Hi All.
I have the need to print this part that will take a lot of stress. It’s a bracket for a gas strut I’m printing for my Polaris Ranger 4x4 and it will act as a door damper when opening and closing the doors. The gas strut is under about 30 pounds of pressure and I wanted to get some opinions of strength settings when printing. My test prints have been with PLA with the walls being 5mm thick. So far no issues but I want to strengthen it the most I can before having to go to a carbon fiber or something else (recommendations are welcome). FYI the arc will mount to the roll bar in the Polaris and the single hole will be a stud the the gas strut snaps on too.
When printing functional parts, you have to consider the layer lines. 3D prints are anisotropic, strength-wise. They separate much more easily along layer lines than perpendicular to them. So you want to print your model oriented to ensure the layer lines are perpendicular to the stress vector that’ll be applied to the part.
For the model you’re showing, it wants to be printed standing on one of the ends, not oriented the way you show it. The way you show it, it’ll break more easily.
Then, you want to use 100% infill. Nothing is stronger than 100% solid plastic. Rectilinear is good because the fill layers will be printed at 90º to each other.
Lastly, 3D printed parts are inherently weaker than injection molded parts. You want to add some structure in the areas where the stress will be higher, to compensate for the fact that the part’s printed instead of molded. And fillet the seams where the top part meets the bottom part. Stress fractures love sharp angles.
There are some 3D filaments you can harden with a heat treatment after printing. But I would use CF Nylon on this.
Obviously I left out the holes. But this will work unless the holes that bolt this to the bar need to be aligned with the arm that connects to your piston. If that’s the case, I can still see a way to do it so you can print it like this.
The holes will come out slightly oval but you can fix that with a twist drill. That’s what I do with my functional parts. Print defines the hole’s location, drill bit makes it round.
I do print it standing up…I should have mentioned that. I didn’t extend the flat piece and for that reason I use supports but I do like your idea of extending the flat piece that way there are no supports, plus it would probably be such stronger.
I would make it solid and also add some ribbing on the outside. Also print it so that the layer line work for you. If you print it on its end, its gonna snap in half easily. (think of wood grain). You can run cf-nylon through the ams but you may find that normal nylon is better. It can flex a little.
Added some outside ribbing as well as RocketSled suggested that I fillet the joints. Might have go overboard on the fillets but should be strong. Again, Im mocking up in PLA but will eventually do it in CF.
