The Hindu Business Line : Robot vs robot

Robotics has held the layman in awe ever since artificial intelligence became a buzzword. So, it is natural for us to assume that anything done without the intervention of humans tends to be accurate. While this is largely true, it cannot be taken for granted. That’s what a visit to Hyundai Motor’s car factory near Chennai tells you.

The company uses robotics a great deal in its manufacturing process. But due to the speed in mass production, complex processes and safety requirements, it wishes to take no chance even with the performance of highly reliable robots. Enter the Auto Checking System. At the body weld shop in the factory, where several small pieces of metal parts are assembled and welded to build the shell or body of the car, Hyundai has deployed a set of four additional robots to assist in the ACS. Together, they check the welds executed by other robots on the shop floor.

Robots are automated machines used to carry out various tasks, especially in mass production. They are computer-controlled equipment with an arm that can move in any direction. Robotic arm can be programmed to use different tools (for welding, drilling, painting, etc) and extend to perform tasks that are humanly impossible.

The robots deployed in Auto Checking System check for accuracy at designated locations that are identified based on the safety-critical aspects of the vehicle. Some of the checking points include front end module, rear combination lamps, rear bumpers, crash pad, windshield glass mounting aperture and hinge points of all the doors.

Why ACS

There are, for instance, 1,685 welding points in Hyundai’s i10 car and 1,590 of them are done by robots. The Plant II that builds i10 has 173 robots — 121 for spot welding, 41 deployed in hanger and seven for sealing operations, besides the four ACS robots. Welding is vital in the automobile since it fuses two or three metal parts together to achieve the desired three-dimensional profile of the vehicle. And a flaw in welding can be disastrous.

The factory is designed to produce 57 car shells per hour, eventually churning out 3,00,000 cars per year. Moreover, the company has been exporting about half of its production and since the liability on quality is high, it was unwilling to take a chance, even though robots carry out the welding. This is because there are 93 different child parts put together to make just the shell of a car. In a car, there are over 4,000 child parts. Child parts are constituent components of the shell, like each piece of a jigsaw puzzle.

Besides, to perform one welding cycle, each robot has to physically move 110 times in seven different axes (directions). For example, there are 26 spots to be welded within 65 seconds in the right-hand-side door opening of the car. And each welding operation has four steps — hold, clamp, weld and cool. This kind of intensity in action translates into wear and tear for the robotic arms. Left unchecked, this could threaten the accuracy of the whole welding operation.

Considering the complications involved and the risk in rejections, the company introduced ACS with four robots, which inspect the shell of the car for its accuracy, using a Web-based system, coupled with effective analysis. These robots check 81 points for an accuracy of 0.2 mm tolerance (or thickness of about four human hairs) using LASER (Light Amplification with Simulated Emission of Radiation).

How the checking is done

Pictorial representation of ACS.

ACS is positioned at the end of the weld line so that it can check every car body before it goes for further value addition, such as painting and assembly. ACS uses specially developed software programs to operate the four robots. As and when the car shell arrives at the ACS bay, the in-house developed software actuates the robot to position its arm closer to the car body but without actually touching it. The laser guns fitted at the robots’ arm shoot a laser beam and assess the quality by measuring the reflection of the beam with respect to the corresponding time taken during the process.

This is much like the way bats find their way about. They send out signals and if it comes back quickly, it means there is a hindrance and hence they have to change course. In the case of the ACS, if the laser beam does not come back within a specified time limit, it would mean that the welding has been improperly done.

A laser beam (in red) checking the quality of the welding.

The data retrieved in digital form is correlated with the digital template of ACS and allows the car shell to go through subsequent processes only if it conforms to the stipulated dimensional accuracies. If the tolerance is beyond 0.2 mm, the system will alert the quality inspector and the line supervisor immediately through a Web-enabled communication system. Besides, it will immediately stop the weld line from the work station where the defect has emerged.

For convenience, the system has a visual inspection module — Body Data Management system, which is nothing but a monitor showing the data captured from the car body in the form of a graph. The diagram has a couple of red lines on it. Based on data that the ACS gives out, a blue line is marked. If the blue line is mapped between the two red lines, then the welding operation has been executed well. Similar to the ECG, these graphs are put up right next to the ACS station so that any inspector passing by is reassured that all things are fine.

In the normal course the system also generates a feedback to the quality inspector enabling him to monitor the production process. It helps to produce a car body with consistent dimension, detect problems and take immediate corrective measures. Also it helps to check the critical dimension of a car body, which will help the car offer better driveability, safety and fuel economy.

ACS uses in-house developed software to check and manage body dimensional data during the production process. Access to this tailor-made system is given to only a few departments through closed network arrangement. Through this system the headquarters of Hyundai in Korea can see online the progress of the manufacturing process at the Sriperumbudur plant. Engineers involved in the production and quality inspectors get digital data retrieved by the ACS robot. This helps them take control measures in the manufacturing process and also to align the robots on account of wear and tear.

tmurrali@thehindu.co.in

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