The most critical components of a machine tool spindle are its bearings. Bearings support the shaft and provide accurate. smooth rotation. Foreign particles and fluids damage bearings, and ultimately shorten spindle life.
Seals placed between the shaft and stationary parts protect the spindle bearings. There are many seal designs, but none are perfect for every application. The main challenge is interfacing with a shaft that can spin, while still providing a good seal. Other factors, such as size constraints, temperature, humidity, environmental air pressure fluctuations, chemical exposure, and particle geometry, influence seal selection.
Historically, machine tool spindles employ rubbing-type lip seals for slower applications, and labyrinth-type gap seals for high-speed applications. In instances where environments are extreme, air purge is added to the labyrinth seals to continuously purge contaminants from the sealing area. In the mid1990s, safety concerns prompted machine tool builders to more completely shroud the working area of machine tools. This change, in conjunction with dramatically increased coolant flow rates and pressures, creates a situation where traditional seals are inadequate. Bearing contamination occurs within a relatively short time.
In 1996, Setco constructed a test apparatus that would enable the replication of in-service seal failures. A further objective was to build a foundation on which seal performance could be assessed. Among the features were:
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