Krzysztof Kalinowski

Integration production planning and scheduling systems for determination of transitional phases in repetitive production

In the process of multiassortment repetitive production planning the designation of operating system parameters for the steady state (in which after the last operation the return to the first operation in the sequence of productive resources occurs) is required. The length of steady state of the system is determined by the work of the critical resource. Determination of resources sequence for the steady state gives possibility to determine the processing times for processes in the system without taking into account the transitional phases. During the execution of this type of production, in addition to the phase in which production takes place in the steady state, transition phases connected with starting (start-up phase) and finishing work in the system (cease phase), and the phases associated with the changes in ongoing sequences in steady states can be distinguished. The article presents the problem of estimating the duration of the start-up phase and the cease phase in the concurrent multiassortment production systems, in which access to the resources is regulated by the local dispatching rules. A method and a procedure of creating a schedule for the transition phases using the integration between the systems of production planning and scheduling is presented. The demonstrated approach is illustrated with the examples using KbRS and SWZ systems.

Object-oriented models in an integration of CAD/CAPP/CAP systems

In this paper some aspects of CAD/CAPP/CAP systems integration process are described. Moreover, the structure of an integrated environment, which is an answer to this kind of integration problem is shown. Main elements of this environment are technological knowledge base - TKB and scheduling knowledge base - SKB. The foundation for building these knowledge bases was application of object methods in processes of technological and scheduling knowledge representation. In the paper both models it means the object model of technological knowledge representation and scheduling knowledge representation are discussed in details.

Preparatory Stages of the Production Scheduling of Complex and Multivariant Products Structures

The paper presents the way of creating a scheduling model for manufacturing systems where complex and multivariant structures of products are considered. Described method of scheduling tasks modelling, based on graphs, includes stages of building graphs of operations planning sequence of orders (taking into account their scheduling strategies and alternatives of realisation), input sequencing of the set of production orders and also creation of the aggregated graph of operations planning of the set of orders. The developed model is the basis for the implementation in the APS and simulation type of scheduling software, supporting production planning and scheduling. Because of NP-complete character of considered scheduling tasks, it is a potential application area of soft computing graph searching techniques.

The hybrid method of knowledge representation in a CAPP knowledge based system

In this paper the hybrid method of manufacturing knowledge representation in the CAPP knowledge based system is presented. In the presented solution the manufacturing knowledge as well as the product design is represented by means of the object method. This paper shows only results obtained at the object design stage (OOD). Currently the scope of decision problems solved by proposed system is limited to axi---symmetric products, but basis on the achievements to date it is thought to develop this system in order to widen the subjected products group. Moreover the detailed description of the inference engine of the CAPP system is given. In the inference engine the two groups of rules were distinguished. In the paper content the examples for each group of rules are shown.

The Graph Representation of Multivariant and Complex Processes for Production Scheduling

The paper presents a solution useful for production scheduling in the context of the constraints arising from the complexity of the structures of realized processes and possibilities of use variants of their implementation. The proposed method uses both activity on arc and activity on node types of graph for describing multivariant processes. Representation of complex (composed) structures the AND-OR graphs are used that combines both conjunction and disjunction relations between nodes.

Pareto Optimality of Production Schedules in the Stage of Populations Selection of the MOIA Immune Algorithm

In the paper, the problem of achieving Pareto optimal solutions set with application of the elaborated Multi Objectives Immune Algorithm is presented. The Pareto frontier provides a variety of compromise solutions for contradictive criteria to a decision maker. We propose the application of the selection based on the Pareto optimality to maintain solutions with great diversity in an immune memory. Stimulation and suppression mechanisms are used to control the diversity of generated solutions. Computer simulations are done for a job shop scheduling problem.

Predictive - Reactive Strategy for Real Time Scheduling of Manufacturing Systems

In this paper a solution of soft real time scheduling in manufacturing systems is presented. The basic requirements of scheduling as a real time system are discussed. The proposed rescheduling method uses predictive-reactive strategy and multi thread searching approach with rule-based heuristics, meta-heuristics and random modules.

Estimation of Reliability Characteristics in a Production Scheduling Model with Failures and Time-Changing Parameters Described by Gamma and Exponential Distributions

In the paper a classical model of failures is considered in that successive failure-free times are supposed to have Gamma distributions and are followed by exponentially distributed times of repairs. It is assumed that parameters of these distributions, in general, change with time. Basing on information about the number of failures and failure-free times in a number of periods of the same duration in the past, three different methods of estimation unknown parameters of the model are proposed. Next, predictions of the most important reliability characteristics are found.

A Survey on Capp Systems Development Methods

Process planning is one of the most important links in planning of the manufacturing system functioning, it coordinates and integrates processes planners, designers and economists intentions. The main goal to reach during the process planning phase is to determine the process plan structure it is manufacturing operations and cuts which have to be applied in order to transform given semifinished product into a product with the strict determined design and properties. Simultaneously process planers strive for working out such a process plan which satisfies criteria of the lowest manufacturing cost and labour consumption taking into account current accessibility of manufacturing resources. Process planning is still one of the most difficult, complex and time consuming process planner activities. Traditionally the process plan is designed with so-called manual method. During process planning with this method a process planner is forced to analyse the sequence of manufacturing cuts and operations in the process plan structure and also to analyse alternative processes taking into consideration achieving as low as possible unit manufacturing cost. In this case the process plan quality in principle depends exclusively on process planner knowledge and skills. Taking into account above the methods of process planning functions automation are searched. This goal can be reached by application of computer tools. Computer methods of process planning went through the long evolution process and their development is characterized by the following features: decreasing of process planner participation in the planning of the base structure of process plan, broad application of technological databases, broad application of technological knowledge bases, and possibilities of cooperation with commercial CAD/CAM/CAE systems [1,. In this paper the detailed information on methods of computer aided process planning are given. The variant, semi generative and generative methods are discussed. The main merits and drawbacks for each method are shown.

Study on Transient Queueing Delay in a Single-Channel Queueing Model with Setup and Closedown Times

A single-channel queueing model with finite buffer capacity, Poisson arrival stream and generally distributed processing times is considered. After each busy period the service station is being switched off but this operation requires a randomly distributed closedown time. Similarly, after the idle time, the first service in a new busy period is preceded by a random setup time, during which the processing is still suspended and the server achieves full readiness for the service process. A system of integral equations for transient conditional queueing delay distribution is derived, by using the idea of embedded Markov chain and the formula of total probability. The solution of the corresponding system written for Laplace transforms is obtained via the linear algebraic technique. Numerical examples are attached as well.