A new CAD/CAM/CAE integration approach to modelling flutes of solid end-mills

Milling is used widely as an efficient machining process in a variety of industrial applications, such as the complex surface machining and removing large amounts of material. Flutes make up the main part of the solid end-mill, which can significantly affect the tool’s life and machining quality in milling processes. The traditional method for end-mill flutes design is using try-errors based on cutting experiments with various flute parameters which is time- and resources-consuming. Hence, modeling the flutes of end-mill and simulating the cutting processes are crucial to improve the efficiency of end-mill design. Generally, in industry, the flutes are ground by CNC grinding machines via setting the position and orientation of grinding wheel to guarantee the designed flute parameters including rake angle, relief angle, flute angle and core radius. However, in previous researches, the designed flute profile was ground via building a specific grinding wheel with a free-form profile in in the grinding processes. And the free-form grinding wheel will greatly increase the manufacturing cost, which is too complicated to implement in practice. In this research, the flute-grinding processes were developed with standard grinding wheel via 2-axis or 5-axis CNC grinding operations. For the 2-axis CNC flute-grinding processes, the flute was modelled via calculating the contact line between the grinding wheel and cutters. The flute parameters in terms of the dimension and configuration of grinding wheel were expressed explicitly, which can be used to planning the CNC programming. For the 5-axis CNC flute-grinding processes, the flute was obtained with a cylinder grinding wheel via setting the wheel’s position and orientation rather than dressing the dimension of grinding wheel. In this processes, optimization method was used to determine the wheel’s position and orientation and evaluating the machined flute parameters. Beside, based on the proposed flute model, various conditions for grinding wheel’s setting were discussed to avoid interference of flute profile. A free-form flute profile is consequently generated in its grinding processes. However, in the end-mill design, the flute profile is simplified with some arcs and lines to approximate the CAD model of end-mills, which would introduce errors in the simulation of cutting processes. Based on the proposed flute-grinding methods, a solid flute CAD model was built and a CAD/CAM/CAE integration approach for the end-mill was carried out to predict the cutting forces and tool deflection. And also, the prediction results with various methods are verified to demonstrate the advantage of proposed approach. This work lays a foundation of integration of CAD/CAM/CAE for the end-mill design and would benefit the industry efficiently

Simulation of a finishing operation : milling of a turbine blade and influence of damping

Milling is used to create very complex geometries and thin parts, such as turbine blades. Irreversible geometric defects may appear during finishing operations when a high surface quality is expected. Relative vibrations between the tool and the workpiece must be as small as possible, while tool/workpiece interactions can be highly non-linear. A general virtual machining approach is presented and illustrated. It takes into account the relative motion and vibrations of the tool and the workpiece. Both deformations of the tool and the workpiece are taken into account. This allows predictive simulations in the time domain. As an example the effect of damping on the behavior during machining of one of the 56 blades of a turbine disk is analysed in order to illustrate the approach potential

Simulation of a finishing operation : milling of a turbine blade and influence of damping

Milling is used to create very complex geometries and thin parts, such as turbine blades. Irreversible geometric defects may appear during finishing operations when a high surface quality is expected. Relative vibrations between the tool and the workpiece must be as small as possible, while tool/workpiece interactions can be highly non-linear. A general virtual machining approach is presented and illustrated. It takes into account the relative motion and vibrations of the tool and the workpiece. Both deformations of the tool and the workpiece are taken into account. This allows predictive simulations in the time domain. As an example the effect of damping on the behavior during machining of one of the 56 blades of a turbine disk is analysed in order to illustrate the approach potential

Improving Stability Prediction in Peripheral Milling of Al7075T6

Chatter is an old enemy to machinists but, even today, is far from being defeated. Current requirements around aerospace components call for stronger and thinner workpieces which are more prone to vibrations. This study presents the stability analysis for a single degree of freedom down-milling operation in a thin-walled workpiece. The stability charts were computed by means of the enhanced multistage homotopy perturbation (EMHP) method, which includes the helix angle but also, most importantly, the runout and cutting speed effects. Our experimental validation shows the importance of this kind of analysis through a comparison with a common analysis without them, especially when machining aluminum alloys. The proposed analysis demands more computation time, since it includes the calculation of cutting forces for each combination of axial depth of cut and spindle speed. This EMHP algorithm is compared with the semi-discretization, Chebyshev collocation, and full-discretization methods in terms of convergence and computation efficiency, and ultimately proves to be the most efficient method among the ones studied.The authors wish to acknowledge the financial support received from HAZITEK program, from the Department of Economic Development and Infrastructures of the Basque Government and from FEDER funds. Additional support was provided by the Tecnologico de Monterrey, through the Research Group in Nanomaterials and Devices Design

Application of the stability lobes theory to milling of thin workpieces, experimental approach

The optimisation of cutting conditions in High Speed Machining (HSM) requires the use of a vibratory approach in order to avoid a fast deterioration of the tool and of the spindle, as well as a loss of quality of the surface rough- ness. We suggest a transposition of the method of stability lobes to the case of the milling thin parts, which is very typical from the aeronautical manufacturing context. After having modelled the dynamic behaviour of a blade and of the cutting efforts in side milling, we describe the zones of machining instability. An experimental validation permits us to emphasise the transition from stability to instability, in accordance to our theoretical results. The experimental profile is then compared with a computed profile. A decomposition of the different situations of contact between the tool and the part permits to show the influence of back cutting in the model. Tests of machining permit then to quantify its role. The objective of these works is the definition of a quick methodology for deter- mining the optimal cutting conditions in a given industrial machining configuration

Part Repair using a Hybrid Manufacturing System

Nowadays, part repair technology is gaining more interest from military and industries due to the benefit of cost reducing as well as time and energy saving. Traditionally, part repair is done in the repair department using welding process. The limitations of the traditional welding process are becoming more and more noticeable when the accuracy and reliability are required. Part repair process has been developed utilizing a hybrid manufacturing system, in which the laser aided deposition and CNC cutting processes are integrated. Part repair software is developed in order to facilitate the users. The system and the software elevate the repair process to the next level, in which the accuracy, reliability, and efficiency can be achieved. The concept of repair process is presented in this paper. Verification and experimental results are also discussed.Mechanical Engineerin

Design of a five-axis ultra-precision micro-milling machine—UltraMill. Part 2: Integrated dynamic modelling, design optimisation and analysis

Using computer models to predict the dynamic performance of ultra-precision machine tools can help manufacturers to substantially reduce the lead time and cost of developing new machines. However, the use of electronic drives on such machines is becoming widespread, the machine dynamic performance depending not only on the mechanical structure and components but also on the control system and electronic drives. Bench-top ultra-precision machine tools are highly desirable for the micro-manufacturing of high-accuracy micro-mechanical components. However, the development is still at the nascent stage and hence lacks standardised guidelines. Part 2 of this two-part paper proposes an integrated approach, which permits analysis and optimisation of the entire machine dynamic performance at the early design stage. Based on the proposed approach, the modelling and simulation process of a novel five-axis bench-top ultra-precision micro-milling machine tool—UltraMill—is presented. The modelling and simulation cover the dynamics of the machine structure, the moving components, the control system and the machining process and are used to predict the entire machine performance of two typical configurations

On the stability of high-speed milling with spindle speed variation

Spindle speed variation is a well-known technique to suppress regenerative machine tool vibrations, but it is usually considered to be effective only for low spindle speeds. In this paper, the effect of spindle speed variation is analyzed in the high-speed domain for spindle speeds corresponding to the first flip (period doubling) and to the first Hopf lobes. The optimal amplitudes and frequencies of the speed modulations are computed using the semidiscre- tization method. It is shown that period doubling chatter can effectively be suppressed by spindle speed variation, although, the technique is not effective for the quasiperiodic chatter above the Hopf lobe. The results are verified by cutting tests. Some special cases are also discussed where the practical behavior of the system differs from the predicted one in some ways. For these cases, it is pointed out that the concept of stability is understood on the scale of the principal period of the system—that is, the speed modulation period for variable spindle speed machining and the tooth passing period for constant spindle speed machining

E -commerce for the metal removal industry

The popularity of outsourcing fabrication introduces a problem, namely an inevitable loss of data as information is translated from design to fabrication or from one system to another. Unsatisfactory information, delivered to the outsourcing facility, and inefficient communications between design and fabrication certainly cause enormous economic losses from late product delivery or bad product quality. To overcome these data transferring problems and to improve communications between the design and fabrication sides, a design and manufacturing methodology for custom machined parts in E-Commerce is suggested and implemented in this dissertation. This methodology is based on the idea of a Clean Interface like the Mead-Conway approach for VLSI chip fabrication [MEAD81]. Essential design information for fabricating parts properly with NC (Numerical Controlled) milling machines is expressed in machining/manufacturing features, fabrication friendly terminologies, and is represented by a new language called NCML (Numerical Control Markup Language). NCML is based on XML (Extensible Markup Language)---the document-processing standard proposed by the World Wide Web Consortium (W3C). NCML is designed to include the minimum requisite information necessary for the manufacturer to produce the product. The designer defines NCML, which overcomes geographical separation between design and manufacturing, and minimizes unnecessary interactions caused from lack of information. To prove the possibility of custom machine part fabrication and E-Commerce with NCML, three software systems are implemented. These three systems are FACILE/Design, FACILE/Fabricate, and E-Mill. FACILE is a prototype CAD/CAM system developed to verify NCML feasibility as an Electronic Data Interchange (EDI) format. FACILE/Design is a system based on manufacturing features like holes, contours, and pockets. It can be used to create geometric models, verify the design, and create NCML files. The NCML file is imported by FACILE/Fabricate and turned into G-codes by applying appropriate cutting conditions. Simplified machining simulation and cost estimation tools using NCML inputs are also developed to show some examples of NCML applications that can help design and manufacturing activities. To demonstrate how NCML could be used in a web-based application, an E-Business model called E-Mill has been implemented. E-Mill is a market place for machined parts whose data is encoded in NCML. To make E-Mill a feasible E-Commerce model, two-way communication based on NCML data and the visualization of 3D geometric models in the Virtual Reality Modeling Language (VRML) are equipped with a competitive matchmaking mechanism. In this dissertation, a whole system based on NCML bridges the gap between design and manufacturing. As a part of the NCML validation process for the new system, the pros and cons of NCML design features are discussed. A system for cost estimation is calibrated and compared to real cutting results for the purpose of validation