MMC Magazine

PRÄZISIONSWERKSTÄTTEN (PRECISION WORKSHOP)

DR. -ING. HEINZ-RUDOLF JUNG GMBH & CO. KG
75 YEARS OF CUTTING-EDGE MANUFACTURING AND MACHINING TECHNOLOGY

INTRODUCTION

PRÄWEST is a group of companies manufacturing specialised parts up to a diameter of 2500 mm, including a wide variety of turbines, static parts and casings used over a wide range of industries ranging from aerospace through to heavy plant. The company is equipped with modern machine tools and applies the latest cutting technology to ensure the highest quality components and assemblies, whilst also continuously monitoring emerging trends such as additive manufacturing.

Over the last years, complex applications that require high precision machining of difficult-to-cut materials for components with strict regulatory and technical standards have become part of the company’s daily business. For applications where the in-house tooling solutions don’t reach the anticipated results, the company seeks advice from tool manufacturers to benefit from their expertise.

This editorial casts a retrospective glance at the company’s history and illustrates the partnership between Präwest and Mitsubishi Materials over the last decade.

Foundation of Quality

Präwest was founded by an aerospace industry expert, Mr. Heinz Hampel in Bremen, Germany in 1945 after the end of World War II. Due to the turbulent post-war period that led to government restraints on aircraft manufacturing, the company started operations with special machining applications for the tobacco industry. Two years later the company returned to the roots of its founder and concentrated its activities on the machining of aerospace parts.

From the onset, Präwest focused on product quality and the company soon established itself in the civil aviation business in Germany. Until the late 1970s the company, even with as few as 25 employees, experienced steady output growth and flourished as a small but highly specialised workshop for machining aerospace parts. However, in the early 1980s the business was acquired by Dr.-Ing. Heinz-Rudolf Jung who was to lead the company to its next level.

Building on the company’s good reputation, the new, visionary owner focused on technology setting new strategic objectives. These included further expansion of the company into the aerospace industry, but more importantly a diversification of operations into other business areas, such as automotive, oil and gas and energy, but with the emphasis remaining firmly on quality.

The diversification enabled the company not only to explore and develop new business opportunities but also leverage its technological competencies, by strengthening and modernising its aerospace business. Präwest was one of the first companies to introduce and deploy simultaneous 5-axis CNC machining in Germany, and thereby achieved higher accuracy and performance for special components and niche products. What once started as a local small-sized company upon the initiative of one man, soon developed into the modern international company that it is today.

Adapt and Specialise

Today, Präwest is a tier 1 supplier to major OEMs worldwide and comprises of three independent entities: PRÄWEST, specialised in machining of large, heavy-weight parts; PRAE-AERO founded in 2015 in Lower Saxony, dedicated to mass production processing of smaller parts for the aerospace sector; and CHAMPION PRECISION, founded as a joint venture in 2017 in China for selected niche products.

The Präwest group confidently meets new machining challenges with a committed development team and a state-of-the-art machine park with over 130 CNC machines and 24 robots. The diversification of the company becomes evident by the number and versatility of different products machined in each company. These include parts for aerospace, turbines, organic rankine cycle systems, turbo charger compressors & turbine wheels, vacuum technology systems as well as for the energy, oil & gas industries.

Machining requirements with regards to materials, shapes, sizes and geometries have changed drastically over the past few decades, therefore flexibility and adaptability play a pivotal role for manufacturing companies. What seems revolutionary and profitable today may soon become obsolete. This is especially prevalent in the aerospace sector where the latest big step change in technology has been already realised with the launch of advanced fuel efficient aircraft engines such as the Rolls Royce Trent series, the GE-9X and the Pratt & Whitney GP and PW1100G series which is one of the two engine options for A320neo.

This advancement meant specialisation in product niches became essential. Reiner Wahlers, managing director of Präwest says about the market development: “The industry landscape is constantly evolving in a 5 to 10-year cycle. If we want to keep pace and remain competitive, we must change too. Whereas ten years ago, aluminium structural parts such as wing spars, flaps and airframes dominated our operations, today, we are fully specialised in engine parts, including both gas flow parts and casings.”

Machining specialised aerospace parts such as blisks, blades, vane clusters, impellers or rings and discs are problematic for many manufacturers. The challenge lies primarily in the nature of the raw materials, which are difficult to machine. Titanium alloys, Inconel, nickel and cobalt based alloys as well as stainless steels and other heat resistant alloys are some of the most common materials used for such components. These materials are also the ones that Präwest possesses highest expertise in machining. Consequently, when it comes to acquiring new customer projects, three elements influence the company’s decision: Applications in difficult to machine materials; applications with complex geometries; and applications with the ability to reach a certain level of automation. Dr. Benjamin O’Shea, managing director of Präwest, confirms: “If two out of the three criteria are fulfilled in the customer’s request, it is most probably an attractive project for us and a contract that we want to win.”

Präwest not only has its own high-tech workshop but also a tool grinding facility and a quality assurance department. With a total of twelve CNC grinding machines, plus a new ERPsystem for automated tool registration and an advanced CAD/CAM software, the Präwest Group is fully equipped to design and manufacture customised cutting tools. For aerospace applications where highest precision serial production with high level of automation　is required, the tool pre-setting, optical surface measurement and calibration processes are carried out digitally, directly on the machine. Christian Hoppe, head of the tool development department, says: “We have established certain workflows linked to our tool database, enabling secure transmission of tool geometries, pre-setting data and re-grinding information, so we can quickly upload all needed tool information to the machines.”

Latest Technology

Cooperation and co-engineering with other industry professionals play a fundamental role for the company’s success. Mitsubishi Materials is one of the cutting tool suppliers Präwest has partnered with to improve its production efficiency and optimise the machining process of parts such as vane clusters and blisks.

It was 2014 when the iMX high feed head end mill series with exchangeable heads was introduced to Präwest by Wolfgang Schmidt, sales representative at MMC Hartmetall GmbH, the European Headquarters of Mitsubishi Materials, as the ideal solution for the machining of clusters. Mr. Hoppe remembers: “We were unsatisfied with the performance of the in-house tooling. Additionally, the machining strategy, which was mainly trochoidal milling, clearly didn’t live up to our expectations to machine the narrow channels within titanium vane clusters and be able to leave the minimum material for finishing. When the iMX series outperformed every other tested cutting tool, as well as optimising the overall machining process, we realised that this tool would soon be our first choice not only for the machining of the clusters but also for other applications with similar machining strategies and parameters.”

The iMX series is the screw in head end mill system from Mitsubishi Materials that combines the advantages of both solid carbide and indexable insert end mills. This is made possible because the taper and end clamping faces of the head and the holder are both solid carbide – only the threaded part is composed of steel. This provides accuracy of the carbide clamping faces when a change of head is needed, whilst the benefits of a steel thread embedded in the carbide head and holder, over a purely carbide thread also adds reliability and strength.

Mr. Schmidt says: “After analysing Präwest’s initial requirements, it became clear that the exchangeable heads of the iMX series would be ideal. Additionally, the wide range of different types of geometries and long reach shanks available meant that these tools could effectively and reliably machine the complex shapes and materials specified by Präwest’s engineers. The first diameters tested were the 10, 16 and 20 corner radius types and it was found they could machine very close to the final nett shape. This provided a time saving when compared to other solutions because there was no longer a semi-finishing step needed.”

Whereas for many manufacturing companies reducing machining time is decisive for the selection of cutting tools, Präwest focuses on process stability and reliability as well as cost-efficiency. Mr. Wahlers says:” We don’t look for the fastest way to machine a part. It’s the total process cost that is important to us, therefore we gladly consider tool recommendations from Mitsubishi Materials and other tool manufacturers. We need to be confident that every single time, the part will come off the machine exactly the way it should be. That was the case with the iMX.” Today, Präwest utilises the iMX series for the manufacture of vane clusters in four 5-axis CNC milling machines in four different stages, producing over 1000 clusters yearly. The iMX series has also been introduced on the serial production process of the blisk and other applications with similar machining strategies.

Re-grinding

The cooperation between Präwest and Mitsubishi Materials goes back many years starting with the supply of VP10RT grade turning inserts. However, the introduction of the iMX was a milestone in the longstanding partnership, which now reaches beyond the usual customer-supplier relationship. Mitsubishi Materials follows Präwest’s development steps, standing by to assist, consult and train their highly skilled team. Cost-efficiency is particularly important and influences the company’s purchasing behaviour towards other manufacturer’s cutting tools. Mr. Hoppe says: “Every time we calculate the total process cost of an application, the cost for the cutting tools is a major factor, but, our ability to successfully re-grind tools in-house without unnecessary logistical delays offsets the initial cost and is one of our competitive advantages. After professional re-grinding training by the experts of Mitsubishi Materials, the iMX cutters met our expectations in this aspect too.”

Re-grinding high feed precision carbide tools with geometrically complex cutting edges such as the iMX series is challenging. The tool can drastically lose performance if the edge shape and overall dimensional tolerances are not met after grinding. This can result in loss of tool life and can create the potential to scrap the expensive raw material. Therefore, Mitsubishi Materials gladly agreed to provide grinding machine programmes and trained Präwest how to grind the iMX cutters. This was carried out by a member of the iMX development team, Takayuki Azegami. He is a product design engineer for aerospace applications at the European Headquarters of Mitsubishi Materials,and says: “When I first visited Präwest’s re-grinding facilities for the training, any concern I might have had was immediately eliminated. Looking at the highly skilled staff and the state-of-theart equipment that uses end-to-end automation to prevent human errors, I was confident about the success of the re-grinding project. Furthermore, it gave me great satisfaction to observe a tool that I had helped create, being involved in high level machining at one of our international customers.”

Continued Cooperation

The successful implementation of the iMX series strengthened the partnership between the two companies and opened new avenues of cooperation. With the recently founded solutions centre, MTEC Stuttgart (Mitsubishi Materials Technology & Education Centre), Mitsubishi Materials can now provide Präwest with an advanced facility and the engineering know-how for their cutting tests. This will further enhance open innovation and co-development.

One of the future projects is an application of a semi roughing pocket milling in a stainless steel component, with a tool overhang length up to 180 mm. Mr. Wahlers says: “It is the first time we trust a partner with a cutting trial. In the past, we relied on our own means and expertise, but our positive experience of the collaboration with Mitsubishi Materials brought the benefits of such a partnership to the forefront.

Synergies with financial benefits in the metalworking industry are not rare, but when it comes to building new partnerships, other values matter. While often luck plays an unquestionable role at the start of a partnership, namely offering the right technology at the right time and place, factors such as open communication, information sharing, trust and commitment influence the quality and future of the business relationship. Dr. O’Shea concludes:” Quality has always been one of Präwest’s fundamental principles over the past 75 years. The anticipated high quality is also reflected in the products and services of Mitsubishi Materials. Acting more as a cutting-edge technology partner rather than a purely sales focused company is what we value most in this partnership.”

About the future cooperation and further business support for Präwest, Akihiro Kittaka, team member of the business strategy department of Mitsubishi Materials in Japan, says: “Mitsubishi Materials is a global player in the cutting tools sector and operates worldwide for international customers. Following Präwest’s recent expansion in China we are pleased to have the opportunity to create bridges between existing technologies and applications and support our customer’s new and future business operations in Asia, and of course with the same high-quality standard as in Europe.”