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Choosing the Right CNC

With the latest machine controls and CNC software, manufacturers can improve factory productivity


By Patrick Waurzyniak
Senior Editor 


With competition in manufacturing as keen as ever, today's manufacturers need the right tools to get the job done. Nowhere is this more imperative than when manufacturers choose what CNC hardware and software will control expensive machine tools that must operate at maximum metalcutting efficiency.

Today's controls gear and software offer much better performance and programming alternatives than the choices available just a few years ago. Optimal CNCs offer users a flexible system that can be easily programmed to handle parts on equipment ranging from simple three-axis mills to much more complex multi-axis machine tools.

New digital controls that offer users a flexible system for use in many applications are the latest incarnation of controls from Heidenhain Corp. (Schaumburg, IL), according to Chris Weber, Heidenhain product manager. "Customers are looking for a flexible control architecture that they can customize to suit their machine," he states. "So whether I'm using a simple three-axis machine, or I've got a 14-axis behemoth on which I want to do five-axis simultaneous machining, with 300 inputs and 300 outputs and two operator stations, and remote I/O located all over the machine, a lot of people are looking for a consistent hardware platform that they can customize."
The digital TNC 620 controls from Heidenhain offer users digital drives and conversational programming capabilities.

With the TNC 620 contouring controls, which come in two new digital versions, customers get many improvements including new drive systems, a new logic structure, and a new connection with the High-Speed Control Interface (HSCI), which Weber says has a proprietary digital communications capability similar to Ethernet. Available in two versions, the Manualplus 620 model for lathes is aimed at simple turning applications, and offers a new programming mode called smart. Turn for efficient programming. The other TNC 620 model offers a new compact contouring CNC with digital drive control for milling applications.

"The Manualplus is strictly turning, and it's meant for a shop-floor operated/programmed machine, and medium production runs," Weber says. "It's not a high-production, high-capacity lathe control. It's meant to be more user-friendly, interactive, and shop-floor programmable. There are some nice simple conversational programming features built into the control. If I was going to do two-axis plus a spindle plus a live tool, this would be the control of choice."

 With turnkey software, Bosch Rexroth offers users custom applications like this high-dynamic nibbling and punching operation on Trumpf systems.

The system is suitable for upgrading a manual machine to CNC control, he adds. "You have a lot of manual machines still being sold around the world," notes Weber. "With this control, I can still run the machine completely manually, so I equip it with a couple of electronic handwheels, and I rotate them like I'm controlling X and Z in a normal fashion on a manual machine."

High-performance CNC systems from Bosch Rexroth Corp. (Hoffman Estates, IL) offer users a wide range of capabilities for many machining applications. The company's IndraMotion MTX compact is the latest in its line of controls that now includes a space-saving compact model, as well as standard and high-performance versions.

The Bosch MTX compact CNC includes an Intel-based 500-MHz CPU in a compact format designed for a cabinet mount. "We have MTX standard and performance, which are basically plug-in boards that go into a PC, and that's how we do most high-end CNCs," notes Karl Rapp, branch manager, Machine Tool & Automation, Bosch Rexroth Corp. — Electric Drives and Controls (Hoffman Estates, IL). "We've expanded both hardware ranges, one is the MTX compact, which we've always sold for eight-axis, two channels, etc. We can do anything from basic machines up to eight-axis, and large systems with up to 64-axis over 12 channels.

"The difference in our control versus some of our competitors is that this MTX system is a multichannel control. That means you can run more than two CNC channels, and one channel can be doing milling and the other one could be turning. In some competing units, you buy a milling control or a turning control, so from our philosophy, we always could do all machining technologies within a channel and one control."

Demand for CNC systems remains strong from customers that require the latest technologies, says Rapp, who notes that the Chinese market continues to add metalcutting equipment for its booming business. "We work with quite a few large OEMs in China. They mainly produce for the domestic market, but in last five years they are really, really pushing to have the absolute latest technology in their machine tools, because they want to expand these machine tools, first of all, to make the same quality machine tools for the Chinese market."

In North America, the traditional machine tool market seems to be rebounding a bit, he adds. "At the moment, the market has recovered somewhat, compared to 2000," Rapp says. "The market that really never saw any recession is the waterjet/flame-cutting type systems, and now that's driven on the metals side through the oil boom. With the higher oil prices, it seems there is quite a lot of demand for flame-cutting machines, where they are re-doing the infrastructure, and to build new systems to recover oil in ways that were formerly inefficient."

With Bosch's MTX hardware line, the company will be increasing computing power on the low end to 1-GHz CPUs. "Starting with our next release in June, our MTX compact is functionally no longer restricted, so even in that small form factor, we can do up to 64-axis control," Rapp adds. Other CNCs aimed at applications in large rotary transfer machines will handle even more axes with more-powerful processors.

 With updated SinuTrain CNC training system and ShopMill and ShopTurn applications, Siemens Sinumerik users prove out part programs before heading to the shop floor.

"For example, for Mikron in Europe we make some machines that have up to 144 axes and 24 to 30 stations," Rapp says. "There are multiple networked controllers per machine, and from a motion standpoint, we can do 64 axes at about 6-msec update per MTX. That's not so much the limit on these machines, but we will further improve machine cycle time with an even faster PLC in our controllers to keep the PLC scan time low."

Software development on Bosch Rexroth's CNC applications include .NET and XML-based packages for turnkey applications, such as its IndraMotion for Handling solutions. "Here in the US, because our complete software platform for HMI for CNC is all .NET-based and XML," Rapp says, "we have created a solution for the 2-D cutting market, flame cutting, laser cutting, and waterjet cutting.

"It's basically having nesting software embedded," he adds, "and because it's a .NET platform, we offer a very easy automation interface into which the nesting software can be integrated. We use this currently to provide a totally open solution for OEMs in that market, because this particular market of flame-cutting and waterjet-cutting was always restricted in the past with regard to CNC functionality, due to the controller types they used. And with MTX, we offer the complete range of axis count, processing power, different technology combinations of milling, drilling, tapping, handling, and plasma/flame, waterjet, and laser cutting."

The Bosch Rexroth solution for oxy fuel, waterjet, and laser will be available soon, Rapp notes, and will be called IndraMotion for Shape Cutting. "The key functionality that we needed for that market, specifically the flame-cutting market, is named function, Retrace," Rapp says. "Retrace means that if you move along the path forward in your cutting direction and if something happens to your cutting tool, meaning, for example, the garnet is running out on the waterjet or your gas goes off, then the CNC still moves and there's a section of the part that's not cut. If you have a complicated shape on your sheetmetal, it's very difficult to move backwards with conventional jogging methods.

"The retrace function allows you to simply move a joystick or a reverse button, then the CNC moves along its actual path backwards, until you as the operator decide, 'OK, this is where it's cut,' then you can jog off the path to the scrap area, restart the machine, burn a hole in a scrap area, and go back to the workpiece path and continue cutting without damaging the workpieces."

High-speed, high-precision machining has been gaining momentum among users of the high-end 30 Series controls from GE Fanuc Intelligent Platforms (Charlottesville, VA), according to Paul Webster, GE Fanuc CNC product manager. "It's always about productivity," Webster says. "That's always the big thing—trying to figure out how to get more out of the same machine, or buy one machine that can do what two machines could do in the past. That's always a huge trend in the industry. So compound machines are being more common, where you've got a mill side and a lathe side, where you've got multiple part programs running."

High-performing CNCs to handle mill-turns and five-axis machining remain in high demand, Webster says. "Those types of applications, especially five-axis machining with the amount of aerospace going on right now, is more common than ever," he states, "so those types of applications are where you need the horsepower of the 30 Series controls. Your standard little knee mill probably doesn't need it.

"We get people requesting high-speed machining on these small three-axis machines all the time, and they want some ungodly amount of look-ahead. They want 500 blocks of look-ahead, and 1-msec block processing time," Webster notes. "They'll never be able to use it. It's just a waste of money. But on a five-axis machine, that's where you need it, and the 30 Series will do 0.4 msec and it'll do 1000-block look-ahead, and figure out its path in advance."

With its high-end 30 Series, GE Fanuc improved processing significantly over previous-generation CNCs, including the 16, 18 and 21 Series controls, that used Intel-based CPUs. The GE Fanuc 30 Series incorporated IBM's RISC-based PowerPC chip. "It's very impressive hardware for a CNC application," Webster says of the PowerPC CPU. "Most PC-based stuff is Intel, but doing spreadsheets is a little different than motion control. Our past lineup, the 16-18-21, was Intel-based; that gave us low power consumption, good reliability, and good availability. But it doesn't have the horsepower.

"We also had the Series 15 control that used the Motorola G series—great processor, huge amount of power—but it was a power-hungry beast. That system used 200-V input and had a lot more heat production, which affects reliability and power consumption. So the 15 Series, while it's still available, isn't really going forward. Fanuc took the software and hardware more or less in a combined 15-16, created the 30 Series based on the PowerPC. That gives them the advantage of the low power consumption and the high performance."

Using the PowerPC-based CNCs, GE Fanuc's current generation offers much faster performance, Webster notes. "It gives us a lot faster performance built-in. We're allowed to do more simultaneous axis, more processes at one time. When we got into advanced machining on the 16-18-21 type series on the Intel platform, we had to add a separate RISC board. We don't have to do that kind of thing any more, it's all able to be done on one CPU."

With the higher-performing CPUs, GE Fanuc's 30, 31, and 32 Series controls all are capable of nanometer interpolation. "It does nanomachining right out of the box," Webster says. "It does all its thinking at the nanometer level so everything's smarter. Even if you're not programming to it, interpolating to a nanometer has a lot of advantages. Whether you program to it or not, the controller is doing its background math at that level, which has advantages of rounding. Plus, it's easier to improve your machining when you're inherently at that level."

Faster communications also boosts performance on the 30 Series, adds Webster. "The communication between the CNC and the servo card is done more quickly, and then from the servo card to the amplifier system communication is quicker, so our loops are faster," he says, noting the 30 Series is capable of 32-servoaxis, eight-spindle axis performance.

Software and CNC training enhancements help users of Siemens' Sinumerik controls operate at higher efficiencies. At WESTEC, Siemens showed its updated ShopMill and ShopTurn software packages for the Sinumerik line of controls, as well as its newly updated SinuTrain CNC training package, available at discounted pricing through September 30. Siemens' new SinuTrain system offers users the ability to learn the Sinumerik CNC control and prove out part programs on a PC, notes Randy Pearson, manager, dealer and end-user support, Siemens Energy & Automation Inc., Machine Tool Business Unit (Elk Grove Village, IL).

"SinuTrain is geared for training in a classroom or technical-school type of environment, but now people are using it for in-house training," Pearson notes. "They buy one license to use it in-house, and they also use it to debug and program parts before they go to the machine, because it runs the same way as the machine. So they'll program their parts, run the program through the SinuTrain, and get a 90% confidence factor that it will do what they want it to do, then they put the program in the machine and run. They're saving time and money by debugging on a PC as opposed to debugging on the machine."

Users can also run ShopMill or ShopTurn on the CNC training system, which Pearson notes is the exact same machine interface running on the PC. "It's set up to look and run like your machine, so we can take their CAD/CAM program, load it in and test it, especially on a mold part or an aerospace part. Some of our aerospace companies in California are using it, and before they put the part program on the machine they run it through the SinuTrain, verify that everything will work, and then they load it into a machine."

The training system enables machine operators to effectively run programs for a Siemens 802 or an 840D control before going to the shop floor. "It looks, feels, and runs like the control," Pearson says, "and it'll prove out your parts before they even get to the machines, so you don't have an hourly burn rate for the operator on the machine to test the part. And what you program there you could conceivably transfer right to your machine. As long as the machine has a Siemens control, it can run the part program."High-performance PowerPC-based 30 Series controls from GE Fanuc target high-speed, high-precision applications.

Ease and efficiencies in programming are keys to improving plant productivity. "Everything is tied to productivity," says Wayne Nelson, manager, East Coast CNC Operations Fagor Automation Corp. (Elk Grove Village, IL, and Mondragón, Spain), noting that Fagor offers dependable, flexible CNCs.

"The latest trends are for extremely functional conversational programming and very complex high-speed machining applications," Nelson says. "It would appear that operators and machine shops need all the help they can get to remain competitive. Whether you're making a small batch of parts or millions, you need to maximize the capability of the system and consistently bring parts to QC that can be shipped and accepted. Many dealers in CNC systems are not taking the time to fully learn the nuances of each system and its capability, so the control practically has to be self-explanatory and extremely powerful."

With Fagor's conversational programming system, Nelson says the whole part should be programmable in conversational programming alone. "No G-code back-up programming should be necessary," he says. "Fagor is providing all the simple machining cycles in conversational mode, but also provides a full G-code capability with every detail."

For high-speed machining, the company offers its Fagor 8070 series of controls. "In high-speed machining, the system must stage [buffer] all the servo activity so the relation between the cutter and material does not change," Nelson states. "At speeds in excess of 3000 ipm [76 m/min], the control and servos have to be mated perfectly to make this happen. The SERCOS [SErial Realtime COmmunication System] interface available in Fagor Automation controls makes this achievable.

"The latest batch of cycles includes controls that offer 28 axes and four spindles. Multiple-channel units will allow you to bring together up to four machines in production cells or run up to four separated machines from one control. Software that will combine the functionality of both a lathe and a mill in one machine is available, and we also now offer absolute feedback in our drives and our linear scales."


This article was first published in the April 2008 edition of Manufacturing Engineering magazine.   

Published Date : 4/1/2008

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