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[Poppy Robinson]

Hi! Currently working on a small batch of U-groove guide rollers for a linear transfer system, and I’m using a soft polyurethane tread (around 85A Shore) bonded to aluminum hubs. The supplier estimates each roller will handle about 25 kg static load, but this feels low for my application (mainly slow-moving loads with occasional impact). I suspect the failure is due to shear at the bond line under compressive load. Does anyone have experience with similar PU setups? In your experience, is the bond line shear typically the first failure mode under moderate compression, or should I be more worried about core deformation or tread chunking?

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[Arthur Bennett]

You’re bang on the money; the issue is most likely the bonding of the PU to the aluminum. Do you have any insight into the supplier’s procedure for the bond? The surface prep of the aluminum is critical, since the oxidative layer that forms naturally on its surface needs to be stripped before attempting the bonding. They may be only wiping with a solvent, whereas they need to be grit blasting first in order to be sure that the oxide layer is removed, before wiping with solvent.

Depending on how critical it is for these rollers to perform, you could also ask them about whether they could potentially form some profiles in the aluminum for mechanical locking of the PU in addition to the chemical bonding.

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