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Innovative Automation, a certified systems integrator for Cognex, has implemented a 2D Data Matrix code to provide complete traceability in a handpass assembly system.

Providing complete traceability to ensure that each operation of a handpass assembly system has been successfully completed is a difficult challenge.

For example, if shift registering is used in the programmable logic controller (PLC) program, part counting will be thrown off if a part is introduced or removed from the machine.

Innovative Automation overcame this challenge by applying the 2D Data Matrix code to the part in the first station of an assembly system that it built for an automotive supplier customer.

The company has installed more than 100 camera/vision solutions for its own customer base, which primarily includes Fortune 500 companies within the automotive and consumer products industries.

Working with Cognex supplier Sure Controls and utilising onsite prototyping ability, Innovative is able to determine the viability of vision applications before a project begins.

Innovative Automation was contracted by a specialist in electromechanical actuators and emission control devices to design and build an assembly line to produce a new actuator.

The client required the stringent monitoring of the assembly process operations, as well as the final testing operations.

Traceability, which is often required in critical applications such as medical device and commercial airliner manufacturing, is becoming a common requirement in other industries.

According to Cognex, traceability improves quality by making it possible for the manufacturer to verify that every part shipped to the customer has passed quality tests and limits legal liability by making it possible to prove that a particular part was not defective.

At the same time as that traceability is becoming a more common requirement, it is also becoming more difficult to achieve.

Niche products, which are produced in smaller volumes, are not conducive to traditional approaches to providing traceability.

For example, radio-frequency-identification (RFID) tags are sometimes attached to pallets used on transfer machines that are typically used to produce parts at very high volumes.

However, this approach is becoming increasingly unavailable as manufacturers migrate to more flexible systems that often do not use pallets.

When RFID tags are used, as soon as the user pulls the part off the pallet, he or she loses the identity of the part and the associated data.

The code is read and the part is inspected at subsequent stations with vision systems and the results are automatically uploaded to a database.

By the time the part has been completely assembled, the database contains a complete record of the inspection results, meeting the customer’s traceability requirement.

‘Providing traceability offers many benefits, such as limiting the scope of a recall to only the parts that utilised the questionable materials,’ said Frank Gouweloos, sales manager for Innovation Automation.

Parts are passed by hand from station to station in the assembly system used in this application.

The assembly system also includes a four-station dial machine in which parts are indexed between stations.

Innovative Automation utilised a concept of marking a 2D Data Matrix code on the plastic housing of the part that is read at each assembly and test operation.

Each code consists of a series of dots and spaces configured in rows and columns in an arrangement that gives each pattern a unique identity.

In this application, prior to the start of assembly operations, a 2D Data Matrix code is etched into the housing using a Telesis laser unit.

Sure Controls provided the laser and vision components.

A Cognex In-Sight 5110 vision system is used at the first assembly station to verify that the 2D Data Matrix code quality is sufficient to be readable at all subsequent machine stations.

This pre-screening verification is necessary with laser etching when the surface condition, flatness and marking position of the part may not be repeatable.

Other considerations are that the lighting and distance that the camera can be mounted from the part varies from station to station as a result of variations in the part orientation and tooling interferences.

Innovative Automation selected the In-Sight 5110 vision system because it provides a vision tool library that makes it simple to program a range of industrial applications using a point-and-click approach.

The In-Sight vision system is also suitable for often-crowded assembly system stations because it fits into a 109.1 x 61.4 x 35.5mm package.

At each subsequent assembly station, the code is read by a Cognex Dataman 100 industrial identification (ID) reader, which reads 2D Data Matrix code at high rates of speed.

The ID reader sends a signal to the PLC database to indicate that the operation has been completed.

Tests are also performed at many stations using sensors or vision systems and the results are added to the PLC database.

If all previous operations have been successfully completed, the part status is considered valid for the station and the assembly or test operation is allowed to proceed.

This eliminates the possibility that a rejected part might find its way back onto the machine and get inadvertently shipped to a customer.

On the other hand, if a part is rejected and subsequently repaired, its status will be updated in the PLC database and it will be accepted at subsequent stations.

An operator can determine the status of a part and identify what needs to be repaired using a handheld device, such as the Cognex Dataman 7500 handheld reader, which is used by the company that purchased the machine.

At the first assembly station of the machine, where the vision system verifies the code, an operator presses a seal, a bearing and a stud into the lower housing.

A sensor measures the force used to press the parts into the housing and this information is saved in the PLC database.

If the operator tries to push an oversized bearing into the pocket on the housing, the sensor will record an excessive force value and the part is removed at this station or will be rejected at the next station.

The operator can pull the oversize bearing, put the housing back into the first station and then press a new bearing.

A second Cognex In-Sight 5110 vision system at the first station looks upward to verify the presence and orientation of a seal and clip in the upper press tooling.

Adam Ritchie, control specialist for Innovation Automation, developed the inspection application using Cognex In-Sight Explorer software tools.

He connected the vision system at the first station to a personal computer using an Ethernet connection and loaded the parts to the press tooling.

The In-Sight Explorer software provides a window that shows the image coming from the system.

Ritchie created a box on the image around the seal and he used In-Sight Explorer’s Patmax pattern-matching feature to train the vision system to look for an image matching the good part.

At the second station, an operator loads an output gear and a shaft onto the assembly.

At the third station, the operator attaches a small electric motor with a pinion gear that engages the gear loaded in the previous station.

At the fourth station, the assembly is loaded onto the first station of a four-station dial machine and the cover is married to the assembly produced in the previous stations.

The operator also attaches an intermediate gear that engages with the pinion and output gears at this station.

The dial machine then indexes the part to its second station.

Here, a 20lb/in2 pressure leak tester checks that the housing is airtight.

The results of this test are saved in the PLC database.

If the test results are unsatisfactory, the part will be rejected at the operator load/unload station.

Grease is automatically injected into the pinion gear at the third station of the dial machine.

At the fourth station, a second operator loads the cover with five clips and presses it into the lower housing.

The clips snap into place to hold the cover to the lower housing.

The part then indexes back to the first station of the dial machine, where a Cognex vision camera is used to verify clip presence.

Ritchie had created boxes around the five clips that should be installed in the housing and used the In-Sight Explorer edge tool to check for their presence.

The same operator that loaded the part onto the dial machine unloads it to the fifth station of the assembly system.

A function tester at this station powers up the part and runs it through a series of operations.

The test results are stored in the PLC database.

The operator then passes the part back to the first station, where the same laser that put on the original 2D Data Matrix code applies another code that includes the serial number and the date code for the accepted part.

The assembly system met the customer’s part traceability requirements, including tracking part status throughout the assembly process.

The additional in-process inspection operations also provide an extra level of quality assurance.

The customer originally bought a single machine with the vision system, but now uses a 2D Data Matrix code tracking system on all of its assembly lines.

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