Measurement Parameters of Ultrasonic Oscillatory System during ...

2MEASUREMENT PARAMETERS OF ULTRASONIC OSCILLATORY SYSTEM DURING WELDINGTHERMOPLASTICSof voltages and currents flowing through UOS with areference quantity certain by practical consideration.At use of the circuit diagram of welding «on the fixedtime» the probability formation of a poor-quality weldedjoint is defined by following parameters:1. Instability of a resonant frequency and amplitude ofoscillation UOS;2. Deviation of initial thickness of welded materialsfrom optimum;3. Instability of weld conditions (temperature of awaveguide and magnitude welding force).4. Impurity of welded surfaces.Not large changes of parameters of a welding regime,geometry of details and properties of materials can lead tothat the demanded time of welding will appear more orless time installed by the relay. Thus in the first case willbe observed skin weld, in second - burn weld. It instabilityof the results gained at welding on the fixed time speaks.Improvement of quality in this case are aimed to attaindue to maintenance of a constancy of parameters of awelding regime, however it considerably complicates adesign of the equipment.Unlike the circuit diagram of welding «on the fixedtime» at which sampling of duration of a welding time isnot connected absolutely not with education of a weldedjoint, the circuit design of welding «on the fixedsettlement» is partially connected with kinetics ofeducation of a welded joint. In this case the probability ofimplementation of a poor-quality welded joint is definedby instability of initial thickness of welded materials.Use of a welding method «on the fixed settlement»assumes the certain deformation of a zone of a seam, thatsometimes happens is inadmissible owing to a decline of apackaging of a product. The basic deficiencies of a way ofmanagement process of ultrasonic welding («on the fixedsettlement») [8,11,14] is necessity of recustomizing of theequipment for realization of welded joints from various onproperties and thickness of materials, and also presence ofvarious sensors (end switch, optical, end-of-strokesensors).At ultrasonic welding with a batching of energy underthe kinetic characteristic the information on aphysicomechanical condition of welded materials is used[1]. During ultrasonic welding there is a softening andtransition of a material in a plastic condition, magnitudeof a static compression pressure changes. Therefore thesquare of contact of a welded material and welding toolUOS changes. There is a change of an amplitude ofoscillation of oscillatory system and as consequencechange of a current, a voltage, a phase angle betweenthem, the power consumed UOS during welding. Thepublications of authors [6,7,9,10,12] connected withmeasurements on the electric side of the generator ofvoltages and currents flowing through UOS, matchingspeed or amplitude of ultrasonic oscillations in a material,to a sign on a speed-up of a straining [8,11,14] materialsunder a waveguide and the high-frequency energy [12]consumed UOS are known. In the specified waysmeasurement of the signal proportional to an amplitude ofoscillation and management of process of welding makeby comparison of signals with a reference quantity. Thusa batching of energy carry out with high repeatability ofprocess.The basic deficiencies of these ways of management isthat the offered criterion of definition of transition of amaterial in a plastic condition during ultrasonic weldingis not to constants. Application of big static pressuresduring ultrasonic welding lead to a damping of workingtool UOS, decrease of an amplitude of oscillation andimpossibility of the control of process ultrasonic welding.Besides during welding there is a nonlinear changeproperties of polymeric materials, heating UOS, decreaseof its resonant frequency and an amplitude of oscillationduring welding.Because any of ways of management used now processof ultrasonic welding to the full does not consider changeof parameters UOS, it is necessary to solve followingproblems:1. To execute measurements of electric parametersUOS during ultrasonic welding.2. To define the effect, changing properties of weldedmaterials on parameters UOS.3. To research effect welding pressure on electricparameters UOS.III. RESULTS OF MEASUREMENT OF ELECTRIC PARAMETERS UOSGeneratorf oс , f oпU, I, f, ϕ (I,U)ControlDURING WELDINGAt research of process of ultrasonic welding it was usedUOS for welding thermoplastic, operating at a frequencyof 22 kHz, polypropylene weld specimens by thickness of1,1 mm, lapped combined.The measuring complex is developed for measurementof electric parameters UOS during ultrasonic welding. Infigure 1 the block diagram of the measuring complex ofelectric parameters UOS is presented.The measuring complex is connected to a diagnosticconnector of the ultrasonic generator, and as in "rupture"of a cable of UOS. Such connection provides anControlMeasuringcomplexComputerU, I, f, ϕ (I,U)DataFig. 1. Block diagram of measurement of parameters UOS.UOSopportunity of measurement of parameters followingsignals: