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I needed a coupler so I modeled a close copy of the original. I need to pull springs from worn-out couplers. Both printed in PETG. If it doesn't hold up I'll reprint with carbon-fiber reinforced nylon.

paulrussell wrote: ↑Fri Dec 25, 2020 12:29 pm I needed a coupler so I modeled a close copy of the original. I need to pull springs from worn-out couplers. Both printed in PETG. If it doesn't hold up I'll reprint with carbon-fiber reinforced nylon.20201225_122313.jpg

They look really nice. The originals are known(?) to be Zytel and hold up pretty well. I know many originals are still in service after 60+ years, I have one that old myself. And I know you can get Zytel filament. Any reason for not making the replacements out of Zytel? Does it not 'print' well?

- David

DLB wrote: ↑Fri Dec 25, 2020 1:05 pm Any reason for not making the replacements out of Zytel? Does it not 'print' well?

Simply because I don't have any in my filament stock. However, it looks like Zytel is simply a branded Nylon, and I do have the carbon fiber reinforced nylon I mentioned above, and I'll be making one from that later today.

The PETG worked ok, but not as well as an original. So far, the CF reinforced nylon is working great. I made the coupler in homage to the original, but a few design modifications might be in order to best accommodate the differences in material and manufacturing technology.

Paul,

Are you selling any of these? If so, how much for 1 or 2 carbon-fiber reinforced nylon ones?

There is a market. After all my many years with a Mark V and the original couplers - yesterday I broke two. They didn't just crack they exploded into pieces. Without doing anything other than inspecting the setup the third one is working fine. I don't think it was an overload!! I was cutting 4" foam for a chair cushion.

Zytel is a yellowish looking nylon material. Recent couplers are white. I do not think the newer ones are zytel.

My 60+ yr old was yellowish when new. I have yet to damage a yellowish one. Not so the white ones.

Since I only have a few hours use on this, I'm not prepared to say it is ready for prime time. Some abuse and perhaps intentional abuse are in order.

One cosmetic issue is due to the limitations of 3d printing. The best orientation for printing this is standing on end. As such, the underside of the upper coupler is "unsupported" when it starts to print and ends up a bit ragged.
Several possibilities:
1) Live with it.
2) Along with the part, print a removable support structure. This is a common remedy, but wastes expensive material and takes a lot more time. (The coupler currently takes about 2.5 hours to print.)
3) Replace the fillet between the shaft and the coupler end with a somewhat 45 degree bevel -- this would print cleanly. It further occured to me that this might also provide a great visual differentiator for headstock/tool if done on only one end.

If you do start making them I could use a couple of ends to try some things.

It might be impractical for you to keep printing the central tube if it could be replaced by a piece of stock tubing glued to the ends.

edma194 wrote: ↑Sat Dec 26, 2020 12:47 pm If you do start making them I could use a couple of ends to try some things.

It might be impractical for you to keep printing the central tube if it could be replaced by a piece of stock tubing glued to the ends.

That could be a good option. Thanks for the idea.