The effect of cooling time and colorant pigment on the dimensional accuracy of plastic injection molded closure

Open Access

Year : | Volume : | : | Page : –
By

    John Njagi

  1. Steven O. Otieno

  2. Fredrick M. Mwema

  3. Peter N. Muchiri

  1. , Department of Mechanical Engineering, Dedan Kimathi University of Technology, , Kenya
  2. , Department of Mechanical Engineering, Dedan Kimathi University of Technology, , Kenya
  3. , Department of Mechanical Engineering, Dedan Kimathi University of Technology, University of Johannesburg, Auckland Park Campus, , South Africa
  4. , Department of Mechanical Engineering, Dedan Kimathi University of Technology, University of Johannesburg, Auckland Park Campus, , Kenya

Abstract

Dimensional accuracy is a critical aspect of precision injection molding, with the products generally required to conform to set tolerances. Major causes of these deviations are reported to be related to the polymer material, part geometry, injection mold design, and process parameters. This study investigated the effects of material color pigment and its interaction with process cooling time on product dimensional accuracy. This study was conducted experimentally, where three levels of cooling time and four material color pigment types were used to design a complete factorial experiment. The injection molding process used a 32-cavity injection mold to form closures at parameter combinations. The lateral and transverse dimensions of the samples produced from each experiment were measured, and averages were computed. Mains effect and interaction effect plots were made to determine the impact of process parameters on dimensional variation. Closures made from blue colorants had the lowest dimensional error, whereas white paint had the most significant dimensional error. The lower dimensional error was obtained for all the colors at more down-cooling times. The relationship between colorant and dimensional deviation depends on the cooling time for both dimensions. Cooling time (48%) and paint (37%) significantly affected the dimensional stability of the internal diameter.
In contrast, only colorant (83%) and cooling time (48%) significantly affected the dimensional stability of the closure height and external diameter, respectively. To obtain zero-dimensional error, a black pigment could be used with a process cooling time of 1.8s, while a blue pigment material could be used with a cooling time of 2.6s. The result of this study provides insight into process cooling time optimization for dimensional error control at different material pigment colors.

Keywords: Injection molding, dimensional accuracy, cooling time, color pigments

How to cite this article: John Njagi, Steven O. Otieno, Fredrick M. Mwema, Peter N. Muchiri The effect of cooling time and colorant pigment on the dimensional accuracy of plastic injection molded closure jopc ; :-
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Open Access Original Research
Volume
Received October 30, 2023
Accepted November 20, 2023
Published