Edge Strength of Annealed Float Glass: Influence and Optimization of Cutting Process Parameters

Abstract

The desire to apply annealed float glass with their economic and optical advantages is limited by the reduced edge strength due to the cutting process. The edge strength of annealed float glass is a decisive factor especially for insulating glazing due to temperature stress. In standards (e. g. DIN EN 18008), the edge strengths are reduced compared to the surface strength of annealed glass. This is mainly a result of the applied cutting process with the corresponding parameters and the glass handling after cutting. The type of cutting process and the cutting parameters (cutting wheels, etc.) have an effect on the development of micro cracks and thus also on edge strength. A defined cutting process allows reproducible and enhanced edge strength. This paper presents results of destructive and non-destructive investigations with regard to the edge strength. For the investigations, glass panes were cut on an industrial cutting machine with various process settings. Among other things, the following cutting parameters were varied: type of cutting wheel, cutting pressure, cutting speed and cutting fluid. In addition to the process parameters, different basic glasses, glass thicknesses and the cut process on the tin side were also investigated. The samples were examined with the aim to determine the correlations between the cutting process / glass parameters, the edge strength and the micro crack geometry and optimize the parameters. The destructive tests were carried out primarily with a modified four point bending test, but also with the standard four point bending test according to DIN EN 1288-3.