Assembly in Action: PLC System Guides Cylinder Assembly
October 29, 2009
Founded in Aalen, Germany, in 1981, Alfing Montagetechnik GmbH designs and builds automated assembly machines for customers all over the world, including many in the automotive industry.
Recently, the company took on a project to build an automated cylinder head assembly machine for one of its automotive customers. Normally, the company would have used CNC controls to monitor the system's valve-seat embedding station, because of the amount of data that has to be quickly processed if the operation is to be performed successfully.
However, the company ultimately chose to go with an IndraLogic CML40 programmable logic controller from Bosch Rexroth after Bosch Rexroth engineers assured Alfing Montagetechnik the system was up to the task.
Due to the valve seats' complex geometry and the application's throughput requirement, the system's axes had to be controlled rapidly and precisely. In addition, the line needed to be flexible enough to handle a number of different cylinder head types.
The finished system consists of two lines working in parallel. It can complete a finished workpiece every 30 seconds. In all, it accommodates three different product types, each in eight different configurations. This requires the system to process up to 1,300 I/O points and more than 1,000 diagnostic signals.
"This can't be done with a conventional PLC, as each cycle lasts 100 milliseconds or longer. With 30 to 40 consecutive stages, you lose so much time by comparison to a CNC solution, that it is impossible to keep to the required cycle times," says Alfing's head of controls design Gunter Niedermaier.
After seeing the Rexroth system first hand, however, Niedermaier says it was obvious that the IndraLogic technology could handle the needs of even an application as demanding as this one.
"To start with, we were a bit skeptical. But then it rapidly became evident that the cycle time of 12 milliseconds was something that did not just exist on paper. Experiencing the machine today means an encounter with a harmonized progression of movements with none of the stopping and waiting typically associated with a PLC," he says.
According to Niedermaier, using a single programmable control system, as opposed to having to integrate both PLC and CNC controls, offers a decided advantage from a production standpoint. In the short term, a unified system is much easier to program. In long term, it means his customer no longer has to make sure its own employees remain conversant with two different control systems.
Niedermaier adds that implementing the system was made easy by the support his company received during the integration process.
"We were very satisfied right from the start with the project support we received," he says. "Normally we get a catalog and then have to start by familiarizing ourselves with the product range. At Rexroth there was a single contact who was there for us from the first step to the last. Overall, the programming was very simple and expenditure on subsequent adaptations was kept within the framework of the budget. It would have been more expensive had we gone for a CNC solution."
For more on systems control, visit www.boschrexroth-us.com or call 800-739-7684.