As the German manufacturers explain what they see as a key principle, in the case of standard linear guides, the block is loaded differently by the different quantity of load-bearing balls entering and leaving the load zone, so that the latter is displaced differently and a high waviness results. The SPR/SPS models, however, are said to reduce this effect to approximately 1/10 thanks to their specific design with eight race grooves, a smaller ball diameter, and longer blocks. Consequently, it is claimed, they exhibit a similar waving to that shown by hydrostatic guides. Measured on a 300 mm stroke length, for example, the SPS25LR LM guide has a maximum waving of only 9.5 nm in the vertical direction and 21 nm in the horizontal. In addition, the two LM guides SPR/SPS are distinguished by a rigidity that is reportedly higher than that of roller guides of comparable size. This makes them ideal for the further optimization of high-precision machine tools. The series on show is available in the standard sizes 15 to 45. The SPR variant is for predominantly high radial loads and the SPS type has an evenly high load rating in all main directions.
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High-end profiled rail guides with maximum precision
With the two series SPR/SPS, THK is offering linear motion guides with ball cages that feature particularly high rigidity and low waviness.
06 Sep. 2017
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