Machine Tool Control
New CNC gear and software spur shop-floor productivity
By Patrick Waurzyniak
Shop efficiencies start with the machine tool controller, as today's CNC equipment offers machine operators myriad tools for improving part surface finishes, allocating machine time, and cutting job cycle times.
With the latest CNC gear, manufacturers typically get a much easier-to-use controller packed with built-in software, allowing machinists to handle many programming tasks right at the control.
An affordable midrange control, the Siemens Sinumerik 828D CNC released last year is aimed at job shops seeking a cost-effective but feature-rich machine controller that uses the Linux operating system, new applications software, and the ability to receive and send text messaging to view a machine tool's status and alter its functions with return messages.
"One of the biggest hooks is that the software version on the 828D is the same that'll be on the 840D—it's the same look-and-feel across the line," notes Randy Pearson, manager, dealer and end-user support, Siemens Industry Inc. (Elk Grove Village, IL).
The Siemens 828D also features an updated HMI, called Sinumerik Operate, that combines Siemens' previous HMI Advanced and ShopMill/ShopTurn HMIs that incorporate help functionality on every screen. With its new Animated Elements help capability, machine operators can easily navigate through complex jobs with the built-in simulations.
"You go to the screen, a little animation pops up and shows you how it works," Pearson adds. "In the past, what we had was more static. This way it shows how a drill moves, or how a tool does a conventional cut, with the animations."
The 828D is a panel-based NC unit that contains no battery, fan, hard disk, or any moving parts, Pearson adds. The company's choice of an embedded Linux open-source operating system helps minimize the requirements associated with Windows-based machines and improves protection from malicious viruses that target the Windows operating system while the machine is connected to a plant-wide network, he adds. "It's stable, and if you put it on a network, nobody's bothered to write viruses for it," Pearson observes. "It's stable, it's simple, and it boots fast."
Aimed at production-type three and four-axis machining, the 828D is less expensive than the company's flagship Sinumerik 840D control, which handles more high-end, complex machining chores such as five-axis aerospace, medical, or automotive applications.
"We've positioned the 828 as a compact control that is really geared in terms of functionality and price to be in the midrange area," notes Jon Cruthers, manager, business development, Siemens Industry Inc., "whereas the 840 has a lot built-in, and there are not a lot of options. The feedback that we get from machine tool builders is that it's priced aggressively."
Advanced connectivity functions on the new control include Siemens' Easy Message system, which offers simple production status monitoring by text messaging. Depending on a user's profile, the machine can transmit information about workpiece machining status, report on the tools in use, and send machine maintenance bulletins to mobile phones at any time.
"One of the really neat technologies is the Easy Message feature," adds Pearson, noting setup of the system is quick. "People are asking for this all the time. It kicks out a message and you send a response back to the machine." Many users operate the system using prepaid mobile phone GSM cards that simply plug into the machine.
For high-end aerospace applications, Siemens steers customers toward its Sinumerik 840D control, which offers many technical advantages, including its Volumetric Compensation System (VCS), mandated by the need to fabricate extremely large aircraft parts using gantry mills and other big machines. The high precision requirements specifically for the Joint Strike Fighter F-35 fighter plane program also necessitate using top-end controls (see the article "Precision Machining" in the January 2009 issue of Manufacturing Engineering magazine.)
"The VCS option for the 840D has really been a big advantage, particularly for aerospace, both on the commercial side with the 787, and especially with the JSF," Cruthers states. "We see a ramp-up for full production of the 787 in the future, and through the Tier suppliers, but it's not quite there yet."
Medical applications mirror what's happening in aerospace, Cruthers adds. Likewise, there is good demand in the heavy-equipment market from commercial construction, he says. "We get the sense that the weak dollar is making our equipment much more attractive to the Chinese market, far less expensive than the Japanese equipment," Cruthers says. "Automotive is another strong market for us, and it will come back in the future, once they get things straightened out."
CNC evolution lately has focused around improving the productivity of individual machines and integrating the machines into the overall factory system, notes Paul Webster, manager, product engineering for Fanuc CNC America Corp. (Hoffman Estates, IL).
"The recent economic climate has highlighted the need to increase productivity without capital expenses or labor increases. This means getting more out of each machine, and automating the machining process," Webster states. "Control-system development has followed this approach. To assist machine operators, maintenance personnel, and supervisors, we are seeing improvements in machine operability, reliability, and connectivity."
With the dissolution of the former GE Fanuc Automation last December, all CNC development, marketing, and sales of Fanuc control systems is handled by Fanuc CNC America, Webster notes, while GE Intelligent Platforms (Charlottesville, VA) is focused on PLCs, process control/automation software, and embedded systems.
The most recent control from Fanuc is the new FS0i-D line, which was released last year and is designed to be price-competitive with many alternative solutions, he notes. "The 0i-D is a nano [nanometer] CNC that shares many of the features with the top-of-the-line 30i series of CNCs," Webster says.
For five-axis machining, Fanuc has made several significant advancements, he adds. "Improvements to smoothing functions—Nano-smoothing 2, and Smooth TCP 2 make sure the control system follows the path as fast and accurately as possible," Webster explains. "Following the programmed path is only part of the requirement for large five-axis machining—error compensation is also a large factor in these types of machines.
"Fanuc has addressed this concern with the release of 3-D rotary error compensation. This volumetric compensation feature allows for five-axis or error compensation within the entire machine envelope."
The recent release of interactive force compensation software dynamically corrects for the interaction seen in high-speed five-axis machines caused by the rapid acceleration changes of the linear and rotary axes, Webster adds. "This interaction reduces accuracy at the tool tip but cannot be corrected in the program without lowering feedrates."
Software enhancements help Fanuc controls used in everything from job shops to aerospace applications. "We produce CNC controls that are used by all sectors of manufacturing," Webster says. "The latest 0i-D has all the features required for most applications and shares much with the top-performing 30i, but at a much lower cost. Job shops can take advantage of the improved operability of the 0i-D or the high-end 3xi family, such as Manual Guidance, off-line CNC machine simulation, and more PC-like operation."
The advancements made in five-axis error compensation and accuracy were specifically designed to meet the needs of the aerospace market, he adds. In addition, aerospace applications use high speed, high-powered spindles that Webster notes were developed with the needs of titanium and other more exotic materials in mind.
"Automotive and other high-production industries can take advantage of productivity gains made by improving connectivity, especially the easy robot integration now available in the current Fanuc CNC controls," he adds. "Automotive is also able to leverage the high-speed machine- centric features and high-speed servosystems. Industrial machines such as stamping presses that are using ultra-high-torque servomotors for automotive body panels not only take advantage of the accuracy of modern servos but also the energy savings and safety advantages these systems bring."
Software updates from Heidenhain Corp. (Schaumburg, IL) for its contouring controls line include adding to the company's kinematics optimization and compensation features. Building on its Kinematics Opt software for users, Heidenhain has added Kinematics Comp for machine tool builders, which allows incorporating new compensation tools into machines using the Heidenhain iTNC 530 contouring control.
"When you commission a machine tool, in our control system, you detail every moving element of the machine and how they all relate to each other," notes Chris Weber of Heidenhain. "You can imagine on a five-axis machine, if I've got a tilt-swivel head, the possibilities in five-axis motion are pretty high to hit something you don't want to hit. Also as machines wear, and as machines warm up, those relationships change due to thermal expansion typically.
"Kinematics Opt allows you to go in on a machine and at fixed intervals, even between parts, go in and reset those values," Weber says. "As things start to drift a little bit, I can go in and re-comp based on the current machine status. It involves using a calibrated sphere on a table of the machine."
The enhanced Kinematics Comp software offers machine builders new tools for compensation during initial machine setups, he adds.
New high-speed machining algorithms are available on Fagor's controls, notes Todd Drane of Fagor Automation Corp. (Elk Grove Village, IL). "These high-speed algorithms optimize machining by obtaining higher cutting speed, smoother contours, better part surface finish, greater accuracy and better matching of the programmed surface," Drane states.
"The cumbersome machining of incline planes, which required loosening the part and wedging it, is now a simple operation with the Fagor 8070 CNC. All the customer does is simply orient the tool either manually or automatically after defining the incline plane, and thus they can carry out all kinds of machining operations, such as pockets, rotations, and other operations, without having to wedge the part, saving time and increasing productivity."
When machining spherical surfaces, the Rotation Tool Center Point (RTCP) function improves part finish, Drane adds, because the tool orientation changes to automatically position the tool perpendicular to the machining surface at all times.
In addition, the Dynamic Distribution of Machining Operations (DINDIST) feature of the Fagor 8070 CNC makes it possible to distribute the machining operations among the execution channels on multispindle lathes, he adds. "Just program the machining operations for a single turret, then once the DINDIST function is activated, the machining operations are automatically distributed among the turrets without extra calculations, making it possible to optimize and minimize machining time considerably," Drane says. "This feature makes turn-and-bore operations that are so common on multiturret machines extremely simple to set up and execute.
"Our research indicates the entire industry is starting a slow upswing," Drane adds. "The outlook is perhaps not great, but solid. We believe by 2012 the manufacturing market will have made a near full recovery."
Energy-saving features have been a focus for control systems development at Bosch Rexroth, notes Karl Rapp, automation and machine tool branch manager, Bosch Rexroth Corp.—Electric Drives and Controls (Hoffman Estates, IL).
"Starting with IndraMotion MTX ega for the CNC, Bosch Rexroth is now offering PLC logic and library functions combined with HMI screens so the OEM/user can implement measurable energy monitoring into the control system," Rapp says. "All data can be accessed via OPC and Ethernet TCP/IP for centralized collection in a facility. Bosch Rexroth Germany has several systems running to gather real-world data and measure the benefits.
"We in the US are currently looking for OEMs and end users to integrate the system to document energy consumption of the machine subsystems and measure savings after optimization," adds Rapp, who notes that it is somewhat difficult to find customers that are willing to release gathered information to the public.
In response to more integrated remote access of non-PC-based controllers, Bosch Rexroth has introduced Version 10 of its IndraMotion Service Tool, Rapp says. "With Version 10, users can utilize the benefits for Motion Logic [PAC] and pure Logic [pure PLC] controllers on a range of hardware form factors," he adds. "The controller provides a Web server with pre-configured screens, dialogs and tools [IndraMotion Service Tool] that can be accessed quickly via a Web browser for commissioning and customer service activities."
Since the controller hardware is connected via Ethernet TCP/IP, Rapp says that the connection can be local, in the Intranet, or via secure channels in the Internet for remote access. A built-in user-management setup assures access protection and security.
In servodrive developments, Rapp notes that Bosch Rexroth has installed tens of thousands of IndraDrive servodrive systems with integrated IEC61131-3 PLCs over the past few years.
"Some are single drives or multi-drive solutions with SERCOS III Ethernet connectivity," he says. "The OEM can integrate his own motion and PLC solution [IEC61131-based Indralogic], or they can choose from templates such as IndraMotion for Handling, IndraMotion for Trans, etc. The latest addition is IndraMotion Sequential Motion Control for the IndraDrive system, offered in March 2010. Now the user can load a project and without needing to write any PLC code, use a motion programming language to create his motion and I/O program across up to four independent motion channels and up to six axes—a fast and easy drive-based control system.
A motion editor usable on a PC is used to program, debug, and archive motion programs, Rapp observes, and a small HMI connected via Ethernet with finished screens also is available. "This saves engineering time and allows a common project in the drive control systems, but using machine/unit/station-specific motion and I/O programming for simple automation. If need be, then the user can modify the Bosch Rexroth-provided solution by adding PLC code."
For CNC users, new productivity-enhancing software from Bosch Rexroth includes the company's Cycle Time Analyzer (CTA) tools, which Rapps says offer a real-time recorder in the motion and logic of the MTX CNC captures data in the µsec range.
"The OEM can use the CTA to optimize internal motion, logic, and peripheral dependencies to a minimum time loss—making the control very fast," Rapp contends. "In CNC machines for high production, this can result in accumulative time savings per tool change, I/O interaction, etc., that results in very noticeable productivity gains, as shown by practical implementation experience."
Focusing on embedded systems, automation, and software, GE Intelligent Platforms recently introduced two new products for improving productivity, according to Kam Yuen, product manager, Control Systems, GE Intelligent Platforms (Charlottesville, VA). "The first one is our Boiler Bookshelf. Based on GE's state-of-the-art process control system, Proficy Process Systems, the Boiler Bookshelf is a preengineered solution including control strategies and screens for optimizing boiler control and operation," Yuen states. "The Boiler Bookshelf is ideal for Combustion Control, Feed Water Control, Burner Management, and Automatic Blowdown applications.
"The second one is the PAC8000 RTU Controller," he adds. "Designed for use in the harshest environments, the controller is ideal for all types of remote terminal unit applications, such as pipelines and wellheads in the oil and gas industry.
"The energy industry, in particular the renewable energy segment, is doing well despite the economic slowdown," Yuen says. "There are many factors, such as favorable government policies and concerns about climate change, that contribute to the rapid growth of this industry. In general, I believe that we will see growth in manufacturing in 2010. We are seeing signs that indicate the bottom of the market has been reached and the manufacturing segment is rebounding."
This article was first published in the April 2010 edition of Manufacturing Engineering magazine.