Measurement Parameters of Ultrasonic Oscillatory System during ...

1MEASUREMENT PARAMETERS OF ULTRASONIC OSCILLATORY SYSTEM DURING WELDINGTHERMOPLASTICSMeasurement Parameters of UltrasonicOscillatory System during WeldingThermoplasticsAlexey N.Slivin, Alexey D. Abramov, Denis S.Abramenko, Student Member, IEEEBiysk Technological Institute (branch)of Altay State Technical University after I.I. Polzunov, Biysk, RussiaAbstract - In the article the basic problems interferingevolution of automatic-control systems by process ultrasonicwelding are analysed, measurements electric parameters ofultrasonic oscillatory system during welding thermoplastics,directed on search ways raise of strength a welded joint areexecuted.UI. INTRODUCTIONLTRASONIC welding in modern conditions ofmanufacture allows to solve many problemsconnected with reception of the qualitative joint of anythermoplastic materials. Ultrasonic welding, in most casesin practice has successfully replaced thermal, highfrequency,frictional and other known ways of welding[1].Wide application of ultrasonic welding speaks that atsampling optimum production engineering and thenecessary equipment development engineers andindustrial engineers are based on widely knownadvantages and advantages of ultrasonic welding [5]:1. An opportunity to carry out welding at temperaturessmaller temperatures of smelting welded thermoplasticmaterials.2. High quality of a welded joint.3. An opportunity to carry out welding withoutpreliminary clearing welded surfaces of various pollution.4. Exclusion of excessive heating weldedthermoplastic materials, through local allocation of heatin a weld zone.5. To get a welded joint thermoplastic materials atwelding at a great distance from a point of feeding into ofenergy that allows to carry out joints in remote places.6. Absence of auxiliary glutinous components.7. Durability of a welded joint to dissolvents, etc.Listed above advantage of ultrasonic welding have ledto that at creation of new materials and products there isno any more a question on sampling a way of theirwelding. However, there is a some of problems which areconnected with automation process of ultrasonic welding.Thus the main problem is definition of a time interval ofthe ultrasonic affecting necessary for formation a weldedjoint in thermoplastic polymeric materials.The basic purpose now is development of automaticways of welding and improvement of quality of a weldedjoint of products from thermoplastic polymeric materials.II. PRODUCTION OF THE PROBLEMDuring ultrasonic welding properties thermoplasticmaterials (there is a softening and transition in a isviscous-plastic condition) as a result of sorbtion of energyof ultrasonic oscillations change. It leads to decreasewelding force, to warming up oscillatory system thatcause decrease of its Q-factor and to an error signal of theoscillatory circuit. As a result, the resonant frequency andan amplitude of oscillation of ultrasonic oscillatory system(UOS) changes [1,4].As a result of these destabilizing factors stability of aprocess of ultrasonic welding and reception of aqualitative welded joint gets special value.Change of following parameters is usually made forreception of a qualitative welded joint thermoplasticmaterials at ultrasonic welding: amplitudes oscillation ofradiating surface UOS, magnitudes welding force anddurations of ultrasonic affecting. The variation in lastparameter has gained most a wide circulation.At the automated ultrasonic welding limitation of atime ultrasonic affecting is carried out by next ways:1. Method «on the fixed time» assumes use ofultrasonic affecting of constant duration at welding thesame products. Duration of ultrasonic affecting is frompreliminary experiments and is set on all weld cyclesequal, is usual by means of the electronic time relay [1].2. Method «on the fixed settlement» at whichmagnitude of deepening UOS in a welded detail ordeformation of a weld zone is saved by constant. Atachievement of the set deformation there is an automatictermination of ultrasonic affecting and restriction ofmoving UOS. Duration of a time of welding at thismethod in each separate case can be various [8,11,14].3. Method «under the kinetic characteristic» at whichis installed interconnection between an amplitudeoscillation of working end face UOS and change ofproperties thermoplastic materials as a result sorbtion ofenergy ultrasonic oscillations [9, 10, 12, 13]. Duration ofultrasonic affecting proceeds till the moment of equality

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:

3MEASUREMENT PARAMETERS OF ULTRASONIC OSCILLATORY SYSTEM DURING WELDINGTHERMOPLASTICS1. Signal of basic frequency from the setting generatorsets working frequency UOS.2. Feedback signal. Primary transformation of a signalis carried out by the internal circuit diagram of thegenerator. This signal is used in system of AutomaticFrequency control (AFC).3. Voltage on oscillatory system.4. Strength of current on oscillatory system.ϕ (U,Os)ϕ (I,U)UI001t, sFig. 2. Electric parameters UOS during welding without taking intoaccount effect of properties of materials (radiation in air).ϕ (U,Os)UIϕ (I,U)ϕ (U,Op)00 Phase 1 Phase 2 Phase 31t, sFig. 3. Electric parameters UOS during welding at constant pressure.Ι5 kg0 kg8 kg10 kg15 kg0Fig. 4. Dependence of amplitude of the current flowing throughpiezoceramic elements UOS during welding at various weld pressure.By means of these signals it is possible to computefollowing parameters UOS:1. Value of a voltage on oscillatory system.1t, s

4MEASUREMENT PARAMETERS OF ULTRASONIC OSCILLATORY SYSTEM DURING WELDINGTHERMOPLASTICS2. Value of a current on oscillatory system.3. Oscilation frequency UOS.4. A phase difference of a voltage and a current onoscillatory system.5. A phase difference between two any periodic signals(from the basic generator, a feedback, a current or avoltage on oscillatory system).For management of job of the measuring complex andas recordings and processings of the measuredinformation the personal computer is used.Communication is carried out by means of protocol RS-232.During ultrasonic welding continuous measurement ofamplitude current of mechanical branch UOS I,amplitudes of electric voltage U, a phase angle between avoltage and current φ(I, U), a phase angle between avoltage on oscillatory system and feedback signal φ(I,Os), a phase angle between a voltage and a signal basicfrequencies φ(I, Op) was made (figure 2).In figure 2 dependences of electric parameters UOS atan absent material are presented (radiation to air).During welding at an absent material value of currentI, voltage U and phase angles φ (I, U), φ (I, Op), φ (I,Os) are saved by constants during all period of ultrasonicaffecting. In this case parameters UOS remain toconstants, because of absence of effect on oscillatorysystem, changing properties of a welded material duringwelding.Dependences presented in figure 3 illustrate effect ofchanging properties of a welded material in a weld zone(a softening of a polymeric material and transition in a isviscous-plastic condition) on electric parametersoscillatory system. There is a change of followingmagnitudes: I, U, φ(I, U), φ(I, Os) and φ(I,Op).From dependences presented in figure 3 follows thatprocess of welding can be broken into 3 stages:1. Change of a welded material from a solid conditionin is viscous-plastic. At this stage there is a decrease ofvalue of current I and voltage U on oscillatory system,increase in a phase angle between a voltage and a currentφ(I,U), and values of phase angles φ(I,Os) and φ(I,Op)remain practically constant.2. The Is viscous-plastic condition. At this stage thereis maximum damping oscillatory system. Values ofcurrent I and voltage U attain the minimal value, andmagnitude of a phase angle between a voltage and acurrent φ(I,U) on oscillatory system attains the maximumvalue.3. Change of a welded material from a is viscousplasticcondition in is viscous-fluid. At this stage there isan intensive smelting a material in a weld zone. Excessesof the fused material start to be extruded from a weld zonethat reduces welding pressure on oscillatory system. Thereis an increase in value of current I and voltage U onoscillatory system, decrease of a phase angle between avoltage and current φ(I, U).One of key parameters of ultrasonic welding is weldingpressure.In figure 4 some dependences of the current flowingthrough piezoceramic elements oscillatory system atwelding of equal specimens on thickness frompolypropylene at changing welding pressure on a materialare presented.From the presented dependences follows, that, atwelding equal specimens on thickness, curves of a currentcan differ essentially from each other. It is connected, firstof all, with various force of welding pressures on weldedmaterials, both during the initial moment, and during allprocess of welding.Carried out researches have shown, that at effect of bigwelding pressures there is strong damping UOS owing towhat it is not formed a qualitative welded joint. On theother hand at small welding pressure also it is not formeda qualitative welded joint, owing to insufficient energyforwarded in a weld zone.Thus, for implementation of the qualitative joint ofmaterials it is necessary to expel effect of instabilitywelding pressures at ultrasonic welding, i.e. to expeldistortions of curves of a current.From the gained results necessity of search optimumwelding pressures during ultrasonic welding follows.The further jobs will be directed on search of optimumparameters of ultrasonic welding thermoplastic materials.IV. CONCLUSIONAs a result of the spent researches have been solvedfollowing individual problems:1. Measurements of electric parameters UOS duringultrasonic welding are carried out;2. Effect, changing properties of welded materials onparameters UOS is determine;3. Eeffect welding pressures on electric parametersUOS Is researched;4. Optimum regimes for implementation of ultrasonicwelding with the maximum effect are installed.5. Criteria of automatic determination of optimumregimes of ultrasonic welding of various materials invarious conditions are determined.REFERENCES[1] Volkov S.S., Cherniak B.J. Welding of plastic usingultrasound, Chemistry.[2] Volkov S.S., Orlov U.N., Astahova R.N. Weldingand agglutination of plastic. М., «Machinery», 1972,128 с .[3] Zaysev K.I., Matsuk L.N. Welding plastic. М.,«Machinery», 1978.[4] Holopov JU.V. Ultrasonic welding of plastic andmetals. "Mechanical engineering", 1988.[5] Khmelev V.N., Slivin A.N., Barsukov R.V.,Tsyganok S.N., Savin I.I., Shalunov A.V., LevinS.V., Abramov A.D. "Development of the New

5MEASUREMENT PARAMETERS OF ULTRASONIC OSCILLATORY SYSTEM DURING WELDINGTHERMOPLASTICSPrinciple of Batching of Energy at UltrasonicWelding and Creation of the Equipment forConnection of Thermoplastic Materials", IntrnationalWorkshops and Tutorials on Electron Devices andMaterials EDM'2006: Workshop Proceedings. -Novosibirsk: NSTU, 2006.[6] Patent the USSR №1315341 Control mode of aultrasonic welding.[7] Patent the USSR №1627413 Control mode of aultrasonic welding.[8] Patent the USSR №176381 Device for ultrasoundwelding plastic.[9] Patent the USSR №550225 Device of a proportioningof energy at a ultrasonic welding.[10] Patent the USSR №719835 Way of management ofprocess of a ultrasonic welding.[11] Patent the USSR №753664 Device for ultrasonicwelding plastic. / Cherniak B.J., Bokov V.A.,Lyashko F.E, Zvezdin G.A., Tizengauzen А.М..[12] Patent the USSR №996140 Control mode of aultrasonic welding / Kozich А.А..[13] RU, patent, 2220917 kl. В 29с 65/08. Method ofultrasound welding thermoplastic / Lyashko F.E.,Sokolova O.F.[14] RU, patent, 2229382 kl. В 29 С 65/08. Method ofultrasound welding thermoplastic / Lyashko F.E.,Sokolova O.F.[15] RU, patent, 2247544 kl. A 61 B 18/00. A mode ofsteering of process ultrasonic liposaction / KhmelevV.N., Barsukov R.V., Tsyganok S.N., Slivin A.N.,Rascals А.В.Alexey N Slivin was bornin Biysk, Russia, 1976 Hereceived degree on informationmeasuring engineering andtechnologies from Altay StateTechnical University, keyspecialist of electronics. Hismain research interest aredevelopment of high-powerelectronic generators forultrasonic technological welding.Denis S. Abramenko – postgraduated student of BTI. He isreceived engineer’s degree fromBTI AltSTU at 2005. IEEEStudent Member.Alexey D. Abramov was bornin Biysk, Russia, 1984. Postgraduated student of BTI. He isreceived engineer’s degree fromBTI AltSTU at 2006. IEEEStudent Member. His mainresearch interest are developmentof high-power electronicgenerators for ultrasonictechnological welding.