Cast Urethane Wheelchair Push Tabs

I use these push tabs on my manual wheelchair since I can't grip the push-rim.

I had originally printed tabs using Ninjaflex and they worked very well but over time some broke as the layers delaminated. I needed more and since my 3d printer was down for a while I asked a friend if he could print some. He made one print and suggested it would be much faster to print a mold and cast them from urethane.

We altered the tabs design by adding draft angles to some surfaces so the part could come out of the mold. Then my friend designed and printed the mold and cast the tabs. Another friend installed the tabs and they are working very well. They are a little harder than the Ninjaflex but that seems to be fine.

We did have a hiccup. Originally we had a nut buried in the tab body and the screw ran up through the bottom but when we attached them and applied pressure the rubber could not hold and the tab popped off the push rim. So the friend who was installing them drilled the hole all the way through and bolted them from the top. This is solid and I like seeing the button head M5 screw.

In the end the result is great and another reason to love 3d printing.

And thanks to my friends for making and installing these!

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Excellent design process, goes to show 3D printig can improve quality of life, even just a little. Casting is a lot stronger than printing, although TPC flex would probably do the job equally well, layer adhesion is as strong as the stuff itself. Thanks for sharing!

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Kind regards
Imqqmi

NFAN CoreXY printer:
[reprap.org]

Thanks for your comments! I'm going to look up your recommended filament. Plus I'll be reading about your printer; it looks awesome.

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Very nice to see some practical real-world applications of 3D-printing. I can imagine making a 3-stage mold where you first cast some softer PU, then remove a mold piece to cast the rest of the harder PU. These two should be able to bond together so you have the construction with hard solid PU and a softer part where your more fragile skin/hands have to touch it.

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http://www.marinusdebeer.nl/

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Ohmarinus
I can imagine making a 3-stage mold where you first cast some softer PU, then remove a mold piece to cast the rest of the harder PU. These two should be able to bond together so you have the construction with hard solid PU and a softer part where your more fragile skin/hands have to touch it.

I like this idea very much. Maybe in the future I will try that. Can you recommend a soft PU? We used Smooth-on material for this.

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Quote
Garry Bartsch

Quote
Ohmarinus
I can imagine making a 3-stage mold where you first cast some softer PU, then remove a mold piece to cast the rest of the harder PU. These two should be able to bond together so you have the construction with hard solid PU and a softer part where your more fragile skin/hands have to touch it.

I like this idea very much. Maybe in the future I will try that. Can you recommend a soft PU? We used Smooth-on material for this.

Ahhh Smooth-On is actually already quite a good solution by itself. We used it on the tools on the art academy I worked some time ago. In that case I'm not sure if it's worth going through all the trouble of making a new mold. Unless you like to experiment, which I think you do

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http://www.marinusdebeer.nl/

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Ohmarinus
Unless you like to experiment, which I think you do

You read me well. :-) Sometimes it's difficult to know when to stop iterating.

I will keep looking on the Smooth-on site for materials. I don't have much experience with PU but will try to learn more.

Have a good day!

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