Production planning method, production planning device, and production planning program

Abstract

To provide a production planning method capable of suppressing an increase in inventory quantity caused by an increase in lot size.SOLUTION: The production planning method includes: a basic information acquisition step of acquiring basic information including a work time of a production facility for target products and an internal setup time and an external setup time for each target product; a requirement acquisition step of acquiring a required number and a required production time of each target product; a temporary lot number determination step of determining a temporary lot number of each target product by using the required production time and the external setup time of each target product; a total lot number determination step of calculating an internal setup upper limit number by using the work time and the internal setup time, and comparing the internal setup upper limit number and the temporary lot number to determine a total lot number; a lot number determination step of determining a lot number of each target product with the total lot number as an upper limit; a production sequence determination step of determining a production sequence of the lot of each target product; and a lot size determination step of determining the lot size of each lot by using the production sequence and a production interval between the same target products.SELECTED DRAWING: Figure 2

Description

Technical Field

[0001] The present disclosure relates to a production plan formulation method, a production plan formulation apparatus, and a production plan formulation program.

Background Art

[0002] In the work-in-progress pattern creation method described in Patent Document 1, a step of tentatively determining the lot cycle and lot size of each of a plurality of types of target products, a step of tentatively determining the classification and number of seats for designated seats and free seats of each type of target product, and a step of determining the final lot cycle and lot size, the final classification of designated seats and free seats, and the number of seats for the final designated seats and free seats of each type of target product are provided.

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0004] However, in the method of Patent Document 1 above, since the lot size for each type of target product is determined on the premise that the lot cycles are equally spaced, the lot size may become larger than necessary. For this reason, there was a problem that the inventory level increased accordingly.

Means for Solving the Problems

[0005] The present disclosure can be realized in the following forms.

[0006] (1) According to one embodiment of the present disclosure, a production plan formulation method is provided. This production plan formulation method is a production plan formulation method for producing a plurality of types of target products in lots, and includes a basic information acquisition step of acquiring basic information including the operating time of the production equipment for the target products, the internal setup time and the external setup time for each type of the target products, a necessary condition acquisition step of acquiring the required quantity and the required production time for each type of the target products, a provisional lot number determination step of determining the provisional lot number for each type of the target products using the required production time and the external setup time for each type of the target products, a total lot number determination step of calculating the upper limit number of internal setups using the operating time and the internal setup time, comparing the upper limit number of internal setups with the provisional lot number, and determining the total lot number, a lot number determination step of determining the lot number for each type of the target products with the total lot number as the upper limit, a production order determination step of determining the production order of the lots for each type of the target products, and a lot size determination step of determining the lot size of each lot using the production order and the production interval of the same target product. According to the production plan formulation method of this embodiment, by determining the lot size of each target product using the production order and the production interval of the same target product, it is possible to suppress the lot size from becoming larger than necessary, and thus it is possible to suppress an increase in the inventory level due to an increase in the lot size. (2) In the production plan formulation method of the above embodiment, in the total lot number determination step, the smaller one of the upper limit number of internal setups and the provisional lot number may be determined as the total lot number. According to the production plan formulation method of this embodiment, by comparing the upper limit number of internal setups with the provisional lot number, the smaller one is determined as the total lot number. For this reason, the total lot number is not determined to be a number greater than the upper limit number of internal setups, so it is possible to suppress the equipment from being stopped for operation more than necessary due to internal setup. In addition, since a production plan can be formulated in anticipation of the internal setup ability, the production efficiency can be improved. (3) In the production plan formulation method of the above-described embodiment, in the lot number determination step, in the total lot number determination step, when the upper limit number of internal setups is less than the provisional lot number, among the provisional lot numbers of each type of target product, the lot number obtained by reducing the provisional lot number of the type of target product for which the lot production time becomes the shortest when the same lot number is reduced may be determined as the lot number of that type of target product, and the provisional lot numbers of the other types of target products may be determined as the lot numbers. According to the production plan formulation method of this embodiment, the lot number obtained by reducing the provisional lot number of the type of target product for which the lot production time becomes the shortest when the lot number is reduced is determined as the lot number of that type of target product. Therefore, it is possible to suppress spending a lot of time on the production of a single type of target product. Note that the present disclosure can also be realized in various forms other than the production plan formulation method. For example, it can be realized in forms such as a production plan formulation device, a production plan formulation program, and a non-transitory recording medium storing such a program.

Brief Description of the Drawings

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Mode for Carrying Out the Invention

[0008] A. First Embodiment: The production plan establishment method, the production plan establishment device 1, and the production plan establishment program of the first embodiment of the present disclosure will be described with reference to FIGS. 1 to 14. A1. Configuration of the Production Plan Establishment Device 1: FIG. 1 is a block diagram showing the schematic configuration of the production plan establishment device 1 in the first embodiment of the present disclosure. As shown in FIG. 1, the production plan establishment device 1 includes an input unit 2, a control unit 3, and a display unit 4.

[0009] The control unit 3 stores programs, data, etc. related to the method for formulating the above production plan, executes each process of formulating the production plan described later, and formulates a production plan. Specifically, the control unit 3 may be a functional unit realized by executing a predetermined computer program in a computer having a configuration in which a CPU, ROM, RAM, etc. are connected by a bus, or may have a configuration consisting of a one-chip LSI or the like. Further, the control unit 3 may be a dedicated product, but it is also possible to achieve it using a commercially available personal computer, workstation, or the like. Although the details of the functions of the control unit 3 will be described later, the main functions include a function of determining the lot number of each target product from the production capacity and the target period for formulation, and a function of determining the lot size of each target product lot according to the production order.

[0010] In the present application, "lot" refers to a set of the same type of target products (or products) as the unit of processing. Further, "lot size" is the number of the same type of target products processed together, that is, the number of each lot of the target products. Simplified, it is "the number produced at one time".

[0011] The input unit 2 enables those who want to create a production plan, etc. to input various data, etc. necessary for formulating the production plan. The input unit 2 may be a dedicated product, but it is also possible to achieve it using a commercially available keyboard, touch panel, or the like. The display unit 4 can display the data input by the input unit 2 and the production plan created by the control unit 3, etc. The display unit 4 may be a dedicated product, but it is also possible to achieve it using a commercially available monitor, liquid crystal display, or the like.

[0012] A2. Method for formulating production plan: Next, a production plan establishment method executed by the control unit 3 of the production plan establishment apparatus 1 will be described with reference to FIGS. 2 to 14. The production plan establishment apparatus 1 and the production plan establishment method are applied, for example, in factories or production activities that perform lot production in automobile manufacturers, parts manufacturers, and the like. The production plan establishment method according to the first embodiment produces a plurality of types of target products in lots, and determines the lot size of each target product lot in the operation of the equipment in one day.

[0013] FIG. 2 is a flowchart showing the processing procedure of the production plan establishment method. As shown in FIG. 2, the production plan establishment method includes a basic information acquisition step (S100), a necessary condition acquisition step (S200), a provisional lot number determination step (S300), a total lot number determination step (S400), a lot number determination step (S500), a production order determination step (S600), and a lot size determination step (S700), and these steps are executed in order.

[0014] Hereinafter, each step of the production plan establishment method will be described. In the basic information acquisition step (S100), basic information that is the basis for establishing a production plan is acquired. The "basic information" includes the operation time of the production equipment for the target product and the average setup time for the production target product. The "average setup time" is the working time when shifting the production target from the currently produced target product to another target product. The setup time is classified into an internal setup time and an external setup time. The "internal setup time" is the working time for realizing the shift from the currently produced target product to another type of target product by stopping the production equipment. The "external setup time" is the working time for realizing the shift from the currently produced target product to another type of target product without stopping the production equipment.

[0015] FIG. 3 is a diagram showing the operation time of the equipment in one day and the average setup time in the first embodiment. As shown in FIG. 3, in the first embodiment, the operation time in one day is "480 minutes". Also, the average internal setup time is "5 minutes", and the average external setup time is "25 minutes".

[0016] In the necessary condition acquisition process (S200), the required quantity and required production time of the target products are acquired. The "necessary conditions" include the "required quantity" and "required production time" of each target product. In the necessary condition acquisition process (S200), information for calculating how much time each target product must be produced, i.e., the required production time, is acquired. FIG. 4 is a diagram showing the required quantity and required production time for each target product. In the first embodiment, the target products produced by the facility are six types, namely target products A to F, and it is assumed that it takes 1 minute to produce one product for any of the target products. Note that it may be assumed that it takes an arbitrary time, not limited to 1 minute. Also, the production time per unit may vary for each type.

[0017] As shown in FIG. 4, the required quantity of target product A is 110, and the required production time is 110 minutes. The required quantity of target product B is 100, and the required production time is 100 minutes. The required quantity of target product C is 75, and the required production time is 75 minutes. The required quantity of target product D is 50, and the required production time is 50 minutes. The required quantity of target product E is 25, and the required production time is 25 minutes. The required quantity of target product F is 15, and the required production time is 15 minutes. Note that in actuality, the calculation is made taking into account various other unit factors.

[0018] In the provisional lot number determination process (S300), the provisional lot number of each target product is determined from the required production time of the target product and the external setup time. First, as a premise, the period for formulating the production plan is arbitrarily determined. In this embodiment, the period is set as 1 day. The required production time of each target product within the period is divided by the external setup time to determine the provisional lot number for each target product. FIG. 5 is a diagram showing the provisional lot number and provisional lot production time for each target product. In FIG. 5, the required production time and external setup time for each target product, which are used when calculating the provisional lot number and provisional lot production time, are also described together.

[0019] The provisional lot number is calculated by dividing the required production time for each target product within the period by the external setup time. Hereinafter, this "provisional lot number" will also be simply referred to as "provisional lot". The numbers after the decimal point are truncated, and those less than 1 are grouped as small quantities. In this embodiment, the small quantity is only the target product F, and one seat for small quantities is prepared. Therefore, the sum of the provisional lot numbers for all target products A to F (hereinafter referred to as "total provisional lot number") is 4 + 4 + 3 + 2 + 1 + 1 = 15. Also, in this process, the total production time required to produce all target products is obtained. The sum of the required production times for target products A to F is 110 + 100 + 75 + 50 + 25 + 15 = 375 minutes.

[0020] In the total lot number determination step (S400), the total lot number is determined. The total lot number is first calculated by obtaining the upper limit number of external setups from the operating time and the external setup time, and then determined by comparing the upper limit number of external setups with the provisional lot number. The "upper limit number of external setups" is the upper limit of the number of times to secure the time frame for producing various types of the target products. Since the external setup stops the operation, if the external setup is performed more than necessary, the production efficiency deteriorates. Therefore, an upper limit is set so that the time for the external setup does not exceed an arbitrary ratio with respect to the operating time. In this embodiment, it is assumed that 15% of the total operating time is allocated to the external setup, and the fraction is truncated. Since the total operating time is 480 minutes, the time allocated to the external setup is 480 (minutes) × 0.15 = 72 (minutes) That is, it is 72 minutes. Since the time required for one external setup is 5 minutes, 72 (minutes) ÷ 5 (minutes) = 14.4 ··· (times) Therefore, by truncating the fraction of the above calculated value, the upper limit number of external setups is 14 times.

[0021] Next, the upper limit number of external setups is compared with the total provisional lot number determined in the above provisional lot number determination step (S300), and the smaller number is set as the total lot number. In this embodiment, when comparing the total provisional lot number with the upper limit number of external setups, the upper limit number of external setups is smaller, so the total lot number is set to "14".

[0022] In the lot number determination process (S500), the lot number of each target product is determined with the total lot number as the upper limit. That is, the lot number of each target product is adjusted according to the total lot number. Since the total number of internal process steps is less than the total provisional lot number this time, it is necessary to reduce the lot number of one of the target products. Therefore, when reducing the lot number by one, compare how much the lot production time will increase, and reduce the lot number of the target product with the shortest lot production time when the lot number is reduced. FIG. 6 is a diagram showing the time that becomes shorter when the lot number is reduced for each target product.

[0023] In FIG. 6, the time described in the column of "when the lot number is reduced" is calculated by "required production time" ÷ "provisional lot number - 1". As shown in FIG. 6, in this example, the production time is the shortest when the lot number is reduced for target product B. Therefore, plan to reduce the lot number of target product B from 4 to 3. Since the required production quantity per day of the target product is determined, when reducing the lot number, which is the production frequency, the production time per time will be extended. As described above, by reducing the lot number of the target product with the shortest production time when the lot number is reduced, it is possible to prevent spending a lot of time on the production of a single type of target product even when the lot number is reduced and running out of stock of other types of target products. Note that the total number of internal process steps will not be more than the total provisional lot number.

[0024] In the production order determination process (S600), the production order of each lot of the target product is determined. Basically, arrange each lot so that the same target product lots are as evenly spaced as possible. Various leveling methods can be used for the arrangement method. Also, it is possible to incorporate production constraints and the like. According to the production interval at this time, the inventory quantity of each target product fluctuates each time. FIG. 7 is a diagram showing the production order of each lot of the determined target product. As shown in FIG. 7, in this embodiment, as the production order from the 1st to the 14th, assign A, B, C, D, A, E, B, C, A, F, D, B, A, C in order from the 1st.

[0025] In the lot size determination step (S700), the lot size of each lot is determined from the production order and the production interval of the same target product. Specifically, in the lot size determination step (S700), the expected production volume of each lot is calculated. In this embodiment, production is carried out in a so-called post-supplementary kanban system. The "post-supplementary kanban system" is a production method in which the target product before being processed in the processing step is stored in a container that accommodates a predetermined number (lot) of the target product for each target product, and a "kanban" with information such as the product number and the number of the target product is attached to the container. When all the target products in the container are processed, the "kanban" is collected, and an order is placed with the previous process based on the "kanban" at a predetermined time.

[0026] When calculating the expected production volume of each lot, the calculation is performed in order from the end of the production plan. The expected production volume needs to satisfy the number of products that will not be out of stock until the same target product is produced again. In order to calculate the number of products that will not be out of stock until the same target product is produced again, the time until the next production of the same target product is required, so it is necessary to calculate in advance the production time after the production order for which the calculation is performed. FIG. 8 is a diagram showing the production time of the target product that first appears in the production order. The "production time" is the number obtained by dividing the "required production time of the target product" by the "lot number of the target product". The lot number is the value determined in the previous lot number determination step (S500).

[0027] As shown in FIG. 8, as an example, for the target product C at the 14th production order, 75 minutes (required production time of target product C) ÷ 3 (lot number of target product C) results in 25 minutes. Similarly, starting from the end of the production order, the production time of each target product that is produced for the first time can be calculated in order. As shown in FIG. 8, in this embodiment, the production time of the target product A at the 13th production order is 27.5 minutes, the production time of the target product B at the 12th production order is 33.3 minutes, and the production time of the target product D at the 11th production order is 25 minutes. Similarly, the production time of the target product F at the 10th production order is 15 minutes, and the production time of the target product E at the 6th production order is 25 minutes.

[0028] Next, calculate the production time of the target product that appears for the second time and later from the end of the production order. For the target product A at the 9th position in the production order, since there is a possibility of producing the target product A at the 13th position in the production order, correct the expected production quantity of the lot according to the production interval. This correction is performed by comparing the following two types of first correction candidates and second correction candidates and applying the larger value. First correction candidate. Average external setup time (25 minutes in this embodiment) Second correction candidate. Production time required during the interval until the next production of the same target product

[0029] Regarding the calculation method of the "required production time" in the above second correction candidate, the target product A at the 9th position in the production order will be used as an example for explanation. First, calculate the average production time of all lots as follows. 375 minutes (total production time required to produce all target products) ÷ 14 (total number of lots) = 26.78 minutes Next, calculate the average production time from the target lot (9th in the production order) to the next target lot (13th in the production order) as follows. 26.78 (minutes) × 4 {[order of next production plan] - [order being calculated]} = 107.12 (minutes)

[0030] Then, calculate the ratio of the average production time to the total production time as follows. 107.12 (minutes) ÷ 375 (minutes) = 28.5 (%) Multiply the above ratio by the required production time of the target product to calculate the value of the second correction candidate as follows. 110 (minutes) × 0.285 = 31.35 (minutes) In this example, when comparing the values of the first correction candidate and the second correction candidate, the second correction candidate is larger. Therefore, "31.35 minutes" of the second correction candidate is applied as the required production time. Figure 9 is a diagram showing the production time of the target product in each production order according to the above procedure. For production orders 1 to 5, 7, and 8, the production time in all lots is calculated in the same manner as the above procedure.

[0031] The production quantity to be produced for the 9th target product A in the production order is the quantity that will not result in a shortage until the start of production of the 13th target product A in the production order. If the production quantity is large, the time required for that production will increase, and if the production quantity is small, the production time will be short. For example, if the production order of the last-occurring target product A is 12th, the interval for producing the target product A becomes shorter, so even if the production quantity of the 9th A is reduced, there will be no shortage. However, if the production order of the last-occurring target product A is 14th, the production interval becomes wider, so the production quantity of the 9th A must be increased to avoid shortages. In order to prevent such shortages, it is necessary to determine the expected production quantity for each lot, and thus the above calculations and corrections are being executed.

[0032] After calculating the necessary production time for all lots, a reduction to the production quantity for performing supplementary production is carried out. The calculated production time is only a reference production time, and actually, supplementary production is performed to prevent overproduction. At that time, in order to utilize "kanban", a value that serves as an upper limit is determined for the production of each lot, and an adjustment of the kanban quantity according to the upper limit of the inventory during production is required. FIG. 10 is a diagram showing the upper limit of the inventory for each lot. Using the unit cost of taking 1 minute to produce 1 product, the upper limit of the inventory is calculated from the production time of each lot. At this time, the fraction is rounded up. Here, the "upper limit of the inventory" corresponds to the "lot size" finally determined in the production planning of this embodiment.

[0033] FIG. 11 is a diagram showing the production plan formulated through the above-described various steps in detail. The "planned inventory quantity" in FIG. 11 corresponds to the "upper limit of the inventory" in FIG. 10, that is, the "lot size". The production plan shown in FIG. 11 is referred to as a "planned example case". After the lot size determination step (S700), it is also possible to output information incorporated in the formulation of the plan, such as a table summarizing the formulated plan as shown in FIG. 11, and display it on the display unit 4.

[0034] According to the production planning method, production planning apparatus 1, and production planning program of the above-described first embodiment, it is possible to formulate a production plan that suppresses an increase in the inventory quantity without increasing the lot size.

[0035] In the case of a production plan with a long production time, the inventory will increase accordingly. If the production time is shorter than the setup time, it is necessary to wait for the setup time. Therefore, in order to produce efficiently with as little inventory as possible and without waiting time, it is ideal to be able to carry out the production of each lot for the duration of the setup time. However, when attempting to execute such production, since the time for performing in-house setup and the production of subsequent processes continue, there is a risk of production delays and shortages if the in-house setup capacity is not sufficient. In this regard, in the first embodiment, in the dummy lot number determination step (S300) and the total lot number determination step (S400), the in-house setup capacity value and the external setup capacity value are compared, and the total lot number can be set so as not to exceed the in-house setup capacity value (14 times in the first embodiment), thereby suppressing production delays and shortages. Also, in the first embodiment, the in-house setup time is defined as 15% of the total operating time, but by changing this value, it is possible to formulate a plan assuming the in-house setup capacity.

[0036] FIG. 12 is a diagram showing a production plan example formulated by the production plan formulation method of the first comparative form. The production plan method of the first comparative form is different from the first embodiment above and plans the production of one day in two parts by the method described in the above Patent Document 1 (hereinafter referred to as the "comparative method"). The production plan shown in FIG. 12 is referred to as the "first comparative plan example". FIG. 13 is a diagram showing a production plan example formulated by the production plan formulation method of the second comparative form. The production plan method of the second comparative form plans the production of one day in four parts by the comparative method. The production plan shown in FIG. 13 is referred to as the "second comparative plan example".

[0037] Here, the differences between the method in the above-described first embodiment and the comparative method will be briefly explained. There are three main differences. In the comparative method, there are restrictions on the number of lots, the calculation method of the total number of seats is different, and there are free seats. In the comparative method, when formulating a plan, time is divided in advance in the form of A, B, C, D... (hereinafter, the divided time is called a "pattern"), and the production order within each pattern is determined, and production is carried out sequentially. Among them, in order not to increase the inventory, a constraint of "making the production intervals of the same target products equal" occurs, so only the value of the greatest common divisor of the number of patterns can be used to determine the number of lots.

[0038] Also, among the divisions made by the above patterns, in order to calculate the number of seats for each pattern, the total number of seats tends to be less than that of the method in the first embodiment. When the total number of seats decreases, the production volume per lot increases accordingly, resulting in an increase in inventory. Furthermore, when trying to incorporate a production plan within a pattern, if production is attempted in cycles of the greatest common divisor of the number of patterns due to the constraint on the number of lots, target products that cannot meet the external setup time will occur. For these parts with small-scale production, a framework is provided to manufacture them when there is a shortage, and this becomes the "free seat".

[0039] Figure 14 is a diagram showing the maximum inventory of each target product when the target products are produced based on the planning case according to the first embodiment, the first comparative planning case, and the second comparative planning case. As shown in Figure 14, in the planning case according to the first embodiment, the total inventory number, which is the sum of the maximum inventory numbers of each target product, is 166 pieces. Also, the total inventory number of the first comparative planning case is 208 pieces, and the total inventory number of the second comparative planning case is 181 pieces.

[0040] In the first comparative planning case, since the same target product is produced only up to twice a day in the plan, the production time for one time is extended, resulting in an increase in inventory. In the example of the second comparative planning case, due to the internal setup upper limit, the changeover time cannot be secured within each pattern, so the total number of lots decreases. As a result, an optimal lot cycle cannot be ensured, and the overall inventory increases.

[0041] In the second comparative example, after dividing one day into four parts, within each time period, the total number of seats is calculated on the premise of "allocating 15% of the total operating time to the inner setup time" in the same manner as in the first embodiment. That is, in the second comparative example, since the total operating time is divided into four parts, 120 (minutes) × 0.15 = 18 minutes is allocated to the inner setup. When this time is divided by the 5-minute inner setup time per instance, the result is 3.6. Therefore, rounding down the decimal part, the number of inner setups per cycle is 3 times, and since it is carried out for 4 cycles, a total of 12 inner setups are carried out. Compared with the first embodiment, the total number of inner setup times decreases.

[0042] Regarding the planned case example according to the first embodiment, for some target products such as target product A, although the inventory quantity increases compared to the lot size in the second comparative example, since the inventory quantity is appropriately corrected according to the lot, it varies to a lot size less than the maximum inventory quantity shown in Fig. 14, so the total inventory quantity can be further reduced.

[0043] B. Other Embodiments: (B1) In the production plan formulation method of the first embodiment, in the operation of the equipment in one day, the lot size of each target product lot was determined. However, the unit of operation does not have to be one day, and the numerical values such as the operation time and the average setup time are just examples and can be changed as appropriate. For example, a cycle of once every 4 days or once every 8 days within one month may be used.

[0044] (B2) In the production plan formulation method of the first embodiment, in the total lot number determination step (S400), the smaller of the inner setup upper limit number and the provisional lot number was compared and determined as the total lot number. However, the provisional lot number may be determined as the total lot number.

[0045] The present disclosure is not limited to the above-described embodiments, and can be implemented in various configurations without departing from the spirit thereof. For example, the technical features in each embodiment corresponding to the technical features in each form described in the summary of the invention can be appropriately replaced or combined in order to solve some or all of the above-described problems, or to achieve some or all of the above-described effects. Further, if the technical feature is not described as essential in this specification, it can be appropriately deleted.

Explanation of Signs

[0046] 1…Production plan formulation device, 2…Input unit, 3···Control unit, 4···Display unit

Claims

1. A method for formulating a production plan for producing multiple types of target products in lots, comprising: a basic information acquisition step of acquiring basic information including the operating time of the production equipment for the target products, the internal setup time and the external setup time for each type of the target products; a necessary condition acquisition step of acquiring the required quantity and the required production time for each type of the target products; a provisional lot number determination step of determining the provisional lot number for each type of the target products using the required production time and the external setup time for each type of the target products; a total lot number determination step of calculating the upper limit number of internal setups using the operating time and the internal setup time, comparing the upper limit number of internal setups with the provisional lot number, and determining the total lot number; a lot number determination step of determining the lot number for each type of the target products with the total lot number as the upper limit; a production order determination step of determining the production order of the lots for each type of the target products; a lot size determination step of determining the lot size of each lot using the production order and the production interval of the same target product; A method for formulating a production plan, characterized by comprising the above steps.

2. The method for formulating a production plan according to Claim 1, wherein in the total lot number determination step, the upper limit number of internal setups and the provisional lot number are compared, and the smaller one is determined as the total lot number.

3. The lot number determination step is as follows: in the total lot number determination step, when the upper limit number of internal setups is smaller than the provisional lot number, among the provisional lot numbers of each type of the target products, the lot number obtained by reducing the provisional lot number of the type of the target product for which the lot production time becomes the shortest when the same lot number is reduced is determined as the lot number of the type of the target product, and the provisional lot numbers of the other types of the target products are determined as the lot numbers. The method for formulating a production plan according to Claim 2.

4. A production plan formulation device for producing multiple types of target products in lots, comprising: a basic information acquisition step of acquiring basic information including the operating time of the production equipment for the target products, the internal setup time and the external setup time for each type of the target products; a necessary condition acquisition step of acquiring the required quantity and the required production time for each type of the target products; a provisional lot number determination step of determining the provisional lot number for each type of the target products using the required production time and the external setup time for each type of the target products; a total lot number determination step of calculating the upper limit number of internal setups using the operating time and the internal setup time, comparing the upper limit number of internal setups with the provisional lot number, and determining the total lot number; A lot number determination step of determining the lot numbers of each type of the target products with the total lot number as the upper limit, A production order determination step of determining the production order of the lots of each type of the target products, A lot size determination step of determining the lot size of each lot using the production order and the production interval of the same target product, and a control unit that creates a production plan for the target products, A production plan formulation device, characterized by comprising the above.

5. An input unit capable of inputting data used when creating the production plan, A display unit capable of displaying the data input by the input unit and the production plan created by the control unit, The production plan formulation device according to claim 4, further characterized by comprising the above.

6. A production plan formulation program for producing multiple types of target products in lot units, A function of acquiring basic information including the operating time of the production equipment for the target products, the internal setup time and the external setup time of each type of the target products, A function of acquiring the required quantity and the required production time of each type of the target products, A function of determining the provisional lot numbers of each type of the target products using the required production time and the external setup time of each type of the target products, A function of calculating the upper limit number of internal setups using the operating time and the internal setup time, and comparing the upper limit number of internal setups with the provisional lot numbers to determine the total lot number, A function of determining the lot numbers of each type of the target products with the total lot number as the upper limit, A function of determining the production order of the lots of each type of the target products, A function of determining the lot size of each lot using the production order and the production interval of the same target product, A production plan formulation program realized by a computer.

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