WELDON HAND TOOLS

Weldon Hand Tools

Weldon Hand Tools

Part A

Scheduling for two-stage production system for Weldon Hand Tools including machining operations, setup operations and assembly operations is addressed, where a number of products of the same kind are produced. Each product is assembled with a set of several parts. The first stage is a single machine to produce parts. It can process all kinds of parts but can process only one part at the same time. Setup operation and setup time are needed when the machine starts processing or when the machine changes items (kinds) of parts. The second stage is a single assembly machine or a single assembly team of workers. The objective function is the mean completion time for all products. Machining operations, setup operations and assembly operations are partitioned into several blocks. Each block consists of the machining operations, the setup operations and the assembly operation(s) for one or several products. Parts of the same kind in a block are processed successively. We consider a problem to partition the operations into blocks and sequence the parts in each block so as to minimize the objective function. A solution procedure using pseudo-dynamic programming is proposed to obtain a near-optimal schedule. A tight lower bound is developed to evaluate the accuracy of the near-optimal schedule.

Generally speaking, scheduling for machining parts and planning for assembly operations have been studied independently. In some cases, however, these problems should be treated simultaneously. There are two major types of studies in which both machining operations and assembly operations are treated: type I in which more complex models are built and priority dispatching rules or heuristic methods are presented, and type II in which simpler models are considered and strict solution methods or theories associated with them are proposed.

Huang , Fry et al. and Philipoon et al. consider job-shop scheduling with assembly operations and investigate the performance of some priority dispatching rules to minimize the mean flow time or the mean tardiness. Doctor et al. investigate a model that is similar to and develop a heuristic algorithm to maximize the availability of the system subject to the due date constraints. No comparison with a strictly optimal solution is done in their papers. McCoy and Egbelu formulate a scheduling model for a process and assembly job-shop as a mixed integer programming problem, and develop a heuristic solution approach. Cheng presents an approximate method to estimate the mean and standard deviation of job flow time in a dynamic job-shop with assembly operations. In his model, each component part consists of a single operation only.

Lee et al. consider minimizing the makespan in the 3-machine assembly-type flow-shop scheduling problem. In their model, each product is assembled with two types of parts. Machine Ma processes type a, machine Mb processes type b, and machine M2 assembles the two parts into a product. They present a branch and bound solution scheme and an approximate solution procedure. Potts et al. extend the model of and develop a heuristic algorithm to minimize the ...