Study of the glass press molding process

Ing. Selma Kunosic

Master's thesis

Abstract:

The glass molding process can press glass perform into a shape of finished lens under high pressure and temperature conditions, and it is easy to achieve mass production. So, it has emerged as a promising alternative way to produce complex shape lens. However, there are inherent technical issues associated with the process that has prevented it from being widely used in the industry. The aim of this thesis is to understand the basic underlying physics of the glass molding process. It was also desired to develop a reliable process simulation model that can be utilized for making process predictions and accordingly design, optimize and improve its performance. More specific research objective of this work is to develop a relatively simple physics-based numerical method but yet accurate enough to model a compression glass molding process for manufacturing process, predict the final shape of the glass element at the end of the molding process, and to predict the critically important residual stresses at the end of the molding process. The specific objectives of the proposed research are to: 1. Conduct experiments on a commercial machine to study process feasibility to mold a precision aspherical glass lens with the desired surface finish and curve accuracy as well as determine process repeatability. 2. Perform a parametric experimental study to investigate the influence of different molding parameters on process performance. 3. Develop a 2D FEM model of lens molding by incorporating viscoelastic stress and structural relaxation phenomenon of glass into the simulation. This research was used to show possibility of numerical modeling of glass press molding process. We were able to develop material model for simulation that shows good agreement with experimental results. Experiments were performed on commercial glass press molding machine, and parameters from experiments were used to run the simulation. FEM model was developed firstly for test element, and then it was used to perform simulation on real element. Results from simulations are in a good agreement with the theory of process of glass press molding. The main goal of glass molding process is to manufacture precise aspherical optics for reasonable price. This goal could not be achieved without deep knowledge of the thermomechanical processes, without detailed data of thermomechanical properties of used materials and without possibility to perform numerical simulation.

Abstract:

The glass molding process can press glass perform into a shape of finished lens under high pressure and temperature conditions, and it is easy to achieve mass production. So, it has emerged as a promising alternative way to produce complex shape lens. However, there are inherent technical issues associated with the process that has prevented it from being widely used in the industry. The aim of this thesis is to understand the basic underlying physics of the glass molding process. It was also desired to develop a reliable process simulation model that can be utilized for making process predictions and accordingly design, optimize and improve its performance. More specific research objective of this work is to develop a relatively simple physics-based numerical method but yet accurate enough to model a compression glass molding process for manufacturing process, predict the final shape of the glass element at the end of the molding process, and to predict the critically important residual stresses at the end of the molding process. The specific objectives of the proposed research are to: 1. Conduct experiments on a commercial machine to study process feasibility to mold a precision aspherical glass lens with the desired surface finish and curve accuracy as well as determine process repeatability. 2. Perform a parametric experimental study to investigate the influence of different molding parameters on process performance. 3. Develop a 2D FEM model of lens molding by incorporating viscoelastic stress and structural relaxation phenomenon of glass into the simulation. This research was used to show possibility of numerical modeling of glass press molding process. We were able to develop material model for simulation that shows good agreement with experimental results. Experiments were performed on commercial glass press molding machine, and parameters from experiments were used to run the simulation. FEM model was developed firstly for test element, and then it was used to perform simulation on real element. Results from simulations are in a good agreement with the theory of process of glass press molding. The main goal of glass molding process is to manufacture precise aspherical optics for reasonable price. This goal could not be achieved without deep knowledge of the thermomechanical processes, without detailed data of thermomechanical properties of used materials and without possibility to perform numerical simulation.

Keywords

Glass, lens, molding, press, viscoelasticity, simulation, experiment, aspheric, stress, material.

Language used: English

Date on which the thesis was submitted / produced: 26. 5. 2016

Thesis defence

• Date of defence: 16. 6. 2016
• Supervisor: prof. Ing. Tomáš Vít, Ph.D.

Technical University of Liberec

Faculty of Mechanical Engineering

Master programme / field:
Mechanical Engineering / Machines and Equipment Design