Air flow

Hi all, I have just finished my first aluminium cuts, and believe it or not they turned out very good, I used WD40 for cooling, but I understand that this can be done using air flow, what sort of pressure is need. Thanks.

Ok, seems as though nobody cuts aluminium.

Aluminium can be a bugger to cut, you have to pay attention to feed and cutter speeds, too high a feed and the flimsy little cutters snap like carrots, too slow and the clag builds on the cutting edge, the cut suffers and the cutter breaks. The margins are widened with cooling the cutter and I use WD40 or even water to keep the chips from melting and sticking. I also blow cuttings away with a nozzle fixed to the Z axis. The air, at fairly low pressure, comes from a pump designed for aerating large ponds.

Grade of aluminium makes quite a difference, 1050 is made for bending not cutting and sticks to cutters like shit to a blanket.

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Originally Posted by cropwell

Aluminium can be a bugger to cut, you have to pay attention to feed and cutter speeds, too high a feed and the flimsy little cutters snap like carrots, too slow and the clag builds on the cutting edge, the cut suffers and the cutter breaks. The margins are widened with cooling the cutter and I use WD40 or even water to keep the chips from melting and sticking. I also blow cuttings away with a nozzle fixed to the Z axis. The air, at fairly low pressure, comes from a pump designed for aerating large ponds.

Grade of aluminium makes quite a difference, 1050 is made for bending not cutting and sticks to cutters like shit to a blanket.

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Thanks for that, My first effort turned out well, I used the rate stated by thecad I use, using wd40 worked well, bur quite messy. I have a small compressor which is adjustable up 50 psi, I will try that next time.

You don't necessarily need a lot of pressure, it's the air quantity and velocity coming out of the nozzle that counts. Hence if you have thin pipes and a small nozzle you'll need higher pressure. I have a little side channel blower on my setup which only makes about 6 or 7 PSI but is much quieter than most compressors and outputs a lot of air and does the job fine. As per Cropwell I do find that some water/lubricant (I use 7....10% soluble oil in water) is a big help in stopping the ali sticking to the cutters.

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Originally Posted by Voicecoil

You don't necessarily need a lot of pressure, it's the air quantity and velocity coming out of the nozzle that counts. Hence if you have thin pipes and a small nozzle you'll need higher pressure. I have a little side channel blower on my setup which only makes about 6 or 7 PSI but is much quieter than most compressors and outputs a lot of air and does the job fine. As per Cropwell I do find that some water/lubricant (I use 7....10% soluble oil in water) is a big help in stopping the ali sticking to the cutters.

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thanks I will see what I can rig up.

I don't think my pond aerator pump produces even 6 PSI, but it is directed at the cut at all times. I use 8mm internal bore tube and keep the run of tube as short as possible. Just at the beginning of lockdown I decided to revamp my work room and the CNC is yet to be recommissioned, so I can't do pictures of the new, but this is the old :-
Attachment 31059Attachment 31060

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Originally Posted by cropwell

I don't think my pond aerator pump produces even 6 PSI, but it is directed at the cut at all times. I use 8mm internal bore tube and keep the run of tube as short as possible. Just at the beginning of lockdown I decided to revamp my work room and the CNC is yet to be recommissioned, so I can't do pictures of the new, but this is the old :-
Attachment 31059Attachment 31060

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I have one of those flexable tubes laying around in the shed, I am sure I can jerry rig something. thats a good setup you have..

As others have said, use a high speed and try to stick to a free machining grade like 6061 / T6 (IIRC). I use a airbrush compressor with a small reservoir and a small jet pointed at the cutter. Use standard airbrush hose, about a 1mm hole in the jet which is mounted on a bit of lokline from the mill head so it can be directed at the work. I don't use coolant.

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Originally Posted by JohnHaine

As others have said, use a high speed and try to stick to a free machining grade like 6061 / T6 (IIRC). I use a airbrush compressor with a small reservoir and a small jet pointed at the cutter. Use standard airbrush hose, about a 1mm hole in the jet which is mounted on a bit of lokline from the mill head so it can be directed at the work. I don't use coolant.

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I have the same airbrush compressor with a tank. I was wondering if I could use thay, good stuff, thanks.

Only thing to watch is overheating. These compressors are designed for fairly short run times in normal use, with pressure cut-off switch. Running for 30 mins or an hour on a long cut they might get too warm. I fitted a computer fan on the back of the crankcase to blow air through it.

Strange that! I had a LIDL airbrush compressor, with a disposable welding gas bottle to make a reservoir. I only used it to clean down the machine and shift any build up of chips. This has been since replaced with a small Jun-Air compressor, which is nice and quiet and it only cost me £20. It is old and needed a new pipe and a service, but it is a quality machine. Apparently these compressors are used in Banks as part of the security grill system and with the closure of Branches, they are becoming available.

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Originally Posted by JohnHaine

As others have said, use a high speed and try to stick to a free machining grade like 6061 / T6 (IIRC). I use a airbrush compressor with a small reservoir and a small jet pointed at the cutter. Use standard airbrush hose, about a 1mm hole in the jet which is mounted on a bit of lokline from the mill head so it can be directed at the work. I don't use coolant.

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If you don't mind, can you advise compressor model?, also, can this run/provide cooling continuously (say 1hr+.... I know that's probably short for some people)

The reason I went for the large pond aeration pump is that it can run continuously (24/7 if necessary). It is quiet compared with even an airbrush compressor, pumps out 80L/min free air (70L/min in a typical pond aeration rig) and can produce 0.3 MPa which is 43PSI The ACO-388D costs £40 - ish. When I get my machine recommissioned, I will use it again, with the bigger compressor for large area clearance.

Just a footnote, I started off with a smaller pump, which was OK but not brilliant.

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Originally Posted by cropwell

The reason I went for the large pond aeration pump is that it can run continuously (24/7 if necessary). It is quiet compared with even an airbrush compressor, pumps out 80L/min free air (70L/min in a typical pond aeration rig) and can produce 0.3 MPa which is 43PSI The ACO-388D costs £40 - ish. When I get my machine recommissioned, I will use it again, with the bigger compressor for large area clearance.

Just a footnote, I started off with a smaller pump, which was OK but not brilliant.

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I just ordered thw ACO-328, which is also 80L, will see how it goes, thanks for the help. appreciates.

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Originally Posted by Doddy

If you don't mind, can you advise compressor model?, also, can this run/provide cooling continuously (say 1hr+.... I know that's probably short for some people)

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Sorry, I haven't a clue it's just one of those generic airbrush compressors. With the cooling fan it can run indefinitely I think.

Another option might be a HVLP high volume low pressure paint sprayer. These use a radial compressor, so sound rather like a vacuum cleaner...

I bought an Erbauer one from Screwfix and it worked well for clearing swarf - too well, so the stuff ended up all over the workshop. Until I get round to fitting an enclosure, I am persisting with flood cooling and periodic blasts with a handheld air line.