Bearing positioning on the Y Axis
The build instructions are very specific and insist that the linear bearings be placed so that a row of balls is straight up and down. This causes the load, which appears to be primarily vertical, to be applied to a single row of balls.
This seemed odd to me so I did a little googling. I found the following document that discusses this in terms of maximum capacity.
http://medias.schaeffler.de/medias/en!hp.tg.cat/tg_wf*ST4_307653387
Looking at figure 2, you can see that the maximum load carrying capacity is when the load is evenly distributed across more than one row of balls, not just one. This makes sense to me.
I'm wondering why the Prusa designers want the load on just one set of balls. Being on my second set of bearings and shafts due to excessive scoring, I'm wondering if maybe this is just plain wrong.
My new shafts are already, after about a week, showing mild grooving and wear on the top where the single row of balls rides. The wear is even across the two shafts as opposed to my original problem which affected primarily one shaft and may have been the result of defective components.
Why does Prusa want the bearing alignment like this? Has anyone tried aligning them 45 degrees from the Prusa recommendation so that the vertical load would be more evenly distributed?