Airplane wings require hundreds, and sometimes thousands, of holes to be drilled in complex, fragile surfaces with high accuracy, posing two challenges for manufacturers:

• Developing a method of securing parts during drilling that doesn’t cause damage
• Providing an ergonomic work environment, customizable to each worker, that allows them to drill thousands of holes per day without injury

At Spirit AeroSystems in Tulsa, Oklahoma, these challenges were especially pronounced on the drilling stations for the wedge and cove-angle components of the Boeing 787 aircraft wing. Using input from operators and Bosch Rexroth aluminum structural framing, Spirit AeroSystems developed an ergonomic workstation that significantly improved quality, reduced worker injuries, and improved throughput.

Wedge fixture

The wedge structure is a composite piece of the airplane wing’s leading edge, and there are 10 variations of the part. Each wedge requires around 300 manually drilled holes and the typical production rate is six wedges per day – 1,500 to 2,000 holes per day – no small task for any operator.

“In the automotive industry, probably 90% of drilling is automated, with only about 10% of drilling operations being done manually. In the aerospace industry, the situation is almost the exact opposite,” says Brian Lewis, continuous improvement specialist at Spirit AeroSystems.

The original assembly workstation layout used a standard, flat table to hold the wedge during drilling. But the wedge is contoured, making it extremely challenging for the operator to drill hundreds of holes in precise locations. The part tended to rock back-and-forth on its curved edge, so the operator often had to hold the part with one hand while drilling with the other hand. The lack of control from one-handed drilling, coupled with the odd position of the part, often led to drill-starts where the hole is started in the wrong spot, marking the part and in some cases, producing an out-of-spec, elongated hole.

Additionally, drilling hundreds of holes per day – even on flat, stable parts – requires thoughtful workspace design to ensure good ergonomics. Wedge line operator James Wright was plagued by the effects of poor workstation ergonomics. So, he proposed a rotating fixture – inspired by a rotisserie – that would allow the part to be positioned at any angle and height, depending on the current operator’s preferences. What started as a napkin sketch was taken to Lewis, who accepted the task of making this concept a reality.

Rotisserie development

Having worked with Bosch Rexroth aluminum framing to build tables, workbenches, and holding fixtures for other areas of the factory, Lewis immediately enlisted the help of Spirit AeroSystems Design Engineer Matt Sheets and Jay Rogers of Pacific Integrated Handling (PIH), in Tacoma, Washington, to help design a wedge fixturing system. PIH is a distributor with more than 20 years’ experience applying Bosch Rexroth aluminum framing to specialized tooling and fixtures.

Based on Wright’s sketch, the team designed the wedge fixture with aluminum framing for structural support, along with a counterbalance system to ease rotation of the wedge – an incredibly heavy part. The fixture is infinitely adjustable in height, and the ability to rotate the wedge allows each operator to set the workpiece at a comfortable drilling angle. To accommodate variations in wedge designs, one wedge end is supported by a Bosch Rexroth size 25 ball rail, allowing the width of the fixture to be adjusted to the wedge’s length.

A workstation design that once required five people to complete five units per day, now has three people completing six to seven units per day. Put another way, on an 8-hour shift, man-hours per part fell about 54%, from 8 hours per part to less than 4 hours. And the company has been able to reallocate resources from the wedge area to other operating stations. Since the fixture was put in use, rework in this area has been reduced by 80%.

Possibly the most important outcome of this new fixture is the improved ergonomics. With the previous workstation design, operators experienced back problems from bending over or leaning in to drill holes, and soreness in the upper body was a common complaint.

“The improvement in ergonomics was immediate,” Wright says. “This fixture, and the ability to adjust it to my specific needs, has really made a difference in my physical well-being. Other areas are looking to replace their old, ‘dinosaur’ tooling and fixtures – typically made of steel – with lighter, more cost- effective, and more ergonomic designs made from Bosch Rexroth aluminum framing.”

Cove-angle carousel fixture

A cove angle is also a part of the Boeing 787 wing – a structural member used in the front slats to produce lift. Like the wedge, there are 10 variations to the cove angle, and each variation requires drilling 168 holes. Cove angles require operators to drill a pilot hole and then a second hole to the specified size.

In the original cove angle workstation, operators drilled one part at a time on a typical, flat workbench. This was inefficient, since no real work was occurring every time the operator had to offload one part and load the next. Damage from drill-starts and out-of-round holes resulted in high rework and scrap rates.

The solution to these issues – a rotating carousel fixture – drew inspiration from a fixture that Sprit AeroSystems had implemented on a smaller scale in the Boeing 737 program – essentially the same part but made from aluminum rather than composite.

Cove angles are approximately 12ft long x 2" wide, making them ideal for loading onto a carousel, supported by Bosch Rexroth aluminum framing that holds five parts at a time. The carousel rotates and locks into place while the operator drills each part and moves in and out, to be closer to or farther away from operators to meet ergonomic preferences.

A monitor mounted to the structural framing displays work instruction and layout of each part. With feedback from a linear encoder, the monitor can be moved down the fixture along the part’s length. As the monitor moves, the drawing displayed corresponds to its position along the part, providing instructions specific to that exact spot on the part. After finishing one part, the operator rotates the carousel and works back along the length of the fixture on the next part.

Although inspired by a B737 program solution, the much larger cove-angle carousel fixture was especially challenging to design and manufacture. One difficulty was making a fixture that could rotate while maintaining enough stiffness to support the pressure from drilling.

Spirit AeroSystems completely outsourced the design and manufacturing to PIH, and the PIH team worked with designers and operators at Spirit AeroSystems to provide a turnkey solution that met the operators’ requirements for ergonomics and simplicity, while meeting Spirit’s cost and timeframe goals.

Since the fixture’s implementation, productivity in the cove angle area has increased by 50%, and like the wedge area, ergonomics vastly improved. The cove angle fixture’s ability to handle five parts at a time also reduced floor space and improved part-flow through the line.

Both the wedge and cove angle fixtures greatly improved ergonomics for the operators, improving productivity and quality. The return on investment (ROI) for these projects was well within the three-year timeframe set by management, based on increased throughput and reduced quality costs. Not only did these projects exceed the company’s ROI target, worker compensation issues also decreased. As a bonus, upper management at Spirit AeroSystems was impressed with the amount of input and level of engagement the operators demonstrated in the design and realization of these two fixturing projects.

Bosch Rexroth Corp.

Pacific Integrated Handling

Spirit AeroSystems

Aircraft turbines produce high output by highly compressing air in the combustion chamber. Within the engine, the high-pressure turbine sits behind the combustion tube, subjecting it to great stress from exposure to the pressure generated by combustion energy and temperatures higher than 1,832°F (1,000°C).

Hollow cooling structures in high- pressure turbine blades and nozzle guide-vanes are manufactured using the lost wax process, with molten metal poured into a mold made by a wax model of the component. A heat-proof core in the model enables manufacturers to create parts that have hollow structures. However, a foreign object or processing defect in the hollow structure can reduce heat dissipation, potentially resulting in engine failure. Manufacturers inspect the inner part of the turbine blade’s hollow structure during manufacturing and engine maintenance to prevent such flaws.

Inspection challenges

Mini borescopes with a diameter of 3mm or less were used to inspect the hollow structures inside turbine blades for residues, scratches, and cracks. A rod lens in the mini borescope provided good-quality images but suffered from drawbacks that slowed inspection, including:

• Rigid, easily damaged, long, thin lens on insertion tube
• Small images difficult to see without a monitor
• A camera unbalances the scope, making it difficult to use
• Non-articulated insertion tube; can’t look around inside hollow structures
• Insufficient illumination from weak light guide

Thin videoscope advantages

Unlike a mini borescope, thin fiberscopes and videoscopes are flexible and offer articulation. A fiberscope is made of a bundle of glass fibers, while videoscopes have a built-in image sensor. Both have a 2.4mm OD insertion tube and articulation at the distal end.

Fiberscopes are cost-effective, although images acquired through the glass-fiber bundle have a mesh-like appearance that can make it difficult for users to detect tiny defects.

Videoscopes acquire images via a sensor providing bright, clear images with no mesh-like appearance. By electrically amplifying image signals, videoscopes enable users to observe deep inside a hollow structure with a wide field of view (FOV) and sufficient brightness, even with limited light intensity. This makes it easier for users to detect residues, scratches, and other defects.

Durability

The Olympus IPLEX TX videoscope’s insertion tube has a protective resin layer and 2.4mm OD. The insertion tube’s multilayered structure prevents resin surface damage from irregularly shaped parts, improving durability.

An ordinary videoscope needs to be entirely replaced when its insertion tube gets damaged, but a detachable insertion tube allows quick replacement on the IPLEX videoscope.

Summary

Inspecting hollow structures inside turbine blades presents significant challenges that can be overcome by using a videoscope with a small-diameter insertion tube. With durability, high image quality, and articulation, inspectors can easily maneuver inside these narrow structures, viewing, recording, and archiving images.

Olympus Industrial Solutions

Manufacturing carbon brake discs for aircraft requires specific skills, so raising production as orders rose forced Safran Group subsidiary Safran Landing Systems to upgrade its manufacturing methods with help from its machine programming consultant.

Original methods

More than 200 employees at Safran Landing Systems in Villeurbanne, France, play one of three complementary roles – weaving carbon fibers; performing heat treatment for conglomeration of fibers into strong, compact stock; and machining these fibers.

Increasing orders in the global aeronautics industry motivated Safran to improve its efficiency, responsiveness, and manufacturing methods to make a more reliable product.

Automating operations

MHAC Technologies, Safran’s partner in machine programming, spoke with Olivier Clausse and his team from Safran’s method office about implementing Esprit computer-aided manufacturing (CAM) software for CNC programming, optimization, and simulation. Safran chose Esprit’s SolidMillTurn Production Plus software, which handles C-axis index and rotary milling, Y-axis index milling, B-axis index milling, and 3rd rotary axis index milling. The system includes SolidMillTurn Traditional & Advanced and SolidTturn Multispindle, a 2-axis turning add-on.

Esprit software’s automatic macros define machining origins, offsets, and assemblies when programming Safran’s CNC lathes and 3- to 5-axis milling centers. Macros can automate and optimize operations based on the type of machining being done and stock measured directly on the machine. MHAC Technologies provided made-to-measure post processors for specific machines in Safran’s workshop.

Program reduction

Equipping the shop with updated turning and milling equipment became a top priority to boost brake production.

“One-and-done assembly is becoming a necessity in order to limit work-in-progress, guarantee better quality, and offer greater reactivity,” Clausse says.

Safran engineers chose to limit the number of programs used and standardized the rest to accelerate production. Program standardization arose, in part, from inspecting carbon discs on 3D measuring machines.

“We can define several families of disc brakes, which are only differentiated by a few dimension elements or machining operations,” Production Methods Engineer Mylène Loubatières says.

MHAC Technologies worked with Safran engineers to define brake families and create related programming macros, reducing the number of programs from more than 100 to several dozen.

“With Esprit and MHAC Technologies, we chose to combine ease-of-installation with service,” Clausse says.

One-and-done assembly is becoming a necessity in order to limit work-in-progress, guarantee better quality, and offer greater reactivity

Company growth

Embracing turning and milling while using Esprit CAM technology helped Safran remain competitive in the global aerospace market. In late 2018, Turkish Airlines announced that it had chosen wheels and carbon brakes from Safran Landing Systems for its fleets of 25 Airbus A350-900 and 25 Boeing 787-9 long-range aircraft. With artificial intelligence (AI) programming and collaboration between MHAC and Clausse’s team, Safran Landing System’s aircraft braking program is accelerating.

DP Technology

MHAC Technologies

Safran Landing Systems

The commercial drone delivery industry is quickly gaining popularity, attracting traditional delivery service providers and startup unmanned aerial system (UAS) manufacturers. The primary obstacle for these ventures is the strict body of regulations governing production and operation in the commercial market. Designing for these criteria early is much safer and more cost-effective than conforming to regulations later in deployment. Continued adoption of commercial drones depends on field programmable gate arrays (FPGAs) that enable them to meet these regulatory requirements while also solving size, power, and reliability challenges; eliminating the risk of high-altitude radiation-related failures; and protecting against a growing range of cyber threats.

The main factors affecting drone avionics often require tradeoffs between security, processing performance, power, mass, and form factor. These can all be addressed with the latest generation of FPGAs.

FPGA solutions

Drone designers need small, power-efficient, reliable electronic components that are secure against malicious threats. Stringent power, size, and weight constraints impact battery life. In addition to these requirements, UAS are subject to harsh environments such as neutron effects, moisture, and extreme temperatures.

Like all avionics systems, those in UAS need to be as compact and as light as possible, minimizing or eliminating heatsinks. Smaller electronic components reduce the printed circuit board (PCB) and electronics enclosure size, reducing total system weight while improving efficiency, battery life, and flight time.

Flash-based and silicon-oxide – nitride-oxide-silicon (SONOS)-based FPGAs address these challenges for all drone system applications including sensor interfacing, flight control, and image processing. These types of FPGAs consume the least power – up to 50% less power than their static random-access memory (SRAM)-based counterparts (Figure 1). They remove the need for heat sinks and reduce the weight of the overall system without sacrificing total system efficiency.

Because commercial UAS avionics must meet DO-254 standards, drone manufacturers must select components with an extensive service history, necessary for certification. For aviation manufacturers, this means selecting vendors that can provide the necessary documentation and guidance for DO-254 certification.

Selecting components that are immune to configuration neutron single event upsets (SEU) is another important consideration (Figure 2). Neutron flux (neutrons per cm2 per second) increases with altitude. For example, rising 40,000ft above sea level (a typical commercial aviation flying altitude) increases neutron flux by a factor of 515. Neutron SEU could result in a device malfunction and failure, resulting in a catastrophic event if a drone breaks down and lands on a moving vehicle at high speed, or if it’s transporting vital supplies to a patient.

For drones flying in U.S. states such as Colorado, Utah, and New Mexico with a ground-level elevation close to 10,000ft, neutron effects begin to be noticeable, increasing the neutron flux 12x. Flash- and SONOS-based FPGAs are immune to radiation-induced configuration upsets and won’t lose functionality at these altitudes.

Security is another concern in aviation applications. Security starts during silicon manufacturing and continues through system deployment and operations. Flash- and SONOS-based FPGAs represent the industry’s most advanced and secure programmable FPGAs. In addition to embedded security crypto-processors, these FPGAS include key capabilities required to create a trusted and secure hardware platform for a secure embedded system, making them invulnerable to cloning, copying, and reverse engineering. Sensitive data in embedded systems is protected from malicious attacks. Some of these key capabilities not offered in SRAM-based FPGAs are secure key storage using physically unclonable function (PUF) and licensed, patent-protected differential power analysis (DPA) pass-through. Any programmable device is vulnerable to attacks, so designers need to buy electronics with security features produced by trusted manufacturers.

Conclusion

Drone delivery today is heavily restricted by transportation authorities, primarily due to concerns for human safety and privacy. By designing drones to mitigate these concerns, manufacturers can directly influence the industry’s acceleration. Flash- and SONOS-based FPGAs enable developers to account for safety, security, and reliability throughout the design and deployment processes, while also reducing the size and cost of drones and mitigating the risk that radiation-related configuration upsets will cause them to fail at higher altitudes. These FPGA characteristics solve some of the biggest challenges that drone and electronics designers face and can be the answer to making commercial drone delivery a regular occurrence in the very near future.

Microchip Technology Inc.

About the authors: Maria Zaitchenko is a student at the University of Toronto, in the faculty of Applied Science and Engineering. She can be reached at m.zaitchenko@mail.utoronto.ca . Julian Di Matteo is senior product marketing engineer, space and aviation, Microchip. He can be reached at julian.dimatteo@microchip.com.