Flexible Investment Casting Wax Patterns for 3D-Printing: Their Rheological and Mechanical Characterizations

Abstract

The mechanical and rheological characterizations of flexible investment casting patterns capable of 3D printing are reported. The wax pattern was composed of microcrystalline hydrocarbon wax (DMW7478), Piccotex 75 (a copolymer of α–methyl–styrene and vinyl toluene with a 75/25 molar ratio, respectively) and Escorene (a copolymer of ethylene and vinyl acetate with a 72/28 mass ratio, respectively). It was found that in order to obtain a wax pattern with appreciable mechanical properties, the content of the microcrystalline hydrocarbon wax in these blends should not exceed 30% (m/m). Thus, a series of patterns with 28% (m/m) wax and varying Piccotex and Escorene contents spanning from 0 to 72% (m/m) was prepared. The dependence of the dynamic viscosities of the wax patterns on the composition was described using a stretched exponential model, whereas their variations with the temperature were interpreted in terms of the Arrhenius–Guzman equation. Furthermore, the slopes of the lines fitted to the viscosity versus temperature curves at the pour point decreased linearly with the Piccotex content. Non-Newtonian changes in the shear stress with the shear rate and shear stress crystallization were observed at temperatures near the pour points. The mechanical properties were evaluated using the uniaxial tensile mode and by three-point bending experiments. It was found that the stress (σ) versus the relative elongation (ε) curves can effectively be rendered by means of the standard linear solid (SLS) viscoelastic model. In addition, it was also established that the Young’s modulus varied according to a sigmoid-type curve with the piccotex content, while the yield stress decreased linearly with the concentration of Piccotex. In addition, based on the spooling suitability and printability, the patterns were rated and it was found that the most appropriate wax pattern compositions for 3D printing were those which contained 30% (m/m) and 35% (m/m) Piccotex.

The Effect of Heat Treatment on a 3D-Printed PLA Polymer’s Mechanical Properties

“…The mechanical parameters of additive-manufactured polymers can be enhanced with heat treatment after the printing process [ 14 , 15 , 16 , 17 , 18 , 19 , 20 , 21 , 22 , 23 , 24 , 25 ]. The material properties of 3D-printed samples can be characterized via material testing [ 26 , 27 ]. Several researchers have conducted tensile tests to determine FDM-printed and heat-treated specimens’ mechanical properties, measuring the increase in UTS (32%) by annealing the specimens at 90 °C for 1 h [ 25 ].…”

Rapid Prototyping and Tooling Technology to Assist the Development of Low-Cost Dies

“…Wax is one of the thermoplastic materials that has been utilized for the longest in recorded human history. Due to their varied and variable qualities, which allow them to generate final products that meet a variety of needs, waxes are primarily utilized in foundries such as the production of wax patterns in traditional investment casting process [13]. The next step includes the investment casting of the wax patterns of the selected product.…”

Experimental Study on Warpage Phenomenon of Wax Parts Manufactured by Fused Filament Fabrication

“…On the other hand, the affordability and availability of FFF machines make the technology the most popular in the AM industry. In addition, recent studies demonstrated that it is possible to manufacture low-cost wax patterns having properties very similar to traditional IC waxes [ 8 , 9 ]. For example, non-tough wax parts having low viscosity in the molten state have been manufactured by the authors of the current study [ 8 ].…”