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PLASTIC WRAPPED BEARINGS-Plastic-Coated Bearings

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Plastic-Coated Bearings

 

 

In the fields of machinery and industrial design, a small innovation can often lead to a leap in efficiency, and plastic-coated bearings are one such example.
In modern machinery and equipment, plastic-coated bearings, with their unique structure and performance, have become an indispensable component in numerous industrial applications. While traditional metal bearings are durable, they have limitations in corrosion resistance, vibration and noise reduction, and workpiece surface protection.
The emergence of plastic-coated bearings cleverly addresses these issues. By coating the outer ring with a layer of engineering plastic, they combine the strength of metal with the various excellent properties of plastic, creating a more comprehensive bearing solution.

 

What are plastic-coated bearings

 

 

As the name suggests, plastic-coated bearings are specialized bearings with a layer of plastic coating on the outer surface. This design goes beyond a simple physical coating; instead, a specialized process securely bonds the plastic to the bearing base, creating a composite product that combines the advantages of both.

 

 
Diverse Materials and Properties
 

The performance of plastic-coated bearings depends largely on the plastic material used. Different materials impart distinct properties, making the bearings suitable for diverse operating environments.

Common plastic-coated materials include nylon (PA), polyoxymethylene (POM), and the engineering plastic polypropylene (PP).

These materials generally possess a certain degree of hardness, impact resistance, friction resistance, and self-lubricating properties.

Nylon (PA)

Nylon (PA) offers excellent mechanical strength and wear resistance, making it suitable for the production of relatively precise plastic bearings. It also has a wide operating temperature range, typically between -60°C and 100°C.

Its surface is strong and smooth, virtually free of tension. Its excellent self-lubricating properties and low coefficient of friction allow it to be used in precision and high-speed applications while maintaining the traditional advantages of plastic bearings.

Polyoxymethylene (POM)

Polyoxymethylene (POM) is the most widely used plastic bearing. It features high rigidity and hardness, maintaining high impact strength even at low temperatures.

POM also exhibits excellent elasticity and creep resistance, as well as high thermal stability and very good dimensional stability.

Polyurethane

Polyurethane is another common overmolding material, often used in PU-coated bearings. The polyurethane portion is made of thermoplastic material, offering excellent wear resistance and greater cost-effectiveness.

Polyurethane hardness can be adjusted as needed, for example, with a Shore A hardness of A90. However, it should be noted that polyurethane degrades due to hydrolysis when used in high humidity or water.

Specialized engineering plastics

Specialized engineering plastics, such as Saint-Gobain's NORGLIDE® MP bearing material, consist of a metal mesh embedded in a wear-resistant PTFE polymer and then sintered.

This combination offers high load capacity and excellent formability, making it suitable for many applications, including harsh chemical environments.

Wide Range of Applications


Plastic-coated bearings have an extremely wide range of applications, covering nearly every industry requiring bearings.
Plastic-coated bearings are widely used in machinery, industrial assembly lines, furniture, and hardware accessories.
Depending on the application, plastic-coated bearings can be manufactured in various shapes, including pulleys with V-grooves.

 

 In the industrial sector, plastic-coated bearings are often used in industrial assembly lines as guide pulleys and support wheels in conveyor systems.

For example, in the crimping mechanism of winding machines, the wear resistance of polyurethane can extend service life. Polyurethane offers a wide range of hardness options, allowing for selection based on the required pressing force.
For workpiece transport assistance, the polyurethane coating on the bearings protects the workpiece from damage.

 

 In the automotive industry, Schaeffler's VoltShield-P plastic-coated insulating bearings, which utilize a high-performance plastic coating, address the issue of electrical corrosion in motor bearings for new energy vehicles. They are already in mass production at Schaeffler's Yinchuan plant and are used in several leading domestic brands.

This bearing offers a high cost-effectiveness, saving costs and improving reliability and safety.

 

 Plastic-coated bearings also demonstrate unique value in specialized environments. For example, in gluing applications, when the adhesive contains chemicals, plastic-coated bearings made of specialized materials may be used.

In environments with high humidity, hydrolysis-resistant materials should be selected or certain polyurethane materials should be avoided.

 

 For high-end equipment, NORGLIDE® MP bearings are suitable for many applications, including those in harsh chemical environments.

This material offers excellent sizing properties, enabling interference fit designs between bearings and shafts to generate specific torques or eliminate backlash.

 

Advantages of Plastic-Coated Bearings

 

1. Workpiece Protection

Plastic-coated bearings effectively prevent scratches and damage to delicate workpieces. When transporting fragile and easily scratched workpieces, the outer plastic layer provides cushioning and protection.

2. Corrosion Resistance

The plastic layer provides excellent corrosion resistance, enabling the bearing to operate properly even in humid or corrosive environments.

3. Vibration and Noise Reduction

The plastic layer absorbs shock and reduces noise, ensuring smoother and quieter operation of mechanical equipment.

4. Self-lubricating

Many plastic-coated materials are self-lubricating, reducing the need for lubrication and maintenance.

5. Insulating Properties

Plastic-coated bearings can be used in applications requiring electrical insulation. For example, Schaeffler's plastic-coated insulated bearings were developed specifically to address the electrical corrosion issues associated with motor bearings in new energy vehicles.

 

Selection and Usage Key Points


Choosing the right plastic-coated bearing requires comprehensive consideration of several factors:
------Operating Environment: This includes factors such as temperature, humidity, and the presence of chemical corrosion. For example, polyurethane bearings used in high-humidity environments or water can hydrolyze and degrade.
-------Load Requirements: Plastic-coated bearings made of different materials have different load capacities. For example, polyurethane-coated bearings have a specific allowable load range.
-------Precision Requirements: For precision machinery, higher-precision bearings are required.
-------Special Requirements: This includes requirements such as insulation, acid and alkali resistance, or food contact.
-------Mounting Method: Plastic-coated bearings have a variety of mounting methods, such as external threads and flanges, and the selection should be based on specific installation conditions.

 

During use, please note the following:
Polyurethane may yellow over time, a phenomenon known as yellowing, but this does not affect its physical properties.
The dimensions of polyurethane bearings will change with ambient temperature, but the change is minor, and they will return to their original dimensions after being stored at room temperature for a few hours.
Avoid using polyurethane bearings in a wet or humid environment for extended periods of time, as this may cause hydrolysis and deterioration.

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