Southern Manufacturing Group (SMG) of Morrison, TN, makes automotive components and industrial valves. In 2012, the automation system for its 175-ton hydraulic forming press received electrical damage resulting from a lightning strike (Figure 1). Purchasing a new hydraulic forming press would be prohibitively expensive — in the range of hundreds of thousands of dollars. Therefore, SMG needed a company that could repair the forming press in a short timeframe to maintain its production schedule.
Required repairs included either replacement of components on the existing antiquated automation system, or a completely new automation system. The decision to either repair or replace would be driven by multiple considerations including cost, schedule, and functionality of the old versus the new automation system.
Repairing and Improving the Press
Although the press was 40 years old, it was still a very robust machine worth repairing. A dual-action press, it shapes two separate parts in different ways at the same time. During the first step, the hydraulic forming press bends the metal in half without creasing it. In the second step, it rounds the metal piece. After the first step, the metal piece moves to the second step, and a new piece is inserted into the machine for bending. This continuous process significantly increases production yield as compared to simpler machines that only shape one part at a time, but it also requires more than a simple automation system, as multiple operations need to be controlled simultaneously to close tolerances.
In order to get the hydraulic forming press working again, SMG turned to fully licensed electrical and mechanical contractor American Construction Technologies (ACT) in Nashville, TN to find an economical and timely solution. When ACT inspected the press, its engineers were faced with multiple challenges, including the repair or replacement of the automation system. ACT contacted KCC Software in Huntsville, AL for an automation solution that would not only work with the existing machine, but also improve it.
KCC Software specializes in software programming and technology integration for manufacturing customers. While ACT would build the new automation system enclosure and perform all wiring, as well as improve and update parts of the hydraulic system, KCC Software would create a new, modern automation system.
Designing the New Automation System
Even presses designed ten years ago often don’t have the automated features and functionalities that help manufacturers decrease cycle times and improve production consistency. For example, the old automation system couldn’t automate press runs, so operators needed to manually enter instructions with each job setup. Not only did this add to cycle times, it also significantly increased the possibility of error and inconsistent part runs. The old automation system also lacked modern features and functions, and was becoming difficult to support.
For these and other reasons, SMG was willing to consider replacement rather than repair of the old automation system, provided the replacement system could be designed and installed quickly at a reasonable cost. Preliminary investigations were sufficient to allow KCC Software to satisfy SMG’s requirements, so design of the new automation system began.
KCC Software began designing the system by considering the system requirements — pressure transducer feedback, encoder feedback, fast response times, accurate and timely valve controls — indicating that a very flexible controller was needed.
KCC Software selected the Do-more series PLC CPU module and a high-speed counter module from AutomationDirect (Cumming, GA) to interface to the encoder on the press. The other I/O cards selected for the PLC were standard DirectLOGIC 205-series cards for the discrete inputs and the relay outputs required by the press, along with an analog input card for pressure transducer feedback.
The PLC offers programs and tasks that are essential to a well-designed automation system controller program, particularly for this application. These features enabled KCC Software to separate the code into manageable pieces; its programs and tasks can also be employed multiple times inside a program, as well as to develop new programs.
A key step was programming the force of the hydraulic press to match the preset movements of the machine. The correct pressure, together with the corresponding ram travel plus other key parameters, were stored in the new controller’s memory by job number, and were configured to be automatically preset by the die setter. For deep drawing operations, the blank holder or hydraulic die cushion force was programmed to be varied through the press cycle, improving operations and reducing machine wear.