The Xiris Blog

Using a Light Meter for Automatic Weld Monitoring

Posted by Cameron Serles on Tuesday, August 02, 2016 @ 02:30 AM

With the advent of high dynamic range weld cameras such as the Xiris XVC-1000, images of welding processes can be made with enormous ranges of brightness.  As a result, it is now possible to monitor and record good quality video of most welding processes using an HDR camera.  With good quality images of the weld pool, arc and seam, the next logical step is to incorporate image processing into the camera system to extract additional information to help operators better control the welding process.

One of the most basic tools for image processing is a LightMeter.  The LightMeter tool from Xiris provides statistical information about the pixel values in an area of interest.  It can be used as an overall measure of the intensity of a weld process, detect part or feature presence, or be the first step in performing powerful image processing on an area of interest.

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Figure 1 : LightMeter Window

The LightMeter generates a histogram based on the light intensities of the pixels in an area of interest, calculating a number of statistics, including:

Median – the brightness level that separates all the pixels in the area of interest into two equal halves.

Mean - the average brightness of all the pixels in the area of interest

Mode - the pixel brightness level that appears most often in the area of interest.

Minimum - the value of the darkest pixel in the area of interest.

Dark Tail – the pixel value at which a specific percentage of the total number of pixels in an area of interest are found to be darker.

Bright Tail - the pixel value at which a specific percentage of the total number of pixels in an area of interest are found to be brighter. 

Maximum – the value of the brightest pixel in the area of interest.

Standard Deviation – the amount of variation or dispersion of brightness levels of all the pixels in an area of interest.

Sum – the addition of all the pixel values in the area of interest.

These measurements can be used as building blocks by users and developers to create automatic inspection algorithms to measure welding features and parameters with the goal of performing a level of process or quality assurance.

A sample histogram with some of the key features is displayed below:

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Figure 2: Sample Histogram

Conclusion:

By incorporating image processing tools such as a LightMeter tool into their weld camera systems, machine builders can measure features of their weld processes in a way that has never before been possible.  It is now possible to find and measures levels of light across an entire image, or in a region of interest in an image.  This can provide information about features of the weld, such as the weld wire, melt pool or weld seam, that could allow for further monitoring or analysis, or form the foundation for seam tracking or weld pool geometry analysis.

For more information on how Xiris Weld Cameras and the LightMeter image processing tool can enhance the quaity and economy of your welding processes, visit Xiris.com

Topics: weld camera, image processing, Xiris, welding, High Dynamic Range, area of interest

How to Get the Best View of an Open Arc Weld

Posted by Cameron Serles on Thursday, July 17, 2014 @ 06:00 PM

Attaining a good image of a weld and the surrounding background has been a struggle ever since video cameras for welding became available.  The problem has always been the range of brightness that occurs during welding: the ratio between the maximum and minimum light intensity is usually too great for a standard camera to measure properly.  Standard cameras on the market today can typically measure about 1,000 levels of brightness between the maximum and minimum light levels in an image.  However, in a typical open arc welding environment, there is a brightness range that can exceed 10,000,000 levels of brightness between the brightest portion of the welding arc, and the darker areas surrounding the weld.  Using a standard camera to image such a weld will create an image similar to the image below on the left, where the camera sensor will image the scene up to a point and then saturate when it gets too bright. This causes the bright areas of the image to appear as a white blur.

 

To solve this problem, Xiris Automation has developed the XVC-O View Camera that uses advanced electronics with logarithmic sensitivity to be able to see more than 10,000,000 levels of brightness in an image.  As a result, more image detail is visible than ever seen before. The detail of the weld arc, the shielding gas, weld pool, torch tip, and weld seam can all clearly be seen.  The image below on the right is an image taken from the XVC-O camera of an open arc welding process. The weld arc is no longer saturated and is clearly visible as is the detail of the background, providing better quality information for the weld operator.

 

GOOOOOOD resized 600       Standard Camera Image of a Weld                      Xiris XVC-O Camera Image of a Weld

With the ability to see more detail of the weld arc and the surrounding environment, welding technicians are able to use the XVC-O to better control their welding processes through better quality assurance and process feedback. 

To see examples of the video quality possible with the XVC-O across a variety of welding processes and materials, please see our Weld Video Library here.

 

Topics: weld camera, weld inspection, Laser welding, welding automation, weld environment, Machine Vision, image processing, Education, Welding Process, weld video, Xiris, image contrast

Monitoring Tube and Pipe Production to Find SCARFING Defects

Posted by Cornelius Sawatzky on Tuesday, June 17, 2014 @ 12:53 PM

Recent advancements in machine vision technology have made a new type of inspection able to see defects related to the forming and welding area of a tube or pipe.  The result is improved quality assurance and process control on the production line.  The new type of inspection device is a laser-based triangulation system that measures the outside contour of a tube or pipe in the vicinity of its weld. 

Typically NDT systems are placed at the end of a production as a final check.  However, the laser inspection system can be placed directly after the weld box.  This system can let operators know what is changing in their welding process, allowing them to perform corrective action before significant scrap occurs. This capacity is especially helpful for one of the most common defects found across all types of Tube manufacturing: Tube Scarf defects.

 

The Scarfing Width

In certain situations on ERW/HF tube and pipe production lines, there is not enough space to perform the Non Destructive Inspection (NDI) measurements right after the weld box because the scarf tool (used to remove excessive bead from the tube) is placed directly after the weld box.  In such situations, the measurement process must be made after the scarfing tool, measuring the flat area of the tube where the scarf has occurred. On some production lines, this measurement is essential to identify the shape and profile of the tube, and to understand how it is travelling through its forming process.

Known as the scarf width, this measurement is defined as the length of the “flat” portion of the tube that appears after the weld bead has been removed by scarfing.  Scarf width measurement changes quickly during production, so it is best averaged over a number of inspections in order to make the measurement stable.

 June 17.14 Blog Scarfing resized 600

The Scarf Width, where “w” = the width of the defect.

How the WI2000p System Measures the Scarf Width

Xiris Automation Inc. has developed a non-destructive inspection system called the WI2000p Weld Inspection System. The WI2000p includes a laser line and a camera whose optical axis is offset to the axis of the laser line by an “offset angle”.  The WI2000p creates a visible cross-section of the tube by projecting the laser line on to the tube and capturing an image of the line using the camera.  The resulting image shows a profile of the tube surface as if it were cut in cross section.  If a tube is ideally round, the laser image will represent a section of an ellipse and any anomaly such as a freeze line defect can be mathematically detected. 

The WI2000p bases all of its measurements on the differences between the actual laser profile line seen by the camera, and the ideal mathematical profile based on the tube parameters.  By knowing the position of the actual laser profile, the ideal profile, and the size of the pixels in the image, the WI2000p can detect weld bead profile defects that often escape detection by other quality tools such as Eddy Current testing, or Ultrasonic Testing techniques

 

Conclusion

Overall, laser-based 3D imaging systems, such as the WI2000p from Xiris, offer an excellent measurement option for tube mill owners/operators who want additional, real-time monitoring of weld features. They can be used in a proactive manner, warning operators what is changing in their welding process so that they can perform corrective action before significant scrap occurs And by measuring the outside contour of a weld, laser-based 3D imaging systems can operate on any type of material, regardless of its reflectance or magnetic properties, using a single head to perform the measurement.

Topics: quality control, weld camera, weld inspection, Laser welding, image processing, High Dynamic Range, Tube and Pipe welding, laser-based monitoring, Pipe Cladding, welding defect, scarfing

Monitoring Tube and Pipe Production to Find FREEZE LINE Defects

Posted by Cornelius Sawatzky on Tuesday, June 03, 2014 @ 03:09 PM

Recent advancements in machine vision technology have made a new type of inspection able to see defects related to the forming and welding area of a tube or pipe.  The result is improved quality assurance and process control on the production line.  The new type of inspection device is a laser-based triangulation system that measures the outside contour of a tube or pipe in the vicinity of its weld. 

Typically NDT systems are placed at the end of a production as a final check.  However, the laser inspection system can be placed directly after the weld box.  This system can let operators know what is changing in their welding process, allowing them to perform corrective action before significant scrap occurs. This capacity is especially helpful for one of the most common defects found across ERW Tube manufacturing:  Freeze Line defects in the weld bead. 

 

The Freeze Line Defect

Particularly in Electric Resistance Welding (ERW) or High Frequency (HF) welding processes, incomplete heating of the faces of the parent material can sometimes occur, resulting in a potentially cold-welded joint, which manifests itself as a line or seam extending from the top surface of a weld down into the welded area, in the shape of a sharp valley. Such a defect could indicate major metallurgical or structural problems in a weld, such as cold welding or improper forming.  It can very often be a point of a major failure of a weld in high-stress applications because the freeze line acts as a crack initiator into the welded material.  The Freeze Line becomes a concern to weld operators when it goes below the surface of the parent material of the tube because once the weld bead has been removed through grinding or scarfing, there is a risk that a void of non-welded material could be left behind.

The freeze line is measured from the lowest point of any contour in the weld bead to the surface of the parent material as defined by the ideal circle scribed by the walls of material beyond the weld zone.  If the freeze line goes below a pre-defined height, then it is considered a defect.

June 3.14 Blog Freeze Line resized 600

The Freeze Line Defect, where “h” = the height of the defect.

 

How the WI2000p System Measures the Freeze Line Defect

Xiris Automation Inc. has developed a non-destructive inspection system called the WI2000p Weld Inspection System. The WI2000p  includes  a laser line and a camera whose optical axis is offset to the axis of the laser line by an “offset angle”.  The WI2000p creates a visible cross-section of the tube by projecting the laser line on to the tube and capturing an image of the line using the camera. The resulting image shows a  profile of the tube surface as if it were cut in cross section.  If a tube is ideally round, the laser image will represent a section of an ellipse and any anomaly such as a freeze line defect can be mathematically detected. 

The WI2000p bases all of its measurements on the differences between the actual laser profile line seen by the camera, and the ideal mathematical profile based on the tube parameters.  By knowing the position of the actual laser profile, the ideal profile, and the size of the pixels in the image, the WI2000p can detect weld bead profile defects that often escape detection by other quality tools such as Eddy Current testing, or Ultrasonic Testing techniques

 

Conclusion

Overall, laser-based 3D imaging systems, such as the WI2000p from Xiris, offer an excellent measurement option for tube mill owners/operators who want additional, real-time monitoring of weld features. They can be used in a proactive manner, warning operators what is changing in their welding process so that they can perform corrective action before significant scrap occurs And by measuring the outside contour of a weld, laser-based 3D imaging systems can operate on any type of material, regardless of its reflectance or magnetic properties, using a single head to perform the measurement.

Topics: quality control, weld camera, weld inspection, Laser welding, image processing, High Dynamic Range, Tube and Pipe welding, laser-based monitoring, Pipe Cladding, welding defect, freeze line

Monitoring Tube and Pipe Production to Detect BEAD ROLL

Posted by Cornelius Sawatzky on Tuesday, May 13, 2014 @ 02:29 PM

Recent advancements in machine vision technology have made a new type of inspection able to see defects related to the forming and welding area of a tube or pipe.  The result is improved quality assurance and process control on the production line.  The new type of inspection device is a laser-based triangulation system that measures the outside contour of a tube or pipe in the vicinity of its weld. 

Typically NDT systems are placed at the end of a production as a final check.  However, the laser inspection system can be placed directly after the weld box.  This system can let operators know what is changing in their welding process, allowing them to perform corrective action before significant scrap occurs. This capacity is especially helpful for one of the most common defects found across all types of Tube manufacturing:  excessive Bead Roll. 

 

The Bead Roll Measurement

The nature of some welding processes such as Laser Beam Welding (LBW) or GTAW (TIG) require that the weld bead remains within narrow range around the centerline of the tube to ensure the best quality weld.  Any small deviation from the centerline can cause a variety of welding defects mentioned earlier in this blog.  With such precision welding processes, the bead position cannot change even momentarily or a bad weld will result.  Bead roll could indicate setup problems in a mill where there are uneven forces on the tube that causes a gradual twisting.  Often, this is avoided by placing the weld box as close as possible to the forming rollers.  However, if a roll still exists in the tube beyond the weld box, the tube may be later rejected as downstream processes will not be able to process a twisted tube properly. In extreme cases, it could cause problems with bead removal later down the mill.

The Bead Roll angle is measured based on the midpoint between the left edge and right edge of the bead width.  The difference between the midpoint position and a vertical axis through the center of the tube defines the angle of the bead roll.  The actual angle also relies on using the ideal diameter of the parent material for calculation. 

May 13.14 Blog Bead roll resized 600 

The Bead Roll Measurement, where “θ” = the measured angle.

 

How the WI2000p System Measures the Bead Roll

Xiris Automation Inc. has developed a non-destructive inspection system called the WI2000p Weld Inspection System. The WI2000p  includes  a laser line and a camera whose optical axis is offset to the axis of the laser line by an “offset angle”.  The WI2000p creates a visible cross-section of the tube by projecting the laser line on to the tube and capturing an image of the line using the camera. The resulting image shows a  profile of the tube surface as if it were cut in cross section.  If a tube is ideally round, the laser image will represent a section of an ellipse and any anomaly such as a bead roll can be mathematically detected. 

The WI2000p bases all of its measurements on the differences between the actual laser profile line seen by the camera, and the ideal mathematical profile based on the tube parameters.  By knowing the position of the actual laser profile, the ideal profile, and the size of the pixels in the image, the WI2000p can detect subtle bead rolling that often escape detection by other quality tools such as Eddy Current testing, or Ultrasonic Testing techniques.

 

Conclusion

A new technique for detecting bead roll on welded Tube and Pipe has been developed by Xiris and is known as the WI2000p weld inspection system.  The WI2000p system is a laser based inspection system that is capable of detecting bead roll immediately after welding to alert the operator of a defect in time to minimize rejects.  The result is improved quality, fewer field defects and a more reliable method for the operator to optimize the welding process.

Topics: quality control, weld camera, weld inspection, Laser welding, image processing, High Dynamic Range, Tube and Pipe welding, laser-based monitoring, Pipe Cladding, welding defect, bead roll

Labelling Your Weld Videos with Production Weld Data

Posted by Cameron Serles on Tuesday, May 06, 2014 @ 04:06 PM

A Weld Camera used for remotely viewing welding processes can become an even more powerful in-line monitoring tool with the addition of real-time annotation of production data into the recorded video.  

When connected to a welding power supply, a Weld Camera system such as the Xiris XVC-O can acquire production data and write it to the exact video frames when it is acquired.  By synchronizing the writing of the actual weld power supply data to the video frame with the physical image of what is happening with the weld, operating personnel are able to perform more detailed analyses of recorded welding parameters during welding or after the weld is completed.

Annotating Weld Videos

 

The integrity of every weld can be ensured when the weld video is recorded with annotated data, such as the following:

  • Weld power profiles (welding voltage, current, conductance)

  • Pulse Mode, Frequency

  • Type of Welding

  • Material

  • Travel Speed

  • Force and displacement profiles

  • Time and Date Stamp

When it is enabled, the XVC-O View Camera can automatically embed a label into the bottom of the recorded video with multiple sets of information sent to it from the welding power supply.  During the welding process, welding anomalies can be seen as they occur to stop and fix the process.  After the weld, any anomaly in the weld process can be reviewed in the recorded video to see exactly at what level the system parameters were set when an observed problem took place.  

The net result is that the operator is able to maximize the amount of information the recorded weld video provides with simultaneous image and data recording.

Benefits:

  • Make more informed quality control decisions.

  • Improve your welding processes by discovering what parameters make good and bad welds.

  • Rapidly determine the optimum power settings to use to get the best quality welds.

  • Troubleshoot set-up problems and machine malfunctions immediately.

  • Provides empirical information matched to a video log about the welding process.

 

Conclusion

If weld quality is of utmost importance, the use of recorded weld videos with labelling helps to ensure your welds are in-process, stable and repeatable.


Topics: remote monitoring, weld camera, image processing, Welding Process, weld video