Leveraging a model-based value chain and digital twin to streamline product creation and enhance sustainability

Shaping the future of aviation

Aircraft manufacturers are under intense and continuing pressure to improve fuel efficiency while reducing their environmental impact. This is mainly what drives aircraft engine research and development (R&D).

The innovative solutions of MTU Aero Engines (MTU) have been shaping the aviation industry for more than 85 years. As Germany’s leading aircraft engine manufacturer, they develop, produce and maintain civil and military aircraft engines. As a risk and revenue partner of original equipment manufacturers (OEMs), MTU mainly designs and manufactures components such as high-pressure compressors and turbine center frames as well as assembling complete jet engines.

According to MTU, 30 percent of aircraft in service worldwide have their components on board. MTU is also an independent maintenance supplier, servicing, updating and upgrading both commercial and military aircraft engines.

“Our experts are active in the research, development and realization of innovative engine technologies that will help ensure an emissions-free future for aircraft of all power categories,” says Dr. Stefan Sasse, head of design methods and support at MTU Aero Engines.

Across the various engineering departments, about 600 MTU engineers use Siemens Digital Industries Software’s NX™ software for computer-aided design (CAD) and computer-aided manufacturing (CAM). The company is investigating alternatives to the existing coordinate measurement machine (CMM) solution. For the storage and exchange of all product-related information, MTU relies on a corporation-wide implementation of the Teamcenter® portfolio for product lifecycle management (PLM). NX and Teamcenter are part of the Siemens Xcelerator business platform of software, hardware and services.

Figure 2. The Pratt & Whitney GTF engine family for next-generation commercial aircraft, which contains MTU components, offers double-digit improvements in fuel burn, pollutant and noise emissions, and operating costs. Image: Pratt & Whitney

Incoherent product information

Like all aerospace and defense companies, MTU faces risks due to integrating complex systems and supplier relationships and complying with regulatory requirements. They are also faced with providing maintenance, repair and overhaul (MRO) for extremely long-lived products, some of which were built well before CAD and CAM were even available.

To tackle these challenges and to overcome inefficiencies along the value chain, MTU decided to invest in a digitalization strategy, moving from document-based to model-based methods for systems engineering and production.

Although MTU’s design and manufacturing engineers have been employing 3D modeling for many years, until recently parts manufacturing relied solely on drawings. “Along with separate information silos, this media discontinuity along the value chain was less than user friendly,” Sasse points out. “It hampered product creation efficiency due to many manual transfers of information between systems and was a potential source of errors and misunderstanding.”

Figure 3. MTU turned to model-based definition methods, augmenting the 3D models with other information traditionally noted on the drawings. As a proof of concept, they built the framework and finished one design, a bladed integrated disk.

A model-based value chain

This prompted MTU management to turn to model-based definition, augmenting the 3D models with other information traditionally noted on the drawings. This meant completing the digital twin of each component within one file to weave a digital thread throughout the value chain, from design to manufacturing and quality assurance, including MRO. The aim was to eliminate 2D drawings.

“Our approach goes beyond a model-based definition,” Sasse stresses. “We implemented a model-based enterprise using Siemens software across MTU from the very beginning of product ideation to MRO, feeding back usage and condition information.” This means replacing drawings with intelligent 3D models of components and assemblies with embedded product and manufacturing information (PMI) that constitutes a single source of truth throughout the company and its partner ecosystem.

MTU design and manufacturing engineers started the conversion project by analyzing the existing information required for downstream processes in the product definition, and their various lifecycles within the product lifecycle. They also evaluated the existing software’s capabilities to accommodate geometric dimensions and tolerances (GD&T), 3D annotation (text) and dimensions, surface finish and material specifications. These were inherently present in NX and Teamcenter but not yet developed to the current extent. “This was no substantial obstacle,” recalls Robert Kloeppner, CAD/PLM methods developer and MBD/MBE project lead at MTU. “We saw that Siemens continually extended these capabilities, and current versions of NX and Teamcenter come with best-in-class broad PMI capabilities.”

“Building the product information Autobahn for a value chain as complex as ours is a project spanning many years,” states Sasse. “We formed a dedicated CAD/PLM methods design team to tackle it.” Prior to implementing anything in software, these MTU experts developed and tested rules and methods for model-based definition (MBD) to provide a better interface with manufacturing and quality assurance. The PMIs carry information along all stages of the value chain, so the MTU engineers also evaluated all downstream processes to determine the best use of PMIs.

Figure 4. The PMIs lock on to the boundary representation geometry of the 3D model. The result can be exported in JT or STEP file formats for easy use in manufacturing, quality assurance or other downstream activities.

Dynamically replacing drawings

Using NX and Teamcenter, the team creating a framework for a comprehensive digital twin of all products and processes. This product master model provides rules and processes for product definition and comes with the product’s geometric model and various sets of PMIs for all downstream uses. The product master model also includes rules for Teamcenter so it can automatically supply all required information in the appropriate form all along the value chain.

“As different parts of the overall data have different lifespans, we need to ensure individual pieces of information can be added or modified over the often decades-long lifecycle of an aircraft engine without rectifying the entire design,” says Kloeppner. “We make sure that in our implementations, PMIs can be handled in NX as well as Teamcenter.” When a change is made in NX or Teamcenter, it is reflected in the other.

“Drawing a digital thread along the entire lifecycle, from ideation and manufacturing to its service life, facilitates full information transparency using concise data to streamline the processes,” says Kloeppner. “This reduces manual interaction with the data and potentially reduces repetitive work, human mistakes, time-to-market and expenditures.”

MTU engineers not only augmented the 3D models with PMIs, but they also used NX conditional logic statements to build them so faces of the models of the PMIs would be associated with colors. This reduces time for searches. It eases and accelerates reading and interpreting the information and helps eliminate mistakes. Since they are embedded in several instances of closed-loop design and manufacturing along the value chain, the augmented NX models are also used to identify manufacturing savings, such as optimizing individual tolerances to meet the required tolerance distribution of the manufactured part.

Figure 5. The augmented NX models capture the collected experience of many design, manufacturing and quality engineers. Their faces come in various colors associated with the PMIs. This reduces time for searches, eases and accelerates reading and interpreting the information and helps eliminate human mistakes.

Reducing time-to-market

However, according to Kloeppner, replacing documents with data that is readable by machines as well as humans is only one of several achievements. “The augmented NX models capture the collected experience of many design, manufacturing and quality engineers in a way that colleagues can leverage in later designs without the need for information archaeology,” he emphasizes. “This helps us streamline product creation and reduce time-to-market.”

It enables MTU to more effectively manage increasingly complex product requirements, development and overall integration of their design, analysis, validation and verification activities. This helps them achieve optimized designs, avoid surprises and reduce cost impact from changes by identifying and addressing issues early. Closed-loop collaboration inside the team and with key suppliers helps reduce costs of verification, documentation and compliance with end-to-end traceability.

However, this transformation did not come about quickly. The process has been underway for several years. “In close cooperation with the Fraunhofer Institute for Production Technology, we built the framework and finished one design, a Blade Integrated Disk and a compressor module as a proof of concept, and plan to go live and roll out the methods by early 2025,” reports Kloeppner. “Currently, we are on a steep slope along a learning curve that is part of a lengthy journey that is unlikely to terminate anytime soon.”

Figure 6. PMIs embedded in the NX models are machine readable so they help accelerate the creation of NC programs creation using NX CAM.