Showing papers on "Electric resistance welding published in 1995"

Method of production of workpieces by welding equipment

Abstract: Starting on the surface of a foundation body (2) weld material is applied in runs to form layers by an equipment for profiling building-up welding and hence a workpiece (1) is manufactured, where the foundation body (2) may be a component of the workpiece (1). The course of runs to form layers as well as the approximate rate of application of weld material are calculated by a computer system (11), starting from a two- or three-dimensional data model of the workpiece (1) in the form of software, and given over to the system control (10) which positions the welding torch (7) by means of the robot (5) and the workpiece (1) located on a turntable (4) by a clamping mechanism (3) with respect to one another, and regulates the rate of application of weld material applied by the welding apparatus (8) in such a way that the liquid weld material adheres to the layer lying underneath without running down and irregularities in the runs to form layers are levelled out. Hence metal workpieces having manifold bodily shapes and theoretically of any size and having any thickness of wall, even consisting of different metallic materials, may be manufactured by profiling building-up welding without auxiliary cores or other devices supporting the liquid weld material.

Computer simulation of resistance spot welding in aluminum: Part 1

Abstract: A computer-based model of resistance spot welding with hemispherical electrode tips has been developed to include simulation of elastic-plastic mechanical deformation as well as ohmic heating and thermal conduction. The primary effect of the mechanical deformation is in its influence on the contact read and current density developed at the faying surface. The model was used to simulate spot welding in aluminum alloys. Preliminary results show the effects of variations in input current, contact resistance, applied force and position of the cooling water with respect to the electrode tip. It is shown that the value of the contact resistance has a large effect on nugget formation in the spot welding of aluminum alloys and that the applied force has a significant effect arising from its effect on the area of contact at the faying surface. The formation of a resistance spot weld in aluminum is also sensitive to the position of the cooling water-electrode interface because of the high thermal conductivity of aluminum alloys.

Control equipment for resistance welding machine

Abstract: A control equipment for a resistance welding machine for welding a material by the Joule's heat generated in the material by applying an electric power to the material, including an inverter (7) for converting a DC voltage to an AC voltage by pulse width modulation control (16), a transformer (8) having a primary winding to which the AC voltage is applied and having a secondary winding which supplies an AC current to the material, and a control unit for generating an AC current reference with a rectangular waveform of a specified frequency, comparing the AC current reference with an output current of the inverter to obtain an error, and for PWM controlling the inverter so that the error becomes zero.

Laser welding with filler wire

Abstract: New applications such as welding of material combinations and the ability to fill opening gaps between the workpieces offer new prospects for laser beam welding processes with filler wire. To guarantee good quality, vertical distance variations between wire tip and weld pool are, above all, not permissible as this causes globular metal transfer and would accordingly result in strongly rippled, unclean welds. A process-internal signal, recorded by a sensor, helps to solve this problem. The automatic tracking of the vertical wire position is possible on-line via a controller. In this way, the running process can be optimized and a consistently good weld quality can be achieved.

An intelligent control system for resistance spot welding using a neural network and fuzzy logic

Abstract: An intelligent control system based on fuzzy logic able to compensate for variations and errors during automatic resistance spot welding (RSW) and produce consistent sound welds was developed. A fuzzy logic control (FLC) scheme was employed to overcome the lack of a precise mathematical model of the process. Electrode displacement, indicative of weld nugget growth, was used as the feedback signal to create appropriate actions to adjust power delivered to welds in real time. Control action is generated from a rule-based system constructed from experimental data for welds made under a wide variety of conditions. A neural network (NN) was constructed to provide process input-output relationships and tune the fuzzy rules off line. The FLC system was evaluated using the NN to describe electrode displacement as a function of percentage maximum heat input and welding time. Results showed the suitability of applying this control scheme to deal with the uncertainties of RSW in a typical automated production environment.

Hybrid laser and arc process for welding workpieces

Abstract: A welding process in which laser radiation is trained on the seam area fod between two sheet-metal workpieces, one of which has an edge projecting above the other In addition, the arc is guided along this edge to melt the edge and contribute molten metal to the pool formed by the laser

MAG arc welding apparatus

Abstract: An MAG arc welding method and apparatus is capable of achieving a welding bead in a regular ripple pattern or in a suitable sectional form The welding power source generates the first welding current I1 and a second welding current I2 larger than the first welding current The wire melting speed is changed by switching between the first and the second welding currents The welding method or apparatus according to the invention generates the first arc length more than 2 mm and the second arc length more than the first arc length and switches between both arc length at a switching frequency F of 05 to 25 Hz The ratio of the second to the first welding currents is made to be in 103 to 120 In addition to a welding method to change the arc length by switching the first and the second welding currents at a constant wire feeding rate, the present welding method makes it possible to carry out the lap welding or butt welding even when there is a large gap The large gap requires a large amount of molten metal which is prepared by increasing the wire melting speed caused by an increase in the wire feeding rate by 5 to 20% The resultant reinforcement has a beautiful appearance

Industrial workcell system and method

Abstract: An industrial resistance welding workcell includes a robot controller and robot, a welding control, and an overall workcell control in a form of a programmable logic controller and electronically-controlled electrically-actuator assembly is coupled to the wrist of a robot arm, which is further coupled to a conventional welding gun. The actuator assembly is controlled by an actuator control to vary the tip separation distance to any one of a virtually infinite number of separation distances, and further, is adapted to control a clamping force with a high degree of accuracy. The workcell further includes a tool used to secure a workpiece or workpieces. The tools characterized by use of an electronically-controlled electrically-actuated clamp for securing the position of the workpiece or workpieces relative to the base of the tool. Use of electrically-actuated clamps, and actuator assembly for the weld gun eliminates the need for use of plant-provided facilities, particularly compressed air and the dense packs, surge tanks, and air cylinders associated therewith as used in conventional resistance welding workcells. Furthermore, the workcell has associated therewith a self-contained closed loop cooling system, mounted under the robot base, that substantially eliminates the host of feed and return cooling hoses that are commonly found on conventional resistance well workcells. The all-electric workcell significantly reduces workcell down time, and material and labor cost, while improving overall system performance.

Apparatus for automatically replacing welding electrodes

Abstract: A double extractor and an electrode supply station are provided for automatically replacing electrodes in opposing jaws of a resistance welding machine. With coated sheet steels now used for car body structures, it is found that electrodes must be replaced more often. The automatic replacement system is programmed to replace electrodes when the welding machine is idle such as between the movement of car bodies or other structures moving on a conveyor. A double extractor has a first position for extracting top electrodes and a second position for extracting bottom electrodes. Both positions have a plurality of gripping fingers operated by a cam, which simultaneously twist and pull-off the electrodes from the jaw. After the jaw has been removed, the gripping fingers release the old electrode.

Reinforced susceptor for induction or resistance welding of thermoplastic composites

Abstract: A fiber reinforcement fabric contains a metal susceptor strip paired with each warp thread and woven with the weave thread to produce a thermoplastic welding susceptor of separated and electrically isolated, longitudinal metal strips and fiber reinforcement in the weld.

Method of welding a carbon steel and an austenitic stainless steel together and resultant structure

Abstract: Method of welding a carbon steel and a austenitic stainless steel involves using high density energy beam like a laser beam or electron beam Welding using high density energy beam is effective to obtain a high precision welding For the purpose of obtaining both high precision and no cracks, and no deformation, the method of the invention controls the structure of a weld portion to be a mixed structure of an austenitic structure and not greater than 20 wt % of a ferritic structure

Process for producing steel pipe excellent in corrosion resistance and weldability

Abstract: A process for producing a steel pipe excellent in corrosion resistance even in an atmosphere containing wet carbon dioxide and trace hydrogen sulfide and also excellent in weldability at a reduced cost and an enhanced productivity. The process comprises heating to 1,050-1,300 °C a billet containing, on the weight basis, 0.01 to less than 1.2 % of Si, 0.02-3.0 % of Mn, 7.5-14.0 % of Cr, 0.5-0.005 % of Al, a reduced amount of each of C, N, P and S, at least one of Cu, Ni, Co, Mo and W, and the balance consisting of Fe and inevitable impurities and having an MC value of at least 0, finishing hot rolling in the austenitic single-phase temperature region, winding up the rolled steel as a hot coil with a thickness of 3.0-25.4 mm, cooling the coil to at least 500 °C in a cooling rate of at least 0.01 °C/sec to give a steel substantially comprising martensite, reheating the steel to a temperature in the range of from 550 °C to the Ac1 transformation point, holding at that temperature for at least 15 min, cooling to an ordinary temperature, cutting in a given width, and continuously shaping in a cylindrical form while conducting resistance welding of both ends of the strip into a pipe.

Recent developments of ultrasonic welding

Abstract: New ultrasonic welding methods of metal and plastic materials have been proposed by the author and their effectiveness shown. For welding of thick and large metal specimens: (1) ultrasonic butt welding methods joining thick metal specimens end to end are proposed. Large capacity vibration sources and solid state power amplifiers of 50, 100 kW were developed; (2) a welding method using two vibration systems crossed at a right angle is effective, and 10 mm thick aluminum plates were joined successfully. For medium size metal welding specimens; (3) complex vibration welding tips were shown to be very effective, and one-dimensional complex vibration systems are developed to simplify the systems. For welding of small metal specimens; (4) higher vibration frequency and a complex vibration wire bonding system are proposed, and it is shown that they are significantly effective. The bonding systems of 60 to 780 kHz were designed and the required vibration amplitude and velocity obtained for thin aluminum wire using the 40 to 780 kHz bonding systems. For welding of plastic materials; (5) high frequency, complex vibration and two-vibration-system welding methods are effective.

Apparatus for nondestructive on-line inspection of electric resistance welding states and a method thereof

Abstract: Apparatus for inspecting an electric resistance welding state including a first electrode connected to a power source, a second electrode connected to another terminal of the power source, and a welding object interposed between the first and the second electrodes. A voltage waveform measuring system includes a first analog-to-digital converter for detecting voltage applied, during a welding process, to both ends of the welding object. An electrode movement measuring system includes a sensor for detecting a change of a gap between the first and the second electrodes during the welding process, and a second analog-to-digital converter for receiving an output of the sensor. A computer system which includes a neural network inspection system for receiving outputs from the voltage waveform measuring system and from the electrode movement measuring system is provided.

Welding method for the connection of a component to a workpiece, and a device for carrying out the method

Abstract: In a welding method for the connection of a component (6) to a workpiece (7) by means of an arc between the component end and a welding point on the workpiece (7), the arc voltage is set and is monitored continuously during the welding process. The component lift is in each case automatically adjusted accordingly.

Electric wire connecting method

Abstract: PROBLEM TO BE SOLVED: To establish an electric wire connecting method which can give a stable, small contacting resistance and a sufficient bonding strength to the connecting part between a terminal and an electric wire. SOLUTION: The core (soft copper wire) of a wire harness is exposed by stripping the insulative covering at the foremost part of an insulated electric wire to constitute the harness. A band-shaped brazing material 20 is inserted between the core 11 and the connection part 31 of a terminal (copper alloy) 30, and these parts 11 and 31 are pinched by pressure in the electrode 41 of a resistance welding machine 40 followed by current feeding, and now the band- shaped brazing material 20 will quickly be melted by the resistance heating to establish strong connection of the core 11 with the terminal 30 through the brazing material 20.

Ultrasonic welding of metallized plastic

Abstract: A method for ultrasonically welding two plastic parts together One part (30) has a weld joint feature (23) that is covered with a metal layer (27), and the other plastic part (25) has a complimentary weld joint feature The two parts are joined together by ultrasonically welding the two weld joint features to each other A force (40) is applied to the first and second plastic parts prior to the step of welding The force is substantially in excess of that required to cause the two weld joint features to contact each other This method creates an ultrasonic welded metallized plastic assembly Each part of the assembly has a weld joint feature, at least one of which was covered with a metal layer prior to welding Portions of the each of the two weld joint features are deformed to form a plastic weld joint through the metal coating

Explosive welding: principles and potentials

Abstract: Explosive welding is a solid-state process in which controlled explosive detonations force two or more metals together at high pressures. The resultant composite system is joined with a high-quality metallurgical bond. Explosive welding (or explosive bonding) is a high-pressure process in which contaminant surface films are plastically jetted off the base metals as a result of the collision of two metals. The time duration involved in the explosive welding event is so short that the reaction zone (or heat affected zone) between the constituent metals is microscopic. During the process, the first few atomic layers of each metal become plasma because of the high velocity of the impact (200 to 500 m/s, 660 to 1,640 ft/s.) The angle of collision causes the plasma to jet in front of the collision point, effectively scrub-cleaning both surfaces, and leaving clean metal behind.

Method for controlling resistance welding using fuzzy reasoning.

Abstract: A method for controlling resistance welding adaptively optimizes a set value of welding current for the next welding operation by inference from monitored signals of the present welding operation. In an embodiment, a welding current I and a change of resistance ΔR across welding electrodes are measured during a welding operation. The number of welding operations N involving the welding electrodes is incremented. After the present welding operation, these values of ΔR, I and N are mapped into compatibility degrees of respective antecedent membership functions. Compatibility degree of conclusion membership function of each control rule is computed from its antecedent membership function compatibility degrees. Then compatibility degree of conclusion membership functions U, S and D is composed. From the composed compatibility degree, an operation value i.e., percent change of set welding current is computed by the center of gravity defuzzification method. Finally, using the percent change, the set value of welding current is corrected. The corrected set welding current is used for the next welding operation.

Method and apparatus for controlling resistance welding

Abstract: A control apparatus for resistance welding includes a time measuring device for measuring an energization time of a welding current, the energization time being required by a given electrode displacement during welding between an electrical conductive weld member and a member to be welded which are arranged between two electrodes. A time difference calculating device is operative for calculating a time difference between the energization time measured by the time measuring device and a preset target energization time. A feedback control device is operative for correctively increasing and decreasing a welding current, which occurs at a next weld timing, on the basis of the time difference calculated by the time difference calculating device.

Theoretical investigation of penetration characteristics in gas metal-arc welding using finite element method

Abstract: In the modeling of the gas metal-arc (GMA) welding process, heat inputs to the workpiece by the arc and the metal transfers have been considered separately. The heat energy delivered due to the metal transfer has been approximated in the form of a cylindrical volumetric heat source, whose dimensions of the radius and the height are dependent on the molten metal droplet characteristics. The pinch instability theory (PIT) and the static force balance theory (SFBT) of drop detachment have independently been used to obtain the expressions for various characteristics of the drop,i.e., the drop radius, the drop velocity, and the drop frequency at various welding parameters. The occurrence or the nonoccurrence of finger penetration, routinely found in the GMA welding at high welding currents, has been satisfactorily explained by the cylindrical heat source model. The effect of various welding parameters,e.g., the welding current, the wire radiusetc., on the weld bead penetration characteristics has been investigated. In this modeling effort, the heat conduction equation has been solved in three dimensions.

Method of resistance welding thin elements

Abstract: A battery pack (30) is assembled with a flexible circuit board (38), a first tab (40), and a second tab (42). The flexible circuit board (38) has an exposed area of isolated conductor (46) which is located directly under the intersection of the first tab (40) and the second tab (42), a point where the two are resistance welded together (44). When a weld current is applied at this point (44), the isolated conductor area (46) acts as a current sink such that current flows primarily through the second (lower) tab (42). This method allows both tabs or elements to be of the same or similar thickness and electrical properties, and facilitates automated battery pack assembly.

Method of welding weld studs to a workpiece

Abstract: The invention relates to a method of welding weld studs to a workpiece, in particular of aluminum in each case, by the stroke ignition method, in which the stroke height(s) of the weld stud (1) is altered as a function of the measured arc voltage and optionally of the arc firing time. In particular, the stroke height(s) of the stud (1) can be increased during the occurrence of short circuits, i.e. during a sudden drop in the arc voltage, preferably in predetermined steps. The weld stud is immersed into a pool of melt after a predetermined period of time of between 5 and 10 ms after the welding current has been switched off. The polarity of the stud or of the workpiece is changed at least once during the welding process. The welding current is interrupted for a predetermined period of time for this purpose. The method leads to an improved, readily reproducible quality of weld.

Process and device for cooling the area of a weld during laser welding

Abstract: A process and device are disclosed for cooling the area of a weld when laser welding metal sheets or metal strips, in particular for building car bodies in the automobile industry. The invention shows how to supply coolant and to create an inert gas veil between the focus and the liquid coolant so that the liquid coolant may not reach the area of the weld and negatively affect it.