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Who’s Afraid of Five-Axis Machining?

Ed Sinkora
By Ed Sinkora Contributing Editor, SME Media
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Five-axis machining has gotten easy because modern controls automatically calculate the center of rotation of the part relative to the center of rotation of the machine, as on this Doosan DVF 5000.

It’s much easier than you think.

As industry veteran Andy McNamara would have it, “getting customers to move into five-axis machining is all about giving them confidence. Changing their notion that going to a five-axis automatically makes things much harder.” And according to McNamara, director of sales for Doosan Machine Tools America (Pine Brook, NJ), the most important tools in that effort are features within the control that make it simple to create, understand and prove out machining programs. Those features are now common among all high-end machine tool builders.

Errol Burrell, machining center product sales specialist, Okuma America Corp. (Charlotte, NC) hammered home the same point. “Years ago it was much more difficult to program five-axis machines. All the pivot points, all the centers of rotation, all the gauge lines, the tabletop, the exact tool length, all the specific attributes you could apply to a machine had to be plugged into your CAM system before you could even start to output any code. It was a lot of work, especially if it wasn’t just a simple right angle rotation on an A or B axis. Improvement in machine controls have eliminated all this.”

One major improvement is a feature Okuma calls “dynamic fixture offset,” with which the machine automatically calculates the center of rotation of the part relative to the center of rotation of the machine. As Burrell put it, “On a complex five-axis part with the proper fixture, all the operator has to do now is bolt the fixture down roughly near the center of the table, set the part on the fixture, indicate the part with the datum location, load the program, load his tools, and he’s ready to go. You can literally put the part anywhere you want on the fixture as long as the machine can reach all the X, Y and Z limits.”

But, as suggested earlier, this feature is not unique to Okuma and its OSP control. On FANUC controls, it’s called “tilted working plane indexing command.” Siemens, Heidenhain, and others have the same functionality. By the same token, CAD/CAM providers are pushed into creating post-processors that take advantage of this and similar features that make it easy to create and then verify five-axis machining programs (just as Doosan’s McNamara alluded to).

Plus, you often have several control options with a given machine tool. For example, Okuma’s Millac product range is available with either OSP or FANUC controls. Most Doosan machines ship with FANUC controls but the company also offers Heidenhain on some models and Siemens on others. The user can pick from a range of control and CAD/CAM combinations for five-axis machining.

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Touchscreen controls, like this Mazak Smooth X-1, eliminate intimidating masses of buttons, simplify menus, offer excellent graphics, and provide a friendly, tactile interface.

For Mazak Corp. (Florence, KY), it’s a Mitsubishi control with additional features that are proprietary to Mazak. Product Specialist Kenzie Roaden said the latest such version, SmoothX, makes big cycle time gains thanks to “the protocols in the control and streamlined hardware that eliminates the choking down of data as we process massive blocks of code.”

An unusual feature, which Mazak calls Smooth Machine Configurator, allows the end user to manipulate the gains on the servo drives, effectively enabling them to tune their own machine for a specific application. Mike Kerscher, product manager, described the interface as “three sliding bars on the control that you move back and forth with your finger to adjust sharpness, accuracy, and smoothness.”

Once you’ve achieved the desired tuning for a specific application, you can save that setting as an M code and reapply it later, even on another program. Hurco Cos.(Indianapolis) offers a similar technology, called SFQ (Surface Finish Quality) that can be adjusted in the control parameters and also customized on-the-fly in the part program or even for specific tools, according to Paul J. Gray, Ph.D., manager for path planning, front-end design, and R&D for Hurco.

McNamara added that high-end controls also include a feature that periodically adjusts the machine’s kinematics to compensate for the small changes in axis alignment that occur over time. And it’s especially important in five-axis machines that stack both linear and rotary axes. Doosan’s version is called Doosan Intelligent Kinematic Compensation. Besides making the necessary adjustments, it builds a table of all the changes so the owner can look for trends as the machine moves over time.

“You end up chasing tolerances without this kind of kinematic software,” explained McNamara. “Or you use old-school 3D indicators and it takes literally hours to set up a five-axis machine. We just bring a probe down, hit a button, walk away for 15 minutes and it’s done.”

Hurco’s approach uses a precision sphere and tool probe and can “easily be added to an automation system to run periodically throughout a production run,” said Gray.

McNamara also said that users now expect machine tool builders and control suppliers to understand their tricky applications and have solutions built into the software, and that’s exactly what’s happening. For example, he pointed to FANUC’s FAST (FANUC Advanced Surface Technology) functions, one of which is designed to improve turbine blade and blisk machining.

“Posture control” offers a good illustration of how a FAST feature takes advantage of a five-axis machine’s geometric flexibility without having to program each move in detail. This function automatically adjusts the position of the cutter as it approaches a point where it needs to transition from one plane to another, as opposed to waiting until it gets there. “Thus the surface finish doesn’t suffer as you get to the end point,” explained McNamara, “and it makes all the difference in the world on blade type features.”

Touchscreens Help

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This replica of the “Black Panther” mask was cut on a five-axis Hurco VMX60SRTi. It was on display at Hurco’s booth at IMTS last September.

As Okuma’s Burrell expressed it, “a skilled operator can do a lot of positional five-axis programming, and three plus two programming, at the machine. But it’s practically impossible to program simultaneous five-axis moves at the control.” So everyone agrees that most five-axis programming is appropriately done with CAD/CAM software on a separate PC, a subject beyond the scope of this article. That makes the wonderful new touch screens being fielded today relatively unimportant for five-axis work, but still worth a look.

For one thing, when you consider the prominence of smartphones and tablets in the daily lives of both millennials and the old codgers still haunting factory floors, it’s probably fair to say that touchscreens are now the dominant computer interface.

As a result, younger workers expect machine tools to have touch screens and older workers take to them as well. Hurco, which not coincidentally has long focused on making five-axis machining easy, introduced touch screens way back in the 1990s. One key benefit, as Gray explained, is the ability to “dynamically present the right information and menu selections at the right time and in the right place. This vastly simplifies operation and programming and dramatically reduces the operator learning curve.” Controls that used to have as many as 80 buttons are now much less intimidating.

Because today’s touch screens are all based on state-of-the-art PC technology, they also have the ability to display high-quality graphics, including 3D models. In fact, Gray said Hurco’s latest control uses 3D solid models to conversationally guide users to generate their part programs, though this presumably would not be the best use of machine time for a five-axis job.

Whether or not it’s used for programming, the ability to see 3D models of the machine, workpiece, and workholding on the screen is a great comfort for the operator. Hurco’s Mike Cope, product technical specialist, added that it’s also possible to add more softkeys to a touchscreen as needed, whereas “adding, changing or re-labeling hardkeys (physical buttons) on the control panel would be more difficult and more expensive. A touchscreen overhaul can be achieved with a software change.”

Finally, Doosan’s Manager of Applications Bob Appleton pointed out that PC technology also helps the operator by making it easy to include PDF instructions and send information back and forth to other parts of the company, including “things like productivity reports. Just the fact it’s a touch screen makes it more interactive.” That brings us to benefits and pitfalls of connected machining.

Connections, Remote Monitoring

According to Hurco’s Gray and others, MTConnect is now a widely adopted interface resulting in “a plethora of offerings for remote monitoring, which has led manufacturers to discover new insights into their present processes and to consider the viability of investing in technologies like five-axis machining to improve efficiency, quality, and throughput.”

Or as Burrell said, “Remote monitoring has shocked a lot of machine shop owners because it’s showed them how underutilized their spindles are.” He added that while he’s long been an evangelist for the greater efficiencies of five-axis machining, shop owners now come to the realization themselves when they see utilization of 30% on a three-axis vertical.

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Chevalier’s iMachine Communications System allows a user to review a machine’s alarm history, maintenance status, and overall equipment effectiveness from anywhere in the world, so he can anticipate potential issues and prevent stoppages.

With a remote monitoring system like the iMachine Communications System from Chevalier Machinery (Santa Fe Springs, CA), a user can review a machine’s alarm history, maintenance status, and overall equipment effectiveness (OEE) from anywhere in the world. Access to such performance data, said Vice President Johnson Lan, gives customers the power to anticipate potential issues and prevent stoppages.

McNamara of Doosan cautioned that while remote monitoring is helpful, the ability to quickly download, run or edit large files is important in five-axis machining. “We’ve seen recent examples of 20 and 60 MB files that, when handled the wrong way, were taking literally 20 minutes just to upload, an unacceptable amount of time. So connected machining is essential, but it needs to be implemented in a way that delivers the most important benefits first.”

Neil Desrosiers, software developer/application engineer for Mazak, echoed this thought, adding that Mazak’s solution distinguishes itself by providing a scalable approach to encrypting file transfers, thus protecting a company’s intellectual property. The Mazak system, called Smart Box, was developed in partnership with Cisco. “You can use the same system for 50 to 100 machines or push files to a Tier 1 supplier’s system without resorting to email or moving USB sticks around.”

However, there is a limit to how much data you can transfer quickly enough for some purposes. As Desrosiers explained, if your goal is to make “real-time adaptive feed rate adjustments or any real-time machine response to data, you need to do it with a dedicated CPU, dedicated RAM, and a high-frequency connection to the drives.”

In other words, it’s not something you can do remotely. But you can pre-process your high-frequency data locally and then report it to the cloud, or report individual events, or take low-frequency samples and send that data to the cloud.

As it stands now, there’s much more potential to gather and learn from the data that’s available in machine tools than is actually taking place. As Kerscher observed, “The big software giants are now recognizing that there are more computers in manufacturing facilities that there are in the business side of many companies. But a lot of the computer power on the manufacturing floor is not well connected at this point.”

Desrosiers described the situation as a software war to see what systems are best able to collect and analyze this data, with the likely winner being a company like Microsoft or Oracle, which are more sophisticated at this task than machine tool builders.

Another great advantage to connected machining is the availability of all the relevant files—whether it’s an NC program, DXF drawing, solid model or job instructions—right on the machine control. At the same time, said Cope, companies can “download available data from a specific file to whatever machine is open and ready to run that particular job. It also allows companies to store newly edited or
‘proven’ programs and CAD files in one place.”

By centralizing file management, he explained, you can eliminate the risk of an operator running an outdated program from a local file, which would result in scrap parts. “Connected machining can also provide access and communication to other types of technology, such as offline tool length presetters, pallet systems, and tool management systems.”

More Than Exchanging Parts

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As shown on this Okuma machine tool, probes can locate parts and automatically update offsets, plus perform in-process QC checks. And now it’s easy to program even complex probing cycles.

Much of what we’ve covered so far (automatic kinematic adjustments, connected machining, and remote monitoring) contributes to the ability to automate five-axis machining. And next to setting up a five-axis job, the most important consideration is keeping it running accurately with minimal manpower. The best part handling option, as Kerscher would have it, “has more to do with the size and weight of the part and the pace at which it needs to move, than whether it’s a five-axis part or a four- or three-axis part.” So let’s instead consider additional process control aids.

In a nutshell, “probing is huge,” said Burrell of Okuma. A probe can locate the part in the fixture, automatically update the offsets and clear the machine for take-off. And with zero point fixturing, you might even be able to eliminate this probing step because it is accurate within a few microns.

Burrell added that operators can also use a probe to make in-process measurements, like measuring a bore or a counterbore, or a depth, or a face relative to a bore position. What’s more, it’s now a breeze to program automated probing routines. Roaden said Mazak has a touch screen style graphical user interface (GUI) that makes it very easy to both set up automated probing routines and to apply the data. For example, it asks if you want to write the probe data to a file or offset a tool.

For more complex, in-process quality checks, Desrosiers said it’s now possible to incorporate a CMM in a cell that performs quality checks and pushes the data to scheduling software or QC system for approval before starting the next job. This is due in part to the wide adoption of the Quality Information Framework (QIF) standard, along with the MTConnect protocol.

In general, perhaps the ideal approach would be to combine a closed-loop feedback system for high-frequency data within a machining cell with a remote monitoring system that reported individual events like tool breakage or other causes of machine stoppage. That way, a shop could run lights-out with confidence.

“Prior to the onset of this technology shop owners might feel uneasy about running lights-out, choosing not to risk it,” said Cope. “This apprehension would cause them to miss out on the productivity of those extra hours in the workday.” And, Gray added, if things are running well, bi-directional communication gives you (or your ERP system) the ability to “command any series of different jobs to satisfy an order.” This makes even high-mix, low-volume production cost-effective.

Go For It

In any given fixturing situation, a five-axis machine can do more than a three-axis machine. That adds up to both more up-time and the ability to make more complex and profitable parts. And while there’s a still a role for a good engineer in CAD/CAM, it’s no longer difficult to operate the machine. Burrell’s bottom line? “You can hire practically anyone off the street to run the most complex machines we can build,” he said.

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