Ancestors

Written by Luka Rubinjoni on 2024-03-07 at 12:01

Ok, so this bistable compliant switch printed in PETG failed at about 25 a/b cycles... #3dprinting #petg #prusa #CompliantMechanisms

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Written by Luka Rubinjoni on 2024-03-07 at 12:06

Here's the source page... Printed in PETG (personally extruded by Josef Prusa himself, lol), 0.4mm hardened steel nozzle, textured print sheet, 0.2mm layer height, 15% infill. Default settings for Josef's PETG in PrusaSlicer 2.7.2.

https://www.thingiverse.com/thing:2988576

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Toot

Written by Luka Rubinjoni on 2024-03-07 at 12:11

Of course, I stared fidgeting with the switch as soon as the print was done... The switching was very pleasant (not too much force required - I need to find a tool to measure it). It was so easy to switch, I just started flipping it quickly and counting. It's possible I overheated it - the first hinge to fail was the one connecting the base and the lever of the switch, not the ones on the "free bar". The free bar ones failed fairly quickly after some more fidgeting. Need to try it in PLA, ABS...

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Descendants

Written by Luka Rubinjoni on 2024-03-08 at 09:27

So, next in line is a flexible filament I had on hand: colorFabb varioShore TPU. I'm using the Prusa Slicer preset, with temperature set to 190C. #3dprinting #TPU #colorFabb #varioShore #prusa #CompliantMechanisms @3dprinting

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Written by Luka Rubinjoni on 2024-03-08 at 09:31

Prusa Slicer says TPU isn't compactible with MMU2S multi material mode. Which is reasonable, since I hot a filament jam as soon as I tried to load it. Still, I might try to do a flexible/rigid composit later on... (PLA/TPU or something with compatible extruder temps). #prusa #mmu2s #tpu

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Written by Luka Rubinjoni on 2024-03-08 at 09:36

Also, the failure of PETG switch could be due to the slicing/g-code quirks... The compliant area isn't printed as long strings, but as separate walls that touch at the narrow point. I should look into this further... #CompliantMechanisms

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Written by Luka Rubinjoni on 2024-03-08 at 12:30

Here's the print in TPU. A layer of outer wall delaminated while I was removing the switch from the bed. Even printed at 190C, the whole thing is too soft to act as a switch - it retains the "b" position only if I press the bottom against the table. #CompliantMechanisms #3dPrinting

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Written by Luka Rubinjoni on 2024-03-08 at 13:10

Next in line, good old ABS... #3dPrinting #ABS #CompliantMechanisms

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Written by Luka Rubinjoni on 2024-03-08 at 13:53

Got a wee bit of separation from the bed... Almost done, it will work (but definitely needs a skirt). #ABS #3dPrinting #CompliantMechanisms

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Written by Kyle Davis on 2024-03-08 at 13:56

@rubinjoni I do a lot with compliant mechanisms and foldable prints.

This your results are not surprising.

I’ve been asked why I don’t use TPU for this type of project: it seems right but TPU is flexible (bends) and elastic (stretchy). Elasticity isn’t what you want: compliance relies on some of the print being able to be rigid and non-stretchy. PETG and PLA do work but the performance in this application varies wildly.

There is also flex PLA but it is weak and hard to print.

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Written by Luka Rubinjoni on 2024-03-08 at 14:00

@linux_mclinuxface Thanks for the feedback! I'm just going through the available materials, trying out the prints. In your opinion, is BYU bistable switch a good benchmark for trying out materials for #CompliantMechanisms ? Would you suggest something else? What would be a compliant mechanism #Benchy ?

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Written by Kyle Davis on 2024-03-08 at 14:11

@rubinjoni I don’t think I know of a good benchmark print honestly. Compliant mechanisms is just a very wide category. That model does look good as a starter bistable. They can get pretty complex and this one looks simple enough.

As far as getting it to work, think about tweaking your slicer settings. You need very consistent flow especially around the intersection between the joint and body. Also make sure you have a high number of walls/perimeters.

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