3D Printing Living Hinges

[john12]

Hello,

I've been trying to 3D print living hinges for a few different projects for a while and was wondering if anyone had any tips.

Living hinges are used all around us. The best example is probably on a ketchup lid. Basically the entire lid is one single piece but the top and bottom are joined by a thin piece of plastic (or other materials in different applications) that flexes and allows the parts to open and close.

These are used really commonly in moulding but I've personally struggled to make good versions via 3D printing. This is mainly due to the materials used - 3D printing generally uses plastic that's a lot more brittle - but also down to the process used. The method of printing layers (mostly used in FDM) tends to makes flexible parts quite weak 'across the grain'.

I've found some blog posts online but was wondering if anyone has any specific tips from their own real-world experiences?

Specifically -
* What's the best material to use? I typically go for something like a Nylon, or a 'Strong and Flexible Plastic'
* The best process to use - FDM, SLA, SLS etc?
* Any tips on the actual geometry. I tend to use this image as a starting point -

but obviously this isn't optimised for printing.

It's tempting to make the parts thicker... but I suppose that this actually just makes them less flexible and more prone to breakage.

Any tips or idea would be gratefully received. Thanks!

 

[GoodCat]

REC FLEX
REC FLEX - from 10 to 40 mm / s
Nozzle temperature 220 - 240 ° С
Table temperature 80 - 110 ° С
It is printed on glass, any film will be firmly welded to the model.
But for flexible materials you need extruders with two rollers, you need to buy a special extruder or modify the one you have.

 

[john12]

You mean that you use glass as the printer bed/base to print the model onto?

Have you had any luck with non-flex materials like Nylon, or am I expecting too much from printing with this? It's just sometimes a big ask to convince clients to spend all of their money on a mould without the hinge design actually being tested first!

 

[GoodCat]

Yes, for this material need to insert glass. I use a piece of tempered glass, but I think ordinary glass will do. In order not to cut yourself, you can blunt the edges with a grinding block. I did this in a basin filled with water so that there was no dust and also if it is done in water, chips on the edge of the glass will be less.
With inflexible materials, it will not work if this FDM technology breaks the part into layers I tried to place the parts in solvents for a short time but this does not help. (
As far as I know, SLA technology allows you to get rid of the problems of delamination, but materials that are photo-cured are too hard for such structures. I think this can happen with the help of SLS technology, but it is expensive.
Alternative method: you can print 3d models of the product, then use the technology of plastic molding into silicone mold. It is cheaper and easier than making a mold, but I'm not sure that the accuracy will be good on such a thin structure.

 

[john12]

Thanks for the advice and information. There's lots for me to think about here.