Use of robots in manufacturing
Robot and machining cell can be controlled by one and the same CNC. A self-sufficient rotary drilling cell for the production of bearing caps at the Siemens plant in Bad Neustadt, Germany, shows how this works.
Employees, CNC and robots cooperate
How can handling robots be used easily and efficiently in combination with CNC machines? Peter Zech, head of die casting and special machine manufacturing in Bad Neustadt, has one answer. Together with his team, Zech revamped the machining pro- cess for bearing shields and caps with a turning and drilling machine. He explains, “The parts in the old system were still of high quality, but it wasn’t efficient enough anymore. The availability left a lot to be desired, and the drilling station had to be loaded manually - it was very monotonous work.”
Completely refurbished turning machine combined with a drilling station
Initially, the team discussed purchasing a new turning center that could have been used for the entire process. But repeated drilling, which a separate drilling station would complete in a single step, would lengthen through- put times, and investment costs would be much too high. Another option was to replace the existing Index GE42 with a new turning machine. In the end, though, a retrofit with new SINAMICS drives and SIMOTICS motors and SINUMERIK CNC system technology proved to be the best solution. Diecasting foreman Volker Ress explains why: “Since the general overhaul, the GE42’s mechanical quality and precision have met our needs perfectly. And the total cost of this solution was significantly lower than that of a new machine.”
Complete part handling
The turning machine’s retrofit alone, however, was not enough to satisfy Zech and Ress. Their plan: a flexible robot should be responsible for all parts handling within an independent turning and drilling cell - from the feeding conveyor system to the removal of the finished component. When selecting the robot technology, they quickly recognized that the KR Agilus from KUKA would be the best solution. “Other robots can carry out the same movements,” confirms Zech, “but KUKA is known for high quality. And the seamless integration of robotics into the machine tool environment is unique. The combination of the KUKA robot with Sinumerik 840D sl makes this possible.”
The CNC controls the robot
The solution is based on the Run MyRobot /Handling software interface, which Siemens and KUKA engineers developed together. Its major advantage is that machine operators are comfortable using it. Mechatronics and maintenance engineer Martin Leutbecher confirms this: “Run MyRobot /Handling is awesome. It means we can control the KUKA robot with SINUMERIK Operate on our normal panel or with the HT8 Handheld Terminal. We don’t have to use any other robot control system with features that we’re unfamiliar with.”
This means the entire production process for the robot and machine can be programmed offline - without a loss of turning and drilling cell availability. For tasks such as setting up, teaching and retracting the robot, the HT8 is used as the central control unit. Timo Rössler, a machining production technician, points out another advantage: “Operators can enter the manufacturing cell safely at any time - even while controlling the robot.” This is ensured by the SINUMERIK CNC’s built-in Safety Integrated feature. This function ensures that the robot can move only at controlled speeds.
Fully automated machining cell
Once it is set-up, the turning and drilling cell can produce series averaging 400 to 500 components per shift. Then the product is changed. “That’s how we maintain optimum stock levels,” explains Rössler. The feeder belt carries around 70 blanks - enough to leave the system running independently for two to three hours. During this time, the operator is able to work two additional processing lines and carry out random quality checks. After it is filled with blanks, the machining cell functions fully automatically: A vision system registers the blank and transmits the location signal to the robot, which then uses the location data to grip the component in such a way that it can always transfer the component to the Index GE42 in the correct position.
When the turning machine opens, the robot first uses the reverse of the exchangeable gripper to grip the completed component and then transfer the blank. It then passes the turned workpiece to the drilling station, which drills several holes or threads in a single step. Finally, the robot deposits the fully machined component and takes the next blank from the feeder belt - repeating the process until the next product change.
A good team
Run MyRobot /Handling makes the operator, machining tool and robot into a successful team. The secret to success? The operators, mostly cutting machine operators, are able to control two fundamentally disparate technologies using the familiar SINUMERIK CNC system.