Orientation and counting of electronic components
In today's electronics industry, the reduced geometries of high-volume components, coupled with ever-increasing demand for faster customer turnaround times, has led to a growing need for automated packaging solutions. While the accurate placement of, and accounting for, thousands of tiny components into packages may seem trivial, the time it takes component manufacturers to perform these packaging tasks without automation can be a bottleneck to business growth. This is particularly true with companies that build components based on customer specifications.
New Jersey-based Compex Corporation is a case in point. The company manufactures single layer components that are used in high frequency RF, microwave, telecommunications and fiber optics products. More than 10 million components are produced annually at the company's 16,000 square-foot, state-of-the-art manufacturing facility in West Berlin, and most are built, packaged and shipped to overseas customers on very short notice.
To increase output and accelerate delivery time, Compex has recently implemented new automated inspection systems based on compact machine vision sensor technology.
"Historically, packaging has been one of the major delays for us in getting product out the door," said David Gordon, General Manager of Compex. "A lot of our time was spent manually inspecting components to ensure they were oriented properly before being placed into packages, and later counting components in packages to make sure customers were getting exactly what they had ordered. For a rush order of 25,000 pieces, for example, we'd need multiple operators in the packaging line for two or three shifts just to ship within a few days notice.
Gordon added that Compex competes directly with much larger component suppliers, and maintaining competitiveness is directly tied to delivery times. "Our goal was to be able to start shipping within one week for any order we received."
The new automated inspection systems have enabled Compex to not only reach its one-week turnaround goal, but to also increase production yield and redeploy nearly 80% of the resources previously spent on packaging to other areas of the operation.
Compex is no stranger to machine vision technology. In fact, the company had implemented a proprietary vision inspection system in 2000 to ensure components were oriented the correct way before being robotically loaded into packaging. The system, however, had a number of key limitations that prevented it from speeding the packaging process up.
For example, the vision software tools were not sophisticated enough to handle wide variations in part appearance. Different types of substrate materials, including quartz and ceramic, would confuse the vision system and cause failures. High reflectivity of the components - most of which are gold-plated - was also problematic for the system. Additionally, various marks and scratches on the surfaces of production feed track, caused by normal wear and tear, would inevitably show up in inspection scenes. Unfortunately, the vision system had trouble ignoring this type of "background noise" and additional failures resulted.
"The vision system we had been using was basically just a pixel counting system, so even if a component was mis-oriented or off-center, the system would accept the part if the pixels added up," explains Gordon. "We had to constantly tweak the light sources for this system, and ultimately the systems limitations demanded an upgrade.
Acknowledging the limited reliability and throughput of the current vision equipment, Compex shifted to a semi-automated process to be used with new pick and place equipment. The vision system would capture and display an image on a monitor, and an operator would manually make a go/no-go decision based on what he saw on the screen. If a component was not oriented properly, the operator would physically remove and recycle the component back into a vibratory feed bowl. If orientation was correct, the operator would hit a button on a controller to activate the robot - a multi-axis Cartesian model - which would pick the component off the feed line and place it into the packaging.
"Ironically, bringing humans into the inspection process with new pick and place equipment was a high-speed alternative to relying on the vision system itself," said Gordon, "but we believed full automation could take us to the next level".
The company was also spending considerable resources on another stage of the packaging process: counting. Thousands of components placed onto film carriers needed to be manually counted before the packages were shipped. The process, according to Gordon, was slow, tedious, and error-prone.
"One operator could spend 20 minutes or more counting a single package, and there were often inaccuracies. Errors were unacceptable, since some of our customers would report back to us that two components were missing out of a shipment of 80,000. The process was a nightmare for us, and just one more thing slowing us down."
With far too much labor tied up in manual inspection tasks, Compex began its quest for new automation systems that would streamline the component packaging process and reduce the need for operator assistance.
Vision comes full circle
In early 2005, the company learned about a local machine builder/system integration firm that specialized in vision-based inspection solutions. The company, Serview, appeared to have the right combination of technological know-how and industry experience required to improve Compex's packaging process.
"We have people internally who could have designed a new system, but there is no substitute for the kind of expertise Serview brought to the table," said Gordon. "Plus, they were right down the road from us which really helped move things along."
According to Serview engineering manager Brian LeBlanc, the objectives of the project were clear at the outset. "Compex wanted to improve output and reduce turnaround time without changing the number of personnel. Instead of having multiple operators working in the packaging area, they wanted to have a single person oversee a number of automated systems and use the remaining manpower elsewhere. With the right tools and proper system design, we had a high level of confidence that we could help Compex exceed their production goals and take their business to the next level."
Although Compex's experience with machine vision had been less than perfect, company engineers realized that the technology was nonetheless a necessary part of their automation strategy. Gordon and a few associates flew to Boston in 2004 to attend the Vision Show East (sponsored by the Automated Imaging Association), where they became acquainted with some of the latest and most advanced vision solutions available at the time. During the show, they connected with Cognex, which was showcasing its line of In-Sight® vision systems.
Although Gordon and his team had been impressed by the capabilities and relative ease-of-use the Cognex products seemed to offer, they ultimately deferred to Serview on vision system selection based on the firm's years of experience. As it turned out, Serview was a Cognex Certified Vision Integrator and designed a majority of their systems around Cognex technology. "We felt comfortable working with the equipment Compex had already purchased, retooling it with new machine vision and PLC controllers. We were able to interface the vision inspection with the PLC for machine and control functions to provide a fully optimized solution using off the shelf components."
While many of the systems Serview developed over the years incorporate PC-based vision systems, the primary inspections Compex needed to accomplish - component orientation verification and counting - were both single-camera applications. For this reason, Serview integrators selected In-Sight vision sensors as the vision platform of choice.
"We wanted to simplify integration of the vision system as much as possible," explains LeBlanc. "In-Sight had the right toolset for us, and because it's a standalone form factor, it runs without a PC even being needed for anything other than product changeover or viewing inspection results.
Specifically, the team chose an In-Sight micro for the orientation system, which is a low-cost, general-purpose vision sensor, and an In-Sight 5000 series for the counting system, which is a high-resolution vision sensor series featuring 1600 x 1200 pixel CCD sensing. Both sensors incorporate all image processing hardware, software, and communications in a compact, self-contained package. The fully integrated design significantly reduces the time and expense associated with integrating vision into the production line.
At Compex, vision technology had now come full circle as Serview began work on developing the new systems.
The main components of the orientation system designed by Serview include the In-Sight micro vision sensor, Compex's existing Cartesian robot, a vibratory feed bowl and track, an air blow off for part rejection, and an Allen-Bradley Micrologix PLC. A Cognex I/O module was used to link to link the In-Sight sensor with the PLC, and a Dell PC is used by the operators to monitor the inspection during runs and perform product changeover, and run the In-Sight Explorer vision software application, as well as a custom graphical user interface.
One of the main challenges in designing the system was configuring lighting and optics so the full range of Compex components could be inspected without making any set up changes.
"We had to get the lighting and lensing repeatable across all components, which took a fair amount of development time to tune the inspection software to match the full range of part types and materials, along with normal part variations that were deemed acceptable," said LeBlanc. We felt lighting was one of the deficiencies of the previous vision systems, and we knew that this area would need to be engineered carefully to make the systems easy to use and to allow for rapid and repeatable changeovers. Since changeovers are frequent, it was desired that a single lighting setup would work across all part types. This goal was accomplished and product changeovers are done by loading product configurations with no optics or lighting adjustments.
The Serview team experimented with various configurations on the range of part types and materials and ultimately settled on a combination of Xenon strobe and fiber optic lighting. This combination provided white light at a short pulse width, along with very tightly synchronized image acquisition and strobing via the Cognex I/O module, provided proper image formation for the various components types.
The vision application, which involves a two-step inspection routine, was developed using In-Sight Explorer software. The software includes a suite of development, management, and monitoring tools to make the entire vision application development cycle easy and fast.
The vision sensor first verifies the orientation of the component, and then measures critical dimensions. The dimensional checks include measuring the outer dimension of the components and the dimensions of the metal coating.
Serview Director of Operations Steve LeBlanc explains, "Even though Compex uses very accurate dicing saws, tolerances are still an issue. Components as small as 0.015" square are viewed under high magnification using microscope lenses, and we make dimensional measurements as part of the inspection process. So, by measuring the parts during the orientation stage, we were able to give Compex another safeguard. Any defective parts that are chipped or are out of dimensional tolerance that were missed in previous inspection steps are rejected by the system. This gives an extra level of quality inspection that finds more defects than we originally expected to see."
Both the orientation and dimensional inspections were set up using various edge detection and histogram vision software tools, which are part of the standard In-Sight vision tool library. A customer graphical user interface makes it a snap for operators to select different inspection "jobs" during part changeover. According to LeBlanc, an operator can take the system offline, select the new job, and put the system back into run mode within 10 seconds.
Serview engineers also designed a built-in calibration program into the In-Sight application. This allows operators to easily reset the camera lens magnification within five seconds if the lens goes out of adjustment.
While the system is completely automated, Compex felt it was still important to have the option of using operators to inspect the components if, for example, computer systems shut down, or new component parameters had not yet been programmed into the vision application. For that reason, Serview designed a manual-mode feature into the system. Manual mode works in a similar fashion to their previous operator-assisted vision system, whereby an inspection image appears on the screen and the operator makes the pass/fail decision.
The orientation system is located at the end of a linear feed track, onto which components are fed from a vibratory feed bowl. Once a component moves under the In-Sight micro sensor, which is mounted approximately six inches above the track, an image of the component is captured and sent to the In-Sight's on-board processor where the vision tools analyze the image. Operators can view the inspection in real-time as it occurs.
If the orientation is correct, the PLC signals the robot to grip and place the component onto a film ring or waffle pack. The entire inspection and placement time, from image acquisition of a good chip to robot placement, is approximately 300 milliseconds. The Insight vision system is faster than the material handling, so the process is limited by material handling speeds.
If there is a problem, such as the component being upside down or stacked on top of another, the vision sensor fails the part, a red LED appears on the inspection monitor, and the part is automatically recycled back into the feed bowl. Only good parts are accepted and placed by the system.
Inspection that really counts
Further downstream, packaging containing thousands of components travel through Compex's new automated counting system just before they are shipped. This system, according to Gordon, was a necessary tool for a number of reasons.
"Our guys were trying to do a manual count of thousands of pieces, which could take one person 20 minutes," said Gordon. "In addition to being time consuming, it was very difficult to get 100% accuracy, which our customers demand."
Unlike the orientation system, the counting system is a tabletop, standalone system that requires no PLC. A single-camera application as well, Serview again chose to incorporate an In-Sight vision sensor for the job. However, this time the engineers selected the In-Sight 5000 series, which contains a high-resolution (1600 x 1200) model.
"One of the key design considerations with this system was building in the flexibility to automatically count smaller and smaller components in the future," said LeBlanc. "The high-resolution In-Sight was a good solution in that it would give the company this leeway."
In addition to the In-Sight sensor, the system consists of a combination of LED backlighting, which works well to image the components, and a Dell PC, which runs a custom-designed Visual Basic program.
The user interface for this application was developed using Visual Basic said LeBlanc. "The application we wrote gives the user just a couple of selections on the user interface to simplify the set up and operation of the system. For example, the operator can just pick a given job from a drop-down list and all various set-up parameters for that job such as brightness settings change dynamically. The application user interface is simple enough that most operators feel comfortable using the system right away. The system is flexible, and we have already added new products as Compex adds them to the mix".
The In-Sight vision tools used to perform the counting operation include a combination of blob and grayscale morphology pre-processing tools. According to LeBlanc, getting the blob tool to run effectively was a challenge due to the fact that the components are so small and tightly laid out on the package with very little separation between components. For that reason, images are first pre-processed with the morphology tool, which provides the necessary feature separation for blob to work reliably.
Once a part type has been selected from the Visual Basic user interface, operators select "live mode" which allows them to manually align the package with a template overlay. The operation is viewed on the PC monitor. Once the manual alignment is performed, the operator then selects "Count" which triggers the In-Sight sensor to acquire the image and perform the count.
As the sensor counts, it also verifies that the components are the correct size and that components are not touching. It typically takes less than 20 seconds perform the whole sequence of alignment and counting, the system reports the number of components in the package and indicates if there are any problems. The image of the package is saved to disk and count data is saved in a SQL database, giving Compex a permanent record of every package they ship.
"So far all reports are that the system is 100% accurate, and we found up front testing really paid off as we have not had to make any changes on this system after it was delivered. We're in the process of working to integrate the vision count data so it is printed onto a label with bar code and serial number of the package," said LeBlanc.
Through careful system design and implementation, Serview has helped Compex make dramatic improvements to its component packaging process without changing the number of personnel at the West Berlin facility. The systems have eliminated a major bottleneck in Compex's ability to ship quickly, and labor savings in the packaging area alone are approximately 80%.
"We knew that implementing these systems successfully would be challenging, as previous attempts at developing these systems did not succeed." LeBlanc said. "Serview engineers focused on working with Compex to understand their processes and part types, and this allowed us to design and tune the lighting and software to make these systems work. We worked with them to make sure the vision systems could cover the full range of products, and it is really satisfying to see them grow and be successful using our equipment."
Compex and Serview are currently working together to identify additional areas of the manufacturing process that could benefit from automated inspection, including component surface defect inspection.