CAM technology keeps pace with aerospace manufacturing challenges.

Advances in materials and engine efficiency have created clear benefits for replacing older aircraft. Demand is so significant that machine tool makers are challenged to supply equipment quickly enough to aircraft manufacturers and their suppliers. Increasing the number of spindles can be difficult and expensive, so some producers are reacting by increasing productivity of tooling, workholding, and CAM software solutions. Enhancements to support technologies can increase productivity of existing equipment, reducing the need for new machines.

Many CAM systems focus on processes such as 5-axis milling, mill-turn, wire EDM, or mold-and-die applications. So, ideal CAM software for aerospace must excel at high material removal of aluminum from structural components and work well with high-precision temperature-resistant titanium or nickel-based superalloy compressors and turbines.

High-performance roughing brings aluminum blocks or plates to near-net shape, where 90% or more of the block weight may be removed. This is important in typical 3-axis structural components and crucial in 5-axis components. Many CAM programs have a high-performance roughing module using trochoidal techniques. Open Mind’s hyperMILL MAXX Machining roughing module has been extended to apply to 5-axis roughing. For shaped structural components (wing segments or doors), 5-axis roughing benefits subsequent machining processes.

Standard structural part surfaces are machined with swarf milling, with the side of the cutter aligned to the side of the part, enabling good performance but limited to 50mm high wall surfaces. For larger wall surfaces, swarf milling may cause the cutter or wall surface to vibrate. Multiple steps with overlap and inconsistent deflection patterns are also possible. The next best option is point milling in many passes by using the tip of a ball-nose end mill with a small step-over. Unfortunately, point milling increases cutting time dramatically.

Open Mind’s hyperMILL MAXX Machining finishing uses a conical barrel cutter (also known as circle segment or arc segment end mill) for a barrel contact radius of 1,000mm or more, producing a wider stepdown 10x to 15x that of a ball-nose end mill. This can reduce cutting time 90% or more. The conical barrel cutter has the large barrel radius ground on a tapered feature, compared to a traditional barrel cutter where the large radius blends to be tangent to the cutter shank.

The taper allows the cutter axis to be pulled away from the surface being cut. The result is a shorter, stiffer cutter without interference from the cutter holder. Though the tangent barrel cutter provides some benefit, the conical barrel cutter enables a larger barrel radius to allow shorter cutters without interference from the cutter holder.

Conical barrel cutters exhibit long life and consistent machining performance. In addition, the ball end on the tip of the conical barrel cutter can be used to clean fillets and blend surfaces using the same cutter.

Single blades for a turbine engine can be machined from rectangular block, cylindrical stock, or near-net forgings. Roughing is a critical task to control costs and to set up for finishing operations. Due to various starting stock shapes and irregular finishing shapes, stock tracking is essential during roughing to avoid wasteful air cuts. As blades can be twisted, multiple cutting orientations should be used during roughing to leave minimal stock for finishing.

Single-blade finishing is typically performed with ball-nose end mills, especially on twisted surfaces and near attachment platforms. Open areas of the blade surface are often cut with a tilted bull-nose cutter. This cutting style gives a large effective radius of curvature and can produce a fine surface finish with fewer passes compared to a ball-nose end mill. Recent developments also include the applications of high-angle conical barrel cutters to single blade components.

Finishing multi-blade components – a turbine bladed disk (blisk) – brings additional challenges due to tight blade spacing and requirements for high aspect-ratio cutters. CAM collision detection and avoidance techniques can find a solution in the close spacing between blades.

Small cutter radii imposed by blade spacing, fillet geometry, and fine surface finish specifications may require hundreds of passes around the blade using a ball-nose end mill. Applying long path lengths against hard metals is time consuming and leads to cutter wear and concerns for manufacturing consistency. Some engine manufacturers change a cutter for each subsequent blade surface to assure consistency of wear and reduce imbalance of the machined part.

Twisted multi-blade surfaces typically don’t allow swarf milling. Conical barrel cutter solutions are also being applied to achieve cycle time and quality improvements. The larger stepover reduces overall path length and tool wear compared to ball-nose end mills.

Single-blade and multi-blade components can be classified with feature-based and family-of-parts (macro) programming. Repeated geometry selections of curves and surfaces are more complex than typical holes and pockets but can be represented by feature definitions. Using best practices for materials and tooling, including feed rate and spindle speed, holders, stepdown, and stepover, can be useful when programming for multiple parts. A comprehensive family-of-parts strategy reduces the programming effort across many parts while achieving high productivity.

CAM has a large influence on machine tool performance, so users can benefit by selecting the proper software for the application. The most advantageous CAM software is continually evolving with each new version release to offer enhancements and innovations that keep up with aerospace manufacturing requirements. 

About the author: Alan Levine is managing director of Open Mind Technologies USA Inc. He can be reached at alan.levine@openmind-tech.com.

Optimized flash technology can ensure host architecture compatibility while meeting application workload requirements.

Technologies based on the Industrial Internet of Things (IIoT) are expanding exponentially, and Industry 4.0 has sparked a wave of transformation that is quickly changing the way aerospace manufacturers operate.

One challenge – managing massive amounts of data produced by aerospace IIoT systems. A jet can generate hundreds of gigabytes of data per minute. And data storage devices must function in extreme environments. For IIoT applications to capture, store, analyze, and share information, they require versatile storage devices that can withstand high and low temperatures, humidity, and vibration.

The rugged durability of industrial flash storage devices provides a solution for applications such as helicopter black box recordings, jet mission data collection, unmanned aircraft base station and flight data recording, and in-flight entertainment and WiFi services.

Industrial flash storage devices must be able to handle massive amounts of data and operate from -40°C to 85°C for prolonged time periods without fail. Ruggedized devices use single layer cell not-and (SLC NAND) architecture, since it’s more reliable for IIoT purposes.

Unfortunately, many aerospace manufacturers perceive flash memory as a commodity, and purchase commercial off-the-shelf (COTS) parts that meet type, memory capacity, and form factor specifications. They may overlook considerations such as workload (frequency of reading/writing large amounts of data), power management (dirty power, power cycling, power failure), and environmental conditions (temperature, vibration). These factors can corrupt data and cause other errors, reducing storage reliability and lifespan.

“Many aerospace manufacturers purchase flash storage devices over the Internet only to discover at the launch of the product there were unexpected issues due to inaccurate assumptions about the environment and workload requirements,” says Tony Diaz, product manager for Delkin Devices, a supplier of non-volatile flash solid state drives (SSD), cards, and modules.

In aerospace, this can lead to unexpected failure of mission-critical data and compromise safety features. Given the vital role of storing mission-critical data, Diaz says most industrial flash storage devices require some customization to meet real-world workload requirements.

All flash storage has a finite life, depending on how well it’s managed and workload requirements. To optimize and extend the life of a flash storage device, carefully consider how data is written to it.

New data cannot be saved to flash until old data is erased, and only a finite number of programming/erasing cycles can be performed before wear renders flash unreliable. Some flash media are not used evenly, further reducing a device’s life.

Options to extend flash device life include reducing unnecessary file copying or data downloading, consolidating writes, wear-leveling techniques, and selecting whether data are written sequentially or randomly.

“If an aerospace manufacturer misjudges or misunderstands the workload requirements, there are implications for the storage,” Diaz explains. “It could be as simple as unexplained errors in the field, or it could be a situation where they are wearing out the flash memory much faster than they realize.”

When customizing flash storage, consider mechanical ruggedness. Ask, is the application subjected to unusual amounts of vibration? Does the typical operating environment exceed standard industrial storage parameters?

Although designed to be rugged, each industrial flash storage application has different operating requirements. Customizing mechanical ruggedness can alleviate concerns about failures associated with operating conditions.

To ensure a storage device will work as expected, partner with a manufacturer who offers testing reliability services. At its manufacturing facility in San Diego, California, Delkin Devices offers design verification testing, ongoing reliability testing, and accelerated lift testing to simulate long-term operating conditions.

Losing power during a write operation can cause data loss if data aren’t saved completely. Even a small amount of data loss during a power failure can cause significant ongoing problems, including fatal corruption of the entire system. It can also cause inefficient use of memory capacity, which can dramatically shorten the embedded flash storage lifespan.

Reducing external sources of power loss mitigates the risk of power fails. However, power failures can still occur, so internal protections are essential for reducing data loss risk. For flash memory systems that handle critical data, that means built-in power loss controls, including systems for monitoring power supply and the ability to recover data after losing power during a write operation.

Dirty power from outages, brownouts, surges, and power spikes is another concern. When direct current (DC) dips below the required threshold, errors can occur in equipment critical to airplane or spacecraft operation.

How a manufacturer sources parts, engages suppliers, and ensures that the sourced parts will be available throughout the product life cycle are important issues.

Bills of materials (BOM) of commercial-grade flash storage are often updated without warning. Although this helps consumer manufacturers maximize functionality while minimizing price, aerospace manufacturers need consistency and reliability.

Diaz says manufacturers can achieve a higher standard when component parts are controlled and configuration locked.

“Once qualified, the flash, controller, and firmware will not change as long as the part number is active. If anything needs to be changed, changing the part number essentially guarantees that the customer is notified and the BOM is updated,” Diaz explains.

COTS flash storage may have the right specs and cost less than a customized part from a supplier, but there are always hidden costs and risks.

Diaz says manufacturers should engage a supplier from the beginning of the design process to ensure they get what they need for the product’s entire life cycle.

“Aerospace manufacturers may not spend much time considering flash storage,” Diaz adds. “But given the critical nature of data in today’s devices, there is too much risk to take industrial flash for granted.”

How compliance and collaboration will electrify aircraft.

Power conversion is a uniquely challenging feat when designing converters for critical applications such as engine or flight control systems. Since manufacturers don’t routinely redesign these complex systems, most of today’s commercial aircraft will have a power supply within the engine control system that was designed 25 years ago – proven and performing like clockwork.

But the if it ain’t broke, don’t fix it line of thinking is poised to change if aerospace original equipment manufacturers (OEMs) plan to capitalize on newer technology to drive higher efficiency. Where an old converter design might be 70%-to-75% efficient, a newly engineered version should deliver more than 90% performance efficiency while ensuring safety compliance. To develop smarter technologies for today, as well as breakthroughs on electrified aircraft of tomorrow, progress and performance must break free of resistance to change.

With production dominated by a few large industry players, existing power converters – for example, auto-transformer rectifier units (ATRUs) – are based on decades-old technology and are commonly non-compliant to the latest airframe harmonic requirements. Used to connect electronic equipment to airframe power, the non-compliant ATRU typically must be granted a performance waiver from the OEM; these waivers essentially acknowledge small outages in performance. ATRUs are safe, but failure to meet standards results in greater heating effects onboard the aircraft and greater limitations on the systems and features that can be engineered into the airframe. As aircraft change and advance technologically, these limitations won’t remain acceptable. For optimal performance, as well as competitive value, there’s a new push for ATRU technology that is fully compliant to the harmonic requirements of advanced aircraft.

Meanwhile, since ATRUs are so integral to electronic aircraft systems they have become key drivers of revenue for manufacturers – even if the manufacturer lacks deep understanding of how their own devices are engineered. Because these firms do not typically have onsite expertise to enable power conversion design at their facilities, a new market is emerging for products that are fully compliant and implement safety-critical features from the earliest design phase.

Systems must be safe under all circumstances, yet just because a system works doesn’t mean it’s fully compliant to safety standards. Innovators are tackling this challenge by developing families of robust, safety-critical converters to power the brains of aircraft systems such as engine controls or fly-by-wire control systems. To ensure optimum power generation, energy from the generator must be drawn sinusoidally, reducing harmonics and the negative effect of heat on wiring. However, this design is complicated, so expertise must focus on the safety-critical aspects of performance. Consider a simple input filter for a power converter. There are quirks and oddities around this rudimentary circuit that may not be solved even if the paired voltage converters seem to perform. Complex systems have potential for peculiarities – such as unusual voltage on a single rail – that require specific design talent to avoid system failure.

Compliance and safety lay the foundation of smart design and enable performance excellence, including improvements necessary to drive engineering breakthroughs in modern aircraft design. For example, meeting the input-current harmonic specification ensures safety and protects the interests of aircraft manufacturers, but also positions the industry to unlock the potential of more-electric aircraft (MEA). This is a critical on-ramp to the future of aircraft design, because as planes become more electrified, more electrical systems will be added. All-electric aircraft will require even tighter, lower harmonics on systems’ input current, and manufacturers will face an evolving goal of drawing increasing levels of power from the generators in use.

In January 2020, TT Electronics acquired the Covina, California-based business unit from Excelitas Technologies Corp, of Waltham, Massachusetts that designs and manufactures power electronics for aerospace and defense (A&D) markets.

The acquisition enhances TT’s U.S. presence in A&D power electronics, providing access to growth programs with sole-source positions with several major U.S. defense primes.

In this landscape, firms with a global footprint and deep expertise also play a role in pushing forward overall industry innovation and technology breakthroughs – not to mention helping aerospace leaders sustain relevance to the engineered systems of tomorrow. By recruiting talent from system manufacturing and design engineering, innovators are creating teams experienced in developing power electronics systems. This creates a significant industry shift, filling a gap in companies that can provide broad spectrum solutions, allowing industry players to redirect design resources to the next level of aircraft integration.

Auto-transformer rectifier units (ATRUs) convert the AC power produced by generators into DC power. There might be hundreds of ATRUs onboard a single aircraft, handling a spectrum of power needs, spanning from 1kW to 250kW. These simple and reliable devices deliver quality power using a multi-phase transformer, power diodes, and electromagnetic interference (EMI) filters.

However, legacy ATRUs introduce unwanted harmonics into a system instead of delivering the desired smooth sinewave current pulled from a sinewave voltage. This fails the acceptable level of harmonics defined by the comprehensive DO-160X industry specification, requiring aircraft manufacturers to grant waivers for any ATRU design that falls out of spec. While a waiver doesn’t mean an unsafe device, it acknowledges a less efficient device is being used that produces more heat, limiting the number and type of electrified systems that can be added to the aircraft.

Compliance changes this landscape: Qualified to DO-160 provides a way for manufacturers to fully capitalize on the power potential of their designs in the same or even smaller ATRU footprint. It’s a big win in advanced aircraft systems relying on a fixed amount of power being generated and transmitted – allowing a competitive difference.

Compliance waivers are on their way out, creating a virtuous cycle of innovation that’s critical to improve safety compliance and develop breakthroughs to fuel the growth of electrified aircraft. The industry should recognize this sea change and develop greater awareness of the challenges, possibilities, options, and leadership opportunities driven by excellence in power conversion.

About the author: Julian Thomas is engineering director, power and hybrid business unit, TT Electronics. Connect with him at julian.thomas@ttelectronics.com or LinkedIn.

Less can be more when it comes to flexibility and speed.

In precision aerospace grinding, the size of components matters. For smaller parts, less can be more in machine size requirements, features, and especially flexibility and speed.

Machines developed to grind small blades, vanes, and shrouds increase flexibility, economy, and productivity. And adding milling and drilling multitasking to a compact, 5-axis grinding machine multiplies production flow benefits.

Maximum efficiency results when manufacturers process parts on appropriately sized and equipped machines, so United Grinding North America offers several configurations of Mägerle 5-axis multitasking grinding machines to process aerospace components and other high- value parts.

Engineers designed the Mägerle MFP 30 5-axis grinding machine to manufacture small blades, vanes, and shrouds typically used for the CFM International Leading Edge Aviation Propulsion (LEAP) high-bypass turbofan or the Pratt & Whitney Geared Turbo Fan (GTF). For smaller components, the MFP 30’s compact size maximizes useful space and facilitates smooth production flow.

For maximum effectiveness, the MFP 30 machine uses design elements from larger platforms, such as preloaded ballscrews to prevent backlash and hydrostatic wrap-around guideways on the Y-axis to provide dampening for accuracy, high metal removal rates, and extended tool life.

A space-efficient, double-sided servo-driven table dresser accommodates dresser roll lengths up to 307mm for several separate diamond rolls for different part features. Twin bearings and a servo motor drive facilitate reliable dressing across the entire speed range.

While the machine’s compact size facilitates manual loading of smaller, lighter components, larger components on clamping fixtures can be loaded through the top of the machine using a crane.

Features that support strength, flexibility, and productivity remain critical, such as rigid HSK-B80 flange mountings that support 300mm x 60mm x 76.2mm grinding wheels for wide profiles.

The MFP 30’s direct-drive, 12,000rpm, 26kW (from 1,750rpm) spindle gives power and torque at low spindle speeds for creep-feed and conventional grinding, as well as high rotational speeds for plated carbon boron nitride (CBN) grinding, milling, and drilling. Critical to such multi-process capability, the MFP 30 features through-spindle coolant for chip evacuation, longer overall tool life, better surface finishes, and higher throughput.

A 12- or 24-pocket automatic tool changer accommodates grinding wheels up to 12" as well as mills and drills. Additionally, a shop can install a measuring probe to check workpiece positioning and dimensions. Operators can load and unload the tool changer while the machine is in cycle. Operation The MFP 30’s multitasking capabilities include single-clamping and multi-operation part processing. Processing a typical turbine blade, for example, may require six operations:

Accomplishing these operations in a single part fixturing reduces cycle time and increases part accuracy.

The MFP 30’s part indexing/rotating allows grinding two profiles on one side of a turbine blade with a standard corundum wheel, then rotating the part to grind two profiles on the reverse side.

A separate system delivers clean coolant.

The MFP 30’s software addresses turbine grinding applications. Macros further simplify operator responsibilities, including standard cycles for grinding, milling, and drilling.

When choosing grinding systems for certain parts and operations, particularly in the aerospace industry, coordinating machine size and capabilities with component sizes produces multiple benefits. For reduced machining time, fewer setups, more efficient shop floor utilization, and the ability to respond quickly to frequent shifts in production volume of small parts, smaller can be faster.

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