Fine Finish aluminum

[Incogneeto]

Hi All,

We do mostly cast aluminum projects thin walled and Facing, Lots of bearing finishes. I generally don't have an issue with the bearing surfaces But on the others I generally end up with a 62 or 125 finish. using standard Flat end mills ( Face mills are not really conducive to our work) Any Ideas on tooling, speeds or feeds to get that aluminum mirror finish?? Top speed on our fastest spindle is 16000 and the rest 8000. Tried a bull endmill and it did not look any better. Feedrates usually from 36 IPM to 50 IPM.

We use Encool for coolant. Like I said generally Facing small areas. Any suggestions are appreciated.

Thanks Dave

[jeff]

Depth of cut and feedrate are also factors in getting a good finish.

36-50ipm seems really slow for 16k rpm. (what dia endmill?)

Maybe a small dia insert cutter with a bright polished insert will do the trick.

[Quickmike]

I wonder if it may be the material. Maybe the casting has a little porosity

[Incogneeto]

Thanks for responding. Yes it has porosity But My Bearing surfaces usually pull at least a 32 finish.

 

I wonder if it may be the material. Maybe the casting has a little porosity

 

Depth of cut and feedrate are also factors in getting a good finish.

36-50ipm seems really slow for 16k rpm. (what dia endmill?)

Maybe a small dia insert cutter with a bright polished insert will do the trick.

Depth of cut generally is .05 total at the most and because these are usually difficult to fixture they may have High walls but usually less than 1/2" across on the Face. They endmill likes to drag and I don't want to rip it out of the fixture.

[Newbeeee™]

Dave - it maybe better with a sweeper geometry? Sometimes this can work well.

Also we've had good luck with a diamond insert before - but this was on 6000 series mtl.

[civiceg]

What is your normal finish pass step down ? 

[The Cathedral]

If you're talking face, ideally you want something that only has one cutting edge. A fly cutter or a facemill with only one insert. You can also get one-flute non-center-cutting endmills for small diameters. When you have more than one flute, any variation in the grind or how far the inserts stick out will affect your finish and there's really nothing you can do about it unless you buy ultra-premium tools. The same one-flute endmill works good for walls as well. The biggest trade off is time since you have less cutting edges. Since it's aluminum, as long as you have a very good coolant flush, you can get away with running the tool at a high sfm and low feed to kind of burnish the part. Just be careful of galling and make sure you use an uncoated endmill.

 

Then send it out for electro polishing.

[Incogneeto]

Probably Better if I just show you. I am only machining the top face and the Boss down in the Bottom. These are sealing surfaces so I want a very clean finish. I'm pretty sure this is 2024 aluminum cast. I'm doing both sides just the faces and 1 bearing surface on the Bottom. The bearing wall is not an issue it's usually 32

[Incogneeto]

Tried sending you the File I'm working on now But it's too Big. It has a much larger face area. 5" x 7". But I would like the same result. As you can see By the part I sent fixturing and holding the part is not conducive to a large say 3" face mill.

Thanks for all the support.

 

Dave - it maybe better with a sweeper geometry? Sometimes this can work well.

Also we've had good luck with a diamond insert before - but this was on 6000 series mtl.

 

If you're talking face, ideally you want something that only has one cutting edge. A fly cutter or a facemill with only one insert. You can also get one-flute non-center-cutting endmills for small diameters. When you have more than one flute, any variation in the grind or how far the inserts stick out will affect your finish and there's really nothing you can do about it unless you buy ultra-premium tools. The same one-flute endmill works good for walls as well. The biggest trade off is time since you have less cutting edges. Since it's aluminum, as long as you have a very good coolant flush, you can get away with running the tool at a high sfm and low feed to kind of burnish the part. Just be careful of galling and make sure you use an uncoated endmill.

 

Then send it out for electro polishing.

 

What is your normal finish pass step down ? 

I usually don't do a finish pass as the most I take off is just clean up or .050.

[Newbeeee™]

Try a 5 thou finish cut with a real sharp 45deg 3 flute geometry tool.

Then do the same with a sweeper edge.

I know the automotive guys just used pcd - its a bit of experimentation with castings.