Creating the perfect assembly

The melding of parts with injected metal assembly

Comments Off on Creating the perfect assembly September 12, 2009
by Steve Purwitsky

Traditionally, when engineers specify that parts should be securely joined in an assembly, adhesives, screws or some other bonding solution are the most likely candidates. For many applications, however, there may be a better way.

First conceived by the company’s founder, Bill Fisher, more than 60 years ago, Peterborough, ON-based FisherTech’s Injected Metal Assembly (IMA) process can, in many cases, provide a superior solution for small component joining and assembly production while reducing manufacturing costs.

According to the company, most applications that require assembling two or more parts using adhesive bonding, brazing, swaging, staking, press fitting, riveting, soldering, crimping or other joining processes, are ideal for the IMA process. In addition, the process has the potential for eliminating quality and cost issues that are often factors in traditional multi-step assembly processes.

In practice, the company’s process uses molten zinc alloy as a joining agent. First, the components to be assembled are positioned in their correct relationship by a custom-designed assembly tool. After the tool closes, aligning the components in their correct relationship, molten alloy is injected under pressure into the intersection of the components.

Cal Craig P.Eng, manager of FisherTech Business Unit, explains that two or more components of virtually any shape can be joined. In fact, the alloy is often used to cast one or more of the individual components during the joining process to eliminate fabrications, material costs and inventory.

"The injected alloy solidifies in milliseconds creating a strong, permanent mechanical lock between the components, free of flash or burrs," he says. "Cable assemblies and varied automotive and appliance assemblies are particularly well suited to the process."

Once cast, the bond exhibits properties common to adhesives, such as stress distribution and the ability to join a diverse range of dissimilar materials and others of different thicknesses. In addition, the zinc alloy joint requires no special surface preparation and has no peeling or thermal degradation issues common with conventional adhesives.

In many applications, in fact, the IMA process has advantages over conventional bonding. For one, it is a one-step manufacturing solution. In addition, small components of just about any type of material can be joined by the IMA process including metals, ceramics, glass, fibres, paper, elastomers and plastics. Craig adds that functional components made from one of these materials are often eliminated by die casting them during the assembly process. For example, pinion gears can be cast in position as a gear and shaft are locked together by the alloy joint.