Real-Time Data Acquisition for High-Accuracy Diecasting

The increased popularity of high-pressure diecasting for automotive and other critical designs is based at least partly on the increased performance standards for diecasting systems. That performance is made possible by the expanded capabilities for data management and process control of diecasting technologies. One manufacturer of hydraulic diecasting machines relied on CAS DataLoggers for the data acquisition and control functions that power its presses. That is the data that defines and manages the process of filling dies with molten metal to form complex shapes that are another basis of diecasting demand — parts formed so reliably that they may not require final machining, for use in engines, transmissions, and other high-value automotive parts.

Controlling molten-metal injection has long been managed by PLC systems, but standard industrial PLCs lack adequate response times to maintain the tight control required to achieve fully formed parts of the proper density and minimum porosity, while controlling the speed, volume and pressure during the injection process.

The diecasting machine designers saw the need for a high-precision process control package that also performs data acquisition, for users’ quality-control requirements. The solution would have to monitor the pressure, force, speed, and displacement accurately, and in real-time during the shot injection and have flexible communications capabilities for communication with a PC.

The technology provided by CAS DataLoggers incorporated an ADwin-Gold real-time data acquisition and control system in a sturdy metal housing. The ADwin system monitors and controls the various analog and digital inputs during the shot injection, and interfaces easily with a Visual Basic application providing the HMI for set-up and monitoring tasks, including configuring the injection shot, viewing and storing real-time data.

All of the real-time control is achieved using the on-board analog and digital I/O of the ADwin system with sub-microsecond precision.

This 16-analog input channel system measuring at 18-bit resolution was connected to various sensors to monitor the pressure, force, speed and displacement effectively during the injection shot.

The ADwin-Gold system’s local, real-time CPU supports parallel, individually-controlled real-time processes while running independently of a PC’s operating system, providing deterministic operation with response times of 1 microsecond or less.

The ADwin’s CPU also controls signal acquisition and all measurements are recorded in real time onto 1 MB of external DRAM for data storage. Communication with a PC is done via an integral Ethernet interface.

The ADwin application runs on the processor internal to the ADwin hardware, and it is accessible by applications on computers running Windows, Linux, Mac iOS and other platforms. Multiple PCs communicate with the ADwin-Gold concurrently during program implementation and commissioning, and if necessary one PC also can access multiple ADwin systems as part of a network, to provide centralized monitoring.

The system is able to calibrate analog inputs and outputs and has drivers for many popular programming environments, including VB, VC/C++, LabVIEW, Kakkiste, among others.

The ADbasic application was created using the ADbasic development environment, in which users define the processing sequences executed on the ADwin hardware, optimizing and compiling the program code with a click of the mouse. The system’s real-time processes are executed independently after being loaded on the ADwin-Gold via ADbasic, or a graphical PC user interface.

ADbasic also contains the functions to access all inputs and outputs, as well as those for floating-point operations, process control, and PC communication. Users also have a library of standard functions (e.g., filtering, various examples for counter use, function generators, etc.), which helps them to implement the program quickly. ADtools offers a simple way for users to view their real-time data graphically or numerically, to visualize process sequencings or to set input values via potentiometers, sliders, or push buttons.