About geckos, squids and robots.

How geckos revolutionized gripper technology in the plastics industry

What do geckos have to do with gripper technologies? A whole lot. As a source of inspiration for design engineers, the scaled lizards have had a great influence on the development of gripper systems. Nevertheless, the history of gripper assembly did not originate in research into nature. It reaches back to the first hand prostheses in the Middle Ages, whose influence still extends to today’s industrial robots in the plastics industry.

The history of gripper technology has its origins in the year 1504. At the time, the Franconian imperial knight Gottfried “Götz” von Berlichingen lost his right hand during the War of the Succession of Landshut. On his sick bed, he remembered a knight named “Kochle” who reportedly had an iron hand. Götz had two such iron hands made. The first, lesser-known model appeared between 1505 and 1510, was 13 cm long and weighed almost 600 g. The fingers were able to be clamped by means of a ratchet mechanism inside the iron hand. A spring action allowed them to spring back into the initial position. This allowed the wearer to move the fingers and thumb.

The second, more popular model appeared almost 20 years later in around 1530. The hand prosthesis was 37 cm long and weighed 1.5 kg. The same mechanism as the first one was used here, except that the second “Götze hand” was far more complex. The latter version allowed not just the fingers and thumbs to be moved but also all the individual joints. Three joints were used for the fingers, while two were used for the thumbs. It was also possible to pivot 15 degrees. Hand prostheses based on this design principle were widely used in the 16th century. 

Thanks to his battle injury, “Götz”, also known as “Götz of the Iron Hand” and first mentioned in 1518, quite unwillingly heralded in the first chapter in the history of gripper systems. Complex, versatile gripping as well as hand-eye coordination are just a few examples of what still plays a role today in the development of artificial gripping tools. The term prosthetics has now become established for the development of hand prostheses, a science that is concerned with the development of artificial body parts.

The influence of prostheses and bionics on gripper technologies

It wasn’t until the second half of the 20th century and the introduction of industrial robots, however, that gripper technology was first paid a lot of attention. The advancements in development yielded ever more possibilities and ideas for expanding the area where gripper technology could be applied. The human hand as a source of inspiration, after all, also had its limits. Susceptibility to temperatures, restricted loads and positioning accuracy as well as problems when moving extremely demanding gripping objects, such as bulky loads or tiny miniature components, required new solutions.

The influence of prostheses and bionics on gripper technologies

This was the reason why the research field of bionics increasingly became the focus of attention alongside prosthetics. Bionics is concerned with the issue of how biological systems can be transferred to technical applications. In particular, biological organisms and the structure of their natural gripping organs have provided valuable information for the technical implementation of gripper mechanisms. Two prominent examples from nature that have revolutionized gripper technology are the gecko and the squid. The foot of the gecko and the gripping arm of the squid have served as a source of inspiration. The gecko has feet with adhesive setae, with millions of tiny hairs attached to them. 

Using electrostatic interaction and Van-der-Waals forces, it can adhere to various different surfaces and release the adhesion again in just a few milliseconds. Moreover, the surface of the foot of the gecko possesses self-cleaning properties, meaning it does not lose its power of adhesion over time. The squid, on the other hand, possesses flexible gripping arms of varied lengths, which can move in any direction. The arms feature vacuum suction cups that adapt ideally to various surfaces and allow the squid to grip securely.

Geckos are small to medium-sized lizards that occur in a wide variety of species throughout the world. Some species have lamellas on their feet, with which they can adhere to almost all surfaces through adhesion.

The role of robotics in gripper assembly

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.

Challenges for the plastics industry

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 prostheticsbionics, 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.