The mechanism for the Umbrella Man has been rebuilt with the O-ring pads. This appears to have fixed the ticking problem. It has been running continuously now for several days without getting noisy, so hopefully it will stay quiet. My sister’s end is coming along also, and it is looking great.

I expect I will ship the mechanism off to my sister tomorrow unless it suddenly re-develops a noise problem.

To eliminate the ticking problem in the mechanism for the Umbrella Man, I decided to try adding O-ring snubbers between the pully shafts and the bearings. Because the O-rings are 1-mm in cross section, I was afraid that if I kept the original 5-mm shaft diameter, the shaft diameter in the O-ring grove of 3-mm might be prone to breaking (resin printed parts are fairly brittle). So I increased the shaft diameter to 6-mm. This necessitated going from bearings that were 4-mm thick to 3-mm thick, which required reprinting the baseplate.

In the bottom view you can see the white plugs which support an overhang which supports the bearings. They are printed with a special breakaway plastic and are easily knocked out after printing.

The pully is shown still attached to its support structure. With fused filament printing, a structure like this would not be required; it could print right on the printer baseplate, and it would detach as it cooled. With resin printing, there is no cooling, and parts have to be pried off the printer baseplate. Thus, most parts are printed on a sacrificial base, connected to the part by small posts. The touchpoints to the parts are very small, so these posts are easily broken away. This leaves small defects at the touchpoints, which in this case don’t matter, but otherwise they can be sanded away. Because the top edge of the O-ring and c-clip grooves was unsupported, they are slightly angled, but for this application this was better than dealing with the touchpoint artifacts.

My sister’s latest project is a man standing with an umbrella over his head, with rain pouring on him from the umbrella. Her first idea was to use real water, but I persuaded her this was a bad idea for multiple reasons (clogs, algae, mess, the list goes on). So, she came up with the concept of using wires painted with a black and white spiral. When these rotate, it should look like stuff coming down. There are thirty of these all needing to rotate. The sculpture is only about 12 inches across, so there is not a lot of space. So, I came up with a drive concept that involves using belt driven pulleys.

The base plate is 3D printed on a fused filament printer and the pulleys, which need remarkable precision, are printed on a resin printer. A pair of miniature ball bearings supports each pulley. The belts are made from NinjaFlex 3D printing filament. It works well for a while, but then it starts ticking. I think for some reason the pulley shafts are loosening up in the bearings and shifting as they revolve causing a tick. I am currently redoing it using O-rings between the pulley shafts and bearings, which will make the pulleys less sensitive to shaft size and provide a damper.