Three-jaw Chuck Research Articles

The effect of gloves, wrist position, and age on peak three-jaw chuck pinch force: a pilot study : Hallbeck, M S and McMullin, D LVisions. Proc Human Factors Society 35th Annual Meeting San Francisco, California, 2–6 September 1991. The Human Factors Society, Santa Monica, California, Vol 1 (1991) pp 753–757

The effect of gloves, wrist position, and age on peak three-jaw chuck pinch force: a pilot study : Hallbeck, M S and McMullin, D LVisions. Proc Human Factors Society 35th Annual Meeting San Francisco, California, 2–6 September 1991. The Human Factors Society, Santa Monica, California, Vol 1 (1991) pp 753–757

The Effects of Forearm Posture, Wrist Posture, Gender, and Hand on Three Peak Pinch Force Types

In many industries the hand is utilized as a fixture, pinching in various wrist postures and forearm postures. In an effort to quantify the effects of wrist posture, forearm posture, gender, and dominant/non-dominant hand upon three peak pinch forces, a study was performed. Three pinch types were tested in this study: index pad pinch, middle pad pinch, and three-jaw chuck pinch force. For each pinch exertion condition, one of five wrist postures were employed: neutral, 45° extension, 65° extension, 45° flexion, and 65° flexion. Each pinch was also performed in one of three forearm postures: neutral, full pronation, and full supination. Ten subjects between 20–25 years of age within each gender category were tested giving a total of 20 subjects. Each subject was asked to build up to his or her maximal voluntary contraction using a modified Caldwell regimen, and hold that pinch level for three seconds. Results were analyzed using analysis of variance (ANOVA) with significant effects (gender, hand, pinch type, wrist posture, and forearm posture) tested using post hoc analysis. The results and their implications are discussed.

Comparison of Power Grasp and Three-Jaw Chuck Pinch Static Strength and Endurance between Industrial Workers and College Students: A Pilot Study

Due to the ease of obtaining subjects, much ergonomics research utilizes students. However, is it valid to make a hypothesis concerning industrial workers from this student data? To evaluate the validity of such a generalization, ten industrial workers and ten students, five men and five women from each subject sample participated in the study. The functional range of motion for extension and flexion in the wrist and anthropometric measurements of the hand and arm were measured for each subject. In addition, the three-jaw chuck pinch force and endurance and power grasp force and endurance were also measured. The data was analyzed using both paired comparisons and ANOVA tests. Only power grasp force showed a strength difference between students and industrial workers. The students had 82.9% of the grasp force of the industrial workers.

ＮＣ旋削加工の形状精度補正

Based on the fact that conventional cutting can not avoid the circularity error which is caused by cutting a deformed workpiece held by three-jaw power chuck, this paper describes three methods to compensate the circularity error using an NC lathe with the tool post driven by PZT to trace the surface of the deformed workpiece so that the resultant cut geometry becomes an ideal one after unclamping. The developed methods can realize a constant depth of cut for the deformed workpiece, during cutting by using the prediction by FEM and/or the measured data of circularity. The predicted data are accurate enough to use as the control input to drive the tool post and the results obtained by using developed apparatus showed the improvement of roundness up to 80% with respect to the component of the three undulations per revolution.

A Study on the Deviation of Shape of a Turned Workpiece Clamped by Multiple Jaws

The shape of a cylindrical workpiece machined in a lathe is dependent on the type of clamping. For example, a workpiece turned by clamping in a two jaw-chuck will be of oval shape and if it is turned by clamping in a three-jaw chuck it will take a three-pronged shape and so on. The causes of the derivation of shape have been described by different authors. However, no thorough analysis has been done to give a generalized mathematical model. In this study, the cutting process under different clamping conditions have been analyzed and a generalized mathematical model has been developed to predict the shape of the turned workpiece in relation to the type of clamping. The experimental results are in good agreement with the thoeretical predictions.

Fluctuation of chucking force in cutting.

With the increasing demands for higher efficiency and machining accuracy in the manufacturing system, the workpiece chucking technology has recently become important. This trend is especially accelereted with the advance of the FMS (Flexible Manufacturing System) technology. The workpiece chucking technology, such as a multiple-jaw chuck greatly affects both the geometrical accuracy and functional performance of the workpiece. In order to enhance the chucking technology of the future, it is necessary to investigate and evaluate the performances of the conventional chuck at first. However, research activity on the conventional chuck is not sufficient enough as yet to solve the problems so far suggested. In this paper, therefore, the fluctuation of the chucking force during non-cutting and cutting has been investigated using the three-jaw chuck of wedge type. In addition, the relationships between the chucking force and the thermal deformation of the workpiece have been measured to clarify the cause of the fluctuation of the chucking force.

Analysis of the Cutting Process of a Cylindrical Workpiece Clamped by a Three-Jaw Chuck

A theoretical analysis has been carried out on the cutting dynamics of a solid cylindrical rotating workpiece clamped by a three-jaw chuck with balanced pressure at the jaws and subjected to a cutting operation. The net reaction balancing the cutting force is found to consist of infinite number of force components oscillating at frequencies 3ω, 6ω, 9ω ... etc., where ω is the angular speed of rotation of the workpiece, and a stationary force term 3F0/2 where F0 is the static balancing force impressed on each jaw-line. The stationary force term tends to give a uniform depth of cut. However the harmonic force terms tend to spoil the uniformity in the depth of cut. Under resonant condition of the third harmonic force maximum depth of cut occurs in the mid positions between two jaws and minimum along the jaw-positions. Resonant vibration of the system takes place at angular spindle speeds ωr = ω0/3P where P is an integer and ω0 = (K/M)1/2 is the angular natural frequency of vibration of the system.

Development of Chucking Condition Sensor for Three-jaw Scroll Chuck

The chucking pressure plays an important role in chucking a cylindrical workpiece with a three-jaw scroll lathe chuck, however, it has not been investigated in the earlier works. In the present study, the chucking pressure is investigated by measuring the strains induced on the chuck jaw surfaces. From the present investigation, the following observations are obtained. (1) The chucking condition can be expressed by a simple diagram so-called "chucking triangle" based on the measured strains of the jaw surfaces. (2) The chucking triangle shows the chucking pressure distributions at the individual jaws and can be displayed automatically on the CRT after processing the strain data with micro-computer. A new sensing method for chucking condition is developed using the chucking triangle. The newly developed method has been tested by chucking specially formed specimens, and it is proved that the new sensing method has satisfactory performances.

Factors affecting the machining accuracy of a chucked workpiece

A deviation in shape called ‘out-of-roundness’ is commonly observed in machined workpieces held by three-jaw chucks in turning operations. This out-of-roundness is due mainly to the variation in the stiffness of the workpiece-chuck-spindle system; the stiffness being higher when the cutting force is acting against a jaw and lower when acting along a jaw. This variation in stiffness of the workpiece-chuck-spindle system, termed here ‘directional orientation’, also leads to the generation of a type of parametric vibration. An attempt has been made to get rid of this effect of directional orientation by optimizing the contact between the jaw face and workpiece. Cutting tests were conducted on tapered testpeices with full contact between the jaws and the testpiece. Various contact chord lengths and spindle speeds were used. Measurements of out-of-roundness, limiting depth of cut and radial cutting force were made for analysis. Results show that where the deviation in shape of the testpiece has a three-pronged profile, and the peak at the third multiple is significant in the frequency spectrum of the radial cutting force, a contact chord length equal to the radius of the testpiece gives the optimized clamping condition.

Considerations of Chucking Force in Chuck Work

In this paper, the chucking characteristics were investigated experimentally. The chucking force during cutting, which had not been studied, was measured with a load washer. Many advantageous characteristics were ascertained in detail with this measuring system. The results obtained from this study are as follows: (1) Fluctuation obtained force is generated periodically with the rotation of main spindle due to the combined effects of directional orientation of the chucking stiffness and the cutting force. (2) This chucking force of a three-jaw scroll chuck decreases with an increase in the fluctuation of chucking force. Especially, the fluctuation appears remarkably in the presence of chatter vibration.

Stability analysis of chatter vibration in turning processes

Most turning operations are carried out with use of three-jaw chucks. The position of the jaws with respect to the direction of the cutting force causes a variation in the mass, damping coefficient and stiffness of the workpiece-chuck-spindle system, the variations being larger when the cutting force is acting against a jaw and smaller when the cutting force is acting along a jaw. These factors are usually considered to be constant when carrying out a stability analysis of self-excited chatter appearing in a turning process and, in consequence, the experimental results so far presented are sometimes found not to agree with the theoretical ones. The variations mentioned above are liable to cause a directional orientation effect in the workpiece-chuck-spindle system and thereby lead to the generation of a type of parametric vibration. Stability analysis carrien out with the above variations taken into consideration is found to give a good qualitative agreement with the experimental results. Furthermore, it is found that with the increase of the variation of the mass, damping coefficient and stiffness of the workpiece-chuck-spindle system, the chatter stability of the turning process deteriorates.

Chucking pressure distribution in turning.

In automatization of the machining procedure, one of the problems is the clamping device for the workpiece. The three-jaw chuck is one of the most representative devices frequently employed in the turning machine. When the chucking is not sufficiently accurate, some deviations in the shape and dimension of the workpiece may occur. Following the series of investigations of chucking, in this paper, the chucking pressure distribution in turning has been investigated, especially aiming at clarification of the change of the chucking pressure due to the act of the cutting force. From the results, it can be observed that the cutting force has considerable effects on shucking pressure distribution, The chucking pressure distribution varies periodically depending on the relative position of the jaw to the resultant cutting force.

Power Actuated Three-Jaw Chucks: Analysis of Gripping Action and Implications

Provision for reliable gripping action is a key factor for industrial application of high speed turning. High speed Machining in production requires safety against burst and adequate gripping over the operating range. The present work is subdivided in two parts. In the first one numerical stress analysis with FEM of main components, under both static and dynamic loads, is described as well as spin test up to rupture speed for design optimization purposes. The second one deals with an in-process gripping force measuring device especially designed to operate in a closed-loop regulation system. Results obtained in the course of an experimental investigation and problems concerning dynamic gripping action are discussed.

Effect of Clamping Conditions on Chatter Stability and Machining Accuracy

In three-Jaw chuck turning operations of overhung clamped workpieces, a variation of stiffness of work-chuck-spindle system is observed depending on the direction of cutting force with respect to the position of Jaws. This leads to deviation of shape of machined workpieces. Moreover, this variation in stiffness termed here as factor of “directional orientation” causes a parametric type of vibration which in turn causes a deterioration in the chatter stability in turning process. The aim of this study is to investigate the factors affecting this variation of stiffness and to propose some means to get rid of this effect of directional orientation. It has been found that factors like the chucking force, the chucking length of workpiece and the type of contact between the workpiece and Jaw faces are mainly responsible for the variation of stiffness. This variation can be eliminated by optimizing the above factors and thus, the deviation in shape can be minimized and furthermore, chatter stability can be improved.

Three-jaw chuck for the working wheels of pumps

Three-jaw chuck for the working wheels of pumps