Showing papers in "Precision Engineering-journal of The International Societies for Precision Engineering and Nanotechnology in 1985"

Design and testing of a fast tool servo for diamond turning

Abstract: A self-contained and independently servo-operated diamond tool holder was built to increase the resolution and accuracy of a precision lathe. Its static and dynamic repeatability over a range of ± 50 μin (1.27 μm) is better than 0.05 μin (1.3 nm). Its frequency distortion from 0–100 Hz is less than 1.0 μin (25 nm) for a peak displacement of less than 28 μin (0.71 μm).

Optical system for measuring the profiles of super-smooth surfaces

Abstract: The design of a common-path polarimetric interferometer system, developed primarily for measuring the profiles of ‘super-smooth’ surfaces, is described and measured comparisons with a mechanical stylus technique are discussed. The instrument has a sensitivity to changes in surface height of better than 0.1 nm and is capable of a lateral resolution of 1 μm with a helium-neon laser light source.

Calibration of coordinate measuring machines

Abstract: For over three years the Physikalisch-Technische Bundesanstalt has been investigating the numerical error correction of cmms , and the relationships between problems in this area and in the calibration of these machines. It has been determined that calibration is possible, for pre-defined conditions, but that the calibration is applicable only to the particular measuring task and conditions. This paper describes the mathematical model used by PTB and gives results of tests on a cmm .

Absolute two-dimensional sub-micron metrology for electron beam lithography: A calibration theory with applications☆

Abstract: A mathematical theory is presented along with some simple resulting procedures that permit an electron beam lithography machine to be calibrated by using it to make multiple observations of an imprecisely defined but stable planar object The calibration thus obtained yields a degree of accuracy that is approximately equal to the reproducibility of the machine For this purpose a rigid, movable grid plate is used, with grid points placed at arbitrary but more-or-less evenly distributed, fixed positions on its surface An e-beam lithography machine with a high precision X-Y stage has been used to measure such a grid plate Two interferometer beams, nominally parallel to the X- and Y-axes, measure stage displacements No geometric assumptions are made concerning the stage, other than repeatability Although the assumptions are very general, it is possible to observe the grid in just three orientations to determine both an inverse distortion function (calibration) and accurate, absolute rectangular coordinates for the grid points, providing that the absolute distance between a pair of points on the grid is known A calibration program has been written applying the theory to the practical problem of calibrating an e-beam lithography system Simulations based upon actual e-beam measurements confirm the theory for the practical situation The paper concludes with suggestions for applictions to three other areas of science and technology: astronomy, optometry, and satellite geodesy

Improvements in grinding steels by cryogenic cooling

Abstract: The intensive temperatures in high-speed machining and grinding not only limit the tool life but also impair the machined surface by inducing tensile residual stresses, micro-cracks and thermal damage. This problem becomes acute when the components are made of hard and strong materials and used in dynamic loading. In such cases drastic cooling is essential during machining. The authors have employed liquid nitrogen in the form of a jet in the surface grinding of a number of steels and found appreciable improvement, though to varying degrees, in their surface quality without significant change in specific energy requirement.

A capacitance based ultra-precision spindle error analyser

Abstract: The measurement of errors in the axis of rotation is of increasing interest, and considerable work has been done to improve understanding of the effects of these errors on machined workpieces. In an attempt to simplify the measurements, and to increase their accuracy, a multiple capacitive transducer has been developed. Use of large-area sensors reduces the effects of out-of-roundness and misalignment of the master cylinder. Instrument errors less than 10 nm have been demonstrated. A combination of digital and analogue circuitry reduces set-up time to a minimum, and facilitates rejection of the once-per-revolution components at any speed.

Practical non-contact surface measuring instrument with one nanometre resolution

Abstract: Appareil d'utilisation pratique pour la mesure sans contact des surfaces avec une resolution d'un nanometre

In-process measurement of surface roughness during cylindrical grinding process

Abstract: An in-process surface roughness sensor developed by the author has been applied to cylindrical grinding operations. The sensor utilizes fibre optics to illuminate a workpiece surfacec and to detect the intensity of the reflected light. A change of surface roughness during one plunge grinding cycle is measured for various grinding conditions. It is confirmed by the measurements that the surface roughness is closely related to changes of the workpiece radius during a grinding cycle. The result is quite simple and it is useful in determining the cycle time of a grinding operation.

Problems with software for running coordinate measuring machines: The use of virtual volumetric standards

Abstract: The validation of software for coordinate measuring machines is increasinly being seen to be as important as the assessment of the machine construction and its coordinate system. Virtual volumetric standards are the coordinates of points on the surface of an imaginary workpiece which can be used to evaluate cmm software. This paper gives some examples of virtual volumetric standards and their use.

Design, manufacture and testing of precision machines with essential polymer concrete components

Abstract: High accuracy in precision machinery can be achieved by using new materials such as polymer concrete. The possibility of using these materials in service depends mainly on the physical features of the materials and on the material dependency of the machine-parts. The construction, manufacturing and testing of the precision machines mentioned in this article have led to a better understanding of the materials and to the development of expressions relating to their use.

Stone-based structural materials

Abstract: Several stone-based structural materials are compared, including cement concrete, polymer cement concrete and a special type of granite-based polymer concrete called Granitan. The differences between the materials, particularly for machine-tool component applications, are discussed. It is shown how the inherent disadvantages of these stone-based materials, notably the high thermal expansion and creep, have been refined out of more recent formulations, by using different resins, more controlled structure and specific stones.

Automatic calibration system for polygon mirrors

Abstract: An automatic calibration system of polygon mirrors is described. This system consists of the four subsystems: a precise rotary mechanism, a rotary magnetic scale for angular standard, a special photo-electric autocollimator which enables dynamic measurement, and a mini-computer system which controls the compiling and handling of data. The basic principle of the system depends on the self-checking method, so that both the polygon mirror and the standard rotary scale are calibrated simultaneously. A time-conversion method is adopted to detect slight angular difference with high resolution. By way of an example, the calibration of a 12-sided polygon is described. The results obtained are as follows: (1) The calibration can be done automatically in a short time without skill, except for the manual operation of setting a polygon relatively for the magnetic scale; (2) 95% confidence interval of instrumental error calibrated on the system is within ±0.07 seconds of arc.

Atomic bit machining by energy beam processes

Abstract: Energy beam processes have an important role in atomic bit processing because they are capable of supplying the high level of specific processing energy necessary at the atomic level. Several applications of such processes to fabrication of electronic, optical and mechanical components are given, and future prospects of the energy beam processes for atomic bit machining are examined.

Manufacture of some SIMS components from tantalum foils by electrolytic photoetching

Abstract: Components of a specimen holder used in secondary ion mass spectrometry (SIMS) have been fabricated from tantalum by electrolytic photoetching. Principal benefits of the technique are the ability to use a non-hazardous etchant and the ease with which design modifications can be carried out

Comparison of cone-centre and ball-centre for roundness in cylindrical grinding

Abstract: In high precision cylindrical grinding it is customary to support the workpliece with dead-centres. The workpiece is rotated as a guide to the points o

Low thermal expansion materials for high precision measurement equipment

Abstract: The operation and mechanical construction of an instrument which measures the shape of aspheric surfaces with ± 5 nm precision is reported1. The instrument makes use of contacting probes, and it functions on the basis of an optical differential technique. To achieve maximum performance the equipment is built in glass-ceramic (Zerodur) and Invar. Special attention is paid to the selection and machining aspects of these thermally stable materials.

In-process control of machining: milling a part according to its function

Abstract: The implementation of a machining strategy which focuses on part function rather than conventional manufacturing drawing tolerances is described, and comparisons with existing machining and inspection practices are made. The function controlled is cannon recoil force; the critical parameter measured is the area-distribution of teardrop-shaped orifices machined in a tube wall. To control this parameter adaptively, a machining centre is fitted with an optically-based, microcomputer-controlled metrology system which monitors orifice area as it is being machined, compares to a standard, and corrects the tool path as necessary. The final inspection record is generated while the part is on the machine.

Smooth, low scatter metal optics by repeated machining on a ‘no growth’ machine

Abstract: Specifications mastered well today for metal optical components up to some 10 cm diameter include figure and slope. Diamond-machined optical function surfaces also require a minimum incident light scatter and maximum specular reflectance equalling that of the bulk material. This relates to microfinish, which is less well mastered in micromachining. We report recent results in the state of the art of diamond machining metal surfaces. We expect that today's physical and economic limit can be pushed further by a special machining process reducing roughness, based upon repeated machining relying on a ‘no growth’ machine. In this method the tool is exposed to the full range of cutting depths between the preset maximum down to ‘zero’, or rather to a limit about which we intend to learn much more. In situ tool inspection is essential to predict results. The method was presented at Laser 83 and we now present recent results. The process of repeated machining concentrates on flats and spheres.

Precise and versatile systems for dilatometric measurement of solid materials

Abstract: An interferometric dilatometer has been developed which uses a double path high-sensitivity interferometer and specimen supporting systems. Usual interferometric dilatometers require polished specimens, but the present system does not need any special specimen preparation. The system, therefore, provides measurement facilities for various shapes and dimensions of materials such as thin wires, slender rods, etc. The interferometric system incorporates self-compensation for optical misalignment and a resolution of 1 nm can be achieved by using an ac fringe detecting system.

Integrated metrology systems

Abstract: The integration of quality into future manufacturing planning is an essential part of the factory of the future, one specific area of quality assurance — metrology or dimensional inspection — plays a key role in guiding, coordinating, and approving manufacturing efforts. The advances in modern industrial production towards greater precision and more reliable function of products have created the need for a continuing, parallel improvement in dimensional measurement and inspection technologies. Selecting, justifying, and integrating these technologies into manufacturing operations requires careful planning and the consideration of alternative approaches for implementation. An overview is presented of a programme recently completed for the US Army Tank and Automotive Command (TACOM) with the purpose of assisting TACOM vendors in the integration of metrology into future operations to improve quality and reduce overall costs.

Statistical design for the location of planes and circles when using a probe

Abstract: A statistical approach to the problem of establishing the location of planes and circles by use of a touch-trigger probe mounted on a machining centre is presented. Equations for determining the minimum number of measurements to make and their location in order to locate a part within a specified confidence interval are given. An explicit solution to the parameter estimation problem for the circle is derived, and its properties are compared with solutions from two other methods. It is shown that one of the methods has an estimator whose accuracy does not improve as the number of measurements made is increased because the probe can move only along cartesian axes when it is mounted on a machining centre.

Analysis of light scattering by rough manufactured surfaces

Abstract: The relationship between the roughness of a manufactured surface and the angular distribution of the light scattered by that source is presented. A one-dimensional rough surface model is considered. It has been found that the angular distribution of the light scattered in the Fraunhofer zone is proportional to the square of the Fourier transform modulus of the surface reflection function. If the peak-to-valley height of the surface roughness is small compared with the light wavelength, the angular distribution of the light scattered is proportional to the power spectrum of the profile. If the peak-to-valley height of the surface roughness is comparable with or greater than the light wavelength, the angular distribution of the light scattered can be determined by using the suggested light scatter simulating system.

An optical non-contact probe

Abstract: An optical non-contact probe to detect displacement, position and inclination of a work surface is presented. It uses two light beams which intersect near the surface and form spots of light on it. Images of the spots are formed on a photo-detector by a lens. Positions of the images and distance between them, which depend on the distance from the intersection to the surface, are sensed by the detector. Its output is electrically converted into a signal which represents displacement, position or inclination of the surface. An experimental probe is set up, in which laser diodes and a position-sensitive detector are used. The probe is tested on sandy, milled, lathe-turned, ground and specular surfaces and the measurements agree with predicted values.

Functional needs, machining conditions, and economics of surface finishing☆

Abstract: Two applications of surface finish technology to industrial problems are discussed. The first problem involves the deterioration of tools used to turn large numbers of parts. Preliminary observations indicated that waviness of the tool cutting surface impeded chip flow over the tool and reduced usable life. Changing the tool finishing conditions reduced waviness considerably and increased tool life between sharpenings from 8000 to 53 000 parts. The second case involves the degradation of flat steel tracks for rolling needle bearings in a moulding machine. Waviness of both the newly ground and refinished surfaces led to their rapid deterioration In addition, the hardness of the steel was also considered to be too low for this application. By improving the finishing process, the life of a set of guides was improved from typically 1500 hours to 5000 hours. For this case, the financial implications of the results are also discussed.

Measurement of transient cutting force by means of a Fourier analyser

Abstract: Measurements of transient cutting force are often required for analysing transient phenomena in cutting or detecting tool chipping. With most existing tool dynamometers which detect cutting force through strain, however, accurate measurements of transient cutting force cannot be expected because of inadequate frequency characteristics or large time lag. This paper proposes a method of measuring the transient cutting force. In this method, cutting force is calculated by means of a digital Fourier analyser from the output of a tool dynamometer and the transfer function, which has been identified in advance under the same set-up as used for the cutting test. The assessment tests have revealed that the cutting force calculated in this way is extremely close to the real value, regardless of the dynamic rigidity of the tool dynamometer. This method is also applicable for accurate detection of acceleration of a simple system.