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Complex molds and dies often need grinding to achieve the required surface finishes and tolerances. Due to complex part geometry and multiple-axis motion, the wheel-workpiece engagement conditions may vary drastically during grinding, which imposes challenges to choose the appropriate workspeeds. This paper presents a modeling approach to optimize mold and die grinding to reduce cycle time while maintaining process parameters such as grinding force and specific removal rate below critical limits. The wheel-workpiece engagement conditions are calculated for each grinding step by processing the NC program, part and wheel geometries. Grinding forces, power1, and temperature are calculated and used as decision variables to optimize workspeed to reduce cycle time. Results for grinding a half bottle shaped mold show that the grinding process parameters vary significantly along the wheel axis at any instant and along the grinding path. The grinding process is far from optimum if a constant workspeed is used. Model-based optimization has been shown to reduce cycle time by 50% while achieving much lower grinding forces and power. [ABSTRACT FROM AUTHOR]

Toroidal surfaces are used in many machinery parts such as ball bearing races, bull nose and indexable endmills, continuously-variable transmissions, and enveloping worm gears. Torisity, the form tolerance of toroidal surfaces, plays an important role in mechanical design and quality control such as component functionality, assemblability, and interchangeability. Compared with simple forms, such as planes, spheres, cylinders, and cones, toroidal surfaces are more complex and the evaluation of torisity has not been thoroughly performed. This paper proposes a nonlinear approach to evaluate torisity information using particle swarm optimization (PSO). Three sets of PSO parameters are compared based on the least-squares objective function and minimum-zone objective function using toroidal geometry characteristics. The effectiveness and robustness of the PSO approaches are validated by experiments on simulated entire, outer, inner, thrust, and endmill toroidal surfaces, which appear in various machinery components. Compared with previous studies in torisity evaluation, the proposed approach is more efficient in the ability to provide the form tolerance and the surface profile information simultaneously. The proposed approach is also more consistent with the tolerance zone definition of ASME standard Y14.5M on dimensioning and tolerancing. [ABSTRACT FROM AUTHOR]

During wire drawing processes a critical parameter is the micro-hardness distribution imposed. The present numerical and experimental investigation focused on the effects of and interdependence between processing parameters such as die angle, bearing length, lubrication, and draw speed during wire drawing. The micro-hardness distribution imparted by the drawing process was selected as the focal product quality attribute. The goal of the study was to evaluate the ability to create desired hardness levels in a drawn wire product. The numerical component of the study was performed using DEFORM- 2DTM, a commercially available metal forming software package based on the finite element method. In addition, experimental verifications of the software predictions were completed wherever possible. Full factorial designs of the processing parameters were studied, and it was found that the final hardness distribution was primarily affected by the die angle. Interactions between the four processing parameters were negligible. Based upon this finding, it was concluded that strength and hardness variations inherent to stock wire could be detected and minimized during wire drawing through the appropriate science-based selection of die angle. This could dramatically enhance the consistency of the wide range of common metal products that are manufactured from wire stock. [ABSTRACT FROM AUTHOR]

A machining fixture controls position and orientation of datum references (used to define important functional features of the geometry of a mechanical part) relative the reference frame for an NC program. Inaccuracies in fixture's location scheme result in a deviation of the work part from its nominal specified geometry. For a part to be acceptable this deviation must be within the limits allowed by the geometric tolerances specified. This paper addresses the problem of characterizing the acceptable level of inaccuracy in the location scheme so that the features machined on the part comply with the limits associated with its geometric tolerances. First we solve the "forward problem" that involves predicting the tolerance deviation resulting at a feature from a known set of errors on the locators. However, the paper concentrates on solving the "inverse" problem that involves establishing bounds on the errors of the locators to ensure that the limits specified by geometric tolerances at a feature are not violated. [ABSTRACT FROM AUTHOR]

Presents two techniques, quasi random numbers based on the Number Theoretic Method and sequential algorithm based on the Number Theoretic net, to calculate yield and to perform tolerance allocation. Importance of tolerancing in product and manufacturing process design; Demonstration of optimal tolerance design; Efficient use of algorithm to obtain global optimum, with considerable reduction in amount of calculation.

Focuses on the use a parametric and statistically-based technique for the determination of cylindrical variations in geometric tolerancing. Parametric model fitting procedure; Cylindrical form deformation determination; Detection of cylindrical variations.

Formulates the tolerance allocation problem as a nonlinear integer model under the constraints of process stability. Total cost function; Use of a complex search model to ensure optimal tolerance allocation; Numerical examples illustrating successful model implementation for both linear and nonlinear design functions.

Investigates the effectiveness of the design of experiment (DOE) approach for concurrent selection of component tolerances and the corresponding manufacturing processes. Use of the Monte Carlo simulation approach to obtain component tolerances and tolerance stackups; Discussion on the advantages of DOE over exact algorithms.

Reviews the four basic tolerancing formulae that are used for relating input and output specifications in engineering design projects. Basis of optimal tolerances; Alternative cost-distribution models; Value of design time relative to production costs.