At its main factory in Loßburg, in the Black Forest, the machine builder uses it to bend the machine bases for all injection molding machines from large-scale sheet steel with a thickness of up to eight millimeters.
Over time, the aging hydraulic system struggled to guarantee the required accuracy; in addition, obtaining spare parts, including those for the control and drive technology, was becoming increasingly difficult and expensive. The production managers saw the need to intervene proactively and prevent the worst-case scenario of a lengthy unscheduled failure of the key press with a comprehensive retrofit. To avoid disrupting the company’s ability to deliver, a maximum production downtime of five weeks was stipulated.
Integrated automation ...Press manufacturer Dieffenbacher, who updated the mechanical and hydraulic systems, and the retrofit experts at Koch automation in Ilsfeld, Germany, responsible for the electrical and automation aspects, developed a new automation solution based entirely on Siemens components and implemented it in record time.
All the electrics were removed from the press, the sensors were all replaced, a new displacement measuring system and a second displacement sensor to monitor the slide (tilting) movement were installed. In addition to new control, drive, and HMI technology, Koch also implemented the control cabinets and terminal boxes for the power and control sections of the press, as well as the shuttle carriages used to push out the finished parts.
The new main press controller is a Simatic S7-300F with a fail-safe CPU, which in turn enables fail-safe communication with actuators and sensors in the press via the Simatic ET200S distributed I/O modules and Profibus. In addition, the drives for the six tool adjustment axes – two of them on the infeed plane, four in the upper area – were replaced by modern equivalents consisting of modular Sinamics S120 converters and S-1FK7 servomotors from Siemens. Instead of two conventionally equipped operator panels (one of which was installed on the press) there is now a central TP1500 Comfort Simatic panel with a touch display for monitoring and control in sight of the process.
... for safe and convenient press operation
A sequencer-based bending process was implemented based on the prior process but with completely new programming and visualization. Thanks to the EPos basic positioner
function in the Sinamics S120 drive system, precise synchronous operation of the four upper and two lower tool adjustment axes in master-slave mode was achieved with little time and effort. As a result, the press operator can now re-bend a finished enclosure as required – for example, if dimensional variations arise following reset due to the different material properties.
The new solution also makes it possible to continue bending directly following a fault-based interruption of the process in automatic mode. This was previously not possible and occasionally resulted in complex rework or scrap. The second displacement sensor, in conjunction with the additional monitoring in the controller, safely prevents the press slide from tilting in the event of an asymmetric load.
Functions such as two-hand operation and valve monitoring for machine and personal protection are implemented via standardized, certified press safety modules for the Simatic S7-300F. Standstill monitoring for the Simotics servomotors is implemented via the Safe Stop 1 (SS1) safety function within the Sinamics S120 drive system. This, together with Profibus communication and the Profisafe protocol for the main controller, saved on additional safety hardware and wiring requirements.
Transparency for efficiencyA controller for all tasks and the field bus technology also significantly increase the flexibility and simplicity of the component connections in distributed terminal boxes in and on the press. This is particularly useful when old schematics need to be implemented using new technology.
Set-up, monitoring, and control of the press is now also far more convenient, transparent, and thus efficient with the touch display on the central HMI. The new operator panel visualizes all activation conditions in clear graphical form, thereby facilitating operator guidance. Displays of all operating states, operating and fault indications for each bus device makes it easier to localize faults and thus reduce downtimes. Bending programs that have been created can be stored in the panel’s tool data memory using the Siemens devices’ standard recipe management system with up to 500 tool data sets and called up whenever necessary.
Wolfgang John, head of department at Arburg, is very pleased with the results, and in particular with the speed at which this modernization project was completed: “With the Siemens equipment we selected, both the reliable function of our press and supplies of spare parts are now assured for many years.” He adds that it is rare for such complex projects to be completed so far ahead of schedule. Instead of the planned five weeks during the summer vacation, the team from Dieffenbacher and Koch required just four weeks prior to restarting the press.
The modernized key press has since been running reliably and without faults – and will continue to do so for many years. Machine enclosures can now again be bent into shape accurately and more conveniently than ever before, and the availability of spare parts has been secured for the long term. Last but not least, the process can also continue seamlessly after interruptions, thereby saving on rework.