An innovative method of controlling and optimizing car painting processes

Lead Research Organisation: University of Cambridge
Department Name: Chemical Engineering and Biotechnology

Abstract

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.

Planned Impact

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).
 
Description In this project we have developed a new method to measure the thickness of car paint layer structures on different substrates (metal and carbon fibre) by means of a non-contact sensor. The layer structures can contain high amounts of metal or other pigments and their thickness is below the previously resolvable threshold. The technology we developed is based on a novel sensing modality termed terahertz pulsed imaging and our industrial project partners are currently looking into commercialising this technology for car paint inspection applications.
Exploitation Route This is part of a TSB funded project and the industrial lead partner has developed a technology demonstrator as part of this project. This instrument has been used to test real car structures at Ford in Detroit as well as our industrial partner Aston Martin Lagonda.

In addition the data extraction algorithm that was developed in this project can be directly employed for all other coating thickness measurement applications that utilise terahertz pulsed imaging. We have demonstrated this in the application of polymer coatings for pharmaceutical tablets.

TeraView, our industrial partner, is currently commercialising the technology developed in this project and proof-of-principle measurements as well as contract work has already happened for other potential customers.
Sectors Aerospace, Defence and Marine,Agriculture, Food and Drink,Manufacturing, including Industrial Biotechology,Pharmaceuticals and Medical Biotechnology
URL http://thz.ceb.cam.ac.uk/news/new-paper-terahertz-sensor-for-measuring-the-film-thickness-of-automotive-paint
 
Description The findings from this project have been used at two car manufacturers to test whether or not the newly developed terahertz sensor can determine the coating structure and individual layer thicknesses in commercial manufacturing environments. We have successfully demonstrated that our new terahertz sensor can indeed resolve the typical structure consisting of four layers and quantify their individual thickness. The major advantage of our technology is that it is non-contact and can potentially be fully automated. compared to competing technology it has the additional advantage in that the measurement spot is much smaller (<1 mm) and hence can be used in locations on the car that are critical for the coating quality, but that cannot be tested reliably with current sensors.
First Year Of Impact 2014
Sector Manufacturing, including Industrial Biotechology,Pharmaceuticals and Medical Biotechnology
Impact Types Economic
 
Description Intelligent Manufacturing of Pharmaceutical Film Coating Using Terahertz Pulsed Imaging, Optical Coherence Tomography and Numerical Modelling
Amount £382,914 (GBP)
Funding ID EP/L019922/1 
Organisation University of Cambridge 
Department Engineering and Physical Sciences Research Council EPSRC
Sector Public
Country United Kingdom of Great Britain & Northern Ireland (UK)
Start 06/2014 
End 06/2016
 
Description Signal processing of terahertz waveforms (YCS collaboration) 
Organisation University of Liverpool
Country United Kingdom of Great Britain & Northern Ireland (UK) 
Sector Academic/University 
PI Contribution We have exchanged ideas how to model the propagation of a terahertz pulse in a layered structure
Collaborator Contribution Dr Shen suggested modifications of our existing model
Impact Joint paper (do:10.1109/TTHZ.2014.2325393)
Start Year 2013
 
Description Understanding coating of pharmaceutical tablets (Purdue collaboration) 
Organisation Dow Chemical Company (DOW)
Country United States of America 
Sector Private 
PI Contribution We have measured the coating thickness distribution of pharmaceutical tablets using terahertz pulsed imaging as well as helped with the understanding of the data
Collaborator Contribution The partners have provided materials (coated tablets, raw materials), developed a discrete element model of the coating process and have collaborated on writing up the results into a scientific paper
Impact Paper in Chemical Engineering Science: Comparisons of intra-tablet coating variability using DEM simulations, asymptotic limit models, and experiments (doi:10.1016/j.ces.2015.03.013)
Start Year 2013
 
Description Understanding coating of pharmaceutical tablets (Purdue collaboration) 
Organisation Pfizer Global R & D
Country United States of America 
Sector Private 
PI Contribution We have measured the coating thickness distribution of pharmaceutical tablets using terahertz pulsed imaging as well as helped with the understanding of the data
Collaborator Contribution The partners have provided materials (coated tablets, raw materials), developed a discrete element model of the coating process and have collaborated on writing up the results into a scientific paper
Impact Paper in Chemical Engineering Science: Comparisons of intra-tablet coating variability using DEM simulations, asymptotic limit models, and experiments (doi:10.1016/j.ces.2015.03.013)
Start Year 2013
 
Description Understanding coating of pharmaceutical tablets (Purdue collaboration) 
Organisation Purdue University
Country United States of America 
Sector Academic/University 
PI Contribution We have measured the coating thickness distribution of pharmaceutical tablets using terahertz pulsed imaging as well as helped with the understanding of the data
Collaborator Contribution The partners have provided materials (coated tablets, raw materials), developed a discrete element model of the coating process and have collaborated on writing up the results into a scientific paper
Impact Paper in Chemical Engineering Science: Comparisons of intra-tablet coating variability using DEM simulations, asymptotic limit models, and experiments (doi:10.1016/j.ces.2015.03.013)
Start Year 2013