An Engineering Pedagogy for Developing Practical Knowledge and Hands-On Skills Related to 5-Axis Milling and Computer-Aided Aerospace Parts Manufacturing Using Current Technology

The implementation and effective utilization of advanced computer controlled machines and processes depends on a concerted effort by industry, machine and software vendors, and educators. Specialized and multipurpose machines such as 5-axis mills, turn-mill, and Swiss style lathes are becoming more popular and affordable. Furthermore, their controllers are becoming more versatile and integrated with sensors, probing capabilities, data collection and enterprise level software. Although trade schools do a good job at training operators and CAD/CAM technicians, there is a growing need for mechanical, manufacturing, and aerospace engineering graduates to have experience and a working knowledge of all aspects of component design, process planning, CNC programming, and process improvement so that companies realize a competitive edge from their investments. This is especially true in the aerospace industry, where factors such as part geometry complexity, difficult to machine materials, single setup fixture design, computer simulations, and reduced cycle times through optimization determine the difference between potential and realized gains in capability and efficiency. In this paper, the authors present a set of course modules that address some of the challenges mentioned above and propose a low-cost platform (hardware/software/tutorials) for other educators to get started. As Industry 4.0, the IIoT, Human Machine Interfaces (HMI’s), and Machine Control Units (MCU’s) become more sophisticated, the need for skilled personnel and good pedagogical tools will grow as well. Finally, the authors developed some tools to evaluate the effectiveness of the modules and gather feedback from students for future improvements. Introduction and Background Advances in machine tool technology, CAD/CAM integration, 3D Printing, and Industry 4.0 initiatives are forcing manufacturers across the board to reflect and reevaluate how they design and implement components and assemblies of all kinds. Because of the nature of aerospace parts in general (geometric complexity, tight tolerances, and hard materials) as well as strict industry and FAA guidelines, the use of multi-purpose and multi-axis machines and specialized cutting tools along with the ability to inspect parts right on the machine are a necessity. There is a need for more practical and current educational materials that address this paradigm shift toward designing, programming, and producing these parts using current technologies and skilled personnel at all levels (i.e. operators, process planners, programmers, and Figure 1: Spider Chart Showing 5-Axis Growth in Diverse Industries engineers). The expected growth in one particular area (5-Axis machining) across many industries is well documented and shown in the chart above taken from a National Tooling and Machining Association webinar titled: “Main Strategies for Effective Implementation of 5-Axis in Different Areas” shown in Figure 1. [1] This paper focuses on improving engineering education. Students completing a traditional B.S. or dual degree in Mechanical Engineering and Manufacturing Technology provide an excellent audience to explore the challenges and opportunities related to designing and making aerospace parts. With the growing prevalence of 5-Axis and multi-purpose CNC equipment, it is inevitable that the way we think about parts will also experience a sort of revolution in the upcoming decade. The idea is to target students that already have basic CAD/CAM and 3-axis CNC knowledge and extend that to the application and theory of 5-axis machining. Utilizing a 5-Axis table-top mill Pocket NC and a 3D modeling and manufacturing software Fusion 360, the authors have developed modules for students in the advanced CAM class to teach the theory, applications, and practice of 5-Axis. The didactical nature of the machine (i.e. low risk) and the availability of the software selected makes it a great place to start and is readily transferrable to other colleges/programs that are interested in learning about this exciting technology. The goal is to expose students to both higher levels of design and critical thinking abilities. Other skills pertinent to 5-Axis machining that are covered include Design for Manufacturability (DFM), cutting tools, CAM software mastery, simulators, code reading, and communication with operators. The results will help to identify which tools are effective and which are not for introducing 5-axis, as well as for establishing a roadmap to future enhancements. Literature Review One of the recurring themes in researching 5-axis machining is that this technology is often being utilized below its potential [2]. 5-axis, in many situations, is used in the same way that 3axis technology is used. This can be the case in 3+2 [3] machining where rotational movements only occur between operations to position the part and the actual machining operation is a standard 3-axis machining process. This process can be inefficient from a cycle time perspective. While using 3+2 machining does save time and allows for higher quality parts as compared to traditional 3-axis manufacturing it may not utilize the full potential of the technology. It should be remembered however that at times 3+2 machining can be more optimal than 5-axis by allowing for better part quality. This is dependent on the machine itself, tools available and the nature of the operation performed [4]. Some of the challenges inherent in 5-axis machining are tool collisions, surface finish and tool path optimization. This last challenge is especially important as finding the most efficient machining method can be very difficult given the extreme level of flexibility offered by the technology [4]. This problem of flexibility is not limited merely to 5-axis systems but is an issue faced by CNC machining in general. Even something as simple as using different CAM systems to process operations can result in different cycle times and based on how each system develops its machining strategy [5]. Another important area of research in this field is the study of how to minimize errors due to thin part deflection and vibration. Given the fact that aerospace part machining frequently involves thin bladed parts with high tolerance requirements this is an especially critical field of study. To control the forces that might deflect and deform parts causing defects, studies using finite element analysis and tool orientation optimization have been performed with favorable results [6]. In addition to reducing defects, research is also being undertaken to find more efficient tool path methodologies by determining the ideal tool path layers and flow line arraignment in order to reduce machining waste [7]. In educating students on multi-axis machining principles, an emphasis has been on being able to provide students with improved opportunities to simulate machining operations in a low risk environment. This can be performed through the use of various CAD/CAM software such as SOLIDWorks or Vericut that allow students to simulate operations and perform activities such as tool path and machining time optimization [8]. Statement of Need for Engineering Education Related to 5-Axis for Aerospace Parts From large parts like fuselage sections and bulkheads, to medium sized parts like wing spars and landing gear, to small components and molded parts typical in the aerospace and airline industry, there are common factors that distinguish them from other types of parts. Starting with stock shapes and materials (forgings, castings, roughed out and work-hardened), cumbersome setups and fixture design, high strength, low weight, curved shapes, high tolerances, features located normal to surfaces, long and robust tools for cutting, and clearance space in the work envelope are some of the most commonly identified challenges for machining aerospace parts [9]. These and other issues like machine kinematics, analysis of forces on cutting tools/machine components, and optimization of material removal rates are analytically beyond the scope of training for students with a limited math, physics, materials, and machine design background. “Considering angular limits with different setups is important. When you’re dealing with five different axes of movement, the machine can get wrapped around itself when trying to get into various nooks and crannies of those odd-shaped parts. Determining what kinds of angular limits the machine has is key to making your rapids as fast as possible if your machine needs to unravel itself from a weird angle on a part, that is all off-part motion.”[10]. New technology is also influencing the growth of 5-Axis in the aerospace industry. “Machine tool makers and their technology partners are developing solutions to help, including easier-touse controls and programming complex cuts with support graphics and dynamic collision monitoring (including touchscreen). Machines that easily and efficiently feed data to enterprise systems and machine monitoring programs can offer visibility and analysis to increase competitiveness and profitability. Aerospace has increasingly stringent demands: consistently high surface quality, reliable compliance with tight tolerances, high machining speeds, and documentation/validation of processes accompanying production” [11]. Mastering the art of 5axis necessitates taking a host of factors into account. Although 5 -axis machining has been around for a while, it is experiencing new popularity, particularly in aerospace and defense applications. These markets are experience significant growth. For example, the commercial aircraft order backlog is at its peak of more than 14,000—with about 38,000 aircraft expected to be produced globally over the next 20 years. “When you look at problems that customers have, very seldom is it machining a part. Typically, the problem that’s holding them back is centered around something other than making a chip. I