Abstract
In this study, the technique of drilling at stepped feed rate is suggested as a new method for reducing the burr size at the exit of a hole in Al-5005, without prolonging the drilling time. The hole was divided into two regions, which were drilled at different feed rates. As a reference for comparison analysis, Al-5005 was drilled at constant drilling parameters. The smallest burr size with constant drilling parameters was obtained at 140° point angle, 0.1 mm × rev−1 feed rate, and 400 rpm spindle speed. The parameters that mainly effect the burr size were determined to be point angle, feed rate and the spindle speed, respectively. The same material was drilled employing the method of stepped feed rate, where the first region of the hole was drilled at 140° point angle, feed rates of 0.1, 0.2, and 0.3 mm × rev−1, and spindle speeds of 400, 800, and 1200 rpm. The second region was drilled with a feed rate that was automatically adjusted by the CNC machine to be one tenth of the feed rate in the first region, without removing the drill bit from the hole. It was observed that, using the stepped feed rate method, the burr height and burr thickness were diminished by 35 % and 25 %, respectively, compared to constant drilling parameters.
Kurzfassung
In der diesem Beitrag zugrunde liegenden Studie wird ein neues Verfahren mit einer schrittweisen Vorschubrate empfohlen, um die Gratgröße des Austrittsloches in Al 5005 zu reduzieren, ohne die Bohrzeit zu verlängern. Das Loch wurde in zwei Regionen unterteilt, die mit verschiedenen Vorschubraten gebohrt wurden. Als Referenz für vergleichbare Analysen wurde Al 5005 bei konstanten Bohrparametern gebohrt. Die niedrigste Gratgröße ergab sich bei konstanten Bohrparametern bei einem Spitzenwinkel von 140°, einer Vorschubrate von 0.1 mm pro Umdrehung und einer Spindelgeschwindigkeit von 400 U × min−1. Als effektivste Parameter bezüglich der Gratgröße wurden entsprechend der Spitzenwinkel, die Vorschubrate und die Spindelgeschwindigkeit ermittelt. Derselbe Werkstoff wurde gebohrt, indem eine schrittweise Vorschubrate angewandt wurde, wobei die erste Region mit einem Spitzenwinkel von 140°, Vorschubraten von 0,1, 0,2 und 0,3 mm pro Umdrehung und Spindelgeschwindigkeiten von 400, 800 und 1200 U·min−1 gebohrt wurden. Die zweite Region wurde mit einer Vorschubrate gebohrt, die automatisch mittels einer CNC-Maschine auf ein Zehntel der der Vorschubrate der ersten Region angepasst wurde, ohne das Bohrwerkzeug von dem Loch zu entfernen. Es wurde beobachtet, dass die Grathöhe und die Gratdicke mittels des Verfahrens mit schrittweiser Vorschubrate um 35 % bzw. 25 % im Vergleich zu den konstanten Bohrparametern abnahmen.
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