I feel too many parts need to be aligned to make X and Y move smoothly. This complicates assembly as well as the end result.
I’d like to suggest that the plastic 4 parts housing the bearings for each axis, could be made into one piece, reducing alignment issues.
Taking this one step further, would be to make the entitre bed [X and Y respectively] in one piece [two in total]. If need be the aluminium frame coud be bolted on for stiffness.
Result: The rods would fit more precisely and slide better because the bed, housing for the bearings and the seating of the motors would be in a precise and fixed position.
Not sure that would help…I guess no frame we each build is exactly the same and independent bearing mounts give an additional flexibility to help with ultimate alignment. In my case I did not tighten the hex screws (having first checked the rods were not bent) until I was sure they ran OK. I was bit put off by the “scratchy” feel but this is apparently OK - as dealt with in other posts.
I agree with Tonyin3D. If your thorough when building your printer you shouldn’t have any problem with the X-Y axis.
A rigid mount wouldn’t leave any mean to handle the inevitable manufacturing tolerances of the hardware.