Thursday, April 27, 2006


Full translation on the z-axis...

I ran one of the z-axes on Godzilla for it's full range of motion, approximately 660 mm. Not as smooth or fast as I'd like, but I think I can tweak that for better performance without a lot of trouble.

Now that I have it working after a fashion some of the weight loss ideas I had for the system a few months back when I was doing design charrettes came back to me.

First off, if we fixed the threaded rod and rotated the thrust collar (nut) we could lose both the bearings and the inertia of turning the whole rod. I suspect that that would greatly reduce the torque required to move the vertical y-axis tower.

Second, if we used a cheap metal ruler on one of the z-axis stages to provide lateral stability for the y-axis towers we could lose about 75-80% of the volume of polymer needed to produce Godzilla's z-axes.

Similarly, if we used a couple of cheap metal rulers held together with reprapped clips and mountings we could provide for both lateral and vertical stability on the x-axis that is suspended between the two y-axis towers. That would drop about 75-80% of the volume of polymer needed in the x-axis.

If I went in that direction the replication time for Godzilla would drop by well over half.

I've been thinking about some weight reduction ideas as well. I think as we work on designing these machines we should pay attention to categorizing practices suited to construction (rather than prototyping) using disposition. One thing that is obvious is that added complexity of shape does not necessarily increase cost, so techniques such as corrugation, or spheroidality (curved sections, as in the joint at the top of a coke can) can be implemented to easily reduce material use. Also, making fixed holes for smallish diameter support rod seems to make a lot of sense. Ideal solutions might not even require support material, corrugation with only one outer sheet should work immediately, or two outer sheets with increased crosshatching towards the top sheet.
Also, there is no necessary limits on geometry as is typical in extruded corrugated plastic, this should allow us to remove or better control the weak direction found in standard examples (by using radial corrugations for example).
Or you can fill the thing with concrete....

Vik :v)
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