High torque densities and high reduction ratios
Envalior, a leading supplier of high-performance thermoplastics, used its extensive technical expertise in materials, plastic gear design and CAE simulations to refine the design of the gearbox components. The focus was on manufacturability and reliable mechanical performance. Certain compounds from the Stanyl product range were selected on the basis of material properties, structural and manufacturing simulations. The PA46 is a unique high-performance polyamide known for its excellent stiffness, strength and fatigue resistance even at high temperatures. In addition, it offers excellent wear, abrasion and corrosion resistance as well as favorable friction properties that are ideal for gearbox applications.
Stanyl PA46 results in gear designs with significantly better torque-to-weight ratios than when using metals. At the same time, it enables very high reduction ratios. Both these features support the development of lightweight, reliable and durable gearbox systems, especially for robotics. "Previous market solutions made of plastic often did not meet the stiffness and precision requirements needed for high-torque robotic gearboxes. The new combination of Stanyl PA46 and SENTImotion's tooth geometry offers a major advance in this area," said Ron Krotwaar, expert in lightweight technologies at Envalior.
In addition to their lower density, plastics have a general advantage over metals because they enable the cost-reducing integration of functions such as mounts, guides and fastenings into the respective component. These functions are taken into account in the design from the outset and therefore do not have to be implemented in separate process steps, unlike metal designs. This reduces the total number of components required for the gearbox. The injection molding process also produces ready-to-assemble components. Post-processing steps such as milling, polishing or hardening are therefore no longer required. This is a major economic advantage, especially when it comes to manufacturing components in large quantities.
Lightweight, affordable robots start with the right gearbox design
Gearboxes account for around half of the total costs of metal robots simply due to their large number and contribute significantly to their high weight. For example, a standard robot arm with seven degrees of freedom of movement usually contains seven gears, so that the total number of gears in a humanoid robot adds up to more than 30. Therefore, designing the gears in lightweight plastic results in robots that are more than 20% lighter than their metal counterparts.
The significantly lower weight of a robot arm with plastic gears also has advantages for its dynamic behavior. It can be actuated with less force, which reduces the robot's energy consumption. The arm also reacts faster. In addition, the lower inertia of the arm increases the so-called safe speed, which benefits the robot's productivity. This allows it to complete its tasks faster, more efficiently and therefore more economically. The requirements for safe speed are defined in the ISO/TS 15066 standard. Among other things, it specifies how fast robots may interact with humans in order to avoid injuries. The high safe speed of the plastic gears significantly exceeds the requirements of the standard and therefore has the potential to be the impetus for an update of the standard.
For more information, visit Envalior at automatica (Hall B4, Stand 328) or at https://www.envalior.com/en-us/products.html.
