FIPA Magazine: About geckos, squids and robots

However, the history of gripper construction did not just originate in the exploration of nature. It goes back to the first hand prostheses in the Middle Ages, whose influence extends to today's industrial robots in the plastics industry. The history of gripper technology takes its origins in 1504, when the Franconian imperial knight Gottfried "Götz" von Berlichingen lost his right hand in a battle surrounding the Landshut Succession War. While in sickbed, he remembered a horseman named "Kochle" who supposedly possessed an iron hand. Götz had two such iron hands made. The first, more unknown model appeared between 1505 and 1510, was 13 cm long and weighed just under 600 grams. With the help of a pawl mechanism inside the iron hand, the fingers could be locked. Under spring pressure, they jumped back to the open initial position. In this way, its wearer moved fingers and thumb.

The second, more popular model appeared almost 20 years later around the year 1530. The prosthetic hand was 37 cm long and weighed 1.5 kg. It used the same mechanics as the first model, but the second "Götzehand" was much more complex. In the latest version, not only the fingers and thumb could be moved, but also their individual limbs. Three joints were used for the fingers, and two for the thumb. It was also possible to swivel the device by 15 degrees. Hand prostheses based on this design principle were widespread in the 16th century.

"Götz", whose nickname "with the iron hand" was first mentioned in 1518, rather involuntarily opened the chapter of gripping technology due to his war injury. Complex, versatile grasping as well as hand-eye coordination are just a few examples which also play a role today in the development of artificial gripping tools. In the meantime, the term prosthetics has become established for the development of hand prostheses, a science that deals with the development of artificial body parts.

In the second half of the 20th century, however, gripping technology once again received a great deal of attention due to the introduction of industrial robots. As development progressed, more and more possibilities and ideas emerged to expand the application field of gripper technology. This was because there were also limits to the human hand as a source of inspiration. Temperature susceptibility, limited load-bearing capacity and positioning accuracy as well as problems in moving extreme gripping objects such as bulky loads or tiny miniature components required new solutions.

These findings have lately flowed over into a third field, which is crucially involved in modern gripper technologies: robotics. Robotics is concerned with the development of robots. Today, industrial robots are used everywhere automation processes offer great potential. Grippers are working tools located at the very end of a handling machine and so form the interface between the industrial robot and the workpiece. This places them in the group of end effectors.

An end effector is a device that is fitted to the outermost end of a kinematic chain and that achieves an effect. The task of the industrial robot is to move the end effector to the target position according to the programming instructions in order to pick up or set down items. In production processes, robots fitted with end effectors such as clamping grippers, vacuum suction cups, magnets, finger grippers or needle grippers replace the human hand. Even when the combination of robot and gripper technology often works automatically, human hands are not completely superfluous. For example, a worker can work together in collaboration with the robot gripper system via a control model.

As opposed to biological systems, which have been subject to long-term evolutionary pressure, technical gripper systems are also orientated towards markets and trends. Gripper systems must provide the right answers to urgent problems, such as in the plastics industry. Companies in this industry are subject to great cost pressures. Die-cast technology has proven to be a tried-and-tested and cost-effective method of manufacturing plastic parts. To cut costs and remain competitive, it is often necessary to automate the entire periphery around the die-cast machines. Automation ranges from feeding in the granular material through to removing the parts from the machines and transporting them to the next processing station. 

Some questions that arise from the process of automation demand all the creativity of the design engineers: How should hot plastic parts be correctly handled? What needs to be considered when it comes to coatable surfaces? And what is the best method for metalized surfaces that must not be touched? A combination of knowledge from prosthetics, bionics, and robotics means that gripper systems today can react flexibly to the varied requirements. Thus hot plastic parts are lifted using silicone suction cups, which can briefly withstand temperatures of up to 200 degrees. HNBR and Thermalon suction cups are used for coatable surfaces up to 160 degrees. This type of design is low-marking, free of silicone and LABS and so can guarantee that the surface of the plastic parts is suitable for coating. In the case of reflective items that must not be gripped, FIPA designer Henning Schanz reveals a little trick: metalized surfaces that will not be faces can generally be gripped. Which can all be traced back to the loss of a hand.