PLASTER - POLYESTER CASTING TECHNIQUES IN THE ART OF SCULPTURE

Sculpture art forms an integrity within itself in mass and volumetric sense in the period from the first age to the present in the classical sense. Likewise, the art of sculpture made progress by developing itself further with concepts such as mass, volume, emptiness, fullness, light and shadow, which were revealed in the medieval and baroque period. Especially the separation of the sculpture, which was created with classical materials, with different phenomena with the formation process (clay, mud, marble, wood, bronze, etc.) began to express itself as a separate definition with casting processes as well as molding with materials. In this study, mold making processes, which are indispensable of sculpture art, will be examined by using two different casting techniques from sculptures that have been molded. In this context, it is observed that gypsum mold and polyester mold technologies continue to be used today with the developments and changes that they have undergone from the past to the present. To summarize, within the scope of this study, detailed processes related to casting the work whose mold was taken over classical sculpture technology were explained. Keywords: Sculpture, mold, casting, plaster, polyester

Influence of Heat Sink on the Mold Temperature of Gypsum Mold Used in Injection Molding

Gypsum molds have been developed as an alternative for the Rapid tooling (RT) method used in injection molding. However, the poor capability of the heat delivery forces the gypsum mold to operate under a high-risk condition, and distortion of the molded part becomes apparent. The goal is to investigate the effect of a heat sink on the reduction of the gypsum mold temperature and to establish a methodology for the heat sink design. The methodology used the advantage of the electrical circuit concept to analyze the mold temperature. The heat transfer of a mold was modeled using an equivalent thermal circuit. After all the components on the circuit were determined, the heat transfer rate could then be calculated. Once the heat transfer rate was known, the mold temperature could be easily analyzed. A modified thermal circuit considering transverse heat conduction was also proposed, which estimated the mold temperature more accurately. The mold temperature was reduced by 16.8 °C when a gypsum mold was installed with a 40 mm thick heat sink in a parallel configuration. Moreover, the reduction of the mold temperature improved the deflection of the molded part from 0.78 mm to 0.54 mm. This work provides a quick approach to analyze the mold temperature based on the thermal circuit concept. As the cooling system of the mold was modularized analytically, important properties of the cooling system in the heat transfer process were revealed by analyzing the thermal circuit of the mold, for example, the heat transfer rate or the mold temperature.

The Temperature Distribution Research of Foaming Gypsum Mold in the Fabrication and Pouring Process

This paper describes study of temperature variation in the gelling and hardening, thermal baking and pouring stage of foaming gypsum mold. The temperature difference curve in the gelling and hardening process shows an rapid decline, tending to the placid downward eventually after a clipping rise. During the thermal baking stage, owing to the low heat conduction coefficient of the foaming gypsum mold, the actual temperature of each thermocouple lags behind the craft temperature, lag degree increases gradually with the extension of baking temperature and holding time. At the initial period of pouring process for molten aluminum, the temperature of center position in the mold increases fast by absorbing lots of heat in the solidification process, whereas, slower temperature rising curve occurs in the edge and intersection position. Coupled with the ongoing of air convection heat transfer, resulting in a continuous falling of temperature, therefore the temperature difference curve of each point inside the mold shows a successive upward trend with the solidification process of molten aluminum alloy.

Shape Forming of Alumina by Step Pressure-Vacuum Hybrid Slip Casting

Conventional methods for preparing ceramic bodies, such as cold isostatic pressing, gypsum-mold slip casting, and filter pressing are not completely suitable for fabricating large and thick ceramic plates, because of disadvantages such as the high cost of equipment, formation of density gradient, and differential shrinkage during drying. These problems could be avoided by employing step pressure-vacuum hybrid slip casting in which consolidation occurs not only by the compression of the slip in casting room, but also by vacuum sucking of the dispersion medium (water) around the mold. This method enabled us to fabricate a 110 × 110 × 20 mm alumina plate without cracks and with homogenous density, and the possibility of extending the method to fabricate other ceramic products appears to be promising.

Study on Gypsum Molding Material Properties and Alloy Liquidity

In this paper the influence of gypsum-water ratio, filler types and calcination temperature on gypsum bending strength were analyzed by the means of experiments. Spiral-shaped gypsum mold was made by gypsum molding material and mobility experiment was conducted on Pb-Sn alloys. Compared with pure gypsum, gypsum mixture had better mechanical properties. The fluidity of the alloy in the gypsum mold was prone to casting pressure, pouring temperature and alloy ratio. The research results have benefit to the development of gypsum casting technology.

Linear dimensional change in acrylic resin disinfected by microwave energy

The purpose of this study was to characterize the linear dimensional change in specimens made in aluminum rectangular dies (65.0x12.0x3.5mm), with 4 reference demarcations, using the Clássico, Onda-Cryl and QC-20 brands of acrylic resin. Wax patterns with 67.0x15.0x5.0mm were embedded in metallic or plastic flasks with stone gypsum, according to the conventional technique. After stone gypsum setting, the wax molds were removed and the aluminum dies impressed in the stone gypsum mold with silicone material. The powder/liquid proportion and acrylic resin were manipulated according to manufacturer’s instructions. The metallic flask pressure was achieved using the RS tension method. After polymerization in water at 74OC for 9 hours, ebullition water for 20 minutes or microwave energy (900 W) for 10 minutes, the specimens were cooled at room temperature and then removed from the flasks and submitted to conventional finishing. The distances between the A-B, C-D, A-C, and B-D reference points were measured before and after disinfection by microwave energy (650W for 3 minutes). The linear dimensional evaluation of the distances was performed by the same operator with an Olympus optical comparator microscope, with an accuracy of 0.0005mm. Obtained data were submitted to ANOVA and Tukey’s test (α=.05%). The disinfection by microwave energy did not alter the original linear dimensions of the specimens.