Design 

The increasing complexity of product designs has led to interest in percussion welding, which allows intricate welds in milliseconds. It handles delicate designs with fine wires and small joint surfaces, and it gives engineers and designers more options because it joins metal combinations that are difficult to weld.

It is used for sensors, electronics, lighting, heating elements, batteries, medical devices and automotive equipment. In these designs the weld is usually a lead, pin or terminal, and the surrounding parts, insulation or plating cannot take much heat.

The material pair is the first design decision that affects the weld. Percussion welding joins dissimilar metals directly, but each pair needs its own settings, and a few pairs need testing before anyone can say more.

Our lab database covers 33 materials and 68 material pairs in 131 schedules. Use the material compatibility checker to see whether your pair is in it, and the weld schedules table for the settings. If it is not, send the materials for a free applications test.

Read more in the guide to dissimilar metal welding.

These are joints we have welded and recorded in our lab, so they are a useful starting vocabulary when you sketch a design:

• Wire to a flat strip.
• Wire end to wire end (butt joint).
• Wire to a tube.
• A screw to a washer.
• Wire to a disk, including stranded copper wire to aluminum.
• Several wires joined at one junction.
• Thermocouple wires welded at the bottom of a drilled hole.

Each joint is two surfaces brought to a gap, so the geometry has to let one part approach the other cleanly. Tell us the shapes and sizes and we will say what we expect before you build parts.

In a percussion weld the two parts must be held with their weld points at a pre-defined gap and brought together squarely. The design has to leave a way to do that.

The 726 Bench Fixture holds the wire in a moveable wireholder with a spring-loaded thrust, and the workpiece in a stationary workpiece holder. It has Z-axis and Y-axis adjustment, a gap adjustment and an initiation lever, and a foot pedal or hand switch triggers the weld.

For parts that do not fit the standard holders, we review part geometry, joint design and fixturing strategy with your team before you cut metal.

A weld is defined by a small set of parameters. Our lab schedules record them for each material pair:

• Wire diameter.
• Actuator velocity.
• Delay time.
• Capacitance setting.
• Weld voltage.
• Pulse, long or short.

On the 858 these map to the front-panel dials and switches. Use the Parameter Finder to get a starting set for your pair and wire size, then change one setting at a time. Schedules are starting points, not guarantees, and every application is validated on your own parts.

Decide at design time how the weld will be checked. Welds are inspected visually, by mechanical testing, or with the Percussion Weld Monitor.

A pull test is the simplest mechanical test. In pull tests the wire often breaks before the weld. The monitor adds a record of every weld: it learns a signature waveform from good welds and shows Pass or Fail for later ones, which gives you documentation for production.

State your strength, resistance and appearance requirements in the specification, and we will test against them.

A design that works on the bench can go to production without a change of process. The same four-stage weld is used from the first prototype to the production line.

• Prototype: evaluate the application, then a process evaluation with free applications tests of your materials.
• Development: usually in your environment, or at MTI MicroWelding if you prefer.
• Production: operator training, weld parameter documentation, and integration into automated lines where needed.

See process development for the stages in full, and talk to us early: a joint designed for percussion welding is easier to weld than one adapted afterward.