On delivery, the surfaces of the ceramic coupling element and runner are smoothly polished. During the run-in procedure, asymmetry of the alignment is compensated by material abrasion. Over the course of a lifetime, signs of wear as well as effects of asymmetric alignment are visible on the surfaces of the coupling element and the runner.
The outcome of a 19,000 h lifecycle test of a PILine® M-663.5U linear stage test is discussed below, where these impacts can be readily observed. For more details on the test, refer to chapter 4.2. Wear and degree of abrasion on the coupling element and the runner are analyzed in Fig. 4 and Fig. 5, respectively. During the lifecycle test, the average height of the coupling element decreased by about 60 μm, with more than 85 % of the original height (400 μm) remaining. The removed volume amounts to approximately 0.05 mm³ (0.2 mg) of the abraded material.
The mean abrasion depth of the runner was estimated to be approximately 1 μm in the contact area of the coupling element, as described in Fig. 5. From profile scans, an abrasion volume of 0.03 mm³ (0.11 mg) can be estimated.
In total, this particular PILine® linear stage has produced approximately 0.08 mm³ (0.31 mg) abrasion. Therefore, after an initial run-in period, an abrasion volume of less than 0.02 μg/h can be expected, assuming constant wear.