I have a little 3D printing project I am working on for my adult son, Steven.
His main avocation has always been playing and collecting percussion instruments. He is an outstanding drummer as well as being a fairly abundant collector. He does play what he has, just not all at once.
He has a couple of snare drums that have broken a tension bracket cam that is made from plastic. Two drums with the same hardware with identical failures (cracks) in the plastic cam follower.
There is a design flaw as the breaks are identical. There is a very high stress area that has a sharp 90 degree tab that the tension adjustment screw passes through the tab. The 90 degree angle is the failure point on both.
We have designed an identical plastic replacement part using Rhinoceros 3d CAD and exporting a .stl file to Simpilfy3D CAM software for creation. The design now has a fairly large fillet where the 90 degree tab angle was located. This should relieve the stress point.
We have made several parts and broke one trying to install it in the tension adjustment bracket. The old part came out because it was broken and we broke the new one trying to force it back into the bracket.
There is a rivet that needs to be drilled out to fully disassemble the components as we have discovered this will be necessary. The rivet is not a critical part and we think it can be replaced with a SS bolt and nylock nut. There is plenty of room for the head and nut. The bolt will also make the tension device much more serviceable if needed in the future.
The design flaw in the cam follower looks like just weak engineering. The drums are over 20 years old, but the same hardware is still being produced. Perhaps a planned weak point? We thought about that, but it is doubtful.
I feel fairly certain there is not a huge world market for this part. It may not even be available as a replacement part because of the riveted construction of the tension adjuster. Probably the only standard option is to purchase the entire assembly.
In any case it is interesting and a challenge. The part could be made from metal using a CNC mill and a lot T&E (Trial and Error.) Far more effort than 3D printing in plastic.
This prototype is using ABS plastic. There are other filament types available (like nylon) but a whole spool for one part is not efficient. If our design is good, we can outsource the print file to a commercial 3D print shop and get any material we desire. So this effort and material is a good prototype process.
The resources available today for making things are wonderful.
|Preliminary hand drawings for measurements before CAD.||The master drawing created in Rhinoceros 3D CAD|
|3D printing underway.||Part just completed printing. Build supports shown in place.|
|This is the same part cleaned up a bit, supports removed.|