Best way to cut ePTFE sheet laminated to a polyester/polyethylene backer

[Mgobluecw2]

Hello,

So I'm having trouble cutting a thin (<1.5mm thick) sheet of expanded PTFE laminated to a polyester/polyethylene backer. The kicker is the sheet is half an inch wide and I'm tying to cut circles with a diameter of .4 inches. I'm using a cutting die, but am experiencing tearing of the backer instead of the desired clean cut. Any suggestions? Would shearing the cutting die or increasing the tension of the strip help create a cleaner cut? Any help would be greatly appreciated.

Thanks,

G

 

[patprimmer]

I don't know for sure, but I suspect shearing might make it worse unless you can get virtually no clearance between the cutter and the matching shear blade. Even 0.001" clearance will allow extrusion of the elastomer backing I would think.

A hot knife might do better.

Dipping the material to be cut into liquid nitrogen should help, but hardly worth the trouble I would expect

Regards
Pat
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[Mgobluecw2]

Thanks for the reply. Would the speed of the cut have any effect? A hot knife is not plausible for the process unfortunately. I think I have to play around with the die cutting speed and angle as well as the tension in the strip of ePTFE, but haven't been successful as of yet.


-G

 

[btrueblood]

Can you clamp around the entire o.d. of the punch before pushing the cutter into the material? What kind of backing are you cutting against, sounds like it might need to be harder/stiffer? In the end, would a waterjet cut it quicker, cleaner, and easier?

 

[MikeHalloran]

First thing I would try is sandwiching the laminate between two sheets of card stock, e.g. opened manila file folders.

If that didn't help, and probably anyway, I'd send it out for laser cutting. (Which may not work, depending on the color of the material and the laser wavelength.

If that didn't work, I'd send it out for waterjet cutting.

(I'd do it in that order because, if it works at all, I suspect the laser would give you a better edge finish.)

Mike Halloran
Pembroke Pines, FL, USA

 

[Mgobluecw2]

I can't sandwich the laminate because after it's cut it's being held down to a liner via vacuum pressure and then welded on. The material being cut is PTFE laminated to a Polyethylene/Polyester backer. There's a .2" clearing from the PTFE cut to the liner surface which is also causing some flipping issues. Thanks for the suggestions and please keep them coming!


-G

 

[Compositepro]

You should be using a steel rule die, which is basically a razor sharp edge that cuts your film against a hard plastic backing.

One thing that may allow your shear die to work better is to cool your film so it will be more brittle and not stretch at the cut. A compressed air Vortec cooler or a shot of liquid CO2 may work.

 

[patprimmer]

Opps. I read the backer as a polyether/polyester backing which I presumed to be either a polyurethane or a Hytrel type of material both of which have extremely low entitlement temperatures.

Now I am not quite sure what you mean by polyethylene/Polyester as they are quite different materials and are not normally sold as alloys as far as I know.

Regards
Pat
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[Mgobluecw2]

The polyester/polyethylene backer is a weave. The polyester is surrounded polyethylene and creates a random weave that adds stability to the expanded PTFE layer above. My problem getting a clean cut stems from not being able to cut against a hard surface. I have to cut it against a soft foam surface and cannot cut the foam. I can get 3/4 of the circle diameter to cut clean, but am tearing the last fourth of the material which causes issues with our process.

 

[btrueblood]

"My problem getting a clean cut stems from not being able to cut against a hard surface"

Ugh. That might be an insurmountable problem. Can you try using something like a paper drill - basically a razor-sharp steel rule die, but it spins in a drill press. I'm not holding my breath for sucess on that method either. Freezing to get the foam stiffer is unlikely to work, you will likely shatter the weak foam substrate before affecting the fabric layer much.

 

[patprimmer]

I'm starting to think this fabric is a split tape fibre which is hard to cut clean even under good conditions.

Regards
Pat
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