On Friday, January 1, 2021 at 1:49:09 PM UTC-5, 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. 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 ****ty. 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.

I sometimes wonder why people then turn around and do weird things like lawyer-up, get accountant services, decide to incorporate, add college whiz kids to the payroll, etc...