QMT Features: July 2008
Handle on vision
An automatic  vision system  provides a robust method for 100% final inspection of automotive door handles . By Earl Yardley, Industrial Vision Systems

The build of an automotive handle comprises of many differing production processes including pressure die casting, injection moulding, painting and assembly of the final unit.

All of these processes require careful planning to achieve the quality levels expected of a Tier 1 automotive supplier. The final inspection of the assembled unit and kit of handles which make up a complete car is critical prior to the product leaving the factory.

Because of this, one large UK-based OEM manufacturer of automotive door handles approached Industrial Vision Systems (IVS) to automate the process for inspection of these parts. As a sister company to NeuroCheck from Stuttgart, Germany, IVS designs and manufactures machine vision systems for many industries including the electronics, pharmaceutical, medical devices, food and printing, as well as the automotive industry.

Inspection machine
The manufacturer produces an average of 100,000 keys or ID-devices, 60,000 door handles and 24,000 steering column locks each day. The required machine must perform a number of inspection tasks as part of the final automatic quality control of the product. An automotive handle is made up of a number of constituent parts including the main body of the handle, a buffer insert and a clip – all these parts are critical to the effective operation of the handle in the application. Add to this the number of colour variants of each handle available along with the variations in 2 door/4 door left hand/right hand which go up to make a complete car handle pack; and it can be seen that the final inspection is critical to guarantee the correct components reach the customer.

The vision system was required to check for a number of key criteria:
1. The correct combination of parts is present in terms of left hand/right hand handles, and locking/non locking parts as required.
2. Check of the individual components of the handle to confirm they are seated correctly in the handle and have not deviated out of position, including the handle buffer and clip.
3. Check of the correct type against the manifest sheet.
4. Check the positioning of the parts within the customers box before final delivery.
The automotive handles are sent to the customer in specific rigid boxes with an in-fill foam insert designed to take a combination of handle types. These boxes are returned to the supplier once the handles have been used on the car and the box re-used again.

System design
The machine design was based on a manually loaded station with an automatic conveyor feed to present the boxes to the vision system cameras, a conveyor area for re-work, and an out feed for good products. For the inspection process the box was required to stop in the centre of the machine where the barcode manifest situated on the side of the box was read via the vision system. This gave the settings of the current type to the machine PLC, which in turn switched the correct check routine within the vision system for inspection of the particular type.

In the design of its vision system, IVS chose a standard Bosch Rexroth conveyor system which was built into a custom designed framework. The design of the machine had to take in account the loading and unloading by operators along with all the required tooling and fixtures for holding the vision system components and associated LED line lighting.

The vision inspection area was purposely designed to stop the ingress of ambient light; therefore lighting levels could be controlled by automatic switching of the lighting arrays as required. Six cameras were mounted into the canopy over the conveyor - five medium resolution FWX06c Digital Firewire Cameras and one high resolution FWX20 Digital Firewire Camera. The medium resolution cameras were used for the general inspection processes including the overall correct presence of the handle and deviations of sub components within the handles – whilst the high resolution camera was used for label inspection and reading of the bar code relating to the manifest sheets.

Four high intensity 280mm white LED line lights were mounted obliquely to the box requiring inspection. The lighting units included a polarizing filter (as were the lenses) to reduce glare and reflections from the metallic painted parts. Following the inspection process the machine automatically marks a good part with an ink marking system on the label. This is then verified to check it has been marked correctly by the vision system before final release to travel down the pass conveyor area. The manifest is also logged to the factory information system so it has been recorded as passing final inspection.

The whole vision system is controlled by the standard NeuroCheck machine vision software package which communicates with the cameras, completes the entire industrial image processing to confirm the acceptance or rejection of the part – and finally communication with the internal machine PLC and the factory information system. Two industrial PC units are integrated into the machine, with one being the master which is used in day to day operation of the machine – the second industrial PC is present purely as an available backup in case of failure of the master PC. A Siemens S7-200 PLC is used to communicate with the vision system (via Profibus), conveyor control, sensors, and the ink marking system used to confirm a good box. A Siemens PLC HMI interface is also integrated into the front panel of the machine to offer overall control to the engineers for the ongoing maintenance of the machine.

To supply the system’s operator with information regarding each box inspected, IVS used the NeuroCheck software to develop a graphical user interface to display images and the results of each inspection. As each box is inspected, the operator is presented with an image of the box and the highlighted search regions. The results of each pass or fail on each box is displayed as well as a running total of the number of handles inspected and passed by the software.
Because such information is stored in a standard database format, it can be networked to existing database systems to provide management about the integrity of each system in the production process. This information can be transferred from the system’s PC using a standard Ethernet interface.
The machine offers a robust method for automatic final inspection of every handle leaving the factory thus guaranteeing the quality for the manufacturer. Every box is logged against the factory information system so an historical database of information relating to quality and ongoing statistical process control has been gained. Ultimately the Tier 1 manufacturer can offer a cast iron guarantee of the quality of products leaving the factory to their customer. l


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