A large number of products are produced using the glass pressing process. Among others TV panels, tableware (dishes, asher, drinking glasses, etc.) or preform for future are blow molding applications (press and blow process). The market constantly demands thinner container walls, lighter objects and better textures making glass production far more complex than the apparent commonality of the produced goods.
The meshless CFD simulation software by NOGRID has been used successfully for the improvement of the glass pressing process for many years. The combination of free surface deformation under the combined effect of the motion of different solid devices (molds, plunger(s), etc.), gravity, the cooling process (mainly due to the heat exchange with the mold and the plunger), the mechanical and thermal detection of the contact between the deforming glass and the moving and still molds despite the thin slit remaining between all these parts, create a better understanding of the subtleties of the glass pressing process. This better understanding quickly leads to tremendous savings in manufacturing costs and time while ensuring a final product of high quality.
Figure 1: Velocity (left) and temperature (right) distribution during pressing a glass cup
Glass pressing is probably the application where the deformations are the largest. In figure 1, the process begins with a sample of glass that becomes a typical cup. During the pressing process, the solver automatically refines the point cloud where this is necessary. Refinements may appear where very large deformations occur or where the geometrical details of the mold require them. Intelligent algorithms automatically refine the grid only where and when this is necessary during the run both in 2D and in 3D. These techniques are especially important when small geometrical details are involved in the final product.
The pressing of glass is limited by two major effects. If the pressing time is large, the cold mold or cold plunger can freeze the flow or generate chill ripples at the glass surface. On the other side, if the pressing time is small, the plunger velocity is very high. In that case the glass could tear apart.
Our CFD software is able to predict such effects and helps designers to find the right geometry for their molds and plungers. Beside the normal flow with Newton's viscous law NOGRID points is also able to run the computation with non-Newtonian materials (also viscoelastic material behavior is included).