Changes on the Bed Support (3D Printer Part 19)

boucaron(57)

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Hi ! As said in the previous post, I am changing a lot of things on the Bed Supports due to bending issues.

Before I just put 2 2040 profiles and link them with two 2020. It was not a good idea due to PETG parts flexing a bit and generating a wobble.
So I add 2 2020 and 4 biffy aluminium brackets (probably next time, I will look for steel ones) for the bed support.
First rigidity issue solved.

The next issue was in the design of my brass supports that was generating potentially bending constraints on the 8mm rods.

Even on a relatively short distance 8mm are very easy to bend.
I already had some experience on the XY gantry to align the 6 rods 600mm.
The idea is to allow some clearance on the parts to be able to align and avoid any bending due to the lack of precision of the whole assembly.

Instead of using the brass bushing, I am using 4 very long LM8 that are more kind if I have a bend in a rod. I changed the attachment points on the Bed Support to allow to move on the XY plane on both translation and on the rotation.

First prototype batch

Second batch to check clearance and if enough alignment. It was a bit too tight, the final version is the same design with minor modifications.

The pre-assembly is a bit tricky but not difficult, tricky on the order to align and to lock things:

Align and lock the bottom rod supports and keep the top free.
Align and nearly lock the leadscrew nut supports.
Move up and down the bed to align the top.
Align and nearly lock the bed supports (the whole bed support to the chassis has a side clearance of less than 5mm side to side).
Move up and Lock the top supports .
Check and realign leadscrews.
Lock leadscrews nut supports
Recheck for any unwanted move.

Pre-assembly

I put only one screw to hold it to check for the needed clearances on the final part, those small guys do not flex.

Result and forth coming part

I do not have any binding, not any bad wobble, but there is still a very minor wobble.
I used the modified Z Nut holders allowing adjustment on the XY plane (translation/rotation) which are working correctly to avoid the bending of the leadscrew but they are too weak and they are flexing a bit.

So I am fixing this issue right now, I redesign it and printing with the Strong Hex Infill at 30%.
The lines on the Strong Hex infill are 0.8mm for the thinnest and 1.6mm for the large ones.