The Xiris Blog

Monitoring Tube and Pipe Production to Find UNDERCUT Defects

Posted by Cornelius Sawatzky on Tuesday, March 18, 2014 @ 12:10 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 mainly in Laser and Plasma welded Tube manufacturing: Weld Bead Undercut. 

 

The Undercut Defect

The undercut defect is primarily a result of laser or plasma welding processes.  It may form if the laser beam or plasma arc is too far off center of the ideal welding zone of the tube material.  Undercut is actually a non-melted, non-welded area of the bead that can occur on one or both sides of the bead.  It looks and behaves like a crack along the bead, creating a very weak point on the tube cross-section.  Undercuts are detected as sharp, narrow negative drops in the actual profile (where at least one side of the undercut must have a high deflection derivative, or near vertical slope) that happen close to the edges of the bead.  The absolute value of the biggest negative drop found is reported as the height of the undercut.

Mar 18.14 Blog Undercut

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


How the WI2000p System Measures the Undercut 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 Undercut 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 Undercut profile defects that often escape detection by other quality tools such as Eddy Current testing, or Ultrasonic Testing techniques

 

Conclusion

A new technique for detecting Undercut on laser or plasma 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 Undercut defects 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, undercut

Monitoring Tube and Pipe Production to Find MISMATCH Defects

Posted by Cornelius Sawatzky on Tuesday, March 04, 2014 @ 12:55 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 Mismatch. 

 

The Mismatch Defect

The Mismatch defect is caused by uneven joining of two edges of the tube material strip before welding. Mismatch is a vital parameter to monitor for all tube and pipe fabricators, regardless of which side is higher. This is because many mills employ a grinder or scarfing process to remove any excess bead that is out of round.  However, if mismatch occurs prior to welding, once the tube bead has been removed, part of the wall on the high side of the mismatch may get removed as well, causing significant thinning of the tube wall or leave a step on the lower side after grinding the weld area.

Sometimes the actual welded tube wall thickness in the area of the bead becomes smaller than the original tube wall thickness. This is a result of processing steps other than material removal, such as corrugation or bending of the tube, which can create additional potential failures if a Mismatch defect is also present.

Mismatch is calculated as the absolute value of the radial difference between the two reference points where the weld bead meets the parent material. The mismatch calculation uses the current roll angle to compensate for the bead roll, as such:

 Blog 140304 students resized 600

 

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

 

How the System Measures the Mismatch 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 Mismatch 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 Mismatch profile defects that often escape detection by other quality tools such as Eddy Current testing, or Ultrasonic Testing techniques

 

Conclusion

A new technique for detecting Mismatch 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 system that is capable of detecting Mismatch defects 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

Better Images, Better Instruction, Better Welding Students!

Posted by Cameron Serles on Wednesday, February 12, 2014 @ 03:50 PM

Training a new group of welding students can have a number of challenges for even the best instructors: getting all the students around the weld head to be able to see what is going on; a limited number of hours the instructor has available for actually performing the welding; how to see all the features of the weld arc as well as the background information, and how to make sure that all students are marked fairly and objectively. 

When educating welding students, providing them with the ability to view the detail of the weld tip as well as the environment around the weld tip (such as the weld seam and weld pool) is important for them to learn all the parameters of the welding process.  To overcome the visual monitoring challenges created by the presence of a very bright light source (the weld arc), as well as dark areas in the image (the background around the weld tip), a camera with a wide dynamic range of imaging is required.  Reliable visualization of the environment around the weld tip is necessary to control and adjust the welding process found on most modern welding processes.  In addition, the ability to record video and play it back to the students can provide multiple benefits for teaching and correcting welding techniques.

 Blog 141212 students resized 600

Image courtesy of Casper College

They Can’t All See the Details…. 

New developments in electronics has led to the creation of a new type of camera that is able to accommodate the full range of light present at a weld head during welding, allowing welding to be taught in a way it has never been taught before!

By providing a good quality image of the weld tip and background, welding instructors and their students can remotely monitor a weld demonstration and record the results for off-line feedback.  By using a camera to view the weld demonstration, the students can verify that the tip is in position and that all the welding inputs (welding wire, shielding gas, etc.) are being properly fed.  Because the area around the weld demonstration is typically quite congested for class sizes more than a few students, using a camera mounted at the welding tip allows the students to clearly view the welding process remotely.  The video can also be replayed back, off-line in the classroom for instruction, marking or review purposes. 

 Blog 141212 xiris resized 600

The Solution: a Xiris XVC-O View Camera for Teaching Welding

 Conclusion

Using a View Cameras in the classroom to teach welding results in:

  • —  A more Enjoyable Learning Experience for the Students
  • —  Less Time Required to Achieve Results
  • —  Reduced Material Consumption
  • —  A Video Library of Standard Applications for Review / Consulting / Analysis
  • —  Easier to Explain New Welding Techniques
  • —  Better Support for Students’ Technical Projects
  • —  Research Tool

Join the growing number of Welding Educational Institutions who have added a Xiris XVC-O View Camera to their classrooms. Improve welding instruction and achieve the numerous benefits!

To read educator's personal testimonials below

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For more information on how Xiris Weld Cameras can augment your welding education program, please visit Xiris.com 

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Topics: remote monitoring, weld camera, weld inspection, Laser welding, Machine Vision, image processing, field of view, welding instruction, Education, High Dynamic Range, laser-based monitoring, image contrast

The Technology Behind Every Xiris System

Posted by Cameron Serles on Tuesday, January 21, 2014 @ 03:42 PM

Every machine vision system developed by Xiris is based upon an internal image processing library developed by Xiris over a 20 year period including thousands of hours of coding and testing.  The library has been built up to include a number of key algorithms to perform specific imaging tasks, and includes a number of tools created for maximum specification.

 Pattern Match Tool

Figure 1: This image demonstrates the capabilities of the Pattern match tool

The Edge Tools are used to very precisely locate single edges or edge pairs in a straight line or along an arc.  Best used for precisely gauging the distance between two edges or object location (finding one or two edges precisely to locate a corner, or feature), the software has been scientifically proven in a lab environment to be accurate to better than 1/20th of a pixel.

The Blob Tool is used to perform shape analysis of randomly oriented objects in an image with over 60 different measured features.  It can be used to determine if object meets specific criteria with individual thresholds available for each parameter to quickly select the features of interest, including: Area, Perimeter, Equivalent Diameter, Centroid, Orientation, Second Moments, Bounding Box, Circularity, Eccentricity and many others.

The Pattern Match (or Search) Tool, as shown above, is used to perform pattern matching by locating two dimensional objects in a very accurate manner (1/4 pixel or better).  The Pattern Match Tool is very useful when trying to find an object in a complex scene. Additionally, this tool can be used to determine how well an object matches its ideal, or golden part. 

Used to identify lighting variations, the Light Meter (or Histogram) Tool monitors overall intensity changes or simple part presence. Another important application of this tool is the modification of the Brightness or Contrast of the overall image.

Print Inspection uses a golden template pattern, built over a series of taught images, to compare with the image under inspection.  The Euclidean distance between each overlaid pixel is analyzed to determine if the image under inspection meets with predefined defect criteria.  During the teaching phase, the tool automatically determines appropriate inspection thresholds for each pixel.

Color Tools can be used to verify or recognize a region of color on a component by comparing the candidate color to a series of pre-taught, or known colors.  The color processing can be done inRGB (Red, Green, Blue), HLS (Hue, Luminance, Saturation), CMYK (Cyan, Magenta, Yellow, Black), XYZ or other color spaces.  These tools are often used for product identification, print image quality, feature analysis.

Symbology Tools help read or verify various types of symbols, including multi-format 1-D and two-D bar codes, as well as Optical Character Verification and Recognition.  Characters can be verified or recognized down to 24x24 pixels in size.

Other tools in our software package include Temporal Tools, which can track position over time, a number of Surface Inspection tools, which range from feature detection to defect classification, and 3D Imaging with the use of Laser Triangulation, used to extract the 3-dimensional shape of a surface

Our other Image Processing Tools are used to enhance an image for the benefit of an operator, including morphology (shape based processing such as erosion/dilation or opening/closing), and neighborhood processing using convolutions, including: Sobel, Averaging, Sharpening, Low Pass, Median, Watershed, and others.

All of these tools were created to help the operator make better decisions based upon what they are able to monitor. By using its own software imaging library in its machine vision systems, Xiris is able to provide custom algorithms to suit some very specific market requirements, achieving greater speed and performance benefits that would be otherwise unavailable were a general purpose imaging library to be used. The customizable nature of this software toolkit makes a Xiris system essential for a variety of applications. 

 

Have an application that could benefit from these tools? Contact us, we always welcome the opportunity to discuss new initiatives! 

 

Topics: remote monitoring, camera selection, quality control, weld camera, weld camera, weld inspection, Machine Vision, image processing, field of view, High Dynamic Range, laser-based monitoring, image contrast

Overcoming the Challenges of Laser Beam Welding

Posted by Cameron Serles on Friday, October 25, 2013 @ 09:19 AM

An increasing number of tube and pipe fabricators are turning from conventional plasma and GTAW (TIG) welding to laser beam welding (LBW), which can provide higher welding rates, stronger welds, and deeper, narrower keyholes.

But there’s a tradeoff to the advantages of LBW systems—the resulting need to improve monitoring of the edge presentation and seam location.

Just as with GTAW and plasma welding, the strip edge presentation and seam location relative to the weld head must be controlled to minimize defects such as mismatch, edge wave, edge gap, and seam wandering. But because a laser beam spot is about 10 percent the size of a GTAW or plasma arc, achieving this control is much more difficult in LBW.

The Advantages of Laser Beam Welding

There are clear and compelling reasons for the increased popularity of LBW among tube and pipe fabricators.

Speed

LBW results in increased productivity for the fabricator because it can be 50 percent or more faster than conventional welding techniques, if the laser is appropriately sized and fiber lasers are used.

Power density

LBW systems have greater power density than GTAW or plasma welding systems. The heat in a laser system concentrates into such a small spot that it forms a keyhole weld, which generally extends through the entire thickness of the material and has a narrow heat-affected zone.

The capability for a deeper, narrower weld is valuable in many applications, and the narrow heat-affected zone results in a stronger weld because less of the parent material is distorted or changed in the weld heat zone.

The Challenges – How to Achieve Greater Precision

While the narrower heat-affected zone of LBW creates stronger welds, the small spot size makes it difficult to keep the laser on the seam as the seam wanders from left to right, requiring very precise monitoring to keep the seam on track.

Laser-based Weld Inspection Systems, such as the Xiris WI2000p, have proven to be an effective way to monitor if the seam is out of alignment. Using a triangulated laser and camera solution to monitor the weld seam, the typical laser-based Weld Inspection System can accurately track the seam over an area of 25 mm (1”)—enough to compensate for seam wandering in properly maintained mills.

And once the Weld Inspection System has been taught the correct weld parameters, it monitors the process and alerts operators when parameters are exceeded.

Weld Cameras are another tool that progressive tube and pipe fabricators are using to enhance their monitoring of LBW. A Weld Camera with High Dynamic Range imaging—such as the Xiris XVC-O—can allow operators to watch the laser beam process in real time, with clear visibility of the entire brightness range of the weld scene. This visibility allows operators to use their judgment and experience to make adjustments that improve quality and productivity during production.

 

Image of laser cladding captured with Weld Camera with High Dynamic Range imaging.

Laser Cladding Image From XVC-O

 

Conclusion

The advent of laser-based welding processes in tube and pipe production brings a number of advantages to the fabricator. However, with those advantages, there is a need for enhanced monitoring because the laser weld is so small.

Laser-based Weld Inspection Systems provide a useful way to monitor the weld quality after the fact and Weld Cameras with High Dynamic Range imaging allow an operator to see all the details of the weld and its background during the process to provide instant quality and process control. 

Topics: weld camera, weld inspection, Laser welding, laser-based monitoring

Why Cameras Are Needed for Fiber Laser Beam Welding

Posted by Cameron Serles on Tuesday, October 22, 2013 @ 06:41 PM

The emergence of fiber lasers as a viable alternative to CO2 lasers in laser beam welding (LBW) is exciting for tube and pipe producers, largely because fiber lasers don’t require the use of helium.

Helium is necessary in CO2 LBWwhich is easily the most predominant LBW method—because even though the process is called simply CO2, the resonator gas includes helium. Helium is also needed as a shielding gas. 

The price of crude helium has nearly doubled in price in the past 15 years, and the cost of grade-A helium has quadrupled—so being able to eliminate the use of helium has grown considerably in importance.

Fiber lasers also reduce electricity use because they run more efficiently than a CO2 laser (30 percent compared to 5-10 percent).

For tube and pipe producers, LBW has several important advantages over conventional GTAW and PAW— higher welding rates, stronger welds, and deeper, narrower keyholes. For fabricators already using LBW—or considering moving to LBW—the availability of fiber laser technology offers the potential to gain these advantages at lower cost.

The Challenge

The problem for tube and pipe producers is that fiber lasers don’t eliminate the primary challenge of LBW—compared to GTAW or PAW, it requires significantly better weld monitoring because of the precision of the process.

Just as with GTAW and PAW, the strip edge presentation and seam location in LBW must be controlled to minimize defects such as mismatch, edge wave, edge gap, and seam wandering. However, because a laser beam spot is about 10 percent the size of a GTAW or PAW arc, achieving this control is much more difficult.

While the narrower heat-affected zone of laser welding creates stronger welds, the small spot size makes it difficult to keep the laser on the seam as the seam wanders from left to right. It requires very precise monitoring to keep the seam on track.

Achieving Greater Precision

Fortunately for tube and pipe producers, weld monitoring technology has improved to keep pace with LBW advancements such as fiber lasers.

Laser-based Weld Inspection Systems, such as the Xiris WI2000p, have proven to be an effective way to achieve the enhanced process control that LBW demands. Using triangulated lasers and a trailing camera to monitor the weld seam, the weld head in a typical laser-based Weld Inspection System can track the seam over an area of (1”)—enough to compensate for seam wandering in properly maintained mills.

Once the system has been taught the correct weld parameters, it monitors the process and alerts operators when parameters are exceeded.

Weld Cameras are another tool that progressive tube and pipe fabricators are using to improve their monitoring of LBW—allowing for real-time operator monitoring of the process. With a Weld Camera with High Dynamic Range imaging—such as the Xiris XVC-O—operators can follow the process as it occurs, with clear visibility of the entire brightness range of the weld scene, without having to delay the process to change lighting.

This immediate visibility allows operators to use their judgment and experience—which even the best laser seam tracker can’t match—to make adjustments that improve quality and productivity.

Conclusion

LBW offers tube and pipe producers many benefits—and the use of fiber lasers can add to the advantages—but these productivity and quality gains are only possible if the precise LBW process can be sufficiently controlled. This requires advanced weld monitoring solutions, such as Weld Inspection Systems to automatically track the seam and Weld Cameras that allow operators to exercise in-process control. 

Topics: weld camera, Laser welding, Tube and Pipe welding, laser-based monitoring

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