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  • 1
    ISSN: 1433-3015
    Keywords: Collision-free ; PCB ; Spatial representation technique
    Source: Springer Online Journal Archives 1860-2000
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Notes: Abstract 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.
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  • 2
    ISSN: 1433-3015
    Keywords: Component dimensioning ; Optimum assembly
    Source: Springer Online Journal Archives 1860-2000
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Notes: Abstract 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.
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  • 3
    ISSN: 1433-3015
    Keywords: Automation ; Fixture set-up ; Inspection
    Source: Springer Online Journal Archives 1860-2000
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Notes: Abstract 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.
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  • 4
    ISSN: 1433-3015
    Keywords: Linear optimisation software ; Tolerance charting
    Source: Springer Online Journal Archives 1860-2000
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Notes: Abstract 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.
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  • 5
    ISSN: 1433-3015
    Keywords: Geometric dimensioning and tolerancing ; Graphical model ; Stack analysis
    Source: Springer Online Journal Archives 1860-2000
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Notes: Abstract 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.
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  • 6
    ISSN: 1433-3015
    Keywords: Key words. Assembly requirement; Dimensioning; Tolerancing
    Source: Springer Online Journal Archives 1860-2000
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Notes: Dimensioning and tolerancing are both important phases of product design. Although dimensions can usually be assigned based on design constraints and aestheticism without much difficulty, tolerancing is often a major problem to designers. Traditionally, tolerances are assigned intuitively followed by an analysis to check for any violation of the assembly requirements. Based on the analysis results, modifications are made manually by a "trial and error" method. This method relies on the experience of the designers and the results may not be optimal. 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.
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  • 7
    ISSN: 1433-3015
    Keywords: Keywords:Brittle; Cleavage plane; Ductile regime; Grinding; Slip plane; Turning
    Source: Springer Online Journal Archives 1860-2000
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Notes: Many of today's products require high precision and operate in extreme environments. To meet these demands, new types of high-performance materials and machining techniques have been developed. The use of these machining techniques , enables these materials to achieve nanometric tolerances. Ceramics are one group of such materials, which can be used in high-performance applications because of their high stiffness, dimensional and temperature stability, and resistance to chemical environments. The brittleness of these materials poses problems during machining, but the demand for precision parts made of these materials are increasing at a fast rate. Experiments have shown that plastic flow can occur in ceramic materials, so they can be ductile machined. However, much needs to be determined in respect of the cutting conditions to enable this ductile behaviour to be successfully maintained throughout the machining processes such as turning or grinding.
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  • 8
    ISSN: 1433-3015
    Keywords: Key words.Encoder; Ultra-precision measurement; Refractive index compensation; Heterodyne laser interferometer
    Source: Springer Online Journal Archives 1860-2000
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Notes: Abstract. 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.
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  • 9
    ISSN: 1433-3015
    Keywords: Geometric tolerancing ; Tolerance analysis ; Tolerance charts
    Source: Springer Online Journal Archives 1860-2000
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Notes: Abstract The development of tolerance charts has come a long way from the past manual methods to the current computer-aided models. As a result, many techniques have emerged over the years. However, the area of geometrical tolerance charting has not been given much attention. In view of this, this paper addresses both linear and geometrical tolerance control. The method proposed in this paper allows the user to construct a model directly from the process plan. The relevant process links between any two planes which are required to satisfy both the linear and geometrical requirements are easily obtained from the model. Having established all the appropriate constraints, the linear programming optimisation software is used for the determination of the unknown working dimensions and tolerances. In essence, this paper presents a new methodology for deriving the process links from the process plan and also highlights the significance of the use of linear programming in achieving the optimal tolerance mix or combination.
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  • 10
    ISSN: 1433-3015
    Keywords: Automated assembly ; Natural resting aspect ; Vibratory-bowl
    Source: Springer Online Journal Archives 1860-2000
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Notes: Abstract 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.
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