Development history of drill bit and drilling research (2)

For a long time, the main edge of the twist drill has been designed as a straight line. In 1990, Fugelso MA found that because the main edge of the taper twist drill was required to be straight, the back angle of the main edge near the core was too small. If the drill was rotated about its own axis by 5° to 10 before sharpening. °, you can solve this problem, but the main edge will become slightly curved. In the same year, Wang Y regarded the main edge as a curve, and used the polynomial interpolation method to establish the geometric model of the helix front rake face. In 1991, Lin C and Cao Z proposed a comprehensive mathematical model of twist drills suitable for straight and curved edges, using tapered, cylindrical and planar flank faces. In 1999, Ren KC and Ni J proposed the use of binomial to represent the main edge curve of arbitrary shape. The new rake face of the drill bit adopts a new mathematical model, and the vector analysis method is used to establish the sharpening parameters and geometry of the flank face of the quadratic surface. The relationship between the parameters.

2.2 Structural optimization of the drill bit Due to the unsatisfactory cutting performance of the widely used tapered twist drill, people have been working on improving its structure (parameter) and sharpening method, and have proposed more than 200 different drill bit shapes. To improve its cutting performance. Among them, Shi HM et al. proposed a method of controlling the distribution of the rake angle of the main edge by changing the main blade direction, and in 1990 developed a curved edge twist drill that made the front angle of each point on the main edge of the drill bit reach the maximum possible value. In 1987, Lee SJ proposed a method for optimizing the design of the drill bit in order to eliminate the swinging phenomenon of the drill tip during the drilling process under the condition of the bit deflection. In 1995, when Selvamhe SV and Sujatha C studied the deformation of the twist drill, the geometry of the drill bit was optimized by the finite element method, and the optimized structural parameter value (bit diameter 25 mm) which minimized the deformation of the drill bit was: helix angle 39.776 °, the transverse blade angle Ψ = 54 ° ~ 80 °, the front angle 120 °. In 1997, Chen WC proposed a special truncated thick core twist drill with sufficient torsional stiffness and reasonable distribution of the main and chisel rake angles. In 2005, in order to ensure the optimization of the drillability of the drill bit, Paul A et al. proposed a new drill tip model based on the sharpening parameters, and used it to optimize the tapered drill tip, the Racon drill tip and the helicoid drill tip. Minimize cutting forces.

2.3 Calculation of Spiral Groove Truncation and Tool Truncation In 1975, Dibner LG proposed a method to simplify the calculation of the grinding of the spiral grooved grinding wheel, improve the groove machining accuracy and completely eliminate the influence of the diameter change of the grinding wheel. In 1990, Ehmann KF proposed a method for cutting the helical groove machining tool based on differential geometry and kinematics. From 1998 to 2003, Kang DC and Armarego EJA dealt with "positive problems" and "anti-problems" in spiral groove machining ("tool truncation by groove truncation" and "groove truncation by tool truncation") A research was carried out to propose a computer-aided geometric analysis method for the design and manufacture of spiral groove spiral groove.

2.4 Research on Group Drills and Micro Drills In 1982, Shen J et al. established the first mathematical model of group drills. Using this model, one can repeatedly grind a group of drills. In 1984, Chen L and Wu SM studied nine typical group drills, improved the mathematical model of group drills, and provided the possibility of computer-aided design of group drills. In 1985, Hsiao C and Wu SM proposed a specific method for assisting the optimization design of group drills by computer. In 1987, Fuh KH proposed a method for designing and analyzing group drills using a comprehensive quadric surface model and a finite element method. Liang EJ proposed a group-drilling CAD/CAM integrated system based on knowledge base technology. In 1991, Liu TI designed and optimized a group drill for machining machine shaft oiling holes using a two-stage strategy. In 1994, Huang HT et al. derived the formulas for the working angle and the forehead angle of the group of cutting edges, and proposed an accurate geometric model of the group drill considering the transition between the inner and the circular edges. In 2001, Wang GC et al. applied a tilted solid block method to establish a new mathematical model of group drilling, which solved the problem of the uncertainty of the chisel edge geometry existing in the existing model and ensured the machinability of the designed group drill. .

Beginning in 1992, a research team consisting of Lin C, Kang SK, Ehmann KF, and Chyan HC conducted a systematic study of micro drill bits. In 1992, they established a mathematical model of the planar micro-drill tip and proposed the corresponding sharpening method. In 1993, they proposed a mathematical model and a sharpening method for the micro-drilled tip of the spiral surface, and found that the micro-drilled tip of the spiral surface is superior to the commonly used planar micro-drill tip in terms of geometry and cutting performance. In 1997, they pointed out that the spiral micro-drill tip has two advantages compared to the planar micro-drill tip: 1 allows for a larger feed rate under the same working cutting angle distribution; 2 sharpening method It is simpler and less susceptible to sharpening errors. In 2002, they produced a series of drill tips for curved micro-holes with a curved blade.

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