Inaccurate installation techniques during synchronous belt operation can readily cause early damage or failure of the synchronous belt, therefore influencing not only the proper running of the equipment but also the running expenses.
1. Timing Belt Installation Errors
(1) Inner Ring Misalignment
Loose fit between the shaft and the inner bore of the synchronous belt: When the fit between the shaft and the inner bore of the synchronous belt is too loose, sliding occurs between the two. This sliding friction generates heat, causing the synchronous belt to overheat and fail. Additionally, the sliding leaves noticeable marks on the surfaces of the shaft and inner bore.
Cracks brought on by heat from contact between the inner ring end face and shaft shoulder: Sliding friction generates high temperatures during "inner ring running," and the narrow contact area between the inner ring end face and shaft shoulder can cause temperature increases to be rather significant. This results in thermal cracks on the inner ring end face that can spread and finally cause the inner ring to shatter under usage.
High temperatures cause the metal of the shaft and inner bore surface to melt and cling together, greatly influencing the normal operation of the synchronous belt by means of sliding friction generated by "inner ring movement."
(2) Outer ring movement
Sliding between their surfaces results in heat production problems and synchronous belt failure from overheating if the housing bore diameter and synchronous belt outer diameter have too loose a fit.
(3) Directly striking the synchronous belt with a hammer
Direct hammer strikes of the end face of the inner ring (or outer ring) might readily compromise the flange when installing a synchronous belt with an interference fit on the inner ring. To finish the installation, first lay a sleeve on the end face of the inner ring-or outer ring-then hammer on the sleeve.
(4) Transmitting installation force through rolling elements
When installing a synchronous belt with an interference fit inner ring, force should not be transmitted to the inner ring through the outer ring and rolling elements. Otherwise, this may damage the synchronous belt raceway and rolling element surfaces, causing noise during operation and premature failure. The correct installation method is to apply force directly to the end face of the inner ring using a socket.
(5) Excessively high heating temperature
Some users use an acetylene torch to heat the inner bore of the synchronous belt. However, if the heating temperature exceeds 727°C (the phase transformation temperature of the synchronous belt steel), the internal microstructure of the synchronous belt steel will change. After cooling, the inner bore dimensions cannot return to their original size and are typically larger than before heating.
(6) Improper installation causing one-sided force on the synchronous belt
If the spherical roller synchronous belt is not installed properly, one row of rollers will be stressed while the other row of rollers will not be stressed. In this case, the raceway on one side of the inner and outer rings of the synchronous belt and one row of rollers will be subjected to excessive pressure, thus accelerating damage.
2. Correct installation method
(1) Selecting appropriate clearance
When installing the synchronous belt, ensure that the fit between the shaft and the inner bore of the synchronous belt, as well as between the housing bore and the outer diameter of the synchronous belt, is appropriately tight to avoid "inner ring drift" or "outer ring drift."
(2) Use appropriate tools
When installing a synchronous belt with an interference fit, use tools such as sockets to transmit installation force, avoiding direct impact on the synchronous belt to prevent damage to the flanges or raceways.
(3) Control heating temperature
If heating is required for installation, strictly control the heating temperature and never exceed the phase transformation temperature of the synchronous belt steel to prevent changes in its internal microstructure, which could affect the belt's performance.
(4) Ensure proper installation
For synchronous belts requiring precise installation, such as self-aligning roller belts, ensure proper installation to distribute roller loads evenly and prevent damage caused by uneven loading.
While synchronous belt installation may seem straightforward, it involves numerous critical details that require careful attention. Only by mastering scientifically sound and proper installation methods can synchronous belts be used reliably and their service life extended.