Plastic Parts Assembly—Adhesives or Welding?

From sleek, curvy headlights on fancy automobiles to built-for-purpose designs such as earbuds, medical devices and consumer packaging, plastics are part of our daily lives. Adhesives have typically been used in assembling these plastic parts into their finished form.

Emerson's Tarick Walton

In an Appliance Design article, Adhesives or Welding for Plastic Part Assembly? [free site registration required], Emerson’s Tarick Walton contrasts the two approaches.

Tarick opens noting that the decision on assembly technology is based on two factors:

…business factors and part factors. Business factors involve your product lines and production needs, and the degree of speed, flexibility, and scalability that are needed in your assembly operations. Part-related factors go right to the part itself: its performance requirements, shape, and materials of construction.

Some advantages of adhesive-based assembly include flexibility in shapes, plastic materials and sizes. It can be a solution for:

…low-quantity assembly jobs, including part prototypes, pre-production product samples, or production runs that include parts that include optional components of differing sizes or shapes.

Disadvantages of adhesive-based assembly is increased care and maintenance to keep the applicator clean and free of clogs and blockages. The adhesive:

…must be applied with consistency and care to ensure a complete and cosmetically pleasing bond.

As the production rate increases, the cost of the consumable adhesive increases.

Ultrasonic welders, such as the Branson ultrasonic plastic welding products, provide:

…manufacturers with a high degree of flexibility through modularity of the tooling setup. By using a single ultrasonic welder and a range of part-specific tooling, manufacturers can produce a variety of different parts on a single assembly line.

These ultrasonic welders work by creating friction between the parts to be joined. The:

…mechanical vibrations are transmitted to the interface between the parts, where it is focused on a triangle-shaped bead, the energy director, which focuses the vibration to create intermolecular and surface friction. This friction creates heat and a subsequent melt, which solidifies into a welded bond.

While upfront capital costs can be higher for ultrasonic welding technology and associated tooling, the costs associated with consumables and more frequent maintenance are avoided. Generally:

…those with production volumes ranging from tens of thousands to millions per year generally realize a significant financial benefit with an ultrasonic welding process.

Read the article for more on advantages in assembly cycle times, material considerations, parts geometry, and design considerations. Visit the Ultrasonic Plastic Welding area of and see the Branson GSX Ultrasonic Welding Platform video to learn more about this reliable sealing and parts assembly technology.

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