Your thoughts on 1500mm X axis gantry design

[disneytoy2]

Hello!

So John and the rest, I'm at the stage on this large scale 2 Meter tall clay printer, to order the parts for the X axis. It is based on a 1500mm long Triangular aluminum truss. 8".

See attached diagram.

So the payload is not going to be very heavy, perhaps 20-25lb. Actually it may be half that. It will be belt driven.

So here are some of my thoughts and I'd like opinions.

Orientation of the Triangle. Since gravity is pulling down, Initially I though of having the triangle pointing down like an arrow head. I can run 2 linear rails on the top, and the actual nozzle will be off the side.

I discounted orienting the triangle facing up. The bearings would be hanging off the bottom, and its my understanding there is less ball bearing contact that way. In the same orientation, the rails can go on the sides, but still not the best for the bearings.

Option 3, The Triangle is pointing left or right, leaving the 2 tubes to be vertical. The linear rail can be facing sideways.

Option 3.5: Same orientation, but the lower linear rail facing outward, and the upper one on the top tube facing up.

I'm trying to keep the x axis light. The truss is only 9lb. say another 1b or 2 for the belt and pulleys. So, my main weight is the linear rail.

I have a 20mm 1200mm supported linear rail here and it is way too heavy, didn't weight it. I was thinking of 16mm or even 12mm.

Again as I mentioned in my previous posts, The print head or nozzle is connected to a tube. So I have to have it hanging off the side and not centered underneath the x axis.

Just trying to get this figured out. Please see my diagram.

Thanks again!

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[Jim Dawson]

I like option 3.5. Looks pretty substantial with both carriages in at least partial compression.

[skrubol]

I agree, that orientation is a pain with profile rail, but with round rail alignment shouldn't be too difficult.
How do you plan on attaching the rail to the truss?

[disneytoy2]

Hello!

Originally I was going to use those Supported Linear rails maybe 12mm or 16mm. But if you think 1500mm unsupported is rigid enough (x2) then I can just have a end plate at both ends to position the rods. I'd really like to keep weight in check. Thanks. I also saw some 16mm with a 10mm hole, so lighter. Any thoughts.

[skrubol]

No, 1.5m of 16mm unsupported rail would be pretty flimsy. If you go up a couple sizes it may be an option.
I was referring to profile rail (the squareish type rails,) being a pain when on different axes, but supported round rail is more forgiving. I would think attaching to the truss would be a pain though.

[Jim Dawson]

The rails would be easier to mount if you used square tubing for the truss rather than round.