Plastic/Polymer for Pliers

Dec 16, 2004 2 Replies

Can anyone suggest a plastic/polymer that would have sufficient strength to make non-metallic needle nose pliers? I have seen pliers made of glass-filled nylon, but such material requires relatively large cross sections to maintain sufficient stiffness.



I am more than willing to look up the mechanical properties of any suggested materials, but I could use some suggestions (particularly for unusual materials).


Someone's already tooled up hemostats in polypropylene. The joint comprising four living hinges instead of a pin/clevis is pretty clever. They're strong enough to close a blood vessel or a thin plastic tube, once or twice, but you wouldn't want to work hard metal wire with them.

Some of the poly- ether- other- whatever- imide resins are moldable in thick sections and fairly strong. You've probably seen the stuff it rings like aluminum when you drop a part on the table.

Most of the resins that are strong/stiff enough to almost do what you want tend to be (shockingly) expensive, hard to mold, and brittle.

No plastic will substitute for metal, especially steel, in the same geometry.

You have to decide what, exactly, you want to do, and what non metallic behaviors you can tolerate, and how much space you've got to work with, and seek a specific compromise for each available material.

-Mike-

I did a quick search on

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for a polymer with a minimum Flex Mod of about 3 million+ and there were quite a few hits. There were even some materials at about 7 million. Pretty much every family was involved, ABS, PC, PEEK, LCP, Nylon.

Most of the materials were filled with a lot of carbon fiber. I can't comment on tool life with these resins, but in general any fiber reduces the life of the tool. The molding geometry can be a challenge too, since you don't get even shrinkage of the resin - it's different across and with the "grain". You can overcome this by designing the critical contact surfaces to be easily changed after you've made first shots and ironed out the process.

Matt

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