THK SR type limitations

[NC_jimbo]

Read 5Bears talk about THK bearings and SR spec but I'm still a little confused.

Continued mention that SR is best for "horizontal guideway".

Would that allow me to use it on the Y axis if I had a flat sled design for the head carriage and the 2 rails were in normal flat orientation spanning Y direction?

How about if I had a traditional single box gantry with the rails laying flat on the top and bottom faces of gantry (In this case he top rail would be normal flat mounting and the bottom rail would be inverted and the block hanging upside down)?

I'm thinking that mounting the rails on the face of a single box gantry would be NOT ok.

[RICHARD ZASTROW]

FYI
SR rail flat in normal hor. app. = 100 % dynamic and static capacity
side/lateral = 55% of dyn. and 43% static capacity
upside down/reverse radial= 61% of dyn. and 50% static capacity
pg. 39 THK cat. D-2

[NC_jimbo]

Thanks Richard. I read your comments as saying if I was making a Y-axis sled design things would be OK, but any other common y-axis style would be working in a reduced capability range of the bearing.

Lastly, I looked through the LM docs at THK here
but I can't seem to find the document that you refer. Do you have a link?

[ger21]

Try this one.
http://thk.com/documents/us_pdf/prod...chmodel_c1.pdf

Look at page A-184

[RICHARD ZASTROW]

NC_jimbo, I didn't intend to imply anything, only to provide info. If you size the components properly, you could build it upside down. If you go to the link Gerry provided and check the specs, you may be able to do what you described. Good luck

[Zumba]

Pay attention to moment loads rather than gravitational loads. All else equal, moment loads are the same in all rail/block orientations. Right side up, sideways, inverted, doesn't matter. Rail LOCATION, on the otherhand, does make a difference. Rail/block orientation affects location, so use your discretion.

For example, if an inverted rail/block assembly allows you to shorten a lever arm (and reduce the moment force) by 300%, it will more than offset the decrease in load capacity.