Abstract:
A weld tip testing head is presented. An alignment member has an aperture disposed therein and is coupled to a spring element. The spring element is further coupled to a mounting. The aperture is operable to removably receive a weld tip and the alignment member is operable to determine an alignment associated with the weld tip. Computer software is encoded on storage. The computer software is operable to receive the alignment from the alignment member and analyze the alignment with respect to at least one expected alignment value. The computer software is further operable to generate an alarm based on the analysis and generate a fault based on the analysis.

Description:
TECHNICAL FIELD OF THE INVENTION  
         [0001]    This invention relates in general to welding, and, more specifically to a method and system for weld process monitoring.  
         BACKGROUND OF THE INVENTION  
         [0002]    As computers have grown increasingly important in today&#39;s society, various industries have increasingly adopted computer controlled systems for more efficient and effective control and monitoring of equipment. Industries using automatic welding have increasingly used computer controlled equipment.  
           [0003]    Industries involved with automatic welding have turned to computer controlled machinery to increase the efficiency of assembly lines. One common operation on an assembly line is the welding together of components. The welding operation is often performed automatically by a computer-controlled welding device. Often, a determination of proper operation of the welding device is performed manually by inspecting welds after they are performed. For example, a pry test may be used to determine a bad weld that has not properly joined two elements. However, manual inspection can be undesirable as many bad welds can be created before a problem is detected.  
         SUMMARY OF THE INVENTION  
         [0004]    The present invention provides an improved method and system for weld process monitoring. In one embodiment of the present invention, a weld tip testing head is described. An alignment member has an aperture disposed therein and is coupled to a spring element. The spring element is further coupled to a mounting. The aperture is operable to removably receive a weld tip and the alignment member is operable to determine an alignment associated with the weld tip. Computer software is encoded on storage. The computer software is operable to receive the alignment from the alignment member and analyze the alignment with respect to at least one expected alignment value. The computer software is further operable to generate an alarm based on the analysis and generate a fault based on the analysis.  
           [0005]    The present invention provides numerous technical advantages. Various embodiments of the present invention may provide all, some or none of these technical advantages. One such technical advantage is the capability to detect possible welding problems before many bad welds are made. By checking various elements of the performance of the welding equipment, problems and developing problems may be more quickly detected. Early detection of problems decreases the number of bad welds and increases the productivity of, for example, an assembly line.  
       
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0006]    The present invention is best understood from the detailed description which follows, taken in conjunction with the accompanying drawings, in which:  
         [0007]    [0007]FIG. 1 is a block diagram illustrating a weld process monitoring system according to one embodiment of the present invention;  
         [0008]    [0008]FIG. 2 is a side view illustrating details of a testing element associated with the monitoring system of FIG. 1 according to one embodiment of the present invention;  
         [0009]    [0009]FIG. 3 is a top view of the testing element according to one embodiment of the present invention;  
         [0010]    [0010]FIG. 4 is a diagram illustrating further details of a tip dresser associated with the monitoring station of FIG. 1 according to one embodiment of the present invention; and  
         [0011]    [0011]FIG. 5 is a flow chart illustrating an exemplary method of operation of the monitoring system of FIG. 1 according to one embodiment of the present invention.  
     
    
     DETAILED DESCRIPTION OF THE INVENTION  
       [0012]    [0012]FIG. 1 is a block diagram illustrating a weld process monitoring system  10 . System  10  comprises an assembly line  12 , a welding station  14 , a weld arm  16 , a control system  18 , and a monitoring station  20 .  
         [0013]    Assembly line  12  comprises a suitable assembly line for placing physical items in a location accessible by welding station  14 . More specifically, assembly line  12  may move physical products along a predetermined path such that welding station  14  is given suitable time to perform one or more welds on the products.  
         [0014]    Welding station  14  comprises a station for performing automated, manually and/or partially manually controlled welding on products on assembly line  12 . More specifically, welding station  14  may provide mechanical and/or logical control of welding arm  16  for welding products on assembly line  12 .  
         [0015]    Welding arm  16  comprises an articulated or non-articulated arm operable to move to weld products on assembly line  12 . Welding arm  16  also comprises one or more weld tips  22 .  
         [0016]    Weld tips  22  comprise tips operable to create a weld. In one embodiment, weld tips  22  comprise copper tips used to perform resistive welding and may be water cooled or air cooled. The invention is not limited to any specific number of weld tips  22 , any particular material for fabrication weld tips  22 , or any kind of cooling mechanism.  
         [0017]    Control system  18  comprises a processor  24  and/or storage  26 . Processor  24  comprises a suitable general purpose or specialized data processing device, such as an application specific integrated circuit (ASIC), a field programmable gate array (FPGA), a general purpose central processing unit (CPU) or other suitable hardware operable to execute computer software stored in storage  26 .  
         [0018]    Storage  26  comprises suitable transient and/or persistent computer-readable storage, such as a computer-readable medium, either alone or in suitable combination. For example, storage  26  may comprise one or more of magnetic storage, optical storage, electronic storage, such as random access memory (RAM) and dynamic random access memory (DRAM) and other suitable physical, optical or electronic storage in suitable combination. Storage  26  is operable to store computer instructions executable by processor  24 . Alternatively, the functions performed by control system  18  may be performed by a combination of hardware and software or may exist entirely in hardware.  
         [0019]    Control system  18  is operable to assist welding station  14  in the operation and control of weld arm  16  and weld tips  22 . Control system  18  is further operable to receive information from monitoring station  20  and welding station  14  for storage and analysis. For example, control system  18  may receive errors or other data generated at welding station  14  or monitoring station  20  for recording in a log on storage  26 . Multiple control systems  18  can be used for different components without departing from the scope of the invention. In addition, data associated with monitoring station  20  may be sent to one or more remote computers.  
         [0020]    Monitoring station  20  comprises a testing element  30  and a tip dresser  32 . Monitoring station  20  is operable to perform various testing and repair actions on weld tips  22 .  
         [0021]    Testing element  30  is operable to perform one or more tests on weld tips  22 . For example, testing element  30  may determine weld tip cooling status, weld tip alignment, available squeeze force of weld tips  22 , a pneumatic component status associated with arm  16 , and force settings associated with welding station  14 . Some of these tests may be omitted or other tests performed without departing from the scope of the invention. Testing element  30  is described in greater detail in association with FIGS. 2 and 3.  
         [0022]    Tip dresser  32  is operable to repair weld tips  22 . More specifically, as weld tips  22  are used to weld products on assembly line  12 , weld tips  22  may become dull. Tip dresser  32  operates to sharpen weld tips  22 . Tip dresser  32  is discussed in greater detail in association with FIG. 4.  
         [0023]    In operation, products move along assembly line  12  to welding station  14 . Welding station  14  then instructs weld arm  16  to create one or more welds on the product on assembly line  12 . For example, arm  16  may be articulated and move weld tips  22  to the location where welds are needed. Weld tips  22  then generate welds as appropriate. In one embodiment, weld tips  22  squeeze around the desired location of the weld and then use resistive welding to generate a weld. More specifically, arm  16  may move weld tips  22  closer together so as to hold the portions of the product to be welded in a stationary and touching position while the weld is completed. After a predetermined number of jobs, welding station  14  moves weld tips  22  to monitoring station  20  (or moves monitoring station  20  to weld tips  22 ). At monitoring station  20 , various tests are performed on weld tips  22  by testing element  30  and tip dresser  32 . Welding station  14  then returns weld arm  16  and weld tips  22  to welding products on assembly line  12 .  
         [0024]    [0024]FIG. 2 is a side view illustrating details of an example of a testing element  30  constructed in accordance with the invention. FIG. 3 is a top view of testing element  30 . FIGS. 2 and 3 are discussed together for increased clarity. Testing element  30  comprises a mounting  50 , one or more alignment sensors  52 , one or more springs  53 , a pressure sensor  54 , a temperature sensor  56  and an aperture  58 .  
         [0025]    Mounting  50  provides an essentially stable attachment to monitoring station  20  such that testing element  30  is relatively securely mounted to monitoring station  20 . For example, mounting element  50  may comprise a steel arm. Mounting element  50  could be almost any shape and could be made of many different materials.  
         [0026]    Alignment sensors  52  comprise elements operable to detect a misalignment of weld tips  22 . In one embodiment, alignment sensors  52  comprise spring mounted members shaped like portions of a washer or an entire washer operable to move in response to contact with weld tips  22 . The shape of alignment sensors  52  is relatively unimportant as is the number of alignment sensors  52 . In the illustrated embodiment, a single alignment sensor  52  is located on each of opposing sides of testing element  30 . However, multiple alignment sensors  52  could be included on either side of testing element  30  such that the direction of misalignment could be sensed. For example, four sensors could be placed on each side to locate misalignment in one of four quadrants. Movement of alignment sensors  52  is detectable by monitoring station  20 . The particular alignment sensor  52  which is moved may also be available to monitoring station  20 . Alternatively, alignment sensor  52  may comprise a laser, an infrared sensor or other suitable mechanical, electrical or optical alignment detection equipment.  
         [0027]    Aperture  58  is disposed within alignment sensor  52  and allows insertion of weld tips  22  through alignment sensor  52 . If weld tips  22  are not aligned with aperture  58 , then alignment sensor  52  will be activated. The size of aperture  58  may be varied in order to set particular tolerances for the alignment of weld tips  22 . For example, a three-quarter inch tip may be used with a seven-eighths inch aperture  58  so as to allow minimal tolerance for misalignment of weld tips  22 .  
         [0028]    Spring  53  comprises a compressible element coupled to alignment sensor  52  and mounting  50 . Spring  53  is compressible in response to force applied to alignment sensor  52 , such as when weld tip  22  comes into contact with alignment sensor  52 . In one embodiment, depression of spring  53  causes generation of a piezo-electric charge which is receivable by monitoring station  20  for analysis by control system  18 . In another embodiment, movement of alignment sensors  52  on springs  53  may be detected by a laser or other optical system, for example, where the movement of alignment sensor  52  breaks one or more laser beams. In general, one or more sensor elements  55  may be coupled to mounting  50  for detecting compression of alignment sensor  52 . For example, sensor element  55  may comprise a laser, a piezo-electric current generator responsive to spring  53 , a mechanical sensor, an optical sensor, an electronic sensor, a magnetic sensor or other suitable sensing device.  
         [0029]    Force sensor  54  comprises a sensor element operable to measure the force exerted by weld tips  22 . For example, force sensor  54  may comprise a strain gauge, a load cell, or other mechanical force sensors.  
         [0030]    Temperature sensor  56  comprises a sensor operable to detect the temperature of welding tip  22 . Temperature sensors  56  may be operable to individually determine the temperature of the one of weld tips  22  to which the temperature sensor  56  is adjacent. For example, temperature sensors  56  may detect the heat radiated by weld tips  22  as weld tips  22  are inserted into testing element  30 . Infrared sensor  56  may comprise an infrared heat sensor, a thermocouple or other suitable temperature measurement equipment. As noted, one temperature sensor  56  may separately determine the temperature of an upper weld tip while a second temperature sensor  56  determines the temperature of a lower weld tip.  
         [0031]    In operation, weld tips  22  are inserted into testing element  30  through aperture  58 . If weld tips  22  are misaligned from their expected position, then weld tips  22  will impact one or more of alignment sensors  52 . If alignment sensors  52  move in response to weld tips  22 , then monitoring station  20  will sense a misalignment of weld tips  22 . Alternatively, when alignment sensors  52  comprises optical devices, such as lasers, mis-alignment may be detected by intersection of weld tips  22  with a laser beam.  
         [0032]    In addition, by detecting which alignment sensors  52  are moved, monitoring station  20  may be given a better idea of the nature and extent of the misalignment of weld tips  22  where multiple sensors are used on each side of testing element  30 .  
         [0033]    Temperature sensors  56  determine the current temperature of weld tips  22  and the associated data is captured by monitoring station  20 . Force sensor  54  determines the amount of pressure provided by weld tips  22  and the associated data is also captured by monitoring station  20 . More specifically, weld tips  22  may be inserted into aperture  58  with the same amount of speed and pressure used when weld tips  22  are welding products. After relevant measurements have been made, weld tips  22  withdrawn from testing element  30  can be moved to tip dresser  32  or can be returned to performing welding.  
         [0034]    [0034]FIG. 4 is a diagram illustrating further details of tip dresser  32 . Tip dresser  32  comprises a tip dresser element  100 , a load sensor  101  and a vibration sensor  102 . Tip dresser element  100  comprises an element operable to receive weld tip  22  and sharpen weld tip  22 . More specifically, tip  22  is inserted in tip dresser element  100  to be sharpened. Tip dresser element  100  may use spinning blades driven by a motor to sharpen weld tips  22 . Typically, the act of sharpening a weld tip  22  is referred to as “tip dressing”. Tip dresser element  100  may be coupled to monitoring station  20 .  
         [0035]    Motor load current sensor  101  is coupled to tip dresser element  100  and is operable to detect the electrical current draw of the motor driving the blades of tip dresser element  100 . Motor load current sensor  101  communicates the electrical current draw of the tip dresser motor to monitoring station  20 .  
         [0036]    Peak vibration accelerometer  102  detects the peak vibration of tip dresser element  100 . By detecting the vibration of tip dresser element  100 , peak vibration accelerometer  102  is operable to detect an unbalanced or malfunctioning tip dresser motor.  
         [0037]    In operation, weld tips  22  are inserted into tip dresser element  100  for sharpening. Tip dresser element  100  then rotates one or more blades at an appropriate speed in order to sharpen weld tips  22 . More specifically, tip dresser element  100  attempts to form a pointed tip on weld tips  22 . Current sensor  101  measures the amount of electrical current drawn by a motor driving the blades and communicates the amount of electrical current drawn by the motor to control system  18  for analysis. The amount of electrical current drawn by the motor may indicate a failing motor, such as by drawing more electrical current than usual, dulled blades or other problems. Accelerometer  102  detects the amount of vibration resulting from operation of tip dresser element  100 . The detected vibration levels are communicated to control system  18  for analysis. For example, increasing vibration may indicate a broken blade which is unbalancing tip dresser element  100 .  
         [0038]    [0038]FIG. 5 is a flow chart illustrating an exemplary method of operation of system  10 , unless an order for the various steps is obviously required, the steps could occur in any order. The method begins at step  200 , where control system  18  determines whether the check interval for weld arm  16  and weld tips  22  has been reached. In one embodiment, the check interval is reached when welding station  14  has performed a certain number of jobs, where a job comprises a certain number of welds. For example, after five jobs involving ten welds each, control system  18  may determine that the check interval has been reached and have welding station  14  move control arm  16  and weld tips  22  to monitoring station  20  for testing. Alternatively, monitoring station  20  may move to weld tips  22  or both weld tips  22  and monitoring station  20  may move.  
         [0039]    Next, at step  202 , testing element  30  determines the temperature of weld tips  22 . More specifically, using temperature sensors  56 , the temperature of weld tips  22  may be determined. Once the temperature of weld tips  22  is determined, the amount of cooling being provided at the weld tip may be determined by comparing the actual temperature of weld tips  22  to an expected temperature or range of temperatures for weld tips  22 . Thus, malfunctions in the weld tip cooling system or defects in the weld tips  22  may be detected. More specifically, weld tips  22  may be cooled using a water cooling system where water is circulated through arm  16  to weld tips  22  to draw away heat generated during the welding process. Improper cooling of weld tips  22  may contribute to decrease the life span of weld tips  22  and increase the chance of improper welding.  
         [0040]    At step  204 , the alignment of weld tips  22  is determined by monitoring station  20 . More specifically, as weld tips  22  are inserted in testing element  30 , alignment sensors  52  may be moved. If the alignment sensors  52  are moved by weld tips  22 , then weld tips  22  and/or arm  16  are not correctly aligned. Control system  18  and monitoring station  20  can then use this information to realign arm  16  and/or weld tips  22  and/or to inform repair personnel of the need to realign arm  16  and weld tips  22 .  
         [0041]    Proceeding to step  206 , the squeeze force applied to weld tips  22  is determined. More specifically, force sensor  54  measures and records the amount of pressure exerted by weld tips  22 . As weld tips  22  are used to weld products on assembly line  12 , their capability to squeeze with sufficient force may decrease due to wear or other problems. Monitoring station  20  may be used to ensure that the proper squeeze force is applied to properly weld products. The measured squeeze force at sensor  54  may be communicated to monitoring station  20  for analysis at control system  18  and/or sent to remote computer systems.  
         [0042]    Then, at step  210 , weld tips  22  are moved from testing element  30  to tip dresser  32  (or tip dresser  32  is moved or weld tips  22  and tip dresser  32  are both moved). At tip dresser  32  the force setting of tip dressing element  100  is determined. More specifically, the amount of force used to spin the cutting blades of tip dresser element  100  is determined using the current measurement described above.  
         [0043]    At step  214 , accelerometer  102  is used to detect excess vibration, which could indicate a bent weld gun or bad alignment.  
         [0044]    Next, at step  218 , the interval since the last check performed by monitoring station  20  and arm  16  and weld tips  22  is determined. More specifically, control system  18  analyzes information from monitoring station  20 , such as the time of the present check of arm  16  and weld tips  22 , and determines if an unusual and/or unexpected amount of time has passed since the last check operation.  
         [0045]    Proceeding to step  220 , the amount of time taken by the tip dressing operation by tip dresser element  100  is determined. Then, at step  222 , damaged cutter blades in tip dresser element  100  are detected based upon this time interval and/or a vibration analysis using accelerometer  102 .  
         [0046]    Then, at step  224 , cutter blade sharpness is estimated. More specifically, cutter blade sharpness is estimated by analyzing the amount of time needed to sharpen the weld tip  22 . Dull cutter blades may not sharpen tip  22  appropriately and/or may take an unexpected amount of time.  
         [0047]    Then, at step  228 , control system  18  analyzes the results of steps  200  through  226 . More specifically, a predetermined acceptable range may be associated with each measured item, such as temperature, alignment and squeeze force. The measured value is then compared to the expected value. In addition, control system  18  may have fault ranges for the various measured elements, such as temperature, alignment and squeeze force, may be provided to system  18 . Control system  18  may then compare the measured values to the fault range of values. The fault range indicates operating values of the measured elements that indicate imminent failure or serious problems.  
         [0048]    Proceeding to decisional step  230 , control system  18  determines whether an alarm should be generated. More specifically, an alarm may be a trend detected based on the analysis of the information gathered indicating that while things are currently operating within parameters that a problem may soon occur. For example, tip dresser  32  may currently be operating within acceptable operating parameters, but an analysis of tip dresser  32  may indicate that major replacement may soon be needed. Alarms may be generated using historical data and/or the currently measured data.  
         [0049]    For another example, the measured temperature of tip dresser  22  may exceed the acceptable range of temperatures for a tip dresser  22 . This information can be used by a plant manager or other administrator to schedule down time for monitoring station  20  and schedule other replacement and repair operations associated with the monitoring station  20 . For another example, arm  16  and weld tips  22  may presently be operating within acceptable parameters, but analysis of the data returned by monitoring station  20  may indicate that significant work my soon be needed. If a trend is detected, then the YES branch of decisional step  230  leads to step  232 .  
         [0050]    At step  232 , an alarm is generated and communicated to an appropriate person indicating the trend that has been detected. For example, probable failure in the near future may be communicated to a plant manager or operational supervisor via e-mail indicating the imminent failure and the analysis which indicated the imminent failure. The plant manager may then use the alarm to schedule maintenance so as to decrease the down time and impact of the repair. In one embodiment, the alarm includes the data which triggered the alarm. Returning to step  230 , if no alarms are to be generated, then the NO branch leads to decisional step  234 .  
         [0051]    At decisional step  234 , control system  18  determines whether a fault exists. Typically, a fault indicates more immediate problems than alarms. For example, imminent failure of weld tips  22  may be detected by control system  18  analyzing information from monitoring station  20 . If a fault is detected by control system  18 , then the YES branch of decisional step  234  leads to step  236 . At step  236 , a fault is generated and communicated to an appropriate person. In some embodiments, a fault may cause automatic shutdown of the welding equipment. For example, imminent failure of the cooling system for weld tips  22  may be communicated via a message sent to a plant manager. In one embodiment, the fault includes the data which triggered the fault. Returning to step  234 , if no fault is detected then the NO branch of decisional  234  leads to step  238 .  
         [0052]    At step  238 , control system  18  records data received from monitoring station  20  on storage  26 . In one embodiment, data is recorded by control system  18  in the manner consistent with ISO 9000 procedures. The method then ends.  
         [0053]    Other changes, substitutions, and alterations are also possible without departing from the spirit and scope of the present invention, as defined by the following claims.