Side machining UHMW

[MechanoMan]

I am turning a UHMW cylinder on a 4th axis for side machining with a 1/4" carbide 2-flute.

I am having trouble with these fuzzy "sweater sleeves" of UHMW material on the outside as it goes. It actually peels up off the cutting zone and rolls off sideways in an intact sheath and pushes off into the uncut region further and further. It's just that- a fuzzy sleeve and it just grows longer and longer onto the uncut area, the cutter won't remove it in normal cutting. Until the built-up sleeve stops on the chuck, builds up more, and then the cutter runs into it and it starts tearing up it long chunks which can wrap around the cutter.

I've got the rotary table on the left, feeding clockwise as viewed from the right onto the table face, and the cutter spins clockwise and is run on the far side of the work from right to left. I could change that by turning it counterclockwise and placing the cutter on the near side instead.

I selected the current configuration because I figured the chips would eject better as the bulk of them formed on the left and then were immediately thrown out to the far side. And I was concerned about the chips maybe mucking with the finish if they were circulated underneath across the finished surface.

But the "fuzzy sweater" thing, would that go away if I changed cutting sides? Looking at the situation it seems like it would get ripped into the cutting zone and couldn't roll off an attached sweater like this. Would it affect the finish?

[DareBee]

Not sure what your 4th axis turning scenario is exactly.

But the rules are more DOC, more feedrate and use HSS cutters (ground really sharp with Hi Pos edge)

[Geof]

Brand new cutter is what UHMW needs. Years ago it was difficult to find carbide cutters with the really sharp edges and HSS was the best but now some of the micrograin carbides with a high helix and very sharp edges made for aluminum will work very well.

You should also use climb milling.

[cut more]

I machine a lot of UHMW on my machining center. I get a gloss finish using either Micro 100 1 flute or Onsrud O-flute carbide cutters.
I have also used Onsrud's 1 flute straight fluted cutters and they work well too.
~ 700-800 FPM works well for me.

Hope that helps,
Cutmore

[MechanoMan]

It's a UHMW cylinder being turned on a 4th axis. The cutter is solid carbide, which as far as I know is sharper than any HSS. The cutter is new.

The cutter is doing side cutting. It's run down the far side of the cylindrical stock and the whole side of the bit does cutting as we turn the cylinder, as opposed to placing the bit on top of the stock and only cutting with the tip. Direction of turn and cut are as listed above.

It's not a finish problem. Actually the work has a nice finish. It's the buildup of unseparated, very thinly attached UHMW material down the side. This seems to be unique to side-turning cutting.

[Geof]

Originally Posted by MechanoMan ... The cutter is solid carbide, which as far as I know is sharper than any HSS....

This is not always the case. Micrograin carbide cutters that are uncoated can be a sharp or sharper than HSS. Coated carbide cutters may not be as sharp as HSS. Carbide insert cutters are almost certain to be less sharp than HSS unless they are uncoated micrograin ground for aluminum.

[MechanoMan]

Solid carbide micrograin- this one (#20401 to be exact). Not carbide-coated steel.
And BTW, it's $12 and all, but it's a damn good cutter.

The program is also spiraling in at like 40 tpi, not doing one circle and stepping to the next one.

The problem is not one of sharpness I realized. The cutter's helix is doing an upcut and the way it's being fed keeps peeling the edge away from the cutter. I'm really thinking reversing the side and turning direction is the only way.

Hmm actually I forgot I HAVE done some wood, oak, with this cutter. No metal though. And not much. I use a couple of shallow cuts in a wood scrap dowel to calibrate the Y-axis and compensate for the skew between the rotary axis and the X-axis.

[cut more]

MechanoMan,
let me see if I have this right,
Your 4th is oriented horizontally, your cutter is vertical,(basically lathe -like)
What size is your cylinder?
Could you stand the part up and interpolate it vertically? Maybe then you could cut deeper per pass.

I have used these Onsrud cutters cutting full length and I haven't found anything that gives a better finish than these. I use them on aluminum too and the bottom finish in pockets is mirror-like.

https://www.onsrud.com/oc/pdf/Super_o.pdf

Regards,
Cutmore

[MechanoMan]

Well, the side-cutting was an experiment.
UHMW cylinder 3", reduced to ~2"-2.5". Cuter 1/4".

The side cutting seemed favorable because:
1. It's insensitive to Z-axis variations. The rotary table mounting plate was discovered to be a problem in that tightening it down warps the plate and tilts the rotary axis upwards in the Z direction. Probably not a big issue.
2. Seemed like it would create a good finish (and it did)
3. Wanted to make use of this expensive cutter I already damaged the tip on when some metal work got loose (side cutting doesn't use the tip at all)
4. It's easy to write G-code for, and I was doing this by hand
5. Wasn't sure if I was gonna have enough Z-clearance to machine this on top

I did variations. With the cutter on the near side and the stock turned CCW, the finish on the right side- which is the end product surface- is awful. Fuzzed over. I put and end to it in the roughing stage and went back.

With the cutter on top, there's no fuzzy caterpillars left on either the unfinished stock surface or the finished work. Interesting!

[HelicopterJohn]

Hi Cutmore,

I can't get this link to work???

[QUOTE][/Qhttps://www.onsrud.com/oc/pdf/Super_o.pdfUOTE]

John

[cut more]

HelicopterJohn,
I just tried that link and it seems to be down. Maybe try it again later, I did a search for Onsrud super O flute and came up with this.

http://pdf.directindustry.com/pdf/on...604-34213.html

I use these on aluminum too, they give a fantastic finish on the bottom of pockets and you can really rip aluminum off in a hurry.

MechanoMan,
How many of these do you need to make?
I have a pile of ~5" diameter x 1.3" thick UHMW disks if they could be of use.

Regards,
Cutmore