Camera/robot increases quality, reduces initial cost 40 per cent and retool cost 80 per cent

Citation

(2010), "Camera/robot increases quality, reduces initial cost 40 per cent and retool cost 80 per cent", Industrial Robot, Vol. 37 No. 4. https://doi.org/10.1108/ir.2010.04937daf.002

Camera/robot increases quality, reduces initial cost 40 per cent and retool cost 80 per cent

Article Type: Mini features From: Industrial Robot: An International Journal, Volume 37, Issue 4

The Piston Group, located in Redford MI and Liberty MO, builds cooling modules for seven different vehicles. These cooling modules are built on five different assembly lines, each line building more than 50 different variants in sequence to the customers demand. Many different inspections need to be performed on each module including verifying the build variation, checking electrical connections and all dimensional requirements. In the past, inspections were performed in an automatic check station that utilized multiple pneumatic actuated slides that were fitted with linear probes, vision systems and a wide variation of sensors to inspect the different components. The problem with this approach was that each individual slide cost around $15,000 or more, and the slide had to be replaced whenever the corresponding part specifications or design changed.

The conventional approach to replacing the slides with machine vision would have required as many as 30 different fixed cameras, each with special lighting requirements. The Piston Group developed a much less expensive and more flexible solution by mounting a single Cognex®. In-Sight® 5603 vision system on a Fanuc® robot. The robot moves the vision system into position to capture the 30+ images in less than 45 s, completely inspecting the module. The In-Sight vision system can be modified to inspect for future design changes easily with a few hours of programming time. The new inspection system has substantially improved quality by inspecting more points at a higher level of accuracy while reducing initial investment by 40 per cent and retool cost by 80 per cent.

The Piston Group provides sequenced and non-sequenced sub-assembled components for complex modular assemblies. The company assembles modules ranging from front-end cooling systems, suspension and chassis systems, interior systems, and power train systems. The cooling module produced in this application consists of essentially everything between the motor and front bumper: the core support, radiator, electric fan, AC condenser, power steering and transmission coolers, reservoirs, hoses, wiring harnesses, and many other small components. The modules are built in many different configurations. For example, most lines have over 20 different wiring harnesses are used depending in the model and options selected by the customer. The customer sends The Piston Group a daily release that indicates the required front module configurations and their build sequence.

Demanding quality requirements

The quality requirements for the modules are demanding. First, each module must be correctly configured for the vehicle it will be installed on, with the proper wiring harness and other components. Second, many components need to be installed within tight dimensional tolerances. Several hoses and clamps must be installed within 1 mm of a specified location. All electrical connectors must be fully seated and engaged.

In the past, many of these inspections were performed in a check station by mechanical probes mounted on slides. This approach required that a custom slide be designed and built for each dimension that was checked. Whenever the dimension was changed, the slide had to be modified or replaced with a new design. The cost of retooling for all new vehicle model was typically about $150,000 and required approximately two weeks of downtime to retrofit the entire check station. Prior to model changeover, the company would build small quantities of pre-production new model parts and these parts had to be inspected manually due to the station not being changed over. Many inspections, such as determining whether parts were identified and installed properly, were performed by 200 per cent visual inspection by quality engineers. The flexibility of the new system allows for accommodation of both current and new model production, reducing this reliance on visual inspection.

“Every time the customer made a single engineering change, the cost was a minimum of $15,000,” said Kevin Miller, Director of Manufacturing Engineering for The Piston Group. “We wanted to implement a flexible vision system to reduce cost and turnaround time on changes. We also wanted to reduce the amount of required manual inspection to improve quality. The normal practice is to use one camera per inspection point. This approach would have taken up too much space on the existing equipment and the cost was too high.”

Using a single vision system for multiple inspections

Separate cameras have traditionally been used for each inspection point because each point generally requires very specific lighting and camera focal distance in order to achieve the required level of accuracy. Camera speed has also been a concern when considering the idea of using a single camera to take multiple images within a single cycle. But the evolution of Cognex vision system technology makes it possible for a single robot-mounted camera to inspect a large number of points with a high level of accuracy (Figure 1).

Figure 1 Image of bad part on HMI screen

“We worked with the Vision & Traceability Group of McNaughton McKay Electric to identify the right camera for this application,” said Patrick O’Dell, Control Engineer for The Piston Group. “We selected Cognex because its vision systems provide the wide range of tools needed to inspect the many different points involved in this application. Also, Cognex’s PatMax geometric pattern matching tool provides substantial improvements in accuracy by accurately determining the part location. A single Cognex In-Sight 5603 met the requirements of this application by accurately inspecting 30+ very different features in many different locations in less than 45 seconds. Plant wide we are using this camera for more than 90 different inspections”.