Need help cutting Aluminum

[waltie]

I am trying to machine 1 mil al sheet, using a Onsrud 3/16 UpcutSpiral O bit,16,000 RPM with a feed of 1.3IPS, also using a mister. I am getting weld of the chip to the material.
What am I doing wrong?

[Brady Watson]

Walt,
Try using an air nozzle OR the dust foot hooked up to your DC to air-cool the bit. Liquid or mist cooling on a Bot with a wood spoilboard is bad news...

If you are getting welding of chips on the edge it is telling you that your current method of cooling is not adequate and/or your RPM is too high or feed rate too slow. With that bit, I think that you are in the zone with your speeds/RPM. Try air cooling.

Here's my air setup running @ 25 PSI, assembled from brass fittings and Husky/HomeDepot blow gun parts:



8815

8816

This is setup for a 5HP Colombo. Yours may vary depending on what tool you are running...I hacked this together in about 20 min.

-B

[wcsg]

Walt are you using a single or double flute O? If it's double flute your going to fast, that speed and feed sounds good for a single flute only

[waltie]

Single Flute

[waltie]

Brady, The AL is gluded to 3/4 MDF, so the water issue is not a problem. I had to do this because the parts are about 1.750 X 1.750, Very small to hold down otherwise.

[steve4460]

HI Waltie
I good results with an 1/4" downspiral at 10000 rpm at 0.8 ips and some WD40 sprayed on ebout once a minute , just a little squirt in to the cutt and on the cutter .
Bot on

[Brady Watson]

OK...I still think that you mister is not doing the job. The welded edge is telling you that the tool is not sharp or it is too hot, causing the chip welding. I'd try running dust collection as an experiement. The air will cool the bit. You also might want to try a 2-flute tool and crank your speeds up to around 1.7 to 2.2 IPS. Rpm should be in the 13,000 to 16,000 range.

www.bradywatson.com/Aluminum.htm (http://www.bradywatson.com/Aluminum.htm)

-B

[john_david]

If you can afford the mess I allways use w-d 40all the time Works Great


JD

[waltie]

I thank everyone for their help, now a new problem. I am getting bad chatter marks all around this part. How can I get rid of these, or
can I?

[Brady Watson]

What diameter bit are you using? Going up to a larger dia bit helps. How clean are your vectors? Are you using the shopbot_arcs post processor (you should be) or the straight inch version?

-B

[waltie]

Part done in AutoCad, using Arcs post MM, and using 3/16 spiral O bit, only bit I got, here is
a picture of the part (I Hope)




8817 (30.7 k)

[Brady Watson]

You don't need to use an o-flute to cut AL. I use a standard carbide end mill (same grind as upcut spiral) and it does just fine. I take it you saw the water pump impeller I made? That was machined with a 2-flute end mill & 2-flute ball mill. Since you are gluing the AL down, hold down is not an issue. A 2-flute end mill will allow you to go at faster speeds as well. Regardless of the bit that you use, you are going to get some 'coin edges' on AL sheet that are easily removed with an orbital.

-B