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Automation Technologies 3/2015

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Automation Technologies 3/2015


CONTROL AND DRIVE TECHNOLOGY Grinding robots prove their worth under harsh conditions Ralf Högel System supplier Automations Robotic has opened up a whole new dimension with its fully-automatic grinding cell for chassis components that offers 99.65 % system availability. The robotic cell with two Yaskawa six-axis robots also sets benchmarks in terms of autonomy, output and flexibility. Company name: Yaskawa Electric Corporation Established: 1915 Headquarters: Kitakyūshū, Japan Turnover: $ 3,3 bn (2012) Employees: 14,600 worldwide Products: Industrial robots, inverters, servo drives, … About When Automations Robotic directors Walter Schaffhauser and Alexander Steiger and their team closely examined the requirements and specification of a renowned automotive supplier for a planned robotic grinding system, they found themselves increasingly questioning the feasibility of the project. The task seemed simple enough: the grinding, in defined areas, of structural components made of die-cast aluminum. What initially appeared to the experienced system integrators to be a standard application quickly became a genuine challenge due to a number of restrictions and special requirements. recalls Walter Schaffhauser: “Even taken in isolation, the specified maximum cycle time of 30 seconds for the complex grinding operations is very difficult to achieve. However, the requirements of flexibility and availability made us actually doubt the feasibility of the entire application. Despite a great confidence in our collective know-how, it takes courage to guarantee 99.65 % system availability in three-shift operation under the harshest of operating conditions.” AUTOMATION TECHNOLOGIES 3/2015

CONTROL AND DRIVE TECHNOLOGY How it works In cooperation with the automotive suppliers the AR team developed a solution. The fully-automatic grinding cell is divided into two robot sections with a total of three grinding areas. The varied grinding tasks on the chassis components are shared between the two Yaskawa 6-axis robots, with the larger MS 80W in charge of operations in the cell while the smaller MH 50 performs the tool-guided grinding tasks. Thanks to its considerable reach of over 2.2 m and payload capacity of 80 kg, the MS 80W is able to perform the complete handling of the components and the workpiece-guided grinding tasks. At first the structural chassis components are transported to the robotic cell on a conveyor belt. Once a part has reached the defined unloading position, a window in the robotic cell automatically opens, allowing the large 6-axis robot to reach out to the conveyor and fetch it into the cell for machining. The door then closes, hermetically sealing the cell, and the grinding operations can begin. The large 6-axis robot then carries out various workpiece-guided work steps. It then transfers the part to a clamping fixture where the MH 50 executes further tool-guided grinding processes. AutomationsRobotic has coordinated the processes in such a way that the robots can work at their respective stations simultaneously and there are always two structural components in the cell at any one time. Once all the grinding is complete, the MS 80W removes the part from the clamping fixture and sets it back down on the conveyor belt. Alternatively, the parts can also be offloaded to enable integrated quality inspections. Hundreds of possible machining variants Automatic compensation for wear of the grinding materials is a very crucial factor here. The state of the abrasives is monitored by means of sensors. The motion paths of the robots are then automatically adjusted on the basis of this data. Making it possible to meet the strict requirements of the automotive manufacturer with regard to consistent machining quality and process reliability. Walter Schaffhauser is particularly proud of the programming options which include an impressive range of stored machining variants: “Five surfaces that are always to be machined are defined for the structural components. In addition to this, there are 29 further surfaces for optional grinding, depending on the degree of wear to the tools. The operator can directly select each of these surfaces individually on the visual display. Theoretically, freely combining these surfaces results in more than 800 machining variants.” “Failure is an unknown concept” Complying with the specified system availability of 99.65 % in extreme conditions is a very difficult task. Once the six-axis robots start their grinding operations, extremely fine grinding dust settles everywhere over the robots, even visibility is almost down to zero. By installing the most powerful dust extraction systems, the enormous strain placed on the robots by the grinding dust is thus taken care of. In the 1,440 minutes of a complete working day, the maximum downtime for cleaning the system or replacing worn abrasives is just five minutes. “The fact that we were able to achieve this incredible availability is primarily due to the quality of the Yaskawa robots that serve uncomplainingly. For these six-axis robots, failure is an unknown concept – even in three-shift operation under such extreme conditions,” says Alexander Steiger. Photographs: Ralf Högel The larger robot can perform the complete handling of the parts and the workpieceguided grinding task