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 o f the plastic jamming the chip conveyor. Now I am a novice but do know en ough 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 cn c turning center.
Dan
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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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What did you lubricate it with?
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On 6/21/2019 9:32 AM, Jim Wilkins 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 >> >> ************ >> >> 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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On Fri, 21 Jun 2019 04:51:28 -0700, snipped-for-privacy@krl.org wrote:

I don't think any sort of classic chip breaker like for metal will work. The stuff is PLASTIC, of course, and therefore will just curl around anything like that. Some plastics also produce a HUGE static charge when cut, so the chips stick to everything.
Jon
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On Jun 21, 2019, Jon Elson wrote

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

do

a

way.

t or

The turning center is a Okuma LB15. Not the latest and greatest, but in g ood shape.
Using HSS makes sense. No need for carbide that can withstand high tempera res and pressures. And HSS can be sharper.
I thougt it would be easy to find a comercial solution to plastic chips. b ut 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 mu ch with actually getting the chip to break. Might be able to program pause s that would limit the length of the chips to 5 or 10 feet.
Will post our sucess or failure.
Dan
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On Sunday, June 23, 2019 at 10:30:01 PM UTC-4, snipped-for-privacy@krl.org wrote:

of the machine. If that does not work well we might try CO2 cooling. I wou ld 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 pau ses that would limit the length of the chips to 5 or 10 feet.

The program was changed to include " pecking " and now the problem is mana geable. The chips are maybe 2 feet long and can be removed by hand. Not a perfect solution, but as long as the chips are removed after machining e ach part, the chips do not clog the machine.
Peek is somewhat flexible and the chips can be cut with scissors. So it mi ght be possible to make some sort of motorized cutter to cut the chips to a much shorter length, but it does not seem a high priority to do that.
Dan
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On Friday, June 21, 2019 at 4:20:05 PM UTC-4, Joseph Gwinn wrote:

s for carbide. But I can not locate a source. Any one know where one can buy them?
Dan
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On Friday, June 21, 2019 at 4:20:05 PM UTC-4, Joseph Gwinn wrote:

I 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 ---------------------------------------
https://littlemachineshop.com/info/inserts.php
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On Mon, 24 Jun 2019 21:36:03 -0400, "Jim Wilkins"

Arthur R. Warner. https://www.arwarnerco.com/Default.asp
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On Tue, 25 Jun 2019 06:00:58 -0500, Pete Keillor

I don't want to get into any arguments but I grew up and did my apprenticeship in the High Speed Steel days and I must say that the way we were taught to grind high speed tool bits resulted in a substantially different tool than what I see used with "insert" type tool holders which I suspect might be better for turning something like plastic. http://www.steves-workshop.co.uk/tips/toolgrinding/toolgrinding.htm
https://www.youtube.com/watch?v=hrDr4rYLiAk

--
cheers,

John B.
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On Sun, 30 Jun 2019 05:08:58 +0700, John B.

Hi John. HSS indexible inserts are available. Even Amazon has some. I've seen them offered with or without a chip groove and, IIRC, with a moderate amount of relief or no relief.
Granted, those variants were things I saw years ago, but I think you'll find that a few different types are offered, and some look exactly like typical carbide inserts.
--
Ed Huntress

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On Sat, 29 Jun 2019 19:18:24 -0400, Ed Huntress

Probably true as I've been totally out of the trade since 1972 and when I left we were still using HSS. In fact, thinking back, I can remember only one time we used a carbide tool to turn something and it was a hard valve insert in some sort of special valve and the HSS just wouldn't make a compete cut. (Damn! that was nearly 50 years ago :-(
But I think if I were to buy a hobby lathe today I'd still go for HSS if for no other reason than it lets you grind all sort of special bits for various projects. Back in the day a machinist would probably have ten or a dozen tool bits in his tool box that he had ground for some sort of special project over the rears.
And, if there was a bench grinder in the shop you never had to worry about dull tools :-)
--
cheers,

John B.
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My take on inserts is that they eliminate tool offset adjustments in high volume production. I'm with you on HSS but I make only one to maybe a dozen identical parts so one sharpening is enough.
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    [ ... ]

    Useful.

    Yes, there are materials where carbide is the better choice.

    There are tradeoffs. HSS for specialized tools/purposes.
    Carbide inserts and a quick-change toolpost for repeated operations. The inserts can be rotated to give two, three, four, or up to six different cutting corners, depending -- and each time you do this, you don't have to re-calibrate the dial to the new length of the bit -- that is what "indexable" means. Especially useful with CNC and automatic tool changers, but useful enough with a lathe with a quick-change toolpost, and remembering the zero point for the tools where the diameter of the turned workpiece is important. And the inserts are made sufficiently precise so the zero is maintained when you finally wear out all the points on the insert and replace it with a new one. :-)
    I use carbide inserts most of the time -- but still grind special tools at need -- including ones to cut ACME threads a bit too big for the insert tools which my lathe can handle.

    Agreed -- but you did have to re-zero the dials after each re-sharpening. :-)
    Enjoy,         DoN.
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wrote:

Actually I was thinking of lathe tools and most of the lathes I ran, in those days, had cross feed and compound dials that could be "zeroed" to read zero (:-). Cutting threads for example you touched the tool bit to the work, to start, zeroed the cross feed and compound and then used the cross feed to retract the tool for returning to the beginning after each cut and reset to zero to begin the next cut and the compound feed to set the depth of cut.
--
cheers,

John B.
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On 6/21/2019 7:51 AM, snipped-for-privacy@krl.org wrote:

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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On Fri, 21 Jun 2019 04:51:28 -0700 (PDT), " snipped-for-privacy@krl.org"

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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On Fri, 21 Jun 2019 04:51:28 -0700 (PDT), " snipped-for-privacy@krl.org"

I run a shop vac with a 2.5" line lock hose. Noisy, yes.
R Remove 333 to reply. Randy
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