Fundamental investigations on micro single-lip deep hole drilling of challenging drilling situations
Final Report Abstract
When producing deep bore holes, the tools have low rigidity due to the high length-todiameter ratios and are typically designed asymmetrically. They therefore require a drill guide in the form of a drill bush or pilot hole at the start of the drilling process. The tools support themselves by circumferentially arranged guide pads in the drill guide and in the further course of the drilling process on the bore hole wall, thus enabling the production of highquality bore holes with a low center deviation. Particularly in the case of complex components with inclined and curved surfaces as well as those having surface-hardened areas, the production of pilot holes is very time-consuming or specially adapted drill bushes are required. As the laser beam is not deflected at the surface, laser drilling enables the wear-free drilling of pilot holes on hardened and complex-shaped surfaces. In additive manufacturing, i.e. through selective laser beam melting, pilot holes can also be integrated directly into the manufacturing process of the component. The aim of the project was therefore to significantly shorten the conventional process chain for deep hole drilling in complex drilling situations by substituting face milling and mechanical pilot hole drilling with the laser pilot hole drilling process or the direct integration of the pilot holes into the component. In extensive investigations into the generation of laser pilot holes using a single pulse, process parameters for pilot holes with a diameter of d = 0.5 mm were identified for the materials X2CrNiMo17-12-2 and 20MnCr5. These parameters were successfully used in the process combination of laser pilot hole drilling and single-lip deep hole drilling. When creating larger pilot holes (d = 1.5 mm), the flexibility could be significantly increased by helical laser drilling with a large number of laser pulses along a defined CNC-controlled path. The solidification of the molten material (recast layer) on the bore hole wall in the area of the laser pilot hole resulted in a lower bore hole quality compared to mechanically produced bore holes. The analysis of additively manufactured pilot holes showed that the guide pads lead to a leveling of the roughness in the pilot hole from the additive process, resulting in diameter deviations in this area. By using step drills with a first diameter step for threading and guiding the tool in the (laser) pilot hole and a second larger diameter step for machining the entire bore hole surface, it was possible to achieve bore hole qualities that are comparable to the conventional process chain.
Publications
-
Mikroeinlippentiefbohren bei anspruchsvollen Anbohrsituationen. Unter Span, 1 (2017), S. 23
Biermann, D.; Kirschner, M.; Michel, S.Biermann, D.; Kirschner, M. & Michel, S.
-
Am Anfang ist das Licht. WB Werkstatt + Betrieb, (2018) 1/2, S. 64-67
Michel, S.. & Biermann, D.
-
Analysis of the laser drilling process for pilot holes in complex shaped components. Procedia CIRP, 74(2018), 398-402.
Michel, Sebastian & Biermann, Dirk
-
Mikrotiefbohren mit Laserpilotbohrungen*/Micro drilling with laser pilot holes - Laser pre-drilling as guidance for deep hole drilling in demanding surface geometries. wt Werkstattstechnik online, 108(01-02), 76-80.
Michel, S. & Biermann, D. Prof.
-
Experimental investigations of a helical laser drilling process for pilot holes on complex surfaces. Lasers in Manufacturing Conference 2021
Michel, S.; Volke, P. & Biermann, D.
-
Experimental investigations using a single pulse and a helical laser drilling process for pilot holes on complex surfaces. Vortrag EUROMAT 2021, 13.-17.09.2021
Michel, S.; Volke, P. & Biermann, D.
-
Investigation of Laser Drilled Pilot Holes and Additively Generated Pilot Holes as Drilling Guides for Single-lip Deep Hole Drilling. SSRN Electronic Journal, 2021.
Michel, Sebastian; Volke, Pascal & Biermann, Dirk
-
Laserpilotieren und Einlippentiefbohren kombinieren. VDI-Z, 164(09), 58-61.
Volke, Pascal; Michel, Sebastian & Biermann, Dirk
