When conventional handling modules reach their limits, additive manufactured solutions made of polyamide are able to step into the gap. The robust and abrasion-resistant flight weight increases process reliability and efficiency.

Since 2005, Schunk has been focusing on the near limitless possibilities of additive manufactured gripping system components. The competence leader for clamping technology and gripping systems has consequently analysed the various generative manufacturing methods on other fields of applications such as handling and assembly. In test series, Schunk looked at the behaviour of solid joints, the dependence of production orientation (load direction), and the reset process. Moreover, Schunk and the Fraunhofer IPA tested generatively manufactured robot grippers and optimised them. The result was impressive: Additive manufactured gripping components are light, wear-free, and are exceptionally adaptive. They open up new creative scopes to develop standard modules and application-specific special solutions.

Complex parts are feasible

There is no doubt that the main advantage of additive manufactured components is the enormous degree of freedom with regard to the part geometry. Design engineers don't have to pay attention to draft angles, or undercuts, and can strike new paths. Channels for power, signal, or compressed air feeding can be directly integrated in the gripper. Complex components, which are manufactured in the conventional way with great efforts, can be comparably easily manufactured with the layering technique. And also moveable parts, such as hinges, can be manufactured in a single piece, and many elaborate assembly steps are not necessary. Since the components are directly generated from the CAD system, manufacturing time is reduced considerably. Particularly in case of individual solutions manufactured in small quantities, additive manufacturing offers enormous advantages in regards to cost and time. Depending on the complexity of the application, Schunk can calculate within a 1 to 2 weeks lead time for engineering and manufacturing individually designed gripper fingers. Due to the low weight of polyamide modules, further effects arise: the light polyamide components offer optimum preconditions for shortening cycle times, reducing energy consumption, and for the use of smaller robots and handling systems.

Today, the modern laser-sinter plants are used for chipless and tool-free manufacturing of different modules from light and wear-free polyamide PA12. The program comprises one-pieced grippers with an encapsulated actuator diaphragm for hygiene critical applications, by individually formed, flexible gripper fingers, to additively manufactured quick-change systems, which are directly integrated in the gripper or gripper fingers, and if required, they can be equipped with media feed-throughs. Even complex contours or individual markings are feasible without additional costs. Since polyamide is chemically resistant and food compatible, it can be also reliably used in conjunction with aggressive media, and in the food-processing industry.

Maximum cost transparency

The function of Schunk is not limited to manufacturing components. Instead, it is more about being a competent problem solver for implementing sophisticated handling solutions. Schunk developed additively manufactured polyamide fingers for the automotive industry, used for verification process of induction forged precision components and considerably shortened the whole verification process. Gripping modules are used in a measuring cell, and in one single process step three component features can be optically con-trolled without having to change the gripped position. The internal gearing, the number and shape of the teeth; the tapped hole, this means the position of the bore hole and the number of thread convolutions; and the symmetry of the lateral milled slot. For this purpose, the Schunk universal gripper PGN-plus is equipped with individually shaped polyamide fingers in a way that the test position of all relevant features is visible at the same time. The reflection-free surface of the fingers ensures that the light of the camera illumination does not reflect. The low weight of the gripper also pays off: it has been the precondition that the available robot could be used again. In order to use the test cell as universal as possible, Schunk has additionally equipped the gripper fingers with a standardized jaw quick-change system, which allows a fast exchange of the gripper fingers, and that the plant can be retrofitted with a new spectrum of parts. In order to achieve a maximum cost efficiency, Schunk is the first supplier who offers fingers, quick-change systems, and the engineering design at an all inclusive price. Since components can be manufactured and re-ordered within a few days, this manufacturing process is excellently suitable for manufacturing prototypes, and wear- or replacement parts.

The perforation gripper handles sensitive parts

In addition to the individually designed special solutions, Schunk also uses the additive manufacturing process for further expanding its standard module program. The additively manufactured LOG gripper is the lightest gripper on the market, and is offered at an attractive price. Compared with conventional rubber perforation grippers it has been possible to reduce the dead weight by about 60%. Moreover, it disposes of higher holding forces, and allows longer service lives. The module can be compared with an expansion arbor, and is a one-piece design with an encapsulated, and therefore dirt resistant diaphragm system. Moreover, an internal stop protects the expansion diaphragm against damage. When the gripper is actuated with compressed air by an external or internal thread, the diaphragm expands, and affects the gripper jaws. Due to the frictional locking they ensure secure hold. Since the polyamide jaws have large surface contact inside the workpiece, damages at the workpiece never happen. If the air pressure is reduced, the diaphragm automatically draws back to its starting position, and the gripping jaw releases the part again. The LOG gripper offers ideal prerequisites for handling sensitive parts such as sand cores. Its standard version is available for diameters between 20 mm and 40 mm. At a dead weight of 10 g to 135 g it can handle parts between 1 kg and 4 kg. Since it is equipped with connection threads, it can be quickly and easily assembled without needing any tools.

Polyamide cover for gripper stations

The additively manufactured components also open up new opportunities in the field of robot accessories. The active dirt cover SWD for example, protects changing systems with stored grippers against dirt, chips, grinding and welding dust. Instead of traditional dust covers with leather aprons, and swivel cylinders, the thin, weight-optimised and coolant-resistant polyamide covers do not require any additional attachment parts for mounting, and are tailor-made inserted and locked. They close tightly and no dust can enter the mechanics or the electric connections of the stroked effectors. They are offered with the smart dust covers in nine sizes for all quick-change systems SWS with payloads between 25 kg and 200 kg. On request, they are also available for other electric modules and pneumatic gripper change systems GWS. Due to the enormous advantages, which can be achieved with generatively manufactured modules, Schunk is going to extend its standardised module program in the field of additive manufacturing. Particularly individual solutions will continuously be pushed forward, and will be designed even more creatively.