Prevention of exit crack in mirco drilling of soda-lime glass

In micro drilling of glass plates, cracks occur at the exit surface. In this work, a back-up glass plate was used to prevent the exit crack. The mechanical lateral constraint was applied to the workpiece and the back-up glass plate to reduce tensile stress near the drill corner. In this way, crack-free holes could be produced. In order to avoid careful fixturing for the mechanical constraint, two glass plates were adhered with various liquids. It is shown that the liquid adhesion of the back-up glass plate without the mechanical constraint is a more effective method to prevent exit crack.