Metalworking (rec.crafts.metalworking) Discuss various aspects of working with metal, such as machining, welding, metal joining, screwing, casting, hardening/tempering, blacksmithing/forging, spinning and hammer work, sheet metal work.

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Old January 1st 21, 07:05 AM posted to rec.crafts.metalworking
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Default Cutting aluminum with a cheap CNC

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.

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Old January 1st 21, 08:06 AM posted to rec.crafts.metalworking
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Default 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?
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Old January 1st 21, 03:07 PM posted to rec.crafts.metalworking
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Default Cutting aluminum with a cheap CNC

https://www.youtube.com/watch?v=AkziYG-Rq2U

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"

Somewhere in Pakistan.

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





I 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.


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Old January 1st 21, 03:09 PM posted to rec.crafts.metalworking
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Default Cutting aluminum with a cheap CNC

https://youtu.be/AkziYG-Rq2U?t=16

He zooms in on it.
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Old January 1st 21, 07:49 PM posted to rec.crafts.metalworking
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Default Cutting aluminum with a cheap CNC

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.

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Old January 1st 21, 07:56 PM posted to rec.crafts.metalworking
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Default Cutting aluminum with a cheap CNC

On 1/1/2021 12:06 AM, John Doe wrote:
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?



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.

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Old January 1st 21, 09:20 PM posted to rec.crafts.metalworking
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Default Cutting aluminum with a cheap CNC

John Doe wrote:

I'm not very hopeful in getting a cheap 3018 CNC to cut aluminum well,
but...

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
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Old January 2nd 21, 01:03 AM posted to rec.crafts.metalworking
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Default Cutting aluminum with a cheap CNC

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.* 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 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.

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Old January 7th 21, 10:26 PM posted to rec.crafts.metalworking
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Default Cutting aluminum with a cheap CNC

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

https://youtu.be/eiN_JhxguEs?

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.
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Old January 7th 21, 11:01 PM posted to rec.crafts.metalworking
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Default Cutting aluminum with a cheap CNC

....that Z axis bearing is failing?

https://youtu.be/eiN_JhxguEs?t=35

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


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