Aerospace parts manufacturers face numerous machining and finishing challenges, one being the introduction of new alloyed materials. To increase fuel efficiency and produce lighter planes, incorporating materials that are lighter, stronger, and can better manage heat is crucial. While these alloys have amazing characteristics, they can sometimes be difficult to process, resulting in the need for grinding expertise and the latest technologies. Without optimizing the grinding process, parts made with these new alloys may have poor surface quality, internal metallurgical damage, increased part cycle times, and higher manufacturing costs.

Another challenge is bottlenecks on the manufacturing floor. Some customers use wire electric discharge machining (EDM) to carve profiles and shapes into various aerospace components. While EDM is effective for parts with faces that are tough to access, grinding may be a better option for many operations. Wire EDM machining is initially less expensive than grinding, however, using EDM can take a long time to complete a part. Grinding is much faster in removing material, and while it may be more expensive upfront, the benefits of grinding – saving production time, unclogging bottlenecks, and having a smooth-running line – almost always offset the cost and result in a substantially more efficient process.

Grinding vs. machining

Aerospace components generally have very low Ra surface finish requirements and tighter dimensional tolerances, as well as precise complex shapes and forms. Grinding is much better at producing these precision parts and holding necessary shape and dimensional tolerances due to the way the material is removed. During grinding and machining, the material ground off is removed as chips. In grinding, much smaller chips are created which allows for more precise shapes and smoother surface finishes, while machining produces significantly larger chip formations.

Due to the larger chips and aggressive cuts of material, traditionally, machining has generated higher material removal rates (MMR) than grinding. With newer grinding technology, this isn’t necessarily true. For example, new Norton TQX grain technology has been able to hit Q’ (Q- prime specific material removal rate) values of >3in3/min/in in creepfeed grinding of aerospace components, which is usually the max Q’ achieved with ceramic grain bonded wheels. These values rival those of machining processes. Figure A (pg. 30) shows the improvement of TQX versus other ceramic grains. With the other ceramic grains, as Q’ is increased, G-ratio (the volume of material removed from the work per unit volume of wheel wear) declines and eventually bottoms out at about 3.5in3/min/in. Alternatively, TQX can increase G-ratio with increased Q’ up to 2.5in3/min/in and maintain this high G-ratio at Q’s over 2.5in3/min/in, but in this case, TQX reaches a Q’ of 5.5in3/min/in. This new technology challenges machining processes, producing parts with improved quality and eliminating the need for further finishing processes.

How materials affect grinding

Different material types affect grinding processes, depending on the material hardness, variety of material properties (especially newer alloys), and behavior of the material once it heats up (among other operational factors). This means one grinding wheel type or specification may not work for all materials or it may not work for various material types within similar applications. It depends on many factors, so consult with a grinding expert to determine grinding wheel requirements based on material type, and how to consolidate specifications and wheel sizes to keep inventory levels low.

One issue often seen with some newer alloys and more exotic materials, typically used for turbine blades, is they become gummy or act soft upon grinding, especially prior to heat treatment. Examples include Rene 108 and Inconel. Grinding gummy materials can load up a grinding wheel, which will result in heat generation, burn, poor surface quality, and the need for additional dressing. In this scenario, generally a softer grade, porous grinding wheel is needed with a friable abrasive that’ll fracture a bit easier and produce new, sharp cutting points to continue grinding through the soft material.

Additive manufacturing

Additive manufacturing (AM) for aerospace components adds simplicity to making complex parts, including those with intricate internal shapes and channels. It also gives the ability to produce parts with different metals or materials that weren’t in use before due to difficulty in grinding, machining, etc. With AM growing, grinding is still relevant. For example, an abrasive cut-off wheel can separate 3D-printed parts from their build plate. Afterward, a grinding wheel can grind down this metal plate, flattening it, removing any additive material, and ensuring the appropriate surface finish so the plate can be reused for the next part.

Abrasives are also used in AM finishing steps such as improving dimensional tolerances and surface quality. Although the growing use of AM overall will decrease the need for creepfeed grinding of aerospace components, new requirements will move toward deburring and finish grinding. Parts with precision features will require finish grinding regardless of how they are initially produced. The main difference with finishing 3D-printed parts compared with finishing traditionally made parts may just be that additively manufactured parts need less stock removed to get to the final geometry and surface finish.

Norton | Saint-Gobain Abrasives

About the author: Arianna Smith is corporate application engineer for Norton Saint-Gobain Abrasives. She can be reached at arianna.smith@saint-gobain.com.

The post-COVID-19 frenzy to return to normal has created a bevy of problems for manufacturers sourcing raw materials. Inflationary pressures and tariff uncertainty have challenged the ability to secure materials and have created more volatility in pricing and delivery times. These challenges to affordable sourcing and predictable availability create the perfect environment to explore new options for producing parts and components. If necessity’s the mother of invention, then there’s no better time to explore aerospace sourcing and manufacturing alternatives than after a pandemic that made us all realize the true meaning of necessity.

There may have been no greater example of how globally interconnected and vulnerable our supply chains are than when the Ever Given ran aground in the Suez Canal earlier this year. In the United States, we watched spellbound as we realized an event halfway around the world could impact our ability to get what we needed. Speaking to The New York Times, Ian Goldin, a professor of globalization at Oxford University said: “As we become more interdependent, we are even more subject to the fragilities that arise, and they are always unpredictable. No one could predict a ship going aground in the middle of the canal, just like no one predicted where the pandemic would come from. Just like we can’t predict the next cyberattack or the next financial crisis, but we know it’s going to happen.”

Reimagine materials

I’ve seen firsthand the recent supply interruptions across industries – from aerospace and electronics to automobile manufacturing and recreational products. The uncertainty has driven many of our customers and prospects to consider domestically supplied options while concurrently posing questions that could improve manufacturability or allow conversion of the materials from which parts are made. Less expense, shorter production lead times, reduced waste, and more sophisticated part design are timely considerations that for many, make converting from metal to composites the right talk now.

Converting parts from metal to other materials creates weight savings that offer one of the greatest opportunities for aerospace to make dramatic cuts in carbon emissions. While some industries address the issues of carbon neutrality with more efficient manufacturing and clean energy, most aircraft emissions are generated through operation, such as burning jet fuel, which can be addressed by cutting weight.

Additionally, transitioning to more reliably sourced advanced materials presents an opportunity for designers to reimagine parts, identifying potential for part consolidation that can ultimately optimize the supply chain. For weight savings, customers will often look specifically at existing heavy parts. We recently evaluated converting a part that weighed 60 lb to 30 lb. Then, we were also able to identify additional smaller parts that could save incremental weight. For example, the client hadn’t considered a cable bracket that could save 0.5 lb per part used several times across platforms. Evaluating the parts with an understanding of what was now possible to engineer created a greater potential for collective weight savings that the client might not have considered.

Increase flexibility

With raw materials, the question isn’t just if they’re available and affordable, but also how well you can work with them – what can they handle? Increasingly, the manufacturing partners we work with are using modern equipment, robotics, and software- driven solutions versus traditional manufacturing processes, and the companies embracing these new options are starting to set themselves ahead of legacy companies. Flexible manufacturing capability allows for shifting workers across suppliers to accommodate capacity changes. As we learned from the pandemic, workers have changed how they want to work, increasing the struggle for employees and directly impacting the supply chain. It’s increasingly important that manufacturers have some flexibility, allowing for fluidity in how to apply and keep their workforce.

Minimize risk

Many choose raw materials and legacy manufacturing processes in pursuit of lower part price. But hidden costs increase final part cost when materials are not sourced domestically, whether it’s transportation, potential for lost shipment, time, delays (traffic jam in the Suez Canal), or tariffs. Regulating trade imbalances, regardless of the administration, always creates volatility. Not having to guess the price of tariffs creates more certainty and means an American-made part might not come at a premium.

Working with domestic suppliers can also have significant advantages to maintaining the security of your designs and supply chains. The Cybersecurity Maturity Model Certification (CMMC) from the U.S. Department of Defense measures contractors’ cybersecurity capabilities, readiness, and sophistication. It helps ensure the supply chain is protected from threats through robust internal processes and allows mitigating the threat that could shut down production or steal data. This risk is further reduced when both partners are CMMC compliant.

Stay ahead

Updating for the future isn’t as difficult as designers and manufacturers may imagine. With a little education and more engineering, there’s a way to design for the future while making your product and business more secure. Now is the time to secure yourself to lessen the impacts of future uncertainties, which last year may have been about keeping customers, but today is likely focused on keeping workers and supply chains intact. Take steps to modernize your manufacturing processes or products to give your customers what they want.

What’s easy now may not be so easy in the future, but that isn’t set in stone – or even aluminum.

Alpine Advanced Materials

About the author: Roger Raley is president of Alpine Advanced Materials. He can be reached at 469.490.1470.

August 2021 winner:

Joseph E. Yehoda, Ph.D., Technology Director, Diamonex, Allentown, Pennsylvania

How long have you been in the aerospace business? More than 25 years.

How did you become interested in aircraft? From an early age, I enjoyed going to air shows as well as the U.S. Air Force museum in Dayton, Ohio, and the Smithsonian Air & Space museum in Washington, D.C. A highlight was attending the air show at Edwards AFB in 1987 that celebrated the 40th anniversary of transonic flight.

What is your favorite aircraft and why? The Supermarine Spitfire. Its elliptical wing design and bubble canopy gave it a very distinctive look. It was an innovative aircraft for its time.

Runners-up:

Tom Steinbrunner
Electronics Engineer
National Air and Space Intelligence Center
Wright-Patterson Air Force Base, Ohio

Mattthew Empett
Facility Engineer
Collins Aerospace Binghamton,
New York

Submission procedure

To enter the contest, visit www.AerospaceManufacturingAndDesign.com/Form/NameThatPlane and fill out the provided entry form. Only completed forms will qualify. A full set of rules is provided.

Have fun, and good luck!