Power to the machines

While human flexibility offers special advantages in the assembly hall, modern paintshops rely heavily on automation to tackle hostile conditions and a strong need for consistency. AMS reviews the recent trendsRobotic technologies have for decades been centre stage in automotive manufacturing. The industry is top of the league for robot utilisation, and it is arguably in the paintshop where they have made their greatest impact. In the assembly hall, ‘multi-axis’ humans offer the kind of flexibility and adaptability which keep them cost-effective even compared with the latest generation of high-performing robots. In the paintshop, though, it is automation which holds sway; a hostile working environment combined with the need for absolute consistency in paint application pushes technology to the fore.

For several decades, robot manufacturers have been honing their products to make them ever more dexterous and simpler to configure and operate. Key to these developments have been the close working relationships established over the long term between vehicle manufacturers and a handful of leading robotic suppliers which, in turn, have been supported by independent application specialists and software developers.

Three trends have become apparent in recent years. Firstly, perhaps the most important development has been the integration of robotic and non-robotic processes. Secondly, sensor and machine-vision technologies have been developing at a significant pace, bringing with them new possibilities and opportunities. Thirdly, developments in control software have proven crucial in generating real gains in quality, process control and flexibility of application.

Making the most of automationRobotic technology is applied to a whole range of processes in the modern automotive paintshop, and this hardware has seen the emergence of numerous developments. Robotic arms formed from lightweight alloy castings, sophisticated seven-axis systems, along with features like open process arms compatible with multiple OEMs’ paint systems all have a part to play in enhanced efficiency. Robotic arms are merely the most obvious and visible components; spray applicators, colour-change manifolds, pumps, flexible cable pathways and pipework, valves, pressure controls and regulators are all part of the picture.

‘Multi-axis’ humans are cost-effective in assembly; in the paintshop, the combination of a hostile working environment plus the need for absolute consistency pushes automation to the fore

Refinements in painting equipment have, for example, reduced the cleaning requirements during colour changes, with the colour changer incorporated into the atomiser and each colour having a separate dosing pump connected by switchable pneumatic couplings. Incremental improvements in each type of painting equipment in recent years have generated gains in efficiency, but it is the successful combination of these enhancements within the overall paintshop system which produces the best results.

A further point to consider, as argued by leading German paintshop supplier Dürr, is that a process which is technically feasible may not always represent the optimal solution for a customer’s needs, nor produce the greatest benefits; true efficiency is achieved by using only the level of technology that is absolutely necessary. Reducing complexity can bring with it numerous advantages, not least lower maintenance costs and simplification of workforce training.

One challenge for automotive manufacturers relates to the utilisation of robotic equipment in plants with less-than-ideal layouts. Automated systems are well-suited to high-density paint-booth layouts; whether shelf-, wall-, or rail-mounted, paint robots can offer compact workcell solutions. Increasing attention is now paid to the way robots can be designed to work in close proximity to each other and ancillary equipment. With creative robot placement, companies can not only save floor space, but also achieve faster cycle times and better accessibility.

The ingenuity of suppliers who configure workable solutions in such circumstances is highly valued by their clients. Future developments will therefore be affected not just by technological development within robotics but perhaps as much, or more, by the ability of those tasked with system installation to deliver real-world solutions for their customers.

With OEMs placing more stringent product and process quality controls on their suppliers, which in turn are passed down through subcontractors, automated painting is increasingly to be found even at small suppliers in less developed markets. Painting is tedious, repetitive work, and human operators are at risk of exposure to harmful toxins including volatile organic compounds (VOCs), isocyanates and carcinogens. With a robotised system, hazards are minimised and the working environment greatly improved. Given the enhancement of finish quality, vehicle end users have undoubtedly benefitted from increasing automation in automotive manufacturing throughout the process chain.

Implementing intelligent controlThese days, virtual techniques and material-flow simulation methods are frequently used to plan the optimum overall concept and layout of new paintshops, as well as to remodel existing facilities. Conveyor and material-handling systems are crucial to efficient paintshop operation, and these too have evolved considerably over recent years. The latest compact designs offer tight control over material flow using overhead conveyors, pendulum systems and sophisticated monorail installations. Elsewhere, sensor systems will be further developed and increasingly take a key role in quality measurement and assurance.

Indeed, the use of intelligent, IT-based control systems, linking paintshop activities to other factory processes, is now recognised as an important enabler of enhanced efficiency. The main robotics suppliers regularly release new developments in this area, and with each function, planned and programmed production can be maximised. With scheduled maintenance, and sophisticated back-up systems available in the case of a machine malfunction, production flow can be maintained and downtime reduced.

Extensive research has gone into the development of sophisticated paint-process controllers, readily programmable and operable without the intervention of highly skilled personnel. Automatic process planning and motion planning for complex surface geometries, along with multi-robot scheduling and interactive adaptation and optimisation of paint paths, all play a role in ensuring cost savings and reduced cycle times.

Using technology to paint cleanlyEnvironmental concerns and energy usage are increasingly important drivers of technological development in automotive paintshops. The more sophisticated the robotic hardware and control systems which can be incorporated, the more overspray and wastage can be minimised, bringing benefits in terms of cost savings and a reduction in air and water pollutants. Recent years have seen significant advances in the treatment of waste heat and pollutants from automated paintshops.

In September 2016, Audi will launch what it calls “the most environmentally friendly paintshop on the American continent” at San José Chiapa, Mexico, while its German rival, BMW, is building a plant in the country at San Luis Potosí to open by 2019 which will include a zero-wastewater paintshop – the first such facility in its global production network. At the time of writing, Audi was also due to launch a new paintshop at Ingolstadt, Germany, with “ultramodern equipment” including a dry scrubbing process, 80% recirculation of cleaned waste air, plus robotic technology which improves paint application by more closely following the contours of the vehicle bodies.

In modern paintshops, electrostatic overspray removal systems deal with contaminated air, while regenerative thermal oxidation processes tackle waste-heat recovery, allowing significant savings in energy and associated costs. Adsorbsion processes have been developed as an alternative to concentrate air with low pollutant loads. The smaller the volume of air and the higher the concentration, the lower the investment and operating costs. This is why adsorption can be a first step in the treatment of large volumes of exhaust air with few contaminants. This makes subsequent processes, such as combustion or solvent recovery, much more cost-effective.

Those companies involved in the construction or upgrade of paintshops also find that the combination of wastewater recycling and material recovery can deliver a favourable return on investment.

Meeting future challengesFlexibility in automotive painting has become essential. Whether it is a single-robot painting cell or a multi-robot integrated finishing system, the same consideration must be given to its potential for adaptation in the light of changing market demands. Suppliers of robotic technologies always point out that automotive manufacturers are among their most demanding clients, with the need to respond to market fluctuations always high on the agenda. The ongoing challenge is to produce robotic systems which can combine high operational performance with the maximum possible programming flexibility. Dürr, for example, offers much of its paintshop process equipment in modular form to allow for easy reconfiguration and a rapid response to production changes and evolving plant layouts.

The EcoBell 2 atomiser from Durr. Increasingly, paintshop equipment will need to cope with alternative car-body materials

Another challenge for the future is the need to adapt to the introduction of new materials in body construction, plus the use of familiar materials in fresh applications. Lightweight composites, now widely used in high-end vehicles, will increasingly be found in mass-market products. They present their own challenges in paintshops and in preparation areas, all of which have to be integrated into a seamless production process. In response, suppliers such as Eisenmann are integrating both traditional sanding and alternative processes such as laser technology with the spray booths. Electrostatic overspray removal systems, dry scrubbers, horizontal or cross-flow Venturi scrubbers can be incorporated as required.

Alongside the technical development, manufacturers are being offered alternative business models in the supply of equipment and paintshop development. ‘Pay on production’ (POP) deals, where the full responsibility for plant operation is assumed by the line developers, or ‘build, operate, transfer’ (BOT) arrangements are being canvassed within the industry and it may be that these models will have an attraction for some categories of paintshop customer.

Shaving seconds off sanding

One technological innovation at this year’s PaintExpo was an automated sanding system from Germany-based Asis, consisting of a six-axis robot from Yaskawa of Japan, an active contact flange from FerRobotics of Austria and an abrasive changeover station developed by Asis itself, plus off-the-shelf pneumatic or electric sanders. Sanding is associated with manual labour, but the Asis system enables the automated sanding of metal, carbon and plastic surfaces, and is claimed to offer reproducible quality, process reliability and flexibility. Furthermore, the automated changeover of sanding media can be achieved in under 15 seconds, according to Asis.

Sebastian Gottwald, project manager at Asis, regards the Yaskawa MH50 II robot, the centrepiece of the system, as a “universal genius”, saying that: “With its reach of more than two metres it is capable of a broad range of work, while maintaining a high degree of precision in all areas with a remarkable repeat accuracy of -/+ 0.2mm. Extremely good path behaviour of the robot is also critical for sanding processes, and the MH50 II does not fail to impress on this point.” He adds that the robot is very easy to programme.

Meanwhile, the active contact flange regulates contact pressure in all positions by means of a sensor system; an interface pad between the flange and the abrasive also caters to irregularly shaped surfaces. “With this solution, we can regulate the contact pressure far more accurately compared to the handheld sander,” explains Gottwald. “We can also work on body panels with different contact pressures and thus, for example, increase the removal rate over a surface and sand at more difficult points with due care and correspondingly lower pressure.”

The automated sanding system from Asis can be used on metal, carbon and plastic surfaces, whether car bodies or components

The automated abrasive changeover process involves the robot moving to the station, clamping the grinding disc and exchanging old for new paper (the interface pad can be swapped similarly). Nonetheless, the dispenser holds enough abrasive material for operation over several hours before changeover is required.

The Asis automated system is already being employed in the automotive industry, for the sanding of vehicle bodies and components such as spoilers. “In a specific customer application, the sanding time for a certain component using our standard cell may be 12 minutes compared to 22 minutes for manual work,” says Gottwald. “The robots are not almost twice as fast in every application, but we always achieve time savings of 30%.”