ELECTRICAL WELDING TEST INSTALLATION BETWEEN ELECTRODES WITH PART PERPENDICULARITY DEFECTS

Abstract

An electric welding test setup comprising two electrodes (10, 12) aligned along a principal axis (A), and between these electrodes (10, 12) a plate (20) connected to a frame, comprising a positioning location (22) for two superimposed flat pieces (2, 4) to be welded, and a hole for the passage of an electrode (10), the plate (20) being connected to the frame by a pivot (34) disposed in a plane perpendicular to the principal axis (A), comprising a locking device at several predefined angular positions relative to this perpendicular plane. Figure 3

Description

Title of the invention: ELECTRICAL WELDING TEST INSTALLATION BETWEEN ELECTRODES WITH DEFECTS IN PERPENDICULARITY OF THE PARTS

[0001] The present invention relates to an electric current welding test installation between two electrodes with perpendicularity defects of the bearing surfaces of the assembled parts with respect to the axis of the electrodes, as well as a method of using such a welding test installation.

[0002] A known type of electrical welding test setup between two electrodes pressing two pieces together, presented in particular by document KR-A-20090031106, comprises a horizontally arranged rotating circular platform held by an axial pivot fixed to a workstation frame.

[0003] The platform has several slots evenly distributed around its perimeter, each receiving two superimposed parts to be assembled, which are positioned by these slots. An electrode fixed to the frame of the unit is positioned opposite a hole in each slot during the rotation of the platform, so as to come under the parts to be assembled after each rotation, following equal fractions of a turn.

[0004] The workstation includes an upright comprising a horizontal arm having below it a movable electrode, which slides vertically so as to come above the parts to be assembled in the axis of the fixed electrode.

[0005] Various part presence control systems incorporating sensors allow for the automation of the station's operation, comprising, for each table stop, simultaneously loading two parts to be welded into an empty slot, welding the parts in the slot between the electrodes, and unloading one welded assembly into a third slot. The table then performs a fraction of a turn to repeat the same operations.

[0006] This type of installation allows for the serial performance of repetitive tests on parts to be welded, in particular for carrying out weld quality tests on a fairly large sample.

[0007] The construction of motor vehicle bodies comprising assemblies of metal sheets uses many electric welding points which must be qualified to ensure quality and safety.

[0008] For this purpose, robots are used for the automatic welding of vehicle bodies, carrying a relatively heavy gripper, moving in space to successively clamp the sheets between the electrodes at each weld point, with, if possible, short cycle times in order to make the investments profitable. high. We have tolerances for electrode positioning, in particular defects in the perpendicularity of the electrode axis, which should not compromise the quality of the welds.

[0009] In particular, certain assemblies of different materials, notably an aluminium sheet on a steel sheet using steel pins passing through the aluminium sheet, are delicate to produce and require precise calibrations of the installation and frequent checks of the results obtained.

[0010] The type of installation according to the prior art, intended to achieve a positioning of the flat parts to be welded perpendicular to the axis of the electrodes, poses problems for qualifying welds exhibiting well-defined defects of this perpendicularity on batches of samples.

[0011] The present invention aims in particular to avoid these problems of the prior art.

[0012] To this end, it proposes an electric welding test installation comprising two electrodes aligned along a main axis, and between these electrodes a platform connected to a frame, comprising a positioning location for two superimposed flat pieces to be welded, and a hole for the passage of an electrode, this installation being remarkable in that the platform is connected to the frame by a pivot disposed in a plane perpendicular to the main axis, comprising a locking device at several predefined angular positions with respect to this perpendicular plane.

[0013] An advantage of this welding test installation is that by providing the locking device with several angular positions progressively offset from the perpendicular plane, it is possible to easily and quickly test the results of welds with defects exhibiting a progressive distancing from the perpendicularity of the electrode axis by choosing several increasing angular deviations easily locked with a precise angle by the locking device.

[0014] It is thus possible to carry out analyses and tests of resistance on the samples produced in a reproducible manner to qualify the acceptable tolerances of the perpendicularity defects.

[0015] These results make it possible in particular to optimize the trajectories and speed of the movements of the welding clamp carried by a robot, taking into account acceptable deviations thanks to the qualification of the welds which can be done repeatedly on a large number of samples.

[0016] The electric welding test installation according to the invention may further include one or more of the following features, which may be combined with each other.

[0017] Advantageously, the pivot is formed on a support fixed to the chassis of the installation.

[0018] In this case, advantageously the locking device comprises a series of holes made on the platform and on the support, which can receive a pin engaged in a hole in the platform and the support to define an angular position.

[0019] Advantageously, the support symmetrically comprises two bosses framing the plate, each comprising a part of the pivot.

[0020] In this case, advantageously each boss comprises a series of holes arranged on an arc of a circle centered on the axis of the pivot.

[0021] Advantageously, the predefined angular positions start with an angle of 0° and increase with an increment of 1°.

[0022] Advantageously, the predefined angular positions are between 0 and 6°.

[0023] The invention also relates to a welding test method for two flat pieces with a test installation comprising any one of the preceding characteristics, remarkable in that it includes, for each predefined angular position, the welding of a batch of identical samples.

[0024] Advantageously, the test process then performs a weld strength measurement test for each batch, and then determines the maximum angular deviation corresponding to a minimum required strength.

[0025] In particular, the test method can perform the welding of the end of a rivet engaged in a bore of an aluminium part, including a shoulder placed on this aluminium part, onto a steel part.

[0026] The invention will be better understood and other features and advantages will become more apparent upon reading the following description given by way of example, with reference to the accompanying drawings in which:

[0027] [Fig. 1] is an axial cross-section diagram of parts to be welded arranged perpendicular to the axis of the electrodes;

[0028] [Fig.2] is a diagram showing a defect in the perpendicularity of the parts;

[0029] [Fig.3] is a view of a platform of a test installation according to the invention in a perpendicular position; and

[0030] [Fig.4] is a side view of this plate with a defect angle.

[0031] Figure [1] shows an upper aluminum sheet 4 to be fixed onto a lower sheet in steel 2, by means of a steel rivet 6 arranged along a main axis A, comprising a body engaged in a bore in the aluminum sheet and an upper collar 8 bearing on this sheet.

[0032] The lower part of the rivet 6 protrudes slightly below the aluminum sheet 4 to compress and weld itself onto the steel sheet 2 by the effect of an electric current between two electrodes aligned on the main axis A, comprising a movable upper electrode 12 clamping the stack onto a fixed lower electrode 10. With the melting of the end of the body of the rivet 6 welding onto the steel sheet 2 until the collar 8 is in contact with the aluminum sheet 4, a permanent fixing of this aluminum sheet by riveting is obtained, allowing the two different materials to be joined.

[0033] Thanks to the perpendicularity of the sheets 2, 4 with respect to the main axis A, a pressure of the end of the rivet 6 is obtained uniformly distributed on the top of the steel sheet 2, which gives a constant welded surface over the entire end ensuring the best hold.

[0034] The [Fig.2] shows a defect in perpendicularity of the clamp carrying the electrodes 10, 12 with respect to the superimposed sheets 2, 4, which forms with the plane perpendicular to the main axis A an angle a due to a bad positioning of this clamp.

[0035] An irregular support is obtained from the end of the rivet 6 on the steel sheet 2, with different pressures giving an uneven quality of the weld over the whole surface.

[0036] After welding a series of samples with the same perpendicularity defect, metallurgical analyses and tensile tests make it possible to measure the mechanical resistance of the rivet 6 to pull-out and the diameter actually welded, in order to accept or reject series production with such a defect.

[0037] Figures 3 and 4 show a square plate 20 comprising a positioning housing 22 for an elongated lower sheet metal sample 2 receiving an elongated upper sheet metal sample 4 which is arranged perpendicularly.

[0038] Two opposite sides of the plate 20 have an edge plate 24 which has in the middle a rising edge forming a semicircle 26 protruding above this plate, which is centered on a horizontal axis of inclination B aligned on the top of the plate.

[0039] A support 30 fixed to the frame of the test installation not shown, comprises a flat base elongated along the axis of inclination B, comprising symmetrically at each end a rising boss 32 forming a semicircle fitted on the outer face of the rising edge 26 of the rim plate 24. On each side of the platform 20 a pivot 34 disposed on the axis of inclination B, connects the rim plate 24 to the boss 32.

[0040] The underside of the plate 20 is positioned at a small distance from the top of the support 30 to form an intermediate space which allows this plate to tilt also to one side or the other around the tilt axis B of the pivots 34, following a maximum angle of 6° corresponding to the maximum defect envisaged.

[0041] A hole formed in the center of the support 30 and the plate 20 allows the lower electrode 10 to engage through these elements, protruding slightly above the bottom of the housing 22, by a value between 0.5 and 1 mm, so as to ensure that the force applied by the upper electrode 12 clamping the stack of sheets 2, 4 is properly taken up by the lower electrode, without interference from the plate.

[0042] Symmetrically on each side of the plate 20, the boss 32 of the support 30 has a series of holes 36 arranged along an arc of a circle on the same radius around the axis of inclination B. On each side of the plate 20 the rising edge 26 also has a series of holes 28 arranged in an arc of a circle on the same radius, but with a small angular offset relative to those of the boss 32 so as to obtain by fitting a pin in a hole of each part the formation of an angle of inclination a of the plate which goes from 0 to 6°, with an increment of 1°.

[0043] A precise and reproducible locking of the angle of inclination a is obtained in a simple and quick manner by tilting the plate 20 according to the required angle, then by engaging a pin on each side in the two aligned holes 26, 38, allowing a series of welding tests to be carried out with this angle.

[0044] Alternatively, different increments of the tilt angles of the platform can be provided, for example 0.5° to obtain more precision on the perpendicularity defects.

[0045] Advantageously, the method for qualifying weld clamp inclination defects comprises a series of welds on identical samples, including one batch for each increasing inclination angle, starting from perpendicularity with the angle α of 0°, which corresponds to the optimum weld strength. Each batch of samples then allows measurement of the weld quality degradation and definition of the maximum acceptable angle to obtain the desired strength level.

Claims

Demands

1. Electric welding test installation comprising two electrodes (10, 12) aligned along a principal axis (A), and between these electrodes (10, 12) a plate (20) connected to a frame, comprising a positioning location (22) for two superimposed flat pieces (2, 4) to be welded, and a hole for the passage of an electrode (10), characterized in that the plate (20) is connected to the frame by a pivot (34) disposed in a plane perpendicular to the principal axis (A), comprising a locking device at several predefined angular positions relative to this perpendicular plane.

2. Test installation according to claim 1, characterized in that the pivot (34) is formed on a support (30) fixed to the chassis of the installation.

3. Test installation according to claim 2, characterized in that the locking device comprises a series of holes (28, 36) made on the plate (20) and on the support (30), capable of receiving a pin engaged in a hole in the plate (20) and the support (30) to define an angular position.

4. Test installation according to claim 3, characterized in that the support (30) symmetrically comprises two bosses (32) framing the platform (20), each comprising a part of the pivot (34).

5. Test installation according to claim 4, characterized in that each boss (32) has a series of holes (36) arranged on an arc of a circle centered on the axis of the pivot (34).

6. Test setup according to any one of the preceding claims, characterized in that the predefined angular positions start with an angle of 0° and increase with an increment of 1°.

7. Test setup according to any one of the preceding claims, characterized in that the predefined angular positions are between 0 and 6°.

8. A welding test method for two flat pieces (2, 4) with a test setup according to any one of the preceding claims, characterized in that it comprises, for each predefined angular position, the welding of a batch of identical samples.

9. Welding test method according to claim 8, characterized in that it then performs a weld strength measurement test for each batch, and then determines the maximum angular deviation corresponding to a minimum strength required.

10. Welding test method according to claim 8 or 9, characterized in that it performs the welding of the end of a rivet (6) engaged in a bore of an aluminium part (4), comprising a shoulder (8) placed on this aluminium part (4), on a steel part (2).