What is behind MM-W?

Use of the LiteWWeight adapter. © www.mm-welding.com

With the MM-W technology, which is patented by MultiMaterial-Welding AG and sublicensed by KVT-Fastening parent Bossard, the LiteWWeight variant, for example, uses thermoplastic fasteners in a pin, sleeve or freely selectable form instead of conventional fasteners (see Figures 1, 2 and 3). The functional principle: The thermoplastic fastener is driven through the surface layer in phase 1 by a combination of ultrasonic movement and pressure. Due to the friction between the fastener surface and the component, the surface of the fastener itself becomes the joining material. Thanks to its material hardness, however, it retains its shape and function. The MM-W process uses the combination of ultrasonic energy, material hardness and the design of the fastener to drive it into the component on the one hand and to use the melted plastic as a bonding material on the other. The porous material of the component is ideally filled via the capillaries of the melt, which results in a larger-volume and larger-surface holding anchorage.

MM-W technology has various advantages. One of these is the significantly shorter process time compared to alternative joining techniques. This leads to more efficient inline processing: the entire joining process takes less than a second. No curing or cooling times need to be taken into account afterwards. The joint can be loaded immediately after the joint is released. In most cases, there is also no need to pre-drill a hole in the material. Another advantage: the technology offers a high degree of flexibility, as the fasteners can be used without pre-positioning to compensate for tolerances. In addition, the MM-W method guarantees stronger bonds than many other fastening methods. The background to this is that by designing a surface shape and size that meets the requirements in combination with the selection of the appropriate thermoplastic fastener, loads are applied to a large area of the component. This not only creates a fastening point, but also integrates the fastener into the component both functionally and visually.

These new freedoms in the design of applications are also not tied to specific geometry specifications, such as radial symmetry. In addition, thin substrates can also be provided with connection points without visually impairing the "reverse side". Processing is also cleaner compared to conventional joining techniques, as no additional materials or pre-treatment of the surfaces are required and no waste is produced. Last but not least, the ability to statistically control the process guarantees the consistent quality of each individual connection point and makes the process permanently reproducible and reliable.

Areas of application for MM-W

The application example shows a loading floor cover made of sandwich materials. © www.mm-welding.com

The main focus of the constantly evolving MM-W technology is currently on joining foamed materials, sandwich materials or honeycomb panels, such as those used in the automotive and transportation industries (see application example in Fig. 4). Joints between sheet metal and compact plastics are also possible. In this case, a deep-drawn "pore" is driven into the compact thermoplastic in the sheet metal. As a result, a metallic fastener, for example a nut or a bolt, can be equipped with a specific anchoring geometry, which is then applied to the back of a component with a Class A surface using the MM-W process, thus creating an invisible joint. Further developments are in the test phase and will be applied in the near future as requirements increase.

All in all, MM-W technology combines the advantages of conventional joining and bonding technology. It combines high strength with fast and controllable processes, increases product quality and process efficiency and therefore offers a completely new alternative for joining lightweight materials.

Florian Beer, Managing Director at KVT-Fastening Germany / ag