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Thread: Machining Sticky Aluminium
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15th Mar 2011, 02:06 PM #1
Machining Sticky Aluminium
Hi All,
Apologies if this has been covered before, but lately I've been stuck with a batch of aluminium bar (it's an extrusion) that is proving difficult to machine cleanly.
I don't know what the alloy is, but it doesn't want to form chips at all, it just winds around the cutters and gums up the flutes.
I've tried a few different cutting lubricants, doesn't seem to make much difference.
I've just snapped a 1/4" slot mill, because it gummed up and stuck.
I'm looking for any hints that might help?
Regards
Ray
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15th Mar 2011, 02:36 PM #2Most Valued Member
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Have you considered useing air to keep swarf away from cutting edges.
Have you considered useing an end mill instead.
Is the cutter suited to aluminium.
Does it react different if you change DOC feed or RPM.
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15th Mar 2011, 03:18 PM #3
Hi Pipeclay,
Thanks, I'll try all those suggestions and see how it goes.
The cutter was one from CTC,
2 FLUTE HSS AL SLOT DRILL CUTTER - METRIC (1 PC) #E25
Regards
Ray
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15th Mar 2011, 07:10 PM #4
Hi Ray, I have used carbide bits for wood, those cheap ones with 10 or 12 in the case from Bunnies, to cut that type of aluminium in my macro mill, with great results
Check the photo, that's a QCTP for my Taig lathe, it has a 3/8 dovetail on the body and a 1/4 inch slot on the tool holders,
cheers, Richard
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15th Mar 2011, 08:16 PM #5I break stuff...
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Perhaps a roughing endmill might help? Should break up the spirals as they form? From your description I envisage spirals working their way up the flutes like when you drill a hole with a normal drill bit?
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15th Mar 2011, 08:55 PM #6Novice
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Hi Ray,
I know just the stuff you are dealing with. I had a "very nice" 6" Diametr peice about 10" long that came directly from alcan.. It would build up on and around the cutting tool on the lathe eventually re attaching to the work piece. tried all different cuts on the HSS tools, carbide inserts, speed combinations and coolant to no avail. I suspect it may have been pure aluminium from the pot mills.
Ended up giving it away as a bad joke.
Go and buy yourself a nice piece of 6061.
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16th Mar 2011, 02:25 PM #7
Hi All,
Thanks for all the suggestions, after a bit of mucking about, and trying a few different things, The best results are when the swarf doesn't stick to the cutter, so shallower DOC means the swarf is smaller, but still sticks like glue to the cutter tips.
Changing lubricant, kero works pretty well, but metho is the best so far, I had tried it earlier, but it seems the trick is to keep plenty of it up to the cutter.
Regards
Ray
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16th Mar 2011, 04:55 PM #8
Hi All,
Here is a picture of results with different lubricants, the trick is to stop the swarf from sticking to the cutter, once it's stuck in the flutes you have to stop anyway.
8mm cutter, 2mm DOC, 1600 rpm, same feed rate for all cuts.
From left to right
1. No lubricant, no swarf sticking either but the right hand side is cleaner.
2. Metho, sufficient to have a pool of metho around the cutter at all times.
3. Kero, sufficient to keep pooling around the cutter.
4. Trefolex, the gooey clear liquid stuff, not the black greasy stuff.
It's pretty close between metho and kero, with metho slightly smoother.
Right hand cutting side seems to be always better
Regards
Ray
Edit:
Hi Richard,
I haven't yet tried router bits, nice idea, some of the more complex profiles would come in handy.
From the looks of your QCTP they certainly work well. Looks good. Nice work.
Regards
RayLast edited by RayG; 16th Mar 2011 at 05:21 PM. Reason: Fixed left and right
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16th Mar 2011, 05:20 PM #9Most Valued Member
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Ray
Will your mill go any faster? My maths says 3800rpm, not sure in this case if it will help.
Stuart
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16th Mar 2011, 05:44 PM #10
Hi Stuart,
The standard HM52 maximum at 50hz is 2400 rpm, but I did run 3200rpm with the vfd upper limit set to 100hz and the belts configured for 1600rpm.
Much rather dial up the frequency than change belts..
I didn't really see much difference at the higher speed, but I take your point, aluminium can be cut at a much faster sfpm as a general rule.
Regards
Ray
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16th Mar 2011, 06:05 PM #11Most Valued Member
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"Much rather dial up the frequency than change belts" So lazy lol
Yeah I didnt really think it would help, should have known you would have tried it already.
Stuart
p.s. you've just given me an idea but I'll put it in a new thread.
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16th Mar 2011, 07:52 PM #12
Hi Richard,
Just as an experiment, following your advice, I tried a a few cuts in Aluminium with some cheap router bits, they work beautifully, nice finish, and no sticking. I just did an edge with a cove bit. Beautiful. Lots of metho and climb cutting.
I can see great potential for some up-coming projects, fancy beading and coves on all the projects from now on.
Here is a straight cut with a cheap router bit for comparison with earlier trials.
The router cut is the one on the left. I think the straight flutes are cutting cleaner on the edges than the normal milling cutter spiral flutes.
Thanks for the tip.
Regards
RayLast edited by RayG; 17th Mar 2011 at 01:40 PM. Reason: spelling
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17th Mar 2011, 12:29 AM #13
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17th Mar 2011, 07:50 AM #14Most Valued Member
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20th Mar 2011, 10:48 PM #15Senior Member
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Hi RayG,
Once you have cut your slot with the slot cutter running in a clockwise move the material over just a few thou and run the material in the opposite direction (climb milling) with lubricant being sprayed on the cutting area - you should end up with a near mirror finish.
Regards
MH
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