Showing papers on "Machining published in 1988"

Advanced methods of machining

Abstract: Early progress in machining. Electron beam machining. Ion beam machining. Electrochemical machining. Laser machining. Electrodischarge machining. Plasma arc machining. Ultrasonic machining (USM). Water-jet machining. Specialized methods of machining. Appendix. Basic atomic and electrical principles.

Computational Geometry for Pocket Machining

Abstract: I Introduction.- 2 Survey of contour-parallel Milling.- 3 Survey of direction-parallel milling.- 4 Preliminaries.- 5 Computing Voronoi diagrams.- 6 Implementation issues.- 7 The concept of monotonous areas.- 8 Generating the tool path.- 9 Constructing the mesh.- 10 Generating the tool path.

Compound surface modelling and machining

Abstract: A method is presented for modelling and machining ‘compound surfaces’ commonly found in die cavities and punches. A collection of topologically unrelated surface elements specified in a domain of interest is termed as a compound surface. A constructive solid geometry scheme is employed to model compound surfaces that consist of planar surface elements, general quadratic surface elements, and composite parametric surfaces. Implementation strategies as well as computational details are presented. A prototype modelling system has been implemented on an IBM PC AT. It took less than five minutes to generate cutter location data for a compound surface of realistic complexity.

Surface finish prediction models for fine turning

Abstract: Surface finish data were generated for aluminium alloy 390, ductile cast iron, medium carbon leaded steel 10L45, medium carbon alloy steel 4130, and inconel 718 for a wide range of machining conditions defined by cutting speed, feed and tool nose radius. These data were used to develop surface finish prediction models, as a function of cutting speed, feed, and tool nose radius, for each individual metal. A general purpose surface finish prediction model is also proposed for ductile cast iron, medium carbon leaded steel, and alloy steel. Statistical analysis of experimental data indicated that surface finish is strongly influenced by the type of metal, speed and feed of cut, and tool nose radius. While the effects of feed and tool nose radius on surface finish were generally consistent for all materials, the effect of cutting speed was not. The surface finish improved with speed for ductile cast iron, medium carbon leaded steel, medium carbon alloy steel, and aluminium alloy, but it deteriorated with speed...

Adaptive And Repetitive Digital Control Algorithms for Noncircular Machining

Abstract: This paper presents experimental results of digital tracking control algorithms applied to a hydraulic linear actuating system for tool positioning in noncircular machining. Noncircular machining is accomplished by controlling the tool position in the direction normal to the surface of the rotating workpiece. Implementation of two robust tracking controllers is presented: one is the adaptive zero phase error tracking controller for tracking arbitrary shaped desired signals, and the other is the digital repetitive controller for tracking periodic desired signals.

Diamond tools for rock drilling and machining

Abstract: A polycrystalline diamond tool comprising a diamond layer is bonded to a support body having a complex, non-plane geometry by means of a thin more than 3 μm continuous layer of a refractory material applied by PVD or CVD technique.

Scope of in-process measurement, monitoring and control techniques in machining processes—Part 2: In-process techniques for workpieces

Abstract: This paper surveys the status of technology for the quality assurance of machined products by in-process measurement. The methods of measuring dimension, profile, and surface roughness are described through representative examples. The classification of the advanced technologies is also presented from the author's viewpoint.

Grinding Forces and Energy

Abstract: Grinding forces and energy play an important role in all abrasive machining operations. While specific grinding energy may be obtained from workpiece dynamometer values or by measuring spindle power, care must be exercised in converting dynamometer reading into power consumed. This is particularly true for operations involving a large ratio of wheel depth of cut to wheel diameter or when the radial force on the wheel is large relative to the tangential component. Interpretation of workpiece dynamometer results are discussed and several specific examples are considered including the diamond sawing of granite and the creep feed grinding of metal.

Mechanism of atomic removal in elastic emission machining

Abstract: Elastic emission machining (EEM) can be thought of as a machining method utilizing the chemical activity of a particle surface, rather than a liquid echant as in chemical etching. Selecting the combinations of silicon as workpiece material and SiO2, Al2O3 and ZrO2 as the powder particles, the material removal rate during machining was examined. Different combinations of workpiece materials and powders affected removal rates strongly, so that the machining process was considered from the standpoint of the atomic interactions at the interface between the workpiece and the powder particles. The surface voltage of the workpiece with adsorbed powder particles was measured as one of the parameters representing the interfacial interactions, and correlations with removal rates were obtained.

Multi-run chemical cutter and method

Abstract: Disclosed are a method and an apparatus for cutting conduits. The apparatus includes a cutting head adapted for insertion in the conduit. The cutting head has at least one nozzle. The cutting head is rotatable to locate a previously cut sector of the conduit. A decentralizer is provided for positioning the nozzle adjacent a portion of the conduit.

Multi-function pipe machining apparatus

Abstract: A portable multi-function pipe machining apparatus has a plurality of different cutting attachments to provide a portable machining center. The apparatus has a split frame with an inner ring attachable to the outer periphery of a pipe and rotatably mounts an annular tool head which can carry a selected cutting attachment. The annular tool head is driven by one or more drive motors mounted on the inner ring and having driven gears which mesh with an external annular gear on the annular tool head. Each of the cutting attachments mounts a cutting tool for movement along one or more axes with the movement being derived from rotation of the annular tool head and more particularly by rotation of a driven gear associated with the cutting attachment which is rotated by a stationary tool driving gear 22 on the inner ring. The cutting attachments include a cutoff slide for single axis cutting, a cam slide to provide bevel cutting, an X-Y slide for dual axis cutting and a boring bar attachment for boring and which also has a radially movable tool slide to enable movement of a cutting tool both radially and axially of a pipe.

Real time machining control system including in-process part measuring and inspection

Abstract: A real-time machining control system is provided which includes a conventional computer numerical control and a dimensional measurement system which continually measures the actual diameter of the rotating workpiece and provides an error signal representing the difference between the actual diameter of the workpiece and that of the part program. The error signal is used to directly control the movement of the cutting tool to assure that the final actual machined profile and dimensions of the workpiece conform to the part program.

Manufacture of rotary drill bits

Abstract: A rotary drill bit is manufactured by forming a main bit body part from a machinable metal, such as steel, machining sockets in the outer surface of the main bit, inserting in each socket a thermally stable cutting structure or former which substantially fills at least the mouth of the socket and projects beyond the outer surface of the main bit body part, applying to the surface of the main bit body part, at least in an area surrounding each socket, a compound comprising powdered matrix-forming material, such as powdered tungsten carbide, mixed with a binder to form a paste, and infiltrating the matrix-forming compound with a metal alloy in a furnace to form a hard matrix. The size, location and orientation of the sockets may thus be accurately determined using conventional machining techniques, as in the case of an ordinary steel-bodied bit, but the external parts of the bit body are formed of hard solid matrix material and are thus highly resistant to erosion.

Modelling machining processes with a view to their optimization and to the adaptive control of metal cutting machine tools

Abstract: This paper describes an orthogonal machining theory which can be used to determine the stresses, temperatures etc involved in chip formation from a knowledge of the work material flow stress and thermal properties and cutting conditions It is shown how these can be used to predict machinability factors such as power consumption, built-up edge range, tool wear rates (tool life) and those cutting conditions which cause plastic deformation of the cutting edge An oblique machining theory which is more representative of practical machining processes than the orthogonal theory is then described, taking into account machining on more than one cutting edge as in bar turning Throughout the paper comparisons are made between predicted and experimental results

Machining apparatus having a main spindle supported by magnetic bearings

Abstract: A machining apparatus having a main spindle supported by magnetic bearings which controls machining conditions by controlling electric current values flowing in electromagnets according to predetermined conditions, thereby obtaining an optimum machining condition and thus improving accuracy and machining efficiency. The machining apparatus comprises a spindle having a tool at its one end, electromagnets for radially and axially supporting the spindle by magnetic force without contact to the spindle, position detecting means for detecting radial and axial positions of the spindle, control means responsive to outputs from the position detecting means for controlling current flowing in the electromagnets, current measuring means for measuring current values flowing in at least one of the electromagnets, and machining control means for controlling machining conditions by controlling current values at the electromagnets according to the measured current values.

Three-dimensional laser machining of composite materials

Abstract: This paper presents a concept for performing three-dimensional laser machining on composite magterials, using two intersecting laser beams to create grooves on a workpiece. An analysis of the grooving process was conducted for carbon/teflon and glass/polyester materials. A model was developed to determine groove depth from process parameters and material properties. Groove width and damage width results were compared with surface quality standards for laser cutting of composites

Adaptive Control Systems for Machining

Abstract: In CNC systems of metal-cutting processes the machining variables (e.g., the cutting speed and feedrate) are prescribed by the part programmer. The determination of these variables depends on experience and knowledge regarding the workpiece and tool materials, coolant conditions, and other factors. The main idea in adaptive control is the improvement in production rate and of part quality by calculation and setting of the optimal variables during the machining itself. This calculation is based upon measurements of process variables in real time and is followed by a subsequent on-line adjustment of the machining variables subject to constraints with the objective to optimize the performance of the overall system.

Dynamic Modeling for Control of the Milling Process

Abstract: In the interest of maximizing the metal removal rate and preventing tool breakage in the milling process, it has been proposed that fixed gain feedback controllers, which manipulate the feed rate to maintain a constant cutting force, be implemented. These process controllers have resulted in substantial improvements in the metal removal rate; however, they may have very poor performance when the process parameters deviate from the design conditions. To address these performance problems, an empirical second order model of the force response for a milling system to feedrate changes is presented along with experimental results which show that the parameters of this model vary significantly with cutting conditions. These variations are shown to have significant effects on the performance of fixed-gain proportional plus integral action and linear model following controllers. This is demonstrated using machining tests as well as through digital simulations.

Machine for ultrasonic abrasion machining

Abstract: Machine for ultrasonic abrasion machining of the type comprising an assem (1) supporting the parts (p) to be machined; a vibrating assembly (9) ending in a tool-holder (12) and adapted to drive the tool (8) with a reciprocal movement at ultrasonic frequency and to communicate these vibrations to an abrasive machining liquid; a system for the controlled descent of the tool towards the part to be machined, the attacking surface of the tool (8) being perpendicular to the axis of the tool-holder (12), so that the ultrasonic abrasion machining is carried out at the tool end; a device for regulating the downward movement of the tool; and, between the vibrating assembly (9) and a fixed frame (4), acousto-mechanical filters (20) disposed at longitudinal amplitude nodes (21, 22) of the vibrations, characterized in that an acousto-mechanical filter (20) is formed essentially of two concentric rings (23, 24) connected together by equidistant bridges (25), the inner ring (24) being deformable resiliently under the effect of the radial vibrations.

Indexable cutting insert

Abstract: The invention relates to an indexable cutting insert for face milling of engine blocks of cast iron. The insert has a free surface and a clearance surface and a cutting edge extending peripherally about the insert. The corners of the insert have a relatively large radius and therefore the setting angle gets close to zero degrees during machining of the engine block when the insert gets close to the border line of the work piece. The free surface and the clearance surface enclose an acute angle and therefore the insert has a positive cutting geometry. A land is provided between the free surface and the cutting edge. The land has a width increasing towards each insert corner.

Generation of workpiece orientations for machining using a rule-based system

Abstract: This paper deals with the automatic generation of workpiece orientations on a machine for machining operations. A system capable of this has a wide spectrum of applications in many areas of manufacturing planning and is essential to the development of dynamic process planning systems. However, such a system requires the ability to reason about geometrical and spatial relationships, a topic of great difficulty for automatic reasoning. A study of the problem characteristics is made and its results are implemented in a rule-based system. This system, when given a workpiece along with operation instructions and machine specifications is capable of generating a good orientation for the workpiece. The functioning of the system is demonstrated by an example.

EDM sinker cutting of a ceramic particulate composite, SiC-TiB sub 2

Abstract: An experimental investigation of the machinability of the ceramic particulate composite SiC-TiB{sub 2} was conducted using an electrical discharge machine sinker cutting process. Machinability was evaluated in terms of material removal rates, tool wear, wear ratio, and surface finish, using copper and brass electrodes under rapid, medium, and very slow cutting conditions. Copper was found to machine SiC-TiB{sub 2} material faster with less tool wear but with a poorer surface finish than brass. A comparison of the percent of electrode wear in machining of steel to that of SiC-TiB{sub 2} under very slow cutting conditions showed that machining of SiC-TiB{sub 2} is much more efficient than of mild steel.