Burr reduction method in microdrilling of metal sheets by Poly Methyl Methacrylate (PMMA) coating

The manufacturing of a through bore-hole is characterized by the formation of an entrance and an exit burr that surrounds the hole and affects its function ability. In particular, the exit burr degrades the quality of parts and causes troubles when the parts are assembled so a deburring process is necessary. Problems arise when manual deburring, which is often used in the conventional size level, is very difficult to apply and a chemical deburring process is not suitable because it can distort the hole shape. In this paper a preliminary research about a burr reduction technique is presented: a coating was applied, before the machining, on the upper and lower surface of a metal sheet. After the microdrilling a cleaning process was executed to eliminate the coating and a hole with less burr is obtained. An experimental campaign was executed to measure the effectiveness of the technique as a function of different metal sheets, tool drill diameters and thickness of the coated layer.