The Miba process for manufacturing bearings - half shells and bushings

The production of bearings in the form of half shells and bushings at Miba is based on precise manufacturing steps and state-of-the-art technology. From casting the base materials to special coating processes, every detail is designed to optimize the functionality and durability of the bearings.

In order to meet the diverse requirements of customer systems, Miba relies on a multi-layered bearing structure. The individual layers and their interaction ensure that the bearings deliver high performance, which sets them apart from conventional bearings.

Basically, a Miba half shell or bushing consists of a steel backing and the tribologically effective bearing metal. Depending on the requirements, an additional top layer can be applied by coating when manufacturing the bearings:

Steel backing: This is the load-bearing layer of the bearing and provides structural strength and stability. The steel backing ensures that the bearing can withstand mechanical loads.

Bearing metal: The overlying layer is a bearing metal with good frictional properties and high wear resistance. This layer enables low-friction movement. For special applications, it can also be useful to apply several layers of bearing metal in order to combine different properties of the bearing metals.

Possibly additional coating: In some applications, an additional coating may be useful to provide special properties such as improved corrosion resistance or improved running-in behavior.

For certain applications, bearing metals can also be applied specifically to the corresponding component (e.g. inner diameter of a gear wheel) using PVD technology or direct coating. This is particularly advantageous where additional weight savings are required or complex geometries are to be manufactured.

1. Material selection

The first step in the production of hydrodynamic bearings begins with the selection of the right bearing metal. Depending on the application and specific requirements, we use different metal alloys that are known for their resistance to friction and wear.

The most commonly used materials in the manufacture of bearings include:

• Aluminum
• bronze
• and white metal

We also develop innovative alloys ourselves in order to respond quickly and specifically to our customers' requirements.
 

2. Casting and molding

We use advanced casting techniques to produce the optimum raw materials and blanks for our products - all in-house. Our processes include:

Strip casting: a continuous casting process in which the bearing metal is applied to the steel. In a subsequent process, the primary material is prepared in the form of coils or strips for the next processing steps.
Spin casting: In this process, the bearing metal is cast in rotating molds (steel bushes), which is particularly suitable for cylindrical components such as bushes.
 

3. Forming

The coils or strips are formed into the desired shape (half-shell or bush) through targeted forming.

4. Mechanical processing

High-precision CNC machining produces the final shape according to the drawing. Precision comes first - we pay attention to the highest accuracy to ensure an optimal fit and functionality of the bearings.

5. Coating process

Depending on the specific application and requirements, the bearings can be provided with special coatings during production. These coatings can further increase the friction properties, wear resistance and durability of the bearings. Miba uses a wide variety of coating processes for this purpose:

• Galvanic coatings: Various metal coatings, such as tin plating
• Polymer coating: Provides additional protection and sliding properties

Depending on the requirements, these manufacturing steps are decisive for the final performance of the bearings.
 

6. Quality control

Quality is Miba's top priority. Depending on customer requirements, the manufactured bearings in the form of half shells and bushings can undergo 

• random sample tests during production 
• up to 100 % inspections. 

The bearings are checked for dimensional accuracy, surface quality and mechanical properties using state-of-the-art testing methods and technologies. Only bearings that meet our high standards are delivered to our customers.

7. Shipping

After the bearings and bushings have gone through all the production and testing processes, they are carefully packed and shipped to our customers. Depending on customer requirements, special packaging can be used.

Wind turbines

A milestone was reached in 2019 when bearings were successfully validated in turbine tests. Since then, they have been used in the main gearboxes of wind turbines, especially in planetary stages of higher power classes from 3 MW. 

Hydrodynamic bearing technology, in which the tribologically effective bearing metal is located on the outer surface of the bushing, minimizes the installation space. This enables smaller planetary stages and reduces the overall weight.

This technology makes it possible to increase the input torque and achieve power classes of up to 20 MW, thereby reducing energy generation costs. 
 

Aerospace

Applying the bearing metal to the inner diameter of gears by PVD coating during the manufacture of the bearings enables the implementation of turbines that have a fuel reduction of 20% and a significant reduction in noise.

Expressed in figures, they cause up to two thirds less ground noise. This means that aircraft can land at airports for longer in the evening, as the reduced noise development leads to a noticeable reduction in noise levels. 

Emissions are also reduced - CO2 by 15 % and NOx by 50 %.

Large engines

Modern large engines, especially those with frequent start-stop changes, benefit from bearings that are optimally adapted to changing operating conditions. Miba relies on innovative polymer coatings during production. They ensure that the bearings function reliably when starting and stopping in the mixed friction phase.

In addition, Miba's bearing design ensures stability and load-bearing capacity as well as low-friction movement.