Data processing: generic control systems or specific application – Specific application – apparatus or process – Product assembly or manufacturing
Reexamination Certificate
1998-02-13
2001-08-07
Grant, William (Department: 2121)
Data processing: generic control systems or specific application
Specific application, apparatus or process
Product assembly or manufacturing
C700S107000, C700S106000
Reexamination Certificate
active
06272389
ABSTRACT:
BACKGROUND OF THE INVENTION
This invention relates to a novel capacity allocation method and system suitable for generating a production schedule.
INTRODUCTION TO THE INVENTION
Allocation methods for generating a production plan or schedule are known, and are preferably used in conjunction with conventional Material Requirement Planning (mrp) or Manufacturing Resource Planning (MRP) systems. Allocation methods may also be used with detailed finite scheduling systems, for generating aggregate schedules that are feasible with respect to material availability and aggregate capacity constraints. Reference on these points is made in U.S. Pat. No. 5,548,518, incorporated by reference herein.
SUMMARY OF THE INVENTION
We have discerned that traditional Manufacturing Resource Planning (MRP) systems can provide for only limited consideration of the manufacturing capacity. Subsumed Capacity Requirements Planning (CRP) modules, included in most commercial systems, use a simple offset-and-net calculation to evaluate a Master Production Schedule (MPS), to determine whether there is enough capacity at key work centers in order to produce the specified quantities of product in the specified time periods. This offset-and-net method, in turn, assumes fixed lead-times between the production of subassemblies and the production of high-level items that use these subassemblies. Now, in the event of insufficient capacity, a CRP system module can identify capacity shortages, but can not provide information as to how to address these shortages.
Our work addresses this situation, in the following way. In particular, and in sharp contrast to the intent and purview of the illustrative CRP system module approach, we note that even when CRP indicates capacity shortages in some periods, if there are also capacity surpluses for the same resources in earlier time periods, it may still be possible to determine a production plan that achieves the same end item production as specified by the MPS.
To this end, we disclose a novel method, which requires only slightly more computational effort than standard MRP logic. This novel method is most appropriate for use in an assembly environment, and can be incorporated into standard Manufacturing Resource Planning systems. An important aspect of this method is that, when it detects that there is not enough capacity to build the required quantity of product in the specified time period, it can determine how much of the product can be built in the specified time period, and then consider the possibility of building the rest of product in earlier periods. When the bill-of-materials (BOM) of the product has multiple levels, as is typical in an assembly environment where subassemblies are carried as stock, the novel method also considers building subassemblies earlier than specified by the BOM offsets, to allow for efficient use of available manufacturing capacity.
Accordingly, in a first aspect, we disclose a method suitable for producing a production plan that is feasible with respect to capacity availability, the method comprising:
(1) reading an end product demand and capacity availability information;
(2) selecting a specific demand derived from the end product demand and comprising an end product, a time period, and a quantity;
(3) determining whether the quantity can be produced in the time periods using the available capacity and surplus capacity from earlier periods; and
(4) recording the amount of capacity used in each time period to produce this quantity; thereby enabling realization of end product demand when an imbalance of demand and capacity exists.
In a second aspect, we disclose an allocation method for utilization within a computer for generating a feasible production plan, the method comprising the computer implemented steps of:
(1) reading an end product demand comprising a part number p, a quantity q, and a time period t, and reading capacity availability information for periods l through t;
(2) determining a planned quantity of production q′(t) less than or equal to the quantity q of the part number p that can be produced in the period t from subassemblies with available capacity;
(3) updating the capacity by subtracting the capacity required to produce this planned quantity q′;
(4) if possible, moving any remaining requirement q−q′ to successively earlier periods;
(5) repeating steps 2 and 3 until time t is exhausted thereby computing q′(t−1), q′(t−2), . . . ,q′(1);
(6) exploding the planned quantities of production q′(t), q′(t−1), . . . ,q′(1) of p through the bill of material of p to determine the requirements for each of the subassemblies p′ of p in each time period t′;
(7) repeating steps 1-5 for each part p′ used in p and each time period t′ until all requirements have been satisfied or no additional production is possible; and
(8) reporting whether the quantity q can be produced by period t.
In a third aspect, we disclose a system suitable for producing a production plan that is feasible with respect to capacity availability, the system comprising:
(1) means for reading an end product demand and capacity availability information;
(2) means for selecting a specific demand derived from the end product demand and comprising an end product, a time period, and a quantity;
(3) means for determining whether the quantity can be produced in the time periods using the available capacity and surplus capacity from earlier periods; and
(4) means for recording the amount of capacity used in each time period to produce this quantity; thereby enabling realization of end product demand when an imbalance of demand and capacity exists.
The novel method and system as defined can realize several significant advantages. The novel method and system can directly address and solve an important problem related to production planning. The method can be incorporated into a MRP system, taking advantage of existing database and reporting facilities. The method can also be combined with the method disclosed by Dietrich and Wittrock in U.S. Pat. No. 5,548,518, to produce production plans that are both material and capacity feasible, and which can take advantage of available capacity by building products and subassemblies earlier than required when insufficient capacity exists to build these parts in the required time frame.
REFERENCES:
patent: 5216593 (1993-06-01), Dietrich et al.
patent: 5440675 (1995-08-01), Matsunaga et al.
patent: 5548518 (1996-08-01), Dietrich et al.
patent: 5808914 (1998-09-01), Shin et al.
patent: 5963911 (1999-10-01), Walker et al.
patent: 5971585 (1999-10-01), Dangat et al.
Bahta Kidest
Grant William
International Business Machines - Corporation
Kaufman, Esq Stephen C.
McGinn & Gibb PLLC
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