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Another remedy is to look at equipment that operates on a higher frequency, perhaps 30 or 40 kHz, provided the tooling required by the application is available for use at this frequency. Higher-frequency equipment produces lower amplitude output, but compensates by resonating at a higher frequency. Thus, higher- frequency welders are considered "more gentle" in the application of ultrasonic energy to parts. Electronic assemblies, especially those with delicate timers/oscil- lators and other components located on printed circuit boards, have benefitted from this approach. In a similar way, parts that suffer from "diaphragming" or "oil canning" due to excessive movement of one of the mating parts, will often benefit from the change to higher-frequency equipment. Another potential factor is equipment malfunctions. These rarely occur without warning. One obvious example is a change or increase in the noise generated when a welder is operating. Experienced operators and maintenance personnel are often attuned to such subtle harmonic fluctuations and should always communicate about these changes to supervisors. Heeding "a squeaky wheel" sooner rather than later may well permit iden- tification and resolution of a problem before production is adversely affected. Similarly, newer ultrasonic equipment allows users to perform interactive diagnostic function checks, which if interpreted properly and used in combination with other warning signs such as noise, can alert the user to worrisome trends before they become major issues. Power supplies, through advanced communication protocols, can obtain data such as "weld graph results" and "horn scans" that can be compared with baseline data obtained when the equip- ment was new, recently serviced, or known to be performing up to standard. With this information, experienced users can then focus their troubleshooting and determine whether additional action or further monitoring is required. Once an area of concern has been identified, substituting known good components for suspect components is one way to positively identify weld equipment that require repair or corrective action. Examples of useful diagnostic data include: • Weld graph data. This can help pinpoint differences between good parts and suspect parts. Data displayed on a weld graph, as seen in Fig. 3, include amplitude, current draw, power, frequency, and phase. Amplitude, phase, frequency, and current variations can indicate a problem with a power supply or stack. A discrepancy in power draw could indicate a process change (such as in weld pressure), part-geometry change (tolerances, especially in the joining area may have changed) or a stack-component problem (a horn or con- verter is beginning to fail). • Diagnostic scan of horn. This identifies whether the horn is drawing more power (displayed as an increase in the wattage needed to run in air). Increased power draw could indicate that a crack is forming in the horn. Such cracks are sometimes internal and therefore not always visible to the naked eye. • Random data. Data that appears chaotic when compared with known, good data may indicate a fault in the converter, the horn, or in the radio-frequency cable, as seen in Fig. 4. PROCESS PARAMETERS & MATERIALS Careful control and documentation of process parameters is another area that cannot be overlooked. Medical and automotive component producers know this and follow strict procedures, often mandated by regulating agencies such as the FDA, that result in a high degree of success when using ultrasonic welding. Unfortunately, processors of other products, such as toys or disposable products, often operate under much less stringent Substituting known good components for suspect components is one way to positively identify weld equipment that requires repair or corrective action. FIG 3 DCX Test & Graph Screen of a Typical Good Weld Diagnostic of a good ultrasonic weld: Within 150 millisec after weld initiation, all parameters of the weld are up to specification and continue to operate smoothly to weld conclusion. 90 72 54 36 18 0 -18 -36 -54 -72 -90 20450 20350 20250 20150 20050 19950 19850 19750 19660 19550 19450 120 108 96 84 72 60 48 36 24 12 0 Frequency, Hz Power, % / Current, % / Amplitude, % Phase,° 0 75 150 225 300 375 450 525 600 675 750 Time, millisec Amplitude Phase Current Power PMW Amplitude Frequency Draw from 0 ms to 750 ms Graph Selection Phase X Value 0 Y Value 0 Update Value Frequency Power Current Amplitude Phase × × × × × × Export Graph Data Update Graph Set Default Redraw Graph 58 JUNE 2017 Plastics Technology PTonline.com Trouble shoot ing