motor shaft coupler too flexible?

Hi guys,
I got these couplings with my prusa i3 kit.

I was surprised how soft they were and how easy I could compress them vertically.

Now I´m wondering, if that would reduce z-axis accuracy?

Imagine your extruder is on the far left side, where also the x-stepper is.
The whole weight would compress the left coupling a bit.
Printing in the center or even on the right side, would compress the right coupling more and more, expanding the left coupling at the same time.

To overcome the vertical compression, my idea is to insert a silikon tube ( 4mm AD ) between the motorshaft and the M5 rod. Now the weight of the x-carrier and extruder rests on the motorshaft and not on the coupling.
This way, the compression would be dampened a lot, while the side-to-side flexibility of the coupling stays the same.

What do you think?
Sorry, if someone has posted that before.
Olaf

No, they don't reduce the Z-axis accuracy in any significant way. Their flexibility is in fact on purpose.

You can try to print with and without your silicon tube idea and report on any observed differences, but personally I doubt there will be any.

Stick a ball bearing down the hole. Stops the compression and keeps the flexibility.

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[3DKarma.com] - suppliers of quality, affordable 3D printer kits and filament for the UK market.

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3dkarma
Stick a ball bearing down the hole. Stops the compression and keeps the flexibility.

Ditto here. You can try to print with and without a ball bearing inside the coupler and report on any observed differences. Again personally I doubt there will be any.

Other things you can try that I personally doubt will make any difference in print quality (or at least any measurable/observable improvement along the Z-axis):

- Wrap the coupler in duct tape (hey, duct tape usually helps, doesn't it?).
- Put magnets around the coupler.
- Arrange stones around the 3D printer, preferably in the same pattern as Stonehenge.
- Paint the coupler in pink, Hello Kitty style.

Edited 1 time(s). Last edit at 05/08/2015 01:51AM by AndrewBCN.

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AndrewBCN

Ditto here. You can try to print with and without a ball bearing inside the coupler and report on any observed differences. Again personally I doubt there will be any.

Other things you can try that I personally doubt will make any difference in print quality (or at least any measurable/observable improvement along the Z-axis):

- Wrap the coupler in duct tape (hey, duct tape usually helps, doesn't it?).
- Put magnets around the coupler.
- Arrange stones around the 3D printer, preferably in the same pattern as Stonehenge.
- Paint the coupler in pink, Hello Kitty style.

You forgot crystals and dancing naked around the printer in a fullmoon night at midnight helps too!

But I don´t understand your point of view?
The coupling has three degrees of freedom, we only want two of them,
We can´t put the rod and steppershaft directly together, because their ( more or less ) flat ends would block any flexing.
That´s where my silikon tube comes handy...or maybe a piece of wooden toothpick? Anything that supports the weight and doesn´t block the desired DOF
Olaf

The proof is in the printing, Olaf. Try it, see for yourself and then report back to confirm, preferably with pictures (not of you dancing naked, I mean pictures of the prints...).

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3dkarma
Stick a ball bearing down the hole. Stops the compression and keeps the flexibility.

Thanks 3dkarma!
At first I was puzzled by your suggestion, but then the penny dropped..you´re talking about a single ball!
Sure that´s the best way to reach my goal.

I wouldn´t be happy if I had to dance around in a cold spring night
Olaf

You're asking the right questions! What's really going to bake your noodle is thinking about what happens when the guide rails and the frame of your machine flex...

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o_lampe
Hi guys,
I got these couplings with my prusa i3 kit.

I was surprised how soft they were and how easy I could compress them vertically.

Now I´m wondering, if that would reduce z-axis accuracy?

Imagine your extruder is on the far left side, where also the x-stepper is.
The whole weight would compress the left coupling a bit.
Printing in the center or even on the right side, would compress the right coupling more and more, expanding the left coupling at the same time.

To overcome the vertical compression, my idea is to insert a silikon tube ( 4mm AD ) between the motorshaft and the M5 rod. Now the weight of the x-carrier and extruder rests on the motorshaft and not on the coupling.
This way, the compression would be dampened a lot, while the side-to-side flexibility of the coupling stays the same.

What do you think?
Sorry, if someone has posted that before.
Olaf

Good News,
coincidently I found 4.5mm bullets are dead cheap. Lots of 1500 or 5000pcs. for airguns are available without the need to slaughter a ball bearing.
That´s plenty of z-rods improvement. ( At least it improves the "peace of mind" factor for me )

Probably they are not perfectly round, but in my case, that dosn´t matter.
Olaf