Ratcheting Z-Axis from X-Axis carriage extremes

With some more wild imagination being applied to the design of a repstrap, I came up with the idea of using the X-axis motor to ratchet the Z-axis. The idea would be to save the cost of the Z-axis motor/controller.

That is that moving to the extremes of the X-axis could push/pull a ratchet to raise or lower the Z-axis. With a M8 thread the pitch would be approx 1mm, so a 4 position ratchet would give 0.25mm steps and the extruded material would naturally slump to the surface anyhow.

Does the concept of having to move to the end of the X-axis screw with the laying of plastic? Can the extruder shut off/restart the material flow OK to have this happen?

Cheers,
Simon.
aka Mungewell.

Interesting concept.

The issues that may need addressing with such a mechanism:
- ratchet may be more complex than simple motor. Good tradeoff, if it can be produced completely via printed parts.
- Path computation may become more complex if Z must be raised temporarily to enter areas surrounded by plastic printed at the current layer (E.G, outline, followed by infill.) May not be an issue.
- zeroing Z, how do you ensure Z axis zero position? Can a human to adjust the Z manually, easily?
- Designs limits multi-head printing options.

I played a little with the concept, and maybe a scheme like this would work:


In answer to BeagleFury's questions:
1) Should be 'printable + a couple of springs' (unless someone figures how to do these reliably in plastic), but the main concept for RepStrap is that you don't have a 3D printer at all so you would have to be able to make with hand tools.

2) Could end up with string everywhere. I have some other ideas would would involve 'messing' with the path/gcode anyhow.

3) Zeroing done with optical vane (if required). Manual setting could be via rotating threaded bar by hand, or just whacking the mechanism the appropriate amount of times.

Cheers,
Mungewell.

Hey... That's a really neat mechanism!

It might be quite slow... How would you turn it backward, by the way?

Edited 1 time(s). Last edit at 02/09/2010 10:36PM by jbayless.

If you push the 'red frame' from the right the nut will be ratched the other way ;-)

Simon

I 'played' some more and came up with this.



Any comments on the manufacturability of this would be welcome.

Cheers,
Mungewell

I saw that pushing it from the other way will lower it... I was more wondering how to push it the other way. I don't see a very good way to do that.

I don't see any particular manufacturing difficulty; it looks like all of that could even be done with printed parts

You could have a rigid arm traveling the length the X-axis carriage, so that going to that extreme 'pulls' the mechanism the other way.

Simon