Connecting and aligning precision rails

[drodrig]

Hi there!

We are installing some precision rails for the movement of one of our systems.

We have chosen the SHS LC45 model from the THK company,

https://tech.thk.com/en/products/index.php?tar=285

We need to separate this in two sections, one of 1 meter and another one of 7 meters. We have two platforms like this:

I would like to ask for help how to install and align these rails.

In order to gain some height and have a good surface I was thinking about putting them on IPN or HEB profiles; since the rail holes is centered this would interfere with the profile web, so an intermediate part can be included (pink part):

One can see a gap between the end of the rail and the end of the profile, this is for the next section of the rail. If the second one goes on the top of the first part of the profile it will fit and be aligned better.

The idea is machining the profiles to get a proper surface for the rails. The screw holes in the rails have some play with the screws, so we can align it horizontally. But in 7 meters this play could not be enough to get them aligned.

Also, how can one adjust the height? There is maximum load of 3-4 metric tons.
Lots of screws to regulate the height?

I will appreciate your help regarding this topic
Thanks!

http://i60.tinypic.com/91htvp.png

 

[Brad805]

You will have better luck getting responses if you post in a mech forum like Solidworks. Structural guys rarely deal with tolerances in the realm of thousandths. Personally, I think you will have problems getting the WF's algined properly. I would try top build a table structure that both rails can be mounted to assuming that top will fit on the deck of whatever CNC machine you are using to bore all of the holes. The vertical alignment issue will be another problem. Have you talked to someone like Bishop Wisecarver, Thomson Linear or THK? Any of them could provide you a complete package.

 

[tbuelna]

Ideally you would finish machine the rail attachment interfaces after the base structure has been welded and stress relieved. If this is not possible, you can shim the rails at installation to level them and use oversized holes in the rails to allow them to be aligned longitudinally/laterally. Just make sure the number of bolts used to clamp the rails to the base is sufficient to accommodate any working loads by clamped friction.

 

[kingnero]

Milling the top of WF beams will warp them to no end.
In the smaller installations I have done in my machine construction job some eyars ago, one rail was installed on the prepared surface, then a rolling charriot was placed on it, with a dial gauge on a magnetic base, in order to measure the distance between both rails. Then the second rail was fastened into place, while driving accross the whole length with the dial gauge, making sure the distance inbetween both rails was kept in the tolerance band.

 

[kingnero]

edit previous post, the dial gauge was also used to check the differential height, but we used properly ground platforms for our installation.
But the dial gauge will certainly come in handy when checking every aspect of the geometry.

 

[drodrig]

Hi there,
Thanks for the answers.
The 7 meter rails will be dismounted after the positioning of our system (the small platform moves away -with our system- in perpendicular direction to the rails).
For the final alignment we will have a laser tracker, so we can find the final position; the problem is how to move them.
And the biggest problem is how to move them vertically, how to shim them.
The shim must be done within one milimeter in a very long part.
kingnero, the chariot idea is very nice. I take note. How did you adjust the rails after knowing the position?
thanks

 

[drodrig]

And yes, we talk to the THK people, but I would like to start getting a general idea how this works