Nikolay Guschinsky

Graph approach for optimal design of transfer machine with rotary table

A line balancing problem for transfer machines with rotary tables is considered. This type of machine is used in mass production. A part is sequentially machined on m working positions and is moved from one position to the next using a rotary table. The operations are grouped into blocks, where the operations of the same block are simultaneously performed by one piece of equipment with several tools (a multi-spindle head). All multi-spindle heads of a machine are simultaneously activated. Therefore, all operations of the machine are executed in parallel on m parts mounted on the rotary table. The line balancing problem consists of partitioning the set of all operations into sub-sets in order to minimize the number of working positions and the total number of spindle heads while satisfying all the constraints (precedence, compatibility for spindle heads, etc.). The method proposed in this paper is based on transforming this line balancing problem into a search for a constrained shortest path. An algorithm for simultaneously generating a graph and finding a constrained shortest path is developed. Some dominance rules for reducing the graph size are provided. An industrial example is presented in detail and experimental results on other industrial instances are reported.

Balancing large-scale machining lines with multi-spindle heads using decomposition

The paper deals with optimal logical layout design for a type of machining lines. Such lines are made of many machine-tools (workstations) located in sequence. On each workstation there are several multi-spindle heads. A spindle head does not execute one operation but a block of machining operations simultaneously. The problem studied in this paper consists of finding the best partition of the set of all operations to be executed on the line into blocks and workstations. The objective is to minimize the number of blocks and workstations. An optimal decision must satisfy a desired productivity rate (cycle time) and precedence and compatibility constraints for machining operations. A heuristic approach based on decomposition of a Mixed Integer Programming (MIP) model is developed. Two ways of forming sub-problems are proposed. One treats the obtained subsets independently. The second aggregates the solution of the previous subproblems. Results of their computational evaluation are reported.

Balancing production lines composed by series of workstations with parallel operations blocks

A balancing problem for paced production lines with workstations in series and blocks of parallel operations at the workstations is considered. The problem is to choose blocks from a given set and allocate them to workstations in such a way that all the operations are assigned, the precedence and compatibility constraints are satisfied, and the line cost is minimal. A method for solving the problem is based on its transformation to a constrained shortest path problem.

Optimal design of a class of transfer lines with blocks of parallel operations

Abstract A problem of optimal design of automatic transfer lines is considered. For these lines, operations are partitioned into blocks. The operations of the same block are performed simultaneously, and different blocks of the same workstation are executed sequentially. The relations of the necessity and the possibility of combining operations in blocks and workstations as well as precedence constraints are given. The problem is to minimize the total number of workstations and blocks, providing a given cycle time and satisfying the above constraints. Two methods are proposed to solve the problem. The first one uses mixed integer programming, the second is based on reducing the initial problem to the shortest constraint path problem.

Integrated Approach for Design of Machining Systems

In this paper we present the prototype of a decision support system for logical layout design of machining systems. The approach and developed decision support system are focused on systems which are used in the mass production of a unique product or a family of similar products. In these lines, the machining operations are realized on working positions equipped by standard modular spindle heads. The part transportation from a working position to the next one is synchronized. The spindle heads selected and their layout define the system productivity and the final cost. The paper present a novel approach and depicts mathematical and decision-aid methods developed and implemented in the software tool for optimization of each design (or reconfiguration) stage of such a line, in particular, a method for finding the optimal logical layout.

Some Optimization Approaches for Transfer Lines with Blocks of Operations

Abstract In this paper some algorithms which can be used to minimise the line cost of lines where operations can be executed simultaneously (for example by a spindle head) on workstations in series are presented: the operations can be grouped in blocks of parallel operations. The duration of the longest operation of a block is its processing time; the workstation time is the sum of processing times of its blocks. Two types of methods are proposed: the first one is based on a MIP model, and the second one on random search heuristic. Some comparisons are given

Decomposition Methods to Optimise Transfer Line with Parallel and Sequential Machining

Abstract This paper is devoted to a preliminary design problem of synchronised automatic transfer lines. The aim is to minimise the line life cycle cost per piece under the given productivity and technological constraints. The paper focuses on a mathematical model of the problem and methods to solve it. The model is formulated in terms of mixed (discrete and non-linear) programming. For solving the optimisation problem, a special decomposition scheme is proposed, which is based on parametric decomposition technique.