Eitel Presses Deliver Precision Straightening with Windows-based Real-time Control

To efficiently combine high-speed mathematical calculations with reliability and flexibility, Eitel Presses built their state-of-the-art control platform on Steeplechase VLC and the INtime RTOS for Windows; giving them a competitive advantage that cannot be easily duplicated.

The rapid increase in the use of embedded PCs for industrial control systems is a natural outgrowth of designers’ interest in building machines with enough flexibility to adapt to constantly changing requirements.

Using a Windows PC to provide human machine interface (HMI) functions alongside PLCs that perform general machine control is commonplace, but PCs can do much more than implement just an HMI. Windows PCs are capable of implementing reliable real-time control and high-speed data acquisition when augmented by a tightly-coupled real-time software environment.

High-Speed Mathematical Computations

Eitel Presses of Orwigsburg, PA, has produced machines governed by PC controls since the late 1990s, when they undertook a project to migrate their PLC-based control systems to incorporate a Windows-based platform. The migration was driven in part by the fact that some of the mathematical calculations they need to perform couldn’t be done efficiently by PLCs. They needed a more general-purpose computational element in their systems. The system architecture Eitel developed is referred to internally as ORCA (Open Reliable Control Architecture).

Eitel’s presses provide precision straightening for heat treated metal parts to the automobile industry. Parts such as valves, crankshafts, pinions, and axles are typically out of alignment when they exit the heat treatment process. Eitel equipment straightens these parts to tolerances as tight as 20 microns, with a repeatability of measurement equal to two microns or better. High-speed mathematical computation is required to make the part-straightening cycle times fast and precise.

Double the Performance

With incorporation of real-time Windows PC control, Eitel’s Automatic Mechanical Straightener (see photo above) reduced the straightening time of camshafts to 10 seconds, compared to 20 seconds using their previous generation of PLC-only controlled machines. In addition to calculating the straightening algorithm, the Windows PC provides a connection to manufacturing and enterprise networks, implements the HMI, rotates the parts being straightened, and hosts a data collection card that obtains dimensional measurements on the parts during the straightening process. The Windows PC also functions as a conventional PLC, controlling general machine I/O functions, such as activating solenoids for parts transfer on and off the machine.

Real-time Data Acquisition and Control

High-speed data collection plays a major role in achieving the machine’s impressive cycle times. Shaft straightening is performed over multiple rotational cycles. During each rotation the shaft’s deflections are measured, by laser or linear variable displacement transducer (LVDT), and its rotational angle is tracked with an encoder. One rotation results in 256 measurements being made by the real-time Windows PC. The part is typically rotated at 60 RPM with a servomotor, also controlled by the PC.

Reliable and Flexible Platform

The only reluctance Eitel had to adopting a Windows PC as a control element was their concern for system reliability. At the time Eitel chose Windows to be part of their ORCA platform, PCs had the reputation of being prone to software crashes; Eitel needed a software environment that was robust, with a high degree of numerical performance, included flexible expansion options, and had the easy-to-use features of the Windows platform. After evaluating multiple PC-based software alternatives for managing control and data acquisition functions, Eitel chose the VLC package from Steeplechase, a division of Phoenix Contact located in Ann Arbor, MI. Using Steeplechase VLC, Eitel’s designers quickly implemented a flowchart design to control the servo drives and facilitate data collection from the data acquisition card.

In addition to wanting to use a flowchart-based design approach, another key reason Eitel cites for selecting VLC was the INtime real-time kernel underlying the VLC software. Key to meeting the performance requirements of the Eitel application was the need to implement machine-dependent functions, such as servicing the data acquisition card and performing Eitel-specific straightening algorithms, that would not be affected by non-control Windows applications in the system, such as the HMI and enterprise network components.

INtime, the real-time operating system (RTOS) provided by TenAsys Corporation of Beaverton, OR is based on software technology that has been proven by over 25 years of use in thousands of mission-critical Intel Architecture applications. Working in parallel alongside Windows, the INtime RTOS insures that time-critical applications always have priority over non-time-critical Windows processes.

Custom Real-time Control Blocks

With the help of TenAsys engineers, Phoenix Contact developed a means by which OEMs can extend Steeplechase VLC with custom real-time PLC function blocks. These custom function blocks, created using the Steeplechase C-Toolkit and a standard Microsoft® Visual Studio compiler, execute on the INtime real-time kernel and expand the functions and features available in the Steeplechase VLC programming environment, without requiring that a PLC programmer have to understand or even see the implementation details of the real-time function block.

The process of developing the C-Toolkit extension for Steeplechase VLC was simplified by the fact that the INtime development environment is completely integrated into Microsoft Visual Studio. Integration with Visual Studio allows the process of editing, compiling, and debugging real-time applications for the INtime RTOS to be done in a familiar environment using modern, up-to-date software development tools.

Using the Steeplechase C-Toolkit, Eitel engineers developed custom application code for Steeplechase VLC to run on the INtime RTOS. The Eitel real-time code manages the complex action of reading and processing information from the data acquisition card before it is passed back to Steeplechase VLC for control of Eitel’s straightening press. This flexibility of the INtime RTOS, to simultaneously support multiple real-time processes, is what allowed Eitel to create a fast and precise control system that can be easily programmed by their end users.

Steeplechase VLC also controls two press servomotors through a PC motion control card. Servo drives power the straightening function and rotation of the part for measurement. They also provide encoder feedback for the straightening algorithm. Standard motion control function blocks included with VLC, combined with function blocks developed by Eitel, form the core elements in the system.

Familiar Flowchart Programming

The Steeplechase VLC programming environment is very user-friendly and easy to troubleshoot. During application development, designers can view the values of variables in real-time as VLC programs are being debugged. Eitel’s customers also have the ability to modify VLC programs to make application-specific changes themselves—giving Eitel a distinct advantage over competing “black box” systems that require vendor support for even simple modifications.

Data Archive for Quality Control

After straightening, information about each part, before and after deflection measurements, and the cycle time required to make corrections, are stored on the PC's hard drive. Additional information can be collected to help the customer troubleshoot upstream processes that affect the straightness of the part. The customer can use this information to improve his process, yielding better quality parts and improved cycle times. Some applications, such as those involving the straightening of aircraft parts, require that such information be archived for each and every part manufactured on the line.

A Real-time Platform for Growth

“Due in large part to the reliable VLC/INtime software environment, the AMS system has proven to be fast, quiet, and environmentally friendly,” said Karl Klemsche, Eitel Vice President. “We are now building machines around the second generation of the ORCA architecture.”

The new generation of ORCA systems incorporates adaptive controls that adjust the straightening stroke infinitely, based on the measured deflection before straightening. Other benefits include plotting thermal infrared (TIR) imaging curves and surface geometry, multilingual HMIs (including Japanese), and automatic flaw detection systems.

“We feel that the VLC/INtime software environment gives us a competitive advantage in our market that cannot be easily duplicated,” added Mr. Klemsche.