Manufacturing complex parts for aerospace and defense programs requires the consistency highquality and precision that Smiths Machine achieves with Siemens CNC

Manufacturing complex parts for aerospace and defense programs requires the consistency, high-quality, and precision that Smiths Machine achieves with Siemens CNC.

New CNC Platform Sets Stage for Machine Shop’s New Direction

Smiths Machine adopts Siemens programming as the starting point for a strategy that has guided five years of growth and expansion Quality and precision, not throughput More complex … more competitive Teaching, learning as core values NX, as in next

Family-owned machine shops are not unusual but Smiths Machine, a second-generation, business with two state-of-the-art operations in Tuscaloosa, Ala., is carrying on more than a legacy. The CNC milling, turning, and grinding business has redefined itself in recent years,  finding a formula for growth that has resulted in adding 70 workers since 2009. That’s a 300% increase, mostly during a time when many machine shops (indeed, many manufacturers) were struggling to break even.

Ahead of the recession, Smiths Machine was operating like many other machine shops doing at that time, coasting along with a solid business in automotive parts production. The financial crisis hit the automotive sector particularly hard, and the bankruptcies of General Motors and Chrysler Corp., as well as many of their top-tier suppliers left many machine shops vulnerable to volume-based supply from overseas competition. A once well-oiled machine tool business model suddenly seemed unstable.

The idea of moving the Smiths Machine business into a new manufacturing sector seemed uncertain, however necessary. Defense and aerospace part manufacturing require a different business approach than auto parts production, according to Tim Smith, vice president of Smiths Machine.

Smiths Machine’s growth strategy started with its investment in a CNC platform: The steady progression of a stable machine/control platform has allowed the manufacturer to expand its workforce while building on established knowledge, rather than having to learn new and different versions every few years.

“It is specialized work that requires special approvals, log-down processes and complicated procedures,” Smith said. “The complexity is challenging. And it all starts with a different way of thinking, more of an engineering approach than a production approach.”

Smith said his company needed to build a new business model and the operations to support it.  Defense and aerospace machining is characterized by small lot counts, generally lower margins, and a very low tolerance for errors. Scrap rates thought to be nominal in the past would now be out of the question.

“You can’t make a $6,000 part and have a 30% scrap rate, or even a 10% scrap rate,” explained Smith. “The emphasis is not on throughput, but on the high quality, highly precise manufacturing of very complex parts.”

Based on these three, inseparable machining requirements — quality, precision, and complexity — Smiths Machine set out to reach its greater potential in the machine tool market, not as a production machine shop but as company focused on complex part manufacturing. Having achieved some early success in this new direction, the way forward for the company soon could be summed up more simply:

“The more complex the part, the more competitive we are,” Smith stated.

To protect and grow this competitive advantage, the organization’s leaders knew that internal processes and technology needed to match up with the particular requirements of the defense and aerospace industries. Major investments in large, complex, five-axis machines would need to be enhanced by equally complex control capabilities. Smith recounted how a decision made previously by the company would have a profound effect on the changing profile.

Synergistic Approach to Milling, Turning

Traditionally a milling and turning company, Smiths Machine first teamed up with DMG and Siemens in 2000 to establish a single machine tool platform. This brought about a synergistic approach to complex milling and turning: an advantage that took on greater significance when the company decided a few years later to focus on the defense and aerospace markets.

“Siemens controls were available on DMG milling and turning machines, and that was a natural fit for us,” Smith recalled. The DMG/Siemens platform has enabled Smiths Machine to establish and maintain a high level of operational proficiency. The central advantage here, Smith said, has been the ability to invest in, train, and keep his people moving forward with a stable technology platform.

Graphics-guided Sinumerik Operate HMI from Siemens made it easy to adopt Sinumerik 840D sl CNC, a control that is known for its powerfully complex capabilities. Across the company, visually guided teaching and learning methods have promoted rapid learning and operational proficiency.

“The technology and the people using it are the backbone of our organization,” Smith asserted. “Even with 25 machines, we can share knowledge between the milling and the turning machines. The common control is a Siemens Sinumerik 840D sl. Our technology purchases are based on where we want to be in ten years, not on a workforce that is fractionally trained and a platform that can rapidly deteriorate due to a change in market condition or a change in employment condition.”

Smith said an example of this single-platform advantage is the control’s similarity across milling and turning operations. “All controls are customized to a certain extent,” Smith acknowledges. “But unlike Siemens, many other control series are individually customized so that the keyboard layout will be different from machine to machine. The Sinumerik 840D sl CNC is consistent. So when you train your operators, you can say, here’s the jog button, here’s the axes button, here’s your alarm button and your offset button. And this level of consistency extends to a graphical interface that really complements how we teach and learn.”

Teaching and learning are core values for an organization that uses visual techniques to promote education, efficient information sharing, and quality control. “We are a very visual company,” Smith said. “We use a lot of colors and we buy a lot of printer toner. Our parts inventory uses color-coded tags and the same is true across our production. We use yellows and blues and reds for consistent instruction. And the Siemens 840D sl control uses the same approach. You are guided visually for such things as axis direction, approach point, final depth and other variables inside a cycle. And this is true from control to control, for milling and turning.”

Smith said visually guided information flow is characteristic of today’s complex range of next-generation electronic communications, because this speeds understanding and information sharing. Whether for a smart phone or a CNC, graphically guided interfaces enable rapid learning and proficiency, a fact that has been well leveraged by the 840D control interface design.

New Angles on Programming

Gerhard Hetzler, engineering manager at Smiths Machine, has first-hand experience with the company’s single-platform approach, and the continuity it provides manufacturing functions like post, machine simulation, NC code, and control functionality.

While the Siemens 840D sl control has evolved in significant ways over the years, Hetzler said these changes have served only to accelerate the performance of the programmers and operators, rather than impede them with new and different procedures. The control platform also gives Smiths Machine the freedom to create custom cycles that can be copied and shared from control-to-control, and so machine-to-machine.

“I’ll give you an example,” said Hetzler. “To catch occasional entry errors on the tool management side, we created a cycle that checks the length of the tool and within a specific tolerance. So within in a matter of milliseconds, the control compares that value to what was entered in the tool management side, and if the tolerance is exceeded by 2mm, the control immediately stops the machine.”

The Cycle 800 function within Siemens NX supports the programming for 2-1/2 axis and 3D milling through the rotation of all X-Y-Z planes, while maintaining a zero offset. Functions include automatic shifting of zero offset, tool length, and radius compensation in rotated planes. Compensation of machine geometry is available too, and all machining cycles can be used.

Hetzler said another advantage resulting out of the DMG and Siemens relationship is the continued simplification of complex cutting operations, especially in the area of angular milling heads.

“Siemens has come a very long way to improve the cycles and support related to milling heads,” Hetzler said. “Aerospace requires a lot more use of angular milling: Even a five-axis approach can’t do it; you need an angular milling head. I would put this on the top of my list of the advantages DMG and Siemens have developed. And this relates to another important development, Siemens NX.”

Siemens NX software integrates CAD, CAE and CAM, encompassing all areas of tooling, machining, and quality inspection, to accelerate parts production. NX has become integral to Smiths Machine’s CNC platform because it supports part planning through manufacturing, with the prevention of errors and related costs.

“Our ability to develop all of our own post-processors in house is supported by Siemens NX,” Hetzler explained. “We set up our angular milling heads in NX, so we can post the G-code before we even send it out to the machine.”

An early introduction to the effects of NX came when the organization discovered it needed to write code to produce an especially challenging aerospace landing gear. The code took six-weeks to program manually — before the programmers learned that they could do the same task using NX in just nine days.

Siemens NX integrates CAD, CAE and CAM, encompassing tooling, machining, and quality inspection functions to accelerate part production.

“Siemens knows five-axis machining and NX is a Siemens product that leverages five-axis,” Hetzler said. “As an example, we can do three-plus-two axes work in NX. There is a cycle for that called Cycle 800. So when NX outputs the NC code, the machine then also understands it. Other control brands will have a cycle that can be made to work, but they are a lot more problematic. We are talking about managing the change of plane, a concept that has been around for a long time and was always problematic to do. Now, Cycle 800 in NX does it all for you.”

Hetzler said Cycle 800 makes programming the change of plane easier, faster, and with higher accuracy than traditionally calculated methods. “We would normally round off after the third or fourth decimal,” he recalled. “Now, the control calculates to nine decimals. When you start talking in terms of microns, especially in the aerospace industry, it makes a huge difference. And, this difference has been fully implemented by DMG. They have invested a lot of time and money to make sure from their side that Siemens NX and Cycle 800 work 100% of the time.”

John Meyer is the manager of marketing communications for Siemens Industry Inc. Contact him by email, or visit Siemens Industry online.

TAGS: CAD and CAM
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