Gap while assembly Y plates to wasteboard

I am in the final stages of my 1000mm assembly, and I have quite a large gap between the rear Y axis plates and the 20x20 extrusions.


There is a 10mm bolt vs the 8mm bolt in there for reference.

The gap is the same on both Y axis. And to make my life difficult I built my own wasteboard.

Related but not helpful so far: Length along Y axis of slide vs workspace discrepancy
Has anyone else had such a large gap?

Well for now I do think the gap is due to the homemade wasteboard.
I MacGvyer up 2 washers as shims and it seems to work fine.

The tape is an easy way to hold the washers in place during assembly.

It would be more stable if the Y axis plate sits flush against the 29mm extrusion rather than against a washer. Did you measure the length of your 20mm extrusion as mentioned in thread Length along Y axis of slide vs workspace discrepancy ?
It’s probably better that your spoil board is too small rather than too big. Due to a measuring error, mine ended up 2mm too small and it’s had no effect on operation.

I would measure your extrusions because the frame underneath your wasteboard is what effects the mounting of the y plates if i am understanding what you are saying correctly

but you defiantly do not want to have those washers in there those plates need to make full contact so the machine is more rigid

I am confident the extrusions are correct. However there “should be” a 1mm gap between the X 20mm and the perpendicular Y extrusion in your wasteboard; 2mm total. My wasteboard extrusions do not have a gap. The X and Y are flush perpendicual to one another. which is why the length of the wasteboard base is 998mm, not 1000mm. The CAD model shows this gap.

Summary: My MDF is 998mm (matches CAD model). However instead of making the X 20 mm extrusion inset by 9mm, I made them 10mm (different than the CAD model). I thought this would be ok; making everything flush and square.
But as seen it causes the gap I experienced.
On a positive note, this gives me room to mount plates on the Y makerslide down to the Y extrusion for extra support; reducing Y axis flex.

thats crazy I guess i never noticed that seems to me that the gap makes it weaker i am really not understanding what that gap is for