Question about designing for TPU
I've printed a few things with TPU so I know how to work with it. This question is more of a design question. I'm working on a model that's basically a hollow tube to slip onto another (solid) tube. I'm looking for some advice on tolerances. Sure, I can try a few different values but it may save some time if anyone would be happy to share their experience. Given that the material is flexible, my thinking is none to even negative clearance as I don't want it to come off easily.
@fuchsr
Ok I'll say it, I almost feel as though this is a set up, but,,eehhemmm, could you post a Zipped Up .3mf project file? 😜
Also what TPU did you have in mind fuchsr?
If NinjaFlex you could probably go with a 1:1 for ID. to OD. tolerances because it flexes so much if it's something like Overture at 95A you could possibly do a slight taper on the insert and use soapy water to get it fitted if that can be an option for your application. The durometer of the two materials will make a difference to the design.
Hope this helps
Swiss_Cheese
The Filament Whisperer
What? 3mf? Zip? Huh?
Seriously, the design at this point is just a hollow cylinder around a solid cylinder so there's nothing to share. Eventually it'll be a holder for an Airtag that goes on the bottom of the transmitter for electronic dog training collars.
The TPU is in fact Overture 95A. I like your ideas. I'd rather err on the side of being a bit tight than slipping off to easily. Not a great idea to lose the airtag that is supposed to help you find your transmitter 🙂 Didn't think of the soap trick. That makes a lot of sense.
I'm guessing this is a fairly small part.
Thin TPU stretch is differential according to the direction of lay of the filament. It does recover quite well, if slowly, from stretching so printing at 0, or even -0.1mm rad tolerance works, especially if you can pre stretch it off the part and then fit it swiftly as it recovers.
Instead of soap you can use a polyurethane contact adhesive, used wet as lubricant (don't follow the instructions on the pack) and/or finish with a collar of heatshrink tube.
Cheerio,
Are there any more specifics you can give other than tube-on-tube? Because scale makes a difference. So better grip for a pen/pencil would be different from a bike handle-grip which would be different from a beer cozy.
When someone asks you if you're a god, you say, "YES!"
Thank you all for your input. This is why I love this community. Reminds me of when I was a kid, I used a dial-up modem a la "War Games" to connect to the "internet", and we had these hacker groups on electronic bulletin boards. It was true communities where people genuinely helped each other. The state of the 3d printing community has a similar feel—has not yet been taken over by Facebook...
Anyway, so seeing all the great response, I've spent an hour last night to actually do some measurements and take my idea to the draft phase in Fusion. Attached is the outcome of this exercise. It's a zip file with the step file and the .f3z (it contains an imported mock-up of the Airtag). As I said the top will slip onto a (somewhat rubbery) transmitter, the bottom is for the airtag. Both need to be reasonably tight to not come off easily but a normal human being should be able to push the sleeve over the transmitter. So currently it's modeled on the outer diameter of the transmitter, no offsets. There's clearly overhangs in any orientation but I don't see that as a problem; there's no functional significance to those surfaces so looks don't matter. Any additional comments are welcome. The TPU is showing up on my doorsteps today.