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Kiss cutting TPE/TPU ideas

Postby iab » November 15th, 2016, 4:20 pm


iab
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On the very outside chance someone here has some experience, I thought it can't hurt to ask.

What do you know about the tear properties of a TPE/TPU or even silicone?

This is the problem/idea. I have a bottle of liquid. In a simple plunging motion, I want to force a "stick" through a septum so the "stick" immerses into the liquid. The reason for an elastomer instead of simple foil seal is I want the septum to squeegee the excess liquid off of the "stick" when it is pulled out of the bottle.

My idea is to have a TPE/TPU, silicone with a 0.040-0.080 wall thickness and kiss cut an "X" let's say 0.020-0.040 deep. When you push the "stick" through, the material tears through the "X" only and use the "flaps" as the squeegee. I suppose I could also mold in the cut marks as an alternative.

This is probably more of a question for my material supplier, but does any of this stuff tear "well"? Playing with my Santoprene samples, the stuff really stretches before tearing. I'd have to put a lot of force on the "stick" for it to break through. When it does break through, it is a fast jarring motion. Not customer friendly at all.

Re: Kiss cutting TPE/TPU ideas

Postby engio » November 16th, 2016, 11:00 am


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I had tearing problems with an injection molded TPE part. It always started creeping at the gate. When we moved the gate the problem disappeared completely, and the part was very durable (designed to replace a leather-strap). While it's the opposite of what you're trying to achieve, but the way it behaved makes me think your idea is feasible - if I understood it correctly. If you have the possibility to IM it, I'm sure you can tweak it to the just right by experimenting with X-cut-depth, fillets/corners, and also the main shape. I'm thinking a cone or pyramid instead of flat?

Re: Kiss cutting TPE/TPU ideas

Postby iab » November 16th, 2016, 12:44 pm


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I like the pyramid idea. Tears at the vertices.

I'll put your name on the patent. ;)

Re: Kiss cutting TPE/TPU ideas

Postby iab » November 16th, 2016, 12:45 pm


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Do you recall the material spec?

Re: Kiss cutting TPE/TPU ideas

Postby slippyfish » November 16th, 2016, 1:15 pm

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Mold in the cut marks, and work with a water jet cutting vendor like http://www.flowwaterjet.com/ to fine tune the cutting depth.

(disclaimer - I don't truly know if this would work, but hey its a design forum)
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Re: Kiss cutting TPE/TPU ideas

Postby engio » November 17th, 2016, 7:45 am


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iab wrote:Do you recall the material spec?


Not in detail, just "TPE with UV adding, Shore 70 A"


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