printed hinges from TPU sandwich aka. DIY Hylite(R)?
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Hi guys,
do you remember the 'Zatsit' Delta printer kickstarter campaign? There was big interest in this new way of building hinges and effector from CNC'd Hylite.
I just thought, why not print a sandwich material with TPU or TPE in the middle? It might not be as durable as the real stuff, but I can print anything myself instead of looking for a CNC shop with an empty timeslot...What would be the best bonding and stiff material we could combine with TPU or other flex-filament?
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@o_lampe So called "living hinges" which you see on storage boxes and containers are usually made from polypropylene, so I'd have thought that would be the best stuff to use, rather than trying to make a sandwich using TPU.
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@deckingman
I'm not fixed on TPU but we'd need a good bond between polypropylene and ?? outer shell. -
@o_lampe I was thinking you could print the entire part out of polypropylene, rather than making a sandwich.
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From what I gather not much sticks to PP, but it would make a good approximation of Hylite since I believe hylite is just PP and Alu sandwich.
How much rigidity do you need? Do you even need a sandwich? PP is pretty durable and can be printed stiff/thick.
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@deckingman @Phaedrux
the thing with hinges or folded structures is, that they need a sharp edge for accurate bending dimensions. Think of a folded effector, it needs accurate rod distance for good print results.
That's where the aluminum plates come into play. I'm not sure if a PP_only part can offer both flexibility and stiffness at the same time.
And there might be a problem with layerbonding, seems it doesn't even stick to itself
I have some old TPU leftovers, I'll try bonding with PLA.
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...another way would be to use PP-sheets as inlay in a PLA sandwich. No bonding, so there has to be a mechanical (clamping or interlocking) solution.
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@o_lampe Sorry for waking up an old thread, but since I made some very flexible parts from 'flexible tough' resin, I rethought about the bonding issue we discussed with PP or TPU.
With 'ABS-like' resin I can print the bottom half of a sturdy shell, then add an already printed and cured 'flexible' inlay and print on with ABS-like.
Since both parts are based on resin, they will bond during the print process.Why do i post resin printer stuff here? The usecases for living hinges are Delta effectors, 5-bar SCARA arms or Tripteron builds. So in long term a DUET board comes into play
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Another interesting material for this might be Olefin Block Copolymer which is flexible when printed thin, and rigid when printed in larger blocks. So a geometry like
[]><[]may get you a living hinge from one material. I dont know how precise hinges like this can be. The high cost of OBC has kept me from trying myself tho.
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I have printed TPU on PETG and it bonds well without any messing around. Your folding print's first layer could be printed with TPU and the remaining layers with PETG to get some stiffness and to define the folding lines. I'd choose the first layer solid infill pattern so the (TPU) lines run as close to perpendicular to the folds as possible.
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@mrehorstdmd I haven't tried printing TPU on a FR2 bed.
I hope I can print a 0.1mm first layer and still be able to remove it in one piece. -
Just for the record:
I've printed a 0.4mm thick hinge from Anycubics "flexible tough" resin and it lasted only 16 cycle of 90° bending.
I had a hard time to print a thin hinge. It always turns out thicker than expected due to the burn in layer exposure time.
Maybe thinner hinges or if I increase the bending radius, they will last longer.
But there are obviously better materials available in sheet form.
I better laser-cut the hinges from PP and print only the hinge bodies. Stay tuned -
@o_lampe I haven't printed on FR2 either, but it sticks very well to PEI, sometimes too well. dribbling a little IPA around the edges of the print seems to help it release. It might help on FR2, too.
100 um seems pretty thin for a single layer.
