cutting with the big shell mill I mentioned or large end mills or whatever. I run like this all the time when i'm working with a short end mill and a long drill in the same program and can get excellent finishes.

[big_mak]

From the pics, it looks like the inserts are axially aligned.

How tight are you holding the work? It looks like vibration to me because of the pattern on the top.

Rigidity is a relative term. Your mchine may be rigid, but the work or holding may not be, and they are just as important as the holder and the machine.

Can you take a pic of the cutter? Almost any cutter should be able to cut aluminium with out issues, unless you are using some double negative rake cutter from the stone ages.

[big_mak]

You should make sure you maintain proper chip loading regardless of RPM try to maintain constant chip per tooth.

[peter.blais]

Yea, well, I ran it through at 25ipm which is like .00125 or so per tooth and haha well it rattled / chattered... Slowing down the rpm and leaving the 25ipm feed made matters even worse with gouges into the material a couple thou deep where it looked like the inserts were "bouncing" or skipping across the top. All of this seems to happen on the back side of the cut where there is no cutting going on.

Here are a couple pics of the cutter / inserts...

[big_mak]

Is the pullstud/Drawbar sufficiently tight? What about the spindle, have you put a dial on it and seen how much you can push it side to side by hand?

[big_mak]

Upon a closer look at the pictures, it looks as though the cutter is being pushed up as you get into the cut, and are engaged in the cut, and as the pressure relieves at the exit side of the cut, the spindle drops gradually causing the mill to back cut, giving you the waves.

IF you are only removing 0.005" try removing all but 1 insert, and turn the mill into a flycutter of sorts.

[peter.blais]

I haven't put a dial on it, you can-not-move it by hand haha and it has fresh bearings and such not long ago at all. It would really surprise me if there was too much run out on the spindle because honestly I can get great finish out of any other tool around here except this damn face mill lol. The shell mill I tried didn't do anything wierd and it was a whole lot bigger, in fact I could kinda hog with that thing, but I didn't like the way the teeth were ground it left excessive tool marks IMO if you took a large IPT with it.

[big_mak]

I may not be radial play, but axial play in the spindle as the movement would be in the Z- Axis

[big_mak]

Did you try the Fly cutting thing for the hell of it?

I use this trick at work alot when I need a pristine finish. We are using relatively young(less than 10 year old) Matsuura machines with Hertel/Kennametal face mills for aluminium.

[peter.blais]

No, and thats exactly what i'm after, I'm trying to use this to basically machine some gasket surfaces to a mirror shine. A mirror finish also helps move parts off the shelf when you are retailing them (like I am), regardless of function.

I'm gonna run out and try that right now will post results in 10 minutes or so.