CNC Tool Grinder Research Articles

Research on Adaptive Control of Grinding Force for Carbide Indexable Inserts Grinding Process Based on Spindle Motor Power

The grinding force is the most sensitive physical measure of reaction loads in the grinding process. To enhance surface quality and assure high efficiency and stability of the grinding process, it is essential to accomplish adaptive control of the grinding force. This paper suggests a grinding force adaptive control system based on spindle motor power feedback, considering the process–machine interaction. The spindle motor power is utilized as a proxy for the grinding force because of the mapping relationship between the two variables. The machine tool’s feed rate is automatically modified to achieve adaptive control of the grinding force, after assessing the discrepancy between the collected spindle motor power and the preset power. Finally, a cemented carbide tool grinding experiment was performed on a 2MZK7150 CNC tool grinder. During the experiment, the grinding force was precisely controlled between 80 and 100 N, ensuring machining quality and increasing machining efficiency. The experimental results show that the adaptive control system can meet the high-efficiency and high-quality machining requirements of cemented carbide rotary blades.

A compensation algorithm of tool path for grinding wheel wear in solid cutting tool flank grinding

In finishing machining, the quality of workpiece is significantly influenced by the performance of solid cutting tool. Solid cutting tool flank is ground by CNC tool grinder in accordance with the tool path of grinding wheel. In actual grinding process, the grinding area of wheel will be gradually worn down, resulting in the decrease of geometric accuracy of flank and even wrong profile. In order to compensate the error, a compensation algorithm of tool path for solid cutting tool flank based on grinding wheel wear is proposed. Firstly, the coordinate systems are defined for the grinding process of flank, and the orientation and location calculation model of ideal wheel with the grinding process parameters is derived. Secondly, based on the profile description of wheel wear, flank errors are analyzed. Then, the compensation algorithm for anastomosis of cutting edge and relief angle is proposed. Finally, series of experiments of simulation and actual grinding are carried out. The comparison of the results shows that the algorithm can reduce the influence of wheel wear effectively, which can also improve the grinding quality stability and prolong the service life of grinding wheel.

Structural design and fabrication of polycrystalline diamond micro ball-end mill

Since cemented carbide has been used as a micro-lens array mold, its processing method and micro-tool is one of the research priorities. In order to achieve high-quality milling of cemented carbide micro-lens array, the design and fabrication of the 0.5-mm diameter polycrystalline diamond (PCD) micro ball-end mill were studied. Based on the space vector, the mathematical model of the plane cutting edge of the PCD tool is established. According to the three processing characteristics of milling, grinding, and milling grinding, the double-edged conical surface micro ball-end mill, spherical micro ball-end mill, and single-edged hemispherical micro ball-end mill were designed respectively. Based on the line-face contact model of the grinding wheel and the movement principle of the CNC tool grinder, the grinding principles and methods of the rake face and the flank face are proposed. The high precision grinding of PCD micro ball-end mills are realized. The micro-groove milling experiment of cemented carbide was conducted; the milling performance of three PCD micro ball-end mills was studied. Considering the surface morphology and roughness of the micro-groove machining, a single-edged hemispherical PCD micro ball-end mill can avoid the phenomenon of chip blocking and depositing and can also fully exert the grinding characteristics of PCD materials to obtain relatively better processing quality.

Research on the Drilling Performance of a Helical Point Micro Drill with Different Geometry Parameters.

During the micro-drilling process of stainless steel, the wear, fracture, and breakage of the micro-drill easily occur. Micro-drill geometry parameters have significant influence on the drilling performance of the micro-drill. Nowadays, the helical point micro-drill is proposed and its improved drilling performance is validated by some researchers. In this study, to analyze the effect of geometry parameters of the helical point micro-drill on drilling performance, the mathematical models of the helical flank and ground flute are proposed, and the cutting lip shape, rake angle, and uncut chip thickness are calculated using MATLAB software. Then, based on the orthogonal tests, nine kinds of micro-drills with different point angles, web thicknesses, and helix angles are fabricated using a six-axis CNC tool grinder, and micro-drilling experiments on 1Cr18Ni9Ti stainless steel are carried out. The drilling force, the burr height, and the hole wall quality are measured and observed. The results show that the point angle is the main contributing factor for the thrust force and burr height, and the web thickness is the main contributing factor for the micro hole wall quality. The increased point angle offers a larger thrust force, but gives rise to a smaller exit burr. A larger web thickness leads to a larger thrust force and burr height, and results in a poor surface quality. With the helix angle increased, the thrust force and burr height decreases, and the surface quality of micro-hole improves. The geometry parameters with a point angle 70°, a point angle of 40°, and web thickness ratio of 0.2 can used to improve the drilling performance of the helical point micro-drill.

The Grinding and Test of Annular Milling Cutter with Double-Circular-Arc

For the problem of the non standard cutter shape cutting edge not smooth transition connection and flank face of cutting tool grinding precision difference, the influence of wheel deformation is analyzed to different grinding linear speed, and the grinding wheel deformation error compensation grinding method is studied in this work. The grinding of annular milling cutter with double-circular-arc is processed in five axis CNC tool grinder. Finally the machining precision of annular milling cutter with double-circular-arc is tested by the tool test center, the result show that the wheel grinding method based on compensation of grinding can realize smooth transition in different parts of cutting edge belt of annular milling cutter with double-circular-arc and flank grinding precision is ensured.

Influence of Drill Geometry Parameters on Helical Point Micro Drilling Performance

Helical point micro-drill is characterized by a continuous helical flank instead of the piecewise planar flank, and its improved drilling performance is validated compared with planar drill point by some researchers. In this study, to analyze the effect of geometry parameters of helical point drill on the drilling performance, the micro-drills with different point angles, web thicknesses and helix angles of the flute are fabricated on a 6-axis CNC tool grinder, and a serial of micro-drilling experiments involving these drills on 1Cr18Ni9Ti austenitic stainless steel are carried out. In experiments, the drilling forces are measured and exit burrs are observed. Within a certain range of geometry parameters, thrust force increases with the increase of point angle and web thickness, and the decrease of the helix angle of the flute. The point angle is the main contributory factor for the thrust force followed by web thickness, while helix angle has a moderate effect on the force. Furthermore, poisson burr and rollover burr are generated with different point angles. Based on the results, a good selection of the helical point drill geometry parameters with small point angle, big helix angle and small web thickness are proposed to improve the micro-drilling performance.

A 5-Axis Coordinated CNC Grinding Method for the Flank of a Non-Coaxial Helical Micro-Drill with the Cylinder Grinding Wheel

Micro-drilling become more widely used from precision mechanics to electronics. Nowadays, the main commercial tools are planar point micro-drills. However, that geometry often causes a high thrust force, high temperature, and rapid wear during micro-drilling. Furthermore, it is difficult to adjust the four flank surfaces to accurately intersect at one point, particularly when the drill diameter becomes smaller. To solve this problem, non-coaxial helical drills points have been proposed by some researchers, and is characterized by a continuous helical flank instead of the piecewise planar flank. Its drilling performance is improved compared with planar drill point. This study presents a 5-axis coordinated CNC grinding method of the non-coaxial helical drill flank. Mathematical models of the drill flank and its engagement line between cylinder grinding wheel and drill tool are established, and then the path of the grinding wheel with respect to the drill tool is obtained. In order to verify the availability of the proposed methods, three dimension (3D) grinding simulation of non-coaxial helical drills with diameter 0.5mm was carried out using the CAD software, and then were fabricated on a 6-axis Makino CNC tool grinder. The ground micro-drills examined by 3D laser scanning microscope show good identity with the simulated result. These indicate that the manufacturing model presented in this paper provides a practical and efficient method to grind the flank of a non-coaxial helical micro-drill.

Research on CNC Grinding Program of Overall End Milling Cutter

With high precision special rotary tool is widely used in automotive, mold, aerospace, machinery, electronics and other fields, the demand of manufacturing for such type and quantity of cutting tool is more and more big, lead to the demand for multi-axis CNC tool grinder which provides efficient, high quality production support for it also increasing. In terms of hardware and software multi-axis CNC tool grinder in developed countries are relatively mature, but domestic did not have enough for this research, especially for development of CNC tool grinding machine operation software system, and rarely reference data. In view of the domestic manufacturer in urgent need of independent research and development of CNC tool grinder, this article will research tool grinding automatic programming and simulation technology of CNC tool grinding machine operation software system, through analyzing the four main steps of NC grinding four-blade overall end milling cutter, parametric programming with MATLAB, and grinding trajectory data in the form of mixed programming of MATLAB and VC+ + will be post processed into NC programs, then simulation in VERICUT virtual machine tool, finally the actual grinding out overall end milling cutter.

Parameter Optimization of a Five-Axis Tool Grinder Using Grey Relational Analysis

This paper uses the grey relational analysis to find the optimal values of parameters of the servo drives and the controller of a five-axis CNC tool grinder in order to improve precision of grinding and accuracy of end mills. The experimental planning and design are based on the Taguchi method. There are totally six control factors in the experiments, and each factor has three levels. An L18 orthogonal array was applied for the experiments, and each experiment was repeated three times. The grey relational approach was then employed to find the optimal values to the drives and the controller. These values were utilized for grinding a ball nose end mill of cemented tungsten carbide with two-flute and 6 mm in outside diameter. Finally, a well-known tool measuring and inspection machine was used to measure the geometric parameters of the end mill for the initial design and the optimal design. Experimental results show that the grinding time is reduced up to 6.02 ％, and the precision of the ball nose end mill is also improved. Thus, the results demonstrate the effectiveness of the proposed approach.

The Predictive Model of Surface Roughness and Searching System in Database for Cutting Tool Grinding

Due to the rapid development in recent cutting technology, demands for different types of precise cutting tools become increasingly complicated. Since the design and grinding of end-mills are the last and the most important processing for cutting tools. The geometrical accuracy and the cutting performance of an end-mill depend essentially on the grinding. However, the complicated geometry of an end-mill will be ground by the specific software of CAD/CAM on the 5-axis CNC tool grinding machine. The precision of end-mill grinder will be determined by the performance of 5-axis CNC tool grinder and setting of grinding parameters. Three regulation factors for grinding are grit size of the diamond grinding wheel, grinding speed and the feeding speed. The variable ranges of each parameter can be divided in large, medium and small interval. In this study for an end-mill with fixed geometrical profile, a series of different grinding parameters have been utilized by the 33 factorial experiment planning. And tool grinding experiments for the rod material specification of tungsten carbide have been performed by 5-axis CNC tool grinder. After grinding, surface roughness of tools will be measured. The reliability and precision of the end-mill grinding can be enhanced by the prediction model of polynomial network for surface roughness of end-mills. Besides, the database system for cutting tool has benn established. Totally 4802 data were constructed in the relational database according to the characteristics of tools.

A novel CNC grinding method for the rake face of a taper ball-end mill with a CBN spherical grinding wheel

A novel method using a CBN spherical grinding wheel to grind the rake face of a taper ball-end mill and the configuration of corresponding CNC tool grinder are presented. This method utilizes the self-adaptation characteristics of a sphere to decrease the number of simultaneous cooperative axes of a CNC tool grinder and to smooth the rake face on the transition area between the taper and the ball-end of the mill. In order to obtain an accurate normal rake angle, which is one of the key factors affecting tool cutting performance, a moving coordinate system based on the required normal rake angle and the cutting edge was established. Then, by the proposed moving coordinate system, an algorithm to determine the position and orientation of a spherical grinding wheel, the basis of CNC code generation, is proposed and the relevant formulations are deduced. The 3D simulation of rake face grinding for a taper ball-end mill with constant helical angle indicates that the number of simultaneous cooperative axes of the CNC tool grinder is decreased from five to four and the smooth transition of the rake face is realized by the proposed method herein.

Planning and analysis of grinding processes for end mills of cemented tungsten carbide

End mills are widely employed in cutting applications, but there is lack of standard grinding process. Thus the main purpose of this paper is to plan the grinding processes of end mills, including approach and retract sequence of each axis, and grinding parameters, etc. A tool grinding CAM system was applied to set appropriate parameters in order to find out the optimal approach and retract distance, and the sequence. In the experiments, a five-axis CNC tool grinder was utilized to grind a square end mill and a ball nose end mill with two flutes to verify the efficiency for the saving of time. Experimental results show that the efficiency was improved approximately up to 40% by the approach and retract time, and the overall machining time, 10%. Therefore, the results demonstrated the effectiveness of the proposed processes for the saving of machining time. They also can be applied to grind different shapes of cutting tools.

Grinding Process Fuzzy Control on CNC Tool Grinder

In order to improve form cutter accuracy in grinding process, a closed-loop control system was designed to accomplish adaptive control of constant force in grinding process. Since it is a complicated dynamic process with severe nonlinear and much stochastic disturbance, fuzzy adaptive controller was used which can adjust parameters online. By measuring grinding force, characteristic information of grinding process was acquired. Regulation factor of feed rate is determined by grinding force ratio, and force deviation and its change rate are used as evaluation indexes. Thus, adaptive control of constant force in grinding process is accomplished. Simulation and tool grinding test indicate that the system has high precision and stability, and reduces cutter error efficiently.