Showing papers on "Machining published in 1979"

Surface residual stresses, surface topography and the fatigue behavior of Ti-6AI-4V

Abstract: Fatigue tests have been conducted on Ti-6Al-4V from 293 to 589 K to determine the influence of surface residual stresses and surface topography on low and high cycle fatigue properties. Four types of machined surfaces as well as shot peened surfaces were included in the investigation. It was found that surface residual stresses play a key role in controlling the development of microcracks and, therefore, overall fatigue lives at both room and elevated temperature. X-ray measurement of the stability of surface residual stresses under thermal activation and/or cyclic loading demonstrated that, for the conditions studied, cyclic loading was primarily responsible for residual stress decay. In addition, the magnitude of the decay was dependent on the relationship between the sign of the residual stress and the sign of the imposed mean strain. Finally, it was demonstrated that the sharpness of machining grooves is more important than their depth in controlling fatigue resistance.

Flow stress model in metal cutting

Abstract: A model for the plastic deformation that occurs in metal cutting, based on dislocation mechanics, is presented. The model explains the fundamental deformation structure that develops during machining and is based on the well known Cottrell-Stokes Law, wherein the flow stress is partitioned into two parts; an athermal part which occurs in the shear fronts (or shear bands); and a thermal part which occurs in the lamella regions. The deformation envokes the presence of a cellular dislocation distribution which always exists in the material ahead of the shear process. This 'alien' dislocation distribution either exists in the metal prior to cutting or is produced by the compressive stress field which operates in front of the shear process. The magnitude of the flow stress and direction of the shear are shown to be correlated to the stacking fault energy of the metal being cut. The model is tested with respect to energy consumption rates and found to be consistent with observed values.

Apparatus for machining material

Abstract: The gaussian energy distribution common to all laser beams is a serious handicap in most laser beam applications for machining material, such as for drilling, welding and the like. This is especially true in welding extremely thin metal sheets, as in the manufacture and assembly of the transducers of modern magnetic disk files. According to the subject invention, a laser beam is directed to a glass cone or axicon which converts the gaussian energy distribution of the laser beam to one more uniform in cross-section. Depending on the distance of the workpiece from the exit side of the axicon, the energy distribution of the radiation impinging onto the workpiece will be either uniform, saddle shaped or annular cross-section. It has been discovered that saddle shaped or annular energy distributions are optimal for welding very thin metal sheets by a laser beam since the heat dissipation in the center of a welding spot is a minimum and that at the periphery of the laser beam depends on the material, size and shape of the workpiece, which parameters can be matched by adjusting the distance between the axicon and the workpiece.

Reliability Analysis of Cutting Tools

Abstract: This paper is concerned with the reliability analysis of tool life based on the tool-wear values obtained from metal cutting experiments. From experimental results, a statistical distribution of tool wear was decided, and the distribution of tool life and the reliability function of cutting tools were derived. Further, it was shown that the reliability of cutting tools at a certain time was easily calculated from machining parameters and tool-wear limits by the use of reliability function.

Electrode for electrical discharge machining

Abstract: An electrode for machining a workpiece by electrical discharges, the electrode having an active surface comprising at least 50% by weight of a metal or alloy selected from the group consisting of zinc, cadmium, tin, lead, antimony and bismuth. Preferably, the active surface is in the form of a coating electrolytically plated on the surface of a conventional metallic wire having good mechanical characteristics. The invention contemplates continuously plating a metallic filament electrode such as an electrode wire with the active surface coating after the electrode wire has been used for machining a workpiece by EDM.

Process control for electrical discharge machining apparatus

Abstract: A process control system for electrical discharge machining apparatus to control automatically the machining of a workpiece. The process control system is operable to receive and retain a plurality of operation instructions regarding electrical discharge machining parameters and transmit operation commands to the electrical discharge machining apparatus to execute the operation instructions in controlling the complete machining of a workpiece. The process control means includes a storage unit operable to store a plurality of operation instructions enabling absolute repeatability of the machining process defined by the operation instructions in the storage unit for a plurality of workpieces. The process control system also includes a digitally controlled servo system to regulate the movement of the electrode toward and away from the workpiece.

Transparent single-point turning of optical glass:: A phenomenological presentation

Abstract: Single-point turning of optical glasses by continuous chip generation at elevated temperature is described in this paper: appropriate temperatures are ranged around the American softening point. Optimisation of tool-setting, depth of cut, local heat supply and other parameters resulted in transparent turning of a number of optical glasses by a process combining abrasive turning by single-point machining and viscous relaxation of the glass surface immediately after removal of the continuous chip

Machine tool control systems

Abstract: A machine tool control system includes a numerical control device associated with each machine tool and an interface unit interposed between each machine tool and the numerical control device. The numerical control device includes a first memory area for storing a first group of programs related to the machining of a workpiece and the selection of a cutting tool, and a second memory area for storing a second group of programs related to interrupting instructions.

Radially shrinkable sleeves

Abstract: Radially shrinkable sleeves for covering joints and terminations in high voltage cables are made by radially uniform machining of an extrudate comprising an insulating layer and at least one other layer which is conductive or semi-conductive or exhibits stress control properties. Expansion of the sleeve can be effected before or after machining. Novel shrinkable sleeves which are obtainable by this method include an insulating layer which comprises at least one tapered section in which its internal diameter increases gradually from a first diameter to a second diameter.

Prodn. track with several machining stations - has interchangeable sections alongside each other for each station and with own conveyors

Abstract: The production track is for items to be produced in two or more operations, having machining or assembly stations in a line, loaded by driven conveyors with the items, the latter being preferably mounted on jigs. The track comprises two or more sections arranged alongside each other to form rows and interchangeable, and each with its own conveyor for the items or their jigs, there being one section for each station and forming a complete assembly with it. There are preferably separate guides and driving members for the jigs, and there are separate adjustable governors for the sections with their machining stations, which can preferably also be coupled to adjacent sections and to a central control unit.

Method of using Si3 N4.Y2 O3.SiO2 ceramic system for machining cast iron

Abstract: A process for continuous or interrupted machine cutting of solid cast iron by milling, turning or boring with a shaped tool, wherein said shaped tool is a ceramic consisting essentially of Si3 N4 and 4-12% by weight Y2 O3, produced by hot pressing at a pressure and a temperature of 1700°-1750° C to achieve substantially full density

Electro-chemical-machining of aerofoil blades

Abstract: An electrode assembly for electro-chemically machining an article, such as an aerofoil shaped blade for a turbo machine. The assembly comprises a plurality of electrodes 2,3 for location adjacent a workpiece 7. Each electrode 2,3 is constrained to move in a first direction towards each other and towards the workpiece 7 and has two side members 22,23 carried by a main body 21. The side members 22,23 are constrained to move with the main body 21 and also relative to the main body in directions parallel to the first direction. The side members 22,23 advance ahead of the main body 21 and when they abut the side members 22,23 of the other electrodes 2,3 their advancement is stopped while the main bodies 21 of the electrodes 2,3, continue to approach each other for a predetermined distance. In this way edge effects during machining are eliminated enabling an accurate shape of article to be produced.

Laser Assisted Machining

Abstract: The availability of high power cw carbon dioxide lasers with sufficient ruggedness, reliability and simplicity of operation for use in manufacturing facilities has led to the development of new machining methods. These methods currently involve the localized vaporization or melting of the material due to beam heating. (1) In the case of metallic materials beam heating is supplemented with burning enhanced by a flow of oxidizing gases at the point of impingement of the laser beam. In our research, we have developed a new and dif-ferent method of cutting with a laser, laser assisted hot spot machining (LAM), in which the laser is used to heat the volume of material directly in front of a single point cutting tool to a temperature less than its melting point.(2,3)The application of gas torch and induction heating to assist, in the turning of metals was first studied in the United States by Tour and Fletche(1949). Concurrently, Schmidt investigated the use of gas torch heating in milling. Although many advantages were reported such as reduction in power consumption tool life improvement and improvement in surface finish, hot-machining has not been perceived as a practical and economically viable method by industry. Recently, however, with the development of more intense heat sources such as the plasma-arc(5) and the laser, hot machining has become more attractive in specific applications as a metal removal technique.

Working pieces by laser beam

Abstract: A laser-assisted machining process for the machining of materials which are normally difficult to work employs a laser source and associated reflecting means which focus the laser beam onto two distinct areas of the workpiece material to effect localized heating thereof and assist the formation of shavings by a cutting tool: one area is immediately in front of the cutting edge of the tool and the other is adjacent the leading face of the tool, in part of the workpiece material which is deformed plastically by the tool in the formation of a shaving.

Method for maskless chemical and electrochemical machining

Abstract: A method for high resolution maskless chemical and electrochemical machining is described. Preferential etching results from exposing those regions where machining is sought to an energy beam. Such exposures can increase the ething rate in the case of electrochemical machining by a factor of 103 to 104. Such enhancement is sufficient to make masking unnecessary.

Method and apparatus for machining a workpiece by varying the tool geometry

Abstract: A method and apparatus for machining a workpiece to perform several functions including sensing tool wear, enhancing tool life, tool wear compensation, cutting a workpiece having two different materials joined at a boundry, and suppressing chatter, including placing a cutting tool having a rake face and a clearance face with a first clearance angle with respect to a workpiece and a second clearance face with a second clearance angle with respect thereto and with the first clearance angle being less than the second clearance angle and supporting the cutting tool in a rotatable tool holder having an axis of rotation with the cutting tool tip being aligned with the axis of rotation such that rotation of the holder varies the cutting tool geometry to perform the several functions.

Method of machining crankshafts

Abstract: A crankshaft is machined at cylindrical portions consisting of mainshaft portions and crankpins and at crankweb side faces associated with the cylindrical portions in a sequence of steps which proceed in the direction from one end of the crankshaft to the other. Each step comprises machining a crankpin which precedes a given succeeding mainshaft portion and a mainshaft portion, when viewed in this direction while the crankshaft is supported by a steady at the given mainshaft portion and machining crankweb side faces adjoining one of the cylindrical portions at the same time as the one cylindrical portion. To improve the accuracy with which the crankshaft can be machined, each of the step comprises machining said one cylindrical portion before the other and machining the crankweb side faces associated with the other cylindrical portion at least in part during the machining of the one cylindrical portion.

The Nature of Strength Controlling Machining Flaws in Ceramics.

Abstract: : The nature of machining flaws introduced in a variety of glass, single crystal, and especially poly-crystal bodies are reported, based on fractographic determination of such flaws as the source of mechanical failure. Particular attention is given to grinding where the anisotropy of strength due to the direction of grinding relative to the tensile axis is shown to be due primarily to a dual population of flaws of differing shapes. One set of flaws form approx. perpendicular and another parallel to the grinding direction. The latter flaws are typically substantially more elongated and often larger than the former and thus give lower strengths for stressing perpendicular to the direction of grinding. Sawing, sanding, and polishing are also shown to result in similar dual flaw populations. The character of flaws are examined as a function of the type of material and machining, as well as specimen size and shape. The latter suggests a limited strength-size effect due to machining flaws. However, the key findings are that machining flaws do not vary greatly with typical variations of machining or material parameters, e.g. composition, grain size, or hardness. (Author)

A gallium-arsenide laser facsimile printer

Abstract: We summarize the development of a high-resolution facsimile printing system in which miniature archival images are machined in metal film by a pulsed, focused, scanning laser beam The film is designed to machine at optical energies within the pulse-power capabilities of GaAs semiconductor lasers. The images are instantly available, as machined, for rear-projection viewing in a compact desk-top printer. Frames of 8 × 10 mm area containing 3.3 × 105 pixels and demonstrating up to seven distinguishable gray levels have been written in 12 seconds. Extensive data on hole machining in partially oxidized, low-melting-temperature, metal films are marshalled to show that single-layer films are inhospitable media for facsimile machining with GaAs lasers. We describe a two-layer film consisting of about 600A of bismuth followed by approximately 650A of selenium evaporated onto a low-surface-energy substrate. This selenium thickness is antireflective at the laser wavelength, and the composition is nearly stoichiometric for Bi 2 Se 3 . A strongly exothermic reaction occurs when molten bismuth and selenium mix in the irradiated area. We present data illustrating the machining performance of this film with a thick-cavity, GaAlAs, double-heterostructure laser providing 300 mW of peak power at 3-percent duty factor and 0.1-μs pulse duration and give examples of the image quality obtained in raster-scanned, hole-array machining. Studies of film adhesion, scratch resistance, and shelf life are summarized. Several diffraction-limited optical systems for acquiring, deflecting, and focusing the GaAs beam onto the film, cylindrically corrected for astigmatism and ellipticity, are described, and several laser properties which affect image machining abversely are characterized.

Method for machining works of current-conducting material with current-conducting abrasive tools

Abstract: The invention is applicable to the griding with current-conducting abrasive tools of works of current-conducting churlish materials, such as hard, magnetic and refractory alloys, and to cutter sharpening. The method according to the invention consists in applying voltage pulses to a tool and a work placed in a liquid medium with a conductance of 10-4 to 2·10-2 ohm-1 ·cm-1. The process of grinding the work and electric-erosion cleaning the tool is carried out at a pulse duration of 0.5 to 10 msec, pulse repetition frequency of 10 to 500 Hz, and amplitudie of pulses ranging from a minimum of 3 V to a maximum which is below a level required for a breakdown of the liquid medium between the tool and the work. Alternatively, simultaneously with machining the work the electric-erosion truing of the tool is performed with the use of a tool truing electrode. The tool truing electrode and the work are connected to the same pole of a power source. According to an alternative embodiment, the truing electrode is a nozzle intended to direct a liquid medium into the machining zone.

Cutting tool insert for precision radial machining

Abstract: A cutting tool insert for precision radial machining comprises two cutting faces and is adapted to be fitted in the strap of a tool holder. Said insert consists of two opposed identical frustoconical portions having a common circular base forming the median plane of the disk of which the longitudinal median plane is aligned with the axis of rotation of the tool holder and intersects with the center of the common base circle. Each of said portions has a cutting face in the median plane which is disposed symmetrically on either side of said axis; the cutting faces are obtained by cutting the relevant frustoconical portions depthwise along the median plane and bound by an inclined plane. The disk may also be made of two separate, identical portions.

A method for measuring shear-band temperatures

Abstract: We have designed an experiment for measuring temperatures accompanying the formation of bands of intense plastic strain. Shear bands intersecting the specimen surface were produced in machining chips of 4340 steel and 2014‐T6 aluminum by orthogonal cutting using a lathe. An infrared microscope was then focused on the chip near the cutting tool to record temperature variations as shear bands swept through the focal area. We report preliminary estimates of temperatures, strains, and strain rates.