JP7547293B2 - Intermediate inventory calculation device, program, and intermediate inventory calculation method - Google Patents

Description

The present invention relates to an intermediate inventory calculation device, a program, and an intermediate inventory calculation method.

Patent Document 1 below discloses a reference inventory quantity calculation device that includes an acquisition unit, an order probability density function generation unit, and a reference inventory quantity calculation unit. The order probability density function generation unit generates an order probability density function, which is a probability density function that represents the likelihood of an order quantity, based on actual order data acquired by the acquisition unit. The reference inventory quantity calculation unit calculates the reference inventory quantity based on the order probability density function generated by the order probability density function generation unit.

International Publication No. 2018/135526

However, the standard inventory quantity calculation device described in Patent Document 1 above cannot simultaneously determine the optimal intermediate inventory holding point and the optimal intermediate inventory holding amount at each holding point.

The present invention has been made in consideration of the above circumstances, and aims to provide an intermediate inventory holding amount calculation device, program, and intermediate inventory holding amount calculation method that can appropriately determine the optimal intermediate inventory holding point and the optimal intermediate inventory holding amount at each holding point.

An intermediate inventory holding amount calculation device according to one embodiment of the present invention is an intermediate inventory holding amount calculation device that calculates the intermediate inventory holding amount for a production line that manufactures products from raw materials through multiple manufacturing processes, and includes a setting unit that sets an intermediate inventory holding point at a branching point of the manufacturing process based on process design information that indicates the product manufacturing process, a creation unit that creates a mathematical model of an optimization problem with objective functions being the intermediate inventory holding cost, the amount of delay in delivery of the product to an order, and the intermediate inventory lead time, and a calculation unit that calculates the optimal value of the intermediate inventory holding amount at the holding point based on the mathematical model.

According to this aspect, the setting unit sets intermediate inventory holding points at branching points in the manufacturing process based on process design information indicating the manufacturing process of the product. Furthermore, the calculation unit calculates the optimal intermediate inventory holding amount at the holding point based on the mathematical model created by the creation unit. Therefore, it is possible to appropriately determine the optimal intermediate inventory holding point and the optimal intermediate inventory holding amount at each holding point.

In the above embodiment, the lead time includes the manufacturing lead time, which is the time required from the start of production of intermediate inventory to the completion of production of the product, and the waiting period from the completion of production of the intermediate inventory to the allocation of the intermediate inventory to an order for the product.

According to this aspect, it is possible to determine a more appropriate amount of intermediate inventory to be held based on the manufacturing lead time, which is the time required from the start of intermediate inventory production to the completion of product production, and the waiting period from the completion of intermediate inventory production to the allocation of the intermediate inventory to product orders.

In the above aspect, the mathematical model is a linear mathematical model defined as a weighted sum of the holding cost, the delivery delay, and the lead time.

According to this aspect, by defining the mathematical model as a linear mathematical model, it becomes possible to solve the optimization problem using linear programming.

In the above aspect, the optimization problem includes at least one of the following constraints: a first constraint expressing that intermediate inventory can only be held up to the upper limit; a second constraint expressing that no more intermediate inventory than is held can be allocated; a third constraint expressing that no intermediate inventory can be allocated unless an order is received; and a fourth constraint expressing that all orders must be allocated to one of the intermediate inventories.

According to this aspect, the optimization problem includes at least one of the first to fourth constraints, making it possible to determine a more appropriate amount of intermediate inventory to be held.

In the above aspect, the optimization problem includes all of the first constraint condition, the second constraint condition, the third constraint condition, and the fourth constraint condition.

According to this aspect, the optimization problem includes all of the first to fourth constraints, making it possible to determine the most appropriate amount of intermediate inventory to hold.

A program according to one aspect of the present invention is a program for causing an information processing device mounted on an intermediate inventory holding amount calculation device that calculates the amount of intermediate inventory held for a production line that manufactures products from raw materials through multiple manufacturing processes to function as: setting means for setting intermediate inventory holding points at each of multiple branching points in the manufacturing process based on process design information that indicates the product manufacturing process; creation means for creating a mathematical model of an optimization problem whose objective functions are the intermediate inventory holding cost, the amount of delay in delivery of the product to an order, and the intermediate inventory lead time; and calculation means for calculating the optimal value of the intermediate inventory holding amount at each holding point based on the mathematical model.

According to this aspect, the setting means sets intermediate inventory holding points at branching points in the manufacturing process based on process design information indicating the manufacturing process of the product. Furthermore, the calculation means calculates the optimal intermediate inventory holding amount at the holding point based on the mathematical model created by the creation means. Therefore, it is possible to appropriately determine the optimal intermediate inventory holding point and the optimal intermediate inventory holding amount at each holding point.

An intermediate inventory holding amount calculation method according to one embodiment of the present invention is a method for calculating the amount of intermediate inventory held for a production line that manufactures products from raw materials through multiple manufacturing processes, in which an information processing device sets intermediate inventory holding points at each of multiple branching points in the manufacturing process based on process design information indicating the product manufacturing process, creates a mathematical model of an optimization problem with objective functions being the intermediate inventory holding cost, the amount of delay in delivery of the product to an order, and the intermediate inventory lead time, and calculates the optimal value of the intermediate inventory holding amount at each holding point based on the mathematical model.

According to this aspect, the information processing device sets intermediate inventory holding points at branching points in the manufacturing process based on process design information that indicates the manufacturing process of the product. The information processing device also calculates the optimal intermediate inventory holding amount at the holding point based on the created mathematical model. Therefore, it is possible to appropriately determine the optimal intermediate inventory holding point and the optimal intermediate inventory holding amount at each holding point.

According to the present invention, it is possible to appropriately determine the optimal intermediate inventory holding points and the optimal intermediate inventory holding amount at each holding point.

1 is a diagram showing a simplified configuration of an intermediate inventory calculation device according to an embodiment of the present invention. FIG. 13 is a flowchart showing the flow of processing executed by an information processing unit. FIG. 13 is a diagram showing a simplified example of order prospect information. FIG. 2 is a diagram showing a simplified example of process design information. FIG. 13 is a diagram illustrating a simplified example of relationship information. FIG. 13 is a diagram illustrating a simplified example of manufacturing lead time information. FIG. 13 is a diagram illustrating a simplified example of possession upper limit value information. FIG. 13 is a diagram illustrating a simplified example of holding cost information. FIG. 1 is a simplified diagram illustrating an example of an optimal inventory holding pattern. FIG. 13 is a diagram showing the aggregation range of sigma. FIG. 2 is a diagram illustrating the definition of each variable.

Below, one embodiment of the present invention will be described with reference to the drawings. Note that in each drawing, the same components are designated by the same reference numerals, and detailed descriptions will be omitted as appropriate.

Figure 1 is a simplified diagram showing the configuration of an intermediate inventory holding calculation device 1 according to an embodiment of the present invention. The intermediate inventory holding calculation device 1 is an information processing device that calculates the amount of intermediate inventory held for a production line that manufactures products from raw materials through multiple manufacturing processes. The intermediate inventory holding calculation device 1 is configured by a computer system or the like, and includes an information processing unit 2 and an information storage unit 3. The information processing unit 2 is a CPU or the like, and the information storage unit 3 is an HDD or SSD or the like.

By the CPU executing the programs read from the information storage unit 3 to the ROM or RAM, the information processing unit 2 functions as an information input unit 11, an intermediate inventory holding point setting unit 12, a mathematical model creation unit 13, an optimal inventory holding pattern calculation unit 14, and a result output unit 15. The mathematical model creation unit 13 has an objective function creation unit 21, an intermediate inventory holding constraint creation unit 22, an intermediate inventory allocation upper limit constraint creation unit 23, an order allocation timing constraint creation unit 24, and an order allocation constraint creation unit 25. In other words, the above programs are programs for causing a computer mounted on the intermediate inventory holding amount calculation device 1 to function as these processing units. The processing contents in each processing unit will be described later.

In addition, process design information showing the manufacturing process from raw materials through intermediate materials to the production of each product is created in advance and stored in the information storage unit 3.

Figure 2 is a flowchart showing the flow of processing executed by the information processing unit 2.

First, in step SP01, the information input unit 11 acquires the created order forecast information 51 and inputs the acquired order forecast information 51 to the intermediate inventory holding point setting unit 12. In addition, the intermediate inventory holding point setting unit 12 acquires the process design information by reading the information from the information storage unit 3.

Figure 3 is a simplified diagram showing an example of order prospect information 51. Order prospect information 51 includes the order number, order product name (E1 to E5 in this example), order quantity, order date, and delivery date.

Next, in step SP02, the intermediate inventory holding point setting unit 12 sets the intermediate inventory holding point based on the process design information and order forecast information 51 acquired in step SP01.

Figure 4 is a simplified diagram showing an example of process design information for products E1 to E5. Products E1 and E2 are manufactured from raw material e0 through intermediate materials e1, e2, and e3. Product E3 is manufactured from raw material e0 through intermediate materials e1 and e2. Products E4 and E5 are manufactured from raw material e0 through intermediate materials e1 and e4. The intermediate inventory holding point setting unit 12 sets intermediate inventory holding points at branching points in the manufacturing process. Specifically, the intermediate inventory holding point setting unit 12 sets the holding point of intermediate material e1 at the branching point from "rough rolling" to "finishing rolling" and "annealing", sets the holding point of intermediate material e2 at the branching point from "refining" to "plating" and "finishing cut", sets the holding point of intermediate material e3 at the branching point from "plating" to "finishing cut" and "winding cut", and sets the holding point of intermediate material e4 at the branching point from "finishing rolling" to "refining 1" and "refining 2".

The intermediate inventory holding point setting unit 12 also creates relationship information 52 that indicates the corresponding allocation relationship between products E1 to E5 and raw material e0 or intermediate materials e1 to e4.

Figure 5 is a simplified diagram showing an example of relationship information 52. A flag of "1" is assigned to intermediate materials that can be allocated to product orders. In the example shown in Figure 5, orders for products E1 and E2 can be allocated to raw material e0 or intermediate materials e1, e2, and e3, orders for product E3 can be allocated to raw material e0 or intermediate materials e1 and e2, and orders for products E4 and E5 can be allocated to raw material e0 or intermediate materials e1 and e4. The intermediate inventory holding point setting unit 12 inputs the created relationship information 52 to the mathematical model creation unit 13.

The operator also creates manufacturing lead time information 53 indicating the manufacturing lead time, which is the period required from the start of intermediate material production to the completion of product production, holding upper limit value information 54 indicating the upper limit of intermediate material inventory (i.e. intermediate inventory), and holding cost information 55 indicating the holding cost of intermediate inventory, by referring to the process design information shown in FIG. 4 or the relationship information 52 shown in FIG. 5, and stores the created information in the information storage unit 3. Note that this information may be created by data processing by the information processing unit 2, rather than by input operations by the operator.

Referring to FIG. 2, next, in step SP03, the mathematical model creation unit 13 acquires the manufacturing lead time information 53, the holding upper limit value information 54, and the holding cost information 55 by reading them from the information storage unit 3.

Figure 6 is a simplified diagram showing an example of manufacturing lead time information 53. The manufacturing lead time is the period (number of days) required from the start of production of each intermediate material to the completion of production of the product. For example, it is shown that for product E1, it takes 16 days from raw material e0 to the completion of production of product E1, 11 days from the start of production of intermediate material e1 to the completion of production of product E1, 4 days from the start of production of intermediate material e2 to the completion of production of product E1, and 2 days from the start of production of intermediate material e3 to the completion of production of product E1. It can be seen that the further downstream the intermediate material is in the manufacturing process, the shorter the period required to complete production of the product.

Figure 7 is a simplified diagram showing an example of the holding limit information 54. In the example shown in Figure 7, the holding limit is set to 50 tons for each of intermediate materials e1 to e4. The holding limit for raw material e0 is set to infinity.

Figure 8 is a simplified diagram showing an example of holding cost information 55. The further downstream the intermediate material is in the manufacturing process, the higher the holding cost is set. In the example shown in Figure 8, the holding cost of intermediate material e1 is set to "12", the holding cost of intermediate material e2 is set to "14", the holding cost of intermediate material e3 is set to "18", and the holding cost of intermediate material e4 is set to "42". Additionally, the holding cost of raw material e0 is set to "0".

Referring to FIG. 2, in step SP04, the mathematical model creation unit 13 creates a mathematical model of the optimization problem shown in the following formula (E1) based on the input relationship information 52 and the acquired manufacturing lead time information 53, holding upper limit value information 54, and holding cost information 55.

This optimization problem is a linear programming problem in which the objective function and constraints are both described as linear functions. The objective function is the intermediate inventory lead time (first and third terms), the amount of delay in delivery of the product relative to an order (second term), and the intermediate inventory holding cost (fourth term). The mathematical model is a linear mathematical model defined as the weighted sum of these four items using weighting values _w1 to _w4 . The weighting values _w1 to _w4 are any value equal to or greater than "0."

In formula (E1), the first term indicates the manufacturing lead time, and the third term indicates the waiting time before production starts. In other words, the lead time of intermediate inventory, which is one of the objective functions, includes the manufacturing lead time (first term), which is the period required from the start of intermediate inventory production to the completion of product production, and the waiting period (third term) from the completion of intermediate inventory production to the allocation of that intermediate inventory to an order for a product.

In formula (E1), the following formula (C1) is a constraint condition created by the order allocation constraint creation unit 25. This constraint condition expresses that all orders must be allocated to one of the intermediate inventories.

In formula (E1), the following formula (C2) is used to calculate the allocation time.

In formula (E1), the following formula (C3) is used to calculate the lead time for each order.

In formula (E1), the following formula (C4) is used to calculate the production completion time for each order.

In formula (E1), the following formula (C5) is used to calculate the amount of delivery delay.

In formula (E1), the following formula (C6) is a constraint condition created by the order allocation timing constraint creation unit 24. This constraint condition expresses that if an order is not received, it cannot be allocated to intermediate inventory.

In formula (E1), the following formula (C7) is a constraint condition created by the intermediate inventory allocation upper limit constraint creation unit 23. This constraint condition expresses that no more than the intermediate inventory held can be allocated.

In formula (E1), the following formula (C8) is a constraint condition created by the intermediate inventory holding constraint creation unit 22. This constraint condition expresses that intermediate inventory can only be held up to the upper holding limit.

In formula (E1), formula (C9) below clearly indicates that x _jkt can only have the value "0" or "1".

Figure 10 shows the sigma aggregation range in formula (E1) and formulas (C1) to (C9). Unless otherwise specified in formulas (C1) to (C9), the sigma aggregation range will be as shown in Figure 10.

Figure 11 shows the definitions of each variable in formula (E1) and formulas (C1) to (C9).

Note that, although an example has been described above in which the optimization problem includes four constraints (C1), (C6), (C7), and (C8), it is sufficient to include at least one constraint.

Referring to FIG. 2, next, in step SP05, the optimal inventory holding pattern calculation unit 14 calculates the optimal value of the intermediate inventory holding amount at each holding point based on the mathematical model created by the mathematical model creation unit 13, thereby calculating the optimal inventory holding pattern.

Figure 9 is a simplified diagram showing an example of an optimal inventory holding pattern 56. The optimal inventory holding pattern 56 includes input information corresponding to the order forecast information 51 and calculation results. The calculation results include intermediate allocation inventory, allocation timing, allocation amount, shipping date, and whether or not there is a delay in delivery.

For example, order numbers 001 and 002 can be delivered on time even if they are manufactured from raw material e0, which has the lowest holding cost, so they are allocated to raw material e0. On the other hand, order number 005 cannot be delivered on time if it is manufactured from raw material e0, so it is delivered on time by allocating it to intermediate stock e1 even though it incurs high holding costs. Also, order number 011 is delayed in delivery by allocating it to intermediate stock e1. This is the result of reducing holding costs by allocating to intermediate stock e1 instead of intermediate stock e4, even if it causes delivery delays, because the holding cost of intermediate stock e4 is _high . If avoiding delivery delays is prioritized over reducing holding costs, the value of the weighting value _w2 of the second term related to the amount of delivery delay in formula (E1) can be increased, or the value of the weighting value w3 of the fourth term related to holding costs can be decreased, so that intermediate stock e4 can be allocated, and delivery delays can be prevented.

According to this embodiment, the intermediate inventory holding point setting unit 12 (setting unit) sets intermediate inventory holding points at branching points in the manufacturing process based on process design information indicating the product manufacturing process. In addition, the optimal inventory holding pattern calculation unit 14 (calculation unit) calculates the optimal intermediate inventory holding amount at the holding point based on the mathematical model created by the mathematical model creation unit 13 (creation unit). Therefore, it is possible to appropriately determine the optimal intermediate inventory holding point and the optimal intermediate inventory holding amount at each holding point.

Furthermore, according to this embodiment, in formula (E1), the lead time for intermediate inventory includes the manufacturing lead time (first term), which is the time required from the start of intermediate inventory production to the completion of product production, and the waiting period (third term), which is the time required from the completion of intermediate inventory production to the allocation of the intermediate inventory to an order for a product. This makes it possible to determine a more appropriate amount of intermediate inventory to hold, based on the manufacturing lead time and the waiting period.

In addition, according to this embodiment, by defining the mathematical model as a linear mathematical model, it becomes possible to solve the optimization problem using linear programming.

In addition, according to this embodiment, the optimization problem includes at least one of the first constraint condition (C8), the second constraint condition (C7), the third constraint condition (C6), and the fourth constraint condition (C1), making it possible to determine a more appropriate intermediate inventory holding amount.

In addition, according to this embodiment, the optimization problem includes all of the first to fourth constraints, making it possible to determine the most appropriate intermediate inventory holding amount.

Reference Signs List 1 Intermediate inventory holding amount calculation device 2 Information processing unit 12 Intermediate inventory holding point setting unit 13 Mathematical model creation unit 14 Optimal inventory holding pattern calculation unit 21 Objective function creation unit 22 Intermediate inventory holding constraint creation unit 23 Intermediate inventory allocation upper limit constraint creation unit 24 Order allocation timing constraint creation unit 25 Order allocation constraint creation unit

Claims (6)

An intermediate inventory calculation device that calculates intermediate inventory for a production line that manufactures products from raw materials through multiple manufacturing processes, comprising:
a setting unit that sets intermediate inventory holding points at branching points of a manufacturing process based on process design information indicating a manufacturing process of the product;
a creation unit that creates a mathematical model of an optimization problem with objective functions being the holding cost of intermediate inventory, the amount of delay in delivery of a product to an order, and the lead time of intermediate inventory;
A calculation unit that calculates an optimal value of the intermediate inventory at the holding point based on the mathematical model;
Equipped with
The optimization problem is
The first constraint expresses that intermediate inventory can only be held up to the upper limit.
The second constraint expresses that no more than the intermediate inventory held can be allocated.
The third constraint expresses that if an order is not received, the item cannot be allocated to intermediate inventory, and
The fourth constraint expresses that all orders must be backed up into some intermediate inventory.
An intermediate inventory calculation device including at least one of the above . The intermediate inventory holding calculation device according to claim 1, wherein the lead time includes a manufacturing lead time, which is the time required from the start of intermediate inventory production to the completion of product production, and a waiting period from the completion of intermediate inventory production to the allocation of the intermediate inventory to an order for a product. The intermediate inventory holding amount calculation device according to claim 1 or 2, wherein the mathematical model is a linear mathematical model defined as a weighted sum of the holding cost, the delivery delay, and the lead time. 2 . The intermediate inventory calculation device according to claim 1 , wherein the optimization problem includes all of the first constraint condition, the second constraint condition, the third constraint condition, and the fourth constraint condition. An information processing device to be installed in an intermediate inventory calculation device that calculates the amount of intermediate inventory held for a production line that manufactures products from raw materials through multiple manufacturing processes,
a setting means for setting intermediate inventory holding points at each of a plurality of branching points in a manufacturing process based on process design information indicating a manufacturing process of the product;
A creating means for creating a mathematical model of an optimization problem having objective functions of the holding cost of intermediate inventory, the amount of delay in delivery of a product to an order, and the lead time of intermediate inventory;
A calculation means for calculating an optimal value of the intermediate inventory amount at each holding point based on the mathematical model;
A program for causing the device to function as a
The optimization problem is
The first constraint expresses that intermediate inventory can only be held up to the upper limit.
The second constraint expresses that no more than the intermediate inventory held can be allocated.
The third constraint expresses that if an order is not received, the item cannot be allocated to intermediate inventory, and
The fourth constraint expresses that all orders must be backed up into some intermediate inventory.
A program including at least one of the following: A method for calculating intermediate inventory holdings for a production line that manufactures products from raw materials through multiple manufacturing processes, comprising the steps of:
An information processing device,
setting intermediate inventory holding points at each of a plurality of branching points in the manufacturing process based on process design information indicating the manufacturing process of the product;
A mathematical model is created for an optimization problem with objective functions being the holding cost of intermediate inventory, the amount of delay in delivery of products to orders, and the lead time of intermediate inventory.
Calculating an optimal value of the intermediate inventory holding amount at each holding point based on the mathematical model;
The optimization problem is
The first constraint expresses that intermediate inventory can only be held up to the upper limit.
The second constraint expresses that no more than the intermediate inventory held can be allocated.
The third constraint expresses that if an order is not received, the item cannot be allocated to intermediate inventory, and
The fourth constraint expresses that all orders must be backed up into some intermediate inventory.
The intermediate inventory holding amount calculation method includes at least one of the above .

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