Don't know if it's been discussed before and this may be old hat for some, but I wanted to give this thread a tip on designing 3D printed parts for use in RC, since I've done a few parts for my RC's, and I'm also working on a 3D printing guide for my company. Mostly what I print aren't suspension or structural, but my
TLR 22 4.0 knuckle adapters for me JRX Pro SE are a good example. It's a small part that didn't usually break in stock form, but mine has taken quite a few hits, including a friend that had a propensity to turn straight into a solid object at full throttle.
One thing I think everyone should keep in mind when 3D printing parts is you
shouldn't try and copy the original exactly, because the design of mass produced parts are largely driven by the manufacturing process, and often compromise the performance. Here's an example.
The original part in black is injection molded. Injection molding requires you to maintain a relatively consistent wall thickness to avoid defects, and all features have to be reachable by a surface on the tool. There are also sometimes provisions for "knockouts" that don't need to be there (see the four round spots in the ribs). Ideally, the tool has just two sides but you can do "side actions" to get geometry that would otherwise create an "undercut", though this increases the cost of the tool so designers try and avoid it. This is why molded parts have lots of ribs. They're adding strength to a feature, but are trying to adhere to the consistent wall thickness as much as they can.
But ribs really aren't ideal for strength, and this isn't the best way to design a part for that. In most parts, the outermost grain bears the most load, so the more material you can put there, the stronger and more rigid the part will be. But a rib only allows for a small area of material to be added where it's needed.
The part on the right is designed to take advantage of 3D printing. The infill can be reduced quite a bit and all of the outer surfaces are filled with material. A simple roller doesn't need a lot to be strong, but if you look back at my Pro SE adapters, other than being C shaped, it's not "cored out" for wall thickness and the material is mostly where it needs to be. This is also in PETG, btw. This part hasn't failed, but if it did, I could fill in that C and it'd be a very solid part. I just didn't because I didn't want to work to get that king pin all the way through as I was iterating. The part in the center was modeled by a coworker who went so far as to recreate the knockout pads and it actually took longer to print than the solid part to the right. It also had some quality issues because our printers are old and need work, but the "full" part did better because the printer wasn't lifting and reversing as much to reduce stringing.
The caveat to this is that this rule is for FDM printing where you can control the infill and wall thickness with machine settings. With other processes like DLP, laser sintering, multijet fusion, you have to core out the part in the model, or accept you will have a solid part. The only downside there is you may end up with a bit more weight while not necessarily adding strength, though you may be able to do something clever like design the part hollow and model a couple of holes in strategic places to allow excess resin or powder to come out. For reference: I seem to recall once reading that there was no strength benefit to infills greater than 30%, though I don't have that source to cite, so don't quote me.
Oh well, not a complex piece, and my simple brain and sketchup made it work.
All stock hardware and no holes drilled. Only lifts the trans 3.5mm, which I don't think will be much of an issue.
