Ultrasonic Equipment Manufacturers Use MTI-2100 Fotonic™ Sensor for Precise and Repeatable Vibration Measurements - MTI Instruments - #1

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MTI Instruments, Inc. 325 Washington Avenue Extension Albany, NY 12205 PH: +1-518-218-2550 OR USA TOLL FREE: 1-800-342-2203 FX: +1-518-218-2506 sales@mtiinstruments.com www.mtiinstruments.com APPLICATION NOTE Ultrasonic Equipment Manufacturers Use MTI-2100 Fotonic™ Sensor for Precise and Repeatable Vibration Measurements Introduction Take a look around and you’ll be surprised to see how many products you come in contact with everyday that use ultrasonics for assembly. Diapers, plastic toys, bags and packages, to name a few, all rely on a process called ultrasonic welding. Ultrasonics is defi ned as acoustic frequencies above the range audible to the human ear, or above approximately 20,000 Hertz. When a part is excited at a frequency it generates energy. The amount of energy is proportional to the frequency and amplitude at which the part moves. The higher the amplitude and frequency, the greater the energy generated. To create this motion typically a high voltage, high frequency electrical signal is supplied to a piezo-electric crystal stack. As the crystals are excited they expand and contract at the same rate as the excitation signal. The amplitude, or peak-to-peak travel distance, depends on the piezo stack length and voltage applied. Typical frequencies range from 20 to 60 kHz with amplitudes from 100 micro-inches (2.5 microns) to over 0.002” (50 microns). An “ultrasonic horn” is the device which concentrates this energy and applies it to a process. They come in many different sizes and confi gurations depending on the task for which they are designed. Figure 1 shows several different horn confi gurations. As the tip of the horn (or contraction area) is brought in contact with a part at a certain pressure, frictional heat is generated causing the material to plasticize locally, creating an insoluble connection between two parts within a very short period of time. As the energy is removed, the part will cure, creating the bond. An example of a typical bond is the seam of a plastic bag as shown in Figure 2. The Problem In order to create a consistent bond or weld the ultrasonic horn must produce a specifi ed amount of uniform energy. Varying energy distribution across the face of a horn or varying frequency will result in an inconsistent process. It is important for the operator to precisely control the motion characteristics of the horn in order to maintain product consistency and integrity. Periodic measurements of horn frequency and amplitude are therefore required. MTII appnote: ultrasonic.pdf - Page 1 of 2