Linear Ball Rail Guides

Frequently asked questions — Rail Guides

• How do I choose between a ball or roller profiled rail guide?

  The choice depends mainly on the rigidity requirements and load capacity of your application. The HG and SR series, using balls, are suitable for standard applications. For heavy spindles or presses requiring maximum rigidity and very high load capacities, roller rails from the HRC and SRG series are recommended. Rollers offer better load distribution than balls, allowing them to support significantly higher loads, particularly beyond the capacities offered by a size 45 rail.
• Which precision class is required for a machine tool?

  According to DIN 645, the precision of the guide is defined by grades ranging from N (normal) to UP (ultra precision). For precision machine tools and servo-controlled axes, it is necessary to choose classes P, SP or UP. These grades guarantee the geometric tolerance essential for the correct operation of high-performance systems. Classes N and H are generally reserved for less demanding applications where strict dimensional precision is less critical to the final result of the industrial process.
• What is the impact of preload on linear guides?

  Preload, classified from None to Heavy, is used to adjust the rigidity of the linear guide. Increasing the preload reduces internal play and increases system rigidity, improving precision under load. However, this increase in rigidity systematically results in higher friction in the carriages, which can affect the service life of the system and the sizing of the motors. It is essential to balance these two factors during selection to ensure the optimum performance of your axis.
• What are the mounting constraints for a profiled rail guide?

  Installing a profiled rail guide requires great care, particularly regarding the flatness of the support surface, which must be a maximum of 50 µm/m to ensure correct operation. To ensure axis stability, it is generally recommended to use two carriages per rail and two rails per axis. Compliance with these mounting conditions is fundamental to avoid abnormal mechanical stresses on the balls or rollers and to guarantee the longevity of the linear guide system.
• What is the recommended lubrication interval?

  Profiled rail guides use a closed circuit of balls or rollers circulating on ground raceways. To maintain performance and service life, grease lubrication must be carried out regularly via the integrated grease nipples. The technical recommendation is to ensure lubrication every 100 km of travel. Strict monitoring of this interval is necessary to prevent premature wear of the hardened steel raceways (HRC 58-62) and to guarantee the continuity of the four-point contact.