Optimization of Injection Moulding Process Parameters for Disposable Specimen Collection Containers

Abstract

Generally, in medical industry, the single use disposable specimen collection containers requirement has vastly increased. The main property of the container is transparency, to achieve this property in the manufacturing industries, uses only virgin polypropylene (PP) material. In the manufacturing process, the products are produced by injection moulding. By properly selecting various parameters which leads to better quality of products. In this work, the aim is to optimize injection moulding process parameters. The parameters selected are injection pressure, melting temperature, cooling time, packing time, and packing pressure. The optimization of the process parameters in injection moulding process by using recycled polypropylene specimen collection containers helps in the production cost, cycle time and virgin material cost.

Introduction

Injection Molding Machines Overview:

Several types of injection molding machines exist, including plunger, plunger preplasticating, screw preplasticating, and in-line screw types. Currently, the in-line screw type is widely used due to its efficiency. The machine mainly consists of two units: the injection unit and the clamping unit.

• Hopper: Holds plastic pellets, often with a dryer to remove moisture and magnets to filter metal particles.

• Barrel: Heats and melts the plastic pellets. The screw inside the barrel moves and mixes the molten plastic.

• Reciprocating Screw: Rotates to move pellets forward, compress, mix, and melt them evenly through friction and heat.

• Heaters: Various heaters maintain the required temperatures in the barrel, mold, and nozzles.

• Nozzle: Injects molten plastic into the mold and can also filter, mix additives, or shut off melt flow.

• Ejector Pins: Push molded parts out of the mold once cooled, with different pin types for durability and self-lubrication.

• Split Molds: Molds consist of two halves (parting line) that open to release the molded part, often moved by mechanical or hydraulic means.

Injection Molding Process:

1. Injection: Plastic pellets are gravity-fed into the injection unit, melted by heat and pressure, and injected into the mold.

   • The reciprocating screw melts and mixes the plastic before injecting it.

   • Shot size and screw recovery time regulate the material volume.

2. Clamping: Mold halves are closed and held under pressure by mechanical, hydraulic, or hydromechanical clamps during injection.

3. Injection Molds: Molds are precisely machined and heat-treated, with types like two-plate, three-plate, and stack molds used depending on the application.

4. Control System: Controls the screw movement and pressure during the molding cycle to ensure quality and precision.

Defects and Parameters:

Common defects like poor surface finish, flash, weld lines, sinks, voids, and warpage can be minimized by adjusting process parameters such as injection pressure, melt temperature, mold temperature, packing pressure, and cycle time.

Shrinkage varies by material and process conditions, influenced by uneven cooling, material behavior, and thermal strain. Controlling shrinkage requires careful parameter management.

Parameter Selection and Experimentation:

Process parameters affecting product quality include temperature, pressure, and time, which are interdependent. Experiments (e.g., using Taguchi’s orthogonal array) help optimize parameters like injection pressure, melting temperature, cooling time, packing time, and packing pressure.

Experiment Details:

• Material: Polypropylene (PP) with 40% calcium carbonate, widely used in automotive and medical products.

• Equipment: Haitian Plastics Machinery MA2000 with 1540 bar injection pressure.

• Method: Taguchi orthogonal array method applied to study parameter effects systematically, aiming for optimal quality and performance.

Conclusion

The main objective of this research work is to identify parameters which affects the performance of the Urine Container and determine an effective method to incorporate the critical performance factor into an equation in order formulate a suitable performance rating method and recycling plastic can reduce consumption of energy. The effect of recycled PP and virgin PP on impact strength optimal values of process parameters was analyzed. The optimal amounts of mixture components to produce recycled plastic products are determined. As the results of doing systematic experimentation, using mixture experiments, the quality of recycled plastic products can be improved and becomes more robust to variations at the optimal operating settings. The results have proven that the manufacturer can use these settings of recycled PP and virgin PP to produce quality products with low cost (quality depends on source as some recycled content qualities can be very high) and environmental impact reduction. In this work, the effect of using pre-consumer PP scraps (which can be collected during Urine Container production process), as an alternative to post-consumer recycling, mixed with virgin Urine Container PP on static and long-term mechanical properties is studied. Samples were prepared by blending virgin PP with various contents of recycled PP.

References

[1] N. Divya, Dr.Ch.V.S. Parameswara Rao, Dr. S.S.N. Malleswara Rao, (March 2017) “Multiintegral Analysis of Injection Mould with Hot Runners for Gate”, International Journal of Scientific and Research Publications, Volume 7, Issue 3, ISSN 2250-3153 [2] G. Rajendra Prasad, Dr S. Chakradhar Goud, Multiintegral May -2017, “Analysis of Injection Mould with Hot Runners for Gate”, International Journal of Engineering Sciences & Research Technology, ISSN: 2277-9655 [3] Ivan W.M. Chana, ?, Martyn Pinfold a, C.K. Kwongb, W.H. Szeto, (2014) \"Automation and optimization of Family Mould Cavity and Runner Layout Design (FMCRLD) using genetic algorithms and mould layout design grammars”, Elsevier, Computer-Aided Design 47 118–133 [4] V.Chandra Sekhar, N. Jaya Krishana, Hot Runner Mould Design and Plastic Flow Analysis for CAP, International Journal & Magazine of Engineering, Technology, Management and Research, ISSN No: 2348-4845 [5] Campbell, GA, Campbell SE, Bullwinkel M, Savoka J, Ragona L, et al. Effect of oil additives and injection molding process parameters on the tensile and impact energy of polypropylene. Proceedings, 59th Annual Technical Conference of the Society of Plastics Engineers2001. p. 466-70. [6] Lee TS, W.A.W.A. Rahman, A.R. Rahmat, Tiam TT, Soo TB, Low CY. Computer aided injection moulding process analysis of polyvinyl alcohol–starch green biodegradable polymer compound. Journal of Manufacturing Processes. 2012; 14:8-19.

Copyright

Copyright © 2025 Ajay Kumar S, Dr. R. Uday Kumar, K. Sirisha. This is an open access article distributed under the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.