Thomson Linear Motion Optmized
Ball Bushing Bearings - Ball Track Differences
Design and Theory
The following describes the the ball track differences in the 3 main product families:
- Precision steel (the original design)
- Super
- Super Smart
Precision steel, Super and Super Smart products all use recirculating
balls. The main design difference is in the load bearing surface. Precision steel uses a hardened sleeve that has a bearing surface ground
into it. Super and Super Smart utilize floating bearing plates. The floating bearing plates
have the ball track(s).
Precision steel, Super and Super Smart products all use recirculating
balls. The main design difference is in the load bearing surface. Precision steel uses a hardened sleeve that has a bearing surface ground
into it. Super and Super Smart utilize floating bearing plates. The floating bearing plates
have the ball track(s).
This image is showing a closeup of the bearing tracks.
- The precision steel linear bearing has point-to-point contact.
- The Super Ball Bushing® design adds floating bearing plates and a ball conforming groove. These improvements increase the load capacity to three times that of the precision design.
- The Super Smart adds two ball conforming grooves to the floating bearing plate. This results in six times the load capacity of the precision design.
Life is a cubic formula and the super bearing's three times the load capacity results in 27 times the life of the precision bearing. The Super Smart bearing's six times the load capacity results in 216 times the life of the precision bearing.
Additional information:
A keen observer might notice that there is point contact between the ball bearing and the shaft in all cases. Then how does adding a ball conforming groove to the ball track in the ball bushing add life? A section of shaft only sees the loaded balls as the linear bearing passes over it. This means each section of shaft is only loaded a portion of the time. But the ball track in the linear bearing sees load anytime the linear bearing has load on it.
In designs where the ball track and shaft both have point contact (Precision steel) the ball track will fatigue before the shaft. Adding the ball conforming groove to the ball track extends the life of the ball track. However, in very short stroke applications that are using a ball bushing with a ball conforming groove (Smart or Super) the shaft could suffer from fatigue before the bearing track. Strokes that may be considered short are strokes that are less that 2 times the length of ball bushing.
This image is showing a closeup of the bearing tracks.
- The precision steel linear bearing has point-to-point contact.
- The Super Ball Bushing® design adds floating bearing plates and a ball conforming groove. These improvements increase the load capacity to three times that of the precision design.
- The Super Smart adds two ball conforming grooves to the floating bearing plate. This results in six times the load capacity of the precision design.
Life is a cubic formula and the super bearing's three times the load capacity results in 27 times the life of the precision bearing. The Super Smart bearing's six times the load capacity results in 216 times the life of the precision bearing.
Additional information:
A keen observer might notice that there is point contact between the ball bearing and the shaft in all cases. Then how does adding a ball conforming groove to the ball track in the ball bushing add life? A section of shaft only sees the loaded balls as the linear bearing passes over it. This means each section of shaft is only loaded a portion of the time. But the ball track in the linear bearing sees load anytime the linear bearing has load on it.
In designs where the ball track and shaft both have point contact (Precision steel) the ball track will fatigue before the shaft. Adding the ball conforming groove to the ball track extends the life of the ball track. However, in very short stroke applications that are using a ball bushing with a ball conforming groove (Smart or Super) the shaft could suffer from fatigue before the bearing track. Strokes that may be considered short are strokes that are less that 2 times the length of ball bushing.
