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Colour Control and Measurement in Automotive Industry

28-04-2020

With the advent of technological advancements in industries, the automotive market has become increasingly competitive. There has been a rise in the demands of consumers for better, safer, and more reliable vehicles that would bring them a more enjoyable driving experience. Amidst the process of producing world-class vehicles, manufacturers duly understand the importance of vehicle design and lighting in the manufacturing. They are also fully aware of the fact that besides the functions, technology and safety features, factors such as brand, design and colour also impact the purchasing decision of customers. Hence, components from the interior or exterior of a car require to be homogeneous in their appearance. Any visual discrepancy of colour and texture in vehicles directly affects the brand image and reputation of a manufacturer.

When ordering parts, a supplier is provided a series of colour samples specified by the car manufacturer. Ensuring colour homogeneity of a vehicle gets challenging when the components are outsourced to the vendors by different suppliers. It gets especially difficult when metallic or pearly paints are used because of the fact that metallic chips in paint cause a variation in colour and are sensitive to different illumination sources. Furthermore, factors such as dry thickness of the paint, formulation of the paint and paint flow can affect the colour consistency. To achieve the shades specified by the customer and ensuring homogeneity of colours in different parts of a vehicle, colour measurement methods are employed in the automotive industry. Let’s look at some of the common applications that have been applying colour sensing techniques for achieving the required result.

Colour Measurement Applications in Automotive

LED’s are the main source of lighting used in the interior and exterior of a car. The headlight, tail light and indicator must be thoroughly tested to ensure that they comply with the industrial lighting standards and are easily noticeable by other drivers. Automotive OEMs (original equipment manufacturers) and vehicle manufacturers plan their lighting and design schemes according to those standards. However, due to mass production, small discrepancies are likely to occur in the material structure, composition, and thickness that results in spectral variations and colour differences. White point adjustment and colour measurement techniques are employed for quality control in automotive research and development. In this case, different spectrums of light appearing to be the same colour are differentiated using colour measuring sensors. These colour measurement techniques are frequently utilised in various production and inspection phases as well as in vehicle research and development process involving colour formulation and lighting system development.
A common issue faced with the LED vehicle lights is the fluctuation of LED batches. Therefore, to ensure the homogeneity of distribution of light, the colour and intensity of these batches are inspected before getting them assembled. Special LED test systems are designed to test inaccessible and widely spaced test specimens.

For components with similar shades, the process of qualifying car parts becomes very tedious. The parts are supplied through a channel of vendors and each of them has its own colour formation and suppliers. During the inspection process, the colour differences are not distinguished easily, but only become prominent on complete assembly. The colour mismatch results in rework, which incurs more cost and takes a lot of time. This is why vendors and manufacturers have shifted from visually examining parts to relying on colour recognition systems.

Parking sensors are painted and attached to the car separately. The major concern while assembling them to the car is the colour mismatch between the parking sensor and the bumper. Even the slightest of colour variation is unacceptable during the assembly. Other car attachments such as the cover of the headlight washer nozzles, mirror and body shell also require colour inspection to determine any colour difference with the parts to which they are going to be attached. It is also important that before installing the front aprons of a car, it is verified if the colour of the attachment matches the colour of the body of the car. Hence, before assembling components of a car that are painted separately, colour measurement techniques are employed for defining the maximum difference between the two colours of the channels.

During the assembly of car components, visual examination of the colour of seams of similar components is a challenging task, more so when the results are not very reliable. To prevent any critical error during the assembling process, special colour measurement systems are incorporated in the assembly line to automate this crucial and hectic process that used to be handled manually before. Nowadays, high-resolution measurement techniques are applied that are capable of distinguishing seams that look virtually the same to the human eye.

On a regular basis in an automotive industrial environment, colour recognition and comparison are done using colour sensors based on high-intensity white LED onto the measuring target. Fibre optics colour sensing technology has also been in demand for in-line colour measurement. Using these colour measurement systems, the L*a*b* colour values are determined that helps in calculating the colour difference between two shades.

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