Classifications

• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B23—MACHINE TOOLS; METAL-WORKING NOT OTHERWISE PROVIDED FOR
  • B23K—SOLDERING OR UNSOLDERING; WELDING; CLADDING OR PLATING BY SOLDERING OR WELDING; CUTTING BY APPLYING HEAT LOCALLY, e.g. FLAME CUTTING; WORKING BY LASER BEAM
  • B23K11/00—Resistance welding; Severing by resistance heating
  • B23K11/10—Spot welding; Stitch welding
  • B23K11/11—Spot welding
• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B23—MACHINE TOOLS; METAL-WORKING NOT OTHERWISE PROVIDED FOR
  • B23K—SOLDERING OR UNSOLDERING; WELDING; CLADDING OR PLATING BY SOLDERING OR WELDING; CUTTING BY APPLYING HEAT LOCALLY, e.g. FLAME CUTTING; WORKING BY LASER BEAM
  • B23K11/00—Resistance welding; Severing by resistance heating
  • B23K11/24—Electric supply or control circuits therefor
  • B23K11/25—Monitoring devices
  • B23K11/252—Monitoring devices using digital means
• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B23—MACHINE TOOLS; METAL-WORKING NOT OTHERWISE PROVIDED FOR
  • B23K—SOLDERING OR UNSOLDERING; WELDING; CLADDING OR PLATING BY SOLDERING OR WELDING; CUTTING BY APPLYING HEAT LOCALLY, e.g. FLAME CUTTING; WORKING BY LASER BEAM
  • B23K11/00—Resistance welding; Severing by resistance heating
  • B23K11/24—Electric supply or control circuits therefor
  • B23K11/25—Monitoring devices
  • B23K11/252—Monitoring devices using digital means
  • B23K11/255—Monitoring devices using digital means the measured parameter being a force
• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B23—MACHINE TOOLS; METAL-WORKING NOT OTHERWISE PROVIDED FOR
  • B23K—SOLDERING OR UNSOLDERING; WELDING; CLADDING OR PLATING BY SOLDERING OR WELDING; CUTTING BY APPLYING HEAT LOCALLY, e.g. FLAME CUTTING; WORKING BY LASER BEAM
  • B23K11/00—Resistance welding; Severing by resistance heating
  • B23K11/24—Electric supply or control circuits therefor
  • B23K11/25—Monitoring devices
  • B23K11/252—Monitoring devices using digital means
  • B23K11/256—Monitoring devices using digital means the measured parameter being the inter-electrode electrical resistance
• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B23—MACHINE TOOLS; METAL-WORKING NOT OTHERWISE PROVIDED FOR
  • B23K—SOLDERING OR UNSOLDERING; WELDING; CLADDING OR PLATING BY SOLDERING OR WELDING; CUTTING BY APPLYING HEAT LOCALLY, e.g. FLAME CUTTING; WORKING BY LASER BEAM
  • B23K11/00—Resistance welding; Severing by resistance heating
  • B23K11/24—Electric supply or control circuits therefor
  • B23K11/25—Monitoring devices
  • B23K11/252—Monitoring devices using digital means
  • B23K11/257—Monitoring devices using digital means the measured parameter being an electrical current
• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B23—MACHINE TOOLS; METAL-WORKING NOT OTHERWISE PROVIDED FOR
  • B23K—SOLDERING OR UNSOLDERING; WELDING; CLADDING OR PLATING BY SOLDERING OR WELDING; CUTTING BY APPLYING HEAT LOCALLY, e.g. FLAME CUTTING; WORKING BY LASER BEAM
  • B23K11/00—Resistance welding; Severing by resistance heating
  • B23K11/24—Electric supply or control circuits therefor
  • B23K11/25—Monitoring devices
  • B23K11/252—Monitoring devices using digital means
  • B23K11/258—Monitoring devices using digital means the measured parameter being a voltage
• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B23—MACHINE TOOLS; METAL-WORKING NOT OTHERWISE PROVIDED FOR
  • B23K—SOLDERING OR UNSOLDERING; WELDING; CLADDING OR PLATING BY SOLDERING OR WELDING; CUTTING BY APPLYING HEAT LOCALLY, e.g. FLAME CUTTING; WORKING BY LASER BEAM
  • B23K31/00—Processes relevant to this subclass, specially adapted for particular articles or purposes, but not covered by only one of the preceding main groups
  • B23K31/12—Processes relevant to this subclass, specially adapted for particular articles or purposes, but not covered by only one of the preceding main groups relating to investigating the properties, e.g. the weldability, of materials
  • B23K31/125—Weld quality monitoring
• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B23—MACHINE TOOLS; METAL-WORKING NOT OTHERWISE PROVIDED FOR
  • B23K—SOLDERING OR UNSOLDERING; WELDING; CLADDING OR PLATING BY SOLDERING OR WELDING; CUTTING BY APPLYING HEAT LOCALLY, e.g. FLAME CUTTING; WORKING BY LASER BEAM
  • B23K2101/00—Articles made by soldering, welding or cutting
  • B23K2101/006—Vehicles
• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B23—MACHINE TOOLS; METAL-WORKING NOT OTHERWISE PROVIDED FOR
  • B23K—SOLDERING OR UNSOLDERING; WELDING; CLADDING OR PLATING BY SOLDERING OR WELDING; CUTTING BY APPLYING HEAT LOCALLY, e.g. FLAME CUTTING; WORKING BY LASER BEAM
  • B23K2101/00—Articles made by soldering, welding or cutting
  • B23K2101/18—Sheet panels

Definitions

• the present invention relates to a method for monitoring and / or regulating a quality of welding spots of a resistance welding gun according to claim 1 and to a control device for monitoring and / or regulating a quality of welding spots of a resistance welding gun according to claim 10.
• Modern manufacturing equipment for example for motor vehicles, use automated welding for joining metallic components, in particular sheets.
• a continuous weld seam is not produced, but individual weld points are attached to the metallic components to be welded by means of resistance welding pliers.
• Conventional manufacturing facilities only allow a poor quality control of the welds produced, since the welding guns are acted upon only with a predefined welding current. When the contacts of the welding gun wear off, the current transfer between the welding gun is no longer optimal, so that a too low current flow or a too short welding time lead to the manufactured resistance welding points not having required strength.
• the object of the present invention to provide a method and a controller for monitoring and / or controlling a quality of welding spot welds of a resistance welding gun in order to classify, regulate and document the quality of a manufactured resistance welding point.
• the present invention provides a method for monitoring a quality of weld points of a resistance welding gun, the method comprising the steps of:
• Measuring and storing measured values when carrying out resistance point welding at different locations of a workpiece the measured values being a voltage, a current, a resistance, a welding time, an energy, a force on welding contacts and / or a power during the production of a
• the reference measurement value representing a corresponding voltage, a current, a resistance, a welding time, an energy, a force on welding contacts and / or a power in the production of a corresponding resistance reference welding point
• the present invention provides a control apparatus adapted to perform steps of the above method.
• the present invention is based on the finding that an improvement in the quality of a resistance spot weld to be produced can be achieved by measuring certain physical variables during the application of the resistance spot welds and comparing them with reference variables. Lying the measured quantities outside a tolerance range of, for example, 70% above or below the reference value, such a deviation is registered and stored the deviation. If such a deviation then occurs again from the reference value in a subsequent resistance spot welding or its measured value, this deviation is in turn registered and stored. The subsequent measurement is again compared and stored in an analogous manner with the reference value. If, during the storage, it is determined that there are a certain number of (successive) measured values which are all outside the tolerance range around the reference value, the warning message is output.
• Such an approach for checking and / or regulating the quality of a resistance spot welding offers the advantage that it can be detected very quickly and accurately by the automatic detection whether the corresponding resistance point welding corresponds to a predetermined quality criterion (which is represented by the reference measurement value). If this is not the case, a warning spot weld can be manually reworked by the issued warning message in order to achieve the required quality criterion.
• a predetermined quality criterion which is represented by the reference measurement value.
• the proposed approach offers the possibility in principle of storing the measured value recorded for each workpiece for each resistance spot weld, thus enabling complete quality control of the resistance spot weld.
• a user of the proposed approach is easily able to prove, in the event of a claim for damages, that no defect was present in a workpiece welded in his factory.
• the method may further comprise a step of assessing the quality of a resistance spot weld, wherein for the evaluation of the quality, a time resistance course in the resistance spot welding is compared with a time resistance curve in a resistance reference point welding and the quality of the resistance welding point the basis of an evaluation, whether the time resistance course of the resistance spot welding outside a tolerance range to the temporal resistance course in the saureferenzpunksch spaung or whether a derivative of the time resistance of the resistance point welding at a predefined time outside a tolerance zone to a derivative at the predefined time in the temporal Resistance characteristic of the resistance reference point welding is.
• the method may further output a warning message if, in the step of judging the quality of the resistance spot welding, a predetermined number of consecutively executed resistance welding points have a temporal resistance profile which is at least one time outside the tolerance range the time resistance course of resistance reference spot welding at the appropriate time.
• a warning message can be issued in particular if the Danger of wear and tear is also clearly visible through the chronological sequence of the resistance welding with the resistance welding gun.
• the steps of the method may be performed for each resistance weld point performed by the resistance welding gun.
• Such an embodiment of the present invention offers the advantage that continuous quality monitoring of each welding point is possible, which is carried out by the corresponding resistance welding gun. This allows a particularly detailed documentation of the quality of the welding points that are applied to a workpiece.
• the method further comprises a step of resistance spot welding, wherein the resistance spot welding, the resistance welding current strength and / or the resistance welding voltage to the resistance welding gun is changed compared to a previously performed resistance spot welding, such that the measured value for one in the Again, the step of resistance spot welding is within the tolerance range of the reference measurement value.
• a wear of the resistance welding gun can be compensated by increasing the welding current or the welding time, so that the quality or strength of the produced welding point can be improved.
• a counter can be reset to count successive measured values which lie outside the tolerance range around the reference value.
• the measured values of each resistance spot weld for each workpiece can furthermore be stored in a central memory. This facilitates the argument in the case of a complaint of a defective workpiece, since in such an embodiment of the invention, the quality of each spot weld can be exactly documented and called from the central memory or computer.
• a step of carrying out a reference measurement is also provided, wherein the corresponding reference value is recorded and stored for the subsequent comparison with the measured values.
• the method may further comprise a step of swapping the resistance welding gun, wherein the step of performing a reference measurement is performed after the step of swapping the resistance clamp.
• a low resistance spot welding current is applied to the resistance welding gun, followed by a high resistance spot welding current.
• a low resistance spot welding current is applied to the resistance welding gun, followed by a high resistance spot welding current.
• Fig. 1 is an illustration of a schematic structure of a resistance welding gun for a workpiece to be welded
• FIG. 2 shows an exemplary representation of the assessment of a quality of a manufactured resistance welding point by comparison of measured values with a reference measured value
• FIG. 3 shows an exemplary representation of a judgment of a measured value using a temporal resistance profile in the case of a reference point weld
• Figure 4 is a schematic representation of a time course when the resistance welding gun with a current when an adhesive material is applied between the workpieces to be welded.
• Fig. 5 is a flowchart of an embodiment of the present invention as
• welding robots are often used in modern manufacturing equipment, which can attach a variety of welds to workpieces in a short time using welding tongs.
• Such a welding tongs 100 is shown by way of example in FIG. 1, wherein, in particular, the welding contacts 110 on the welding tongs tip are decisive for a particularly good quality of the spot weld. Namely, when an electric current is supplied to the contacting terminals 120a and 120b of the welding gun 100, this electric current flows via the contact tips 110 of the welding gun 100 into the workpieces 130a and 130b to be connected (which are metal sheets, for example), so that the high current flow these workpieces melt locally and thereby connect in the form of a welding point 140.
• a current, a voltage, a resistance, a welding time, an energy and / or a power in the production of a resistance welding point with the welding gun is added.
• the quality of the weld spot in the reference measurement is optimal and can be used as a benchmark for further measurements on performed welds.
• a welding point for the reference measurement may be set at a certain current of 10 kA so as to be of good quality. This current of 10 kA then forms a reference value 200, as shown for example in Fig. 2.
• a tolerance range 210 can be placed around this reference value 200, which includes, for example, a deviation of ⁇ 30% from this reference value 200, so that a welding point which has been manufactured with a current value in this tolerance range can also be regarded as a weld point with good quality can.
• this reference value 200 and the tolerance range 210 the welding points applied in the work process to the workpieces are now assessed at different times t in the measurements.
• welding points 100 are produced by welding tongs whose measured values 220 are, for example, within the tolerance range 210 around the reference value 200, then a sufficiently good quality of these welding points 220 can be assumed, so that no further control or Reworking is required at these welds. If, however, the welding contacts 110 of the welding tongs 100 are used up, it is no longer possible to transmit sufficient current into the workpieces 130 due to the smaller contact surface, so that the measured values 230 for such welding points lie outside the tolerance range 210 in a region 240. However, a single measured value 230 in the region 240 outside the tolerance range 210 can also occur due to a singular disturbance when setting the welding spot, so that in this case there is no process inconvenience.
• a sequence of consecutive measurements 230 longer than a predetermined number for example, 3 to 5
• a systematic degradation of the quality of welds is detected, resulting in an output of the warning message 250.
• the quality of welding points of a resistance welding gun 100 can be easily monitored so that, if necessary, the welding contacts 110 can be exchanged in good time or the welding gun 100 can be exchanged.
• the measured values 220 and 230 can also be stored for each welding point, so that a complete automatic documentation of the welding spots applied by the welding gun 100 is possible.
• an assessment of the quality of a spot weld can also be made by evaluating the time course of resistance during the welding of the spot weld respectively.
• the resistance profile is recorded during the welding of the reference welding point, as shown for example in FIG. 3 by the line 300.
• a tolerance range 310 around this reference resistance profile 300 can be taken into account, so that the quality of a welding point can be recognized as sufficient if, during the welding process for a weld point to be assessed, the measured time resistance profile 315 does not lie outside this tolerance range 310 when producing the corresponding welding point .
• a derivative 320 of the reference measured value 300 can also be compared with a derivative 325 of a temporal resistance profile 315 of the weld point to be evaluated, wherein the weld point can be assessed as qualitatively sufficient if the derivative has a slope which is within a gradient range, which is reproduced, for example, by the increase characteristics 330 and 340 shown in FIG.
• a current intensity or a welding time may be increased if measured values 230 that lie outside the tolerance range 210 occur.
• a process stability factor can be determined that expresses the process stability of the spot welding process to what extent the weld indicated by the measurement matches the reference weld.
• a process stability value of 100% means full match of the process with the reference welding process, thus signaling a stable welding process.
• a process stability of 70% indicates that the welding process has changed by 30% compared to the reference weld.
• a change may result, for. B. by wear, which can then be detected by the process factor.
• there was a disturbance which had to compensate the U / I controller to improve the quality of welding. Disturbances, if they occur once, are characterized by a one-off deviation from the 100% line, z. B. splashes or edge welding. Continuously increasing deviations indicate wear, mostly from the electrode caps of the welding gun.
• the value of the process stability factor is a unit-free variable calculated and standardized by the welding controller firmware. It describes the stability of a welding process for a spot weld.
• High values represent very stable and secure processes. In processes with such values, there is no or only very little control intervention. In this case, the current resistance curve is almost congruent with the reference resistance curve of each welded point.
• Low values represent very unstable and unsafe processes. In processes with such values, a high control action (large welding time or current changes) can take place. These can ensure a good spot weld, even in unfavorable conditions.
• the calculation of the PSF value is based on an algorithm that is stored in the firmware • the controller.
• Input variables for the calculation of this value are measured and calculated electrical parameters such as current, voltage, resistance, phase angle, power, energy input, but also characteristic quantities that describe the course of the currently measured resistance curve (minima, maxima, slopes).
• the monitoring parameter current time indicates a higher value.
• the process quality results from the exact analysis of the resistance profile of a weld, as shown for example in FIG.
• striking corner points and trends of the curve are used.
• the resistance profile is divided into several sections.
• the most prominent points of the resistance curve are the initial and final resistance, as well as the local maximum and minimum. Gradients and tendencies are derived between these points, which allow a statement about the welding quality.
• the results of the UIP calculation of the individual sections are included in the UIP with varying degrees of weighting, depending on which section is concerned. Since the dynamics of the resistance curve is weak in some welding tasks, a comparison with the corresponding sections of the reference track is additionally produced and included in the calculation. More difficult to interpret is the quality statement in manual tongs when different materials and sheet thicknesses are processed with a program.
• a process quality factor (also called a UIP value) can be a unit-free variable calculated and standardized by the controller firmware. It describes the "theoretically calculated" quality of a welding point, regardless of whether this quality was achieved without or with a compensating control intervention.
• High UIP values predetermine spot welds with a sufficient and good lens diameter on the basis of the calculation which corresponds at least to the point diameter originally taught.
• Low UIP values (where the minimum value is 0) predicts an insufficient dot diameter or even an unattached weld point (even in the case of a control action).
• the calculation of the UIP value is based on an algorithm that is stored in the firmware of the controller. Input variables for the calculation of this value are measured and calculated electrical parameters such as current, voltage, resistance, phase angle, power, energy input, but also characteristic quantities that the course of the currently measured resistance curve (minima, maxima, slopes) and thus the quality of Describe welding.
• the actual values from the reference weld are taken over as reference for the monitoring.
• An image of the limits within which the monitored variable moves results from the displayed course of a monitored variable.
• the tolerances are best placed around the reference value so that most of the welds are in the "good range", so outliers are outside the tolerance bands, making sure that normal manufacturing variations are not outside the tolerance limits (eg. due to low electrode wear, milling)
• the programmed tolerances are displayed as lines and clearly show how the tolerance bands would affect.
• the monitoring for this size can be activated. In addition, it must be checked that the monitoring is also switched on for this program and "General."
• the tolerances are best programmed on a user interface in the following order: 1. Permissible tolerance band above,
• a quality factor can be determined by determining a comparison of the resistances in the current weld with the reference weld.
• the presented function thus enables systematic error detection, which ensures a high standard of quality and production.
• a permanent process spot welding quality can be ensured in a series production, which significantly improves the production conditions.
• the count of the measured values which have occurred can be set outside a permissible tolerance range such that this counter is reset for each workpiece to be welded, so that a component-related quality warning message can be output.
• a production program-related warning message output can be made to determine a long-term wear of the welding gun.
• the proposed approach makes it possible to ensure a monitoring function for a complete shell of the quality of bodies.
• conditional and absolute warning limits are determined and set, the violation of which leads to a warning message at the plant or to a plant stop: - Conditional warning limit:
• conditional warning limits are set in such a way that the violation of such does not actually indicate a bad welding spot, but does indicate a deteriorating process or the danger of a deteriorating point quality.
• the process monitoring can be set so that only a multiple (freely parameterizable) violation of conditional warning limits leads to a plant stop.
• This counter can also automatically be reset to "zero” depending on a certain number of "good welds” for this program.
• conditional and absolute warning limits as well as the determination of the Q stop or system stop logic is free and can be carried out according to the specifications for the quality control loops of the customer's production lines.
• Adhesive thus acts as an insulator between the sheets.
• the welding current flows at the beginning of the weld via shunts and lacks the production of the actual welding point.
• the time until the adhesive is displaced by the heat generation, that is, the welding current flows through the actual welding point can be very different. This ensures no consistent welding quality.
• the normal welding process uses the parameterized welding current, which is generally between 7kA and 12kA, the high heat buildup quickly displaces the adhesive. This happens partly explosively. Since the forceps can not follow this change so quickly, the process response is often very violent, spattering and burning points occur.
• the aim of the function presented here should be to "gently" displace the adhesive, and then, if there is a defined sheet-metal contact, to begin with the actual welding process, the regulator should optimally "withstand the break-through time of the adhesive adapt.
• the welding gun should be charged with a low current.
• a current of about half of the actual welding current so about 4 - 5kA.
• the length of the first phase should be determined so that the adhesive can be displaced.
• the parameterization of the second phase 410 should be designed as would be necessary for the weld jobs without adhesive. In it, the actual welding should take place. In this way, furthermore, the quality of the welding points can be increased if an adhesive material connects the components to be joined before welding.
• the present invention also includes a method 500 for monitoring and / or controlling a weld spot quality of a resistance welding gun, as illustrated in FIG. 5, wherein the method 500 includes a first step of measuring 510 and storing Measurements in performing resistance spot welds at different locations of a workpiece, wherein the measured values represent a voltage, a current, a resistance, a welding time, an energy and / or a power in the production of a resistance welding point. Furthermore, the method comprises a step of comparing 520 the measurement values with a reference measurement value, the reference measurement value representing a corresponding voltage, current, resistance, welding time, energy, and / or power in producing a corresponding resistance weld point. Finally, the method 500 includes a step of outputting 530 a warning message when it is determined in the step of comparing 520 that a predetermined number of successive measured values is outside a predefined tolerance distance from the reference value.
• the invention presented above enables a consistent quality assurance concept for resistance spot welding, which is made possible by regulation, monitoring and evaluation of spot welds.
• the proposed approach is integrated into an overall concept with integrated control and monitoring concept with integrated process monitoring and quality assessment.
• a process for an efficient production process with simultaneous protection of the spot welding quality is ensured.
• Tolerance range around the reference measurement value 220 Measurement values within the tolerance range 210 around the reference measurement value 200

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• Engineering & Computer Science (AREA)
• Mechanical Engineering (AREA)
• Quality & Reliability (AREA)
• Resistance Welding (AREA)

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• 2009
  • 2009-04-07 DE DE102009016798A patent/DE102009016798A1/de active Pending
• 2010
  • 2010-03-26 US US13/263,147 patent/US20120118861A1/en not_active Abandoned
  • 2010-03-26 KR KR1020117023644A patent/KR20120071413A/ko not_active Application Discontinuation
  • 2010-03-26 CN CN2010800248863A patent/CN102458752A/zh active Pending
  • 2010-03-26 EP EP10712709A patent/EP2416919A1/de not_active Withdrawn
  • 2010-03-26 MX MX2011010619A patent/MX2011010619A/es not_active Application Discontinuation
  • 2010-03-26 BR BRPI1015289A patent/BRPI1015289A2/pt not_active IP Right Cessation
  • 2010-03-26 RU RU2011144607/02A patent/RU2011144607A/ru not_active Application Discontinuation
  • 2010-03-26 WO PCT/EP2010/001904 patent/WO2010115524A1/de active Application Filing

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