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 June 21st 19, 12:51 PM posted to rec.crafts.metalworking
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Default chip breakers for plastics

I am trying to help a guy who is opening a machine shop. Which is kind of comical since I have no experience in commercial machining.

He has a job machining peek plastic. And has a problem with long strings of the plastic jamming the chip conveyor. Now I am a novice but do know enough when confronted with a problem the first thing to do is find out what others have done. So how do you deal with strings of plastic?

When manual machining plastics I just pause feeding te avoid having one long chip. But maybe there is a better way. This is being done on a cnc turning center.

Dan

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Old June 21st 19, 04:55 PM posted to rec.crafts.metalworking
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Default chip breakers for plastics



wrote in message
...

I am trying to help a guy who is opening a machine shop. Which is kind of
comical since I have no experience in commercial machining.

He has a job machining peek plastic. And has a problem with long strings of
the plastic jamming the chip conveyor. Now I am a novice but do know
enough when confronted with a problem the first thing to do is find out what
others have done. So how do you deal with strings of plastic?

When manual machining plastics I just pause feeding te avoid having one
long chip. But maybe there is a better way. This is being done on a cnc
turning center.

Dan

************

Never having used a real turning center my feedback may be moot, but what I
have done on the manual lathe is make sure my cutter is very sharp, cranked
up the RPM and placed a garbage can where the arc of the chip shooting out
into space is piling up.

My biggest issue with plastic on the lathe otherwise was it getting into my
chuck and gumming it up. Had to take it all apart. Not just pull the jaws.

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Old June 21st 19, 05:32 PM posted to rec.crafts.metalworking
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Default chip breakers for plastics

"Bob La Londe" wrote in message
...


wrote in message
...

I am trying to help a guy who is opening a machine shop. Which is
kind of comical since I have no experience in commercial
machining.

He has a job machining peek plastic. And has a problem with long
strings of the plastic jamming the chip conveyor. Now I am a
novice but do know enough when confronted with a problem the first
thing to do is find out what others have done. So how do you deal
with strings of plastic?

When manual machining plastics I just pause feeding te avoid
having one long chip. But maybe there is a better way. This is
being done on a cnc turning center.

Dan

************

Never having used a real turning center my feedback may be moot, but
what I have done on the manual lathe is make sure my cutter is very
sharp, cranked up the RPM and placed a garbage can where the arc of
the chip shooting out into space is piling up.

My biggest issue with plastic on the lathe otherwise was it getting
into my chuck and gumming it up. Had to take it all apart. Not
just pull the jaws.


What did you lubricate it with?


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Old June 21st 19, 09:25 PM posted to rec.crafts.metalworking
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Default chip breakers for plastics


On 6/21/2019 9:32 AM, Jim Wilkins wrote:
"Bob La Londe" wrote in message
...


wrote in message
...

I am trying to help a guy who is opening a machine shop. Which is
kind of comical since I have no experience in commercial
machining.

He has a job machining peek plastic. And has a problem with long
strings of the plastic jamming the chip conveyor. Now I am a
novice but do know enough when confronted with a problem the first
thing to do is find out what others have done. So how do you deal
with strings of plastic?

When manual machining plastics I just pause feeding te avoid
having one long chip. But maybe there is a better way. This is
being done on a cnc turning center.

Dan

************

Never having used a real turning center my feedback may be moot, but
what I have done on the manual lathe is make sure my cutter is very
sharp, cranked up the RPM and placed a garbage can where the arc of
the chip shooting out into space is piling up.

My biggest issue with plastic on the lathe otherwise was it getting
into my chuck and gumming it up. Had to take it all apart. Not
just pull the jaws.


What did you lubricate it with?




Same thing I use for almost everything now. SC520 and distilled water.
One of the very few things I use spray mist for. In fact the only thing
I can think of in some years where mist is better than flood. (High
(relative) rpm with no enclosure.)
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Old June 22nd 19, 12:06 AM posted to rec.crafts.metalworking
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Default chip breakers for plastics

On 6/21/2019 7:51 AM, wrote:
I am trying to help a guy who is opening a machine shop. Which is kind of comical since I have no experience in commercial machining.

He has a job machining peek plastic. And has a problem with long strings of the plastic jamming the chip conveyor. Now I am a novice but do know enough when confronted with a problem the first thing to do is find out what others have done. So how do you deal with strings of plastic?

When manual machining plastics I just pause feeding te avoid having one long chip. But maybe there is a better way. This is being done on a cnc turning center.

Dan


Haven't thought about this stuff for many years.
Having 22 years in the Plastic Industry tells me I should
chime in with some thoughts.

Not visually knowing exactly what process or kind of plastic,
but. my first thought would be to set up a 1-1/2" pipe with
an inserted 1/4" air line about 4" from one end that protrudes
into the pipe and is angled in line with the pipe. The 4" end
would be the entrance port and the "other end" maybe 3' long
with a radius that would discharge into a box or barrel for the
scraps. Turn on the air line and it will create a Venturi Effect
which will suck the chip strings from the machining area.

I built a couple years ago. The were used to move plastic granules
from a barrel on the floor up to a 12 foot high 30" diameter hopper.
The hopper sat on the back of plastic extruders.
It was easier than carrying 50 lb bags up a ladder.

You can Google Venturi and see a lot of pictures.

There are a number of commercial units that can be purchased.
However, you can get a little creative to see the effects.
A cheap one can be made up just to see if the theory will work.

Needless to say, some experimenting will be needed.

However there is a downside. Your air compressor will run more
just to keep it operating. Would be wise to do a little math
to determine the economics.

Good Luck.

Les

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Old June 22nd 19, 01:07 AM posted to rec.crafts.metalworking
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Default chip breakers for plastics

On Fri, 21 Jun 2019 04:51:28 -0700 (PDT), "
wrote:

I am trying to help a guy who is opening a machine shop. Which is kind of comical since I have no experience in commercial machining.

He has a job machining peek plastic. And has a problem with long strings of the plastic jamming the chip conveyor. Now I am a novice but do know enough when confronted with a problem the first thing to do is find out what others have done. So how do you deal with strings of plastic?

When manual machining plastics I just pause feeding te avoid having one long chip. But maybe there is a better way. This is being done on a cnc turning center.

Dan

Greetings Dan,
I haven't machined PEEK but I have machined a lot of plastics. The
problem is not just that the plastic doesn't want to form a chip that
can be broken at room temp but since it is at an elevated temp from
being cut it becomes even more resistant to breaking.
What I have done with plastics that act the same way is to cool
the chip. Get it as cold as possible. Even cold coolant may be enough.
Not for UHMW though. At least I didn't have coolant cool enough.
It may seem exotic but CO2 can be use as a coolant and there are
systems made for using it. After reading about it years ago I tried a
setup for turning UHMW. I just used a 1/4 copper tube to direct the
CO2 to the tool.
I soldered a piece of brass into the tube and drilled it to make an
orifice. Then I opened a needle valve close to the tool and started
the cut. Using a heavy cut on the diameter helped to break the chip.
But I was able to defeat the chip breaking if the feed rate was too
heavy.
I had to turn my CO2 cylinder upside down to get liquid to flow out
because I didn't have the right kind of cylinder. And I used a lot of
CO2. Even though the experiment worked to some extent it was just that
and it was kind of a kludge with the CO2 cylinder being upside down
and resting on the ways and the end of the lathe. I shoulda taken a
picture because it really looked like redneck machining.
So if your friend is machining enough of this plastic it may be
worth it to look into really cold coolant.
There are also lathes that can stop the cut like you did on a
manual machine but I don't know what your friend has. They do this
very fast and are really expensive so I am betting your friend doesn't
have a machine that does this.There also may well be tools that do the
same thing.
I have a feeling that what will work the best though is some sort of
mod to the conveyor that will move the chips out of the lathe faster
so they won't have a chance to clog the conveyor.
Eric

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Old June 24th 19, 03:29 AM posted to rec.crafts.metalworking
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Default chip breakers for plastics

On Friday, June 21, 2019 at 4:20:05 PM UTC-4, Joseph Gwinn wrote:
a

He has a job machining peek plastic. And has a problem with long
strings of the plastic jamming the chip conveyor. Now I am a novice
but do know enough when confronted with a problem the first thing to do
is find out what others have done. So how do you deal with strings of
pl

The key is to use SHARP HSS tools intended for plastic, and to keep the
plastic from melting and gumming everything up. Even plain water used as a
coolant will prevent melting, and will drain the static electric charge away.
To keep corrosion of the machine tool surfaces down, it is traditional to
dissolve some bicarbonate of soda in the water. Do not use any kind of fat or
oil, as it will degrade the plastic.stic?
stic?


As for chip breaking, the usual approach is to arrange for the chip to be
pulled away as fast as it is generated.

Joe Gwinn


The turning center is a Okuma LB15. Not the latest and greatest, but in good shape.

Using HSS makes sense. No need for carbide that can withstand high temperares and pressures. And HSS can be sharper.

I thougt it would be easy to find a comercial solution to plastic chips. but so far have not found one.

I think we are going to first try using air to suck the chip streams out of the machine. If that does not work well we might try CO2 cooling. I would think cooling would help with holding tolerances and finish, but not so much with actually getting the chip to break. Might be able to program pauses that would limit the length of the chips to 5 or 10 feet.

Will post our sucess or failure.

Dan

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Old June 24th 19, 11:53 PM posted to rec.crafts.metalworking
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Default chip breakers for plastics

On Friday, June 21, 2019 at 4:20:05 PM UTC-4, Joseph Gwinn wrote:


The key is to use SHARP HSS tools intended for plastic,

Joe Gwinn


IĀ*understand that one can buy HSS inserts that fit in the tool holders for carbide. But I can not locate a source. Any one know where one can buy them?

Dan



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