What are the best Z couplings for the Prusa I3

I was wondering what are the best couplings to use on the Prusa I3. I am rebuilding an old I3 that I have, but I plan on switching to 8mm lead screws. I have never been sure which couplings are the best, I have always just used the spiral aluminum ones. Any advice would be greatly appreciated.

I think the biggest problem with the "threaded rod" type systems is that the rods are actually quite a bit smaller than 8mm so that they don't line up very concentric to the motor shaft. Also, mine weren't very straight either.

Unfortunately, I don't have an answer for your question. I reworked mine by straightening the screws as best I could and to use shop-built rigid couplers made on a lathe so everything is concentric and rather than pinch the rod with set screws, I tapped the hole for M8x1.25 so the rod threads directly into the coupler.

I'd recommend the lead-screw approach, but I haven't done it myself (yet) because I haven't been able to find a reasonable source for T8x2 single-start lead screws and nuts. I'm not satisfied that using a 4-start lead-screw (8mm effective pitch) would be a good idea. You lose over four times the resolution of the z-axis. Of course, it may still be better than the threaded rods, but I haven't heard from anybody making the switch. Maybe I'll give it a try since they seem to be pretty cheap on ebay, etc.









Edited 1 time(s). Last edit at 02/19/2016 08:58AM by hoxsiew.

I use 4 start T8 lead screws and also turned solid couplers. It took me a couple of goes to get it right as getting the lead screws to sit concentrically with the motor shaft was difficult. For the final version I turned the ends of the lead screws down to 5mm to match the motor shaft which allowed me to use a single uniform bore the full length of the coupler.

I don't find the 8mm lead to be much of a problem, but I haven't tried to print with very small layer heights. I normally use between 0.2 and 0.32 mm layers.

Check out the IGUS web site they have 5 to 8 mm coupler without that spring section instead they use an isolation material zlw 0630s nema 17