Cast PU will have better performance and lower initial cost, but injection moulded will be cheaper once initial costs are amortised.
Nylon and acetal are very commonly used in sliding door rollers.
Acetal is the hardest with the most creep resistance, and therefore will tend to hold its shape better under constant load. Injection moulded PU will be the worst from the point of view of retaining shape, with nylon somewhere in between.
PU will run quiet where the acetal might be noisy, once again with the nylon somewhere in between.
The cast PU will distort under load, but will recover better over time vs the thermoplastic materials.
Regards
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