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Owing to the demand for shorter cycle times for measurement tasks, coordinate measuring machines (CMM) are required to be used at high speeds. In such high-speed measuring processes, dynamic errors will have a greater influence on the accuracy, and so the dynamic error states should be analysed in this case. A dynamic error assessment model is established in this paper for a specific CMM. The major deflections at the probe position owing to accelerations are obtained by using finite-element analysis and error-data-fitting polynomials for three coordinates. The dynamic rotation errors of the CMM at the probe position are measured with a laser interferometer. By comparing the results of the measured dynamic errors using the laser interferometer and the ones obtained by the error-fitting polynomials, it is shown that dynamic error compensation for a specific CMM is possible to a certain degree.

This paper presents a new approach to optimum tolerancing of components in an assembly such that all interaction requirements are met. The requirements may be for unilateral tolerance for control of clearance and interference or they may be for bilateral tolerance control. A model showing the relationship between components is constructed directly from the design. Using the model, coupled with a unique algorithm, a set of linear equations is formulated based on the design constraints and assembly requirements. The linear equations are then solved to determine the optimum tolerances of the assembly.

Geometric dimensioning and tolerancing (GDT) has been playing an important role in specifying the geometry of part features during the product design stage. Tolerance stack analysis is then used to study the conformity of the parts to the tolerance zone. Performing stack analysis is time consuming because geometric tolerances are complex to compute. This paper presents a technique to formulate the bonus and shift tolerances (due to positional callout) and convert them to equal bilateral expressions as in a coordinate tolerance system. An example is used to demonstrate the effectiveness of the expressions. The usage of the expressions is less conceptual and this makes the application simple and direct. Most importantly, the results are shown to be accurate and reliable.

Dimensioning and tolerancing are important engineering processes in the different phases of a product development cycle. The two main phases in a product cycle where dimensioning and tolerancing techniques are extensively employed are in the areas of product design and process planning. Tolerance and dimension assignment in both product design and process planning has an equally important role in keeping the production cost down and, hence, requires equal attention as far as research into these areas are concerned. Another important motivating factor for research is that manual dimension and tolerance assignment is often tedious, time-consuming and requires a considerable amount of skill and experience on the part of the engineer, resulting in inconsistencies and errors. Extensive research, in the area of dimensioning and tolerancing in both product design and process planning, has been carried out with the advancement in computers since the 1970s. The purpose of this paper is to review the state-of-the-art dimensioning and tolerancing techniques in both product design and process planning and explore the opportunities for future research in these areas.

This paper presents a simple and straightforward, expeditious and accurate approach towards tolerance charting. Its simplicity in logic and approach allows a newcomer in this field to quickly develop expertise in process tolerance charting. The approach is used in conjunction with linear optimisation software, LINDO, to determine the optimal dimensions and tolerances for the part that is being processed. An example is given to illustrate the approach.

One of the main objectives in tolerance charting is to determine the working dimensions and tolerances at the lowest cost without violating the blueprint specifications. It is with this objective in mind that the authors present a comprehensive study of the effect of the choice of an objective function on the final manufacturing cost. Optimisation of the objective functions has been done using PROFORT (nonlinear optimisation). The paper deals with a single example, solved using two linear and a nonlinear objective function.

The tolerance chart is a graphical method for representing the manufacturing dimensions of a workpiece or assembly, at all stages of its manufacture. The chart provides an intermediate control system of checks and balances to ensure that processing dimensions and tolerances will meet those specified on the print. Tolerance charts are generally used in studying the dimensional problems on individual parts. However, they have proved tedious in their application to assemblies. This paper presents a simple and systematic approach to the process of tolerance stack analysis. The “Noded graph” model is constructed, representing the given and the unknown dimensions. Links are then established, using the model, which help to formulate the stack path of interest into a linear equation. The equation is used to complete the tolerance stack analysis module. This will be explained using a variety of geometric dimensioning and tolerancing examples. In addition, it is simple and hence easy to practise and very logical.

This paper introduces a new approach to predicting the natural resting behavior of a part of irregular prismatic cross-sectional shape. The methods proposed by Boothroyd, Redford, Poli, and Murch (1972) and Boothroyd and Ho (1977), successfully analyzed parts whose centers of gravity were located at the geometric center. The hypothesis presented here employs the centroid solid angle of parts of irregular cross-sectional shape with virtual resting faces, such as the L-section. It postulates that the probability of the respective natural resting surfaces of a part coming to rest is directly proportional to the centroid solid angle and inversely proportional to the height of the center of gravity from that surface. The proposed hypothesis is compared with the Energy Barrier Method and experimental results obtained from drop-tests of the L-shaped part. The theoretical results agree well with the experimental results, with the maximum deviation not exceeding 6 percent.

Identification of the optimal production sequence and allocation of machining tolerance are important activities in process planning for reducing production cost. This paper presents an approach that is capable of determining the optimal production sequence and its optimal process tolerance to achieve the minimum production costs. A new mathematical model, representing the cost–tolerance relationships and showing significant accuracy improvement over existing models, is introduced to allocate process tolerance. Stock allowance constraints on the selected switching tolerance are also considered to yield practical solutions. A prototype system for hole-making components is used to verify and evaluate the effectiveness of the new approach.

The energy barrier method, first proposed by Boothroyd and associates, can be used to determine the probabilities of the natural resting aspects of objects to be conveyed on and oriented by vibratory devices. However, for parts of uniform cross-section other than square or rectangular ones, the application of the method can be intractable. In such cases, Boothroyd and associates recommended circumscribing the part by a cylinder and using the energy barrier for the cylinder to approximate the probabilities of the natural resting aspects of the part. This approximation is understandably inexact although computationally expedient. This paper outlines the CAD (computer aided design) computation of the probabilities from the energy barriers for two objects: one, a triangular prism with equilateral sides (representing objects with adjacent faces that are not mutually perpendicular) and the second, an L-shaped prism with a virtual resting aspect. The significance of the centroid plane of the part in the determination of the probabilities is discussed. The CAD computations were carried out using the Graphical Interface Programming (GRIP) Language of McDonnell Douglas' UniGraphics II™ CAD system running on a DEC 9000 workstation.

More industries are now aware of the importance of geometric dimensioning and tolerancing (GDT) to their product design. The conventional method of tolerance stack analysis for GDT is tedious and time consuming. This paper presents an elegant approach by using a 'Quickie' technique of tolerance stack analysis for GDT. The proposed approach has the potential to reduce significantly the amount of work required, and computerisation is promising. Two examples are used to illustrate the effectiveness of the method. The 'Quickie GDT' method is applicable to all geometric characteristics. However, due to the different treatment in the various families of geometric characteristics, this paper describes the 'Quickie GDT' approach for analysing form and orientation tolerances. As for the other geometric tolerances, examples are also included in the appendices.

This paper presents an automated fixture set-up for inspection. The system comprises a workplace with magazines, locators and a baseplate. An articulated robot, the SCORBOT-ER VII is used to automate the system. A C-program is developed and used to execute robot arm movements based on user input. The C-program also establishes locating postions for a rectangular workpiece and determines the set-up of the locating fixtures via points. The program is therefore a useful interface to other small-scale expert systems for fixture design and graphical simulators. The set-up of the fixtures can be performed for other complex shapes if locating points are known, and input into the robot controller using the C-program.

Although extensive research has been carried out in the area of tolerancing techniques for product design, concurrent engineering is still very seldom used in this context. This paper introduces a unique tolerancing method which applies the concept of concurrent engineering. The proposed method essentially allocates the required functional assembly tolerances to the component tolerances by formulating the tolerancing problem into a mathematical model and solving the model using a linear programming approach. The component tolerances are first represented in terms of the process tolerances, assigned by process planners at an early stage of the product design. The objective function of the mathematical model, which is to maximise the residual tolerances of the processes, is then established and the constraints formulated based on the assembly requirements and process constraints. The model is subsequently solved using a linear programming approach. Finally, the proposed method is tested on a practical example.

This paper seeks to verify that the existing hypotheses, which predict the natural resting aspects of small engineering parts on soft and hard surfaces, are able to predict the orientation of parts on the track of a vibratory bowl at different vibrating amplitude levels. Most of the existing hypotheses developed were verified using the “drop test” method in which parts were repeatedly dropped from a certain height onto a surface in order to analyse the natural resting behaviour of parts. This paper describes an attempt to conduct accurate experiments in the laboratory to examine the probabilities of the feed orientation of square and rectangular components of different aspect ratios by varying the vibration amplitude levels and surface textures of the vibratory bowl. The experimental results were compared with the predictions of the hypotheses postulated first by Ngoi, Lye and Chen [1], secondly by Boothroyd [2] and thirdly by Ngoi, Lim and Lee [3]. The experimental results were found to agree well with those predicted by the hypotheses. Moreover, it is also observed that the vibrating amplitude of the vibratory bowl does not significantly affect the orientation of the parts.

This paper presents a simple graphical method to represent the process links between surface planes, and leads to ease in performing the validity of a process plan. The approach used the linear optimisation software, LINDO, to solve the respectively linear working dimension and manufacturing tolerance equations. An example is also included to illustrate the method.

In recent years, non-traditional machining processes have been growing in popularity and their applications have continued to increase. However, very limited research work has been carried out to investigate their economic implications on tolerance allocation. This paper reports on cost-tolerance relationships for non-traditional processes, namely, electrical discharge wire machining and laser beam machining. Medium carbon steel plates are machined using the two processes to obtain cost-tolerance data which are fitted to various mathematical models. A third-degree polynomial function has been found which gives the most representative fit to the data obtained. An example is presented to illustrate the application and to compare the cost implication of the two machining processes.

This paper concerns the modelling of cost-tolerance data for various manufacturing processes and the optimisation of process sequences based on minimum production cost. A natural spline model representing the cost-tolerance relationship is introduced. A methodology to optimise the process sequences is developed using an expert system approach. An example to illustrate the methodology and the optimisation model is presented

This paper describes a heuristic algorithm for optimising the layout of a robot workcell. The algorithm attempts to minimise the total path of travel of a robot arm for a given sequence of operations by determining the relative positions and orientations of the stations in the workcell. A unique spatial representation system is used to model the shapes and orientation of the stations in the workcell. The representation is very flexible and can closely represent the shapes of many common types of peripheral machine encountered in a robot workcell. The algorithm has been implemented on an IBM compatible PC and the results obtained are promising.

This paper presents the technique for checking collision of through-hole components during the machine insertion process on a printed circuit board (PCB). The spatial representation technique is used to represent the components and the mounting head of an insertion machine. An algorithm that simulates the insertion process is written to detect any collision of component and mounting head during the insertion process. When a collision is detected, the algorithm will attempt to avoid the collision by re-sequencing the components concerned. If resequencing does not avoid the collision, the algorithm will compute a minimum safe distance for the affected component. The algorithm can also detect component collision due to components' space overlapping each other and subsequently can provide the minimum safe distance. The required safe spacing is based on the type of mounting head or machine used. The algorithm is a useful and efficient tool that could be used during the PCB design stage. The effectiveness of the spatial representation technique has been demonstrated using the TDK VC-544R/AR insertion machine.

Many tolerance allocation methods based primarily on cost optimisation have been developed in recent years. However, the dimensions of the assembly parts are usually determined by convenience or design constraints other than the requirements of the assembly itself. The dimensions are often determined to give sufficient clearance during assembly without much consideration given to their tolerances. This is usually followed by a tolerance analysis to check for interference. The dimensions are then adjusted to eliminate any interferences. There is no control over the size of the clearance of an assembly. This paper presents a new approach of dimensioning the components of an assembly which would allow real control over the size of clearance or interference in an assembly. A unique algorithm in conjunction with a relationship matrix is developed to formulate the dimensions in a tolerance chain into a linear equation. This linear equation is then used to develop the tolerance analysis module. The dimensioning module is accomplished using a separate algorithm in conjunction with the linear equation established. The tolerance analysis and the dimensioning modules are subsequently tested on a number of examples.

This paper presents a simple and systematic approach to the tolerance charting process. A model representing the process links, as well as their associated signs, is constructed directly from the process plan in accordance to the operation sequence. The appropriate process links between any two feature planes are then captured off-line easily from the model. After establishing the links, constraint equations on working dimensions and tolerances are formulated. Having derived all the necessary relationships, the unknowns are solved using LINDO, a linear programming optimization software. The effectiveness of this method lies in its simplicity in constructing the model without the need to employ any comprehensive algorithms. Also, computations on unnecessary variables are avoided when employing this ‘Window’ method.

This paper presents a new approach for analysing the natural resting behaviour of a non-rotational component. The method employs the energy envelope concept to analyse the natural resting of a component. The resultant curves for all the prisms agree well with Boothroyd's theoretical curve and Boothroyd's experimental data.

UV embossing combined with focused ion beam lithography (FIB) and soft lithography is demonstrated to be a viable method for quick and accessible three-dimensional large-area sub-micrometer patterning of biocompatible films. FIB lithography of titanium nitride thin film is also demonstrated to produce a very smooth surface suitable for nanopatterning.

SUMMARY This papers introduces a new approach to predicting the natural resting behaviour of a prismatic part of irregular cross-section. The methods proposed by Boothroyd et al. (1972) and Boothroyd and Ho (1977) were successful in analyzing parts with geometrically simple configurations, although empirical factors were used in the former case. For the past 16 years or so, however, no attempt has been made to analyze pans with complex shapes. Up to now, the study of the natural resting behaviour of complex shapes was conducted by approximating or simplifying the two stated methods. Considering the fact that most parts encountered in industry are not geometrically simple, this practice is the norm rather than the exception. The hypothesis presented in this paper proposes that the probability of apart coming to rest on any of its many feasible resting surfaces is directly proportional to the centroid solid angle and inversely proportional to the height of the centroid from that surface. No empirical factor...

This paper presents a new approach in the analysis of the natural resting behaviour of a component with a displaced centre of gravity. The methods proposed by Boothroyd et al. (1972), and Boothroyd and Ho (1977), can analyse parts with the centre of gravity located al their geometric centre. Hitherto, the only attempt at analysing pans with displaced centres of gravity entailed the use of empirical factors (Boothroyd et al. 1972). The hypothesis presented herein makes use of the centroid solid angle concept to analyse a component with a displaced centre of gravity. The proposed hypothesis postulates that the probability of a part coming to rest in its various natural resting aspects is directly proportional to the magnitude of the centroid solid angle and inversely proportional to the height of the centre of gravity from that aspect. The experimental results of drop tests conducted on a test specimen corroborate the hypothesis within a maximum deviation of 4%. This is the first successful attempt in the a...

In electronics manufacture, discrete components are commonly conveyed and oriented in high volume devices such as vibratory bowl feeders, the efficiencies of which depend, to a large extent, on some fore-knowledge of the probabilities of the orientation of the components prior to entering the devices. The research discussed in this paper is motivated by the fact that a simple and effective analysis of these probabilities is wanting. A new approach, employing the concept of the centroid solid angle of the component, is presented. The hypothesis postulates that the probability of a component resting on a specific aspect is directly proportional to the magnitude of the centroid solid angle and inversely proportional to the height of its centroid from that aspect. When the hypothesis is applied to prismatic parts of square, triangular, hexagonal, cylindrical and rectangular cross-sections, the results were found to agree well with those derived by the Energy Barrier Method postulated by G. Boothroyd and associates.

In the research described in this paper, an approach that utilizes deep models of features to transform a component design represented by neutral features into domain-specific features has been developed. The neutral features are known as feature-oriented generic shapes (FOGSs). The proposed approach provides the flexibility needed to represent both the deep and shallow knowledge required in feature mapping. A deep model of a feature is represented in the form of a face connectivity graph (FCG) that embodies deep knowledge about its geometry, while other non-geometrical information can be represented as rules or procedural functions. By comparing the original faces of a product model with those of the resultant evaluated boundary model, faces of interest can be easily extracted and described using FCGs. A FCG can then be examined to determine its class and the relevant parameters for applications in such domains as process planning. The mapping shell is designed with layered architecture that makes it highly appropriate for implementation using blackboard technology.

This paper introduces a simple and direct method to derive process links between feature planes. Consequently, the relationship between process and blue-print dimensions can be expressed as an array of linear equations and inequalities. By applying appropriate constraints to these models, the desired working dimensions and tolerances can be solved using LINDO, a linear programming optimization software. An example is also included to illustrate the method.

We address some key issues pertaining to geometric tolerancing and propose a simplified method to solve working dimensions and tolerances in 2D space. Geometries that exhibit characteristics similar to linear dimensions are identified. With minor changes, geometrical control requirements can be expressed as ‘equivalent’ dimensions and tolerances and can be applied to a tolerance chart directly. The conversion schemes for short-listed geometries will be tackled accordingly. We also focus on how the process links can be derived from the process plan and outline the strategy to achieve the optimal tolerance mix or combination. An example is included to demonstrate the methods used.

The selection and sequencing of orienting devices used in vibratory feeders is integral to the design of the feeders. However, because of the lack of organized, published guidelines, the selection and sequencing of orienting devices depends almost entirely on the experience of the skilled artisans who tool up the vibratory feeders. This paper discusses a knowledge-based framework by which a CAD model of the part to be oriented and fed is analysed for its significant orienting feature(s), and a suitable match of orienting devices is determined. The outcome of a consultation with the expert advisor typically yields more than one feasible sequence of orienting devices, leaving the user free to decide on the most appropriate sequence to adopt. The paper also discusses the hierarchical classification of the features of the part, as well as those of the orienting devices. The knowledge-based advisor was implemented on a 486-DX33 personal computer within the Microsoft ® Windows 3.1 environment, which integrates both the CAD and the expert system. A benchmarking exercise carried out for two rotational and two prismatic parts yielded solutions that compared favorably with those used in industry, and those proposed by the UMASS system.

This paper proposes the construction of an energy envelope that can be used to advantage with the energy barrier method to analyse the natural resting aspect of engineering parts destined for automatic assembly. Unlike the energy barrier method, the energy envelope does not require any visualization of the projection of the energy barrier on the aspect of interest. The energy envelope is the three-dimensional topology of the changes in height of the centroid, as the part attempts changes of aspect. The paper describes how it may be computed in a CAD (computer aided design) solid modeller. The results of applying the energy envelope to prisms of square and cylindrical cross-sections are the same as those predicted by the energy barrier method. When extended to the analysis of a rectangular prism, the results were consistent with Boothroyd's dynamic solution and Boothroyd's experimental data. This conclusion is encouraging as there is no irrefutable evidence that the energy barrier method may be applied to the analysis of the rectangular prism.

Correct part orientation has been the key to many successful automation applications, and often vibratory bowls were used. Traditionally, the design and tooling of the vibratory bowls are limited to a group of skilled experts. In this paper a feature-based framework for the automatic selection and sequencing of orientating devices is presented. A direct link between part representation and the selection and sequencing of modular orientating devices is provided by a spatial technique, in place of traditional CAD representation. Also described is the classification of a part's orientating features and classification of orientating devices. These two classifications are integrated into a knowledge-based system that will automatically generate sequences of modular orientating devices.

We present a simplified approach of deriving the working dimensions between surfaces of a workpiece during tolerance charting. Unlike other methods, it does not require any representation of the machining sequence. The dimensional chains are first formulated into a matrix and it is then solved by applying the Gauss elimination technique. We also describe an elegant method of deriving the balanced tolerances of a workpiece during tolerance charting. The process links between surfaces are derived by using a special tracing technique. With the process links obtained, the balanced tolerances are solved by using a separate mathematical model. An example is used to illustrate the method.

Integrated circuit (IC) manufacturing demands highly automated assembly due to compact IC design so as to maintain high volume production at low cost. Trim and form operations are important tasks in the manufacturing of microprocessors, memories and programmable logic devices. Inspection and evaluation of the product specifications of IC leads (after trim and form operations) are performed in a lead inspection machine to obtain results for statistical process control (SPC). The results are then checked against the prescribed control limits and appropriate actions are taken to ensure consistent performance of the trim and form machines concerned. The process of picking and placing the IC units individually into the testing compartment of the lead inspection machine is done manually. Such an operation lacks consistency in material handling. The objective of this work is to design and to develop an automated material-handling system that can be interfaced to a lead inspection machine. It is motivated by the ‘overdesign’ and excessive cost involved in a highly automated lead inspection system that incorporates material handling capabilities. The developed automated handling system has been evaluated successfully for its functionality. Besides the non-economic benefits derived from such work, its initial rate of investment (ROI) of 1.34 years is economically justified. The development of such a low-cost automated handling system (which can be incorporated into a lead inspection machine) is able to benefit electronics industries with similar setups. The design outline presented in this paper can serve as general guidelines in such development work.

Tolerance accumulation, as a result of over-specification or under-dimensioning by the designer, determines how easy a product is to assemble. The result is either impossibly tight fittings, or excessive clearance, which affect the final performance and quality of the assembly. This is particularly true of the compact assemblies encountered in microelectronics products, such as portable phones, pagers and disk drives. The effectiveness of the design evaluation stage may determine a company’s success in product launches, and its profitability. Every year millions of dollars are wasted on unnecessary changes in engineering drawings, reprogramming of assembly lines, and reworking or even scrapping of products. Tolerance analysis and tolerance synthesis are therefore indispensable tools for designers and process planners when they are evaluating the designed product. Tolerance analysis is used to determine the final assemblability of components with specified individual tolerances. Its inverse, tolerance synthesis, ensures the reasonable and economical distribution of assembly tolerances on each component, thus helping to optimize product cost, quality and—ultimately—function. This paper summarizes over 100 publications to provide a review of the current state of the art in such research, and to point the way towards possible future research.

This paper describes an efficient method of packing boxes into a container using a unique spatial representation technique. Unlike other algorithms, the packing algorithm in this paper is not constrained by the physical packing sequence, that is, back to front, or bottom to top. This extra flexibility allows the program to pack the boxes more efficiently. The packing plan can be generated to suit the actual packing sequence. The program is implemented on an IBM PC and a comparison has been made with a similar software. The results, in terms of packing efficiency and packing time, are promising.

Conventionally, working dimensions have to be given before the construction of a tolerance chart can begin. Because the method of determining the working dimensions is based on trial and error, it is tedious and time-consuming. This paper proposes a method that can generate the working dimensions automatically from the process sequences and the blueprint dimensions. The method uses a relationship matrix to represent the process sequences and a special path-tracing technique to identify the process links. A unique algorithm is developed to reduce the unknown working dimensions to a system of linear equations, which is then solved using the Gauss elimination technique. This method can either be adopted by the process planner or implemented on a microcomputer. With this method, different processing sequences based on different factors, e.g. cost, machining time, etc., can be evaluated efficiently and economically. The developed program is then tested on a practical example.

Conventionally, the process sequence has to be known before the construction of the tolerance chart can begin. The determination of the process sequence requires extensive knowledge and experience on the part of the process planner. This paper describes a method of determining the process sequence automatically using a special profile representation method. The method uses a two-dimensional matrix, incorporating a number coding system, to model the part profile. A feature interpretation system is then developed to search and analyse the features using the ‘top-down’ approach and to assign the appropriate processes to each of them individually. An example is used to illustrate the method.

This paper presents a unique method of deriving the dimensions and tolerances during tolerance charting. It is simple and practical. Unlike other methods, it does not require any representation of the machining sequence. The dimensions/tolerances between workpiece surfaces are organised into an input matrix. The input matrix then undergoes a series of operations to yield the final matrix. The final matrix contains the resultant dimensions/tolerances between any two surfaces of the workpiece. This method is easy to understand and implement on a microcomputer. An example is used to illustrate the method.

A type of cellular-decomposition, solid-model representation based on variable orthorhombic cells and using a threedimensional matrix data structure is presented. It was developed to do two things that other representation methods cannot do easily or quickly. This method directly provides information concerning intersecting components, and it is fast enough to allow checks for intersection to be made in iterative routines. The method has application to layout design where interference checking is important. The method and the essential algorithms are described. An application to fixture design is presented.

Manual computation of tolerance charts is both tedious and time-consuming. This paper presents an efficient method of automatically determining the working dimensions and their balanced tolerances. With this method, the feasibility of different process plans can be evaluated efficiently and economically. A unique algorithm, based on a special path tracing technique, is developed to reduce the unknown working dimensions to a system of linear equations. The Gauss elimination technique is then employed to solve for the working dimensions. The tolerance balancing process is accomplished using a separate mathematical model. The complete system, comprising the tolerance charting and optimization modules, is finally tested on an example.

Laser machining of submicron grooves on silicon wafer by 400 nm femtosecond laser is studied. A chirped pulse amplification based Ti:sapphire system that produces pulse with a pulse duration of 150 fs at a repetition rate of 1 kHz is used. Focusing lens with numerical aperture of 0.36 focuses the laser beam into a 3 μm laser spot (by calculation). The sample was translated at a linear speed of 400 μm/s during machining. 500 nm wide 100 nm deep groove was obtained on the wafer when the sample was irradiated by pulses with energy of ∼50 nJ/pulse and 800 nm wide 650 nm deep groove was obtained by pulse with energy of ∼100 nJ/pulse.

This paper explores an important aspect of tolerance charting, i.e. tolerance chart balancing. A mathematical model for tolerance chart balancing, based on the “rooted tree” representation technique, has been established. The mathematical model, which represents a resource allocation problem, is then solved by using the linear programming approach. An example is used to illustrate the method. A comparison between the results generated by the proposed method and the manual method is also included.

The heterodyne laser interferometer has gained popularity in applications as an encoder system in ultra-precision machines. It can provide ultra high resolution, which satisfies the requirements of ultra-precision machines. The difficulty of using a laser interferometer is the elimination of the effects of change of the refractive index of air whether by variation in environmental conditions or by external effects like air movement, air vibration and mechanical vibration. This paper presents a new technique for the elimination of the effect of refractive index when using a heterodyne laser interferometer. The preliminary results showed that this set-up has a better static error when compared to an industrial laser system.

The unique ability of the ultrafast lasers to perform sub-spot size machining has been proved to be advantageous over conventional lasers for sub-micron-machining. To achieve this, a Gaussian laser beam free of spatial defects is essential. In this research work, submicron holes with clear edge and symmetric shape on thin metal films using a Ti:Sapphire regenerative amplified femtosecond pulsed laser are produced. While analysing, it is observed that there are two shallow pits accompanying the produced hole, symmetrically located at the two sides of the hole, especially when the holes are in the sub-micron range. A careful study on the effects of these shallow pits and the methods to eliminate the same are presented in this letter. It has been concluded that the shallow pits are Rowland ghosts raised by deficiencies of grating space present in the two pairs of gratings used for pulse stretching and compressing. Methods of eliminating these ghosts to achieve features with better edge acuity and quality are also presented.

The present work relates to surface and/or subsurface defects inspection system for semiconductor industries and particularly to an inspection system for a defect such as swirl defects and particles in an unpolished silicon wafer before the wafer fabrication process by a combined fiber optic digital shearography and holography technique. The dual purpose camera described in this paper gives the possibility of using either digital shearography or holography (DSPI) techniques depending on application needs. The sub-surface defects in a wafer normally create strain concentrations subjected to loading (stressing) which are translated into anomalies in the fringe pattern. A real time technique with the use of Lab view Express 7 software is developed to detect defects in Si-wafer with the application of thermal oading as a stressing method. The results obtained by applying a real time fiber optic shearography technique are described in this paper. The method described here relates specifically to semiconductor wafers, but may be generalized to any other samples.

In ophthalmology, the use of femtosecond lasers is receiving more attention than ever due to its extremely high intensity and ultra short pulse duration. It opens the highly beneficial possibilities for minimized side effects during surgery process, and one of the specific areas is laser surgery in glaucoma treatment. However, the sophisticated femtosecond laser-ocular tissue interaction mechanism hampers the clinical application of femtosecond laser to treat glaucoma. The potential contribution in this work lies in the fact, that this is the first time a modified moving breakdown theory is applied, which is appropriate for femtosecond time scale, to analyze femtosecond laser-ocular tissue interaction mechanism. Based on this theory, energy deposition and corresponding thermal increase are studied by both simulation and experimentation. A simulation model was developed using Matlab software, and the simulation result was validated through in-vitro laser-tissue interaction experiment using pig iris. By comparing the theoretical and experimental results, it is shown that femtosecond laser can obtain determined ocular tissue removal, and the thermal damage is evidently reduced. This result provides a promising potential for femtosecond laser in glaucoma treatment.

A speckle shearing interferometric system is proposed for real-time inspecting sub-surface defects of unpolished silicon wafer. Under dynamic thermal loading, derivative distribution of out-of-plane displacement along a shear direction is measured and homogeneity and regularity of the distribution is indicator of whether impurities or voids exist under the wafer surface. During a continuous thermal stressing, a sequence of speckle patterns are obtained and phase analysis is implemented in time domain. In this paper, the validity of the method for non-destructive testing of sub-surface defects of silicon wafers has been demonstrated.

Wavelength tuning of fiber Bragg gratings (FBGs) by virtue of a lateral or transverse load is attractive for a variety of applications in the field of optical sensing. The wavelength response characteristic of the FBG upon application of a transverse load is highly dependent on the pressurizing media and the contact conditions. In this paper, we evaluate the effect of contact friction and contact angle of the pressurizing media on the lateral pressure tuning of FBGs. Our results showed that pressurizing media with a lower value of stiffness is favorable for greater contact areas and for distributing the lateral load. Thus, the sensing load becomes more hydrostatic in nature, which enhances the lateral pressure sensitivity and tuning range while reducing birefringence. Also, a higher contact friction is favorable for effective transfer of the load through the contact area and improved sensitivities accordingly. The present study is thus useful in better utilization of lateral pressure tuning of FBGs for sensing applications.

Silicon mold fabricated with Focused Ion Beam lithography (FIB) was used to make silicone elastomer molds. The silicon mold is composed of lattice of holes which the diameter and depth are about 200 nm and 60 nm, respectively. The silicone elastomer material was then used to replicate slavery mold. Our study show the replication process with the elastomer mold had been performed successfully and the diameter of humps on the elastomer mold is near to that of holes on the master mold. But the height of humps in the elastomer mold is only 42 nm and it is different from the depth of holes in the master mold.© (2004) COPYRIGHT SPIE--The International Society for Optical Engineering. Downloading of the abstract is permitted for personal use only.