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The broken cheap plastic clip that my S.O. Vicki used to close open bags of chips, etc was terminal. I think some plastics have a finite life, after which they become weak and fragile if not forgetful and leaky. If a product design was made marginal to begin with by minimizing use of material to squeeze out the last milli-yuan (0.0114 cents in China), it will eventually break and there won’t be no fixin’ it.
So I clanged the can with that piece – uh, those pieces -- of Chrap (Chinese crap) and decided I’d make a better one – or two, or maybe three – for milady. Stocking stuffers from her hero, eh?
Yesterday I couldn’t for the life of me remember how I’d made torsion springs, like those found on wooden clothespins, the pawl on the little winch, and that piece-o-Chrap bag clip. It came to me in a dream while sleeping. Voila. Took me 10 minutes to make a little jig since I have no idea where I put the last one I made. They’re so small and easy to make I don’t pay any attention to where I put them after use if I even bother to keep them.
I didn’t try to duplicate the original Chrap clip, just freehand 3D modeled something of similar dimensions and 3D printed the two plastic parts. I printed two sets, one of black PLA+ and the other of green PETG. I’d not printed with PETG before with my entry-level Creality Ender 3 printer and wanted to see how (or if) that might work. If we’re not learning we’re dying.
It worked just fine first try, no problem. While the plastic parts were printing (5 grams of material, 1 hour 20 minutes each) I made the springs. I cleaned the rust off of some .039” music wire, cut some pieces 3.5” long and zinc-plated them so they won’t rust again. Then I wound the springs. That takes less than a minute with no bad words if I don’t drop anything. I did drop one piece of cut spring wire into the portal that goes to the 4th dimension. I spent few bad words on that. I might have spent more but those I used were really bad words. My dear late wife Mary would have been proud of me. “Not bad, Foreman, I may eventually promote you from apprentice epithet artificer.” Gentle, soft-spoken Mary of melodious voice could blister the paint off a fork lift , shrink the piston of a truck driver and shrivel the trident of a Navy Seal – while smiling sweetly.
I could have just glued in bits of 1/8 rod in for the hinge pins, but I decided to turn brass pins with heads because it’s easy to do and it’d keep glue away from the joint that must move freely. They’ll be secured with E-clips. I just happened to have a piece of 1/8” rod with 3 little rubber rollers and six E-clips on it, undoubtedly cannibalized from a tractor-feed dot matrix printer in the dim and distant past when dinosaurs and MS-DOS ruled the planet.
Here are the various parts of the green PETG clip, and the black PLA+ clip assembled and ready to go. The three ridges are copied from the original. I’m not sure they’re necessary or helpful, but it was easy enough to incorporate them in the model.
I’ll make one more, that one out of blue PLA. I already have the hinge pin and E-clip ready to go for it. The straight piece of .039” zinc-plated spring steel music wire in the photo will become the third spring.
How to insert spring into hinge gap without losing it: I stuck a bit of 1/8” rod thru the hole in the spring, grabbed that rod in a vise to keep the spring captive. Then I compressed the spring with a pair of pliers to make the legs parallel, then inserted the parallel legs into the neck of a spent .30-06 Springfield rifle cartridge case. The spring was then captive to the rifle brass which I could then use as an insertion tool to place the spring in the hinge gap and put the pin thru the hole. Then pull out the rifle brass so the clip snaps shut.
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