Pfeiffer Vacuum

3.7.1.1 Translation sealed by diaphragm bellows

Membrane bellows are made from individual lamellas welded together. With a small spring rate, the axial expansion is highly flexible. Bellows ensure a hermetically sealed metal enclosure and are suitable for the highest UHV requirements.

The selection and design of the bellows is in accordance with the required movement task, taking into account the operating conditions: Service life (number of movement cycles), operating temperature, bakeout temperature, differential pressures. The lifetime can be up to 0.5 million cycles with membranes made from the material 316L and up to 10 million movement cycles for the more elastic but magnetizable material 350AM.

Membrane bellows within the specified number of cycles are maintenance free. After they reach the calculated motion cycles they need to be replaced. They are not suitable for environments with dust and dirt.

Membrane bellows are used in the Z-axis, XY-axis and XYZ-axis precision manipulators, and port aligners and bellows sealed rotary feedthroughs.

When baking out units with diaphragm bellows, it is important to ensure an even heating. Heater bands on diaphragm bellows should be avoided. They lead to a strong local heating, as the diaphragm bellows have a low mass and a small area for the heat conduction. Temperature controlled heating sleeves are the better, though more elaborate alternative.

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