Investigation into the plunger cooling tube system design for the narrow neck press and blow process

Perera, Noel (2001) Investigation into the plunger cooling tube system design for the narrow neck press and blow process. Doctoral thesis, University of Northumbria at Newcastle.

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Abstract

Although glass as a packaging material is well received by consumers, its manufacturing process is not fully understood. The two processes associated with glass container manufacture are the blow and blow and the press and blow processes. The narrow neck press and blow (NNPB) process was conceived to maintain the glass containers' competitive edge as a packaging material as it produces a lighter container at a lower cost.
The principal element of the NNPB process is the plunger. It shapes the cavity and disperses the glass within the container. The plunger operates both as a heat exchanger and a shaping tool. The plunger due to its harsh operating
environment, experiences extreme wear. It is liable for product defect, uneven thermal distribution and machine downtime. Plunger wear is partly related to the ineffective extraction of thermal energy by the plunger cooling tube system. Areas of poor plunger cooling correspond to the poor circulation of coolant air hence leading to plungers exhibiting premature wear and failure.
The work presented here is a scientific study of the current NNPB plunger cooling tube system. This has been carried out systematically by designing a laboratory experiment to simulate the manufacturing process of glass
containers and thus assess the boundary conditions (inlet airflow velocity and outlet pressure) for the cooling tube plunger system. In addition temperature boundary conditions were established using the thermal imaging technique. The
CFO models developed were in 2D, axisymmetric and 3D using the established boundary conditions (i.e. inlet airflow velocity, outlet pressure and parison temperature) to assess the performance of the plunger cooling tube system.
CFO modelling has enabled the modification of the cooling tube system design (i.e. 1.2mm hole diameter and hole positioning) to reduce the power/energy consumption by up to 80% during the heat extraction process. Furthermore the
CFO modelling has allowed a better understanding of the airflow behaviour (i.e. recirculation, stagnation) and performance of the plunger cooling tube system. This information is useful knowledge to the designer and manufacturing engineer and should result in finding the design solutions for the cooling tube system more readily.

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