On 01/01/2021 18:49, Bob La Londe wrote:
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.

Someone mentioned an idea that had occurred to me and sounds
plausible. That
is, using a cheap CNC for marking drill holes (like a mechanized center
punch).

Also, seems there is confusion about cut smoothly. One pours water
in the
cutting bit area. Others use oil. More sophisticated appears to be
mounting a
blower nozzle on the motor to blow away the chips (instead of the
cutting area
being full of a sludge of chips in water or oil). I suppose best
might be
both, I think one guy has oil and air blowing on the cutting path,
but that
probably won't happen here.


I tried all of that with KNOWN aluminum alloys.Â* I do it every single
day for hours at a time.Â* I found best cutting results came from
modestly high volume of flood coolant dissolved in water.Â* I found
SC520 to be quite good and KoolMist to be quite ****ty.Â* 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. Â*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.Â* 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.Â* Your
mileage may vary.

I've used a cheap machines.Â* I've used middle weight machines.Â* 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.Â* Your mileage may vary.

The holdup for cheap machines is rigidity, spindle choice, and the
ability to manage coolant.Â* 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.Â* I would at a minimum go with a liquid
cooled spindle with an air seal.Â* Your mileage may vary.

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

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

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.