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Design issue with Smartrapcore ALU (200x200) version

Posted by PDBeal 
Design issue with Smartrapcore ALU (200x200) version
November 19, 2018 11:46AM
So I really dislike the new Onshape requirements to make everything Public, so I’ve been slowly recreating the Onshape files in Solidworks one by one. I know I could just export and reimport, but I want all the sketches to be editable so I’m redrawing everything.

In this process I realized the parts for the Smartrapcore ALU Ztop and Zbottom are not in alignment for the 8mm rod. Between the top and the bottom, they’re out of alignment of 2mm. There is an alignment issue with the belt and the pulley and the GT20 drive wheel too. I then went back and checked the onshape file and it has the same 2mm alignment issue. I’m beginning to wonder if that’s what causes some Z banding that I’ve noticed and could never solve. And I suspect the bed leveling has somewhat adjusted for this alignment issue in the Z axis.

So I’ve redesigned the Ztop and Zbottom parts, printed them last night and plan to reinstall them and see if things change. I won’t be distributing these changes as I’ve also spread the Z rods apart to the maximum width of the print bed for stability and also added an additional tab to mount on the 2020 structure to inhibit flexing over the increased distance. All of these mean I run a heavily modified Zaxis (still cantilever in design, but adjusted for stability and makes three parts that have to be printed diagonally across the bed one at a time.

But I do think anyone that’s using the stock Smartrapcore ALU files might want to look into the 2mm alignment issue with the Ztop and Zbottom parts.
Re: Design issue with Smartrapcore ALU (200x200) version
November 22, 2018 01:47PM
Attached are the updated STL files for my changes. This is what I've modified my Z axis to look like and it runs really well using the rest of the stock parts. You will have to print one more bearing sleeve from the original Smartrapcore ALU version. These three files give me better support to the bed, less twist than the original, better support under the piece of wood and have removed all the Z banding I noticed in my parts. When you install these pieces, you do need to make sure they are aligned vertically.

open | download - Ztop_belt4_8mm_rod_200mm_bed.STL (95.7 KB)
open | download - Zbottom_belt3_8mm_rod_200mm_bed.STL (109.1 KB)
open | download - Zslide_belt2_8mm_rod_200mm_bed.STL (395.4 KB)
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