I wish we could find a better solution than grub screws for attaching pulleys to shafts in 3D printing. Small-scale requirements make it difficult to use other industrial systems.
Grub screws often loosen under the effect of vibration even with Loctite. They also introduce eccentricity. And the tip of the grub screws marks the shaft, making it difficult to remove the pulley.
Any idea how we could improve this?
#3dprinting #3dptech #3dprinting_tech #pulley #motion #belt #grub_screw @3dprinting
@bear_lab @3dprinting If you really want it to be permanent, use loctite / thread locker on the motor shaft.
I haven't had blue loctite (242) on the motor shaft give up, but you can use permanent red loctite (271), or if you really want to go all-in, retaining compound like R-638. R-638 will fill a 0.25mm gap, and is fairly high viscosity, so put it on without grub screws to limit eccentricity. Its working time is limited to 4 minutes.
The 600-series retaining compound has a wide variety of max gap, viscosity, and initial cure time. They all are 24h full cure time though.
@bear_lab It will be more concentric than a set screw... Just don't load it while it sets and it will be closer to concentric than anything else that comes to my mind
It won't be adjustable, so get pulleys that are much wider than the belt. Misaligned flanged pulleys would certainly create artifacts. Could even go with non-flanged pulleys on the motors and flanged pulleys elsewhere. But I don't know about availability of non-flanged pulleys, haven't looked.
The classic solution for this problem is of course close tolerance holes and shafts with keyways and keys. But at this size that's kind of hard!
Hmm. Given my recent fascination with rotary broaches, I could imagine making a pair of broaches (male and female) to cut matching 1mm keyways in motor shafts and pulleys. 🤔
@mcdanlj yeah a lot more concentric than grub screws for sure.
Yes for flanges it is not an issue, I already use a wider pulley than a belt and make sure everything is aligned.
Thanks for all your comments, very interesting points.
Greg Saunier
Michael K Johnson