3D Inspection Opens Doors for Masonite
Masonite is a global building products company with its corporate headquarters in Tampa, Florida, USA. Operating in over 80 facilities in eighteen countries across North America, South America, Europe, Asia and Africa and with approximately 10,000 employees, Masonite leads the world in manufacturing quality moulded door facings, which they supply direct to door-manufacturing partners across the world. Masonite’s Irish facility in Carrick on Shannon, Co. Leitrim, is the result of a $138 million USD investment and is the second largest facility for Masonite. This state-of-the-art production facility ships door facings to 32 countries.
Door facings with different patterns are produced simultaneously and are required to be automatically classified and sorted into the correct collection bays at the end of the production lines. Incorrectly classified facings must be manually re-sorted. Manual re-sorting is highly labor intensive, resulting in damaged facings and subsequent yield loss.
Masonite Ireland had a legacy door facing inspection vision system that had served its original purpose well, but with the advanced moulding designs and expansion of the door facing business, new vision technology was needed. The existing vision system software contained a library of all possible door facings but could not easily accommodate the addition of new facings, thus requiring specialized programming by engineering personnel. Moving forward, Masonite was keen to apply a vision system solution that would meet their requirements for the foreseeable future. It was also critical that the system would be highly accurate, easy to use, quick for operations personnel to train, and could accommodate the large number of moulded door designs used in production.
Bring in the specialist
Committed to investment in continuous process improvement, Masonite commissioned Alpha Vision Design (AVD), a specialist industrial machine vision company, to work alongside Masonite Ireland engineering personnel to deliver an in-line automatic classification system. The system was required to identify the door facings based on the moulding design and surface texture. Two door facings are pressed side by side, with the different door pattern combinations produced from a large stock of single door facing dies. There are thousands of possible die combinations, so the sorting system was required to accommodate multiple die combinations and frequent die changes.
At the beginning of the production run, the operator trains the system for the first set of facings using a simple training wizard. Subsequent facings would then be automatically inspected and classified. The vision system then communicates with the production line’s control system, routing the classified facing to the appropriate collection bay.
The project posed some interesting technical challenges. Due to the large surface area involved (one door length x two door widths), providing even illumination over the entire surface area was difficult to achieve. Masonite had previously used standard large format, high frequency, fluorescent lighting to illuminate the facings within the defined inspection area. Due to the physical attributes of the door facing (large area, not perfectly flat), conventional lighting was inadequate to provide high quality images for the vision system. As lighting is such a critical component of any vision system, it was recognized that significant improvements in illumination were required for this application.
Also, a robust system was required that could deal with rotation and some bending or warping of the door facings, as the facings can sag where there is no direct support from the conveyor belt. As a result, the pattern profile of the door facing can appear distorted, which typically causes stretching or compression within the acquired image. Standard pattern matching tools based on cross correlation techniques would perform poorly under these circumstances.
Globally, the vast majority of machine vision applications are based on 2D inspection techniques. 3D inspection still remains relatively specialized, although new markets are emerging as the technology matures and gains more widespread acceptance. 3D inspection using laser triangulation is probably the most common platform used today for deploying 3D applications (although many other 3D technologies exist). Lasers, used for illumination, offer cost-effective solutions and are readily available from many suppliers and manufacturers. In addition, laser-based 3D systems are particularly effective for scanning large non-reflective parts with well defined profiles and were therefore well-suited for this vision application.
The system is designed to capture 3D data of the patterns on the facing of the moulded door, using diode laser line generators and a line scan 3D image acquisition camera (supplied by other equipment manufacturers). The laser line generators produce a visible laser line across the width of the double door facing as it travels along the inspection conveyor. Using a shaft encoder, the 3D camera is synchronized with the conveyor speed to capture 3D data at a suitable resolution along the length of the door facing. The 3D camera is configured for a similar pixel resolution for the facing width.
The height sensitive image data is transferred to the PC’s framegrabber via a CameraLink interface to build and create a 2D height profile image (in bitmap format) of the double door facing being inspected. The image is then processed using powerful VisionPro™ software from Cognex. VisionPro offers unrivalled image capture and processing in an easy-to-use format. The advanced PatMax® tool provides the ability to perform unique geometric pattern matching and to classify shapes, even at low contrast, as encountered in this application.
“Smart” 2D vision cameras and halogen lighting are used to provide the required surface texture information, which is integrated into the vision system using digital input signals.
Once Masonite Ireland engineering personnel had completed the specification, design, installation, and commissioning of the 3D and 2D vision hardware, the system was ready to be programmed to extract and process the image information. A custom Graphical User Interface (GUI) was created by AVD according to Masonite’s requirements. The interface was designed for ease-of-use by the operations personnel. It was designed to be uncluttered, and contains a color coding scheme consistent with other systems in place at the manufacturing facility.
As part of the ease-of-use ethos, the number of operational settings required to use the system were kept to a minimum. The system was not an overcomplicated engineering tool that would be limited to programming/configuration by technical or engineering personnel. The delivered system requires less than four minutes for production personnel to train new door facings, and requires little more than the ability to draw boxes and position detection tools.
End user results
Robert Sadlier: Senior Controls Engineer, Masonite Ireland.
“Given the large number of possible die combinations, the large surface area and the relatively shallow moulding depth of the door facings, it was difficult to specify a suitable vision system to capture high quality, repeatable images and to accurately categorize the multitude of door facing combinations.”
“The solution required an innovative approach, which resulted in the integration of previously incompatible hardware and software. Alpha Vision Design was chosen as the system integrator due to their considerable expertise in the specialized field of vision system engineering. They succeeded in bridging the gap between the hardware and software by producing custom interface software, allowing the application to become a state-of-the-art vision system.”
“The Graphical User Interface (GUI), designed in partnership with AVD, has proven to be very intuitive to use. The GUI provides all the relevant information required to determine the performance of the system at a glance, without any specialized knowledge required by operations personnel. Engineering personnel can also debug and maintain the system using more advanced, access level protected features of the GUI. Ease-of-use of the system was a critical requirement, as failure of this facet of the project would have negatively impacted the overall project’s success. Once instructed, our production line personnel train the system for new door pattern combinations, as required, without any difficulty.”
“The advanced functionality of the Cognex VisionPro software contributed significantly to the project’s success, allowing the system to exceed the original User Requirement Specification, providing a sorting accuracy in excess of 99.97% (i.e., less than three in 10,000 are incorrectly classified). Manual re-sorting of product has virtually been eliminated, increasing yield, and allowing operations personnel to perform tasks that add value to the product.”
“The excellent performance of the Cognex VisionPro software, combined with AVD’s vision system expertise, resulted in a state-of-the-art vision system, paving the way for similar projects to be implemented in Masonite Ireland in the near future.”
Alpha Vision Design specializes in the application of industrial machine vision systems for quality control and automation in manufacturing. Our broad range of expertise encompasses systems integration, software development, optics and illumination. With over ten years of experience in vision systems design and application development, Alpha Vision Design is the preferred partner for many leading blue-chip manufacturing companies.