Do plain bearings with large wall thicknesses offer advantages inside heavy-duty applications?

May 7, 2020 Uwe Sund
Metal plain bearings with relatively large wall thicknesses are used in many heavy-duty applications in agricultural technology and construction machinery, e.g. according to DIN 1850. Typical bearings are steel bushings and plain bearings made of non-ferrous metal, such as bronze and brass, or sintered materials. But do plain bearings with large wall thicknesses offer advantages inside heavy-duty applications? I say no. 
 

Why large wall thicknesses are preferred for metal bearings

These bearings are often made from solid material. If special processing is still being carried out on the inside diameter -- to introduce lubrication grooves, for example -- it is obvious that a large wall thickness is required.
 
It is also difficult for me to imagine that, for example, a metal bearing with an inner diameter of 100 mm and an outer diameter of 105 mm (which would correspond to ISO 3547-1) can be pressed into a mounting hole without great effort and without running the risk of the bearing getting damaged or deformed.
 
However, iglide® plain bearings can be installed very comfortably, sometimes out in the field with a hammer and a piece of wood if needed. At the beginning of many projects that involve the exchange of lubricated metal bearings in favor of maintenance-free iglide® plain bearings, I encounter massive concerns. Not only am I encouraging engineers to replace their metal bearings with plastic ones, I’m advising them to use a thinner-walled bearing as opposed to a thicker-walled one. That's two big shockers at one time.
 

iglide® bearings proven to last inside agricultural applications

We have proven that iglide® plain bearings can replace metal ones inside heavy-duty applications. Check out this example to see how our bearings helped an agricultural machinery manufacturer eliminate lubrication for their cultivators, reduce costs and increase reliability.
 

But what does the reduction in wall thickness mean for wear?

In my view, there is only one disadvantage: If the complete wall thickness serves as a wear reserve, then a thick-walled bearing will hold correspondingly longer, provided the wear rate is identical. But honestly, in which application is wear in the millimeter range tolerated? Hardly, for example, in coulters. That would have fatal effects on the sowing pattern.
 
No customer accepts huge stock clearance in their machines! And once a metal bearing is badly worn, things really pick up speed because that will hardly remain without consequences for the wave.
 
To get to the bottom of our iglide® materials, we tested bearings with different wall thicknesses for wear. For this purpose, the materials iglide®  G and iglide®  J were tested on different shafts at 30 MPa.
 

Clear results

The higher the wall thickness, the higher the wear rate.
Chart above: Wear results - iglide J, with 1 mm, 1.5 mm and 3 mm wall thickness
 
Chart above: Wear results iglide G, with 1 mm and 1.5 mm wall thickness
 
The reason for the somewhat higher wear is, among other things, the low thermal conductivity of plastic. In applications with a high pxv value, the material may heat up. The higher the specific pxv value of an application, the more critical.
 
In most of the typical applications in agricultural engineering and construction machinery, the speed is so low that no negative consequences are to be expected. Nobody will try to lift or lower a front loader or wheel loader as quickly as possible with full load over a longer period of time. If you want to learn more about pxv value, visit our webpage
 

Typical hurdle for a practical test - and how to overcome it

Since the mount is designed for a relatively larger outside diameter, the corresponding igus® plain bearing will be too small for the same diameter. An adapter can be used to compensate for the missing wall thickness. It is easiest to rework the original metal plain bearing accordingly, even if it is a little painful to misuse an expensive bronze bearing as an adapter.
 

The Bottom Line

A large wall thickness does not make a plain bearing more wear-resistant! The reduced wall thickness of iglide® bearings offers the following advantages:
  • Reduced cost compared to metal plain bearings
  • Less material used during manufacturing
  • Shorter injection molding cycle times
  • Thinner wall thicknesses allow for tighter tolerances
Visit our iglide® webpage to learn more about the benefits of our engineered composite plastic materials.
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