Modelling of the Glass Press-Blow Process

S.M.A Allaart-Bruin

Press-Blow Process of Glass

Press-blowing is a process that is commonly used in the glass industry to produce container glass (i.e., glass bottles and jars). The press-blow process consists of a pressing stage (1) and a blowing stage (2).

Initially the mould is open from above. Once a gob of glass is inside the mould, the mould is closed and the plunger moves upgradually. In this mould we obtain an intermediate form, the parison. This parison is transferred into a second mould, the blow mould, in which it is then blown into its final shape.

Motivation

Important Characteristics of the Model

• Full 3D model
• Two free interfaces
• Contact glass/mould (thermal and mechanical conditions change when glass touches the mould)

Equations

Glass can be considered as an incompressible fluid. The resulting momentum and mass conservation equations are

 with μ the viscosity, v the velocity, Re the Reynolds number, Fr the Froude number, g the gravitational forces and p the pressure.

Pseudo Concentration Method

The Pseudo Concentration Method is used to define where glass and air are located. The concentration c is a continuous function with values between 0 and 1. c≥ 0.5 corresponds with glass and c<0.5 with air. Every timestep is transported by:

The viscosity now depends on the concentration:

where μ_glass depends on the temperature.

Test Problems

2D example to test the Pseudo Concentration Method.

The same test is performed on a (quarter of a) circle. For this problem there exists an analytical solution of the position of the inner interface. We compared this with the numerical results.

Analytically and numerically calculated radius r as function of time t.

Conclusions

The Pseudo Concentration Method seems suited for this problem, but needs some improvement. For instance (local) mesh refinements, or local modifications of the basisfunctions (Discontinuous Galerkin or Immersed Interface Method).