Showing papers on "Spot welding published in 1985"

A Microprocessor-Based Electrode Movement Controller for Spot Weld Quality Assurance

Abstract: Quality assurance has been of a great concern in the process of resistance spot welding, since considerable variation in the weld quality often arises even when the machine variables are held constant. In this paper a new microprocessor-based control method is developed to obtain uniform weld quality regardless of the changing welding environments. The control system utilizes a proportional (P) control algorithm, incorporating with the electrode movement as a feedback variable. The controller generates the welding control current so as to track a desired trace of the electrode movement (reference electrode movement curve) throughout weld cycle. A series of experiments was performed to evaluate the performance of this control method. The results show that, as a result of the electrode movement tracking, weld strengths of all the weldments approach to a desired strength level.

Ultrasonic spot welding tip assembly and method for using the same

Abstract: An ultrasonic welding tip assembly and associated method of use are described. The welding tips of the assembly may be conical with the cone height A and base width B having a ratio of A/B=1.2 or frusto-conical with a ratio of 0.76 in preferred embodiments. The welding tips are supported on anvils. In the welding process, the tips are only partially inserted into the material being welded so that the anvils remain spaced from the material. This space provides a reservoir into which molten material may flow away from the regions of the welding tips.

Welding tip removal tool

Abstract: A welding tip removal tool for use on spot welding machines as are presently used in the industry. The tool can remove multiple size welding tips by engagement with different dimensioned inclined surfaces multiply positioned within the same tool.

Method and apparatus for welding thin metal sheets

Abstract: There is described a method for welding thin metal sheets (A, B) by the localized heating of limited juxtaposed zones of the metal sheets to be welded to cause their fusion and to form spot welds (S). In each weld zone, the metal sheets (A, B) are heated and fused along a closed line so that each weld spot (S) has a substantially annular configuration in cross section in a plane parallel to the metal sheets. This welding may be achieved for example with the use of a laser (2) produced by a laser source (1), or by electrical resistance welding with a pair of opposed electrodes (6, 7) the ends whereof which are intended to grip the metal sheets (A, B) are suitably shaped.

Deep penetration laser welding of sheet metal

Abstract: A sheet metal welding process is described in which limited zones of contact of metal sheets (A, B) are heated locally by a power laser so as to cause fusion in the manner of spot or seam welds (P, C). Such spot or seam welds are achieved by deep penetration welding of juxtaposed metal sheets joined by a plurality of welding spots or seams, these may be spaced apart such that the sheet metal portions between the spots or seams can deform in an elastic-plastic manner under stress.

Microprocessor-based resistance welding monitor

Abstract: The paper deals with a monitoring system for in-process evaluation of resistance spot welds. The system computes the dynamic resistance characteristics (DRC) of the production weld and compares it with the DRC of a reference weld. The result of the comparison is presented as "accept" or "reject".

Preheat time compensating weld control

Abstract: A spot weld controller includes a current transformer, a current amplitude detector, a keypad data entry, a solenoid, an air valve and pneumatic cylinder, welding electrodes, a connection to an electric power supply, a source of pressurized air, and programmed logic that controls the sequential operation of the equipment. The controller performs a weld cycle that includes a preheat period, during which inorganic material that bonds metal laminas together is heated and forced away from the electrodes, and a weld period, during which electric current at welding amplitude produces the weld after the metal lamina contact one another.

Method of making a pressure vessel

Abstract: In making a pressure vessel, spaced electrically conducting plates are separated by a pattern of electrically conducting tensile members which are held in that pattern by separable electrically conducting casing halves made of material which will not spot weld to the plates, the plates are forcibly engaged against the opposite ends of the tensile members and opposite ends of the casing halves while welding current is passed through and between the plates, and then the casing halves are removed whereafter marginal edges of the plates are joined by welding.

An apparatus for profiling the ends of the electrodes of a spot welding device, as well as a device for spot welding

Abstract: An apparatus for profiling the ends of the electrodes of a spot welding device, comprising cutting members (15, 16) rotatably supported in a housing for machining the end profiles of the electrodes, said cutting members (15, 16) being coupled to a drive motor (11) by means of a transmission mechanism.

Electron emission and plasma formation during laser beam welding

Abstract: A 400 watt average power Nd-YAG laser (1.06 micrometer wavelength) was used to study the effects of plasma generation on welding. Laser spot welds on aluminum and stainless steel were monitored optically, acoustically and electrically. Results show that the laser is optically coupled to the workpiece, significant current is emitted by the workpiece, current can be detected from the plasma, optical radiation emitted by the plasma is useful for monitoring purposes, and plasma generation can be monitored using microphones. The plasmas propagate as laser supported combustion waves and are expected to contribute significantly to heat input during welding.

Amorphous metal ribbon fabrication

Abstract: A method is disclosed for the welding of two or more glassy metallic ribbons into a monolithic or composite glassy metallic body. The method includes the step of drawing the ribbons in converging fashion through a nip between two high speed rotating rollers. A heat source is generated with a series of laser beams focused at spaced intervals along the nip between the converging and contacting ribbon surfaces prior to compressing the ribbons together. The welded body is internally cooled at a rate sufficient to retain the ribbons and the weld zone therebetween in a glassy metallic state following welding. The parameters of temperature, ribbon speed, exposure time, laser beam power and ribbon thickness for the process are disclosed. In the preferred embodiment, full width welding in a narrow rectangular area adjacent the line of convergence is generated to provide a monolithic body; whereas, in an alternative embodiment strip/spot welding is provided between the ribbons.

Monitoring device for electrical welding processes, especially electric resistance spot welding

Abstract: 1. An apparatus for monitoring electric resistance welding operations, particularly electric resistance spot welding operations, by a detection of the changes of parameters, namely, current and/or voltage, in dependence on time, comprising detectors (11 to 14) for detecting the instantaneous values of the parameters and a microprocessor (15) which from the instantaneous values of the parameters, which instantaneous values have been converted by at least one A/D converter, derives the changes of said parameters in dependence on time and in dependence on the degree of agreement of said change with a desired value generates control signals for indicating and/or control means (29-34), characterized in that the microprocessor (15) is connected to a memory (27), which is adapted to store a multiplicity of individual data, each of which corresponds to an instantaneous voltage or current value and/or to an instantaneous resistance value derived from said two values during a desired progress of a welding operation, and during a welding operation the microprocessor (15) samples at a predetermined cycle frequency a multiplicity of instantaneous actual values via the A/D converter (21) from peak value-detectors (11 to 14) for the parameters, which detectors are resettable by the microprocessor, the microprocessor associates the actual value data with the stored data which corresponds to a desired progress of the welding operation and compares said actual and stored data in a comparator stage and in dependence on the degree of agreement generates the control signals for the indicating and/or control means (29 to 34).

A Theoretical Model for the Dynamic Resistance in Resistance Spot Welds

Abstract: Although the behaviour of dynamic resistance has been reported to give a good indication of weld quality for the process of resistance spot welding, this resistance variable has not been widely used for the purpose of a feedback controller design as well as for the determination of a good welding condition required for a specified weld material. This is mainly due to the fact that no analytical method is at present available to describe the behaviour of the variable. This paper presents an analytical model that can predict the variation of the resistance. In this model the complicated phenomenon of the thermo-electric interaction at the interface is included to obtain both the voltage and temperature distributions in the weldment. The computed dynamic resistance based upon this model is compared with that experimentally obtained for the case of welding of mild steel. The comparison of results shows that this numerical analysis enables the behaviour of the dynamic resistance to be predicted fairly accurately.

Assembling structure of laminated yoke

Abstract: PURPOSE:To improve the reliability of the strength by spot welding laminated thin steel plates of a laminated yoke which is clamped with thin steel plates in a rotational shaft direction in laminating direction, thereby preventing the slip between the laminated plates. CONSTITUTION:Before a laminated steel plates 1' are intergrally coupled, the adjacent laminated steel plates are intergrated by a spot welding S and laminated by inserting a bolt through a bolt hole 2 as the conventional manner. The laminated steel plates are spot welded in the state pressed in the laminating direction, and spot welded in the normal state that a gap is corrected upon initial waving of the laminated steel plates, outer bending of and varying of the thickness of the plates occurred at the working time. Thus, the slip between the laminated plates can be prevented, thereby obtaining a yoke having high reliability in strength.

Non-destructive quality-testing of a joint between sheets made by electric spot welding

Abstract: A method is described for the non-destructive testing of a joint obtained by the electrical spot-welding of two sheets of substantially the same material joined together in a local zone with the formation of a weld core which has a thermal diffusivity substantially different from the thermal diffusivity of the material of the two sheets before welding, such a core being obtained only when the welding is of a good quality. The testing is effected by a device the main characteristic of which is an electrode which delivers heat and a detector electrode located at two conveniently chosen points on one surface or opposite surfaces of the two welded sheets. The detector electrode is connected through an amplifier and an analog-digital converter to a computer which processes the signal to provide an indication of the weld quality on the basis of the measured value of the thermal diffusivity.

Weld resistance measuring apparatus for a spot welder

Abstract: Apparatus provides for measuring weld resistance of each of a group of weld sites that are subject to variation with respect to weld resistance. The apparatus includes circuitry for inducing a flow of alternating current in a weld site. The magnitude of the induced alternating current is substantially constant; in particular, the percentage variation in its magnitude is substantially less than the percentage variation in resistance to which the weld sites are subject. The apparatus further includes voltage responsive circuitry for producing a signal representative of the magnitude of the resistance of the weld site.

Device for controlling electrical resistance welding apparatus, particularly for controlling apparatus for welding parts of motor vehicles bodies

Abstract: In electrical resistance welding apparatus comprising two welding electrodes connected through respective supply cables to an electrical power supply which can generate welding current with selectively-variable effective values, a control device is provided which, in use of the apparatus, measures the resistance between the electrodes clamped on the pieces which are being welded and the resistance between the ends of the supply cables. During welding, the device detects the change in the resistance between the electrodes with time and, on the basis of a linear combination of several parameters of the resistance curve detected, establishes whether the spot weld effected should be considered acceptable or unacceptable. In the latter case, the control device causes the welding operation to be continued with a current having a higher, rms value so as to correct the spot weld made. A statistical analysis is carried out on the spots considered acceptable so as to effect, in dependence on the results of this analysis, gradual increases in the duration of the activation intervals (welding angle) of the electrical power supply so as to compensate for the attrition of the electrodes. A gradual increase in the duration of the activation intervals of the electrical power supply is also effected upon an increase in the resistance detected between the ends of the supply cables in order to compensate for the wear of the cables themselves. Once the possibility of correction has been exhausted, the device indicates to the exterior the need to replace the electrodes and/or the supply cables.

Method and apparatus producing drawn copper wire from an electrical seam welder

Abstract: The copper wires employed for electrical resistance seam welding of tinned sheet metal with the help of wire electrodes until now had to be taken back to the smelter as old metal after a few applications. The additional operating costs associated with this were until now unavoidable for long seam resistance welding of tinned sheet metal since multiple uses or applications of the copper wire for resistance seam welding have proven to be impossible in spite of years of research. The problem of these additional operating costs can be solved such that new copper wires with a reduced diameter can be directly drawn from the copper wire employed as wire electrodes for resistance seam welding after their use in welding. These wires then, for example, can be used as signal conductors or as windings. The properties of these wires are totally in accord with copper wires that are directly drawn from new copper. By this process, the additional operating costs mentioned above are substantially reduced and in many cases are even totally eliminated.

Resistance spot welding control that automatically selects the welding schedule for different types of steel

Abstract: A new principle has been employed in an adaptive control for spot welding of unknown types of steel. The dynamics of the process is monitored, not materials properties or energy input etc. The rate of rise of the temperature, as reflected in the rate of the resistance, provides all the necessary information. The control algorithm and a series of evaluative tests are described. Any conventional welding machine equipped with the new control will make sound welds the very first time, in HS or LC steel of two or multiple thicknesses, with electrode diameters as different as 2:1, and in the presence of shunting. A "teaching mode" is not required.

Electrode tip for spot welding

Abstract: PURPOSE:To provide a titled electrode tip which extends the electrode life during spot welding of a galvanized steel sheet in particular by incorporating titanium oxide into a copper-base electrode thereby suppressing positively softening of the tip and the decrease in current density and making the surface alloy layer uniform. CONSTITUTION:Fine particles of titanium oxide TiO2 are dispersed and incorporated into a copper-based electrode. The hardness of the tip is increased and the softening thereof is prevented by TiO2 and the decrease in current density is suppressed by the fine distribution. The surface alloy layer formed with the material to be welded is made uniform and the local wear of the electrode is prevented as far as possible. The electrode life is thus extended even in spot welding of particularly a galvanized steel sheet with which the local consumption of the electrode is significant, by which the dot quality is improved and the interval for replacement is considerably prolonged.

Spot welding method of composite metallic plate

Abstract: PURPOSE:To perform spot welding of a composite metallic plate while maintaining satisfactory weld strength without damaging thermally the intermediate layer thereof by interposing a member for current conduction between the composite metallic plate and the other base metal for welding and uniting said plate and base metal to one body by welding. CONSTITUTION:A blind hole 20 arriving at a blank material plate 4b is provided to the desired position of the composite metallic plate 4 by cutting part of one blank material plate 4a and part of the intermediate layer 4c. The member 21 for current conduction consisting of a metal weldable to the base metal is fitted into the hole 20. A similar hole 23 is formed to the other composite metallic plate 3 as well and the length of the member 21 is made equal to or slightly longer than the depth of both holes 20, 23 and is fitted into the hole 23 of the other plate 3 then both plates 4, 3 are superposed on each other in the case of welding the composite metallic plates to each other. Local large current is passed to electrodes while a movable electrode 1 is pressed to weld the contact part by contact resistance. The member 21 is interposed in the same way and the spot welding is executed in the case of welding the plate 4 to the other metallic member 7.

Method for manufacturing a commutator

Abstract: A disk armature for an electric, in-tank fuel pump motor is manufactured by laser welding a pair of annular disks in two concentric circles of spot welds, one near each of the inner and outer circumferences of the disks. One disk is made of malleable copper for the forming of commutator hooks and studs; the other is made of hardened copper alumina for superior wear characteristics in a sour gasoline environment. The welded disks are affixed to an insulating support and cut into segments, each having at least one weld from the inner circle and two from the outer circle. Thus the segments are each securely welded without deformation or degredation of the superior wear properties of the copper alumina disk.

Oxidation preventive device for spot part of spot welding machine

Abstract: PURPOSE:To prevent deterioration and discoloration in a welded spot part by blowing an inert gas to the part where each electrode is in contact with materials to be welded to enclose the periphery of said part so as to shut off air CONSTITUTION:A gas is supplied from an inert gas cylinder 7 by operating a pressure regulator 8 and a needle valve 10 and regulating the flow rate of the gas to an adequate rate while viewing the indication on a flowmeter 9 The inert gas blows out to materials 6 to be welded by passing through the cylindrical space having the widened terminal opening formed of an upper electrode 2 and the inside surface of a nozzle case 13 for preventing oxidation The peripheral space is thus filled with the inert gas The electrode 2 grasps the materials 6 together with a lower electrode 4 and passes large current to the materials, thereby heating said materials Since the heating of the materials 6 is effected in the inert gas, the materials are not subjected to oxidation effect Even if the electrodes begin to part from the materials to be welded upon ending of welding, the gas is still kept blown to provide a cooling effect

Control method of spot welding

Abstract: A spot welding control method is disclosed wherein the welding current and welding time are controlled, in response to changes in the shape of the point of the electrode tip. At each weld point, the lowest value of the varying resistance between the electrode tips is detected in an initial welding period, and each detected lowest value is successively held and stored. At each weld point, a running average of the lowest resistance values is computed, bases on the resistance date of a group of weld points composed of the weld point just completed through a number of preceding weld points, the number of which is preset. The weld conditions are changed from one set of predetermined parameters to another when the computed average reaches the then prevailing threshold limit, following which the threshold is reset. The thresholds are preset depending upon the degree of wear of the electrode tip, whereby welding is continued under newly-selected weld conditions corresponding to the present threshold.

Manufacture of heat exchangers by welding

Abstract: A heat exchanger having a tubular element 10 mounted in thermal engagement with a heat collecting or emitting panel 13 is formed by superimposing the tubular element and panel and clamping them together between a pair of roller-type welding electrodes 20,23. The electrode engaging the tubular element is contoured at 21, so as to engage a substantial part of the circumference of the tubular element over a short length thereof, while the other electrode engages a small area of the panel. A current is applied between the electrodes to form a spot weld between the tubular element and the panel and the tubular element and panel are advanced between the electrodes to form a series of spot welds at spaced locations along their interengaging lengths.

Machine for the production of welded wire gratings

Abstract: of EP00733361. Machine for the production of welded wire gratings from longitudinal and transverse wires (2, 3) intersecting each other at right angles with a multiple spot welding apparatus (1) and with a device for the stepwise movement of the wire grating in accordance with the transverse wire spacing by means of conveying rollers (4, 5) which rotate in opposite directions to one another and which clamp the longitudinal wires (2) between themselves and which are adapted to be driven intermittently in accordance with the spacing of the transverse wires, characterised in that the conveying rollers (4, 5) are situated before the welding apparatus as viewed in the direction of feed of the longitudinal wires (2).

Projection welding method of galvanized steel sheet

Abstract: PURPOSE:To obviate generation of a welding defect with a method for providing a projection to one of galvanized steel sheets and welding said sheets by providing a specific hollow groove to the other galvanized sheet. CONSTITUTION:A projecting part 3 is formed to a steel sheet 1 in the case of welding the steel sheets 1, 2 which are galvanized 1a, 2a on one side. A doughnut-shaped circular groove 4 having the diameter larger than the diameter of the part 3 is provided to the sheet 2. The central parts of the part 3 and the groove 4 are matched and the sheets are welded. Then the part 3 is welded and a nugget 5 is gradually formed and flows into the groove 4. As a result, the welding current is uniformly conducted at the diameter range corresponding approximately to the size of the nugget, by which the welding conforming to the specification is accomplished without change in the current density.

Automatic welding device

Abstract: PURPOSE:To weld fully automatically a housing with one unit of robot by controlling the rotative movement of the welding tool of the welding robot in four axis directions. CONSTITUTION:A work 1 is positioned upside down and is set to a work holding member 35 on a jig 3. A welding gun 4 is set to each welding position of the work 1 by operating manually each motor of a robot 2 and the point on the route traced by the gun 4 is read by each axis by a digital detector and is stored into the storage device of the robot 2. Such teaching operation is performed with all the welding points of the work 1 and is performed while a rotating base plate 34 is rotated by 90 deg. each at every end of the storage of the welding point on the surface of the work 1. When welding is started after such teaching operation is performed, the robot 2 and the jig 3 perform the operation in exact conformity with the stored operation. The plate 34 is automatically rotated 90 deg. when welding of each welding position on the 1st surface of the work 1 is finished and the operation for spot welding the 2nd surface is successively repeated until the work 1 is completed.

Sheet metal welding process

Abstract: A sheet metal welding process is described in which limited zones contact of metal sheets (A, B) are heated locally by a power laser so as to cause fusion in the manner of spot or seam welds (P, C). Such spot or seam welds are achieved by deep penetration welding of juxtaposed metal sheets joined by a plurality of welding spots or seams, these may be spaced apart such that the sheet metal portions between the spots or seams can deform in an elastic-plastic manner under stress.