The aerospace manufacturing industry requires cutting-edge processes to enable necessary efficiency and durability within tight size, weight, and power (SWaP) requirements and current machining techniques may be insufficient, giving rise to less conventional methods such as pulsed electrochemical machining (PECM).

In PECM, a workpiece and a tool in its inverse shape are positioned with a tiny gap between. An electrolyte solution flows through the gap to remove waste materials from machining. The inversely shaped tool moves toward the workpiece, and a pulsing DC current is applied – dissolving the workpiece material until the desired shape is achieved.

Voxel Innovations

Turbines, impellers, blisks

Turbomachinery components are subjected to high forces, require complex 3D surfaces, and demand tight tolerance features. Components such as bladed discs (blisks) and integrally bladed rotors (IBRs) are a growing but demanding application which embodies many of these challenges. Normally manufactured by forging a large nickel- or titanium-alloy disc followed by 5-axis CNC milling of the complex airfoil geometry, as airfoils become thinner or include advanced 3D features or tip geometries, high CNC milling speeds become difficult due to blade vibrations or access between airfoils. Similar geometric challenges also exist with non-rotating components such as stator and vane segments.

Alternative methods such as casting, powder metallurgy, friction welding, or additive manufacturing (AM) all have the potential to reduce material use but come with their own challenges. Casting involves differential cooling rates for thin airfoils vs. thick walls in the hub, creating material stresses that can cause cracks in large components. Some AM and powder metallurgy techniques also have scale limitations due to thermal distortions. In general, near-net techniques also come with additional material property risks which have not been fully addressed for critical components. Finally, in most cases, near-net options require final machining to correct any tolerance distortions or improve surface finish, especially in applications with high Mach number airflow.

Many rotating and static turbomachinery components, including blisks/IBRs, turbines, and impellers, have shared design and manufacturing challenges. They’re all highly sensitive to geometrical deviations and material properties and any variation can compromise the component’s efficiency and lead to imbalances while in use.

Fortunately, PECM poses a worthwhile alternative value proposition. PECM is neither a thermal nor contact-based process, meaning cooling rates and vibrations from cutting are nonexistent. Instead, PECM dissolves the material atom by atom to the desired shape while permitting high aspect ratios and maintaining an attractive material removal rate. The precise shape and smooth surfaces made possible by PECM greatly improve the efficiency of the turbomachinery. PECM is also flexible and can be used for bulk material removal or final finishing of a near-net manufactured part.

Metal AM, then PECM

With the increasing prevalence of AM in aerospace, it’s worth noting that PECM can also be used as a finishing process, not just the primary machining method.

Metal AM has found footholds in aviation engines (combustion devices, housings, heat exchangers), rocket engines (injectors, combustion chambers, impellers), and a range of satellite applications. However, surface roughness is a common issue in 3D printing, particularly remnants from support structures. These surface irregularities can lead to incorrect fit, increased friction, corrosion, and cracks. However, PECM can address surface roughness in post-processing. Although PECM has similarities to electropolishing, it differentiates itself by using a locally small gap between electrode and workpiece. Custom PECM methods developed by Raleigh, North Carolina-based Voxel Innovations make it especially efficient for removing macro-level roughness associated with AM support structures, downskin surfaces, electron beam melting (EBM) powder bed, or freeform AM methods.

Metal AM also has limits on wall thickness and aspect ratios and can be challenged with distortions due to the inherently thermal nature of the process. Instead of compromising design to work within these limits, PECM creates thin-walled or critical features in a secondary machining step.

Another potentially cost-effective solution may be to add extra stock material to the AM part’s surface, then use PECM to dissolve the extra material into tolerance. Similarly, the metal AM build parameters could be adjusted to speed up the deposition rates while using PECM to address the resultant geometry more efficiently. As metal AM grows into more volume production applications, a hybrid approach of metal AM followed by PECM may be a more efficient, effective manufacturing approach.

High-temp applications

Material choice is a careful balancing act, particularly in aerospace, and design engineers must optimize for bonding and joining concerns, corrosion, system mass, and cost, all while considering thermal resistivity and matching coefficients of expansion.

In high temperature applications in liquid rocket engines or hypersonic systems, these needs cannot be met by standard material choices. Ceramics and ceramic-composites with high thermal conductivity and resistance to corrosion may seem like an ideal solution, however, their cost, bonding challenges, and forming limitations impede broader implementation. That leaves high temperature metal alloys including nickel super alloys, titanium aluminides, refractory metals, and high entropy alloys that can be difficult to machine conventionally due to heat and wear resistance – exactly the reason they’re used in high-temperature applications. The difficulty of machining these materials is especially problematic in heat exchangers, given that these components function at their highest efficiency only with high aspect ratios, thin walls, and tight spacing. Many conventional machining processes rely on heat or contact to form features, which can deform thin walls and may lead to irregular channel sizes (and uneven heat flow) or incorrect fit with other components. Many electronics applications require a different set of material choices. Chip-level cooling and high-power radio frequency (RF) or microwave devices in airborne applications may require low coefficient of thermal expansion (CTE) or matching thermal expansion of another material (e.g., silicon). This can include materials such as metal matrix composites, refractory metals, or low CTE Invar and Kovar – all challenging to manufacture. In addition, these electronics applications often require precise depth and wall thickness control to manage heat transfer and packaging requirements. Cryocoolers used for cooling infrared cameras sensors are another example of hard-to-machine geometries, given the typical requirement of high aspect ratio cooling features.

Traditional CNC milling or EDM may be too slow, too expensive, or lead to compromised designs. In contrast, PECM is insensitive to the mechanical properties of the materials and can machine nickel super alloys as fast as copper or aluminum. In addition, the low forces make it an especially good fit for thin wall features and high aspect ratios.

Ultimately, cost is among the most decisive issues for any manufacturing process. Parallel production, made possible through PECM, creates many slots, pockets, or other features simultaneously in the same vector, enabling higher density features, faster production, and lower cost per part.

PECM excels in smooth surfaces, high aspect ratios, high feature density, and thin walls, even in hard-to-machine materials. All of this may be achieved in large quantities and at comparatively low cost, which is why aerospace companies should consider leveraging PECM.

Voxel Innovations

qualifying parts for aerospace takes on special significance when parts are 3D-printed. Metals and polymers used to make 3D-printed components are essentially forged on the fly, so there may be questions about material integrity that must be answered comprehensively and scientifically. Especially with flight-critical parts, the technology used to accomplish this task is computed tomography, better known as CT scanning.

Qualifying

A decades-old technology, CT scanning is a viable way to peer into and through a workpiece to uncover any hidden internal flaws. CT scanning also allows additive manufacturing (AM) users to verify that their equipment is functioning properly and that their processes are sound and repeatable – able to produce the same metallurgical and mechanical characteristics on the parts 3D printed today and a year from now.

CT scanning uses an X-ray source to generate digital slices of an object from multiple angles. Software can then reconstruct the 2D images into a highly accurate 3D model with a corresponding data set suitable for a variety of analyses. Porosity, delamination, cracks, voids, and other defects are clearly visible, as are internal part features that would otherwise require cross-sectioning and other destructive methods to qualify.

Details matter

In aerospace-grade AM metal parts production, laser powder bed fusion (LPBF) processes, including selective laser melting (SLM) and direct metal laser sintering (DMLS), are most used. These technologies also have the most expensive equipment, and due to LPBF’s relatively low build speeds and high material costs, it’s not cost-effective for a manufacturer to print multiple iterations of a full-size workpiece and CT scan each one to determine the perfect process setup.

Instead, manufacturers must develop production operating parameters by printing small test cubes at various locations and orientations within the build chamber. These are then CT scanned for attributes such as material density and consistency, separation between layers, and dimensional accuracy. An operator who finds defects can adjust laser power and other variables, printing multiple test specimens to optimize productivity and part quality.

This process is then repeated with larger parts, and those with complex geometries representative of the target workpiece(s). Design elements such as cooling channels, overhangs, and various wall thicknesses can also be repeatedly evaluated until the metal fabrication process is predictable and productive.

Material commitment

Testing represents a significant investment, well beyond that of the equipment itself. Any metal AM parts provider should adequately budget for testing in terms of production time, raw materials, operator training, and access to CT scanning equipment and software. Expect up to a year of process development for any new 3D printing technology, followed by several months of fine-tuning for each subsequent machine.

Aluminum, titanium, Hastelloy, and Inconel superalloys are widely accepted by aircraft manufacturers, but greater scrutiny is expected and understandable when parts are built or grown via 3D printing rather than machined from billet. There are also new alloys and hybrid powder blends possible, all of which require extensive testing prior to flight use.

CT scanning has shown to be an important tool for the qualification of these and future materials. This is true for the 3D-printed brackets, fuel nozzles, and turbine components made from them and for the raw powder itself. Manufacturers can use CT to analyze high-resolution models of individual grains only a micron or two across, scanning for porosity and irregular grain shapes or sizes that in large enough numbers might negatively impact finished-part integrity.

Contamination is also a concern for manufacturers using metal 3D printing, and it can be avoided only through strict material handling and sourcing procedures. It’s critical to have the means to find contamination when it does occur and identify any uses of recycled powder. These occurrences are easy to spot with CT scanning, with faults appearing as bright spots within the part image.

Scaling up

Use of metal AM in aerospace is poised to grow throughout the coming decades. The design freedom and opportunities for lighter, stronger, and more fuel-efficient components easily offset the obstacles. Furthermore, 3D-part printing will become more efficient.

AM equipment manufacturers continue to deliver machines that are faster, more accurate, and simpler to use, while CT scanning providers and software firms are keeping pace by developing complementary systems. One example is software-based mesh compensation. Though not focused on any specific industry, it reduces the number of iteration cycles during the design phase of additively manufactured parts, anticipating distortion and automatically compensating for it within the part geometry.

Build strategy also plays a role. For instance, the means to dynamically adjust beam size, power, and traverse speed can profoundly impact part quality. Therefore, it’s critical to establish a feedback loop between the as-scanned and as-designed part models, comparing the two and optimizing build parameters to minimize differences.

Volume Graphics and its parent company Hexagon continue to work closely with customers, material providers, and metal AM equipment producers to connect various software tools used during the manufacturing process and share data seamlessly in real-time. This includes the CAD system used to design the additively manufactured parts, simulation software used to model performance, and inspection software to examine and analyze the final workpiece. By closing the loop on these systems, aerospace manufacturers will have the ability to design and produce better parts more quickly, more efficiently, and more consistently.

Volume Graphics

About the author: Philip Sperling is Volume Graphics’ product manager for additive manufacturing. He can be reached at philip.sperling@volumegraphics.com

Compared to peers, aerospace companies that have automated accounts payable (AP) processes spend significantly less time and resources processing the hundreds or thousands of invoices their suppliers send each month. Before AP automation, most of these invoices arrived by mail or as emailed PDF files, requiring the AP team to manually input, code, and approve them in a slow, error-prone process that could take up 84% of their time.

This outdated, manual approach slows invoice processing and leads to undesirable outcomes. Not only do margins become thinner, but suppliers and employees must manually resolve invoice exceptions, resulting in inconsistent payment cycles and errors that frustrate both parties. Furthermore, in a COVID-19 world where a large part of the workforce is still remote, paper-based invoicing processes make business continuity difficult.

The good news is that aerospace companies can overcome these challenges by automating accounts payable and procure-to-pay processes. There are three primary reasons to do so.

1. Improve profit margins

Streamlining and transforming procure-to-pay (P2P) processes with AP automation improves cycle time, ensures accuracy, and enables straight-through processing of most incoming invoices. With an automation solution, aerospace companies can remove paper from AP while also eliminating invoice exceptions that require human intervention (e.g., an invoice that doesn’t match any purchase order). For example, one major U.S. defense contractor automated 88% of the roughly 25,000 invoices received from more than 15,000 suppliers each month.

By automating AP, companies can reduce the costs of internal processes, improving profit margins, and the AP team can now focus on more important areas of operations.

Additionally, AP automation provides real-time visibility into all invoices and more control over when they are paid. Chief financial officers (CFOs) can optimize cash flow and make better decisions with real-time visibility into outstanding liabilities.

When a company relies on manual processes, it’s difficult to take advantage of all the early payment discounts because AP may not be able to pay every invoice within the early pay discount window. Decreasing process time from days to minutes, firms can decide whether it’s worth paying an invoice early or waiting to extend their cash flow.

Although it might be a no-brainer for one aerospace company with a huge cash position to take advantage of every early payment discount, other companies might want to hold onto more cash, instead of taking a potential discount. In the latter scenario, the company would gain cost efficiency benefits of AP automation, while protecting cash flow by holding payment until it’s due.

2. Keep the supply chain intact

Aerospace companies depend mightily on their supply chains. If a supplier doesn’t send materials, equipment, or other components in a timely manner, an aerospace operator might not be able to fulfill its contracts, impacting revenue. To achieve their objectives, they need a supply chain that’s working efficiently.

If an aerospace company isn’t able to pay suppliers in a predictable, timely fashion, it shouldn’t be surprised if those suppliers decide to reduce favorable terms – or, at the very least, stop shipping goods on credit.

By paying suppliers on time, AP automation helps companies overcome these challenges and ensure their supply chain keeps humming. The supplier experience improves because suppliers have real-time insight into the status of their invoices and when they can expect payment.

3. Ensure business continuity

Although the number of teams working from home has been steadily increasing through the years, COVID-19 forced many businesses to rapidly adapt to remote work early in 2020. Companies that were still relying on paper-based invoicing processes learned how difficult it can be to pay suppliers punctually when invoices arrive at unoccupied offices.

With the right solution, teams can work from anywhere – dynamically shifting between home and the office as needed – and even process invoices on a smartphone with AP automation.

Modernized accounting

Aerospace companies often handle thousands of invoices every month. When these invoices involve manual processing, it’s easy to imagine how quickly they can pile up.

By continuing the digital transformation journey and investing in AP automation, aerospace companies can become more agile while increasing profitability – delivering more value to all stakeholders, including customers, suppliers, employees, and investors.

Transcepta

Shan Haq is vice president of Corporate Strategy and Development with Transcepta, a cloud-based procure-to-pay platform. He can be reached at info@transcepta.com.

Adobe Stock | Elnur

While encouraging signs show business returning to pre-COVID-19 normalcy, manufacturers in capital-intensive global aerospace and defense (A&D) industries still face potential long-term impacts on supply chains due to major disruptions from the pandemic.

COVID-19 brought a core supply chain challenge to light: inventory surplus. No one could have predicted a global pandemic would stop production on such an enormous scale, suddenly creating excessive amounts of inventory to manage.

Thankfully, leading manufacturers have been able to recoup losses endured during the pandemic and protect cash flow and liquidity by putting an actionable, data-driven inventory optimization strategy in place – starting by gleaning critical insight from inventory in their factories. There are several ways aerospace manufacturers can drastically reduce inventory and establish operational command to thrive in a post-COVID-19 economy.

Avoid excess inventory, shortages

Supply chains can evolve to accommodate changes such as shifts in demand, order mix, product process variations, or outsourcing. While evolution is a natural part of the supply chain cycle, increasingly complex and unexpected changes can significantly impact manufacturers’ ability to create and deliver products if they don’t have the tools to see problems coming and pivot. Failure to react quickly and efficiently can increase inventory or generate shortages that harm the bottom line and customer relationships. These battles become even more problematic when teams rely on antiquated systems.

Spreadsheets and home-grown business intelligence solutions have served manufacturers well in the past, but these resources aren’t sufficient given the growing complexity of globalized supply networks. Despite evolving technology, teams still often turn to spreadsheets because existing systems lack trusted data and workflows. Leading companies are tapping into analytics, automated workflows and dashboards, advanced collaborative tools, and artificial intelligence (AI) to boost visibility and actionability across the factory.

Powerful insights and purpose-built analytics allow teams to quickly prioritize and respond to urgent actions that can’t be predicted with traditional tools; get a global view of supply and demand data; fix inventory and delivery issues when demand changes; share inventory information and collaborate with colleagues on inventory issues; and standardize inventory processes with built-in workflows.

Adobe Stock | enanuchit

Crisis management

During the pandemic, supply chain leaders learned they need a viable crisis-resilient inventory optimization plan to adjust cash and execute plans quickly for on-time delivery. Although they can’t predict what crisis will upend operations, supply chain leaders know the best defense against disruptions is to be prepared.

Effective ways teams can adapt after a crisis to better manage inventory operations include:

Prioritize, simplify daily work for the buying team – Institute an inventory triage process and establish a simple standard workflow for buyers and procurement leaders so they can focus on the most critical actions first and stay organized in a crisis. Supply chain leaders can also organize specialty teams to tackle the highest priority initiatives, such as shortage or surplus inventory. Collaborating and moving in the same direction frees up time for teams to focus on revenue-building initiatives.

Monitor progress, results to identify buyers who need more support – A spike in current shortages, late placement of purchase orders, or other metrics could highlight instances where buyer workloads must be rebalanced. Managers’ support can relieve some of the burden on team members and keep executive and front-line teams completely in sync and in control of the work ahead.

Manage accountability with task ownership, clear timelines – Leaders must establish operational processes to keep activities moving forward, assign owners and due dates to critical items related to shortages or excess, and report on item status in regular meetings.

Share up-to-date resources to help everyone act quickly, keep production moving – Equip teams with the analytical tools and workflows needed to act quickly on shortages and other procurement issues to avoid production stoppages. Align all team members on which parts and customer orders are most critical and which suppliers are most vulnerable. Equipped with the most accurate information, teams can prioritize the supply needed and determine how to allocate constrained supplier and production resources.

Conclusion

Although COVID-19 upended the aerospace supply chain in 2020, manufacturers can take control of inventory management to achieve resiliency and agility as they continue to ramp up operations. As 2021 brings the promise of a return to normalcy, aerospace supply chain leaders can get back in charge by using advancements in factory technology to address long-term industry impacts and any future crisis that might cause disruption.

LeanDNA

About the author: Richard Lebovitz is the founder and CEO of LeanDNA, an analytics platform for factory inventory management. He can be reached at richard.lebovitz@leandna.com.