Machine Controls Move Ahead
Open systems, faster processors, improved connectivity help improve manufacturing productivity
By Patrick Waurzyniak
Manufacturers today face extremely tough tests in cutting high-quality parts as quickly and efficiently as possible. To stay competitive, manufacturers rely on the latest machine controls as a primary way to help cut parts faster and improve factory productivity.
Today's most sophisticated controls combine open systems standards, faster processors and motion controls, improved HMI software, and the latest in connectivity for networking machines throughout the factory. With PC-based controls becoming more popular in recent years, machine tools typically enhance productivity by allowing operators the capability to run Windows-based shop-floor-management and other applications directly at the machine tool.
Software often can be an important differentiator for controls vendors, as easy integration of HMI software with machine tool controls is changing the face of controls in the factory. Rapid technological changes and the integration of PC-based platforms has caused machine tool control architectures to undergo a major transformation, according to Wolfgang Rubrecht, general manager, Siemens Machine Tool Business (Elk Grove Village, IL), (see the article "Software Spurs Controls Innovations" in the February 2004 issue of Manufacturing Engineering). "With the standardization of control hardware, the control manufacturers are trying to differentiate their products and expand the market by introducing innovative software features within the control system," Rubrecht says. As an example, he points to commercially available, off-the-shelf PC applications, such as remote diagnostics, which have displaced older, proprietary solutions like DNC that controls vendors had offered in the past.
Most major controls suppliers now routinely offer machine controllers that adhere to open systems standards for allowing the use of PC-based software and networking connectivity, but still keep the control's real-time operation isolated from Windows operating systems. The new Rexroth Indramotion MTX control introduced last fall at EMO by Bosch Rexroth Corp. (Buchanan, MI) takes that a step further, allowing what Rexroth calls true openness, where machine tool vendors can choose to customize the CNC kernel to meet their specific needs. The MTX is said to be open to corporate software as well as at the actuator and sensor level, with the NC and integrated PLC closely meshed.
"The openness of the CNC kernel probably only hits a small percentage of customers or OEMs," notes Rick Rey of Bosch Rexroth's Electric Drives and Controls unit. "Some OEMs are going to jump into the CNC kernel and make it exclusive for their machine, but more are looking for openness in terms of what we offer in open HMI systems, where they freely configure their screens, perhaps with our software or with their third-party Visual Basic design."
The open systems push in controls advocated employing the Windows operating system in order to help simplify operator interfaces used for complex machining operations. Some controls vendors in recent years have adopted PC front ends for Windows application compatibility, while still others have taken PC-based controls to fully software-only implementations, like Power Automation GmbH's PA 8000 soft CNC (Pleidelsheim, Germany), and the Windows NT-based OpenCNC from Manufacturing Data Systems Inc. (MDSI, Ann Arbor, MI), which to date have had some successes in the marketplace (see "Machine Control Options Widen" in the April 2003 issue of Manufacturing Engineering.)
Controls supplier Heidenhain Corp. (Schaumburg, IL) last year added Windows compatibility to the company's top-end Heidenhain iTNC 530 Contouring Control. The system employs a dual-processor architecture with two Pentium CPUs, one handling the real-time chores of the motion control and another ported to Windows 2000, says Chris Weber, Heidenhain product management, which gives operators access to Windows-based shop-floor applications at the machine tool control.
"You can't really call us a PC-based control for a number of reasons," Weber states. "Traditionally Heidenhain controls ran off a Motorola processor. Now we've ported our software or firmware onto a Pentium-style processor, so we're PC-based. The actual operating system in a Heidenhain control has nothing to do with Windows whatsoever. The operating system is called HEROS, which is Heidenhain Real-Time Operating System.
"We've always been a firm believer in separating PC applications from control applications, primarily because a CNC control is to run a machine," Weber adds. "Now obviously the market has had strong interest in being able to apply Windows applications in close proximity, if not within the control itself. Our answer to that was to add a secondary processor. So in effect, when you look at a Heidenhain iTNC 530 with the dual processor, that's exactly what you have--two separate processors."
Faster processing speeds through more sophisticated CPUs and enhanced internal communication bus technology mark the main features of the next-generation, top-of-the-line Series 30i-Model A control from GE Fanuc Automation Americas Inc. (Charlottesville, VA). The new 30i control features a host of new hardware and software upgrades over GE Fanuc's Series 15i-MB and 16i Model B, including using IBM PowerPC RISC CPUs, a much faster bus architecture, and a speedier digital servo system.
"All of the developments that we continue to make are developments to help our customers achieve overall equipment effectiveness [OEE], which is a way of measuring productivity," notes Bill Griffith, GE Fanuc Automation's CNC product manager. "We've improved our Mean Time Before Failure to 0.02 CNC failures per system per month."
Controlling up to 40 axes and eight spindles simultaneously, GE Fanuc's 30i control also is capable of running up to 10 independent part programs at a time. "It's a super-powerful control system, with an improvement in speed and operation," Griffith says. "It has lots of features, and its reliability is going to get even better."
With its proprietary, redesigned GTL bus, internal bus speeds have been increased by nearly four times over its predecessor, "We also added some hardware to do error correction code [ECC]," Griffith adds. "To make it more noise-immune, we added ECC." The system includes a CNC CPU, several DSPs, with one for each servo system, and separate processors for Ethernet connections. The control's digital servo system has been dramatically improved, and it also features an enhanced Fanuc Serial Servo Bus. Other upgrades are using flash card memory up to 8 MB for program memory, plus ATA memory cards to 2 GB maximum for the control's data server storage.
Open CNC compatibility also is available with GE Fanuc's Series 300is-Model A, which offers Windows XP/2000 as well as Windows CE. The control's latest software additions have made it possible to become a larger player in the rotary dial and transfer market, Griffith notes. "It also allows us to play in the multiprocess machines, like the Mazak Integrex. We've done a lot to improve our five-axis milling systems in the 30i, listening to end users to make a five-axis machine easier to program and use. A five-axis machine is very complex."
Aerospace machining typically places high demands on CNC controls, with the sophisticated controls like the top-end Siemens Sinumerik 840D, offering many functions necessary for five-axis machining, including special machine kinematics, five-axis transformation, orientation interpolation, high-performance 3-D tool correction, and NURBS and spline interpolation.
"Someone who comes from an aerospace tradition will recognize in the 840D a controller that comes out of its box seeking a five-axis application on an aerospace machine," notes Norman Bleier, Siemens' engineering manager. "Its employment of polynomial methods is a forward-looking strategy for an industry like aerospace that has the advanced programming skills and the mathematicians to work with their CAD and CAM vendors to do something with this. Its real-time, five-axis, kinematics independent transformation addresses the idea of design anywhere, machine anywhere. Its five-axis measuring cycle allows for frame transformations to adjust G54 (or whichever is used) to the tool as it sits cocked and out of square on the table in real time. There is no need to be constantly re-posting the program to account for geometry variables on the machine. Its open real-time kernel has allowed a variety of functions to be custom-prepared to broaden the control's suitability as a retrofit control that still has to maintain certain legacy properties of former CNC solutions, and not just former Siemens solutions.
"Aerospace is proposing new ways to manufacture airframes that require coordinated motion across hundreds of axes," Bleier adds. "The group that took the 840D from concept to product is still intact and directly engaged in outreach to the aerospace industry as part of a coordinated effort, constantly meeting with shop-floor-level personnel at airframe manufacturers and their suppliers to better understand their requirements and offer new functionality."
Simulation represents a critical area to today's aerospace production, Bleier notes. "Workpieces cost hundreds of thousands of dollars before they come to the machine and the machine can easily do another hundred thousand dollars of work," he adds. "Siemens is working with providers of simulation software to enable their software to use a copy of our real-time kernel with parameterization from the actual machine. This way when the user simulates his program he sees what the 840D is really doing."
Several aerospace suppliers have specified the Siemens 840D control, including major airframe manufacturers like Boeing, Lockheed Martin, Northrop Grumman, Airbus, and Canadair, and Cincinnati Machine has standardized on the 840D for all of their five-axis machines.
At WESTEC, Siemens plans to showcase control offerings that will include some enhancements to the 840D including faster processors. "Essentially, we are moving forward in increments," Bleier notes, "sometimes punctuated by bigger steps like our latest NCU board with its gigahertz microprocessor for super-fast PLC and NCU chaining to do applications that require coordinated motion between hundreds of axes."
Customized controls aimed at specific niches also are available from vendors like MDSI, which last summer switched its focus from offering software-only CNCs to a more pre-packaged type of solution that includes its OpenCNC controls software with inexpensive off-the-shelf hardware components. MDSI recently introduced a new grinding-specific control, the OpenCNC Grinder, which offers many functions customized to grinding operations. "Our main focus was to cover about 80% of the different techniques for grinding. That's where we really saw a place that would be a good fit," says Michael Mason, MDSI's managing director, of the OpenCNC Grinder. "Over the past year, we've been trying to determine where we can make life easier for our customers."
MDSI's OpenCNC features an open architecture with Windows-compatible software combined with SERCOS and Yaskawa Mechatrolink links to servo and spindle systems, plus a real-time kernel for motion control with VenturCOM's RTX operating system. In addition to OpenCNC Grinder, the company plans to release an embedded controls solution with a Windows CE version in upcoming months. "It's as though we're able to take Windows XP and scale it down and only use what we need," says Mason. "We'll have the ruggedness, there's no moving parts, and it's a lower-cost solution."
This article was first published in the March 2004 edition of Manufacturing Engineering magazine.