Thermal contact resistance in injection molding

✍ Scribed by Chi J. Yu; J. E. Sunderland; C. Poli

• Publisher: Society for Plastic Engineers
• Year: 1990
• Tongue: English
• Weight: 550 KB
• Volume: 30
• Category: Article
• ISSN: 0032-3888
• DOI: 10.1002/pen.760302408

✦ Synopsis

Abstract

This paper describes a method for obtaining the thermal contact resistance (TCR) between an injection molded part and its mold. Due to the absence of TCR the simulated cooling times obtained from Polycool II, a computer aided engineering (CAE) package for cooling simulation of injection molding, have compared poorly with both field and experimental data. This paper shows that an improvement in the accuracy of the simulated data results from making TCR an Input to Polycool II. TCR was obtained through a combination of experimental and analytical procedures. Experimental work was performed to obtain the part surface temperature distribution and the inside cavity pressure gradient. The part surface temperature distribution was then used as a boundary condition in the thermal analysis. The inside cavity pressure gradient was utilized as a basis for determining the inside cavity shrinkage. The results show that due to the thermal expansion of thermoplastics, the compressibility of the plastic melt, and the mold deformation, the inside cavity shrinkage is reduced as the thickness of the part is increased. Therefore, the TCR value of a thicker part is lower than that of a thinner part. The effects of both part thickness and process parameters, such as temperature and pressure, on TCR are also discussed.