Steed Webzell talks to technology vendors about which OEM criteria are driving their innovations in robot design and development
Unimation installed the world’s first industrial robot in 1961 on a production line at the GM Ternstedt plant in Trenton, New Jersey. Obeying step-by-step commands stored on a magnetic drum, the robot’s arm sequenced and stacked die-cast metal components. Naturally, robot design and development has come a long way since those pioneering days and modern suppliers must now consider many factors when driving improvements.
According to Sean J Murphy, regional sales manager at Fanuc Robotics UK, reliability is the main force in robot design for automotive applications. “The robots used need to be reliable because automotive manufacturing processes are interlinked,” he says. “A stoppage in one area can bring an entire auto plant to a standstill and possibly cause a delay in the supply of vehicles to consumers.”
“Price is also a big consideration,” adds Murphy, “but this has to be weighed up against reliability and ease of maintenance. Safety should be another primary design focus – an automotive plant can be viewed as one large autonomous machine, but unfortunately this machine has to interact with humans at some stages of the process, so operator safety is paramount.”
Another major design consideration for Fanuc is payload, which plays an important part not only in robot selection but in the execution of actual robot movement. Payload data is used to determine how much energy is required to undertake every motion. Understandably, it takes more energy to move a robot carrying a completed car body weighing 500kg than to move the robot alone. In fact, the ability of Fanuc robots to carry 5% heavier loads is one of the reasons they were selected by the Luton, UK commercial vehicle plant of Vauxhall to help build the 2014 Vivaro. Last but not least, Murphy gives a nod to standardisation, as this allows for easier operation and maintenance. With Fanuc robots, the look and feel of the operating system and interface is the same – a concept that allows engineers and operators from different areas of the plant to understand and operate robots in different applications. The most recent fruit of Fanuc’s design efforts for automotive applications is the M-2000iA robot, which has been conceived to pick up a car body and transfer it to a high level, thus replacing a typical dedicated drop-lifter section. While this process is not new (many examples exist of robot pairs undertaking this task) doing it with a single robot means bodies can now be picked at low level and placed into other positions, for example into a rework station, or into a low volume process station away from the main line production.
Over at the Italian headquarters of Comau, the thinking is similar when it comes to robot design. “Quality is the default expectation of the automotive industry,” states the company’s engineering director, Enrico Mauletti. “It is non-negotiable and without it, you aren’t even considered. As you might expect, price is also an important factor, but in addition to the initial purchase price, clients are increasingly evaluating both the life cycle costs of the solution as well as process integration costs, measured in terms of ease of integration with existing processes.”
Mauletti also agrees that standardisation is a key trend, with most customers requiring ‘naked’ robots with only a few options, perhaps relating to safety or networking. “This is especially true in emerging countries and for plants that are relatively new to robots,” he says. “In Europe and the Americas, however, even if the final customer requires a naked robot, there are very strict specifications regarding particular aspects of the Human Machine Interface [HMI] and software functions. This means that in practice, the fulfilment of such requirements essentially makes these robots bespoke.”
Comau has recently launched a range of updated, dedicated robots for body shop applications that are based on the company’s patented ‘hollow wrist’ technology. Smart NJ4 family robots, with payloads from 90 to 270kg, feature a light, fast and stiff structure, and can be mounted on the floor or ceiling as needed. They also offer a new kinematic framework to reduce robot weight and overall dimensions – as well as cycle time – and can be located in high density spot welding lines featuring up to 18 robots per station. On the subject of impressive design, Kuka Robotics has plenty of reasons to sing having last year collected a coveted ‘best of the best’ design prize from the Red Dot Institute for its KR 270 R2700 ‘ultra’ robot from the recently introduced Quantec range. A panel of 30 experts examined, tested and evaluated the robot for its ‘green’ credentials, levels of innovation, functionality and quality. Only a handful of the 4,000-plus entries were presented with the best-of-the-best award, which is given to products that meet the very highest design standards.
Arguably the biggest trend in robot design at present is vision technology, and among the latest developments in this is MotoSense from Yaskawa, which offers joint detection and seam tracking with adaptive fill for critical applications such as TIG welding. The MotoSense adaptive vision system allows the robot to detect the location of the joint as well as to track the seam in corner, butt, overlap and fillet joints. For Yaskawa, energy is another hot potato in the robot design world. A robot’s energy requirements are determined not only by the design of the manipulator, but also the application, controller and system layout – the more varied the individual parameters, the greater the scope for potential savings. Even in isolation, intelligent shut-down concepts during breaks in operation, for example at weekends, can result in energy savings of up to 15%.
The company has observed that on a typical body production line, 40% of all robots could be selected at least one size smaller resulting in an energy saving of 8%. Selecting a smaller robot not only results in energy savings, but also increases cycle times. For example, by replacing a 250kg robot with an 80kg robot that has been designed for the specific application, up to 25% energy savings and a 20% reduction in cycle time can be achieved.
At last year’s Automatica exhibition in Munich, Yaskawa exhibited a robotic cell that demonstrated how utilising excess brake energy can pay real dividends. By intelligent switching of the drives to generator mode, the brake energy of a robot can be recovered and stored or fed back into the mains network. For those seeking a little energy boost in their automation operations, what could be better?
The recently introduced two-finger adaptive robot gripper from Robotiq is both compact and flexible with 85mm of stroke. It has been designed to give low volume auto manufacturers the flexibility needed to automate processes that feature a high mix of parts. Fully programmable, the gripper handles components through three distinct gripping modes: parallel grip; encompassing grip; and inside pick. Applications include flexible fixturing for welding, machine loading and unloading, bin picking and handling fragile parts.
Compared to custom tooling, the programmable adaptive gripper reduces set-up costs and cycle time due to its short stroke and the elimination of tool change delays. It features force and speed controls to handle parts with different rigidities, from brittle to stiff, while accurate finger control enables fast cycle times through partial open/closing.