Component assembly

The Injected Metal Assembly (IMA) process is an alternative to other joining techniques. It has been used to help assemble a kitchen appliance

Rivetting, adhesive bonding, soldering, brazing and welding are all familiar means to assemble small components. Perhaps not so familiar is the Injected Metal Assembly (IMA) process.

In operation, the IMA system uses molten metal, usually a zinc alloy, to form a permanent mechanical joint to accurately assemble small components.

Components are automatically positioned by a specially designed assembly tool in precise relationship to each other, while molten zinc alloy is injected at the intersection where the components are to be joined. As the molten metal solidifies and shrinks towards its theoretical centre, a locking action occurs, resulting in a mechanical joint or hub. This occurs in milliseconds, producing an assembly ready for use in the next production step.

Because the system uses an assembly tool to hold the components as they are joined by the molten metal, accuracy and repeatability are consistent over large production runs. The molten alloy allows the joining of a diverse range of materials such as metals, plastics, ceramics and elastomers.

Kenwood has been using the IMA process to eliminate multiple operations in the production of motor drive assemblies for the Chef and Major kitchen machines. For this application, a sintered iron bevel gear and a zinc alloy gear wheel are assembled to a milled steel shaft by the process.

Originally, the gears were pressed onto the shaft and pinned through and across to obtain the required drive. But the press fitting and subsequent drilling resulted in production problems. Because pockets of carbon, formed in the structure of iron during the sintering process, are very hard, drill life was short. Some changes were needed to accommodate the process. A knurled portion was required on the shaft to lock the zinc alloy joint in place and the bore details of the gears were revised to allow the zinc alloy to form a strong joint as it solidifies and shrinks.

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