Showing papers on "Machining published in 1982"

Analysis and modelling of edm parameters

Abstract: Metal removal in electro-discharge machining (edm) is basically a thermal erosion process where the heat transfer is predominantly through conduction. In this paper, a two-dimensional heat transfer model, assuming the plasma channel to be a disc heat source, has been employed to study the effects of edm input parameters, such as pulse duration, pulse energy and material properties, on metal removal and crater shape. Reasons for somewhat poor correlation between theoretical and experimental data are discussed.

Laser machining system

Abstract: A computer controlled apparatus is disclosed for performing a series of laser machining operations on a work piece in an environment comprised of a non-reactive gas with respect to the material of which the work piece is made. The computer controlled apparatus includes a machining chamber for receiving the work piece and means in the form of a pump for directing the non-reactive gas into the machining chamber at a controlled, selected rate. A laser beam is generated by a laser and is focused into a beam along a path to the work piece. An assembly is provided for selectively moving the machining chamber and its work piece therein through a sequence of steps, whereby the relative position between the work piece and the laser beam is changed such that a series of lasing operations and, in particular, welds may be effected on a sequence of selected sites of the work piece. A computer is programmed to control the rate at which the non-reactive gas is introduced into the machining chamber, as well as to the machining sites of the work piece, whereby the selectively moving assembly may be controlled to dispose the work piece to effect the series of welding operations.

Tool touch probe system and method of precision machining

Abstract: A system and method are disclosed for automatically machining a work piece to precise selectively determined dimensions under computer numerical control in which the cutting tool is set automatically and automatic on-machine inspection is performed of the machined work piece surfaces. Using vibration sensing to detect contact between the cutting edge of the cutting tool and position reference surfaces, the cutting edge is calibrated against these surfaces under closed loop control. The deviation between the programmed and the actual positions of the cutting edge at each reference surface is determined and an initial compensating tool position offset is automatically provided in each axis and is entered into numerical control means. After machining has been initiated, probing of the work piece occurs at least once before the final cut is taken. The tool functions as a tool touch probe during this operation and vibrations are sensed as the calibrated cutting edge is brought into contact with the machined surface. Appropriate tool position offsets are determined and entered into the numerical control means at that time, to assure that the dimensions of the finished surface will conform to the desired dimensions. After final machining has taken place, the finished surface is again probed with the calibrated cutting edge, using vibration sensing. Deviations from the desired dimensions are determined and are indicated together with the allowable machining tolerance for each dimension.

Machining aerospace alloys with the aid of a 15 kW laser

Abstract: “Concept feasibility” has been shown for laser-assisted machining (LAM) using a 15 kW continuous-wave laser— the concept being that a laser beam will selectively heat the workpiece in a machining operation, and will thereby enable higher rates of metal removal to be achieved without a corresponding loss in tool life. The concept feasibility study involved two aerospace materials: Inconel 718 and Ti-6Al-4V. Ceramic tools were used for Inconel 718 and carbides for the titanium alloy. For both materials, the metal removal rate was significantly increased without aggravating either cutting force or tool wear, the gain in removal rate being 33 pct for Inconel 718 and 100 pct for Ti-6Al-4V using current tool materials and beam coupling techniques. The commercial feasibility of LAM requires (a) incorporation of the process into a “laser integrated manufacturing system,” or (b) dropping the power requirement to approximately 5 kW through improved beam coupling techniques, both of which serve to reduce the effective capital investment and operating costs for LAM. Application of LAM is foreseen for difficult-to-machine materials in parts for which the machining time is a major portion of the total floor-to-floor time and thus warrants minimizing.

Methods of entering machining information and display therefor in a numerically controlled machine tool

Abstract: Disclosed herein is a method of controlling a numerically controlled machine tool comprising the steps of classifying cutting tools and machining order for the respective machining patterns determined in response to the final machining contour of a workpiece machined by a numerically controlled machine tool like a machining center, for example in case of the final machining contour with a counter bore and a tap, the cutting tools and machining order of centering--drilling--end milling for a counter bore and centering--drilling--tapping for a tap, by the unit of machining patterns; storing the classification in the numerically controlled machine tool; reading, during machining of the workpiece, a unit of machining patterns corresponding to the machining contour of the workpiece on a display unit; machining the workpiece with numerical information as to each machining patterns entered in the numerically controlled machine tool; and displaying the machining process conditions on the display unit.

Advanced processing methods for titanium

Abstract: Among the topics discussed are recent advancements in Ti near-net shape technology, vacuum hot pressing of large, near-net shape spar fittings, Ti alloy sheet forming, superplastic forming/diffusion bonding of Ti alloys, the influence of H additions on the high temperature superplasticity of Ti alloys, the effects of processing on the fatigue life of Ti-6Al-4V castings, and the laser welding of a Ti alloy. Also considered are aspects of speed machining of Ti, the microstructures and mechanical properties of laser-welded Ti alloys, and the failure characteristics of cutting tools for Ti alloy machining at high speeds.

A Mechanics of Machining Approach to Assessing Machinability

Abstract: A machining analysis is given from which the geometry of chip formation and the associated temperatures and stresses can be predicted from a knowledge of the work material flow stress and thermal properties and the cutting conditions. It is shown how the temperatures and stresses determined in this way can be used to make estimates of tool life, cutting forces and the built-up edge range thus offering an alternative to presently used empirical methods. A comparison between predicted and recently obtained experimental results showing the effectiveness of the approach is given.

Improvement in the working accuracy of an nc lathe by compensating for thermal expansion

Abstract: This study proposes a practical and economical way of improving the working accuracy of an nc lathe by predicting and compensating for the thermal expansion of the tool during machining, a phenomenon which greatly affects the machining accuracy. The thermal expansion can be calculated accurately by the program in which the amount of heat generation is represented as a function of cutting condition and cutting time. As the program judges that the expansion of the tool exceeds or falls below a certain value, tool offsets are made in the direction of cut in advance of operation. Cutting tests on an nc lathe with this compensation have shown a marked improvement in the machining accuracy

Predicting Cutting Forces for Oblique Machining Conditions

Abstract: Using orthogonal (plane strain) machining theory together with certain simplifying assumptions based on experimental observations it is shown how the three components of cutting force in oblique machining can be predicted from a knowledge of the work material flow stress and thermal properties and the cutting conditions. A comparison of predicted and experimental cutting force results is given.

Method of making gas turbine engine blades

Abstract: A method of making a two part aerofoil gas turbine engine blade consisting of casting each individual part separately, the parts being cast by the lost wax process, and subsequently joining the parts together after machining.

Automated machine installation and method

Abstract: A system comprising a plurality of complementary numerically controlled machine tools in which different work-pieces are each subjected to appropriate selected machining operations on selected machine tools in a selected order by appropriate delivery of common form pallets loaded with the workpieces. Transporters deliver pallets between the machine tools, a storage rack, and work-setting stations where work-pieces, automatically delivered in bins from a bin store, are loaded on pallets. Tool magazines are delivered between a rack and the machine tools by a transporter. Transport and machining operations are computer controled, and monitors feed back signals indicative of location of pallets, tool magazines, and bins in the system.

Method and apparatus for monitoring the tool status in a machine tool with cyclic machining

Abstract: The vibration level (a) is measured and applied to controllable filter (F). The filter (F) is a band pass filter that only passes a narrow band around a certain frequency that is determined by the frequency (1) of the machining cycle. The output signal of the filter is then compared to one or several reference levels (7) and an alarm signal is outputted in case of unacceptable deviation from the reference level.

Process and device for treatment of metal-bonded nonconductive materials

Abstract: A rotating electrode tool made of polycrystalline synthetic diamonds in a metal foundation is used in the electro-erosive machining and mechanical grinding of a metal bonded, electrically non-conductive hard material such as synthetic diamonds or boron nitrides in an electrically conductive metal matrix. The tool is first used to electro-erosively machine the workpiece. When a signal is obtained from the machining current or voltage indicating that no further electroerosive removal is possible, the tool automatically mechanically grinds the workpiece to remove nonconductive particles not removed by spark erosion.

Method of machining and vise for use therein

Abstract: To make parts requiring machining with the workpiece vise-held in different orientations, there is provided a precision vise having first and second pairs of jaws, each pair having a member which is fixedly located with respect to a reference location. The invention includes use of a particular form of vise for holding two pieces whereby the screw shaft that rotates to open or close the jaws is tensioned during tightening, which improves accuracy by avoiding bending stresses. When used in conjunction with suitable numerical-control equipment, the vise of the invention greatly increases productivity in the machining of product parts of the kind indicated above.

Wire cut electric discharge machining power source

Abstract: A wire-cut, electric-discharge machining power source which is provided with a first low-current discharge circuit and a second high-current discharge circuit. The first low-current discharge circuit makes a wire electrode positive and a workpiece negative, and the second high-current discharge circuit makes the wire electrode negative and the work positive. After triggering a discharge by the first low-current discharge circuit, a main discharge for machining is produced by the second high-current discharge circuit.