Casting moulds production on the basis of 3DP models.

Waraczynski, B. ; Weiss, E. ; Weiss, Z. 等

Abstract: In this paper was presented indirect method for generating casting moulds. As a master model was applied model generated in one of Rapid Prototyping methods--Three Dimensional Printing. Presented example concern on the lid of hand water pump. On basis of 3DP models, through negative (resin mould), was generated production model. Model like this can by used in hand forming as well as in moulding machines.

Key words: Rapid Prototyping, Rapid Casting, 3D-Printing

1. INTRODUCTION

Nowadays Rapid Prototyping techniques was developed up to degree that they allow for direct generating ready to use products. From this techniques it is necessary to distinguish Rapid Tooling techniques (allowing for tools producing), Rapid Manufacturing (allowing for small batch production). Three Dimensional Printing consists in selective binding powders with binder spread through printing head has significant meaning in this area of use. With ceramic powders or even with direct use of sand it is possible to produce directly casting moulds or complicated cores. Application like this can by called Rapid Casting.

2. INDIRECT CASTING MOULDS PRODUCTION WITH USE OF 3DP

ZCorporation is a one of companies with license for using three dimensional printing technology. This same company also worked out technology called ZCast. In this process is used mixture on the basis of quartz sand for producing moulds and cores. Process like this is very flexible, because it is possible to print out complicated mould with core for single cast of low temperature alloys. When situation require something more than piece production ZCast process become expensive. In this situation was worked out indirect methods for production of moulds.

Indirect production of moulds can be realized:

--in hand forming process;

--in automatic forming process.

Application of 3DP model during hand forming has certain disadvantages. Produced moulds have low quality and master model quickly use up oneself. In this situation we have quantity restriction and worse result. This technique is correct for test or prototype series.

In order to achieve better quality and productivity it is necessary to resin master model from 3DP master model. Between these two models it is required to generate resin mould (negative of 3DP master model). This paper present indirect casting moulds production practicable in automatic moulding process. The device which was used for producing master models was Z400 from ZCorporation and the master models was built from plaster based powder.

3. MASTER MODELS OF LID

First step in process of production master models for automatic forming is to produce 3DP master model and prepare his surface. CAD model before producing in 3DP technology must be also adequately prepared for iron casting.

[FIGURE 1 OMITTED]

4. PRODUCING RESINE MOULDS ON THE BASIS OF 3DP MODEL

Production process of resin moulds was carried out in the following steps:

1. 3DP models were coated with varnish. This step was necessary to fill porous surface of models;

2. Models were grinded and polished for finally preparation of surface;

3. Models were coated with separating substance. This procedure is needed for better pulling out 3DP models from produced resin moulds;

4. Models were arranged in wooden boxes;

5. Gel coat was applied as a contact surface of resin moulds;

6. Produced layer was strengthened with coat of epoxy resin;

7. Rest of free space of moulds was filled out with filler (epoxy past);

8. 3DP models were pulled out.

After each operation where was used resin, were also applied pauses necessary for create chemical bonds.

[FIGURE 2 OMITTED]

5. PRODUCING RESINE MASTER MODELS

Production process of resin models was carried out in the following steps:

1. Moulds were coated with separating substance. This procedure is needed for better pulling out resin models from moulds;

2. Prepared moulds was flooded with polyurethane resin;

3. Open surfaces of moulds were evened up;

4. Produced resin master models were pulled out from.

After each operation where was used resin, were also applied pauses necessary for create chemical bonds. Produced resin models are characterized by good quality of surfaces enough for aims of founding.

[FIGURE 3 OMITTED]

6. USE OF RESINE MASTER MODELS

Resin master models prepared in previous stages were placed on moulding boards. On moulding boards were also placed gating system (Fig. 4).

Moulding boards with models can be mounted in squeeze moulding machine, where moulding sand is under pressure pressed on them. Two parts of mould are received after this operation and after combination of them they are poured with liquid metal. Final effect is presented on Fig. 5.--cast iron lid. Product should be also machined.

[FIGURE 4 OMITTED]

[FIGURE 5 OMITTED]

7. SUMMARY

Up to this day many factories use only machining methods for producing master models. In these cases not every part can by machined. Rapid Prototyping techniques extend possibilities and give greater liberty in designing.

Resin master models produced as was presented give a possibility of production on squeeze moulding machines. After manipulation of used resin it is possible to achieve durability of models enough for medium and also long-run production. On the basis of presented research and observations the conclusion is that very important is to prepare surfaces of 3DP models. Quality of these surfaces has great meaning for cooperation models with moulds.

Direct using 3DP model as a master model in mould forming is also very attractive. 3DP models have lower resistance on wear but in piece production they give good results. In this case efficiency will be greater because of shorter time of production--it is no need to create resin mould.

Three Dimensional Printing models have significant high level of surface roughness. Nevertheless after properly prepared surfaces it is possible to use model like this as a master model for producing resin moulds.

8. REFERENCES

Rapid Manufacturing, Vom Prototyp zur Produktion, Erwartungen, Erfahrungen, Entwicklungen, Seminarberichte IWB, Herbert Utz Verlag Wissenschaft, Augsburg 2004.

Gebhardt A., Rapid Prototyping, Werkzeuge fur die schnelle Produktentstehung, Carl Hanser Verlag, Munchen, Wien 2000.

Chlebus E., Innowacyjne technologie rapid prototyping--rapid tooling w rozwoju produktu, Oficyna Wydawnicza Politechniki Wroclawskiej, Wroclaw 2003.

Sachs E.M., Haggerty J.S., Cima M.J., Williams P.A., Three Dimensional Printing techniques, United States Patent nr 52004055, Cambridge 1993.

Waraczynski B., Zastosowanie metody 3D Printing do budowy modeli i form, M.Sc. Eng. thesis (in Polish)--Poznan University of Technology, Poznan 2004.