The industrial division of Swiss company, Brüggli Industrie offers contract manufacturing and assembly services in the metalworking industry. To meet increasingly high quality standards in the face of rising production volumes, visual inspections were replaced by a fully automated test cell developed by ATS Automation, a company with a broad background in engineering, control and drive technology. Integrated PC control from Beckhoff ensured precise test sequences and dynamic parts handling using delta robots.
The delta robot takes over the entire handling of the test parts to check for punching and grinding errors, as well as dirt in the bores. The punched part is first removed from the feeding belt and placed in the front face test station, where it is checked for errors due to indentations by an inductive proximity sensor. In addition, dirt is removed by vibration with the aid of compressed air nozzles. A surface inspection then takes place on the test station. This produces three results, each based on 30 test criteria, which are evaluated by the image processing system and transferred as a final result to the control system. Depending on this value, the delta robot places the test parts on one of two discharge conveyors – the one for good parts or parts to be checked again, and the other a lateral reject channel for faulty parts.
A special feature is the hexagonal cell design. This allows all sides to be opened, improving access to the inside of the test cell. The location of the delta robot in the centre makes it possible to move the robot gripper to each position inside the cell at any given work height. In addition, the attached test stations can be swivelled out in setup mode, which also increases accessibility. The operator interface with the built-in panel PC can therefore be moved very flexibly, rotating almost 360° on its mounting arm. The panel is always within reach, but not in the way.
A built-in panel PC with 48 cm touchscreen and Intel Core 2 Duo processor (2,26 GHz) serves as the control computer and HMI, with Windows XP as the operating system and Beckhoff’s TwinCAT NC I as the control software. ATS chief executive, Andreas Tobler says, “The main advantage for us was the preconfigured robot kinematic function, which greatly simplified the engineering process. TwinCAT Kinematic Transformation (Level 3) offers an excellent solution for a delta robot as it is designed for efficient parts transport at high speed with a relatively simple mechanism.”
Due to the flexibility of TwinCAT, there was space for individual adaptations on the software side as well. Thus the positions of the delta robot are not controlled by an NC program as usual, but directly in software through the TwinCAT PLC. “From a conceptual point of view, we wanted to control the complete test cell from the PLC. A special function block was programmed for this to allow the direct specification of all positions,” Tobler adds.
A single parameterisation was sufficient for the engineering. This concept significantly simplified the sequence control. For example, the positions can be simply moved and fixed via the operator interface for robot teaching, without the necessity to change the NC program.
Five servo and two stepper motor axes provide dynamic implementation of the position specifications. Three dual-channel servo drives move the three robot axes or the rotary tables of the two surface checking stations, accomplished via five servomotors. In addition, two stepper motor terminals with stepper motors control the intermediate turning station, aided by two EtherCAT couplers and a total of 55 EtherCAT terminals for I/O data processing.
Tobler confirms the advantages of PC control: “To ensure optimal machine safety in every operational state, we chose the integrated Twinsafe safety solution. This is implemented with the TwinSAFE PLC, four TwinSAFE digital input terminals, and a TwinSAFE digital output terminal. In addition, there are drive option cards for the servo drive. The safety functions for emergency stop and safety door monitoring were implemented in this way. We benefit here from EtherCAT, which offers not only high performance, but also universal data communication. Our goal from the outset was to acquire I/O data, solve safety challenges and synchronise drives with one comprehensive bus system,” he concludes.
For more information contact Kenneth McPherson, Beckhoff Automation, +27 (0)11 795 2898, [email protected], www.beckhoff.co.za
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| Email: | [email protected] |
| www: | www.beckhoff.com/en-za/ |
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