Integrated design and manufacturing system for blades mould.

Udroiu, Razvan

1. INTRODUCTION

Most discrete parts are manufacturing by using a near net shape process NNS (Machover, 1996) such as forging, die casting, stamping, injection moulding or autoclave moulding. These processes use die and moulds to impart the NNS geometry on an incoming shapeless material or a preformed work piece. The material that the parts are from can be metal, polymeric or composite. The production of complex parts from composites materials corresponds to a long manufacturing process compared to a mechanical part obtained by chip removing machining. The manufacturing process of complex parts from composites materials is characterized by three design functions: the design of external shape of finished part, the design of internal structure of composite part and the definition of bond tool or mould, and two manufacturing functions: the mould machining and the production composite parts. A helicopter blade is a complex part made of composite materials. In this work the focus is on the design of external shape of the helicopter blade, definition of the mould and mould machining.

2. FEATURES AS INOVATIVE ELEMENTS LINKING DESIGN AND MANUFACTURING

Actual production of mechanical parts is diversified the slogan being higher quality product obtains cheaper and without pollution the nature. In the same time the concurrence at the market place is better. These things claim with acuteness to enhancing the companies' competitiveness by cutting the product-development time, reducing the time-to-market and improving the quality of design using CAD/CAM/CAPP/CAE systems integrated in concurrent engineering philosophy. Concurrent engineering helps bring higher-quality products to market faster and a less cost by involving all the players, including customers and suppliers, at the earliest stage possible.

During the design process, different engineers take information about the design, and manipulate it in order to generate the new information required for the development of the new product. Various engineering representations of the designed product are created and used for different engineering tasks. These represent, for example, a manufacturing engineering viewpoint, a structural analysis viewpoint, a process engineering viewpoint, and so on (Lee et al., 2003).

[FIGURE 1 OMITTED]

Feature technology, is expected to be able to provide for an adequate basis for the integration of design and the subsequent applications such as engineering analysis, process planning, machining and inspection. Features may be generated in three distinct ways (Udroiu, 2003), (Ibrahim & McCormack, 2005), known as "feature recognition", "design with features" and "interactive feature definition/ identification".

Currently, three main views are discerned on how to obtain application features, such as manufacturing features, analysis and inspection features, from a product model. Today, the focus is on the integration of feature based design with feature based manufacturing. In (Chen et al., 2007) the machining feature model of a design part, needs to be built from the design feature model of the part during its design process and automatically adjustable to maintain the consistency of these two models.

In this work I proposed two features models to design a helicopter blade mould: the model of the helicopter blade based on design features and the model of helicopter blade mould based on "constructive-technological features" (CTF), fig.1. CTF wants to help the CAD/ CAPP/ CAM integration in an innovative way. It is proposed the following definition for CTF: "a constructive-technological feature is a geometric shape that has attached several minimal geometrical configurations for milling (MGCM) for each manufacturing operation (roughing, semi-finishing, finishing, rest-material) and a set of information regarding the cutting process, like as cutting strategy, NC files, etc". The concept of minimal machining configuration (Mawussi et al., 2000) for prismatic machining (MMC) and later MGCM (Udroiu, 2003) for complexes parts allow in the context of integrated design, to inform the designer about the machining ability of the part from a cutting tool point of view or allow to inform automatically the NC engineer about the optimal cutting tools use for machining a feature of a part. In the same way the fact that a feature can be machined only with one MGCM whose cutting tool is relatively expensive makes it possible draw the attention of the designer to the portions of the part which increase the total machining cost.

3. INTEGRATED CAD/CAM SYSTEM THE CORE OF CONCURRENT ENGINEERING

The work presented in this paper falls under the step of integrated engineering. The purpose is principally the development of an integrated design and manufacturing system for helicopter blade.

The software resources of system proposed is composed from the software packages realized by the author, some CAD/CAM commercial software and software resource of NovaMill CNC machine.

[FIGURE 2 OMITTED]

The innovative software packages proposes in this paper are the following: PACPE (Computer Aided Design of Helicopter Blade), PACAPE (Computer Aided Design of Helicopter Blade Mould), DACRAF (Computer aided establish of cutting parameters concerning complex surface milling) and ECU-Virtual (Complex Milling Features--Virtual). PACPE and PACAPE are written in Visual Lisp and Dialog Control Language programming language and are implemented in Autodesk Mechanical Desktop. DACRAF and ECU-Virtual are written in Visual Basic programming language and can be added like add-in application to commercial CAD/ CAM system PowerShape/ PowerMill of Delcam. The software resource of milling system NovaMill is called Virtual Reality CNC Milling of Denford.

PACPE allows the automatic and parametric design of a helicopter blade, using features modelling technique. Thus, it was defined a hierarchic system of aerodynamics complex macro-features (ACMF), features and an aerodynamic airfoils database. The PACPE interface between computer and user is constituted from a pull down menu, an ensemble of dialogue boxes and an own captor of errors in view to avoid the wrong data introduction.

Starting with the 3D virtual model of the blade, obtained by PACPE, the software system PACAPE (Udroiu, 2007) generates the 3D model of the blade mould. This mould is realised using design by features and a hybrid modelling (solid modelling combining with surface modelling). The mould is composed from two parts (fig. 2): the upper mould part and the bottom mould part. The system of features is composed from constructive-technological macro-features (CTMF) and features. It is defined four categories of CTMF: CTMF of root, CTMF with constant airfoil, CTMF with variable airfoil and CTMF of tip. In the process of blade mould modelling it was defined three 3D digital models such as: billet mould model, raw upper-lower mould model and mould model.

An example of experimental blade and its mould obtained by PACPE and PACAPE is presented in figure 1. The upper and the lower part of the mould are composed from six CTMF.

ECU-Virtual and DACRAF solve the main issues of the manufacturing process of helicopter blade mould. ECU-Virtual is articulated around three following modules: VTOOL (Virtual specification of cutting tools), AsistGPM (Assistance to the development of machining process) and StrategEnt (Machining features strategies and generation of CN file). The input data for ECU-Virtual is a CAD neutral file, such as IGES or STEP. All CTMF of the mould can be exported from DWG parametric file format in a neutral file format.

The purpose of VTOOL module is the virtual and automatically identification of optimal cutting tools for each CTMF of the mould and determination of their main parameters. After that, VTOOL allows the automatic generation of these cutting tools in PowerMill commercial CAM system. VTOOL use features recognition technique.

The next module of ECU-Virtual, named AsistGPM provide assistance to the development of machining process. This module automatically determines the size of raw material for each CTMF, generate the block of raw material and check in if the CTMF can be manufactured with the selected CNC machine. It can be specify, that AsistGPM has incorporate the main specifications (spindle speed, travels, table size etc) about a lot of CNC machine. The establishing of cutting parameters concerning complex surface milling (CTMF of the mould) it is obtained using the software system DACRAF. These modules, VTOOL, AsistGPM, DACRAF provide information necessary to the forth module named StrategEnt.

StrategEnt establish in automatic way the machining strategies for each CTMF of helicopter blade mould and generate automatically the tool paths and NC files. The optimum strategies proposed within StrategEnt software are focused on 2 1/2 and 3 axis milling machine.

4. CONCLUSION

This research is focused on the integration of design, process planning and manufacturing process of moulds for composite blades, using like tool the concept of constructive-technological feature. Thus, it was development an integrated system for helicopter blades. Briefly, this system allows the automatic design of a helicopter blade and its mould, virtual specification of the optimal cutting tools, the establishing of cutting parameters concerning complex surface of the mould, choosing in automatic way the machining strategies for each CTMF of helicopter blade mould and generate automatically the tool paths and NC files. The mains benefits of the proposed system are the automation of the process and the reduction of product development cycle time. The validation of this system was done using the 2 1/2 axis NovaMill CNC milling machine from Denford. The further researches will be focus on the development of a knowledge based system for assembling and manufacturing of internal structure of the composite blade.

5. ACKNOWLEDGEMENTS

This study was supported by a National Research and Development Program of Romania, CEEX Grant 41/ 07.10.2005. The author expresses his gratitude to all partners for the fruitful collaboration.

6. REFERENCES

Chen, Z., M.; Gao, S., M.; Li, W., D. (2007). An approach to incremental feature model conversion, International Journal of Advanced Manufacturing Technology, Vol. 32, No.1-2, pp.99-108, ISSN 0268-3768

Ibrahim, R., N.; McCormack, A., D. (2005). Robustness and generality issues of feature recognition for CNC machining, International Journal of Advanced Manufacturing Technology, Vol. 25, No.7-8, pp. 705-713, ISSN 0268-3768

Lee, K., H.; McMahon, C., A.; Lee, K., H. (2003), Design of a feature-based multi-viewpoint design automation system, International Journal of CAD/CAM, Vol.3, No.2, pp. 67-75, ISSN 1598-1800

Machover, C. (1996). The CAD/CAM handbook, McGraw Hill, ISBN 0-07-039375-3, USA

Mawussi, K., Duong, V., H., Kassegne, K. (2000). Determination of the parameters of cutting tools in integrated design of products, CD-ROM Proceedings of the IDMME International Conference, Canada

Udroiu, R. (2003). Design and manufacturing of complex shape parts, PhD Dissertation, Transilvania University of Braspv, Romania

Udroiu, R. (2007). Computer aided design of tooling for aerospace composite parts, Proceedings of the 8th international conference "Modern Technologies in Manufacturing", Technical University of Cluj-Napoca, 4-5th October, ISBN 973-9087-83-3, pp. 449-452, Cluj Napoca, Romania.