One of the most limiting factors with modern-day control systems is the rigid link between hardware and software systems used to implement the control system. All too often personnel of a heat treating department generally can find hardware systems that are ideal for their application, but the accompanying software isn't really suitable for the special operations required. The software often does not provide the extensibility that is needed to create the business information system that allows management of the enterprise properly.

FPM Continuous Processing (Cary, IL) and Eurotherm Controls (Reston, VA) have now joined forces to provide a solution that satisfies both the process control and business requirements. Their solution provides:

1. the ability to format files and make in-house modifications;
2. the ability to share data between control and business files, as needed;
3. the ability to enhance portions of the business system with off-the-shelf software that is commonly available in the marketplace;
4. a high level of user-friendliness so operators don't have to be computer experts.

Heat Treating Capabilities and Desired Monitoring System The Cary facility, a branch of FPM Heat Treating, headquartered in Elk Grove Village, IL, specializes in continuous heat treating and most of their work is centered on mass processing of fasteners for the automotive, appliance and construction industries. FPM presently uses eight continuous case hardening furnaces (Atmosphere Furnace Co., Wixom, MI) with varying production capacities from 1,000 to 3,500 lb per hour (see picture right). Their most recent installation is a specially designed deep case carburizing furnace (AFC) capable of handling case depths to .020 inches. In addition to carburizing, FPM also austempers in three furnaces at this facility. Tables I and II present general cycles respectively for carburizing and tempering fasteners, according to GM6010M, and neutral hardening of 1075 carbon steel spring stampings.

Ideally, it was desired to create a common database in order to share data among systems on a network. This would allow working with common information, extending from pricing and customer history files to preparation of job quotes, labor data (payroll, time cards, etc.) billing, receivables, payables and even profit/loss statements. The intent was to generate heat treatment processing details as soon as an order was entered in the system and then track process operation through scheduling, materials, processing and product quality control. Monitoring all aspects of production in this manner should allow better management of this company's operation and improve productivity.

Integration of Major Components To integrate the systems required, FPM chose On-Line Resources (Roswell, Georgia). The machine control systems needed to manage furnace operation (PC 3000/Microcell—from Eurotherm Controls, Inc., Reston, VA) was selected because of confidence that the real-time data that it provides could be fed into the network for other uses (see Figs. 2 and 3). Software (InTouch—from Wonderware Corp., Irvine, CA) was added to provide the appropriate man to machine interface (MMI).

Fig. 2 Control panel for furnace operations and integration of data for overall plant operations

Fig. 3 Portion of circuitry and control instrumentation housed within the control panel.

Some Details of Control System

The control system provides total process control and integration in one system for precise control of both continuous and batch type processes. It can be operated from an industrial terminal, yet still provide extensive on-line statistical process control (SPC) analysis, recupe, and batch logging. Some advantages of this control system are listed in Table III.

The process controller, Fig. 4, incorporates analog, digital control, sequential control, statistical control and communications. This system simultaneously interfaces with multiple supervisory systems allowing data exchange. Interface to all intelligent line devices enables control of any subordinate system.

TABLE III Principal Advantages of PC3000 Control System

Fig. 4 Closeup view of program controller. Portion of a gas-fired continuous furnace is shown at left background.

Precise control of all furnace parameters -- not just temperature On-line SPC (X-bar, Std Dev., Cpk, UCL, LCL...) Open communication (Modbus, J-Bus, Siemens, Toshiba, Eurotherm...) Fewer pieces to integrate -- one PC3000 vs. many discrete controls for all furnace parameters (i.e. temperature, carbon, belt speed...) Easy to integrate with standard, off-the-shelf third party software packages Color operator interface with process graphics Easy to use configuration tool kit -- no programming expertise needed.

Data acquisition and control at the plant level is carried out through input/output (I/O) modules which provide low level interfaces to transducers and actuators. Various multi-channel analog input modules cover a wide spectrum of applications. They are designed with high accuracy, high stability and high resolution (14 bit) for thermocouples, resistance thermometers and most types of transducers for measuring pressure, speed, position, etc. (0-10V, 4-20mA etc.). Multi-channel analog output modules provide high stability, high resolution (12 bit) analog signals (0-10V, 4-20mA) for driving actuators, drives, thyristor stacks, etc. A range of digital input modules are designed for low and high voltage AC and DC applications as well as integral power supply for volt-free contacts. A range of digital output models provide logic level signals and relay contact switching at low and high volts AC or DC.

Communication ports can be used as masters to communicate to PLCs, discrete controllers, motor drives, intelligent transducers, gauging equipment, weighing machines, printers and systems, etc. They also can be configured as slaves for communication with host computers, supervisory systems, etc. This capability allows the process control system to act as a data acquisition unit, data concentrator and communications gateway in a complex network.

A data acquisition system allows the process controller to provide for collecting process and quality information from the hardware and store it to disk. Data can be logged on a routine basis as well as in accord with pre-defined change. Fault finding is facilitated with the high speed alarm log. When a fault occurs, these data are stored as record of exactly what happened before the alarm. Files may be pulled directly from disk by means of database, spreadsheet or network software, or they may be replayed as a video by the control systems graphics package.

The software (Microcell) tool allows definition of the I/O points, connection of the function block wiring, set up of the recipe templates or what parameters go into the recipe, configure the SPC function, and enter the process sequence. The furnace programs are prepared off-line using this software, and then down loaded.

The software provides a complete and comprehensive set of programming tools for creating and editing the furnace program, as well as provide for on-line debug of the completed application program. It is interactive with complete on-line help functions, allowing the maintaining of one database for all configuration and operating-time parameters.

The software for graphical presentation makes full use of all standard animation tools such as movement, color changes, etc. and also allows full mixing of trend charts, graphical pictures, and numerical data.

An object-oriented, graphical application generator (InTouch) for industrial automation, process control and supervisory monitoring applications allows users to draw and animate, on a computer display screen, software representations of the physical devices (gauges, meters, knobs, switches, etc.) used to control equipment in a factory or process control system. Because of its intuitive nature and its strict adherence to the easy-to-use Windows standards, very sophisticated applications can be created with significant savings in development time and effort. It also is an open architecture that allows the user to easily connect to other Windows applications.

Once drawn, graphic objects can be stored in a library for re-use in other screen applications. They can even be "intelligent" objects called "Wizards" that are pre-configured to perform specific functions that are the same in repetitive application use. Bit mapped objects are also easily imported into this software system allowing the generation of more complex graphics with other software packages or scan existing images for use in the program. All graphic objects are then linked dynamically to the PLC signals so that they can be animated or colored to indicate variable conditions.

The graphic software uses the Dynamic Data Exchange (DDE) capability of Windows as the basis of its I/O drivers (called DDE Servers). These poll data directly from the machine controllers (Eurotherm). The use of DDE means that data can also be shared with other Windows-based applications, such as word processors, spreadsheets and database programs. In addition, a networked version of this protocol, Wonderware's NetDDE, allows FPM and Eurotherm personnel to create DDE links transparently across networks, providing additional application versatility. This is especially valuable in providing the flexibility and connectivity to link FPM heat treating processes with other business applications.

Conclusions

The end result is that FPM has accomplished its original goal by combining one manufacturer's hardware with another's software package, to optimize their advantage. Any data that is needed anywhere in the company can be provided via this system.