Drilling Parameters and Their Effect on Chip Clogging and Surface Roughness

Abstract

In the woodworking industry, drilling (boring) is one of the most extensively used processes. Due to the traditional nature of the woodworking industry, not much data on machining has been recorded, only a fraction of this on drilling. This lack of information hinders the understanding and thus improvement in the process of drilling. The objective of this research is to provide a pilot study on chip clogging and the surface finish generated while drilling wood and also to examine the surface breakout at the point of drill entry and exit while drilling. This will help the industry by giving an insight into the drilling of wood for furthering research in focused areas. Experiments on chip clogging were carried out with two sizes of standard twist drills and the effect of feed (in/rev), spindle speed (rpm), passage of air jet, pecking cycle and rotational tool were studied on chip clogging. For the study of surface finish, a full factorial experimental design was implemented to evaluate the effect of factor level combinations of four wood types, four drill types, grain directions (along and across the grain), spindle speed (rpm) and feed (in/rev) and their interactions with respect to the surface quality of the machined workpiece. These 128 factor level combinations were replicated three times for a total of 384 experiments. The data obtained was statistically tested by using the analysis of variance techniques to prove the level of significance for each factor and interaction with respect to the surface finish. Work on chip clogging shows promise and needs further investigation for the benefit of the industry. Results on the surface finish study show trends in the behavior of parameters and future work should include developing mathematical models for accurately predicting responses with respect to the input parameters.