An innovative method of controlling and optimizing car painting processes

Terahertz (THz) radiation forms part of the electromagnetic spectrum, between microwave and infrared radiation. It can penetrate a range of materials - including polymers, ceramics and semiconductors - and at the same time it can reveal excellent contrast of the internal microstructures of such materials. This property can be exploited for non-destructive testing by using pulses of terahertz radiation similar to the way radar imaging is performed. Using this measurement principle a number of applications, such as measuring the thickness of polymer coatings on pharmaceutical tablets, have
been developed. The technology has shown great promise for applications in high value manufacturing and this project aims to open up a new industrial application for terahertz sensing:

Painting is an integral part of the manufacturing process in the automotive industry. The paint coats that are applied to modern cars comprise a complex structure of layers, with the integrity of each layer being of critical importance to the overall performance of the coating. The current quality control strategy that is used to ensure the final integrity of the paint coat is slow, requires manual testing and can only cover a limited number of sampling points on a few select cars per test cycle. The main bottleneck behind this lack of real-time testing capability is that there is no non-contact measurement technology available that is fast and accurate enough for this task.

It is this bottleneck that the current proposal aims to remove by developing a terahertz sensor that is capable of performing real-time measurements of the paint quality and layer integrity in real-time using a six-axis robot that can be directly employed in the spray booth of existing manufacturing lines. Our research will make a vital contribution to ensuring the validity of these measurements, which is of paramount importance to deploying this technology in the automotive industry.

As part of this project we aim to develop the technology platform that can be used to implement direct quality control feedback loops.

Nondestructive testing using pulsed terahertz radiation is an important emerging technology with a wide range of potential applications both in academic research and industry. The potential of this technology for the pharmaceutical, catalysis and medical sectors has already been demonstrated, both for research and quality control applications. However, to date the technology has not sufficiently penetrated the markets in any of the above fields to sustain continued growth for the UK
terahertz industry.

A primary route for the impact of our work will be through the companies that we have partnered with. If this research programme proves successful and we are able to develop a working technology demonstrator at the end of the project it will likely spark strong interest from a wide range of automotive manufacturers and paint technology suppliers. The technology is very attractive as it will make significant cost savings in the paint process possible while ensuring or even improving the product quality through superior process control. The rapid take-up of the new technology by these companies will benefit the UK economically through the improved competitiveness of these industries besides strengthening TeraView and other SMEs that are involved in supplying the terahertz sensor technology.

In addition to economical benefits there is an environmental impact as well as the failure rate of the paint process should be drastically reduced; the overall amount of raw material can be reduced as a consequence of better process control; and due to the better overall coating quality the lifetime of the cars will be significantly increased due to a reduced corrosion rate. Together with an overall reduction in the total volume of hazardous materials this will help to improve the sustainability of the automotive sector. Typically each car consumes over 10 kg of paint (a typical plant will use more than 2,000 tons of paint annually); an estimated 2% reduction in paint consumption is realistic and in addition this will lead to an equivalent reduction in solvent and sludge.

Besides the automotive industry the concept is directly applicable to the aerospace industry. The project will provide the PDRA with a unique possibility to gain insight into the field of terahertz technology as well as driving innovation and developing end user applications of this technology in close consultation with experts from the relevant industries (automotive, robotics, paint).