Anybody interested in a rotary (slide-crank-ish) printing bed lift?

Hi guys, just wondering if anybody would be interested in a design that is completely non-liniar for lifting a platform/bed using rotary-only motion. I have envisioned a way to adapt the slide-crank mechanism and use a number of these to constrain the vertical motion.

I have been researching solutions to move a larger or heavier bed and the latest trend i've seen is using one motor turning 3 leadscrews with one belt. It looks expensive (yet professional/industrial grade) and is surely not reprap.

My solution would be mostly printable (minus bearings) yet more complex, which could introduce errors like play in the links' shafts, etc.



One last thing: should we ditch moving the bed if it is larger/heavier than the accoppanying extruder(s) moving in XY direction and move the extruder on Z too?

Your (constructive) toughts please: ...

Edited 3 time(s). Last edit at 10/12/2015 05:00PM by realthor.

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RepRap Lander concept on Concept Forge
RepRap Lander concept on RepRap Forums
My Things, mostly experimental stuff

What about something like this

[en.wikipedia.org]
a printer that starts flat and then rises.

Edited 1 time(s). Last edit at 10/13/2015 12:25AM by MechaBits.

Hi MechaBits, the sarrus linkage has been tried before for lifting purposes in the 3d printing community (http://forums.reprap.org/read.php?185,450966) and several design variations have been proposed in the "Solutions for Wally" (a simplified version of the Compact Space Crank) or even this Delta Sarrus Linkage concept. But none of them address the further questions: how are they going to be moved, how are the dead spots addressed and what solution for reduction are they going to use and where will that fit in the 3d printer's volume.

- How would the sarrus linkage you propose be actuated? Would you put a motor at each elbow joint? That would be the only way to avoid dead spots/singularities.
- How would you gear down a stepper to obtain a resolution that is 3d printing acceptable?
- If you need a large red printing bed, you get to put the green pairs at the center of the red bed's sides, so you end up needing more than two green pairs, which will get it closer to my design above. This will also increase the need to put a motor at each green pair.

There has been one concept on this forum I really liked and that is Nic Stewart's Modified Sarrus Idea, which has a higher range of Z translation than the normal sarrus. The same thing I am trying to do with my design but the issue I am having is a simple way to avoid the ded points/ singularities in a simple manner. That I didn't find so far.

Thanks.

Edited 1 time(s). Last edit at 10/13/2015 05:11AM by realthor.

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RepRap Lander concept on Concept Forge
RepRap Lander concept on RepRap Forums
My Things, mostly experimental stuff

Here's how can this be done with a gear&pinion for gearing down to help resolution and a cable-drive instead of a belt:



The only downside that I am yet to solve is the controlled rotation of the currently-free-rotating arm which is going to have precision issues at the dead points (perfectly vertica in both directions and when the two arms become co-linear, passing by at the centre of the blue wheel)

So far the only non-printable vitamins are the bearings.

I know that this can be further refined to a simpler solution of the same line of tought. At the moment, to control the free-rotating arm, I have to use this straight line solution https://youtu.be/HmnA6E82-Wk which involves a belt between a gear bolted to the crank and a similar gear bolted to the free-rotating arm (link). The video is more explanatory than my explanation.

Note: this can be done with only 2 cranks at 90 degrees but I am trying to lift a potentially large bed and don't want to have any issue due to the bed being cantilivered etc.

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RepRap Lander concept on Concept Forge
RepRap Lander concept on RepRap Forums
My Things, mostly experimental stuff