Installation of INA linear ball bearing 2

[Smile9999]

I am currently designing the shaft supports of a tray thats sliding on 2 shaft guides using 4 INA linear bearings( 2 on each side) ,

the two guides are supported by two plates , one plate is fixed to the machine frame and the other is at the end of the two shafts, now each plate ofcourse has two holes , the distance between the two holes is the same but I want to add geometrical tolerance to ensure the parallelism of the two holes in each plate and between the two plates , the proplem is I dont know what parallelism between the two guides is optimum for the linear bearings as its not mentioned in the catalogue or in their website, also it says that the bearing can withstand static misalignment of up to 30' so does that mean that it doesnt need accurate parallelism even in a 4 bearings arrangement

please someone explain this to me, the bearings in question is KB20-PP
here is its link in the website

http://medias.ina.de/medias/en!hp.ec.br.pr/KB..-PP*KB20-PP;bh9H7vtTRjw8

thanks for any information

 

[Smile9999]

guys please, I need an answer to this question

my proplem lies with the fact that I dont know whether INA linear bearings need accurate parallelism tolerancing or do they compensate this, thanks

 

[MikeHalloran]

I don't think the bearings compensate for anything.
I've seen them used on machine tools, where the supports were aligned to a gnat's eyebrow by precision machining before the guide rods were mounted.

Less expensive assemblies typically use asymmetrical elasticity in the supports to allow for misalignment. E.g., one rail is supported in blocks, the other is supported by structures having webs that are somewhat flexible in the direction normal to both rails and parallel to their common plane.

Still less expensive assemblies use only three linear bearings, which allows for some twist in the trajectory.

This should all be covered in the INA catalog. ... at least in the thick one.



Mike Halloran
Pembroke Pines, FL, USA

 

[asimpson]

I think the 30' is between bearing and rail. Problems of lack of parallelism between rails would be a function of length of travel distance. I would look at linear deviation of parallelism over travel and see what bearings can take.

Typical arrangements of cylindrical bearing rails mounted on ends have mounts bored together as a set and bearing fitted to rails before fixing to carriage.

 

[Jboggs]

Having done this myself many times I can tell you that in my opinion, you are wasting your time designing your system based on guidance you receive from an online forum, no matter how competent and accurate it is, or how well-intenioned. You mentioned that the information you need isn't on INA's website or catalog. Call Customer Support, or Applications Support. Talk to a live person who knows the product and has a personal interest in making sure it works. On many occasions I have submitted a drawing of what I wanted to do for review and comment by the manufacturer of the product I wanted to use. My experience is that they appreciate being given the opportunity to make sure their product succeeds, and will give you valuable feedback. Do it. Talk to the people for whom it is personal.

 

[Smile9999]

thanks for all the responses guys , I will contact them directly and ask them, appreciate all the answers