Cutting aluminum with a cheap CNC

Can a CNC be turned towards the front/user so that it is on its side and the chips fall away from the cutting area?

Looks like he's doing pretty well with a modified 3018 CNC, even though not using anything to blow the chips away.

"I don't know what type of aluminum it was" :D Somewhere in Pakistan.

Whatever type, it looks like one big chunk of aluminum.

I wrote:

He zooms in on it.

On 12/31/2020 11:05 PM, John Doe wrote: > I'm not very hopeful in getting a cheap 3018 CNC to cut aluminum well, but... > I'm not concerned about how long making cuts takes, so that should help. On > YouTube, a few are successful, but many are disappointed. From the looks of > it, I can guess they have no idea what type of aluminum they are cutting on. > One can expect using a high-speed bit in buttery hardware store aluminum will > produce bad results. But they don't know that. They think they're just cutting > on metal. >

I tried all of that with KNOWN aluminum alloys. I do it every single day for hours at a time. I found best cutting results came from modestly high volume of flood coolant dissolved in water. I found SC520 to be quite good and KoolMist to be quite shitty. The guys at Master Chemical suggested I try SC620, but the SC520 works very well for me. It does seem to be hard on some paints, but only after months of exposure. Not an issue for a part that goes on and off the machine in a day. Your mileage may vary.

Air with mist lube can work, but it really requires a lot of air for anything, but the lightest cutter rubbing cuts. I can build an adequate flood coolant system cheaper than I can buy a compressor able to keep up with the volume needed for any decent cutting rate. Your mileage may vary.

I've used a cheap machines. I've used middle weight machines. I have not used high end multi ton machines (well one I own weighs a little over 2 tons), but the big boys all seem to prefer food coolant blast. Maybe they know something or maybe they learned it the same way I did by trying everything else first. Your mileage may vary.

The holdup for cheap machines is rigidity, spindle choice, and the ability to manage coolant. I can certainly build a small machine for under $1K USD that would cut aluminum within your constraints for not caring how long it takes. I would at a minimum go with a liquid cooled spindle with an air seal. Your mileage may vary.

Way back I did mark drill holes for off machine drilling. Then I realized that was stupid. If the machine can drill then drill. If it can't drill then interpolate. My time was better spent at the computer designing the next project. Your mileage may vary.

Just so you know I started out as a dilettante, and then graduated to hobbyist. Now I machine aluminum every day as my primary job. its how I pay my bills and buy my toys.

Yes, but it would be better to buy (or build) a machine with that layout in mind rather than to flip a gantry mill (cnc router) on its side. I have seen a couple machines designed and built that way. They worked fairly well, but they still used flood coolant to make sure the mill was not recutting piles of chips on shelves and in deep pockets. A decent fl0od coolant keeps the cutter and the work piece cool nearly eliminating chip welding, and the blast of coolant keeps the majority of the chips out of the cut to prevent recutting and tool or work piece damage on excessive unpredictable loads. Its particularly important when using smaller cutters for fine detail work, but can be an issue even with mid size cutters. Your mileage may vary.

The reason to consider a machine built for a vertical bed or table is that the machine itself will be designed to hold its shape by gravity as well as by its construction. The X (or Y) will be signed for lifting loads rather than sliding loads, and the Z will be designed to support the spindle with little or no sag in its horizontal configuration. Flipping a machine on its side does none of that. Your mileage may vary.

Soft aluminum is hard to cut well. And, if it gets even MODERATELY warm, it is MUCH worse. So, here are some things to consider.

Take lighter cuts than you might be able to get away with, but keep the feedrate up. That prevents heat from developing in one spot, it spreads the heating all over the work.

Flood coolant or any other coolant tends to keep the workpiece cool, that keeps the work metal stiff and allows the cutter to CUT, rather than MASH to work.

Use climb milling (opposite direction to what was shown in the YouTube video). Climb milling has the cutter diving into the uncut work, rather than going into the just-cut material and working up a ramp until cutting pressure drives the edge under the surface. Conventional milling causes increased heat, excessive cutter wear, and poor surface finish due to re- cutting and welding of chips. Climb milling avoids these issues, but has the problem it works against the backlash in the machine. So, climb cuts need to be made shallow on machines with a lot of backlash.

If you need to make a slot, use a cutter smaller in diameter than the slot width. Take several passes down the middle until at full depth, then move the cutter over and climb mill the sides to widen the slot to final dimension.

If the metal does not need to be bent later, 2024 is great, and 6061 is good. If you need to bend the sheet after milling, then either soft 5052 or

3003 can be used, but these require careful milling to avoid the heat buildup and problems with tearing or fouling the cutter.

I use almost exclusively 1/8" solid carbide 4-flute end mills for all aluminum panel machining. For the larger sizes, I use M-42 or M-57 cobalt HSS, which is 100X better than plain HSS, and only costs a few $ more. The eBay HSS tools out of China that come in the blue plastic tubes are AWFUL crap, and I would not use them.

Jon

I guess you have a good idea of what to expect regarding machining properties so might twig if something was up. I bought some 6082-T6, a common aluminium alloy in the UK, and it was gummy and horrible to machine even with lube much unlike the normal nice to machine stuff I had before. I took it up with the supplier and he immediately offered me replacement material from another bar and that was fine. He said he had run a production machine shop in the past and had experienced this before where things would run fine for months then go to crap with a new batch of material. Mill would say material spec OK but obviously the heat treat was bad, I think he had enough clout with the mill to get new stock in FOC.

This appears to be one of the cheapest of the cheap, but looks like he's doing pretty well with it.

I'm sure that's aluminum, not steel.

He has a light and a blower (apparently not working) on it?

Looks like an ordinary junk motor.

Maybe 1/8 inch bits.

...that Z axis bearing is failing?

To cut metal, you just need a sloppy set up...