Showing papers on "Machining published in 1978"

NC machining of arbitrarily shaped pockets

Abstract: Machining mechanical parts requires a great deal of area cleaning, i.e. cutting away all material within given boundaries. This paper describes a fast algorithm, implemented in the SAAB-Adapt processor, to compute the necessary cutter paths for machining arbitrarily shaped areas (pockets) bounded by straight lines and arcs.

Linear, annular, and radial focusing with axicons and applications to laser machining

Abstract: New optical combinations of axicons and axicons with spherical mirrors and lenses suitable for laser machining are presented. Linear and annular focusing, coaxially and radially to the laser beam, are possible. Most combinations allow continuous adjustment of exit beam parameters, focal line length, focal ring diameter, and magnification, by varying the relative position of one of the axicons. Potential new laser applications are also discussed in relation to these optical devices.

On the Non-Uniqueness of the Machining Process

Abstract: The elimination of a class of possible slip-line field solutions for orthogonal machining indicates that the process is not uniquely defined. The range of possible solutions for any value of tool rake angle and interfacial shear stress is shown to be associated with large variations in the curvature of the machined chip. Machining conditions are split into two types, for one of which the machined chip will always curl, while the other has the Lee & Shaffer slip-line field as a lower limit of the solution range. The extent of the solution range for any value of friction is found to decrease with increasing rake angle. The analysis is shown to be consistent with certain experimental work available.

Detecting and eliminating collisions in NC machining

Abstract: When a 3D object is milled from a billet by a cutting assembly (tool and an associated cutting head), a common hazard, particularly if the cutting is under numerical control, is that this assembly may collide with (foul) the partly cut billet. Fouling may be detected and eliminated by simulating the changing billet shape and the moving cutting assembly: fouling is detected when billet and cutting assembly models occupy the same model space. The principal method of removing fouling is to modify the billet by removing those parts that would subsequently foul. Alternatively, the cutter assembly may be modified by fitting a longer tool, whose length is calculated to lift the cutter assembly above any part of the billet causing fouling. For premodifying billets, the program records the parts of the billet causing fouling and calculates a cutter path to remove these. Since this preliminary cut may itself cause fouling, the program is applied recursively to the initial toolpath and subsequent defouling toolpaths until a final toolpath is reached that does not cause fouling. These preliminary toolpaths are then executed in the reverse order of their generation. The method assumes that the final shape has a single height above every point of its base, and is therefore limited to shapes that do not have undercutting.

Optimization of multi-pass machining operations

Abstract: The purpose of this research was to develop an optimizing procedure for a multi. pass machining operation. Geometric programming was utilized to determine the values of the machining variable for each pass to yield minimum production cost. The levels of speed and feed were subject to certain restrictions based on allowable values of force, power and surface finish.

Clean surface reactions between diamond and steel

Abstract: THE rate of wear of diamond grinding on machining steel is known to be extremely high. For example, the wear rate of a diamond turning mild steel is 104 times greater than when turning brass of comparable hardness1. Several discussions of this wear conclude that it is due principally to the high local flash temperatures generated during machining and to the catalytic properties of the steel. Static experiments show that diamond graphitises at temperatures above 1,800K in vacuo, or above 1,100K in the presence of iron, and other experiments that flash temperatures of this order may be generated by machining. Hence, there is now general agreement that the wear proceeds by the graphitisation of the diamond; the surface layer of graphite being continually removed either by the abrasion of the steel or by solution in the steel2–7. However, little information is available on the actual conditions prevailing at the interface during machining. Therefore, we have studied the mechanism of wear more closely by making quantitative measurements of the wear rates of round-nosed diamond tools turning billets of mild steel under well defined conditions.

An application of goal programming technique in metal cutting

Abstract: This paper outlines the use of the goal programming technique in selecting levels of machining parameters in a fine turning operation on A1S1 4140 steel using cemented tungsten carbide tools. Goals that are proposed to be achieved are: (i) to finish turning the required depth in one pass, mid (ii) to finish turning within a stipulated time. Constraints used are: R.M.S. surface finish values, cutting horse power of the machine, ranges for cutting speed, feed and depth of cut. A predictive equation to predict the R.M.S. Surface roughness values from the machining variables, cutting speed, feed, depth of cut, and time of cut was used. This mathematical model was developed using stepwise regression analysis on the experimental data for 1/64 in. nose radius cemented tungsten carbide cutting tool. Experiment with the machining variables at different levels were performed to obtain the data. A statistically designed experiment called the rotatable design was used for the experimental design

Frequency adjusting a piezoelectric device by lasering

Abstract: Electrode material is laser machined from a piezoelectric device (10) to adjust its resonant frequency to a nominal value. At the same time the device (10) is electronically cleaned by overdriving the device at a high current level to prevent loosely adhering lasered particles, which cause the device to be electrically unstable, from accumulating on the device. The simultaneous laser machining and electronic cleaning also eliminates erratic resonant frequency changes in the device (10) which occur if the electronic cleaning is performed after the laser machining. As the nominal resonant frequency value is approached, the device (10) is overdriven at successively lower current levels and the laser machining is carried out at respective successively lower rates.

Tool Wear in Cutting Carbon-fiber-reinforced Plastics : The Effect of Physical Properties of Tool Materials

Abstract: A turning (facing) test on glass-fiber-reinforced-plastics was performed with several tool materials, e.g., sintered carbides, cermets and ceramics, and the wear patterns and wear land growth rate were analyzed to clarify the relationship between physical (mechanical) properties and flank wear of cutting tools. The main results are obtained as follows: (1) When cutting speed is increased, the rate of wear on the nose in every tool material starts to increase remarkably at a certain speed, i.e., a critical speed. (2) Thermal conductivity coefficient versus critical speed curve is approximately linear when plotted on log-log coordinates. The higher the thermal conductivity coefficient of tool material, the higher the critical speed becomes. There also seems to exist an influence of the compressive strength and thermal expansion coefficient of tool materials on its performance in high speed cutting of GFRP.

Laser machining apparatus

Abstract: PURPOSE:To remove the portion to be machined of the workpiece with laser beam and then trim.

Unmanned machining center with tool checking

Abstract: A numerically controlled machining center has a tool magazine, automatic tool changer, workpiece shuttle, and a workpiece magazine which holds enough workpieces for operation by the machining center for an entire shift of approximately eight hours. The numerical controls are programmed to perform predetermined machining operations on each workpiece, in turn, and to replace each finished workpiece with a fresh workpiece at the end of each machining program. A proximity switch is mounted on the machining center for checking tools to detect broken or incorrect tools. The tools are positioned adjacent to the proximity switch and are rotated while tho output of the proximity switch is counted for one complete rotation of the tool to determine the number of radially extending teeth on the tool. If the tool has too few or too many teeth, thus indicating a broken or incorrect tool, it is replaced by another tool of the same type. If no alternate tool is available in the tool magazine, the machining cycle is automatically suspended.

Mirror system for uniform beam transformation in high-power annular lasers

Abstract: The conditions for transformation with uniform intensity from an annular to a cylindrical beam, as needed for mode control in high-power lasers, are analyzed. The equations for the shapes of the mirrors in two different arrangements are derived and evaluated for feasibility of fabrication. The shape of the inner mirrors as well as the major part of the outer mirrors should present no problem of fabrication. In either system, however, that edge of the outer mirror which reflects to the axis requires a sharp curvature, the machining of which might appear formidable. Nevertheless, recent work with diamond machining has accomplished even sharper curvatures than here required.

Monitoring the E.D.M. process by radio signals

Abstract: Experimental studies are described to show that high-frequency radio observations provide a simple way to monitor the E.D.M. process and to distinguish between the effective spark and arc discharges. The paper also describes how radio frequency emitted during machining could be used to optimize the E.D.M. process. It was found that radiation from the region of the gap between the electrode (tool) and the workpiece are significantly different when the following conditions occur: open voltage, sparking (effective machining), arcing and short circuit. However, a reliable technique was developed to monitor the rate of metal removal and machining efficiency during the E.D.M. process

Method and apparatus for electrical machining with a multi-guided travelling electrode

Abstract: A traveling wire electrical machining system makes use of a single-strand traveling wire which is guided in a plurality of passes across a workpiece to cut through the latter at a plurality of parallel locations. According to the invention, the machining power supply has a plurality of outputs each of which is connected to a respective stretch of the traveling wire, thereby equalizing the machining current for each of the multiple stretches.

Metallurgical appraisal of instabilities arising in machining

Abstract: The character of the shear instability in the metal-cutting operation is discussed with reference to results from machining En58C austenitic stainless steel It is shown that at certain cutting speeds a continuous chip which exhibits large serrations is formed The sequence of events in a typical cycle of serration formation has been established from a series of photomicrographs of ‘quick-stop’ specimens, and the associated dynamic cutting forces have been recorded It is shown that the serrated chip formation is not caused by machine-tool vibration but is related to the inherent metallurgical features of the steel, for the machining conditions used The essential feature of the chip formation is a varying shear strength of the work material at the chip/tool interface: a phenomenon that is similar to the stick-slip conditions described in previous work on the discontinuous chip formation In a typical cycle, compressive stresses build up ahead of the tool as material sticks on to the rake face; se

Apparatus for controlling position of a plurality of machining shafts each including a machine tool fitted thereto

Abstract: Apparatus for controlling the position of a plurality of machining shafts each including a machine tool fitted thereto so as to move each machining shaft up to its given position in response to the kind of machining to be subjected to a work piece. The apparatus comprises a memory for memorizing the position of each of the machining shafts which are different from each other in dependence with the kind of machining to be subjected to the work piece and a central processing unit for reading out data showing the position of each machining shaft from the memory in succession and generating through one servo-amplifier a signal required for moving the machining shaft corresponding to each servometer to its given position.

Apparatus for simultaneous machining of a stack of plate-like workpieces

Abstract: There is disclosed a method and apparatus for the simultaneous machining of a stack of plate-like workpieces wherein the individual workpieces of the stack are initially assembled into a stack which is held in a manner which will not interfere with the subsequent machining operations by use of rivets or the like. The plate-like workpieces are mounted in the stack upon a support plate, and the machining operations are preferably so conducted as to penetrate through the lowermost member of the stack and into the upper portion of the support plate. The machine tool is preferably one in which a series of stations for drilling, riveting, machining and then drilling out the rivets is provided. The tool may include means for automatically and precisely moving the stack between the several work stations. The method involves the preliminary assembly of the stack of plate-like workpieces upon the support plate and the initial clamping in that assembly until the elements of the stack are initially drilled and riveted to secure the elements of the stack in position relative to each other for the subsequent machining operations.

Cutting insert for chipforming machine

Abstract: A cutting insert for chipforming machining of workpieces is of the type comprising a rake face and a clearance face. At least one cutting edge is formed by the transition between the rake and clearance faces. The cutting edge is intersected by depressions extending along the rake face. The greatest dimension of each depression in a direction parallel to its associated cutting edge is greater than the distance between adjacent depressions.

Automatic apparatus for machining panels, planks and similar articles made of wood, wooden derivatives and the like

Abstract: Disclosed herein is an automatic apparatus for machining panels or similar articles and, particularly, for drilling and milling them in accordance with the "Folding" system. With this apparatus, the panel to be machined is carried by conveyor means, in a direction parallel to its longitudinal axis, towards drilling and milling devices placed one after the other, the latter being able to mill the panel transversely with respect to the direction in which it moves forward. The operation of the drilling and milling devices takes place contemporaneously in unison, controlled by a feeler device located after the milling devices, which is able to perceive the presence of milling in the panel and to consequently cause the panel to halt and to be in the exact position necessary for the aforementioned drilling and milling devices.

Efficiency scale-up for hydraulic turbo-machines with due consideration of surface roughness

Abstract: Particularly in its empiric part this report is based on model tests carried out by universities and manufacturers of hydraulic turbo-machines, who are members of Working Group 5 (WG 5) of the "Section on Hydraulic Machinery, Equipment and Cavitation" of the IAHR. The scale-up behaviour is dealt with on the basis of separate analyses of losses, whereby an important section refers to the influence of surface machining and depth of roughness Rt of separate machine components (full-size plant). Corresponding calculations result in figures which express the modifications in efficiency Δ η(ri) due to the accepted roughness, size of the machine and specific energy Y of the head. The figures for Rt refer to data supplied by leading manufacturers of hydraulic equipment for power stations. Apart from a differentiated insight into the scaling-up process, the report also provides indications and guide-lines for answering the question as to the economically acceptable amount of machining for which the losses caused b...

Method and apparatus for machining spherical combustion chambers

Abstract: A spherically shaped combustion chamber is machined in the cylinder head of an internal combustion engine by revolving one or more cutting tools simultaneously about two axes; one axis being the central axis of the combustion chamber and the other axis being inclined thereto. The tools have a cutting point and a cutting edge extending from the cutting point. The tools are supported so that each cutting point passes through the axis of the combustion chamber, and, when each tool is located in its radially outermost position relative to the axis of the combustion chamber, the cutting edge of the tool cuts an annular surface around the periphery of the spherically shaped portion of the combustion chamber, which, at the bottom face of the cylinder head, corresponds in diameter to that of the cylinder bore.