It’s quite the rabbit hole, but very important consideration in designing a 3d printed object. The material type, the orientation of the part in relation to the layers.
I see a lot of discussion online about orientating the print, with many well established print / designers using quite unusual orientations of what might seem fairly straight forward planar objects.
A lot has been written about this.
Prints naturally will sheer along the layer lines with almost all filaments, so the print orientation really depends on where the most force is expected. Ideally you design your pieces so the force is applies perpendicular to the layer lines.
When that’s not possible, people try to print their objects at weird angles… like printing simple tubes standing at an angle to achieve longer layer lines for more adhesion between the layers. It’s a game of quickly diminishing returns in my opinion, those few percents of more layer-to-layer contact surface is usually not worth the effort.
Much easier to just get out of your filament comfort zone and just print it with stronger stuff.
To side track for a minute, a lot of people don’t get the point of TPU for AMS. Why print a TPU that’s not really flexible? Exactly for the layer adhesion and durability. TPU bonds layers together like almost nothing else and takes a massive amount of abuse.
This print was particularly problematic. I wanted to print it in standard orientation for the finish and no support. This results in the layer line being parallel to the connection of the shoulders. The squeezing of the shoulders or finns caused delamination of the layers.
I had a few different designs thoughts which I may go into later but i was comparing print materials and as @DrKronos suggest TPU (95A I had at hand) was the best for this application. It provided the flex needed for the grip and the strength durability for repeated use.
There’s a few things you can do to make prints stronger:
Avoiding sharp corners at stress points is the main thing. Generously filleting or chamfering those areas increases strength.
Printing things in multiple parts can also increase strength, especially when you can assemble them with layer lines going in different directions. The area where you insert one part into the other will then have double the wall lines a single part has.
In the same vein, counter-intuitively designing holes into your parts can actually make them stronger. Every hole ads another double set of wall lines to that cross section.
In your example, the first thing that comes to mind is chamfering or filleting the edges where the three mount parts meet the base (unless that hinders movement of course).
Thanks @DrKronos - interested in the strength benefit chamfer might give.
For a while i was going down an inserted metal pin. It was a nice solution but not right for this model.
I create the load measurement rig to see how different mods changed the strength - but i came to the TPU solution and kinda shelved it.
One thing that did surprise me was the varying strength of different brands and flavours of PLA. I got 1 of the PLA version going up to 300N - it bent the 3D printed cogs on the rig and exceeded the rating of the load cell. You can see the thing bending here.
The metal pin insert was a nice solution - I never got round to testing the strength increase as I exceed the load cell. Probably need to go up to 100 kg, but funds and energy ran out.
Pause the print insert the pin and make sure its below the current print layer before resuming.
