The requirements were complex: the company was looking for an automated handling solution that could remove standpipes with a length of 250 to 4000 mm and a maximum weight of 30 kg from the cutting machine after the cutting process, bundle them and transport them to the storage area on pallets. However, the space required on site is limited.

Image 1: Each of the four Scara robot arms is fitted with a vacuum gripper that reliably picks up the sheet metal tubes. Each suction plate can handle a load of 40 kg.

© SEW-Eurodrive

Special machine manufacturer RTT Robotertechnik-Transfer from Zittau developed and manufactured a handling and transfer unit with four Scara robots specifically for these requirements. Two robots at a time are mounted on two parallel guide rails under the hall ceiling and can move along the linear axis over a distance of 12 meters. Due to the arrangement, the gripper arms can be flexibly positioned according to the length and geometry of the different articles. The central elements for the Scara robots are precision servo geared motors, inverters and the Movikit Robotics software solution from SEW-Eurodrive's Movi-C modular automation system.

Designed with specific robot kinematics

As the robots are suspended from a guide, the weight of the individual arms had to be kept low. In addition, the task requires a special design with specific kinematics. For this reason, the upper and lower arms of the Scara robots are designed in an optimized lightweight construction. At the load pick-up point, a vacuum suction plate grips the tubes and transports them onwards for bundling and packaging on pallets(Fig. 1).

Figure 2: Two precision servomotors with gearboxes from the ZN series are installed on each Scara arm. All motor data is transmitted in real time to the application inverter and the associated networks. This allows all operating data to be recorded in detail and maintenance forecasts to be created.

© SEW-Eurodrive

Three drives are used for each robot arm: a servo bevel gear motor is used to feed along the carrier (Fig. 2). The other two drives are used to move the upper and lower arm. Servomotors are used here in combination with gearboxes from the ZN series, whose characteristics include zero backlash and precision at extreme acceleration torques. The torsional and tilting rigidity of the gearboxes enables the exact positioning and rapid movement of large loads with repeat accuracy and also offers the possibility of absorbing high torques. In addition, the compact design of the drive units enables installation even in small installation spaces. The motors are lubricated for life ex works, ready for installation and available in twelve sizes.

The Movi-C modular automation system offers a scalable system with engineering software, control and inverter technology as well as the appropriate motors. The configurable multi-axis system 'Movidrive modular' was used for the handling system described (see box).