Laser cutting of float glass during production

Abstract

Studies were conducted to determine the strength and thermal stability of samples of glass with edges obtained by cutting a moving ribbon of float glass by mechanical and laser cutting. The advantage of laser cutting was demonstrated.Brittleness is a problem in using sheet glass. The weakest part of the glass sheet is the edges due to the large number of gross stress concentrators that remain in the edges after cutting the moving ribbon and keeping the degree of its hazardousness unchanged over the entire time of shipment, storage, and use of the glass [1].Mechanical cutting (as the simplest and most accessible) is used in continuous production of sheet glass; it consists of making a median crack with a hard-alloy roller. In order to obtain a quality edge, i.e., a defect-free edge and smooth, shiny end with perpendicular surfaces, the optimum cutting parameters must be rigorously observed. Otherwise, the edge will have a coarse shape with a large number of chips and pits. The transverse bending strength and thermal stability are quantitative criteria for evaluating the quality of the glass edge.Mechanical cutting reduces the strength of the glass by 60% on average. The strength of such glass can be increased by treating the edges. The most common method is mechanical (grinding followed by polishing). However, the strength of the glass increases by approximately 30% [2].A laser cutting unit (Fig. 1) for separating the edges from the moving glass ribbon has now been introduced in the ÉPKS-4000 float line (Saratov Glass Institute Co.). The method of controlled thermal cleavage is used in the unit, and it essentially consists of projecting the beam of a molecular gas CO 2 laser, which provides for local heating (to 350 -450°C) of the cutting line, and feeding an air-water mixture under pressure on the surface of the glass. As a result of the temperature gradient that arises at a small depth from the surface of the glass, a microtrack is formed and causes separation.The edge is separated after the glass ribbon is transversely cut into sheets of the required length with edge cutters. The ends of samples obtained after laser and mechanical cutting of a float-glass ribbon are shown in Fig. 2.The qualitative evaluation with a MIN-8 (´50) microscope showed that both ends are smooth and shiny. However, although a defect-free edge is obtained after laser cutting,

Modern sheet-glass cutting technologies

“…Cutting with a CO 2 laser has been successfully adopted in the Saratov Glass Works for transverse cutting of a float-ribbon [8].…”

Abrasive waterjet micro-piercing of borosilicate glass

“…Excessive heat generation and tool wear can develop as a result of friction between the tool and glass, resulting in material damage. For example, Zhimalov et al (2006) have shown that mechanical cutting of glass reduces the strength of glass by 60% on average. In the mechanical drilling of soda-lime glass plates using a micro-drill bit, Park et al (2002) found the amount of glass chipping on the exit side of the hole could be reduced by using a supporting glass plate.…”

“…For example, Zhimalov et al (2006) demonstrated that cutting glass using LBM could produce better results than traditional mechanical methods. Machulka et al (1972) cut glass with a CO 2 laser, and proposed a theoretical cutting rate model.…”

Comparison of ANN and finite element model for the prediction of thermal stresses in diode laser cutting of float glass

“…In such methods, the cutting-edge of the glass could weaken up to 60% due to the formation of micro-cracks and residual stresses [1]. This also makes the glass vulnerable with time as crack usually grows from these weaken edges.…”