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Plastic Versus Steel Rod End Bearings
1.1 igubal® plastic rod end bearings are self-lubricating and corrosion-resistant.
Spherical rod end bearings are ideal for facilitating rotary and linear motion in a wide variety of applications from packaging and agricultural equipment, to medical and exercise machinery.
However, with different choices available, it is important to remember that not every rod end is the same; each has its own unique set of advantages, disadvantages and limitations.
Below are some of the key elements to keep in mind when choosing between a steel rod end bearing and a plastic rod end bearing.
Design
Click to enlarge image1.2 Steel rod end 3-pc design (left) vs. plastic rod end 2-pc design (right).
Steel rod end bearings and plastic rod end bearings operate differently as a result of how each is designed.
Most steel rod ends feature three pieces: a housing, a “step” (also known as a pivot) bearing, and a ball bearing. A plastic rod end, however, features two pieces: a housing and a ball.
Movement
Click to enlarge image1.3 Steel rod end movement (left) vs. plastic rod end movement (right).
The configuration of the steel rod end bearing causes it to rotate with both the shaft and ball against the housing, and compensate for angular deviations by positioning the ball against the housing. In comparison, the plastic rod end bearing rotates differently – with the shaft against the ball. Like steel rod ends, plastic rod ends also compensate for angular deviations by situating the ball against the housing.
Specifically, igubal® plastic rod ends from igus® are ideal for rotating or linear applications where the rod end’s spherical ball needs to move slightly to compensate for shaft misalignment.
Advantages and disadvantages
Steel rod end bearings and plastic rod end bearings each have many benefits, but also some limitations. It is important to understand these in order to identify the best bearing for your application.
1.4 Plastic rod end bearings are corrosion resistant, unlike their metal counterparts.
Plastic rod end bearings
Advantages:
- Self-lubricating, which eliminates the need for grease fittings and maintenance
- 50 percent lighter than steel / metal rod ends
- Vibration dampening
- Dirt and dust resistant
- Corrosion resistant
- Can be used in rotating, oscillating and linear motions
Disadvantages:
- Lower static capacity
- Larger E10 tolerance with plastic compared to steel at H7
- More heat buildup
- Lower tightening torque than metal parts (from thread)
- Inability to directly fix the ball with a screw (a metal sleeve is required)
Steel rod end bearings
Field Application
1.5 The plastic rod end bearing outperformed the steel rod end bearing.
In a year-long test, an igubal® plastic rod end bearing was still running at 97 million cycles, whereas the steel rod end bearing failed after 50 million cycles.
Test parameters:
Total operation time: 6,500 hours
Cycles completed: 97 million
Inner diameter after the test: pin gauge 6.0 moving / 6.1 not moving
Load 50-90 N
Other Solutions
If neither steel rod ends nor plastic rod ends are a good fit for your application, you might want to consider one of the following alternatives:
- Plain metal rod ends (metal on metal)
- Rod ends with PTFE or nylon lining
- Bronze rod ends
- Needle rod ends
- Ball bearings
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