Plastic Welding Research Articles

Temperature monitoring for high frequency welding of soft biological tissues: A prospective study.

Monitoring of temperature changes and accurately determining the moment of electrode removal during open heart operations is not well recognized. We investigated the temperature fields distribution in the biological tissues affected by electrosurgery upon use of an infrared thermograph. The dynamics of temperature distribution in the tissue was registered by the thermal imaging camera FLIR i7. Measurement of the temperature between electrode couples was carried out for two operation modes: coagulation (100% power) and coagulation (50% power). The most important result of the applied method of temperature monitoring is a determination of the moment for electrodes removal that ensures the avoidance of carbonization of the cardiac tissues during their ablation. Temperature monitoring for connection of soft live biological tissues by welding allows the power to be fed in the amount sufficient for a formation of continuous ablation of the myocardium tissue.

Влияние материала и геометрической формы волноводов на процесс ультразвуковой сварки пластмасс

This article briefly describes basic elements of machines for ultrasonic welding of plastics and the main materials used for manufacturing elements of ultrasonic waveguide oscillatory systems. A relationship between the amplitude of fluctuations of the welded material and a ratio of wave resistance of the product material and the waveguide tool geometry is examined. It is shown that when welding plastic products of a large thickness, it is practical to use waveguides made from aluminum alloys with a working end face with a diameter of 15 mm. It is established that the closer the acoustic characteristics of the waveguide material and the plastic are, the fuller the transfer of ultrasonic energy is when transiting through the interface of the welded polymeric materials. To assess the distribution of amplitudes of fluctuations in the welded material it is more convenient to use a transmission ratio, which decreases with a decrease in the wave resistance. It is established that the sizes of the working end face of the waveguide are most often defined by the properties, dimensions and geometry of the welded product. The application of the developed recommendations to the choice of material and sizes of the working end face of the waveguide can increase technological reliability of the ultrasonic welding process and improve quality of products.

Corrosion Behavior of Welded Joints of X70 Pipeline Steel Produced by High-frequency Welding

Corrosion behavior of welded joints of steel pipe category X70 produced by high-frequency welding, in different conditions, in which it is possible to initiate stress-corrosion cracking, hydrogen or sulfide cracking, was investigated. According to the results of electrochemical researches, the kinetic parameters of the cathode and anode processes on the surface of the welded joint of pipe in the investigated solutions are determined. Corrosion resistance of the welded joint HFW-pipe is similar to corrosion resistance of the base metal.

Optimization on ultrasonic plastic welding systems based on two-dimensional phononic crystal

Large-sized tools are needed for plastic welding of large objects. However, the displacement distribution at the radiation surface of the tools is not uniform due to the strong lateral vibration. In this paper, two-dimensional (2D) phononic crystal (PnC) is introduced by processing periodically arranged grooves in large-sized tools. This method is different from the traditional experience-based grooving method. The lateral vibration is suppressed due to the characteristic of PnC. In this paper, six kinds of ultrasonic plastic welding systems based on 2D PnC with different groove width and height are designed. The vibration characteristics of ultrasonic plastic welding systems were simulated and experimented. The band gaps of large-sized tools are analyzed. The results show that the lateral vibration is suppressed when the operating frequency of the ultrasonic plastic welding system is within the band gap of the large tool. The displacement distribution at the radiation surface of the tools is more uniform. A theoretical support is provided for the design of large-sized ultrasonic plastic welding systems.

Experimental and clinical rationale for the gastrointestinal bleeding treatment with endoscopic high frequency welding bipolar electrocoagulation

Problem of gastrointestinal bleeding treatment remains relevant, due to the high mortality. Endoscopic haemostasis reduces both general and postoperative mortality 3 — 4 times. There are a number of methods for endoscopic haemostasis: chemical, injectable, monopolar coagulation, argon plasma coagulation, laser coagulation and clapping.The aim — to substantiate experimentally and morphologically the use of high­frequency welding bipolar electrocoagulation with the EK­300M1 apparatus in gastrointestinal bleeding endoscopic treatment and introduce it into clinical practice.Materials and methods. An experimental study of a new local haemostasis method for bleeding vessels and erosions (patent N 124885 dated 25.04.2018, A method for treating patients with gastrointestinal bleeding) with morphological verification of the state of the vessels was done with experimental study on 10 pigs aged 5 — 7 years, weighing 85 — 100 kg. For high­frequency welding bipolar coagulation, two probes were used, connected to the EK­300 M1 apparatus in the overlap mode: 2.2 mm in diameter (patent N 115147 dated 04.04.2017) with a convex electrode (N 1) and 3.2 mm (modified) with a concave electrode (N 2).Results and discussion. It has been established that to stop bleeding from vessels with a diameter of up to 1 mm, it is most effective to use probe N 1 with an exposure time of 15 s; for vessels with a diameter of more than 1 mm­ probe N 2 with an exposure time of 30 s.Conclusions. High­frequency welding bipolar electrocoagulation has advantages over other methods of endoscopic haemostasis and can be recommended as the method of choice for the gastrointestinal.

Plastic droplet welding: bond strength between plastic freeforming structures and continuous fiber-reinforced thermoplastic composites

Plastic freeforming (PF) is an additive-manufacturing process for producing three-dimensional plastic parts based on 3D CAD data by applying plastic droplets in layers. This process is used to produce customer-specific and complex geometries (prototypes and small series) on organic sheets. A comparable serial process is the injection of a second component onto organic sheets by injection molding. A sufficient bond between the PF structure and the organic sheets is of particular importance for each application. If this is not guaranteed, the composite system cannot withstand the mechanical load and fails. The force exerted on the system can no longer be transmitted between the PF structure and the organic sheet. The organic sheet is made of glass fiber-reinforced polypropylene (PP). The connection between the organic sheet and the PF structure is achieved by welding the molten polymer droplets and the surface of the organic sheet. The PF structures are made of PP to ensure sufficient compatibility with regard to the weldability of the components. The processing of PP in the PF process is a challenge because PP is a semi-crystalline material. The shrinkage of semi-crystalline materials is significantly higher compared to amorphous materials. Due to the layered structure of the components, the shrinkage of the individual layers results in undesired warpage. The adhesive strength between the organic sheet and the PF structure is investigated by determining the bending strength in the 3-point bending test. The investigations include an optimization of the process parameters to maximize the adhesive strength. The experimental investigations show that an increase of the nozzle and build chamber temperature leads to a higher adhesive strength. In further investigations, the temperature of the nozzle shows no significant influence on the surface temperature despite the expected heat radiation. The surface temperature is almost only dependent on the temperature of the build chamber.

Ultrasonic plastic welding of CF/PA6 composites to aluminium: Process and mechanical performance of welded joints

Due to environmental challenges and need for action with regard to CO2 emission, reducing the weight of vehicles has become one of the most important goals of car manufacturers in Europe. Materials like fibre-reinforced plastics and aluminium are the core of the research for lightweight design. However, efficiently joining these materials together is still a challenge. When thermoplastic composites are used, direct joining (i.e. without adhesives or fasteners) with the metal substrate can be obtained using welding technologies which melt the thermoplastic at the interface. In this study, ultrasonic plastic welding was investigated as a candidate technology for joining aluminium and carbon fibre-reinforced thermoplastics. The goal was to understand the main mechanisms involved in the welding process and how they affect the performance of the joint. Initially, the technique proved to be successful, but moderate strengths were obtained. Therefore, several surface pre-treatments of aluminium were analysed to improve the performance in terms of lap shear strength; mechanical, chemical and physical treatments were also carried out. With laser structuring, strengths comparable to adhesive bonded joints were obtained, but in a much shorter process time. Other treatments led to considerable improvements as well. The encouraging results achieved represent an important step in the development of ultrasonic plastic welding for multi-material joining in the automotive industry.

Investigations on the Interplay Between Focusing and Absorption in Absorber-Free Laser Transmission Welding of Plastics

Lab-on-a-chip devices, where small channels and reaction chambers have to be covered with a sealing lid, laser beam welding has already been proven to show considerable potential for standard material combinations. To avoid absorbing additives, the wavelength of the laser has to fit the absorption bands of the polymers. For it to achieve a localized weld seam, the laser beam has to be strongly focused. To achieve the desired temperature distribution, we establish and discuss the heat rate generated by a focused beam as a function of the absorption coefficient and the Rayleigh length. Thermal simulation of the weld process reveals the dependence of the temperature on Rayleigh length and absorption coefficient. Experiments were carried out with a tunable laser source emitting between 700 and 1000 nm on polycarbonate samples doped with Lumogen 788 dye. Microtome cuts of the welded samples reveal the dimensions of the heat-affected zone and, therefore, of the seam. Experimental and simulation results show that for typical welding conditions a localized seam inside a sample can be achieved with an appropriate focusing of the laser beam and tuning of the wavelength. The dimensions of the heat-affected zone decrease as absorption coefficient decreases and welding velocity increases. The discussion of the functional dependence of the heat rate on absorption coefficient and Rayleigh length shows that Rayleigh length and sample thickness have to be smaller than the optical penetration depth.

Modeling the interrelationship between the parameters for improving weld strength in plastic hot plate welding: A DEMATEL approach

Application of plastics is increasing day by day since plastics offer many distinct advantages as compared to metals. Plastics has mainly good thermal and electrical insulation properties, corrosion resistance, chemical inertness, and high strength to weight ratio. Additionally, these are cheaper in cost as compared to conventional materials. Plastics are additionally easy to process. Nowadays, product requirements are getting critical and thus product design is getting more complex in shape. To manufacture intricate complex shape creates complexity in manufacturing process which is sometimes very difficult or almost not feasible to produce with single manufacturing process. To manufacture such critical products, welding is a complimentary process. Type of weld joint and welding process can be selected based on the product design and load application on the product. Hot plate welding is very simple welding process as compared to other plastic welding process and most commonly used. Good quality weld is the prime objective of welding process. Weld strength is dependent on several parameters which may be process parameters as well as product parameters. The objective of this study is to identify the key parameters in hot plate welding process of the plastics using Decision Making Trial and Evaluation Laboratory which is one of the prioritization techniques. Results of the study focus on understanding the key parameters affecting the weld strength. Study shows that hot plate temperature, welding time, and melting time are the key parameters affecting the weld strength.

Numerical investigation of a double frequency approach for longitudinal HF welding of cladded pipes

This article contains findings of simulation research on longitudinal induction welding of cladded pipes with use of simultaneous double frequency. Solutions are proposed to reach the required temperature distribution at the welding edge for the cladding composite of S355 and Alloy 625 with single and simultaneous double frequency. An advanced consideration of magnetic and other material properties was performed to simulate the dominating physical effects of high frequency (HF) welding. The background of use and advantages of simultaneous double frequency are presented. In the context of the research, a correlation for welding speed, frequency and temperature distribution with industrial relevance was found for the cladded pipe welding.

Laser welding of polymers using unsymmetrical squaraine dyes

ABSTRACTTransmission laser welding of plastic is typically achieved by incorporating a laser absorbing dye into one of the two pieces of plastic one wishes to weld together and mediating the welding process using a laser emitting light at a suitable wavelength. Desirable properties of laser absorbing dyes include: (1) the dye is colorless in the visible region but absorbs strongly in the region at the wavelength where the laser emits, (2) the dye has a good conversion of the energy from the laser to heat, (3) the dye is stable enough to be incorporated into the molten plastic, (4) the dye is soluble in the plastic of choice to give an even distribution in the plastic, and (5) the dye is nontoxic. Here, we explore an alternative approach to achieve laser welding of colorless plastics using a laser dye that is colored, but that can be bleached after the welding process. Nonsymmetrical squaraine dyes were prepared by condensation of squaric acid and two equivalents of various 3,5‐dimethoxy‐N,N‐dialkylanilines. After the incorporation into polyethylene and laser welding, the plastic was bleached either by heat treatment or by irradiation with a high pressure Xe‐lamp giving colorless polyethylene. © 2018 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2018, 56, 2245–2254

Developing low temperature recovery technology of waste heat in automobile factory

AbstractThe painting operation is an important process in automobile manufacturing process, which not only consumes considerable amount of energy but also affects the environment through the flue gases emitted during the process. A case study in Taiwan was conducted on developing an innovative low‐temperature recovery technology of waste heat automobile industry. The high frequency welding segment technology was built on the site to extract heat close to an acid dew point. When the ambient temperature is changed substantially, the fins and heat pipes are solidly connected to maintain the performance of the heat exchanger. Moreover, the hot water obtained from the waste heat recovery is delivered to pretreatment heating tank the painting shop directly. By improving the energy efficiency on heat transfer, the proposed recovery technology of waste heat in automobile factory has been justified with having the performance 69% higher than conventional design. In order to reduce the effect of CO2 emission on the environmental impact, the temperature at the end of the flue gases is further decreased from 160°C to 110°C. The cost benefit analysis reveals that the payback year is 2.8 years. The innovative heat recovery technology contributes to energy conservation and environmental sustainability.

Analysis of short wavelength infrared radiation during laser welding of plastics

In this paper, a new measurement system and a new approach in calculation for infrared (IR) radiation investigation in quasi-simultaneous transmission laser welding of plastics are presented. The measurement system is based on a MW/SWIR (medium-wave/short-wave IR) camera and optical filters narrowing the spectral region to SWIR. The measured signals contain radiation from the melted zone in between the semitransparent and absorbing polymers, as well as radiation from the surface and interior of the semitransparent polymer. The new calculation approach was developed to distinguish between these signals. It is based on simplification of the process to two places with two temperatures (surface and molten interface) and knowledge of the spectral optical properties of the material, filters, and camera response. The results of measurement and calculation for three different optical filters and polyoxymethylene samples with two thicknesses are shown and discussed. Good agreement is obtained for the calculation variant using normal transmissivity of the semitransparent polymer.

Ultrasonic Welding of Dissimilar Plastics

The ultrasonic welding of dissimilar plastics is considered. This process depends on the diffusion of molecules to the surface of polymers at temperatures corresponding to the viscoplastic state. The weldability of a pair of dissimilar plastics depends on the compatibility of their acoustic properties, assessed in terms of the density and viscosity of the melts.

Electric Pulse Component Effect on the Stress State of AMg6 Aluminum Alloy Welded Joints Under Electrodynamic Treatment

The residual welding stresses deteriorate the welded joint lifetime, and they are the chief cause of brittle metal fracture, i.e., corrosion cracking. The development of efficient methods to reduce the welding stresses, which are noteworthy for low energy costs and ease of realization, is customary important for the modern welding production. One such method is the electrodynamic treatment (EDT) based on the electric current pulse passing through the welded joints at the instant of dynamic load application to it. In the optimization of the parameters it is appropriate to test the pulse electric current effect on the residual welding stresses. The procedure of investigation of the EDT electric pulse component effect on the stress state of AMg6 aluminum alloy welded joints is proposed. It is established that the electric current pulse passing through the welded joint metal enhances the EDT efficiency in reduction of residual welding stresses. It is shown that the electrodynamic effect initiates the plastic tensile strains in metal, their interaction with the plastic welding compressive strains reduces residual stresses in the welded joint. Here the electric current pulses passing increases the peak values of the plastic tensile strains, which results in the more efficient electrodynamic effect on the residual welding stresses decrease in AMg6 alloy. The results lend credence to the physical model describing the electroplastic effect on the welding joints’ stress state.

Design, manufacturing, and structural optimization of a composite float using particle swarm optimization and genetic algorithm

In the realm of laboratory experiments dealing with solutions, float is a dynamic part of the testing device to help monitor and measure the level change of the solution, which has a significant influence on the reliability of the data recorded. Thus, the material selection, design, and structural configuration of the float need to be optimized based on the test exposure conditions, temperature, test requirements, and setup limitations, while maintaining the manufacturing to be simple and cost-effective. In the present study, a composite float design, manufacturing, and optimization have been undertaken based on the performance constraints and setup requirements. For this purpose, readily available composites were taken into account in terms of density, temperature resistance, and alkali resistance, resulting in two design alternatives such as polyvinyl chloride and low-density polyethylene. Then, the structural configurations were considered and a performance-based design was implemented. In order to minimize the length of the composite float to make it fit well into the test setup, the design problem was formulated into a constrained optimization problem with four design scenarios and optimization was conducted using genetic algorithm and particle swarm optimization. The results obtained showed that the solutions of genetic algorithm and particle swarm optimization were comparable; however, those of particle swarm optimization proved to be more accurate in case of more complex design scenario, and also faster by two to three times. The manufacturing was conducted through plastic welding and heat shrink tubing and final assembly of linear variable differential transformer and steel weight. It was found that the composite float has a pretty sensitive and accurate performance and can reliably fit and be used in the experimental setup.

Safety analysis of endoscopic haemostasis using a high-frequency live tissue electric welding device - EKVZ300 PATONMED.

IntroductionThe method of a bipolar high-frequency welding (HFEW) of soft living tissues of animals and humans has been used in various areas of surgery. However, it has not been utilized in endoscopic gastrointestinal procedures yet. HFEW has strong potential to be used in gastrointestinal endoscopic procedures due to the competitive cost of generator devices and due to its proven ability to coagulate vessels of wide diameter as compared to standard electrocautery devices.AimTo investigate the effectiveness of the endoscopic haemostasis using HFEW generator device – 300 PATONMED – in a porcine model of arterial gastrointestinal bleeding.Material and methodsA porcine model of arterial gastrointestinal bleeding was created. A 300 PATONMED set to the “welding” regime and a flexible 7 Fr bipolar coagulation probe with two electrodes on the tip fashioned spirally attached to convey energy were tested. Once bleeding from the artery had been initiated, the bipolar probe was applied to coagulate the bleeding site. Animals were observed for clinical evidence of recurrent bleeding and subsequently were euthanised for histological examination.ResultsA total of 10 experiments were successfully completed. An optimal haemostatic effect was achieved with durations of cautery of five to eight seconds in all animals. Continuous observation after haemostasis revealed no evidence of re-bleeding. No systemic side-effects of the technique were observed. Histological examination has shown that the peripheral thermal injury area that surrounded the coagulation zone did not spread beyond the mucosal layer in depth and 2 mm in width.ConclusionsThis animal study provided evidence for the safety of an HFEW in the treatment of gastrointestinal bleeding. The advantages of this technology are smokeless operative area, no tissue overheating, minimal necrosis and damage to surrounding gastric tissue, and the fact that the area of HFEW is confined to the area of the electrodes.

Numerical modelling of industrial scale high frequency welding of cladded pipes

The aim of this work is to develop a model to simulate the high frequency (HF) welding process for cladded pipes and to find process parameters to solve the inconvenient power proportion between the cladding layers. A 2D model of HF pipe or profile welding was created. This model considers the most important parameters of the longitudinal HF-welding process of thin walled cladded pipes. Effects of welding speed, current frequency and material properties have been examined. The material combination of the metal sheets contains S235 as the carrier material and the corrosion resistant alloy 625 for the inner tube cladding. The results have been compared to an available experiment and to gain the basic validation of the model. An approach is proposed to facilitate high frequency welding of cladded pipes under consideration of industrial requirements for a chosen material combination.

Numerical modelling of industrial scale high frequency welding of cladded pipes

The aim of this work is to develop a model to simulate the high frequency (HF) welding process for cladded pipes and to find process parameters to solve the inconvenient power proportion between the cladding layers. A 2D model of HF pipe or profile welding was created. This model considers the most important parameters of the longitudinal HF-welding process of thin walled cladded pipes. Effects of welding speed, current frequency and material properties have been examined. The material combination of the metal sheets contains S235 as the carrier material and the corrosion resistant alloy 625 for the inner tube cladding. The results have been compared to an available experiment and to gain the basic validation of the model. An approach is proposed to facilitate high frequency welding of cladded pipes under consideration of industrial requirements for a chosen material combination.

Suppression of lateral vibration in rectangular ultrasonic plastic welding tool based on phononic crystal structure

Ultrasonic welding is one of the main applications of high-power ultrasound and is used in the automotive industry and aerospace. Transducers and tool are important parts of the ultrasonic welding system. Different tools are required for different welding objects. For larger plastic welded parts, it is necessary to weld them with large-sized welding tools. Due to the large size of the welding tool, under the excitation of the transducer, the tool will produce a coupling effect of longitudinal vibration and lateral vibration. Lateral vibration will cause the radiation surface of the tool to be non-uniformly displaced, and the working efficiency and welding results of the welding system will also be affected. So, in this paper, the phononic crystal bandgap theory and coupling vibration theory are used to study the coupled vibration of large-sized rectangular plastic ultrasonic welding tools. In order to improve the work efficiency and radiation surface's displacement uniformity of the tool, the phononic crystal structure is used to suppress the lateral vibration of the large-sized plastic ultrasonic welding tool, and the lateral vibration band gap of the phononic crystal structure is calculated. The longitudinal resonance frequency of the system is designed in the band gap range of the lateral vibration of the tool. So the lateral vibration of the tool can be effectively suppressed. The longitudinal vibration displacements on the radiation surface of the rectangular tool before and after vibration suppression are analyzed and compared with each other. The vibration mode of the ultrasonic welding system is simulated by the Comsol Multiphysics finite element software. The large-scaled tool with phononic crystal structure has a radiation surface displacement compared with the tool without phononic crystal structure, and the results show that the radiation surface displacement with phononic crystal structure will increase and tend to be uniform, greatly optimize the welding effect, improve the working efficiency of the welding system, and meet the needs of practical engineering. It is concluded that the longitudinal resonance frequency of the ultrasonic plastic welding system within the lateral vibration bandgap on the phononic crystal structure can not only suppress the lateral vibration, but also make the longitudinal displacement of the radiation surface more uniform and larger. Therefore, the work efficiency is greatly improved.