The integration of process planning and machine loading in small batch part manufacturing

PART is a highly automated planning system in which both process and production planning functions are integrated. This paper discusses a method to improve machine tool selection in process planning by integration with loading. A method is presented to select the best process plan from a number of possible alternatives taking into account the limited availability of resources. Various aspects of the quality of a process plan are evaluated and expressed in the so-called evaluation time. To prevent redundant work, partly worked out process plans are considered as alternatives. The consequences of the different alternatives have to be estimated which includes the estimation of machining times. The loading problem is modelled as the minimization of the total evaluation time for a given order set, subjected to capacity constraints

Recent Developments in Tolerancing Techniques

Mechanical tolerances are specified in conjunction with part geometry, material type andother technical specifications during the design of mechanical components and assemblies., These tolerances ensure the expected design function, and provide guidelines for the manufactureof designed parts. However, assigning proper tolerances for a design is a non-trivial task. Thispaper reviews the recent developments in the field of tolerancing techniques, particularly withreference to the use of computers, cost tolerance relationship and tolerance design for qualityimprovement of the product

Study on Genetic Algorithm Improvement and Application

Genetic Algorithms (GAs) are powerful tools to solve large scale design optimization problems. The research interests in GAs lie in both its theory and application. On one hand, various modifications have been made on early GAs to allow them to solve problems faster, more accurately and more reliably. On the other hand, GA is used to solve complicated design optimization problems in different applications. The study in this thesis is both theoretical and applied in nature. On the theoretical side, an improved GA�Evolution Direction Guided GA (EDG-GA) is proposed based on the analysis of Schema Theory and Building Block Hypothesis. In addition, a method is developed to study the structure of GA solution space by characterizing interactions between genes. This method is further used to determine crossover points for selective crossover. On the application side, GA is applied to generate optimal tolerance assignment plans for a series of manufacturing processes. It is shown that the optimal tolerance assignment plan achieved by GA is better than that achieved by other optimization methods such as sensitivity analysis, given comparable computation time

A graph-based method and a software tool for interactive tolerance specification

Abstract The paper deals with the problem of tolerance specification and, in particular, proposes a graph-based method and a preliminary software tool: (i) to accomplish the tolerance specification for a mechanical assembly; (ii) to verify the consistency of the specification and, (iii) to allow the tracing of relationships among parts and features of the assembly. The method adopts Minimum Reference Geometric Elements (MRGE), directed graphs (di-graphs) and a set of dedicated algorithms to tackle the problems of consistency that occur during an interactive tolerance specification activity. Finally, an application illustrates the proposed method and its actual implementation

A Slope-Based Method for Least Cost Tolerance Allocation

In this paper, a new methodology is presented to solve the tolerance allocation-process selection problem simultaneously The prob lem is modeled using discrete and continuous variables and is transformed into a model with only continuous variables by defining an efficient tolerance-cost curve for each component Since the efficient tolerance-cost curve is neither convex nor concave, nonlinear programming method ologies cannot be directly applied The tolerance-cost curve is piecewise linearly approximated and an efficient methodology is developed to solve the problem The method starts with a solution which minimizes the objective function value but is not feasible The infeasibility is iteratively reduced in a way that the increase in the objective function value is minimal Computational analysis indicates that the method is very robust and requires negligible CPU timeYeshttps://us.sagepub.com/en-us/nam/manuscript-submission-guideline

Variational Analysis for CNC Milling Process

Abstract Dimensional and geometrical defects severely affect the quality of chip removal processes in CNC machines. In order to improve the accuracy, a long and expensive calibration process is usually performed on the CNC machine. The tuning process could be easier and faster if the designer is able to evaluate the effect of error sources providing a more robust and reliable CNC machine. The joined use of variational analysis and finite element analysis of geometrical features forecasts the position error of the tool tip

Automatic post-processing for tolerance inspection of digitized parts made by injection moulding

This paper presents the advancements of an automatic segmentation procedure based on the concept of Hierarchical Space Partitioning. It is aimed at tolerance inspection of electromechanical parts produced by injection moulding and acquired by laser scanning. After a general overview of the procedure, its application for recognising cylindrical surfaces is presented and discussed through a specific industrial test case