Bushes and Bearings

What is a Plastic Bush or Bearing?

A bush or bearing is also known as a Plain Bearing, i.e. they don’t have rolling elements like a ball bearing. The primary function is to support movement by being an interface between rotating or sliding parts. This crucial component is designed to reduce friction between moving parts and act as a sacrificial wear component.

Benefits of Plastic Bushes & Bearings vs Other Bearings

Eliminating Lubricants – unlike rolling element bearing and bronze bushes, often plastic bushes and bearing can run dry, especially when self-lubricating materials such as Ertalon LFX and Ertalyte TX are utilized.
Dirty & dusty conditions – where traditional bearings suffer, plastics with high abrasion resistance such as Polystone 7000 and Ertalon LFX can provide maintenance free operation.
Low Friction – metal-on-metal sliding in the case of bronze results in higher friction than plastic-on-metal, requiring higher energy and wear rates, opposed to the low friction of plastics, such as Nylatron NSM, Nylatron 703XL, Ertalyte TX and Ticomp S.
Reduced wear – traditional plain bushes such as bronze result in higher shaft wear and therefore reduced service life of both the bush and the shaft (or counter-face).

Dotmar has qualified engineers that can provide direct support with plastic bush and bearing designs, including conducting calculations and reports.

MATERIAL SELECTION CONSIDERATIONS

Material selection is a critical consideration when choosing a plastic bogie wear part, as it directly impacts the performance, durability, and maintenance requirements of these components. Here are some key material selection considerations for plastic bogie wear parts:

Load and Speed

Neither load and speed can be considered without the other, as the load capacity of a material diminishes with increasing speed, and the speed capacity diminishes with increasing loads. This is known as the PV (Pressure-Velocity) value.

Time

The duration of operation is critical and will significantly affect the load and speed capability of materials for bushes and bearings.

Temperature

The surrounding temperature (opposed to heat generated from friction) for both short- and long-term exposure is important, as materials can withstand higher temperatures for short term periods compared to long term or constant exposure, which in turn affect their load carrying capacity. In the case of extreme temperatures, materials such as Ketron HPV PEEK, Techtron HPV PPS and Ticomp S.

Wear and Abrasion

Abrasive conditions provide different challenges to clean environments, and therefore the material selection, which can include Ertalon LFX and Polystone 7000.

Lubrication

Consider whether the application allows for regular lubrication or requires dry-running, and if self-lubricating materials, such as Nylatron NSM, Ertalon LFX or Ertalyte TX are needed.

Friction

The co-efficient of friction of materials will vary depending on the conditions (load, speed, counter-face etc), and will influence the forces required to drive the system, as well as the heat generated. Common materials with low friction include Nylatron 703XL, Ertalyte TX & Ticomp S.

Regulatory Requirements

Does the application have regulatory requirements such as food contact, drinking water, anti-static or flame retardant. The food industry may also require materials to be metal detectable, x-ray detectable and/or visually detectable by being coloured blue.

Other considerations

At times there may be other considerations such as chemical resistance, dimensional stability, machinability, insulation (thermal and electrical) and impact. Some high performing materials can carry and higher cost, therefore balancing the cost vs performance benefits should also be considered.

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