TUC 3m Lab
m3 Drlinng



Twist drills are geometrical complex tools and thus various researchers have adopted different mathematical and experimental approaches for their simulation. The present research acknowledges the increasing use of modern CAD systems and subsequently using the API (Application Programming Interface) of a typical CAD system, drilling simulations are carried out.


The developed DRILL3D software routine, creates, via specifying parameters, tool geometries, so that using different cutting conditions,  realistic solid models are produced incorporating all the relevant data involved (drilling tool, cut workpiece, undeformed chip). The 3D solid models of the undeformed chips coming from both cutting areas (main edges and chisel edge) are segmented into smaller pieces, in order to calculate every primitive thrust force component involved with high accuracy.





The resultant thrust force produced, is verified by adequate amount of experiments using a number of different tools, speeds and feed rates. The final data derived, consist of a platform for further direct simulations regarding the determination of tool wear, drilling optimizations etc.













The accuracy of the DRILL3D drilling simulation model in calculating the thrust force was verified executing a series of experiments on a HAAS 3-axis CNC machine center with continuous speed and feed control, using a CK60 plate as the specimen. A Kistler type 9257BA three component dynamometer was positioned between the machine center and the work piece. The signal was processed by a 5233A control type unit and during the tests, the thrust force was displayed graphically on the computer monitor and analyzed so as to enable early error detection and ensure steady state condition.





For FEM analysis, the necessary force distribution along the cutting edges, separately for each one of the edges involved, was provided by the DRILL3D. Those forces were transferred to the FE model following a two step approach: First, the forces from the DRILL3D were directly distributed on the nodes of the cutting edges. Second, the elementary forces FN applied on the nodes of the cutting edges were further distributed on the appropriate nodes that reside on the rake face of the tool and close to the cutting edge.







Next figure depicts the maximum Von-Mises stress developed along the chisel edge and the main edges for a number of tool diameters (12mm, 14mm and 16mm) and web to diameter ratios (0.13 and 0.15), when the feed rate is 0.3mm/rev and the cutting velocity is 20mm/min. As the tool diameter increases, for the same cutting conditions, the level of the maximum stresses decreases. Additionally, the increase of the web to diameter ratio results in the decrease of the developed maximum stress for all cases. In all simulations, the increase of the available contact area when the drilling tool engages the workpiece, explains the reductions in the Von-Mises maximum stress calculated.


                                                                                             Technical University of Crete      School of Production Engineering & Management      e-mail