Oct. 3, 2014 - A large global automobile manufacturer has over 300 machine vision systems in operation, generating 200,000 process images per day, at a plant building 6-speed front wheel drive transmissions. The vision systems improve quality by identifying problems as soon as they occur to prevent defective parts from reaching the customer. The vision systems also provide evidence to prove that plant was not at fault in many situations where it would otherwise be assessed charges to due to a warranty claim.
In the past, the transmission plant stored images on local personal computers but lost many images because a PC stopped working. To prevent an incident like this from happening again, the plant installed a central image storage system. This system saves thousands of images per minute with associated data and provides diagnostics, such as when images are not being stored, or when rejects reach a predefined rate. Users can now search for, view and export images from any operation in the plant from a single web interface. This approach helps leverage the benefits of machine vision inspection to provide further improvements in quality and warranty costs.
Automotive transmission manufacturing challenges
The automobile manufacturer invested $323 million in the 2 million square foot transmission manufacturing plant with approximately 2,000 employees. Automotive transmissions are very complex assemblies that can be rendered defective by a single faulty component or incorrect assembly operation. The cost of repairing and replacing a defective transmission can easily run to hundreds of times the cost of the component that caused the problem. This explains why transmission plants have traditionally deployed hundreds of inspectors who were assigned to manually view each of the many parts and assembly operations involved in building the final product. This approach was expensive and dependent upon the diligence and attentiveness of the inspectors. Another limitation was that if a defective transmission was produced, it was always difficult, sometimes impossible, to determine the root cause of the defect, and more often than not,the transmission plant was assessed charges related to warranty claims.
Over the past decade, the vast majority of transmission plants around the world have transitioned to machine vision inspection for error-proofing the assembly process. The transmission plant described in this article currently uses more than 300 cameras, and is in the process of increasing the number to over 500 that will be used to verify every step in building its products. Vision inspection improves quality because it is less prone to errors than manual inspection and can also provide substantial cost reductions. When a transmission is returned with a warranty claim, the archived images can be used to determine whether or not the plant is at fault. If the plant has evidence to prove it is not at fault, then no charges are made. Visions systems also aid in preventing defects by providing detailed dimensional information that can be used to identify the root cause of defects and alert engineering to degrading applications and supplier products.
Vision system standardization saves time
The automobile manufacturer that owns the transmission plant makes extensive use of Cognex vision systems throughout its manufacturing operations. Cognex has worked with the automobile manufacturer to develop templates and communications standards that simplify the installation of new cameras. Traditionally, vision systems are periodically tested by running challenge parts with specific defects through the vision system. Time and money is required to produce and store challenge parts and downtime is often required to run them through the vision system. These expenses have been avoided with a new approach in which images of defective parts are stored on a server and can be analyzed to test the configuration of the vision system, all while avoiding the expense of creating, storing and running challenge parts.
The transmission plant uses Cognex In-Sight 5000 series cameras equipped with PatMax part location technology for inspection and also for reading 2-D barcodes on parts. Vision systems with various levels of resolution up to 5 Megapixels are used in different applications. Higher resolution allows a larger field of view, making it easier for the vision tools to accurately find the features of interest on even larger size parts. Cognex DataMan 302 ID readers are used in some 2-D barcode reading applications. These readers utilize the 2DMax algorithm that can handle variations in code marking, codes with damaged Data Matrix clocking or timing patterns and codes degraded during the manufacturing process. Additionally, the plant employs over 50 Cognex Checkers for identifying the presence/absence of transmission components, such as o-rings and seals.
Image storage challenges
The increasing importance of vision inspection makes it essential to retain vision images for use in root cause analysis and to reduce warranty claims. In the past, the transmission plant stored images on PCs scattered through the plant that were used for viewing of local images directly from attached plant floor cameras and also gathering and storing images for later retrieval. These PCs were expensive both in terms of their initial investment and also in requiring maintenance, such as operating system patches, anti-virus updates and repairing hardware failures. The images were transferred via the File Transfer Protocol (FTP) from the camera to the PC. However, there was no feedback loop to determine when the PC stopped collecting images so it was unpredictable whether or not the images would be available when the engineer reached the PC. The dispersed nature of image storage meant that engineers who needed to determine the root cause of a defective transmission often had to visit many different PCs to collect images. The previous system also did not provide diagnostic capabilities, such as providing alerts when quality was degrading, near the point at which defective parts were produced.
To address this challenge, the transmission plant installed the eFlex Vision central image storage solution that provides an integrated environment for managing and retrieving process images. The solution included a Dell EqualLogic storage server with 12 network interface cards and 48 2 Terabyte hard disk drives providing 71 Terabytes net storage space. The plant floor cameras were all modified within two days to FTP files to the eFlex vision server. The file name contains the part number, serial number, station ID, camera ID and a pass or fail field. Every time an image is captured by a camera, the camera notifies the image server. If the image server does not receive the image, an alarm is immediately sent, ensuring that any problem in retrieving images is immediately identified and corrected. The eFlex Vision software and server solution currently has the capability of storing 1,500 images per minute.
Monitoring part quality and vision system functionality
Through a web interface, images can be searched by part serial number, station, camera, pass/fail, retry count and date/time range. Images can be viewed in varying formats such as carousel, grid or gallery, or exported to a zip file with a browser image viewer. The server provides real-time information related to server health, such as hard drive usage, network bandwidth usage, incoming file monitor, non-conforming file monitor, FTP server status and activity monitor. Additionally, the camera connection status, camera image rate, date and time of last file, and other information is monitored. Real-time monitors can be viewed in a dashboard and configured to generate alarms and warnings. The facility has configured predictive reporting and alarming to statistically monitor reject rates, lighting, part marking grade, part positioning and generate warning and alarm events that notify users of degrading conditions at a particular camera.
Another advantage of Cognex vision systems is the Cognex Audit Message service application that runs on a PC and tracks significant events on the camera. When the audit messaging is enabled, cameras send XML formatted messages to the audit messaging service whenever a user logs in, changes a job, puts the camera online or offline and/or changes a parameter. “We are in the process of incorporating these audit trails into the eFlex Vision database,” said Dan McKiernan, President of eFlex Systems. “This information will make it possible to provide alerts if the operating parameters of a vision system are changed anywhere in the plant and also to look back and track changes. As far as we know, no other vision systems offer this capability.”
Due to the detailed nature of automotive transmission manufacturing and the high cost of errors, machine vision has become the key to ensuring high levels of quality and minimizing warranty costs. As a result of installing the image storage solution, the automobile manufacturer has saved time and money in the management of inspection images. When a quality problem occurs or a warranty claim is made, engineers now can quickly find the information they need to find the root cause of the problem. The diagnostics provided on camera operation have reduced the number of false rejects by alerting engineers of problems with vision system integrity, programming and setup.
A block diagram showing the major components of the eFlex system and how they fit together.
Example Differential Inspection Image for correct assembly, gear inclusion and tolerances.
Example Shifter Inspection and Clutch Plate Inspection Images for location, measurement, and presence/absence.
Sample eFlex Vision Software Image Retrieval Screen showing plant images with part number (pun), pass/fail, camera task, date/time, and image type information; with extensive menu (left), advanced search and pull/drill down selection options.
Cognex In-Sight 5000 series cameras equipped with PatMax part location technology are used for inspection and also for reading 2-D barcodes on parts.
About eFlex Systems
eFlex Systems is a recognized industry leader in the design and implementation of advanced technology and world-class assembly optimization solutions for the manufacturing and information technology markets. We can help you achieve the right balance of technology and lean manufacturing principles to meet changing market demands. Serving a global customer base, we continue to expand our production assembly optimization expertise. We rely on our reputation as a world class manufacturing software company and manufacturing consulting firm to both attract new customers and preserve our relationship with existing clients. Our team includes a diverse group of engineers from manufacturing, software and consulting disciplines.
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