A R C H I V E S

o f

F O U N D R Y E N G I N E E R I N G

Published quarterly as the organ of the Foundry Commission of the Polish Academy of Sciences

ISSN (1897-3310) Volume 10

Issue Special1/2010 399-404

78/1

Geometric accuracy of wax bade models manufactured in silicon moulds

G. Budzik a, H. Matysiak b

a Department of Machine Design, Rzeszów University of Technology, Al. Powstańców Warszawy 8, 35-959 Rzeszów b Research Center “Functional Materials” at Warsaw University of Technology, Poland

*e-mail: gbudzik@prz.edu.pl, hmatysia@inmat.pw.edu.pl

Received 05.03.2010; accepted in revised form 23.03.2010

Abstract The article presents the test results of the geometric accuracy of wax blade models manufactured in silicon moulds in the Rapid Tooling process, with the application of the Vacuum Casting technology. In batch production casting waxes are designed for the manufacture of models and components of model sets through injection into a metal die. The objective of the tests was to determine the possibility of using traditional wax for the production of casting models in the rapid prototyping process. Blade models made of five types of casting wax were measured. The definition of the geometric accuracy of wax blade models makes it possible to introduce individual modifications aimed at improving their shape in order to increase the dimensional accuracy of blade models manufactured in the rapid prototyping process. Key words: Rapid Prototyping, aircraft engine blades, Rapid Tooling, wax casting models

1. Introduction The manufacture of high-quality casts requires the application

of modern research and production methods [1-5]. Rapid prototyping systems are increasingly used in the manufacture of aircraft components [5-11]. Some incremental RP systems enable the production of casting models used for the construction of casting moulds [12-14]. The scope of rapid prototyping application can be expanded considerably through the use of indirect Rapid Tooling methods. One of the Rapid Tooling techniques is manufacturing silicon dies and prototypes at lowered pressure in the Vacuum Casting technology. Silicon moulds make it possible to produce models using casting waxes as well as polyester, epoxide and polyurethane resins [15]. The accuracy of prototypes manufactured in silicon dies depends on a variety of technological factors. The accuracy of wax models

production can be evaluated with the application of the coordinate measuring technique. Literature describing methods of producing wax blade models in silicon moulds usually neglects to mention the aspect of their shape and dimensional accuracy. It is for this reason that the article seeks to explore this theme.

2. Blade model

Tests were carried out on a specially designed blade model. The 3D-CAD test model coordinate system was joined with the midpoint of the upper blade basing plane (fig. 1). Such a coordinate system was the basis for the identification of the model in the coordinate measuring machine programme space. The lower part of the blade constitutes a fixing element which enables a precise orientation of the model for measurement.

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Fig. 1. Test blade measuring model

Base surfaces were made in the model allowing for set-up of the model orientation prior to the measurement. The adopted way of producing the blade model enables its measurement without the necessity to replace the gauging point (contact tip, feeler) and without changing the orientation of the measuring/gauge head.

Based on the 3D-CAD model, a base stereolithographic model was constructed, which was then used to produce a silicon mould. Tests were conducted on wax models cast in a silicon mould using the following types of wax: B405 (fig. 2a), RECLM (fig. 2b), Blue Wax RECLM+ (fig. 2c), A7FR/60 (fig. 2d) and KC41017B (fig. 2e).

Fig. 2. Blade models made of wax type: a) B405, b) RECLM, c) Blue Wax RECLM+, c) A7FR/60, e) KC41017B

3. Measurements 3.1. The preparation of the measuring machine

The analysis of wax blade models geometric accuracy was made with the use of a WENZEL LH 87 coordinate measuring machine (fig. 3) equipped with a Reinshaw tactile scanning head. The machine is computer-controlled, based on the standard Metrosoft CM3.8 software. [15]. The general conditions of taking measurements are presented in literature [15].

The accuracy tests included: • the preparation of the coordinate measuring machine, • the import of the 3D-CAD blade model into the machine

programme space, • the preparation of the base and fixing elements for the measured

blade model, • the design of the CNC software for blade measurement on the basis

of the 3D-CAD model, • taking measurements.

Fig. 3. General view of measuring position

The measuring position was equipped with on the bench of the measuring machine. The ensured the basing of the vice during the fixing of the measured blade. The selection of the gauging point (contact tip, feeler) and other standard operations were performed according to the coordinate measurements procedure [15].

The designed CNC measuring software made it possible to carry out a series of measurements quickly. The procedures of the software included: • the reading in of the fixing vice coordinate system data, • the reading in of the blade 3D-CAD model data, • the definition of points position/orientation on the blade model base

surfaces, • the measurement of the blade geometry in selected sections, • the creation of a graphic measurements report, • the printout of the measurements results.

The measurements featured scanning along the measuring paths (in the x, y plane) spaced at 5mm-intervals along the z axis (fig. 4).

Fig.4. Blade scanning along the measuring path

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3.2. Analysis of measurements results

The software of the Metrosoft CM 3.8. Wenzel Metromec coordinate measuring machine makes it possible to keep track of deviations during the measurement. It also enables a geometric interpretation with reference to the nominal model (3D-CAD) [15]. The measurement protocols were presented as general visualisations in 3D space (fig. 5) and as detailed ones in the form of deviations values at individual points of the measuring paths of the blade sections.

A protocol can also contain concrete deviations values at selected measuring points in a tabular form. The table of results presents the nominal coordinates of the point, the measured values of the point, the detailed deviations and the general value expressed in percentage terms. The results of the blade models measurements were presented graphically in the form of detailed measurement protocols (fig. 6-10). Fig. 5. General measurement protocols in the isomeric view

Fig. 6. Measurement protocol of the B405 wax blade model

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Fig. 7. Measurement protocol of the RECLM wax blade model

Fig. 8. Measurement protocol of the Blue Wax RECLM+ blade model

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Fig. 9. Measurement protocol of the A7FR/60 wax blade model

Fig. 10. Measurement protocol of the KC41017B wax blade model

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3. Conclusions

The measurements results of wax blade models produced with the application of the coordinate measuring machine confirmed the previous results of calculations conducted on the basis of measurements of flat samples, described in literature [15]. The B405, RECLM and Blue Wax RECLM+ wax types have a high shrinkage. The contraction of the A7FR/60 and KC41017B composite waxes, reinforced with polymer particles, is lower and, hence the smaller deviation value, compared with the blade nominal model.

It was found that all the wax types tested can be used for the manufacture of models in silicon moulds, in compliance with proper technological procedures.

The analysis of the measurements results showed that the shape of the blade also affects the deformation resulting from the wax contraction. The measurements results made it possible to determine the processing shrinkage compensation correction – the correction of the 3D-CAD model geometry. The compensation procedure will enable the manufacture of wax blade models whose shape and dimensional accuracy will correspond to the assumed tolerance.

Acknowledgements The present study was financed from resources of MNiSzW as

part of the PBZ-MNiSW-03/I/2007 project.

References [1] G. Budzik, H. Matysiak, J. Pacana, M. Cygnar, The analysis

of chosen methods of Rapid Prototyping of casting models for blades of aircraft engines, Combustion Engines No 2009-SC1, s. 283-288

[2] N. Homburg, E. Wellbrock, Knowledge – based manufacturing strategy and methods for foundries, Conference and Exhibition for Rapid Technology, Erfurt 2006.

[3] R. Hartym, Dimensional accuracy of investment casting for the burned pattern process, Archives of Foundry, Volume 6, No18 (2/2), (2006) 231-236 (in Polish).

[4] R. Haratym, J. Tomasik, The influence of ceramic mould quality on surface geometry of al investment casting, Archives of Foundry, Volume 6, No18 (2/2), (2006) 237-242 (in Polish).

[5] A. Gebhardt, Rapid Prototyping, Carl Hanser Verlag, Munich 2006.

[6] T. Wohlers, Wohlers Report 2009 – State of the Industry, Annual Worldwide Pro-gress Report. Wohlers Associates Inc., Fort Collins, CO, USA 2009.

[7] I. Gajdoš, J. Slota, E. Spišák, FDM prototypes virtual modeling, ICAT 2008, 2nd International Conference on Additive Technologies: DAAAM Specialized Conference: September 17th -19th, 2008, Ptuj, Slovenia: Proceedings. Vienna: DAAAM International, 3 p. ISBN 3-901509-72-0

[8] J.C. Feriera, E. Santos, H. Madureira, J.Castro, Integration of VP/RP/RT/RE/RM for rapid product and process development, Rapid Prototyping Journal Vol. 12 No. 1/2006, Emerald 2006, 18-28.

[9] W. Liou, Rapid Prototyping and engineering applications – a toolbox for prototype development, Taylor & Francis Group, 2008.

[10] G. Budzik, T. Markowski, M.Sobolak, Hybrid foundry patterns of bevel gears. Archives of Foundry Engineering, Vol. 7, Issue 1/2007, s. 131-134.

[11] G. Budzik, T. Markowski, M. Sobolak, Prototyping of Bevel Gears of Aircraft Power Transmission, Journal of KONES Powertrain and Transport, Vol. 14, No. 2, Warszawa 2007, s. 61-66.

[12] G. Budzik, Possibilities of utilizing 3DP technology for foundry mould making, Archives of Foundry Engineering, Vol. 7, Issue 2/2007, s. 65-68.

[13] G. Budzik, The analysis of the possibility of the application of the casting waxes in the process RP, Archives of Foundry Engineering, vol. 9, No 2/2009, s. 133-136.

[14] G. Budzik, Surface Roughness of Aircraft Engine Blade Models Produced with Various Methods of Rapid Prototyping, Journal of KONES Powertrain and Transport, Vol. 14, No. 2, Warszawa 2007, s. 55-60

[15] G. Budzik, Imaging of blade curvilinear surface of the hot part of aircraft engines in the rapid prototyping process, Rzeszów University of technology (in Polish).

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