MMC Magazine

Hideyuki Fujii Gifu Aero Group, Aerospace Dept.Joined in 2015 / Shogo Tanaka Group Leader, Gifu Aero Group Assistant Manager, Aerospace Dept.Joined in 1999 / Hiroki Okumura Production Engineering Group Alloy Production Dept.Joined in 2014

The DSA Series launched in September 2019 was developed for machining heat resistant alloys that are commonly used in aircraft engines. In the process of machining heat resistant alloys, heat caused by friction can easily build and cause work hardening. For this reason, cutting tools are required to have both accuracy and durability. The developers’ commitment to producing the desired features to realize such difficult to achieve characteristics through repeated field testing over a three-year period resulted in innovative new products.

Three Outstanding Technologies and Cemented Carbide Materials that Supported these Technologies

―Why were DSA series developed?

Tanaka:“According to forecasts issued before COVID-19, the aircraft market would require more than 40,000 new aircraft over the next 20 years. With each of these requiring at least two engines, at least 80,000 engines will need to be manufactured. This means that tools for machining materials for those engines will be needed as well. Mitsubishi Materials manufactures WSTAR drills for multipurpose use, and we have an expanded range of drills for different materials (M, K, N, H types); however, the drills for machining heat resistant alloys (S type) were not yet available. This is why developing the DSA series and responding to market needs have been important issues for the company over the past few years.”

Fujii:“In October 2016, the Aerospace Department was established. I was assigned to the department and put in charge of the development of the DSA series of solid carbide drills for machining heat resistant alloys.“

 

―What are the conditions required for heat resistant cutting tools?

Fujii:“Aircraft parts require absolute reliability, and the materials are expensive. Therefore, it is essential to have high machining accuracy to avoid waste due to defects. In addition, cemented carbide tools are expensive, so customers may want to re-manufacture and reuse tools to reduce costs. This makes it important to design geometries that are easy to regrind and re-coat.“

Okumura:“We considered materials based on hardness, toughness and durability as absolutely necessary conditions because the characteristics of cemented carbide change significantly depending on the balance of tungsten carbide and cobalt. As a result of repeated trial and error, we developed DP9020, a new PVD coated cemented carbide material with increased hardness and toughness as well as wear resistance.”

―What are the characteristics of three major selling points?

Fujii:“Coolant, honing and margin all have important characteristics. When machining heat resistant alloys, discharge of coolant significantly changes lubricity and cooling ability. The through coolant hole is triangular in shape, the same as the existing type because it has proven performance. It was found that this shape increased lubricity without lowering drill rigidity. In regard to honing, which is associated with sharpness and durability, we sought a form that could achieve both stable chip generation and be resistant to edge chipping. Through discussion to determine the ideal margin width and edge form, we minimized the contact area to restrict the machining heat and reduce work hardening.”

Tanaka:“In the machining of heat-resistant alloys, coolant is extremely important. Therefore, during development, we first determined the specifications for the coolant hole, then optimized the cutting edge form, honing and margin. In addition to simulations of fluid and rigidity analysis, we observed chip generation with a high-speed camera. This enabled us to adjust the form during development.”

Seeking the best solution through in-depth field testing

―What was the main priority during the development process?

Fujii:“In regard to the honing, which influences tool life, we checked past development cases and took the time needed to identify the best form. We repeated the cycle of hypothesis and evaluation. The possibility of sudden defects in tools cannot be determined before actual machining.”

Okumura:“It’s the same as the carbide material. We checked the consistency of the carbide material used for the prototype drills and repeated this for the materials used for the actual production drills. This was done because the batch sizes of the material used for prototype drill testing and the material used for the manufacture of the mass production drills are very different. Changes in quality due to this difference in batch size would lead to differences in manufacturing conditions between testing and mass production. Therefore, the quality and consistency check are the most important process in the material development.

―How was the development process?

Tanaka:“We started development in October 2016, the same time the Aerospace Department was established. It took about two years to complete basic development, including the design, creation and evaluation of a prototype, then we repeated field tests along with confirmation for mass production. As a result, it took almost twice the time it takes to develop a standard product.”

Fujii:“Although it took time to launch the product, our Sales Division actively advertised it to customers during development, which allowed us to gather information from a wider range of machining cases. In fact, customers use tools to machine materials in complicated forms, not just in the standard blocks used during the in-house testing environment. Tools must function under the customers’ operating environment, not just in the test environment. Knowing the performance of the product being used by actual customers was invaluable for us.”

Okumura:As we came closer to commercialization, we needed to consider materials for stable production. Even if our prototype could be made perfectly, we needed to address a number of issues to commercialize the actual product. After stabilizing the manufacturing process, we needed to satisfy customer requests after the products were introduced to the market. This is why we have to keep improving.”

―Please give our customers a message.

Tanaka:“It goes without saying that for safety, aircraft parts are required to be absolutely reliable. This is especially true for parts used in engines. Our tools obtained approval for use in machining engine parts through field tests, which increased our confidence. The global supply system for the DSA series (including regrinding and recoating) has already been established, so customers can be rest assured that they can get the parts they need when they need them. We are also able to respond promptly to special requests for products. Please feel free to contact us any time about the products. We’re also planning to expand product use to the heavy electric machinery industry.”

Fujii:“The more customers use products, the more we benefit from feedback about performance evaluation over a wide range of conditions. We need to analyze such evaluations to prepare for prompt responses to individual cases. This calls for a system that allows us to accurately and quickly satisfy customer needs.”

Okumura:“The launch of new products is the beginning of the project, not the goal. Our mission is to respond appropriately to a wide variety of requests from customers after they use the products at their plants. Please feel free to contact us for any small or complex issues.”