Milling Aluminum without Coolant

Hello guys, i have a diy cnc router that is machining aluminum and i am having some troubles with chip welding at pockets and other operations. I am using a 45° helix mill, 3 flute, polished from ISCAR, it's doing a pretty job, but sometimes it run into trouble. Do you guys have any solution to improve it's performance? I was thinking of a coating.. or going for two flute endmills. I have with me an image and a website about coatings, but i didn't understand them very well, from these coats, does any of them improve ?

http://www.cnczone.com/forums/attach...d=370244&stc=1

This is the website: Titanium coatings TiN, TiCN, TiAlN, AlTiN - HANNIBAL CARBIDE TOOL, INC.

The ZrNbCn seens to be the best for aluminum, it says wet or dry, have anyone here used it ?

What kind of aluminum are you trying to mill. Many varieties of aluminum are very gummy. You can machine 6061 with carbide endmills very easy. Also harder versions of aluminum. Three flutes works great or even two flute with a good helix. I stay away from coated EMs when running aluminum.

Russ

Aluminum 6351 or 6061. Why stay away from coated ones ?

Here is an smart part of an article that explains. The 6351 stuff is often used for pipes and pipe extrusions. The standard 6061 is very common and most people use it because it is typically cheaper, readily available, and machines very nice.

Russ




When machining aluminum at very high speeds, the conventional wisdom of preferring sub-micron grain carbide materials for their hardness and ability to maintain a sharp cutting edge must be reevaluated. Sub-micron grain carbide relies on a high concentration of cobalt to maintain its strength. Unfortunately, cobalt is known to react with aluminum at elevated temperatures, meaning that the aluminum will chemically bond with the tool material. Coarse-grained carbide, on the other hand, offers sufficient hardness so the tool will not dull as quickly.

The second consideration to avoid edge build up is the tool coating. There are many options for the tool coating, and understanding what the best choice is for a particular job is crucial in high-speed machining.

TiN, TiCN, TiAIN, and AlTiN coatings are not good choices for aluminum applications because the coating process has problems with surface roughness and chemical reactivity. The process results in an uneven surface that more easily bonds to aluminum. In addition, the TiAIN coating contains aluminum itself, meaning it will more likely bond with the material being cut.

Tests have revealed that in fact an uncoated carbide tool will offer superior performance to the coatings mentioned above. Other possible coatings, such as diamond and DLC coatings, offer a smooth, chemically inert surface and will extend the life of the tool. Of coarse, while diamond coatings offer the best performance, they also can be quite expensive. In general, DLC coatings offer the best ratio of cost to performance.

I see, that's why most manufactures sell polished as the best option to mill aluminum. And compressed air as coolant ? This is something i can arrange!

CNCMAN172 is right on with the coatings. Ive found either an Uncoated Tool with Polished Flutes or a ZRN Coating are the best options for milling aluminum (the Uncoated Tool will give you the sharpest edges and best part finishes while the ZRN Coating will give you better lubricity for chip evacuation as well as better tool life) and a DLC Coating will work as well but is more expensive and would be overkill.

If you are having issues with chip packing there are a couple of things you could do. The first would be to reduce the # of flutes to allow for more room for the chips to evacuate (a 2 flute end mill for aluminum with a 45 degree helix would be a good option here). But the 3 flute tool you currently have should also work well in the application to prevent chip packing you should reduce your Axial DOC when slotting and reduce your Radial DOC when heavy roughing to allow for more room for chip evacuation. Also, I see the most issues with chip packing when you are coming into corners on pockets as you are doubling the engagement of the tool leaving no room for the chips to evacuate, when you run into this you need to cut your feed rate in half otherwise the tool will fail. Hopefully this helps (if you happen to need tool recommendations let me know)

Mike

I see, thanks for the replies. I'll indeed try to arrange a compressor to use the air and run some tests with polished 3 flute endmills.

You can use ZrN, TiN, TiCN, PVD coatings with aluminum with no issues. You don't want to use a coating that contains aluminum like TiAlN - those are usually used for milling harder materials. Even then I would still advise using at least some minimal form of lubrication.

Also, the high helix angle can provide a great surface on finish passes, but for roughing, the increased flute engagement may cause issues, at least with my experience. Use a standard helix angle for roughing (and even a low-helix for gummier aluminum) and save your high helix endmills for finishing.

The best tooling I've found for finishing aluminum would be PCD, but brace yourself for the cost (about 10-20X what carbide tooling cost). For uncoated tools, I like using Widia Hanita Alusurf tools and SGS aluminum tooling...

I went for some ISCAR polished three flute Ø6 endmill, and is doing really great.

At 24000 RPM it's really hard to have any trouble, also low AP's help reduce the chance of breaking the endmill.

Quote:

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Originally Posted by imitheo

I went for some ISCAR polished three flute Ø6 endmill, and is doing really great.

At 24000 RPM it's really hard to have any trouble, also low AP's help reduce the chance of breaking the endmill.

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With 6mm I'm more around 12krpm and about 60ipm and 3mm DOC for pocketing, 1.5mm for profiling. The tip of the tool is actually the most inefficient part. Though depending on machine rigidity you may not have a choice.

If you have a compressor, read up on MQL. I use a pulsed misting of 3:1 kero/olive oil. Parts are almost dry when done. It works, and big aerospace companies are using it.

Cheers
PS: soft aluminium alloys are the pits.

What kind of toolpaths are you producing? If you can use high speed adaptive type toolpaths that will help with chip load.