In comparison to Taulman Nylon 618, Nylon 645 is an industrial type material which is much stronger, has higher rigidity and meant to use in industrial manufacturing. It can be printed in a solid piece, machined with CNC and be comparable in terms of strength.
Note on Nylon 645 - It is designed as an industrial nylon in comparison to 618, which can be used to print smaller parts. In order to achieve optimal layer adhesion, a larger layer height is required when printing for 645. A 60% of nozzle diameter height is recommended by Taulman.
A few notes on printing with nylon 645:
We find that printing with a 0mm retraction helps reduce bubbling in your print as water is evaporating from the surface of the filament. If possible, try to print one print at a time to reduce bubbling further.
Always use a raft when printing with nylon - even with a bed adhesive. The raft will come off easy and you will have a perfectly even surface - no curling.
Specifications provided by Taulman.