Data processing: generic control systems or specific application – Specific application – apparatus or process – Product assembly or manufacturing
Reexamination Certificate
1999-12-03
2003-03-18
Von Buhr, Maria N. (Department: 2125)
Data processing: generic control systems or specific application
Specific application, apparatus or process
Product assembly or manufacturing
C700S106000
Reexamination Certificate
active
06535773
ABSTRACT:
TECHNICAL FIELD
The present invention relates to a material/quantity requirements arithmetic determination system for determining arithmetically a material/quantity requirements schedule in order to determine various types of parts and raw materials required for manufacturing an article in accordance with a given production schedule.
BACKGROUND ART
In conjunction with planning of a production schedule for a given article to be manufactured such as an electric motor, there is known a required material/quantity planning (also known as the material requirements planning, hereinafter referred to also as “MRP” in short) as one of methods for automatically determining arithmetically the types or species of parts required for manufacturing an article to be manufactured in accordance with a schedule, time points at which component parts of the article are required and the numbers thereof.
The MRP and the conventional MRP arithmetic scheme is disclosed, for example, in “ZUSETU MRP YOUGO 500 SEN (Selected 500 MRP terms with illustrations in English)” (published by Nikkan Kogyo Shinbun Co. in 1983) and others. In the following, the conventional MRP arithmetic scheme will be reviewed in brief.
For arithmetically determining an MRP, arrangement/preparation schedule is established on the basis of a planned production schedule of an article level (also known as the master production schedule, hereinafter referred to also as MPS in short) for purchasing or manufacturing required things (items) at required times(within delivery-appointed terms) by required amounts (required quantities) concerning parts, raw materials or the like. This arithmetic procedure requires generally three types of information mentioned below.
(1) MPS
In general, the term “master production schedule or MPS” means a production schedule and a standard production schedule of an item (article to be manufactured) which occupies a top level in a parts-exploded diagram.
(2) Parts Table
The term “parts table” means a list table based on two types of master data, i.e., data unique to items, being referred to as “items table”, and data indicating interrelations among items, e.g. between an article to be manufactured and component parts, between component parts and component parts, between component parts and raw materials, and so forth, being referred to as “parts arrangement table”.
(3) Inventory/Order Balance
The term “inventory/order balance” means inventory and number of items being in process at a current time point or an expected delivery-appointed term and an expected number of items already ordered and expected to be delivered or received in the future (order balance information).
On the basis of the information (1) to (3) mentioned above, the MRP arithmetic procedure is so designed as to execute five arithmetic operations mentioned below f or each of the items.
(1) Total Required Quantity Arithmetic
Required quantity data concerning a relevant item is fetched to thereby determine arithmetically a total required quantity thereof for a time period by taking into account the quantities required on a period-by-period basis. In this conjunction, the following description will be made on the presumption that the period mentioned above is set to one day and thus the schedule is planned on a day-by-day basis.
(2) Net Required Quantity Arithmetic
On the basis of the total required quantity determined arithmetically, the net required quantity demanded on a day-by-day basis is determined arithmetically by taking into account the inventory and the order balance.
(3) Lot Arrangement
On the basis of the net required quantity determined on the day-by-day basis, the number/quantity most appropriate for the arrangement or preparation is determined by taking into consideration a lot size preset for the relevant item.
(4) Lead Time Arithmetic
From the delivery-appointed term of the item of the number/quantity determined through the lot arrangement arithmetic, a lead time is subtracted to determine the relevant order date or outset date to thereby prepare the order.
(5) Expansion of Children-items
The order as prepared is expanded down to the items of the lowest rank by making reference to the parts table. More specifically, the demanded quantity is arithmetically determined for each of child-items on the basis of the child-items and the numbers thereof contained in the data concerning the structure of an article to be manufactured with the date immediately preceding to the order outset date being set as the demand-issued date, whereon the required quantities of the individual child-items are written in the required quantity data of each items.
In the following, the arithmetics (1) to (5) described above will be referred to as “part-based expansion arithmetics”.
Through the MRP arithmetic procedure, part-based expansion arithmetic is executed for all the items required for manufacturing the articles all preset in the MPS. It is however noted that the arithmetics for the individual items cannot be executed until the part-based expansion arithmetic for the relevant parent-item of the above-mentioned items has been completed for determining the total required quantity as demanded. For controlling such arithmetic execution sequence, low level codes are introduced in the conventional MRP arithmetic procedure.
At this juncture, description will be made of the low level codes in brief, As is illustrated in
FIG. 17
, on the basis of a parts-exploded diagram of a given article to be manufactured, it is possible to impart level codes to the parts, respectively, in dependence on which of the hierarchical levels or ranks each of the items belongs to in view of the hierarchical parts disposition. Because some of the items may have a plurality of level codes allocated, the level code of the hierarchically lowest level or rank is defined as the low level code. In this conjunction, with the low level or rank, it is contemplated to mean the level as viewed in the direction toward more basic item on the parts-exploded diagram, i.e., when the hierarchical level becomes lower, the corresponding part represents more basic item.
The low level codes of the individual items can be established by retrieving all the items contained in the parts table in precedence to the start of execution of the MRP arithmetic procedure. The low level codes are contained in the items data as the information specific or unique to the items.
By virtue of setting the low level codes in this manner, it can be ensured that so far as the part-based expansion arithmetics for the items ranking hierarchically higher than a given level inclusive thereof has been completed, the arithmetics for all the items belonging to the succeeding level can be executed,
Such being the circumstances, in the conventional MRP arithmetic procedure, the sequence of the part-based expansion arithmetics for the individual items is determined on a level-by-level basis by making use of the low level codes.
More specifically, processings are executed progressively through the procedure described below.
(1) Reading of MPS
A required quantity read out from the MPS is allocated to an item of the article level appearing in the MPS. Further, at that time, the relevant item name or identifier is entered in a queue of level 0.
(2) Start of Arithmetic Operation from the Queue of Level 0.
At the time point when the MPS reading operations have all been completed, one item identifier is extracted from the queue of level 0, whereon the part-based expansion arithmetic is performed for that item, upon completion of which the succeeding item identifier is extracted from the queue. In this conjunction, upon required quantity expansion in the course of the part-based expansion arithmetic operation, the child-item identifiers are entered in the queues of low level codes for the relevant child-items except for the case where the child-item identifiers have already been entered in the queue.
(3) Expansion on a Level-by-level Basis
When the queue of a certain level becomes empty or vacant, one item identifier is taken out from the qu
Sato Masahiro
Takata Masahito
Tsukishima Takahiro
Yokoyama Fumio
Yoshida Sachiko
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