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Optimizing anisotropy in injection-moulded poly(methyl methacrylate) parts using DOE and simulation

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Published/Copyright: October 3, 2025
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International Polymer Processing
From the journal International Polymer Processing Volume 40 Issue 5

Abstract

The injection moulding of Polymethyl Methacrylate (PMMA) is crucial for producing high-precision optical components where isotropic material properties are essential for uniform optical performance. Anisotropy, manifested as variations in volumetric shrinkage (Vs), residual stress (Rs), warpage, and density difference (δd), can compromise dimensional stability and optical clarity. This study investigates the influence of key injection moulding parameters on the anisotropy of 3 mm and 6 mm thick PMMA disks. A novel sectional probing technique was developed to assess core-to-surface variations along the z-axis, offering unique insights into internal anisotropy gradients that conventional methods often overlook. We employed a synergistic approach combining Design of Experiments (DOE) with Taguchi’s method, finite element simulation using Moldflow, and multi-objective optimization via genetic algorithms to identify optimal process conditions. Analysis of Variance (ANOVA) revealed that melt temperature and mould temperature are the most significant factors, accounting for 60 % and 36 % of the variance in Vs and Rs, respectively. A highly predictive linear regression model ( R Pred . 2 >0.95) was developed, demonstrating that optimization reduced Vs by 4 % and Rs by 9 % compared to the initial trials. The study also found that part thickness significantly amplifies anisotropy, with 6 mm parts exhibiting variations of 54 % increase in Vs, 54 % decrease in Rs and a 43 % rise in δd compared to 3 mm parts. Experimental validation using a linear polarized microscope and dial gauge measurements confirmed these simulation results, showing reduced birefringence and shrinkage in the optimized parts. The experimental shrinkage values were within 0.02 mm and 0.06 mm of the simulated values for the 3 mm and 6 mm disks, respectively. This work not only demonstrates the efficacy of integrating DOE, simulation, and optimization but also highlights the critical role of part thickness and the novelty of the sectional probing method in elucidating anisotropy mechanisms, providing a robust methodology for producing isotropic PMMA parts for advanced optical applications such as lenses and light guides.

Keywords: polymethyl methacrylate (PMMA); injection moulding; process optimization; residual stress; volumetric shrinkage; finite element analysis (FEA)
Corresponding author: R. Joseph Bensingh, Central Institute of Petrochemicals Engineering and Technology (CIPET), Guindy, 600032, Chennai, India, E-mail:

Funding source: Department of Science and Technology (DST); Science and Engineering Research Board (SERB)

Award Identifier / Grant number: DST-SERB CRG-2020004267

Acknowledgment

The authors would like to acknowledge the Department of Science and Technology (DST) and the Science and Engineering Research Board (SERB) of India for their monetary backing to this project. DST-SERB CRG-2020004267. The authors thank the scientists at CIPET for their invaluable support and expertise in optics and optical injection moulding, which were essential for analysing and interpreting process variables and responses.

  1. Research ethics: Not applicable.

  2. Informed consent: Not applicable.

  3. Author contributions: The author has accepted responsibility for the entire content of this manuscript and approved its submission.

  4. Use of Large Language Models, AI and Machine Learning Tools: None declared.

  5. Conflict of interest: The author states no conflict of interest.

  6. Research funding: The authors would like to acknowledge the Department of Science and Technology (DST) and the Science and Engineering Research Board (SERB) of India for their monetary backing to this project. DST-SERB CRG-2020004267.

  7. Data availability: Not applicable.

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Supplementary Material

This article contains supplementary material (https://doi.org/10.1515/ipp-2025-0052).

Received: 2025-05-20
Accepted: 2025-09-12
Published Online: 2025-10-03
Published in Print: 2025-11-25

© 2025 Walter de Gruyter GmbH, Berlin/Boston

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https://doi.org/10.1515/ipp-2025-0052
Keywords for this article
polymethyl methacrylate (PMMA); injection moulding; process optimization; residual stress; volumetric shrinkage; finite element analysis (FEA)

Articles in the same Issue

  1. Frontmatter
  2. Review Article
  3. Digitalization techniques in polymer processing – a review
  4. Research Articles
  5. Investigation on the extrusion-induced geometric distortion of three-lumen medical micro-catheters through numerical simulation
  6. Hemp-PEEK composites: surface treatment, processing, and performance
  7. Simulation of polyurethane foaming process based on physical property parameters
  8. Evaluation of mechanical properties of basalt and aramid fiber reinforced hybrid composites with polyvinyl chloride (PVC) core material
  9. The effect of styrene isoprene diblock content on hot melt label pressure-sensitive adhesives properties
  10. Dual nozzle electrospinning based on piezoelectric-conductive composites preparation: simulation and experiment
  11. Enhancing the strength and surface quality of carbon fiber reinforced PLA composite parts 3D printed using fused deposition modelling
  12. Combining Mag-Org fillers with epoxy-functionalised graphene to enhance the thermal stability of the polyvinyl chloride (PVC) based matrix while optimising its mechanical properties
  13. Performance enhancement of ternary epoxy hybrid composites with rice husk bio-filler
  14. Optimizing anisotropy in injection-moulded poly(methyl methacrylate) parts using DOE and simulation
  15. Hybrid biocomposites based on PLA/pine fiber/CaCO3
  16. Enhancement of mode I/II fracture toughness in basalt/Kevlar hybrid composites via multiwall carbon nanotube integration
  17. Quick assessment of melt flow index in hybrid bio-composite filaments for bio additive manufacturing
  18. Preparation, flame retardancy, and phase-change kinetics of OMMT/chitosan composite phase-change capsules
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