Helical Drill Point Research Articles

Grinding process of helical micro-drill using a six-axis CNC grinding machine and its fundamental drilling performance

Helical drill point is characterized by a continuous helical flank surface and an S-shape chisel edge, and its special geometry contributes to a superior drilling performance and a better grinding efficiency. However, the existing grinding processes are complicated and hard to be reproduced in practice, and it is difficult to meet the accuracy requirements as the drill diameter becomes smaller. Thus, it is crucial to research further grinding method of helical micro-drill and its drilling performance. In this paper, a grinding method of helical drill flank using a six-axis CNC grinding machine is proposed based on the mathematical model of generatrix of the helical surface. Then, this grinding process is simulated using the 3D CAD software and is validated by experimentally fabricating the helical micro-drill. The results show that this method is feasible for obtaining the micro-drill with high dimensional accuracy. For the comparison with helical micro-drill, the planar and conical micro-drills with the same geometry parameters are produced as well. The drilling experiments on 1Cr18Ni9Ti austenitic stainless steel with the planar, conical, and helical micro-drills are conducted, and the drilling force, tool wear, and hole quality are measured and analyzed. The experiment results show that the increasing rate of the radial force of helical micro-drills at the beginning of the drilling process is smaller than those of planar and conical micro-drills, the thrust force and wear of helical drill point are also smaller, and the quality of micro-holes by helical drill point is better as well. It is confirmed that the proposed grinding process is effective to fabricate the helical micro-drill with good drilling performance.

Optimization of Grinding Parameters for Drill Points with a Biglide Parallel Machine Based on Genetic Algorithm

In viewof helical drill point grinding,the theoretical and experimental bases for grinding the required geometrical parameters of helical drill points are presented in this paper based on the optimization of biglide parallel machine grinding parameters. A method of grinding the involute helical surface based on the biglide parallel machine is introduced, and then the mathematical model is derived for the helical drill flank. Moreover,the relationship between the geometric parameters and grinding parameters is analyzed,and the optimal grinding parameters are acquired based on genetic algorithm. The results showed that the optimized grinding parameters improve the grinding precision with the experiment on the biglide parallel machine,and the biglide parallel machine can satisfy clients' demands of drill grinding.

A practical optimization design of helical geometry drill point and its grinding process

Drill with helical geometry drill point was developed to avoid the disadvantages of planar drill. For the visualization design and optimization of helical drill, a numerical modeling and simulation CAD system has been developed based on the mathematical models of helical drill. The characteristics of helical drill, such as lip clearance angle along cutting lip, heel clearance angle along flank surface, cutting edge inclination angle, rake angle, and so on, are described. Therefore, drill geometric parameters are modified reasonably according to different drilling requirements by the aid of the developed CAD simulation system. Besides, grinding parameters are obtained to guide the flank grinding process of helical drill. A case has been given to demonstrate the function of the system. And the calculated grinding parameters in the above case have been applied on a five-axis CNC grinding machine RollomΛtic 620XS with an assistant fixture to accomplish the flank grinding process. Drill geometry of ground drill shows good agreement with the simulative one, which validates the accuracy of proposed model method and relative CAD system.

Study on Complex Helical Drill Grinding Using the Grinder with Tripod Parallel Universal Moving Platform

It is necessary to develop complex helical drill point grinders in order to improve drilling quality and efficiency. In this paper, a new type of cutting tool grinder in which there is the tripod universal moving platform is developed, and complex helical drill grinding using the grinder is presented. In addition to complex helical drills, other cutting tools also can be ground using the grinder.

Study on the Effects of the Geometrical Parameter of Twist Drill on the Drilling Performance of Stainless Steel

The key geometrical parameters of twist drills that had a great effect on the drilling performance of stainless steel were studied by Pro/E and DEFORM-3D softwares. The influence of chisel edge and tip angle of twist drill on the drilling force, torque and tool wear in the drilling process was researched, and meantime the effects were introduced by shortened the chisel edge length or adopted S-shape helical drill points as well. The tip angle of drill bit that affected the main cutting edge length, the cutting load on unit length, the proportion between cutting width and cutting thickness in the cutting lay, the cutting force, the torque, the chip formation and chip removal was introduced in detail. The choice of tip angle of twist drill was introduced. In drilling, it has important instructional significance for improvement of life of drill bit, advancement of productivity of drilling and processing quality of hole.

Research on a Helical Drill Point Grinding Machine

It is necessary to develop drill point grinders in order to improve drilling quality and efficiency. In this paper, a new type of helical drill point grinder is presented. This grinder is mechanically simple, low cost and easy to be used. There are three axis simultaneous motions by means of two cams during helical drill point grinding process. Moreover, the relationships between the helical drill point parameters and helical grinding parameters are derived. As a result, the flank surfaces of helical drill points are described.

Study on Helical Drill Point Grinding with a Biglide Parallel Grinder

With the raising demand of the manufacturing technology and productivity in recent year, many new type drills, such as helical drills, have been developed. However, three axis simultaneous motions of a cutting tool grinder at same time are needed when helical drill points are ground. In this paper, a biglide parallel grinder is presented. During helical drill point grinding process with this biglide parallel grinder only two axis simultaneous motions are required. Moreover, the relationships between the helical drill point parameters and helical grinding parameters are derived. As a result, the flank surfaces of helical drill points are described.

Mathematical Modeling of a Complex Helical Drill Point

Helical drill points provide a superior cutting performance, particularly when drilling microholes. Complex helical drill points retain the advantages of conventional helical drills while providing a further strengthening of the cutting edge. However, no methods currently exist for systematically modeling drills of this type. The proposed method has three distinct features. First, the mathematical model of the complex helicoid grinding surface enables the normal and tangential vectors of the abrasive wheel to be explicitly derived. Second, the mathematical models of the flute and flank surfaces are integrated, and thus the cutting edges and chisel edges can be obtained using a simple numerical calculation procedure. Finally, the derivation of the model is straightforward and expresses the drill’s characteristics (e.g., the chisel edge, the lip clearance angle, the heel clearance, the normal rake angle, and the normal clearance angle) in accordance with International Organization for Standardization standards. When integrated with appropriate computer numerical control (CNC) software, the modeling approach presented in this study provides a powerful tool for the design and manufacturing of complex helical drill points with a variety of geometrical designs.

Modal Analysis of a Biglide parallel NC Grinder for Helical Drill Point Machines System Based on ANSYS

The parallel kinematic machines have broad application prospects in the manufacturing industry. Good dynamic characteristics are needed for the structure, which has direct influence on working efficiency, stability and reliability. ANSYS software analysis of their dynamic characteristics is accurate and easy, and can quickly modify the design fault and reduce design cost. In this paper Pro/Engineer is used to draw the solid model of PKM and assembly each part to constitute a system. At last the whole system is imported into ANSYS. The finite element model is established with the simplified model and element equivalent simulation, and modal analysis is conducted using model vibration theory and finite element theory. After the vibration deformation analysis of whole system, the weak parts, i.e. each bearing joint and the power transmission chains, are identified. The weak parts can then be enforced to improve the dynamic characteristics of the whole system.

Effect of Helical Drill Points on Delamination in Drilling Carbon Fiber Reinforced Plastics (CFRP)

A study of helical drill points for drilling carbon fiber reinforced plastics (CFRP) is presented. A helical drill point has an “S” contour with a radiused crown chisel that reduces the thrust force and make the drills self-centering. The S-shape chisel edge has a lower negative rake angle than a conventional chisel edge, and therefore may cut rather than extrude material. Experiments of drilling CFRP with helical drill points and conventional drill points were conducted. The results indicate that the helical drill points can reduce delamination significantly as compared to the conventional drill points under same cutting condition. Otherwise, delamination size decreases with increasing the cutting speed and increases with increasing the feed

Computer Aided Design and Grinding for Helical Drill Points

In this paper, a Drill Point Simulation System (DPSS) which is being developed at Northeastern University is presented. By means of DPSS, the geometric models of the helical drill points were shown after inputting their design parameters. Then, the grinding parameters of the helical drill points were produced. According to the grinding parameters, the helical drill points were ground by the SD helical drill point grinder which was developed at Northeastern University. Furthermore, drilling tests were performed on aluminum sheet workpieces to investigate drilling performance of the helical drill points. In addition, the relationships between the geometric parameters of helical drill points and their grinding parameters also were derived.

Dynamic Analysis of a Biglide Parallel Grinder

In this paper, the moving platform of the biglide parallel grinder with six degrees of freedom will keep moving horizontally at any time using parallelograms. Besides grinding the helical drill point, this grinder also can work as drilling and welding machine tool as well as a CMM. The joint-velocity Jacobian matrix is calculated. Moreover, the dynamic equations are derived by applying the Lagrangian formulation.

Parameterized Geometric Design for Complex Helical Drill Point

This paper presents the design method for complex helical drill point. Different from the conventional helical drill point generated by simultaneous rotation and translation of the drill blank, the complex helical drill point is ground by a supplementary swinging. Associated with these movements a series of grinding parameters are defined. There is another set of structural parameters, characteristic values (chisel angle, point angle, and clearance angle) manifesting the behavioral requirements of a drill. Relationships between these two sets of parameters are shown in curves. In accordance with drilling requirements, appropriate grinding parameters can be selected. The reliability of the proposed method is verified by drill point grinding experiment and measurement.

Mathematical model for helical drill point

Helical drill points provide a superior cutting performance in drilling operations, particularly in micro-hole drilling. This paper presents a comprehensive and straightforward method for the design of helical drill points. The proposed method has three particular features. Firstly, a mathematical model of the helicoid grinding surface is developed. This model allows the normal and tangential vectors of the abrasive wheel to be obtained explicitly. Secondly, the mathematical models of the flute and flank surfaces are integrated and therefore the cutting and chisel edges can be obtained by numerical calculation. Finally, the derivation of the model is straightforward and expresses the drill's characteristics (e.g. the semi-point angle, chisel edge, lip clearance angle, heel clearance, angle tool cutting edge inclination, normal rake angle and normal clearance angle) in accordance with all current international standards. The proposed model is capable of describing a wide range of helical drills. The methodology presented in this study facilitates the production of helical drills on a 6-axis CNC grinding machine.

Curved helical drill points for microhole drilling

The ubiquitous microdrills with planar point geometry used by industry suffer from a number of undesirable characteristics and limitations that influence their drilling performance with respect to hole quality and tool life. In this paper, a new family of drill points, the ‘curved helical drill points’, and the related grinding methods for their manufacture are introduced to alleviate the undesired characteristics and limitations of planar drills. The mathematical foundation and an analytical and graphical comparative drill point geometry analysis between curved helical drill points, linear helical drill points and planar drill points are presented.

A Mechanistic Model to Predict the Cutting Force System for Arbitrary Drill Point Geometry

A mechanistic model is developed to predict the forces for arbitrary drill point geometry. The cutting lips are divided into elements and the elemental forces are determined from a fundamental oblique cutting model. A method is developed to parametrically define the cutting lip in three-dimensional space and to determine the oblique cutting parameters (cutting angles and chip thickness) at each element on the cutting lip. The model does not require calibration experiments for each point geometry. The conical drill is used to determine the model coefficients for a tool and workpiece material combination and these are used for other drill point geometry. Model simulations match experimental data very well for four commercial drill point geometry—the Racon, Helical, Bickford and Double angle drill points.

Helical Micro-Drill Point Design and Grinding

A new drill point geometry, termed the helical drill point, specifically intended for micro-drills, is developed in order to alleviate the disadvantages of existing planar micro-drill points. A mathematical model for this new drill point has been established. It is shown that this model is more general than existing drill point models. The commonly used conical, cylindrical and planar drill point models are only special cases of the helical model. For uniquely determining the grinding parameters of the new drill point as well as guiding the grinder design, the characteristics, the controllability and the sensitivity of the grinding parameters have been analyzed. Finally the geometric characteristics of this new drill point are investigated.