The drilling process – an approach to improvement and better understanding

Michael Emonds & Djomka Hartmann, Aachener Chemische Werke & P.-H. Kroehs & A. Barth, BOHLE AG & Arto Kaonpää, Glaston Services Ltd. Oy

The drilling process is a decisive step in both automotive glass and architectural glass processing. Holes facilitate mounting and transfer of mechanical loads such as those induced by impact and vibrations and thus give additional value to the glass. But it is well known that the presence of a hole results in stress concentration which reduces the
strength and load carrying capacity of plate in the vicinity of the hole. The hole edge strength is lowered by the flaws associated with drilling the hole, i.e. finishing quality of the hole. The latter, of course, depends on factors like drill quality, drill size and speed, feed rate, type of coolant used.

The key objective of this paper is to quantify the effect of spindle speed Vc, feed rate Vf and especially the coolant by measuring feed force F when drilling 26 mm holes into 8 and 10 mm thick float glass plates on a Bohle drilling machine. Additionally, 20 cm x 20 cm x 3,8 mm thick float glass plates with center holes of 26 mm are drilled and feed force F as well as the biaxial strength are measured. The strength measurements are carried out by flexing the glass plates in a ring-on-ring fixture. The effect of a synthetic coolant at different concentrations (3 and 6%) and water is quantified by measuring the strength. The aim of this investigation is to minimize feed force F applied by the drill in order to decrease the drill stress thus minimizing the severity of flaws and maximizing biaxial strength in the vicinity of the hole.

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The Authors

Dr. Michael Emonds Specialist ACW Dr. Michael Emonds is a skilled specialist in preprocessing of glass. He has worked for Aachener Chemische Werke (ACW) since 1993. His knowledge comprises cutting fluids, coolants and interleavants as... Read more