Monday, June 18, 2018
Publication Date: 12/1/2008
Archive >  December 2008 Issue >  Special Feature: Test and Measurement > 

Machine Vision Inspection Boosts Production Accuracy
Cognex industrial vision system (in square metal box) is positioned by a robotic arm over parts to be examined. The red light is part of the system's illumination of the test parts.

Intended for automobile equipment manufacturers, the parts manufactured by Meister France are subjected to very strict appearance checks with the aim of completely eliminating defective parts before delivery to customers. This is an ambitious gamble when you are producing almost 40 million parts per year, and a gamble which has paid off largely due to the use of Cognex In-Sight® industrial vision systems.

The Meister Group is a Belgian industrial group which largely caters to the automobile market. With factories in Belgium, France and the Czech Republic, Meister specializes in the mass production of cut steel parts. The challenge facing Meister, whose production units use specialty precision lathes, is that it must manufacture relatively complex parts in mere seconds, all the while guaranteeing the conformity of the parts on delivery without ignoring the essential and continual search for gains in productivity.

In France, the Meister factory is located in Haute-Savoie. It manufactures electric valve parts for automobile equipment manufacturers specializing in ABS braking systems. Nearly twenty-four multi-spindle lathes produce 120,000 parts each day, representing an annual production of 35 to 40 million parts.

The demand for quality is Meister's primary focus; it must avoid the delivery of defective parts to its customers. In a sector where the smallest incident on an assembly line creates exhaustive investigations and leads to complicated and costly procedures for the subcontractor, the search for zero faults is an absolute necessity. However, given the manufacturing techniques used and the demands of mass production, this goal cannot be attained using only machines. A checking and sorting system is needed to remove defective parts, such as missing or loose components, metal shavings, and damage from vibration or knocks,

Human Checks Not Good Enough
Previously, sight checks were conducted by human operators, which limited the number of defective parts to around 1 in 1000. This was unsatisfactory to Meister, so studies were performed to reduce this rate relative to 100 ppm. Meister also set to work on reducing the impact of manpower costs on the overall cost price of the parts. Consideration of automated checks using vision tools was a natural progression for the company's technicians, who already had experience with industrial vision systems for a dimension-checking application. A seminar organized by the Alpsitec company provided the technicians with additional information on the performance and capacities of the In-Sight vision systems from Cognex.

Production Line Demonstration
Alpsitec, an approved partner system integrator of Cognex, was called upon to carry out a demonstration on the production line to verify that the Cognex cameras were capable of "seeing" the faults to be detected. Following this first feasibility test, a prototype was created and assessed for a month. The ease of use of the In-Sight vision systems was a decisive factor in Meister's order and installation of two test systems at the end of the production line — used to perform a final inspection of each part just prior to packaging.

The parts are put into their packaging, the mesh, by a robot. Once packaging is complete, the robot picks up the packaged part and places it on the test surface. Then, the robot takes hold of the Cognex In-Sight 1000 vision system linked to a lighting system and passes it along the mesh and over the parts. It's important to remember that each part must be inspected for all primary types of defect: the presence of metal shavings, missing components, loose components, and damage from knocks or vibration. The system sends information from the inspection to the robot's control center. The robot then takes the defective parts and deposits them into a chute, based on the nature of the fault found, where they are then transported to a hopper.

One of the test benches is outfitted with two In-Sight 1000 systems and operates at a rate of 6000 parts per hour. The other system comprises a single sensor and functions at a rate of 4000 parts per hour. During the first few months of the operation, both systems worked as dual sorters.

The bulk of the work of updating the application consisted of identifying the various faults recognizable by the checking systems and "teaching" these faults to the vision sensors. This procedure is essential for optimizing the efficiency of the inspection system. The rate of faulty parts delivered to customers has rapidly dropped to 40 per million packaged. The powerful processor algorithms of the In-Sight system and more detailed analysis of the faults to be removed should allow this rate to be reduced even further, to below 20ppm.

Jean-Marc Sermet, Technical Director of Meister France, has supervised this project from start to finish. He is very pleased with Cognex's products and Alpsitec's service. The combination has provided him with the necessary skills and experience in installing vision solutions at Meister. "Above all, we are engineers specializing in precision metal cutting", Sermet stated. "Alpsitec's contribution has allowed us to make rapid progress on this project and to benefit from efficient and reassuring support."

Alpsitec has also trained a technician who has rapidly taken charge of setting the vision systems' parameters. Meister is now able to internally input data for new defects to be identified and is able to modify these parameters in relation to the 15 different types of parts to be inspected. "We were concerned that these test systems would slow down production rates. We have noted with satisfaction that the implementation of these industrial vision solutions do not have a negative effect on production", Sermet added. "The solution used appears to be particularly stable, and the operators do not have any need to intervene."

The greatest reward has been a considerable return on investment in less than six months. The significant improvement in quality has greatly strengthened customer relations, and Meister is currently researching additional applications for industrial vision on its production lines.

Contact: Cognex Corp., One Vision Dr., Natick, MA 01760-2059 877-264-6391 or 508-650-3000 fax: 508-650-3333 Web:

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