Ceramics-Silikáty 51, (2) 119 - 124 (2007)

Critical stresses in glass created during and after pressing process are one of the concepts explaining glass damage in stemware production. Applicability of stress calculation in glass is investigated in real production process simulation with two main objectives: (i) to find critical product locations with high tensile stresses and (ii) to correlate them with responsible process steps. Simple thermo-elastic glass model without relaxation was adopted in a finite element method (FEM) computation on a 16-position carrousel system. Process simulation was finished before the product achieved annealing lehr. High tensile stresses were identified on the product bottom edge, where the glass touches the transport belt or the neighbouring product. This finding was in a very good correlation with observed defect called "cracked bottom" starting on the bottom edge already before entering annealing process. The presented modelling approach can be used for heat transfer optimisation during pressing and post pressing processes on the carrousel.