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3M™ Friction Shims for Transmission & Connection Technology

To transmit high torques and shear forces via single bolt connections, 3M™ Friction Shims offer a simple, reliable and compact alternative to conventional solutions involving large-size bolt or multiple bolt joints or expensive and complicated interlocking connections.

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Applications

The superior properties of 3M™ friction-enhancing shims have a proven track record in Automotive Applications, Wind Energy Applications, in bolt joints in mechanical engineering and industrial applications, such as: Single bolt joints on the crankshaft and cam shaft Vibration-resistant, durable flange connections Improving the performance of components and assemblies without changing the basic design Simple and reliable housing fastenings For these and many others applications, 3M™ offers simple, reliable solutions tailored to customer requirements. They enable favorable designs with high power density by using 3M™ Electroless Nickel coating.

Structure of 3M™ Friction Shims
Structure of 3M™ Friction Shims
3M™ Friction Shims in various designs
3M™ Friction Shims in various designs
An exemplary application of 3M™ Friction Shims
An exemplary application of 3M™ Friction Shims

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3M™ Friction Shims

3M™ Friction Shims create possibilities for lightweight compact design while increasing potential load and peak torque in bolt connections.

Features

  • Increases the coefficient of static friction
  • Function of 3M™ Friction Shims is not affected by an oil film
  • Can be easily retrofitted
  • Prevents fretting
  • Highly reproducible
  • Good corrosion resistance
  • Color option for distinctive appearance
  • Shim geometries according to customer specification

Application

  • Frictional joints
  • Flange joints
  • Joints with central bolt
  • Bolt connections
  • Fastener systems
  • Shaft-to-collar connections

Storage

Dry storage recommended

Assembly

Assembly, i.e. applying the bolt preload on a crankshaft with a central bolt design, causes the diamond particles to press into the softer surface of the counterpart. As a result, a micro scale form fit is created between the base part and its counterpart ( Fig. 1 and Fig. 2 ). The key parameters influencing the extent of micro scale form fit are the counterpart material, the counterpart surface roughness and the applied surface pressure. Figure 3 shows typical coefficients of static friction for various material combinations with and without an 3M™ Friction Shim.

Tribosystem with 3M™ Friction Shim
Fig. 1: Tribosystem with 3M™ Friction Shim
Contact surface of friction joint with 3M™ Friction Shim after assembly and disassembly
Fig. 2: Contact surface of friction joint with 3M™ Friction Shim after assembly and
disassembly
Results of series of tests on the coe cient of static friction (the shaded areas of the bars show the variation)
Fig. 3: Results of series of tests on the coefficient of static friction (the shaded areas of the bars show the variation)

Automotive Applications

3M™ Friction Shims create possibilities for lightweight and compact design while increasing potential load and peak torque in bolt connections.

Properties

Especially in the automotive industry, there is a general move toward compact, lightweight designs that must never theless be totally reliable. Typical applications are central bolt designs in crankshaft and camshaft applications, continuous variable timing, balancer shaft modules, as well as shaft-to-collar connections. The demand for maximum power density, i. e. the transmission of ever greater forces and torque in increasingly compact designs, poses a major challenge to engineers. In friction joints, the given coefficient of static friction imposes definite physical limits on power transmission capabilities. These limits can be overcome with frictionenhancing coatings. When friction joints are designed, physical parameters such as overall size and surface pressure usually can only be varied in a tight window. Load transmission capability in friction joints is thus limited by the friction coefficient of the mating materials. But many applications require higher levels of power transmission. Therefore new ways of enhancing power transmission capability need to be found. One approach is to apply a nickel diamond coating either to the actual parts of the joints or to friction shims for installation in the joint. Depending on other application parameters, the coefficient of static friction can even exceed 0.6, resulting in a greatly increased load transmission capacity.

Processing

3M™ Nickel Diamond Coatings consist of an electroless nickel matrix in which a specified quantity of diamond particles of defined size is embedded. These coatings can be applied either to the joint components directly or to thin shims for installation in the joint. After coating, the parts are heat-treated to relieve inherent tensile stresses and to impart sufficient diamond retention strength.

Assembly

Assembly, i.e. applying the bolt preload on a crankshaft with a central bolt design, causes the diamond particles to press into the softer surface of the counterpart. As a result, a micro scale form fit is created between the base part and its counterpart ( Fig. 1 and Fig. 2 ). The key parameters influencing the extent of micro scale form fit are the counterpart material, the counterpart surface roughness and the applied surface pressure. Figure 3 shows typical coefficients of static friction for various material combinations with and without an 3M™ Friction Shim.

Applications

3M™ Friction Shims offer a simple but very cost effective way to transmit up to four times higher torques than conventional systems. And there is no need to modify the joint design. In production are a variety of engine applications mainly focusing on crankshaft, camshaft and balancer shaft module. Further applications are steering, suspension, transmission, chassis and body. Many car manufacturers, such as Audi, BMW, Chrysler, Daimler, Ford, GM, Mazda, Porsche, VW and Volvo are relying on 3M™ Friction Shims in their designs. By now there are already millions of friction shims on the road. In addition to automotive applications, 3M™ Friction Shims and Coatings are widely used in demanding motor sports applications.

Wind Energy Applications

3M™Friction Shims and Coatings provide a reliable solution to increase the coefficient of friction in bolted or shaftcollar connections. They enable higher potential loads and torque rates with a compact and lightweight design.

Technical and economic demands

In the wind energy sector as well as in many other industries, technical and economic reasons are drivers for the following trends in component requirements:

  • Higher power density: Increasing loads with reduced weight and constructed space
  • Ease of installation
  • Long life and maintenance free operation
  • Reliability and safety
  • Cost efficiency

To transfer higher loads in friction joints such as flanges or shaft-collar connections, components or fasteners generally have to be increased, which in turn impacts negatively on size, weight and costs of the overall system. A better approach than increasing the size of components is trying to increase the coefficient of friction between the components using 3M™Friction Shims technology.

Advantages

3M™ Friction Shims and Coatings increase the friction at the joining surface of two components up to a factor of 4, and so extend the freedom in the design of individual components or the entire system. 3M™Friction Shims and Coatings offer a simple yet very effective solution to the following requirements:

  • Increase of transmittable forces and torques of a connection
  • Reduction of component sizes and weights
  • Consequential weight reduction of adjacent components and the overall system
  • Increase of safety factor
  • Cost reduction of individual components
  • Ease of use
  • Insensitivity to lubricants
  • Principally reusable after disassembly
  • Application without the need of constructive changes

Functional principle

The functionality of 3M™Friction Shims is the result of diamond particles with defined size and distribution protruding from a nickel coating. The coating is applied on thin steel foils or directly on the surface of one of the mating parts. During assembly of the components, the diamonds penetrate the counter surfaces and create a micro-scale interlock. This method allows higher loads to be transmitted through the connection in a reliable and reproducible way. The resulting coefficient of static friction can reach a value of 0.6 or even higher, depending on the application parameters.

Applications

Typical examples of applications in the field of wind energy are flanges and other connections in the powertrain, bolted connections on the bed plate and the fasteners of bearings, brakes and other components. For shaft-collar connections and torque limiters, the components are usually coated directly. The manufacturing process is certified according to ISO TS 16949 and therefore meets the stringent requirements for automotive applications. To date, 3M™Friction Shims and Coatings have been used millions of times by the automotive and various other industries. 3M™Friction Shims has also been certified by Germanischer Lloyd for various material combinations and application parameters, making it versatile for use in the wind energy sector.

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