I was so, so wrong.

3D Printing
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1

I was so, so wrong.
http://ei8htohms.tinyparts.net/?p=1032

2

Would lubricating the couplers help?

3

Yeah, I thought about some dry lubricant of some kind, but I really just need to stabilize the gantry I think. Maybe I’ll try lubricated Oldham couplers again at that point. Thanks!

4

Oldham couplers HAVE to have thrust bearings on the front and back of the screw to work correctly. In most 3d printers people forgo thrust bearings because the forces involved are so low there aren’t adverse effects utilizing the motor itself as a thrust bearing in a since and they are typically using a coupler that can’t stretch.

Oldham’s typically clip together and have some force holding the three together but you can’t rely on it. You need to have your screws constrained in their axis of motion (you can’t pull or push the screw along its travel) otherwise the oldham’s won’t function correctly.

5

Yes, that seems to be the case and I’m not sure I’m ready to try to install thrust bearings just yet. Thanks!

6

I wouldn’t expect you would be. Its a huge level of complication that’s just not needed at this level of machine. What were you trying to fix with the oldham’s?

7

I’m trying to address Z wobble without switching to thinner, brass rods (I’m using 8mm Igus trapezoidal lead screws and Dry-Lin nuts and desperate to capitalize on their potential). The proper solution is just to constrain the gantry, so that’s the direction I’m going ultimately, but now you’ve got me thinking about thrust bearings and I think they could be installed at the top of the bot without too many tears. I love the idea of taking the weight off the motor shafts too.

8

John, I love all your effort here. If you are open to it, let me fund your research. Just send me a shipping list and let me know if I can help. In extremely interested in your findings. Your work coil benefit others. Perhaps some sort of an upgrade kit for other Printrbots could follow.

Great work!
Peace,
Brook

9

Thanks @Brook_Drumm , very kind of you. I’m happy to do it. Please do read my latest blog post on the subject though. Progress.