Machining sheet aluminium

[dave_ac]

Does anyone here have experience in machining sheet aluminium?

I’m making up some light and tool tube brackets and luggage rack that will take Pelicases (4 seconds to remove and 10 to fit) and Kriega bags. I’ve made plastic examples (the Polypropylene luggage rack is amazingly strong) and now want to make some in 3mm Aluminium which I’ll surface treat.

The machine is part of an art open source project. None of the arty folk have used their router on metal so are of limited information.

This is what I am running but getting inconsistent results. Mainly the edge looks melted & huge burrs.

6mm two flute carbon bit with a chip load .09 per tooth running at 15k rpm and a feed rate of 800mm/min. Depth of cut 0.5mm. I’m also using coolant.

I’ve upped the speed to 18k rmp and tweaked the feed rate up and down. The material is very securely screwed to the bed of the machine.

This morning on a single job I had either not too bad an edge right through to a hellish mess and the tool getting clogged up.

Any advice?

Some times the chips are perfect while at other times it looks like the tool is melting and building up the material either side of the cut.

My experience with machining is 20 years old, based on steel and using milling m/c and lathes manually.


Cheers
Dave

[AndyB]

You should be able to go straight through it in one cut rather than taking several small ones and that way the swarf will be able to flow away with the coolant. I'd pack it up so it's just off the table and nail it through with plenty of coolant running on it and also try climb milling rather than conventional milling. Also try a larger diameter cutter at slower speed because that'll also give the swarf somewhere to go.

The only things worse than aluminium when it comes to milling are copper and plastic because they just clog up at the slightest provocation.

[bikehunter]

If the alloy is too soft it will burr up. try lowering the speed as it may be getting too hot also.
I would have used a milling machine to cut the shape using a 6mm two flute with either cutting fluid or slurry at 2500 with a 450mm /min

[Stuart123456789]

someone once told me to use paraffin as the lubricant for machining aluminium, cheers

[kenny87]

A very sharp (new) bit, and parrafin as already said. Mystic's crap on ali. Also one pass should be fine, just leave a few tabs on it to be removed manually to avoid last minute carnage

[Rangoonruns]

+1 For parafin or use a tungsten carbide cutting tool

and slow that spindle to less than 2k if possible, not sure what you are trying to do? but if its just cut it use a bandsaw and then clean the edge with a power plane or the old fashioned way with a file.
if you are profiling i would just throw it at a water jetter it wont cost a lot at all and you will get a decent job

good luck with your project

[knobbly]

Slow the spindle down more and keep a constant pressure on the cut, don't let it back off or it will burr up cos you're just rubbing the Ali. Yes paraffin is the accepted cutting fluid but I also use WD40 as you want a very light oily fluid and you don't see paraffin much these days.
When machining softer materials you would normally have a slightly negative rake on cutting tools but it depends on what you have available.
The problem with machining things like Ali is that it builds up on the cutting edge of the tool as a lump, that lump then breaks off and takes the cutting edge with it. The key is to not let that lump build up but if it does, knock the lump off before continuing cutting. As said before get the swarf away from the tool quickly.

[dave_ac]

Big thanks guys.

Its the inconstant results that puzzling me.

I remember using paraffin on the few times i machined billet aluminium in my youth.

I've tried cutting 3mm in one pass - but the m/c struggled. I think its lacking HP.

Slowing the spindle just caused the tool to bind.

I think its a combination of factors, so ill stick to plastic proto types and then jet then water jet cut and the edges chamfered at the same time.

Thanks again, i'll post pictures when all is done.

[knobbly]

good luck with the project anyway. Bit hard to advise without actually seeing it.