JP2005107826A - Lot size formulation support method and stock simulation method - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a method capable of reducing generation of an excessive product to the utmost in consideration of diversion between kinds. <P>SOLUTION: In a lot size setting support method for a production process having the excessive product using a computer as stock, order information about all that are production targets within a prescribed period is read, a lot size is set on the basis thereof to generate order reception scheduled data, an order of the product is sequentially issued on the basis of the data, stock simulation of the generation of the excessive product, production of the product, and an allowance of the excessive product is performed to the order, it is decided whether a result thereof satisfies prescribed conditions or not, the lot size set at the beginning is decided when it is decided that it satisfies them, the generated excessive product is added to the stock to complete a series of data processing, the lot size set at the beginning is changed when it is decided that it does not satisfy them, and the series of data processing is repeated in this lot size formulation support method. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

  The present invention relates to a lot size formulation support method and an inventory simulation method capable of suppressing the generation of surplus products in a manufacturing process in which both order production and make-to-stock production are performed.

  When manufacturing a product, there is generally an appropriate manufacturing unit in a manufacturing facility, and surplus products may be generated due to the restrictions. In a manufacturing process including such a manufacturing facility, it is necessary to match the order lot size and the manufacturing unit of the manufacturing facility to minimize the generation of surplus products. For example, in a production facility with a production unit of 100, even if the required lot size is 10 or 90, the production amount is 100, and 90 or 10 surplus products are generated.

  Especially in the raw material industry, the lower limit of the processing amount may be set from the viewpoint of chemical engineering, and the order lot size may be less than the lower limit processing amount. In that case, it is desirable to reduce surplus products by processing various orders that can be combined together. In response to such demands from manufacturing processes, inventory simulation is sometimes performed as a means for examining strategies for optimizing the lot size, and various inventory simulation methods have been developed.

  For example, Patent Document 1 (Japanese Patent Laid-Open No. 4-180165) proposes a method of performing an inventory simulation by predicting a future order quantity from a past order record. This method considers the influence of the increase in the number of machines, the increase in production capacity, the shortening of the planning cycle, etc. on the inventory transition by taking into account the production constraints as a numerical value.

Patent Document 2 (Japanese Patent Laid-Open No. 8-241353) describes an inventory planning support apparatus, and an inventory simulation method is proposed therein. This method can prevent the excessive procurement of materials and parts and can indicate the procurement time and the procurement amount for keeping the product inventory amount appropriate.

Japanese Patent Laid-Open No. 4-180165 JP-A-8-241353

  However, the above prior art has the following problems.

  The technique described in Patent Document 1 is a method of performing inventory simulation in consideration of the lot size, and examination of optimization of the lot size is possible, but the surplus product generated during the manufacturing is not considered. As described above, there is a problem in that the estimation of the inventory quantity does not coincide with the actual transition because the production equipment has restrictions on the production quantity unit and the occurrence of surplus products may be unavoidable.

  The inventory simulation technique described in Patent Document 2 considers the lot size, and also considers surplus products generated during manufacturing. However, in this method, the relationship between the intermediate product and the final product is fixed, and the diversion between the intermediate products is not considered.

  In this prior art (Patent Document 2), the intermediate product amount and the final product amount are related only by the yield rate. For example, out of 100 intermediate products A manufactured, surplus products 50 are distributed to final products a, b, and c at a predetermined yield ratio. However, even if the intermediate product A can be diverted to the intermediate product B, the method for determining the diversion ratio is not shown for the final products d, e, and f obtained from B. Therefore, when this method is applied to a production process in which intermediate products can be diverted between varieties, the diversion between varieties is impossible, resulting in an increase in inventory.

The present invention has been made in view of such circumstances, and its object is to consider the generation of surplus products and the diversion between varieties, and to support lot size development that can minimize the generation of surplus products. A method and an inventory simulation method are provided.

The above problems are solved by the following invention. The invention is a lot size setting support method for a production process having a surplus product as a stock using a computer.
A step of reading all order information to be produced within a predetermined period, a step of setting a lot size based on the order information, and creating order plan data;
Sequentially issuing product orders based on the planned order data;
Performing an inventory simulation of surplus product allocation, product manufacture, and surplus product generation for the issued order;
Determining whether the result of the inventory simulation satisfies a predetermined condition;
When it is determined that the predetermined condition is satisfied, the initially set lot size is confirmed, the generated surplus product is added to the inventory, and a series of data processing is terminated,
When it is determined that the predetermined condition is not satisfied, the lot size formulation support method includes a step of changing the initially set lot size and repeating the above series of data processing.

The invention of inventory simulation
In a method for allocating surplus products using computers and a stock simulation method for generating surplus products,
Reading the issued order,
Loading inventory data for surplus products;
A step of determining whether to allocate the order data from the inventory data, and a step of allocating the surplus product to the order when it is determined that allocation is possible;
If it is determined that the product cannot be allocated, the product is calculated under the constraints of the equipment for the order,
It is an inventory simulation method comprising a step of changing a part of a manufactured product to a surplus product at a predetermined ratio and adding it to the inventory.

  In a lot size setting support method for a production process having surplus products as stock, it is necessary to set a product production lot in consideration of the presence of surplus products. In the present invention, lot sizes are first set for all orders to be produced for a predetermined period such as one day or one week. The lot size is set based on given conditions such as restrictions on manufacturing equipment or transportation means as well as the amount of products that can be manufactured in the same lot from the order information. In this way, the data in which the lot size is set for the order information is created and stored as order plan data.

  Next, an order as basic information for manufacturing or allocating products is sequentially issued from the created order receipt data. Perform inventory simulation for issued orders. The outline is to perform a simulation operation for the allocation of surplus products, the manufacture of products, and the generation of surplus products, and the inventory decreases / increases with the allocation / generation of surplus products.

  The inventory simulation will be described in detail later. When the result satisfies a predetermined condition, for example, when the production efficiency, the increase / decrease in the inventory amount, etc. are within a predetermined range (predetermined condition), the initially set lot size Confirm. At the same time, the surplus product generated as a result of the simulation is added to the inventory, and a series of data processing ends.

  When the simulation result does not satisfy the above range (predetermined condition), the initially set lot size is changed by a predetermined method. For example, it is increased or decreased by a certain amount or a certain ratio. In accordance with the lot size change, the contents of the planned order data (at least data related to the lot size) are updated. Thereafter, a series of data processing, that is, data processing after order issuance is repeated.

  In the invention of inventory simulation, a simulation is performed regarding the allocation or generation of surplus products, and a change in inventory quantity is obtained. First, a surplus product that can be allocated for an issued order is searched from the inventory. The conditions for enabling the allocation are given in advance based on past results including the possibility of diversion between varieties. As a result of the search, if a surplus product that can be allocated is found, the allocation is made for the order.

  On the other hand, if there is no surplus product that can be allocated as a result of the search, a product manufacturing instruction is issued for the order. Here, a simulation calculation for manufacturing is performed based on the issued manufacturing instruction, and at that time, a simulation calculation incorporating a constraint condition by a manufacturing facility such as production efficiency by the manufacturing condition is performed. In addition, a part of the manufactured product is degraded due to quality abnormality or the like at a predetermined ratio. The failed product is changed to a surplus product and added to the inventory.

In this way, it is possible to consider the generation of surplus products and the diversion between varieties, which are problems in actual production, and inventory simulation including them can be performed. As a result, the production in the manufacturing process can be faithfully reproduced, and data necessary for formulating a lot size in consideration of surplus products can be obtained.

The present invention performs data processing in consideration of the generation of surplus products and the diversion between varieties by performing data processing on the allocation of surplus products that can be allocated in inventory and the addition of surplus products generated during production to the inventory. In the process, inventory simulation that better simulates reality can be performed. Based on this, the lot size can be appropriately determined.

  Embodiments of the present invention will be described below. FIG. 1 is a diagram showing a system configuration image according to an embodiment of the present invention. The analyst activates a simulation program from a keyboard or a mouse (not shown). The simulation program is transferred from a storage device such as a hard disk to the main memory and executed by the central processing unit CPU. Further, data necessary for the simulation, for example, “order data”, “surplus product inventory data”, “order receiving planned data”, etc. are created before the simulation or at each stage of the simulation calculation step, and are stored in a storage device, for example, Stored in or read from the hard disk.

  FIG. 2 is a block diagram showing an outline of a production process to which the present invention is applied. This is a production process in which both order-made production according to orders from customers and prospective production based on inventory holding are performed. In this manufacturing facility, it is assumed that surplus products are generated due to restrictions on the unit of production or disqualification due to quality abnormalities. Further, a part of the surplus product is a production process that can be diverted to other varieties by satisfying a predetermined standard.

  FIG. 3 is a flowchart showing the procedure of the lot size formulation support method of the present invention. This flow consists of three processes: creation of planned order data, inventory simulation, and evaluation of simulation results. First, in the creation of order plan data (processing 1), the order size data is created by individually setting the lot size for all orders planned during the simulation target period. Here, the upper and lower limit values of the lot size are restricted by the production unit of the production facility.

  Next, in the inventory simulation (Process 2), based on the planned order receipt data, a simulation is performed for the allocation of inventory items or the production of products and the generation of surplus products for the orders (details will be described later with reference to FIG. 4). reference). Finally, in the evaluation of the simulation result (processing 3), it is determined whether the inventory simulation result satisfies a required condition.

  If the condition is satisfied, the series of processing ends. If the conditions are not satisfied, the lot size of the order planned data in process 1 is changed, the inventory simulation in process 2 is performed, and processes 1 and 2 are repeated until the required condition is satisfied. Hereinafter, the processes 1 to 3 will be described in detail.

[Process 1] Creation of planned order data Before performing simulation, create planned order data. At that time, if there is an order strategy formulated to meet various needs such as high-mix low-volume production, short delivery time, inventory reduction, etc., order-scheduled data is created based on the order strategy. On the other hand, if there is no change in the order receiving strategy and the past order record can be substituted, order schedule data is created based on the order record. The scheduled order data includes data items such as order entry date, scheduled production date, grade, grade, weight, and the like.

[Process 2] Inventory Simulation Next, the inventory simulation is executed as follows. FIG. 4 is a flowchart showing the processing procedure of the inventory simulation method.

[Processing 21] Initial data input First, in initial data input, initial data such as order plan data obtained in process 1 is input. The initial data includes the following data.

Provision conditions for surplus materials: Applicable conditions for grade, grade and weight Manufacturing equipment specifications:
・ Manufacturing unit restrictions (eg 250t / charge)
・ Manufacturing efficiency constraints (for example, 50 charges / day)
・ Restriction of surplus product ratio (for example, 50% or less)
Excess material specifications: Weight / grade Production abnormality rate: By material type / grade (abnormality rate obtained from the analysis results of past operation results).

[Process 22] Creation of order plan data This is the same as Process 1 described above. If no order plan data is created, such as when only inventory simulation is performed, order plan data is created here as in the above-described process 1.

    [Process 231] Order issuance Next, orders are issued in order of schedules based on the order plan data. Here, in accordance with the progress of the schedule, the order data whose order entry date corresponds to the current day is extracted from all the order input schedule data initially input, and the order is issued. In the order data, data items such as scheduled production date, material type, grade and weight are copied and set among the data items of the planned order data.

[Process 232] Allocation of surplus material In the surplus material allocation process, a surplus product that can be allocated is searched from an inventory for an issued order, and if found, the surplus product is allocated to the order. The determination as to whether or not to reserve the surplus material is performed using the surplus material allocation condition set as the initial data, that is, the matching condition of the material type, grade, and weight. These conforming conditions include conditions that allow diversion even if the grade and grade differ between the order and the surplus material.

  Table 1 shows an example of a divertable range when surplus products are allocated. The surplus materials that can be allocated here are surplus products (surplus materials) of grades A, B, and C when the ordered product is grade A, and surplus materials and grades of grades B and C when grade B In the case of C, it is a surplus material of grade C. Conversely, surplus products with grade A can be allocated only to ordered products with grade A, surplus products with grade B are grades A and B, grade C is grades A, B and C. Can be reserved for ordered products.

  It should be noted that which of the orders of grades A, B, and C allocates the remaining material of grade C depends on the dynamic state (simulation progress) in the inventory simulation at that time. Therefore, it is difficult to calculate with a fixed distribution ratio by a constant such as a yield rate as in the prior art. In the method of the present invention, since the distribution ratio is calculated based on the inventory simulation, the surplus materials can be appropriately distributed.

  Here, in the case of surplus material allocation, if no surplus product that can be allocated is found, an order product manufacturing instruction is issued. At that time, the generation of surplus products due to restrictions on the production unit or disqualification is also calculated at the same time.

[Process 233] Production Plan Creation In the production plan creation, order data for unfinished production that has reached the scheduled production date is extracted and a production plan is created. In the production plan, charges are used as units of production, and individual orders are applied to charges. Here, the production unit is a charge weight, and is input as initial data under the above-mentioned production unit restriction.

  To create a production plan, specifically, first, individual orders are sorted in the order from the earliest production date to give priority. Next, with the order with the first priority in the order as the charge reference material, orders of the same material type are extracted according to the priority order, and are accumulated and applied to the same charge. When the application of 1 charge is completed, the next charge reference material is selected according to the priority order, and is accumulated and applied in the same manner.

  If the weight of one or more orders allocated to one charge is less than the charge weight, the remainder is leftover. The ratio of the surplus material to the charge weight is called a surplus ratio, and if this becomes high, production efficiency is impaired. Therefore, if the surplus ratio constraint input as initial data is exceeded, the charge is removed from the production plan. Note that the number of charges per day, that is, the production volume, is limited by the above-described manufacturing efficiency constraint.

  In this way, corresponding product data is created for an order assigned to charge as a manufacturing plan. Orders that have not been applied to the charge as the production plan are carried forward as a surplus material allocation or processing target for the production plan on the next day.

[Process 234] Manufacturing Simulation In the manufacturing simulation, manufacturing is simulated based on a manufacturing plan. At that time, abnormal materials (products that do not satisfy the specifications of the production plan) are randomly generated so that the production abnormality occurrence rate input with the initial data is obtained. An order for a product that does not cause a manufacturing abnormality becomes a shipping material upon completion of manufacturing.

  A product that becomes an abnormal material in the manufacturing simulation becomes an unqualified surplus material or a scrap material. For example, the grade of surplus material is lowered by one rank, and an opportunity for provision of surplus material is awaited as inventory, and scrap material is disposed of. An order for a product that has become abnormal in production is not linked to the product, so the production date is reset and a return order is made.

  In this way, when the production simulation for one day is completed, the process returns to the above-described process 232 [allocation of surplus material] and reserves for the next day are performed. At that time, the unsatisfactory surplus material and the recovery order generated by the manufacturing simulation are added to the surplus material and the order, respectively, and are subject to the surplus material provision from the next day.

(Process 3) Judgment of Inventory Simulation Result Finally, it is determined whether the inventory simulation result satisfies a required condition (process 3 in FIG. 2). Here, as a required condition, a predetermined delivery time achievement rate or the like can be used. If the condition is not satisfied, the process returns to process 1 to change the lot size of the planned order data and repeats process 2 (stock simulation) and process 3 (judgment of simulation result) again. The lot size change amount may be, for example, a fixed amount or a fixed ratio.

  The simulation period was set to 3 months, and inventory simulation was performed for cases where small lot size orders were increased (small lot cases) and large orders were increased (large lot cases). Table 2 shows the results of the inventory simulation.

  In Table 2, it can be seen that the ratio of completed manufacturing is higher in the large lot case than in the small lot case. Looking at the ratio between the order issue amount and the return order generation amount, it can be seen that the ratio of the return order generation amount is smaller in the large lot case than in the small lot case, and the production efficiency is improved. Looking at the delivery rate achievement rate, it can be seen that the large lot case has a higher delivery rate and the production efficiency is improved than the small lot case.

5 and 6 are diagrams showing the transition of the inventory amount in the above simulation. From this, it can be seen that the large lot case has a lower level of inventory than the small lot case, which is improved from the viewpoint of inventory management.

According to the present invention, it is possible to quantitatively verify the effects or side effects on the transition of the inventory amount and the delivery rate achievement rate for various strategy proposals to meet the needs of inventory reduction and shortened delivery time.

The figure which shows the system configuration image of this invention. The block diagram which shows the outline | summary of the production process made into the object of application of this invention. The flowchart which shows the procedure of the lot size formulation support method. The flowchart which shows the process sequence of an inventory simulation method. The figure which shows transition of the stock quantity in simulation (small lot case). The figure which shows transition of the stock quantity in simulation (large lot case).

Claims (2)

In the lot size setting support method of the production process that has surplus products as stock in the computer,
A step of reading all order information to be produced within a predetermined period, a step of setting a lot size based on the order information, and creating order plan data;
Sequentially issuing product orders based on the planned order data;
Performing an inventory simulation of surplus product allocation, product manufacture, and surplus product generation for the issued order;
Determining whether the result of the inventory simulation satisfies a predetermined condition;
When it is determined that the predetermined condition is satisfied, the initially set lot size is confirmed, the generated surplus product is added to the inventory, and a series of data processing is terminated,
A lot size formulation support method comprising a step of repeating the series of data processing by changing the initially set lot size when it is determined that the predetermined condition is not satisfied. In a method for allocating surplus products using computers and a stock simulation method for generating surplus products,
Reading the issued order,
Loading inventory data for surplus products;
A step of determining whether to allocate the order data from the inventory data, and a step of allocating the surplus product to the order when it is determined that allocation is possible;
If it is determined that the product cannot be allocated, the product is calculated under the constraints of the equipment for the order,
A stock simulation method comprising a step of changing a part of a manufactured product to a surplus product at a predetermined ratio and adding the surplus product to the stock.

Images