Robots, handling systems and windscreens are superficially the same as they always were, but automotive glass installation today is a very different to even a decade ago.
With auto manufacturers controlling manufacturing processes more closely in order to eliminate gaps as much as possible, glass manufacturers too have had to develop new production processes in order to achieve dramatic improvements in overall tolerances. Powering the trend is a move to ‘exposed edge’ installation, where the glass is installed in the vehicle with sealant, but without a rubber moulding or PVC/ HDPE plastic trim to bridge the gap between the glass and vehicle’s steel frame.
The moulding plays a useful role in providing an additional barrier to dust and moisture, and permits looser manufacturing tolerances, but it also adds weight and cost. Simply achieve tighter tolerances, goes the logic, and the cost and weight of the moulding and trim can be eliminated.
“Exposed edge glass is more prevalent in Europe than it is here in North America, but it’s coming,” says Dave Kaufman, vice-president of OEM sales at Guardian Glass. “It’s mostly been driven by styling and aesthetics, but there turns out to be a wind noise reduction as well.”
Nor is it solely new manufacturing processes that the automotive glass industry has had to develop. The number of glass-related options offered on vehicles has increased significantly in recent years, says Kaufman, posing logistics and sequencing challenges as well.
“Not every vehicle gets the same quarter light, front windscreen or rear windscreen – and that’s before taking into account different sensors and coatings,” he notes. “What used to be one or two part numbers per vehicle is now eight to 10. And lineside storage isn’t an option; there’s just not enough real estate. For automotive glass manufacturers, line sequencing has become a much bigger issue.”
With those additional options have come additional challenges from an installation point of view – challenges that lie on the vehicle assembly plant floor, and not back in the supply chain.
Take the vacuum-driven suction ‘gripper’ pads, which underpin what are otherwise fairly conventional material handling systems. These suction pads comprise the main point of contact for the glass and take the brunt of the strain as the glass is picked up and positioned into place. Several distinct trends have impacted gripper pad technology in recent years, explains Matthias Müller, industry segment manager for glass and solar applications at German specialist automation, handling and clamping technology firm J. Schmalz.
For a start, he notes, the materials from which the gripper pads are manufactured have had to improve in order to provide longer lifetimes and reduced maintenance. But simply using materials that are more durable, without consideration for usage to which the pads are put, can quickly become counter-productive.
“Gripper pads are the part that comes in contact with the glass and have to be non marking, and also provide high holding forces in combination with a precise handling,” says Müller. “What is crucial is that they don’t damage the glass coating.”
Schmalz’ SAB suction pad series is made from a material called HT1, which doesn’t leave marks on the glass surface. In addition, the pads have a high-performance profile on the suction surface, in order to provide high lateral holding forces with high precision during the handling – a particular requirement during glue application.
In addition to these elastomeric grippers, says Müller, Schmalz also offers a range of ‘area vacuum grippers’. With these, the gripper surface that is in contact with the glass is made of a very soft foam material.
These, explains Müller, are particularly useful for handling coated glass, and with an integrated vacuum generator, comprise a time-efficient and flexible plug-and-play solution.
Indeed, Müller points out, in glass handling, vacuum generators and their performance are fundamental to the functioning of an efficient automated handling system. “The main requirements are short evacuation times and short release times,” notes Müller. “Handling an air-tight workpiece like glass means that the main focus of vacuum generation is on short evacuation times – the time until the handling system can start the movement – in order to minimise the gripping time of the glass. And, of course, the reverse is true for the release of the workpiece.”
In achieving this, the use of what are called ‘compact ejectors’ represents the current industry best practice. Based on venturi technology, with integrated valves for suction and blow off, as well as monitoring devices to monitor the status of the system, small and lightweight ejectors are placed directly on the gripping system, as close as possible to the suction pads. Short hose connections and the use of valves directly integrated to the ejectors then enable the short gripping and release times that are required.
“In conjunction with a monitoring unit, the ejectors directly communicate with the controlling PLC to provide a ‘part presence signal’ as soon as a vacuum level for safe handling is reached, and the movement of the handling can start,” says Müller. “In addition, we recommend the use of ejectors with a so-called air-saving system, which automatically switches vacuum generation off as soon as the vacuum has reached a pre-set level, which can enable a reduction in compressed air use by up to 90%.” Naturally, he adds, the air-saving function comes with a safety feature: should the vacuum drop to a certain pre-set level, the ejectors will then restart vacuum generation automatically.
And what of the future? According to Müller, this holds an even greater focus on energy efficiency and the incorporation of greater intelligence into the installation process. Integrated input-output technology, for instance, allows the entire vacuum handling process to be mapped electronically, and thus controlled and monitored from a higher level control station such as a plant-floor SCADA unit: handling cycles, valve activities, evacuation times and control cycles.
“This allows process errors and subtle changes to be recognised and localised early on,” notes Müller. “Service measures can be planned accordingly, and costly machine downtime reduced.”
Energy efficiency, too, has further to go, he reckons. One option is to use a pressure sensor, integrated into the ejector, which allows the user to evaluate energy consumption during processes, and gauge trends over a defined period – for example, monitoring the energy consumption per component, per handling cycle, or per shift. “Energy monitoring provides the user with detailed, qualitative data in regards to energy consumption and changes within the system,” says Müller. “If the energy consumption level rises disproportionately, the user can react immediately.”
In summary, the picture is clear. While the world of automotive glass installation is superficially little different from a decade or so back, between the sheets there’s a lot going on. From the glass itself, to the logistics, manufacturing and materials handling processes that are involved in installing it, innovation is rife.