Sunday, September 07, 2008


Taking shape... of what, I don't know.

Managed to bodge together an experimental gantry and X axis assembly today. I'm not at all certain this is how it will end up looking, but it's something to play around with at the moment while I work on the Y and Z axis bearing assemblies.

The pipe fittings aren't the most precisely machined things in the world. It takes some fiddling - over-tightening some joints, leaving some loose - to get things lined up right. Even so, one of the bearing assemblies needs some further adjustment, which I'll have to do by re-positioning the skate bearings on the bolts. Oh well... that's why they're there.

Can you give us some dimensions on that thing? What are the actual sizes we are talking about. From the picture it looks pretty big.

The longest sections of black pipe are 24 inches.
Wow! Looks like a bed frame I had one time in another life an eon ago. :-s
I managed to get it aligned better without having to adjust the bearings last night. I've got the parts for constructing the Y axis assembly set aside, so there's a good chance I'll get that done tonight.
If you put your unions on the short cross pieces instead of the longer pipes you would get more travel from the head.

I'd edit your picture if I knew how to include a picture here.
I think I understand what you're saying, but it would result in _less_ travel for the head. moving the unions would not increase the length of the longest section of pipe - which can already be fully traversed - but would widen the X axis assembly, restricting it's movement by the increase in width.
I cut and pasted some stuff from you picture and added an end bearing. I should not make it wider and would save four nipples and maybe one less union. Posted an image in photobucket. You may have to cut and paste the url back together.
No criticism of your work. I'm impressed. Good ideas.


I'd do away with two of the bearings and only use one on the top and one on the bottom and I was fiddling in the garage and think an end bearing could be made to hold it all together.

That's what's in the picture I posted. Really messed it all up but I think you'll be able to figure it out.
I see what you're saying. Certainly worth trying out. By no means is this design final. I'm pushing, at the moment, to get lead screws attached for the two axes of movement I have assembled. Once I've done that (tonight maybe?), I'll certainly give your end-bearing idea a try. The design has already benefited from others' input.

Even after I have it working, there will be plenty left to do deciding what can be modified, enhanced, and _especially_ removed from the design to decrease cost, complexity, and required tooling -- all three are already pretty low, but I think they can go lower.

I've also got a couple new ideas that might allow me to do away with the bearings entirely... saving those for a new post - after I give them a try.

Thanks for the ideas! I'll give them all a try eventually. They're all appreciated.
Looks good.
I would recommend spring loading the adjustable tightener bits, and using only one bearing on one of the pipe lengths. If both pipes are used to fix a linear dimension, the two pipes have to be perfectly aligned, or there will be backlash. If only one is used for the linear plane and the other sets the angular plane, no alignment is needed to produce a zero backlash system. The only effect of non alignment will be a slight angular variation that can be minimized by keeping the pipe pieces as far apart as possible. See this site ttp://
for more data.
Keep up the good work.
Murray Horn.
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