Percussion Weld Monitor 

The Percussion Weld Monitor by MTI MicroWelding provides waveform analysis to help you develop weld settings, define a “Signature” waveform for a particular product, evaluate production welds and collect data to meet your QC requirements.

It is an optional part of the Percussion Welder system, alongside the 858 and the 726 Bench Fixture. Instead of judging a weld only by how it looks, you compare the electrical waveform of each weld with the waveform of welds you already know are good, and get a pass or a fail for each one.

Each percussion weld produces a current waveform that rises to a peak, dips as the parts make contact, and then continues. The monitor looks at three characteristics of that weld energy output:

• Maximum amplitude: the maximum current of the weld, the first peak.
• Point of contact or inflection: the dip in the waveform where the parts meet.
• Waveform: the overall shape of the current curve over the weld.

For each characteristic you set a search area, a window in which the monitor looks for it. A weld that falls within the limits you set for all three passes.

In the Learning stage you make welds on your product to create a signature waveform. Use welds you have inspected and know to be good, because everything the monitor later calls a pass is measured against this signature.

During Learning you also configure the search area for each of the three characteristics. The screen shows the waveform of the last weld alongside all the waveforms collected, with the maximum and the inflection point marked, so you can see where each characteristic sits and how much weld-to-weld variation your process has. Learning can also help you develop your weld settings, because you see what each change does to the waveform.

Once the pattern is created, the Configuration step prepares the monitor for production. You select the pattern to test against and make any adjustments to its search areas, tightening or loosening each window to suit how strictly you need to hold the weld.

You also set the duration of the digital output signals for a pass and for a fail. That is what lets the monitor drive an alarm, a light or an automation step, and keeps the signal long enough for your equipment to read it. This is the step to review again if you change product, part number or fixture.

In the Test stage the monitor compares each subsequent weld with the pattern selected in Configuration. If the weld is within the parameters set for maximum current, inflection or contact point, and waveform, the system shows a Pass screen and generates a digital output signal to monitors and weld analyzers.

If any one of the three characteristics fails, the system shows a Fail screen and outputs a fail signal, so you can verify further. The result is available for every weld, not only for the welds someone chose to inspect.

The system overview diagram shows how the pieces connect. The monitor software runs on a laptop. A data acquisition (DAQ) unit connects to the laptop by USB and takes the weld signal from the welder, which has an internal shunt for that purpose.

The DAQ also provides digital TTL outputs. One output indicates that the application is running, one is the pass signal and one is the fail signal. The pass and fail signals are produced for the time you configure, in milliseconds. These outputs are what you wire to alarms, indicators or an automated line. For installation details, contact us for the operating manual.

The monitor collects data to meet your QC requirements and can store data and waveforms. The software screens on this page show how that looks in use: a historical data table, stored waveform views with their data tables, and a log of actions taken in the software with dates and users.

The test screen also shows the result of the last test for each of the three characteristics, along with a count of welds and a yield percentage. Which records you keep, and for how long, is a decision for your quality system. Ask us how the monitor data would fit it.

The monitor suits processes where you want a pass or fail on every weld, or a documented record of how each weld compares with a known-good signature. It is also useful during development, because the waveform shows the effect of each setting change.

It checks the electrical signature of the weld energy. It does not replace validating joint strength on your own parts, so we recommend pull testing and your usual inspection when you set up a process, and then using the monitor to confirm that production welds match the welds you validated.

The monitor is optional. Many applications run without it. Ask us whether it makes sense for yours.