Controlling the Factory
Updated controls gear adds more-powerful, cost-effective solutions
By Patrick Waurzyniak
With the latest machine controls, manufacturers are pushing the envelope on productivity gains as faster, more-productive CNCs and related software help machine-tool users boost machining efficiencies.
Machine-control builders recently have added more cost-effective and network-centric CNC solutions to the mix, along with enhanced software capabilities that aid users performing complex five-axis and high-speed machining tasks, and new safety gear for the factory floor.
Production machining and handling systems can take advantage of the new cost-effective IndraMotion MTX compact CNC platform introduced at IMTS 2006 by Bosch Rexroth Corp. (Hoffman Estates, IL). A space-saving, rackmounted version of the IndraMotion MTX platform, the MTX compact system extends Bosch Rexroth's CNC offerings with a lower-cost model aimed at production milling and grinding tasks on smaller CNC systems, multistation transfer machines, and handling modules.
The MTX compact, a controller-based CNC, handles up to eight axes in two NC channels including a fast IndraLogic PLC, according to Bosch Rexroth, and the unit processes as many as 200 NC blocks per sec. "We have two different scaleable MTX controls, but with the MTX compact, it's an actual controller that you can plug into a Windows CE device," says Rami Al-Ashqar, product manager, Bosch Rexroth Corp., Electric Drives and Controls. "You can plug in a handheld HMI; it also offers remote I/O, and the communications are SERCOS, just like the regular CNC system.
"It's a more cost-effective MTX that is able to control up to eight NC axes and two spindles, and the number of interpolating axes per channel is four," Al-Ashqar adds. "Part of the reason we have this scaleable hardware architecture is to give the customer better options. If he wants to spend less money, we have lower-performance systems; if he wants to spend more money, then we have better-performance systems."
Machine safety advances using built-in safeguards are being touted as an effective way to boost overall manufacturing productivity with improved safety and machine uptime (see the Viewpoints column, "Software Can Enhance Machine Safety," in the September 2006 issue of Manufacturing Engineering.) With Bosch Rexroth's Safety On Board software-enabled motion-control solution, safeguards for machine operation are built into machine tool drives for optimal performance. According to Bosch Rexroth, the Safety On Board features built into Rexroth IndraDrives can eliminate the reasons operators try to defeat or bypass safety.
Safety standards related to safe motion in Europe are now beginning to gain momentum in the North America, according to Al-Ashqar. Instead of using mechanical switches to power-off machines, the Safety On Board system uses safe-motionequipped drives to perform a safe stop with factory equipment. With Bosch Rexroth's safety system, machines can shut down in just 2 msec, Al-Ashqar notes, compared with competing solutions which range from 50–60 msec or even longer.
"The main thing is to have two redundant processors designed by two different organizations, so that way they can act differently but at the same time, they're safe circuits," Al-Ashqar states. "We're adding the second processor into the mix, and the second processor allows the drive to perform the safety functionality. It's certified by European [Norm] 954, and there are more standards coming next year where it will be recognized eventually by OSHA and other organizations.
"Everybody's pushing safety on their drive, because it is definitely the solution for the future, mostly because of the uptime. When you have safety on the drive, you can satisfy all the safety requirements without having to shut down the drive, saving a lot of downtime and setup time."
With its network-centric architecture, the new Sinumerik solution line CNCs from Siemens Energy & Automation Inc. (Elk Grove Village, IL) enables the next-generation controls platform to be effectively combined with Siemens' drive technology to design standalone and plant-wide automation solutions.
The new solution line consists of the panel-based Sinumerik 802D sl, the PC-based Sinumerik 840Di sl, and the flagship Sinumerik 840D sl control, which is available with either CNC-embedded or a PC-based HMI. The systems feature "thin-client" technology, with maintenance-free operator panels that work without a hard disk, battery, or fan, and the control's drive communications system, called Drive-CLiQ, provides fast recognition of drives and motors.
"Diagnostic features are improved with the new integrated diagnostics in the drive system, and with the Drive-CLiQ communications with the motor, the CNC control allows us to transfer much more diagnostic information between the individual units," notes Christian Kuhls, product manager, Siemens Machine Tool Business Unit. "Self-recognition of components, for example, allows people on the shop floor to ensure that they're getting back to the same configuration, and that components would be recognized by themselves; it's pretty much similar to plug-and-play for Microsoft."
The solution line's network-centric architecture also helps users track and analyze factory performance. "There's more and more demand for monitoring the production area, monitoring performance of machines, so you can identify machines that are your weak point," Kuhls notes. "You want to know the production time, the fault time of the machine, so you link all this information. Particularly in aerospace and automotive, there's definitely a high demand for networking machines."
With a new handheld terminal, users can perform setups and monitor machining cell processes using Siemens' new Sinumerik HT 8 handheld terminal, which integrates an operator panel and machine control panel into one compact device. The system enables users to visualize machine applications running on multiple Sinumerik NCU/PCU operations without reconfiguration, automatically reading the configuration from the HMI main panel of the machine while connected to it by a cable.
"The difference between a standard operator panel and an HT 8 is that this is designed to be carried around, going close to the process, going around your machine," Kuhls says. "If you have a large machine and need several operation locations around the machine, you want to save costs by not installing a stationary panel at each of these positions. We can just have the connection box installed at the position where you need that, and you can walk around the machine connecting your mobile handheld unit."
Five-axis and HSM software enhancements were demonstrated at IMTS 2006 by GE Fanuc Automation (Charlottesville, VA), with new features aimed at improving metalcutting performance with NURBS interpolation for HSM and complex five-axis machining. The company also showed updated capabilities in its learning-control functionality for parts cutting on typical machining centers and lathes, and also new learning-control techniques for rigid tapping.
Among its latest software, GE Fanuc has updated its Nano Smoothing feature for HSM users, as well as offering a new Nano Smoothing 2 function that aids metalcutting customers with five-axis operations. "Everyone in our industry knows that by using NURBS interpolation, you can get better accuracy and higher speed," notes Bill Griffith, GE Fanuc CNC product manager. "It's been proven that if an end user would just start using NURBS, he would be able to see the benefits of NURBS interpolation on his control system. In the end user community, no one's really used it, and the reason for that is that to use it, you have to purchase a new postprocessor and a new CAM system that support NURBS interpolation.
"We've created a feature called Nano Smoothing. Knowing that we have this great feature and no one's using it, let's take the output of the standard CAM system, the linear segment part program, load that into the control, and we'll do the NURBS curve fit of the linear segment. Then we'll provide the same accuracy and the same high speed as NURBS interpolation, without having to have the special NURBS CAM processor."
For five-axis machining, GE Fanuc has added a feature called Nano Smoothing 2, notes Griffith. "That allows us to take a linear segmented program for five-axis and do the NURBS curve fit on a five-axis program. It is very, very complicated to run that type of algorithm inside the CNC, but we do it," he says. "It provides the same accuracies and speeds as having a five-axis NURBS CAM processor, which would be very expensive."
A new 3-D interference avoidance system added by GE Fanuc allows users to track the radius of tooling and protects tools, toolholders, and parts from damaging collisions. "It makes operating a five-axis machine a lot easier, because before an operator that would operate a five-axis machine has to be very careful," Griffith adds. "You can imagine that if your part is tilted in space and moving along an axis, an operator really has to think about how he's jogging and moving the machine, or he is going to damage the part, the tool, or something on the machine itself.
"With this feature, the operator no longer has to be concerned about that, because before the axis would get to a point where you would have a collision between two devices that are not supposed to collide, there would be an alarm on the machine and we'd stop the axis," Griffith states. "It not only offers the operator the ability to know that he's operating the machine properly, but it also helps the programmer, because the programmer, as he's checking on a program, cannot damage anything. He can't run the tool into the clamps, or the tool into an area of the part where he doesn't want to machine."
Versatile, modular CNCs are in demand by today's machine tool users, who are looking for flexible approaches to manufacturing tasks, according to Todd Drane of Fagor Automation Corp. (Elk Grove Village, IL, and Mondragón, Spain). "Customers are looking for versatility with their CNC in today's market," notes Drane. "This includes the ability of the CNC to be equipped with a large variety of software solutions, such as milling, turning, and grinding, but also the ability to be equally comfortable working a two-axis application or a 28-axis, multiple-execution-channel application.
"Today, a flexible modular approach to your CNC must be taken," Drane adds. "Versatility also includes the ability to run third-party software on-line with the CNC, as well as the ability for OEM customization. The ability to create custom screens and processes directly on the CNC has become a primary buying consideration for many customers."
Among its latest offerings, Fagor now offers a multichannel 8070 Turning Control, a Windows XPbased system that offers an open architecture with the ability to integrate many software configurations. Designed for use with digital servosystems, high-speed motors, and linear as well as rotary high-accuracy feedback systems, machine servo performance is optimized with the 8070 T CNC model, Drane notes.
The CNC, which comes equipped with either a 12" or 15" high-resolution TFT LCD flat color screen, controls up to 28 axes, four spindles, and up to four execution channels, allowing the system to simultaneously handle multiple turning operations on multiaxis turning centers. "In addition, all of the movements that are not directly involved with the machining of the part, such as bar feeders, tailstocks, or cut-off tools, are all configured as independent axes," Drane says. "The movements associated with an independent axis are executed independently without interrupting the machining of the part, improving cycle times.
"With the Spindle Synchronization feature, a part may be machined in a single fixturing operation on a dual-spindle lathe. One side is machined in one of the spindles, and then the part is switched over to the other spindle to finish machining the other side. The switch is done by coupling both spindles in speed and synchronizing them in position; no home search is required."
A contouring control from Heidenhain Corp. (Schaumburg, IL), the TNC 320 control shown at IMTS 2006, offers machine tool operators an easy-to-use, full-function unit that can control five axes. With an analog drive interface, the TNC 320 easily integrates with existing drive systems on retrofit applications, and the control offers many of the best features of Heidenhain's flagship iTNC 530 control.
With a 1024-by-768-pixel 15" TFT color flat-panel display, the TNC 320 offers excellent graphics, according to Chris Weber, Heidenhain product manager, and it replaces the earlier 310 control. The new system comes with a USB connection for adding a full-size keyboard, Weber notes, which enables easier programming for users running G code on the system. Heidenhain offers its standard conversational programming as well.
A compact flash memory card stores the PLC program and commissioning information, and offers substantially more user memory for NC files, along with resistance to vibration and shock. The TNC 320 system is the first Heidenhain control based on its new NC Kernel software platform, and provides several benefits, including a new, powerful interface between PLC and NC that allows the elimination of redundant operations.
This article was first published in the February 2007 edition of Manufacturing Engineering magazine.