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[Javier López Picazo]

Hello,

I am writing because I am developing fingerboard wheels as a new product within my own brand. I professionally manufacture fingerboard decks and concrete obstacles, and now I am expanding my catalogue with cast and machined wheels.

The wheels have approximate dimensions of 8-9 mm in diameter and 4-5 mm in width, with housing for bearings. In this small format, the behaviour of the material is critical.

I have tried various casting polyurethanes, mainly Shore D (65-75D) type rigid/semi-rigid resins, but the results have not been satisfactory:

-Too light in feel
-Low resilience
-Poor grip or, in other cases, brittle behaviour
-Issues with bearing housing (tearing / low deformation capacity)

I have also tested material from commercial skateboard wheels (marked as 102A), but at finger scale, they are too soft and have excessive grip, so they do not serve as a direct reference either.

Therefore, I am looking for guidance to find a more suitable material, without closing the door to any approach.

Indicatively, the material I am looking for should have:

-High functional hardness (high Shore A ~97-98 real, Shore D (65-70)
-Low surface tack (non-sticky)
-High resilience / good rebound
-Good tear and abrasion resistance, as well as being dense, in other words, having a high weight so that the fingerboard doesn’t feel light
-Good behaviour against mechanical interference (insertion of bearings)
-Suitable for small parts, preferably processable by casting in mould

The functional reference would be closer to urethanes used in high-speed industrial wheels or rollers rather than materials designed for impact absorption or high grip.

If anyone has experience with:

-High hardness elastomeric polyurethanes
-Low tack / high rebound urethanes
-Industrial systems for rollers, pulleys or even high-quality micro-wheels, even Shore D that do work in this type of application

I would greatly appreciate any material, manufacturer or product family recommendations, or even warnings about paths not worth pursuing (some of which I have already learned the hard way).

Thank you in advance, and I am happy to provide any additional technical data as needed.

Automatically translated from: Español

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[jclemencio]

Hi Javier,

This seems like a very intriguing project, although finding the optimal material for the wheels does indeed pose a significant challenge.

Selecting the perfect material for your specific application might be difficult and might require you to experiment with various options to see which one is the best fit. You can review all the materials we offer and their corresponding datasheets here: https://xometry.pro/en-eu/materials/

Some potential solutions that may work could involve using POM in CNC with CNC machining, or SLS or MJF with PA12, which offers more rigidity, or TPU, which provides more elasticity.

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[Javier López Picazo]

Hello Clemencio,

Thank you for your response.

After conducting several tests, I’ve been able to rule out rigid polyurethanes, as they are brittle and crack when the bearing is inserted. Additionally, they are low-density materials and have very little weight. Lately, I’ve been experimenting with elastomeric polyurethanes, and the results have been very promising as these materials perfectly meet my requirements. The only challenge is finding materials in this category with a hardness exceeding 55D (I’m aiming for a hardness of 65D). Despite this, I believe I’m on the right track with this family of materials; now it’s just a matter of finding the right hardness.

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