Vision of success

Producing 25,000 components in one week throws up its own unique challenges, especially when those parts have reduced geometries but need to be made to a high specification.

Compex Corporation is familiar with the practicalities of shipping high volumes at short notice and its route to a successful machine vision inspection system has removed uncertainties inherent in automated packaging.

Compex makes single-layer components used in high-frequency RF, microwave, telecommunications and fibre-optics products. More than 10 million of these components are built, packed and shipped at its facility in West Berlin, New Jersey.

To increase output and accelerate delivery time, Compex has implemented new automated inspection systems based on compact machine vision sensor technology.

David Gordon, general manager of Compex, said: ‘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. For a rush order we would need multiple operators in the packaging line for two or three shifts to ship within a few days’ notice. Our goal was to be able to start shipping within one week for any order we received.’

With new automated inspection systems, Compex has achieved this one-week turnaround and increased production yield.

The company had previously implemented a flawed proprietary vision inspection system to ensure components were oriented correctly before being robotically loaded into packaging.

The vision software tools were unable to handle variations in part appearance. Substrate materials, including quartz, would confuse the vision system and cause failures. Highly reflective components also posed problems. Additionally, marks and scratches on the surfaces of production feed track, caused by normal wear and tear, would appear during inspection. The vision system struggled to ignore this type of ‘background noise’, resulting in additional failures.

Gordon said: ‘The vision system we had been using was basically just a pixel-counting system, so even if a component was misoriented or off-centre, the system would accept the part if the pixels added up.’

Compex then changed to a semi-automated process to be used with pick-and-place equipment. The vision system would capture and display an image on a monitor, and an operator would manually make an accept/reject decision based on what was 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 push a button on a controller to activate the robot, which would pick the component off the feed line and place it into packaging.

Components placed onto film carriers then needed to be manually counted before the packages were shipped. The process, said Gordon, was slow and prone to error.

Compex started to look for new automation systems that would streamline the component-packaging process and reduce the need for operator assistance.

In 2005, Compex learned about Serview, a Cognex-Certified Vision Integrator that designed many systems around Cognex technology.

Brian LeBlanc, engineering manager at Serview, said: ‘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 optimised solution using off-the-shelf components.’

The primary inspections Compex needed to accomplish were single-camera applications, which led Serview to select In-Sight vision sensors as the vision platform.

The team chose an In-Sight 1000 for the orientation system, and an In-Sight 5403 for the counting system. Both sensors incorporate image-processing hardware, software, and communications in a single package.

The main components of the orientation system designed by Serview include the In-Sight 1000 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 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 was configuring lighting and optics so the full range of Compex components could be inspected without making any set-up changes. LeBlanc said: ‘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.’

The Serview team chose a combination of Xenon strobe and fibre-optic lighting. This combination provided white light at a short pulse width, along with very tightly synchronised image acquisition and strobing via the Cognex I/O module.

The vision application, involving a two-step inspection routine, was developed using In-Sight Explorer software, which includes a suite of development, management, and monitoring tools to simplify and speed up the vision application development cycle.

In operation, the vision sensor verifies the orientation of the component, and then measures critical dimensions.

LeBlanc said: ‘Components as small as 0.015in2 are viewed under high magnification using microscope lenses and we make dimensional measurements as part of the inspection process. Any defective parts that are chipped or are out of dimensional tolerance that were missed in previous steps are rejected.’ Orientation and dimensional inspections were set up using various edge-detection and histogram-vision software tools in In-Sight’s tool library.

Compex felt it was still important to have the option of using operators to inspect the components if 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 that works similarly to the previous operator-assisted vision system.

Following successful integration of the system Compex and Serview are working to identify other processes that could benefit from automated inspection.