Putting It All Together: Solutions

Explore the world of sonic welding automation - a fast, efficient and reliable method for plastic and metal joining.

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Sonic Welding Solutions

When it comes to plastic joining techniques, there are only a few methods that stand up to the demands of industrial manufacturing: adhesive gluing, threaded fastening and ultrasonic welding. Adhesive bonding and bolting are both more mature technologies, whereas sonic welding is the relatively newer joint design that has carved out a niche in fast, low complexity, nonstructural plastic joining projects. 

Overall, there is a need for all three joining styles in the industry, each with their ideal applications. Read on to learn more about ultrasonic technology and how it compares to its rival joining techniques.

Building With Sound: The Fundamentals of Sonic Weld Joining

Sonic welding is accomplished by either handheld or automated joining systems that share the same operating principles: Two separate material pieces are placed into a workstation where they are physically pressed together between a welding arm and a solid anvil underneath. The welding arm is made up of a sonic welding converter, booster and sonotrode (or horn), altogether powered by a sonic welding controller. 

When the welder is activated, the weld horn receives physical vibrations from the converter and booster set attached above it, which pushes the horn down into the materials below by a certain dimension (the amplitude), and then does so repeatedly up and down, again and again (the frequency). So, a complete sonic weld specification incorporates both factors, reading as in this example: "15 µm amplitude @ 30 kHz frequency." This weld spec means that the weld horn will stroke up and down a length of 15 µm (microns) similar to a miniature jackhammer, and will do so at 30,000 strokes per second. 

This is how a sonic weld joint is created; by mechanical vibrations generating enough friction between separate material pieces that the two become fused into one solid object.    

Sonic Welding Automation Services - AMS

Comparing Sonic Welding to Other Plastic Joining Techniques

A useful way to understand sonic welding’s capabilities is to break the topic down into its main design considerations, and then compare each feature to the next most common joining methods (namely adhesive bonding and threaded fastening).

Designing for Sonic Success: Material Considerations

By far, the most important consideration around sonic welding is what materials to use. Plastics are the most popular material type selected for sonic welding, though some soft metals, synthetic fabrics and even glass are options as well.

Plastic materials can be split into two categories:  thermosets and thermoplastics. Thermosets are too rigid to be sonically welded, but thermoplastics are fluid enough that many can be easily bonded by sonic welding. High-frequency sound waves resonate with thermoplastics so well, that the plastics can reach glass transitions (ideal bonding temperatures) almost instantly and then can cool just as near-instantly back to room temperature. Further, the heat required to enter glass transition is not added as raw heat, but is rather induced into the plastic by intermolecular friction generated by ultrasonic vibrations. Sonic welding can also be very tightly focused to tiny weld locations, all but eliminating material distortion, weld preparation and post-cleaning.


Common social welding material options include:

  • Acetal
  • Acrylic
  • ABS
  • Polyamide
  • Polycarbonate
  • Polyester
  • Glass
  • Polyethylene
  • Polyphenylene
  • Polypropylene
  • Polystyrene
  • Nylon
  • Some thin metallics such as aluminum, copper and nickel

Automating Sonic Welding Processes

Hobbyists and mass product manufacturers alike can utilize sonic welding equipment, just at different scales and levels of automation to best suit their needs.  

Manual Sonic Welding

Usually performed on a benchtop using a handheld sonotrode. Manual sonic welding can produce one weld at a time and is subject to the skill and consistency of the operator in achieving high-quality welds consistently.

Ultrasonic Joint Testing

Performed using an equipment station in which parts are lined up and situated by a human operator. Once the parts are loaded, actuated sonotrodes are extended to the weld locations, the welds are executed and the completed joined assembly is then removed from the system by hand.

Fully Automated Sonic Welding

The most efficient welding option, can automatically feed in parts to be welded, align and orient the parts in the weld bay, robotically position multiple sonotrodes to the weld points, run quality confirmation checks, execute the welds and then discharge the part to make room for the next part in line. All virtually hands-free. 

AMS offers two plastic joining system platforms that can provide sonic welding along with other plastic fabrication processes. They differ in their automation levels. 

  • Our AMS PJ-301 is a versatile, semi-standard system for ultrasonic staking, forming and spot welding. With semi-automatic operation, poka-yoke functions and outstanding productivity, the PJ-301 is a great general purpose plastic joining machine. This system is easily reconfigurable for future requirements.
  • Our AMS PJ-401 is designed for high-volume ultrasonic plastic welding applications requiring precise welding profiles and specifications, exact locations, high levels of error-proofing and repeatability to ensure consistent welding. The PJ-401 offers larger part sizes, higher volumes, shorter cycle times, advanced recipe-driven PLC controls and extensive data reporting.

Sounding Off

Thanks to over 50 years of engineering development, plastic joining has evolved into a robust material science discipline, the likes of which have given us sonic welding (and so much more). Entire modern industries have been reinvented on the backs of plastic sonic welding technologies, evident in many aspects of our daily lives.  

As sonic welding solutions continue to develop, we expect to see monumental new capabilities unveiled, especially involving metallic jointing, dissimilar plastic welding and increasing structural weld strength that will rival bolted connections. Automated sonic welding systems will have an increasing role to play as these advancements come to fruition, and AMS is dedicated to leading the (sound) wave. Contact us today to talk about your next project.

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