PDA

View Full Version : machining 1100 aluminum - how to prevent burrs?



beanbag
11-04-2012, 04:12 AM
I get to cut a bunch of holes and slots in Aluminum 1100 sheet metal. This is almost pure aluminum, so it is very gummy. When milling, it leaves a lot of burrs around the profile edges. What can I do to reduce these burrs? Right now, I have the sheet metal stacked 2 deep, so at least the lower layer doesn't get burrs. I also have mist / splatter coolant spraying to help chip clearing and prevent built up edge.

vincemulhollon
11-04-2012, 08:25 AM
Which side of the cut are the burrs appearing on? I tried the old tape trick on my bandsaw cutting aluminum and got somewhat better results than without the tape. Your mileage may vary. I don't think there is a 100% miracle cure.

The old tape trick comes from jigsawing thin plywood, clear packaging tape reduces (doesn't completely prevent) splinters. On metal I think it operates differently, chips can't stick to the cutter if there's a layer of tape goo between the cutter and the chips. Note you can set the tape on fire if you work fast enough and all this really does is change the problem from "I got burrs" to "I got fewer burrs and now I gotta remove the sticky packing tape stuff without slicing my hand open on the remaining burrs".

Scary razor sharp tools help, but you'll still have "some" burrs.

I tried the lit candle, melt wax on the work, cut thru the wax and the work, and all I got was smelly vaporized wax smoke and a filthy mess. Boiling water cleanup was easy enough. Didn't work for me, but maybe you wanna try it...

If you ever find a 100% perfect way to eliminate burrs let me/us know...

Uncle O
11-04-2012, 08:46 AM
Sharp tooling. If possible use a sacrificial, or top and bottom plate to clamp over/sandwhich . Size of the detail may not allow for that option tho.

Jaakko Fagerlund
11-04-2012, 02:30 PM
You have to have an endmill that has a left handed and right handed helix and they meet in the middle of the plate :D This way the helix won't pull stuff up to form a burr.

And no, I have no idea if such thing exists, but I do know that some type of plate-edge-tooling-without-burrs exists.

CountZero
11-04-2012, 02:59 PM
http://www.crowntooling.com/compression.html

I do have my doubts for using them with aluminium, especially gummy.

darryl
11-04-2012, 03:55 PM
I don't know the answer, but I think a good choice in cutters would make a big difference. Try to find the right cutter material and geometry- I like the mixed helix idea, sounds like it would go a long ways towards solving that problem.

Gary Paine
11-04-2012, 07:44 PM
I've had good luck with Do-All Tool-Saver. It's like a big stick of waxy compound that is applied to the cutter. Without it I was getting a aluminum build up on the cutter that was causing a ragged cut. With it, the cutter stayed cleaner, sharper, and cooler and the burrs were less troublesome.
I've no connection with the product other than as a satisfied customer.

Evan
11-04-2012, 08:25 PM
You must keep in mind that 1100 aluminum is weaker than many plastics. The Ultimate tensile is 13000 psi and the shear strength is only 9000. Also elongation is thickness dependent. In a one inch section it is about 28% at room temp but as it thins that goes up to as high as 40%. That particular property is what makes it form burrs so badly.

Lubricant always helps but you also need to keep the temperature down as low as possible. The properties turn to bubblegum quickly as temperature goes up even a little. Elongation before break doubles at 212F.

Toolguy
11-04-2012, 08:50 PM
The best way to deal with that is to use straight flute drills and end mills (2 flute) and Tap Magic for Aluminum.

beanbag
11-05-2012, 04:25 AM
With the sheet metal layered, I was cutting slots .100 wide by .100 deep, so I wanted to use a "normal" endmill for good chip evacuation. In the end, I didn't do anything special about preventing burrs. I just let them form. Then I used an exacto knife with a blade that looks like a chisel (bevel on one side, flat on the other). I just pushed it across the top and it took the burrs right off :)

Kevin45
11-05-2012, 10:02 AM
Stack a more rigid piece of aluminum on top of the 1100 pieces and it will help minimize the burrs. With dead soft material like that though it is almost impossible to keep it from burring. Another way that helps is to leave around a .005 cleanup cut where you can.