Is TPU the best material for this?  

RE: Is TPU the best material for this?

there are many different types of tpu(varying levels of harness/softness).  I'm having trouble picturing what it is they are being used for.  You said they are shearing off.  Are they load bearing?

RE: Is TPU the best material for this?

@ssill2

They shear off when being put away incorrectly as part of the foot sticks out (bad design). In normal use they are load bearing at 500kg spread over 4 feet (8 per 2 x 1 deck). The lower photos show them folded up where you can see the part that sticks out. If they are slid together then this can tear the foot off. Replacements are almost £30 each while I've found some tough TPU at £18 per roll here https://amzn.to/3x2NT9o They'd probably be OK in PETG but need a little flexibility so they don't crack. Thanks for your help.

RE: Is TPU the best material for this?

@trevor-wilkins

Ah that's much more helpful thank you.  I've never tried putting a significant amount of weight on tpu..  The share hardness scale has the A and D scales.  https://www.smooth-on.com/page/durometer-shore-hardness-scale/

There are likely more experienced folks on here that have used a bigger variety of TPU than I.  I'm not sure if you can get it over there, but Ninjatek makes a 75D filament called armadillo https://ninjatek.com/shop/armadillo/

That seems like kind of what you'd want in your case.

RE: Is TPU the best material for this?

The stuff you linked is 85A, so very soft.  I don't think you'd want to be supporting a stage on it.

RE: Is TPU the best material for this?

I just printed this belt in Ninjaflex, which is also 85A. I think it would be too soft for your application.

RE: Is TPU the best material for this?

@ssill2

This is all great information. Thank you for your help!

I'll see what we can get over here 🙂

RE: Is TPU the best material for this?

@trevor-wilkins

Yeah seems like you definitely want something on the D scale.

RE: Is TPU the best material for this?

TPU would be my choice for this application. But check the price first. Maybe it's cheaper to buy replacement instead, especially if you need many of them.

RE: Is TPU the best material for this?

I'd suggest something around 98A which is around the toughness used to replace leather in shoe heels which is a similar loading.  It's slightly easier to print than 85A.

You can modify the flexibility of the part by varying the amount of fill.  Further modification is possible by selecting either a fill with closed cells, or one where all the voids are connected, effectively one, and then choosing whether or not to connect the fill space to the atmosphere.  Closed cells make a 'bouncier' part.  Open cells are softer and absorb vibration better.

Cheerio,

RE: Is TPU the best material for this?

@diem

If it's load bearing I would thing it'd be possible to go too light on the infill.

RE: Is TPU the best material for this?

And also a tip, depending on how the feet are put down when theey are unfolded. You could experiment with your own design so perhaps they dont stick out too much and in turn get sheered off.

RE: Is TPU the best material for this?

also I would think you could orient the part so that the shearing direction is perpendicular to the layer lines.

RE: Is TPU the best material for this?

@ssill2

If it's load bearing I would thing it'd be possible to go too light on the infill.

I'm sure you are right.

The beauty of FDM is that you can tweak and rework the design until you reach an acceptable result.  The end result might be a superior part...

RE: Is TPU the best material for this?

All great suggestions, thanks.

I agree that it may be I can come up with a better design, it does seem that the part that sticks out and catches is not necessary.

A roll of 'Armadillo' TPU as suggested would be cheaper than buying two replacement feet so should be very cost effective (solid fill would use 50m).

Just waiting on a filament sample to see how it prints.

Photo of test so far.

Thanks again.

RE: Is TPU the best material for this?

@trevor-wilkins

Should be an easy redesign and easy print, my recommendation if you decide to print is the A scale use a 98, harder then that becomes more slick, for example I have NinjaTek Armadillo here it prints very well and has a durometer of 75 on the D scale, it's almost unbreakable however at that hardness becomes slick on surfaces such as concrete or wood floors. it's very much like nylon in its strength.

the 98A if printed completely solid with be very hard and super tough, but will offer some skid resistance and a bit better vibration absorption.

Nikolai's advice is how I would start this adventure, see if it's cheaper to buy the feet first.

Good Luck

Swiss_Cheese

RE: Is TPU the best material for this?

well I wasn't able to see your latest post before I posted this, since your already getting the Armadillo first thing to do for sure is dry it, I'm not saying this lightly Dry it! before you start printing it and dry it while your printing it if you have a means by which to do so.

Enjoy

Swiss_Cheese

RE: Is TPU the best material for this?

@trevor-wilkins

Listen to swiss 🙂  He knows what he's talking about 🙂

RE: Is TPU the best material for this?

@trevor-wilkins

well? how did things turn out for you?

RE: Is TPU the best material for this?

@swiss_cheese

Well, I haven't received a reply after asking for the sample filament yet and I don't have any suitable to use. I ordered some original replacement feet in the meantime but they're not going to be delivered for another 10 days.

Whatever happened to good old fashioned service?

We've just had a bunch of events cancelled as the Covid regs are being extended so I can't justify paying out any more at present.

It's still on the cards for the future though 🙂