Spindle Revolution Research Articles

Fuzzy-logic control of cutting forces in CNC milling processes using motor currents as indirect force sensors

Abstract A fuzzy-logic controller (FLC) is designed to automatically adjust feed rate in order to regulate the cutting force of milling processes in a vertical machining center. The FLC has a double-loop structure, consisting of the inner PD (proportional-derivative) velocity-control loop for a feed servo and the outer fuzzy-logic force-control loop. Reference cutting forces are well maintained in both numerical simulation and experiments when the cutting-depth profile of an aluminum workpiece (Al6061-T6) is varying step-wise or continuously. In order to replace expensive and impractical tool dynamometers, ac-induction-motor currents in the feed system and the spindle system are analyzed, and then compared as a cutting-force sensor. The bandwidth of both systems are not high enough to sense the cutting dynamics for common spindle speeds. Thus, quasi-static quantities (i.e., average or maximum resultant cutting force per spindle revolution) are compared instead. The spindle-motor current is chosen because quasi-static sensitivity is much higher (i.e., 5.415 × 10 −3 vs. 2.128 × 10 −4 A/N). Reference cutting forces (230 and 330 N) are well maintained when the depth of cut is less than 4 mm.

A study on optimal compensation cutting for an aspheric surface using the Taguchi method

In this research, the optimization of compensation cutting for eliminating the residual form error of an aspheric surface using the Taguchi method was performed. Three parameters of cutting depth, revolution of work spindle, and compensation ratio were considered as control factors, and the experimental trials based on the L 9(3 3) orthogonal array were carried out. Based on the results of analysis of variance, the most significant factor is the compensation ratio having a percentage contribution of 49.37%. Through the confirmation experiment, the rough machining accuracy of 5.81 μm could be significantly improved to 1.53 μm with an improved efficiency of 73.67%. In comparing to the accuracy of 2.60 μm obtained by one of the initial trials, the accuracy efficiency was improved to 41.15%. As presented in this study, the systematic approach to compensation cutting can be applied to various applications of meso-machining or ultraprecision machining works performed by ultraprecision machines.

A PLL Synthesizer with Learning Repeatable Fluctuation of Input Signal

This paper describes a high frequency PLL (Phase Locked Loop) synthesizer with a function of learning then eliminating repeatable fluctuation of timing intervals on series input pulses. Typical spindle encoder generates digital pulses according to the revolution speed. The intervals of each pulse have repeatable fluctuation every revolution by eccentricity or warpage of the encoder scale disk. This method provides a programmable counter for the loop counter of PLL circuit and an interval counter with memory in order to learn the repeatable fluctuation. After the learning process, the PLL generates very pure tone clock signal based on the real flutter components of the spindle revolution speed without influenced by encoder errors. This method has been applied to a hard disk test system in order to generate 3GHz read/write clock.

Chatter Stability of General Turning Operations With Process Damping

The accurate prediction of chatter stability in general turning operations requires the inclusion of tool geometry and cutting conditions. This paper presents regenerative chip and regenerative chip area/cutting edge contact length based dynamic cutting force models, which consider cutting conditions and turning tool geometry. The cutting process is modeled as it takes place along the equivalent chord length between the two end points of the cutting edge. The regenerative chip model is simple, and the stability can be solved directly. However, the three-dimensional model considers the effect of tool vibrations at the present and previous spindle revolutions on the chip area, chord length, and force directions and is solved using Nyquist stability criterion. The penetration of worn tool flank into the finish surface is considered as a source of process damping. The effects of the nose radius, approach angle of the tool, and feedrate are investigated. The proposed stability model is compared favorably against the experimental results.

A Study on Ultrasonic Vibration Assisted Tapping of Titanium

Tapping is a technique commonly employed to make internal threads in the fastening industry. However, sudden breakage of tool bits is the most undesirable event often encountered during thread tapping. In particular, this can most readily occur when making internal threads in blind-holes, especially holes smaller than M6. As such, any effort to prolong the life of the tap is both necessary as well as urgent. The present study tried to use the high frequency vibration generated by a piezoelectric actuator to make threads for the titanium alloy. The thread tapping process was analyzed in detail, involving the Taguchi experimentation method, in which an orthogonal array table, L3(34),was employed to design the experimental runs for use in this study. The effects of interacting processing parameters including the frequency of vibration, vibration amplitude, spindle revolution speed and cutting fluid used on the performance of the tapping process were examined. The result was compared with no ultrasonic-assisted tapping.

경량 피스톤 로드를 위한 마찰용접 적용연구(SM45C/SM45C-Pipe 사용)

Various research to reduce weight of a car is achieving. This research is tendencious to manufacture solid piston rod of shock absorber as hollow piston rod using friction welding. This study deals with the friction welding of SM45C to SM45C-Pipe that is used in car shock absorber, The friction time was variable conditions under the conditions of spindle revolution of 2,000rpm, friction pressure of 55MPa, upset pressure of 75MPa, and upset time of 2.0seconds. Under these conditions, the microstructure of weld interface, tensile fracture surface and mechanical tests were studied of friction weld, and so the results were as follows. 1. In tensile strength, the hole processing is better than non-hole processing. 2. When the friction time was 1.5seconds under the conditions, the maximum tensile strength of the friction weld happened to be 869MPa, which is 103% of SM45C's tensile strength and 91% of SM45C's Pipe. 3. When the friction time was 2.0seconds under the conditions, the maximum bending strength of the friction weld happened to be 1599MPa, which is 80% of SM45C's bending strength and 118% of SM45C's Pipe.

Trouble Diagnosis in Machining the Micro Grooves for the Mold of PDP Barrier Rib

This paper describes evaluation and monitoring methods of machining characteristics for developed cutting machine of micro grooves. Experiments were conducted under various process conditions such as spindle revolution speed, feed rates and depth of groove. A precision blade was manufactured to cut micro grooves in the mold of a PDP barrier rib, while taking the groove shape into consideration. The groove cutting characteristics of the blade were evaluated by experimenting on STD11 and cemented carbide. AE technology was used to observe the state of the grooves. The obtained AE signals reliably represented the grooving quality and cutting conditions, as demonstrated through the use of a fuzzy C-means algorithm.

A Methodology of Off-Line Optimization for NC Milling Process

Traditional adaptive control technologies in machining process optimization are limited in applications because they depend much on sensors, controllers and other hardware. An off-line optimization method for end milling process with constant cutting power is presented. On taking advantage of virtual machining which simulates milling process, acquires cutting parameters and predicts cutting forces, method taking constant cutting power as an objective is discussed to optimize feed rates and cutting speeds. Based on optimal result, the feed rates and spindle revolutions in NC program are re-scheduled. Controlled milling experiments show that machining time is reduced and machining stability is improved by using the optimized NC program.

Study of magnetic abrasive finishing in free-form surface operations using the Taguchi method

This study employed magnetic abrasive finishing (MAF) to conduct free-form surface abrasion of stainless SUS304 material operations. The operations were demonstrated using a permanent magnetic finishing mechanism installed at the CNC machining center. The operations were performed using the Taguchi experimental design, considering the effects of magnetic field, spindle revolution, feed rate, working gap, abrasive, and lubricant. Furthermore, the experimental data was collected using the Taguchi experimental design. The optimal parametric conditions for processing stainless SUS304 material were applied in a two-stage process comprised of rough finishing that involved MAF followed by a precise finishing of the surface. Prior to rough finishing, the Rmax value was 2.670 μm; after rough finishing, the value was 0.158 μm. Precise finishing yields an even lower value of 0.102 μm similar to that of the mirror surface. Therefore, the results revealed that MAF provides a highly efficient way of obtaining surface finish.

1610 異形断面工作物加工によるNC旋盤の加工点の動特性計測(G13-1 生産加工・工作機械(1),G13 生産加工・工作機械)

We have developed a new evaluation method to obtain the dynamic characteristics at the cutting point during cutting directly by machining the specific workpiece. An NC lathe is adopted as the target machine tool. Three-dimensional cutting forces are generated during turning operation. These cutting forces change periodically when the cross sectional profile of workpiece that consists of polygon. Then, the periodic excitation forces are observed from there cutting forces generated at the contact point between tool and workpiece. Further, the excited frequency of periodic and sinusoidal forces obtained by machining the non-circle workpiece depending on the workpiece revolution, the desired frequency is to be obtained by changing the spindle revolution variably from DC to maximum revolution. These combinations lead the excitation forces in frequency domain to the desired frequency range and enough force amplitude as same as the swept sinusoidal excitation technique. The pseudo inverse m atrix is used to obtain the approximate solution of the dynamic characteristics. In this report, the proposed method and its evaluation results are reported. Further, the calculated results of transfer functions of an NC lathe are introduced.

엔드밀 가공시 진동, 표면거칠기, 절삭온도에 미치는 최적가공조건에 관한 연구

End-milling has been used widely in industrial system because it is effective to a material manufacturing with various shapes. Recently the end-milling processing is needed the high-precise technique with good surface roughness and rapid time in precision machine part and electronic part. The optimum mechanical vibration of main spindle, surface roughness and cutting temperature have an effect on end-milling condition such as, cutting direction, revolution of spindle, feed rate and depth of cut, etc. Therefore, this study carried to decide the working condition for optimum mechanical vibration of main spindle, surface roughness and cutting temperature using design of experiments, ANOVA and characteristic function. From the results of experimentation, mechanical vibration has an effect on revolution of spindle, radial depth of cut, and axial depth of cut. The surface roughness has an effect on cutting direction, revolution of spindle and depth of cut. And then the optimum condition used design of experiments is upward cutting In cutting direction, 600 rpm in revolution of spindle, 240 mm/min in feed rate, 2 mm in axial depth of cut and 0.25 mm in radial depth of cut. By design of experiments and characteristic function, it is effectively represented shape characteristics of mechanical vibration, surface roughness and cutting temperature in end-milling.

A study on the evaluation of the micro grooving using the AE technology

This study describes evaluation and monitoring methods of machining characteristics for developed micro grooving machines. Experiments were conducted under various process conditions such as spindle revolution speed, feed rates, and depth of groove. V and U shape of blades and STD11 were used in this experiment. The status of grooving was evaluated through analysis of the acoustic emission (AE) signal resulted in each process condition. Based on the analysis, this paper examines the possibility of monitoring adapting fuzzy logic. In conclusion, this paper presents the possibility of monitoring in process adapting AE technology and appropriate micro grooving conditions.

Studies on High-Speed Milling with Small Ball End Mill

A new three-color infrared radiation pyrometer using an optical fiber is developed for measuring cutting temperature in high speed machining by small ball end mill. The high speed air spindle unit is adopted to the ordinary milling machine so that the maximum spindle revolution of 40000rpm is attainable. The ball radius of the carbide cutter is 3mm and the side cutting of carbon steel with ballnose is executed without cutting fluid. Cutting temperature distribution along the ball-nosed cutting-edge is measured. The influences of spindle rotational speed, radial depth of cut and feed per tooth on the temperature distribution at the flank face are examined. The maximum temperature of peripheral cutting edge about 700°C is obtained even at the rotation angle of 180° after cutting, and it drops along the ballnose toward the ball tip. Relatively large temperature gradient arises along the ball cutting-edge at higher spindle revolution because cutting speed depends on the local tool radius. Depth of cut and feed per tooth, at the same time, affect the overall temperature at the ball cutting edges. The cooling characteristics in air cutting reveals that the temperature difference during one cycle of intermittent cutting increases as spindle speed decreases. The relationship between the peripheral cutting speed and the tool temperature varies from tool shank to ball tip because the interactions between cutting edge and workpiece change along the ballnose.

Non-circle Turning by Displacement Enlargement Mechanism Using Resonant Vibration (2nd report)

A new non-circle turning machine has been developed to obtain the profile which consists of four undulations in the cross sectional profile for automobile piston. The developed displacement enlargement mechanism, which has the designed resonant frequencies with 2 degrees-of-freedom vibration system, vibrates synchronizing with spindle rotation of an NC lathe. This mechanism is driven by PZT electric device, which has not enough elongation originally, exciting the representative point of the beam support constrained on the tool base. Two resonant frequencies are designed so that the target profile is machined to realize four undulations for a circumference. The developed lathe realized the spindle revolution of 870rpm that exceeds the copy lathe, which is used for the ordinary piston machining, seldom exceeds the maximum revolution of 800rpm because of the limitation of dynamic characteristics depending on stylus follower. Although there are various NC lathes equipped additional axis and/or linear motor to solve this problem, these kinds of machines are not suitable for mass-production but these should be used for flexible manufacturing. On the contrary, the developed turning lathe machine is so simple that only the specific spindle revolution is acceptable and suitable for mass-production. Experimental results of no-circle turning showed the profile deviations for various non-circle targets settled within 7μm compared with the conventional profile tolerance of 10μm in the case of profile amplitude 350μm.

A study on the precision machinability of ball end milling by cutting speed optimization

This study proposes an optimization cutting speed program developed to improve the machining precision and tool life in high speed machining using the ball end mill. This program optimizes the cutting speed that varies during free surface machining. As for the technique of optimization cutting speed, the NC code generated from CAD/CAM goes through a reverse post process and cutting simulation and the effective tool diameter of the ball end mill is obtained. Then the range of critical cutting speed suitable for the workpiece is selected and the spindle revolution is changed according to the effective tool diameter within the range of the critical cutting speed. In this paper, the machining precision and tool life were compared in the free surface machining conducted by the general cutting method and the technique of optimization cutting speed.

Relationship between machinability additives and machining parameters

This study proposes an optimization cutting speed program developed to improve the machining precision and tool life in high speed machining using the ball end mill. This program optimizes the cutting speed that varies during free surface machining. As for the technique of optimization cutting speed, the NC code generated from CAD/CAM goes through a reverse post process and cutting simulation and the effective tool diameter of the ball end mill is obtained. Then the range of critical cutting speed suitable for the workpiece is selected and the spindle revolution is changed according to the effective tool diameter within the range of the critical cutting speed. In this paper, the machining precision and tool life were compared in the free surface machining conducted by the general cutting method and the technique of optimization cutting speed.

505 高速小径ボールエンドミル加工における工具温度分布の測定

Cutting temperature distribution along the curved cutting-edge of small ball endmill is measured with an three-color infrared radiation pyrometer using an optical fiber. The high speed air spindle unit is adopted to the ordinary milling machine so that the maximum spindle revolution of 40000rpm is attainable. The ball radius of the carbide cutter is 3mm and the side cutting of carbon steel at spherical ball is executed without cutting fluid. The influence of spindle rotational speed, radial depth of cut and feed per tooth on temperature distribution at the flank face are examined. The maximum temperature about 700℃ is obtained at the peripheral cutting edge and it decreases along the ball cutting-edge toward the ball tip. The relatively large temperature difference arises along the ball cutting-edge at higher spindle revolution because the cutting speed depends on the local tool radius. The depth of cut and feed per tooth, on the other hand, affect the overall temperature at the ball cutting edges.

メタルボンドダイヤモンドホイールを用いたセラミックス研削作業の最適化に関する研究 (第1報)

This study deals with the optimization of ceramics grinding operation with metal bonded diamond wheels.In this paper, the discrimination of the quality of wheel conditioning and of dressing interval is discussed based on signals obtained from an accelerometer pickup mounted on the spindle head of the surface grinder. As a result, it is clarified to identify whether truing and dressing operations are completed or not, by detecting the specific frequencies which are equivalent to the integral multiple numbers of spindle revolution and the principal characteristic frequency of the spindle head, respectively. Also, with 800Hz which is the characteristic frequency of the spindle head, as the specific frequency, it will be possible to determine the dressing interval by considering the rapid increase of acceleration amplitude.

A predicted milling force model for high-speed end milling operation

In this study, a predicted milling force model for the end milling operation is proposed. The speed of spindle rotation, feed per tooth, and axial and radial depth of cut are considered as the affecting factors. An orthogonal rotatable central composite design and the response surface methodology are used to construct this model. The milling force per spindle revolution period obtained from each treatment is equally divided into suitable sections. The extreme value of the milling force in each section is selected to build the predicted model so as to predict the extreme force in each section for any cutting conditions within the specified range of the design database, including the speed of spindle rotation, feed per tooth, and axial and radial depth of cut. Moreover, the predicted extreme force in each section is applied to reconstruct the milling force waveform by means of the expansion of the Fourier series. The predicted model presented in this paper is adequate for a 95% confidence interval, and shows good correlation between experimental and predicted results.

Transient Solutions of the Ring-Spinning Balloon Equations

In the textile yarn manufacturing process of ring spinning, a loop of yarn rotates rapidly about a fixed axis. The surface generated by the rotating yarn loop is called a balloon. The solutions of the time-independent, nonlinear, yarn-balloon equations have been extensively investigated for a reference frame that rotates with constant angular velocity and are termed quasi-stationary solutions. A linear perturbation stability analysis of these solutions has shown that while single-loop balloons are stable, multiple-loop balloons are typically unstable. In this paper a numerical method for the calculation of transient solutions of the nonlinear time-dependent PDEs is developed, and the stability of representative quasi-stationary balloons subjected to a model velocity impulse is studied. The results of the linearized analysis are confirmed: Single-loop balloons remain stable while multiple-loop balloons typically collapse within only a few spindle revolutions.