While the mode of transport of sixty-ton statues in ancient Egypt remains up to discussion [1], the movement of workpieces of similar tonnage in modern times is possible thanks to linear guides. Linear guides, also known as linear bearings, are mechanical elements that facilitate frictionless translational motion. They find extensive use in food, automotive, paper, wood, and metal-cutting industries as part of key machines.
Linear guides appear in various forms and sizes. Our focus will be on the ball-rail linear guide systems as their versatility comes in handy in loads of industrial applications. Using Bosch Rexroth linear guide designation system, we will learn to identify and select the right linear guide for our application.
Linear guides are distinguished by design styles, sizes, preloading, and tolerances. By knowing the respective code of each characteristic, we can identify any linear guide.
Linear guides of Bosch Rexroth come in various design styles, with respective heights, lengths, and widths. For indicating the design style of linear guide, Bosch Rexroth has opted for a three-letter format [2], as shown in the figure below.
Criterion Designation Abbreviation
Width Flange F
Slimline S
Wide B
Compact C
Length Normal N
Long L
Short K
Height Standard Height S
High H
Low N
There are reference sizes that govern the individual dimensions of guide and rail in ball rail systems. In standard rail systems, they indicate the nominal size for the guide rail base’s width and provides other dimensions according to DIN 645-1 [3]. For wider rail systems, on the other hand, the nominal width of the guide rail is separate and follows the reference size by a slash or “/”.
Rail Type | Example | A2 (mm) |
---|---|---|
Standard Rail | 15 | 15 |
Wide Rail | 25/70 | 69 |
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Ball runner blocks or linear guides can be preloaded to increase linear guides’ overall rigidity for specific applications. Depending upon the preloading, the linear guides are available in four classes – C0, C1, C2, and C3. C0 class has no preloading and is suitable for smooth-running guide systems with minimum external forces. On the other end of the spectrum, the C3 class has the highest preloading and finds use in precision machine tools and forming machines.
Class | Preload |
---|---|
C0 | Without preload |
C1 | 0.02 C (C = Load capacity) |
C2 | 0.08 C |
C3 | 0.13 C |
Ball rail systems are categorized into six different accuracy classes based on acceptable tolerances in height, width, and parallelism. These accuracy classes make an individual linear guide suitable for a specific application. For example, an ultraprecision linear guide complements the precision cutting applications. Â
Some accessories and add-ons allow ball-rail systems to adapt to respective applications and are, often, part of a linear guide description. Standard seals or low-friction seals help protect against the dirt, whereas the corrosion-resistant products allow operation in harsher conditions. Meanwhile, the ball chain sees action in low noise applications.
While there are plenty of variables to consider while selecting your linear guide, there are a few which deserve more attention than others. Let us focus on them.
We are hoping that after reading this you will be well-equipped to understand the manufacturersâ designations and make an informed choice for yourself. Still, if you need any help you can reach out to us. We have well-qualified application engineers who will be glad to assist you.
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