On the representation of timing for different structures within MRP theory

Abstract

MRP Theory has been developed during the last 25 years for capturing processes concerning multi-level, multi-stage production-inventory systems in a compact way. Input-output analysis has been used to describe structures, and Laplace transforms to describe the timing relations. This theory has mainly dealt with assembly systems, in which each item has only one successor. The lead times for the assembly of an item have usually been constants and equal for all items entering a given successor. For such systems, the equations describing the flows of components may be written to include the generalised input matrix as the product of an input matrix containing needed amounts, and a diagonal lead time matrix with lead time operators along its main diagonal. less thanbrgreater than less thanbrgreater thanOn occasion, there has been a need to deviate from this representation enabling lead times to vary depending on which input item that is considered. This paper deals with how to represent lead times and similar output delays (in diverging, arborescent systems), when the assumption of equal times is relaxed, in order to retain the basic structure of the fundamental balance equations involved. The intention of this paper is to create a general taxonomy for the representation of timing in algebraic form for a variety of systems covering both assembly systems and arborescent systems (such as extraction, distribution and remanufacturing), as well as systems with mixed properties. For instance, this method may be used directly for the evaluation of investments in capacity or in the location of activities in a production network, or even in a global supply chain

Designing MRP Model in the Condition of Capacity Constraints and Variability of Delivery for Critical Items in ABC Inventory Model “Case Study in National Company of South’s Oil-rich”

“…One of the solutions which immediately clear in the minds of anyone is that it is better to orders all items firstly and ensure to its receipt, take action toward implementation of programs and in fact, after receiving all items and making sure, starts the implementation of the project [4,11].…”

“…On the other hand, Warehouse costs is including the costs of ordering, maintenance and goods deficit and also, warehouse management of each organization is obliged to control these costs. To avoid problems and possible damages caused by lack of inventory items, must be use techniques that eliminate the possibility of making any kind of problems in the production environment or as possible to reduce its occurrence [11]. ABC analysis is one of the most efficient techniques that are used in organizations.…”

The time-averaged L4L solution – a condition for long-run stability applying MRP theory

“…Net 3 production in such a case will be   [Bogataj and Grubbström, 2012], and we then obtain net production as…”

Net Present Value Evaluation of Energy Production and Consumption in Repeated Reverse Logistics

“…They extended multistage assembly systems with 3 additional subsystems: (2) distribution, (3) consumption and (4) recycling, as shown in Figure 1. This extension has been further elaborated in papers of Bogataj, Grubbström (2012 and the influence of aging on timing in such systems has been evaluated in while implementation in food industry is presented in Kovačić et al (2015). Figure 1 presents a closed system where produced elements are distributed to consumption activity cells, where they enter recycling at the end of their lifecycle.…”

“…Lead times can be unique for each individual pair of activity cells where transportation flow appears. The necessity for inclusion of transportation lead times in extended MRP theory is well presented by Bogataj, Grubbström (2012). Transportation costs influence the total NPV of the system and should be an integral part of the calculation.…”