Dimensional Machining Research Articles

A hydrodynamic interpretation of a problem in the theory of the dimensional electrochemical machining of metals

A method of determining the form of the anode-blank boundary for a specified form of the cathode tool in plane problems of the theory of the dimensional electrochemical machining of metals is proposed. Within the assumptions made, the anode-blank boundary is divided into a working zone, in which solution of the metal occurs, and a region next to it in which the machining ceases. The initial problem is reduced to a problem of plane-parallel potential flow of an ideal liquid with non-linear conditions on its surface. The point which separates these two regions of the anode boundary corresponds to the point where the jet separates from the solid boundary. The Brillouin-Villat smooth separation condition is specified when compiling the closed system of equations at the point where the jet separates.

Modelado y simulación del proceso de fresado a alta velocidad en MATLAB-SIMULINK

Machining processes constitute some of the most used procedures of metals processing. This paper shows the implementation, in MATLAB-SIMULINK, of a mechanistic model that relates the cutting forces and the torque in the high-speed milling (HSM) process to the generalized geometry of the tool and cutting parameters. The implemented model predicts the magnitudes of the cutting forces and the resulting torque. The main equations of the cutting process and the equations to calculate the radial chip thickness for 3 dimensional free-form machining are presented. In addition, it introduces the kinematics of the entry and exit radial immersion angles. This model is validated with data collected experimentally, demonstrating its effectiveness. Furthermore, the model can be used in systems of supervision and control of HSM using the predicted cutting forces and torque to determine the possible appearance of faults such as tool wear, tool breakage and the presence of vibration or chatter.

Analysis of product quality with consideration of influence of manufacturing errors in discrete-part machining systems

Control of product quality is one of the deciding factors in current manufacturing competitions, and has always presented a great challenge to both academia and engineers since for a discrete-part machining system, the final product variation is an accumulation from all stations, and there is a complex non-linear relationship between dimensional quality and machining errors. This paper explores a procedure for expressing the influence of a numbers of errors on dimensional variations. The procedure provides one virtual design tool provided CAD AND CAPP data are available. A real-world example is used to illustrate the new methodology.

On improvement of materials separation accuracy by superimposition of electric fields

In this paper, the existing techniques of electrochemical dimensional machining are considered. The use of an additional current-conducting template makes it possible to improve the accuracy of materials separation with the aid of the electric field superimposed.

High-speed anode dissolution of heat-resistant chrome-nickel alloys containing tungsten and rhenium: III. Chloride-nitrate solutions

The anodic dissolution rates of two heat-resistant tungsten (12 wt %) and tungsten and rhenium (8 wt % W : 6 wt % Re) alloys in chloride, nitrate, and chloride-nitrate (30 g/l NaCl : 120 g/l NaNO3) electrolytes have been compared. An excess of the critical current density i crit depending on the hydrodynamic conditions leads to (i) the decreasing dependence of the current efficiency on the current density and (ii) the independence of the dissolution rate on the solution content. The mass-transfer mechanism, which determines the dissolution rate and the structure of superficial layers at i > i crit, is discussed. Data on the chemical content of the surface layers depending on the machining modes are presented. The modes of the electrochemical dimensional machining (ECDM) of the parts made of these alloys are offered to attain the best performance parameters for machining.

Two Dimensional Machining Test of Hard-Brittle Materials Under High Hydrostatic Pressure

This paper reports two dimensional machining tests of a soda glass conducted under high hydrostatic pressure up to 200 MPa. A new device has been developed which enables us two dimensional machining test and in-situ observation by an optical micro scope. The device consists of a pressure vessel, a high pressure pump, a two dimensional machining tester and an optical microscope system. Water is used as pressure medium. The two dimensional machining tester consists of an X stage, a stepping motor that drives the stage, a single point diamond tool, a load cell and a tool holder. The load cell is set on the X stage, and a work piece is mounted on the load cell. The load cell measures both principal force and tangential force simultaneously. All of these mechanisms are installed in the pressure chamber. They work well even under high hydrostatic pressure up to 200MPa. The tool and a work piece are observed by a microscope placed outside of the chamber through a sapphire window. Image of machining process is observed by a CCD camera. Machining tests of soda glasses were conducted using single crystal diamond tools of various rake angles. Three types of chip formation were observed; chipping type and discontinuous type were observed under 0 MPa, and 100 MPa, whereas continuous type was observed under 200 MPa. Measurement of cutting force under 0 MPa and 100 MPa revealed that external hydrostatic pressure is effective to increase both principal force and tangential force. Machining mechanism under hydrostatic pressure is discussed.

State space modeling of dimensional machining errors of serial-parallel hybrid multi-stage machining system

最后的产品质量被累积决定，联合，从所有的产品质量变化的繁殖在多级式的生产驻扎系统(MMS ) 。建模并且变化繁殖的控制是必要的改进产品质量。然而，变化(SOV ) 的当前的溪流理论能仅仅解决单个 SOV 影响的问题产品质量。由于多重变化流的存在，有限研究在连续平行的混合多级式的生产系统(SPH-MMSs ) 在质量控制上被做了。一个州的空间模型和它的当模特儿的策略被开发在 SPH 公里描述多重变化溪流加起来。SOV 理论被扩大到 SPH 公里。系统模型的尺寸被归结为生产现实水平，并且模型的效果和可行性被一个用机器制造的盒子验证。

MODELING AND CONTROL OF DIMENSIONAL QUALITY OF A SERIAL MULTI-STATION MACHINING SYSTEM

Modeling and control of dimensional quality is one of deciding factors in current manufacturing competitions, and has always presented a great challenge to both scientists and engineers since for a multi-station machining system, the final product variation is an accumulation from all stations, and the complex non-linear relationship exits between dimensional quality and machining errors. This paper develops a linear state space model using homogeneous transformation to capture the influence of machined errors on dimensional quality, and the explicit expressions for system matrices of the model are explored. The proposed model employs a linear state space form, facilitating the use of the achievements of control theory, information technology and system engineering theory to support engineers supervisory control of physical machining processes, and it also can be used as an analytical engineering tool for efficient and effective faults diagnosis, system plan and design, and optimal sensors allocation. A real machining case illustrates the proposed model.

Diagnosibility and sensitivity analysis for multi-station machining processes

Dimensional variation is a major problem affecting product quality in discrete-part manufacturing. The stream of variation (SoV) methodology has been proposed as one of the systematic approaches to identify the root causes of process variation based on part measurements. This paper presents the results of the diagnosibility and sensitivity analysis study of the SoV methodology in a multi-station V8 cylinder head machining process used by a major domestic automotive manufacturer. The SoV model of dimensional machining errors has been derived based on the CAD description of the part and CAPP description of the process. Variation patterns of the final product were assessed based on the measurements of 20 automotive cylinder heads machined under normal process conditions, and the relative contributions of each machining station were assessed. In addition, one faulty product was observed and SoV model was used to identify the machining station that caused this quality problem. A station-level error decomposition method has been introduced and the SoV model correctly identified the culprit station. Furthermore, the sensitivities of dimensional features of the cylinder head to departures in fixture parameters away from their nominal values are evaluated based on the SoV model. Finally, four major issues arising from this implementation study of SoV in industry have been identified. Those are: non-diagnosibility of available measurements, vectorial representation of features, random sampling of parts at inspection and inadequate level of details in modeling of the process faults.

Development of a Machining Tester for Two Dimensional Machining Test under External Hydrostatic Pressure

This paper reports on a new machining device developed for experimental study on machining property of hard-brittle materials under external hydrostatic pressure. A new machining device was developed for two dimensional machining tests as well as in situ observation of a machining process by an optical microscope under hydrostatic pressure up to 400MPa. The device consists of four parts; a high pressure vessel, a pump system, a machining device installed in the chamber and an optical microscope. Detail of structure of the device is reported in the paper. Two dimensional machining tests of a soda glass plate were conducted using the device under four levels of pressure. Results of the machining tests is also reported.

SANDVIK BIOLINE 20AP

Abstract Sandvik Bioline 20AP is a high-hardness alloy with dimensional stability and excellent machining properties. This datasheet provides information on composition, physical properties, hardness, and tensile properties. It also includes information on heat treating and machining. Filing Code: CS-145. Producer or source: Sandvik Steel Company. See also Alloy Digest SA-642, January 2012.

Evolution of the Shape of the Anode Boundary under Electrochemical Dimensional Machining of Metals

This paper presents a method for calculating the anode boundary under unsteady conditions of electrochemical dimensional machining of metals. The plane quasistationary problem of determining the shape of the anode boundary for various machining times is considered.

A Hybrid Methodology For On-Line Process Monitoring

A hybrid strategy of using (i) locally linear embedding for nonlinear dimensionality reduction of high dimensional data and (ii) support vector machines for classification of the resultant features is proposed as a robust methodology for process monitoring. Illustrative examples substantiate the methodology vis-à-vis current practice.

Measurement Scheme Synthesis in Multi-Station Machining Systems

Different sets of measurements carry different amounts of information about the root causes of quality problems in machining. The selection of measurements in multi-station machining systems is currently a slow and error-prone process based on expert human knowledge. In this paper, we propose systematic procedures for synthesizing measurement schemes that carry the most information about the root causes of dimensional machining errors. The amount of root cause information conveyed by a given set of measurements was assessed using the recently introduced formal methods for quantitative characterization of measurement schemes in multi-station machining systems. The newly proposed measurement scheme synthesis procedures were applied to devising measurement schemes in an automotive cylinder head machining process. It was observed that the measurement scheme synthesis procedure based on a genetic algorithm robustly outperformed the synthesis procedures based on the heuristics of successive measurement removal.

Dimensional Errors of Fixtures, Locating and Measurement Datum Features in the Stream of Variation Modeling in Machining

Machining processes are usually multi-station processes involving a large number of operations and several locating datum changes. Machining errors are thus introduced, transformed and accumulated as the workpiece is being machined. This paper introduces procedures for expressing the influence of errors in fixtures, locating datum features and measurement datum features on dimensional errors in machining. These procedures are essential in the derivation of the Stream of Variation model of dimensional machining errors using the CAD/CAPP parameters of the machining process. The linear state space form of the Stream of Variation model allows for advanced control theory achievements to be employed in formal solutions to problems in multi-station machining. Modeling procedures presented in this paper were experimentally verified in machining of an automotive cylinder head.

Bayesian approach to measurement scheme analysis in multistation machining systems

Different measurement schemes in multistation machining systems carry different amounts of information about the root causes of dimensional machining errors. The choice of a measurement strategy in a multistation machining system is therefore crucial for subsequent successful identification of the machining error root causes. Recent advances in the linear state-space modelling of dimensional errors in multistation machining processes facilitate a formal and systematic characterization of measurement schemes. In this paper, the stream-of-variation methodology is employed to characterize various measurement schemes quantitatively in multistation machining systems using the Bayesian approach in statistics. Application of these methods is demonstrated in the characterization of measurement schemes in the machining process used for machining of an automotive cylinder head.

Anode-Shape Determination with Allowance for Electrolyte Properties in Problems of Dimensional Electrochemical Machining of Metals

Based on the boundary-element technique, a method for determining the contour of an anode-workpiece with a prescribed shape of a cathode-tool is suggested for plane problems of dimensional electrochemical machining of metals. Within the scope of the assumptions made, the original problem is reduced to the problem of a fictitious flow of an ideal fluid with free surfaces. The allowance for the machining mode and electrolyte properties yields a nonlinear condition at the free surface.

ANALYSIS OF THREE-DIMENSIONAL MACHINING USING AN EXTENDED OBLIQUE MACHINING THEORY

This paper presents an extended oblique machining theory applicable to the analysis of 3-D machining. Existing theories are evaluated to identify suitable formulations which are used with necessary modifications for predicting various quantities pertaining to cutting conditions of three dimensional machining. Actual chip flow angles extracted from measured forces, to account for the nose radius effect, are used, instead of available models, to predict important quantities such as shear plane angle, effective rake angle and shear flow angle. Experiments are conducted in the realms of conventional and high speed machining using AISI 4140 steel and aluminum 7075-T6 respectively with uncoated carbide inserts, and various process conditions pertaining to the cutting mechanics are calculated. The extended oblique machining theory is experimentally validated in predicting temperatures at the tool-chip interface and shear plane for conventional machining. Simulation results from the finite element modeling are used for verifying the shear stress and shear plane temperature predicted by the extended oblique machining theory.

420 Three Dimensional Machining of Diamond by Using Tool Wear During Cutting Process

420 Three Dimensional Machining of Diamond by Using Tool Wear During Cutting Process

Material Damage-Based Model for Predicting Chip-Breakability

A model for predicting the chip breakability potential of groove and obstruction-type tools is described. The potential for a tool to break chips is evaluated in terms of the chip geometry and the damage sustained by the chip as it is formed in the shear zone. The chip geometry is characterized by its thickness-to-radius ratio, and the material damage is evaluated in terms of a normalized accumulated damage factor that is based on a hole growth and coalescence model. The chip thickness-to-radius ratio and the normalized accumulated damage factor are evaluated using a finite element cutting model. A total of 210 cutting tests were conducted to verify the model. Different tools including flat, obstruction, and groove, were tested for cutting of AISI 1020 steel and SS 304 steel. Each of these tool geometries exhibited significantly different chip thickness-to-radius ratios and normalized accumulated damage. Threshold criteria for breaking chips were determined for AISI 1020 and SS 304. For difficult-to-break materials such as stainless, a lower normalized accumulated damage was needed and a higher chip thickness-to-radius ratio was required to break chips. Although the model presented in the paper was developed for orthogonal cutting, it can be readily extended to three dimensional machining processes. Using this approach, a new tool design can be evaluated for its chip breakability potential with much less reliance on prototype building and testing.