MMC Magazine

Joint development of innovative helical broaches

Aisin AW Co., Ltd. holds the world’s top share of the automatic transmission (AT) market. The company’s work on advancing processing technology utilizing large-diameter helical broaches has drastically improved AT production efficiency. In this feature, we focus on a new project between Aisin AW and Mitsubishi Materials.

Committed to maintaining its position as the world’s No.1 automatic transmission manufacturer and to lead future automotive development

Founded in 1969 as an automatic transmission manufacturer, Aisin AW Co., Ltd. is a subsidiary of Aisin Seiki Co., Ltd. and one of the Aisin Group’s six major companies. Since the development of the 3-speed AT with the front-engine, rear-wheel-drive (FR) layout in 1972, Aisin AW has continued developing products that anticipate market trends. It followed up commercialization of the world’s first FR type 8-speed automatic transmission in 2006 with the world’s first front-engine, front-wheel-drive (FF) layout 8-speed AT in 2012 to help maintain its lead in the industry as the world’s No.1 AT manufacturer.

FY 2016 sales reached 1.2 trillion yen, AT being responsible for 90% of that number. Approximately 38% of the AT units made by Aisin AW go to Toyota Group, and the rest are delivered to more than 50 automobile manufacturers across 15 different countries. In 2012, cumulative production of AT units exceeded 100 million. As the leading global supplier of AT, Aisin AW keeps an eye on next-generation mobility and advances the development of electronics. This effort resulted in the successful mass production of a hybrid system in 2004 ahead of other manufacturers. “We would like to create a vehicle that we can operate almost intuitively and one that inspires the driver.” With such commitment, Aisin AW continues to lead the development of AT to meet and exceed market expectations.

Aisin AW Technical Centre continues developing new-generation technology

The Aisin AW Technical Centre features an innovative manufacturing system that enables smooth information sharing and cooperation among departments in both the Engineering and Manufacturing Engineering Divisions. This new Technical Centre was built in 2011 to integrate all departments engaged in technical development for the commercialization of AT, continuously variable transmissions (CVT) and hybrid transmission units manufactured at different locations. The Centre has approximately 3,000 employees that are committed to increasing technical development capacity through the application of an innovative system that comprehensively integrates all phases of new-product development, from planning through to manufacture. Serving as a facility where Aisin AW can pass its DNA to the next generation of innovators, the Centre sets the goal of maintaining a lively human network for the continued development of new products. The Aisin AW Technical Centre is well prepared for the development of electric vehicles (EVs). According to Shinya Sugiura, General Manager of the Manufacturing Engineering Division’s Tool Engineering Department, “The use of EVs is predicted to grow and countries are preparing for the implementation of tightening regulations around 2020. As a leading automotive parts manufacturer, we are also preparing for this.” Aisin AW has started development of new systems to ensure that it is ready for the emerging era of the EV.

Parts manufacturing sites have as much drama as there are parts

While Aisin AW supplies parts to manufacturers across the globe, the company’s largest single customer is Toyota Group, which accounts for around 40% of total sales. Aisin AW was established as a joint venture between Aisin Seiki and the American automotive parts manufacturer Borg Warner, which is where the “W” in Aisin AW comes from, and the American culture is deeply rooted in the company. Harumichi Nakagawa, Group Manager of Tool Engineering Group 1 in the Manufacturing Engineering Division’s Tool Engineering Department says, “I can still find sizes written in inches in old drawings.”

While the AT is generally unseen by car owners, it is every bit as important as the engine and just as complicated because of the planetary gears that make its smooth operation possible.The three major materials used in the manufacture transmissions are aluminum for the casing, steel for the gears and shafts and cast iron for the oil pump and differential cases. Each has unique characteristics and presents different challenges in manufacturing. Thousands of parts go into each AT unit, and each one is essential in enabling a vehicle to run smoothly and quietly. In the process of manufacturing AT units with such a large number of parts, the highly skilled engineers involved in the design and development of each part find it hard to avoid generating problems for each other from time to time, but it’s the creative energy they have that results in the best product possible. Step-by-step, each AT unit takes form through a painstaking process of production, and there are as many stories that come from the process of development as there are parts developed.

According to Shogo Itoh of the Subsidiary Material Purchasing Group, Material and Equipment Purchasing Department, Purchasing Division, “After the engine, the most expensive part of any car is the transmission. Its function is to connect the engine and the driver; and the more luxurious the vehicle, the more important a quiet ride becomes. AT’s from 20 years ago were a simple 3-speed unit, but now they include up to 8 and even 10 speeds. To fit the gears necessary for this degree of performance in a limited space requires a much higher level of processing accuracy for each part than ever before, and such accuracy requires cutting tools that deliver the highest possible performance and quality.”

The most difficult aspect of AT manufacture is ensuring that all gear teeth meet the strict tolerances determined by the design. To ensure success, AT manufacturers and tool suppliers like Mitsubishi Materials work closely to create new machining methods and develop new cutting tools.

Machining is the final process, and it has a significant influence on fuel efficie

There are many processes in the manufacture of AT units. Shinya Sugiura says, “The machining process is the key because the accuracy of the gear, the heart of the AT, is determined by the cutting process.” If the part is not cut correctly, then the AT fails to achieve its potential. It’s not too much to say that cutting process technology is what makes the manufacture of ATs with new added value possible. “AT performance is determined by the accuracy of the overall machining, and the outcome of this process has significant influence on fuel consumption and quietness,” said Noto Hattori, Team Leader of Tool Engineering Group 1.

Depending on the quality of work materials and the machining required determines the type of tool, heat processing method and type of coating that are to be used. The combinations are infinite. “I feel great pleasure when I find the best combination, and that includes details such as finding the optimum cutting oil. It is often the case that solving just one problem in the machining process increases the overall efficiency of production. There is no doubt that highly advanced machining technology has supported Aisin’s technical development and has maintained the high quality of our products. Advanced machining technology is one of our fundamental assets,” said Shogo Ito.

Large-diameter helical broaches are precision tools often used in AT gear processing. The number of teeth on one broach can number more than a few thousand, but if a defect is found on only one tooth, the product is considered scrap. Hattori says, “When we see a problem, it is absolutely essential to find the cause of the defect.” Nakagawa says, “Being involved in gear cutting, has changed my outlook significantly. I have come to consider the mechanisms behind the phenomena I see in daily life, and this has changed the way I live my life. One of my coworkers liked to collect mini-cars. He carefully observed the size and locations of the engines and transmissions, and considered how he could apply his observations to automotive technology, weight balance and turning performance. It surprised me to see his interest in toys, but it made me realize the importance of considering the reasons for and causes of even a very tiny phenomenon.”

Developing a new large-diameter helical broach with Mitsubishi Materials

The trend of planetary ring processing has been shifting recently from the helical broach method to skiving. Aisin AW did not want to stand idly by and watch their superior processing methods it had developed to become outdated, so it initiated a project in conjunction with Mitsubishi Materials to develop a new type of helical broach. This project sought to drastically improve productivity and reduce costs in ways that could not be achieved by skiving.

Sugiura explains why they chose Mitsubishi Materials as a partner, “Their attitude toward product development was very forward thinking and they were clearly motivated to take part in the development of a new tool. We were very proud to have been a pioneer in the implementation of the American broach in Japan. We felt that developing a new future in cutting utilizing broaches was our mission and that Mitsubishi Materials’ great attitude and quick response would make it the best partner for joint development.”

The joint project for development of the new large-diameter “Innovative Helical Broach” started in 2013. “Mitsubishi Materials let us see details of broach manufacturing that are usually not shared outside the company. We shared information on design and the fundamentals of manufacturing to advance the joint project. We worked hand-in-hand with staff at the Mitsubishi Materials Akashi Plant to reach our goal of finding innovative ways to reduce the cost of AT manufacture. I really appreciated their cooperation and hospitality. ”Engineers from both companies had serious discussions at the Akashi Plant looking over full-scale drawings that measured as much as 2 meters long, and there were times when those discussions became heated debates. In fact, there were disagreements about the best way to proceed from the beginning of the joint project.

“For this project, we used the simultaneous engineering method that we have employed at Aisin AW. We brought in staff who would normally become involved only after the design phase has been completed to participate. It is extremely rare, however, that we employ this method with an external partner. We were hoping that Mitsubishi Materials would work with us on this project like comrades in arms fighting for victory,” said Sugiura. He continued, “The key to achieving high precision was the establishment of measurement technology. We had to surpass the level other manufacturers were capable of achieving and because the relationship between precision and cost involves trade-offs, friction between the parties involved was hard to totally avoid. However, both Mitsubishi Materials and Aisin AW kept at it until they achieved high levels of both.”

Development of the helical broach, an innovation that achieves approximately five-fold greater performance than the existing broach

 

Innovative design, polishing and other concepts were implemented in the development of the new helical broach. The original design concept increases tool life, the polishing concept stabilizes the re-manufacturing process, and the innovative machining technique enhances processing precision. These three concepts resulted in a truly ground-breaking helical broach.

“Although the existing broach only needed to be replaced once a day, this new helical broach lasts for five days. The time and manpower it takes to replace a broach is significant, and meant stopping the production line for around one and a half hours every day. Reducing the frequency of replacement to once every five days improved productivity significantly. It has been said that technical development for skiving has been delayed because of our focus on this innovative helical broach, but I disagree. If the limit of broaching were to remain unchanged, we would not need to set a high goal for skiving. However, because broaching productivity has reached an incredibly high level, we now need to reconsider skiving from the beginning to match the new standard. Helical broach development has had a good influence on in-house operations like this, in fact, it was recognized with the Manufacturing Improvement Award, which is a highly coveted in-house award at Aisin AW,” said Sugiura.

Nakagawa looked back on the process and achievements of helical broach development and said, “Mitsubishi Materials was quick to respond to our requests and questions and welcomed us with open arms at the plant. They were like comrades in our fight to develop leading-edge technology and this gave us a shared a commitment and goal that led to success.”

Both companies learned from each other, reviewed results, supported each other and worked hard together step by step to overcome challenges along the way. Mitsubishi Materials will continue to partner with Aisin AW to support its leading position in the automotive industry and the future of automotive development.