Production route determination device and production route determination program

Abstract

To quickly determine a production route for a plurality of products that is an ideal solution for minimizing a load time, or a production route for the plurality of products close to the ideal solution, in a production line in which respective tasks of steps can be performed in parallel by a plurality of processing units, the production line allowing a plurality of kinds of products to be input.SOLUTION: An initial production route determination unit 18 determines an initial product that is a product to be initially supplied in a production line L1 and an initial production route that is a production route for the initial product. A load time calculation unit 20 calculates an increase in load time when an undetermined product is input to the production line L1 after a product whose production route has been determined, for all of product route combinations of the undetermined product and production routes that can be taken in the production line L1. Based on the increase in the load time for each product route combination, a production route determination unit 22 determines the next product that is an undetermined product to be next input to the production line L1 and the next production route that is a production route for the next product.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present invention relates to a production path determination device and a production path determination program. [Background technology]

[0002] Conventionally, technologies for creating production plans for products on production lines that produce products by performing work on products (work-in-progress) have been proposed. For example, Patent Document 1 discloses a production planning device that includes a graph conversion function that converts an input production schedule into a graph consisting of vertices and edges, a graph feature extraction unit that extracts graph features, calculates and evaluates allocation values, and selects the allocation with the highest allocation value, a schedule evaluation unit that outputs evaluation values ​​for the input production schedule and the selected allocation, a reinforcement learning unit that trains the creation of a schedule proposal using the allocation selection unit, evaluates the schedule proposal using the schedule evaluation unit, creates training data for the allocation selection unit that contributes to improving the evaluation value of the schedule proposal, and updates parameters of the allocation selection unit using a gradient descent method, and a schedule planning unit that creates and outputs a schedule using the allocation selection unit trained by the reinforcement learning unit for a list of product orders. Furthermore, Non-Patent Document 1 discloses the use of a two-stage genetic algorithm when creating a production plan for a flexible flow shop. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Japanese Patent Publication No. 2020-177565 [Non-patent literature]

[0004] [Non-Patent Document 1] Quadt, D, "Lot-Sizing and Scheduling for flexible flow lines", Springer(2004) Summary of the Invention [Problem to be solved by the invention]

[0005] Some production lines have multiple processes, and each process can be carried out in parallel by multiple processing units. Such production lines are called flexible flow shops. Each product is produced through multiple processes, and each product can take many production routes. The production route here refers to the route of processing units through which the product (work in progress) flows. For example, if there are three processes, and each process can be processed in parallel by five processing units, there are 125 possible production routes for each product.

[0006] In addition, multiple types of products may be input into a flexible flow shop and multiple types of products may be produced in the flexible flow shop. In such cases, the cycle time (time required for work, also called man-hours) of each processing unit that makes up the flexible flow shop may differ depending on the type of product.

[0007] In this way, in a flexible flow shop, each product can take many production routes, and when multiple types of products are input, the cycle time of each processing unit differs depending on the type of product. Therefore, a huge amount of calculation may be required to determine a production route for multiple types of products that is an ideal solution that minimizes the time required for all operations on the products input into the flexible flow shop (in other words, the time required to produce the products input into the flexible flow shop, which is referred to as the "load time" in this specification), or a production route for multiple types of products that is close to the ideal solution.

[0008] For example, the method of Patent Document 1 proposes a method using reinforcement learning, but it takes a considerable amount of time (e.g., several days) to create training data for reinforcement learning. Furthermore, reinforcement learning must be performed every time the production line configuration changes, and a sufficient amount of training data must be obtained each time. Furthermore, Non-Patent Document 1 proposes a two-stage genetic algorithm, but in cases where many production routes are possible, such as flexible flow shops, it can take an enormous amount of time to obtain an ideal solution using a genetic algorithm.

[0009] The object of the present invention is to enable a production line having multiple processes, in which the work of each process can be performed in parallel by multiple processing units, and into which multiple types of products are input, to quickly determine a production route for multiple products that is an ideal solution that minimizes load time, or a production route for multiple products that is close to the ideal solution. [Means for solving the problem]

[0010] The present invention is a production path determination device that determines production paths for a plurality of types of products that are produced through a plurality of processes in a production line that has a plurality of processes and in which work in each of the processes can be performed in parallel by a plurality of processing units, the production path determination device comprising: an initial production path determination unit that determines an initial production path, which is the production path for a leading product that is to be first input into the production line; a load time calculation unit that calculates, for all product path combinations that are combinations of the undetermined product and the production path, an increase in load time, which is the time required to produce a product that has been input into the production line when an undetermined product, whose production path is yet to be determined, is input into the production line after a product whose production path has been determined; and a production path determination unit that determines a next product, which is the undetermined product to be input into the production line next, and a next production path, which is the production path for the next product, based on the calculated increase in load time for each of the product path combinations.

[0011] Preferably, the initial production path determination unit determines a final process that is the last process of the plurality of processes. will be startedThe leading product is determined based on the time until the leading product of The final step but earliest Started The production route is determined as the initial production route.

[0012] Preferably, the initial production path determination unit determines the initial production paths of the plurality of leading products so that the initial production paths of the plurality of leading products do not interfere with each other.

[0013] Preferably, the multiple types of products include products having different attributes, and when the product that the processing unit has worked on and the product that the processing unit will work on next have different attributes, a work switching time is required between work on both products, and the load time calculation unit calculates the increase in the load time taking into account the work switching time.

[0014] Preferably, when there are a plurality of minimum combinations of the product routes that minimize the increase in the load time, the production route determination unit determines a final process that is the last process of the plurality of processes. of The method is characterized in that the next product and the next production route are determined from the minimum combinations, with emphasis on the increase in work time.

[0015] Preferably, when there are a plurality of minimum combinations which are the product route combinations that minimize the increase in the load time, the production route determination unit determines, among the minimum combinations, the undetermined product and the production route that constitute the minimum combination that includes the same production route as the initial production route, as the next product and the production route of the next product.

[0016] Preferably, the production line is a line that produces a plurality of each of the plurality of types of products, and a plurality of products of the same type are successively introduced into the production line, the initial production path determination unit determines the initial production path of a leading type that is to be introduced into the production line first, the load time calculation unit calculates the production path for all type-path combinations that are combinations of an undetermined type that is a type of product for which the production path is undetermined and the production paths, and the production path determination unit determines a next type that is the undetermined type that is to be introduced into the production line next, and a production path for the next type, based on the increase in load time for each of the calculated type-path combinations.

[0017] Preferably, in the production line, the production line is determined for each lot consisting of a plurality of products of the same type, the initial production path determination unit determines an initial production path which is a production path for a leading lot that is first input to the production line, and the load time calculation unit calculates an increase in load time which is the time required to produce a lot input to the production line when an undetermined lot, for which the production path has not been determined, is input to the production line after the lot for which the production path has been determined, by: Load time of the first product in the lot + (number of products in the lot - 1) x cycle time of the bottleneck in the production route and the production route determination unit determines the next lot, which is the undetermined lot to be put into the production line next, and the production route for the next lot, based on the increase in load time for each of the calculated lot route combinations.

[0018] Preferably, the production path determination unit determines the plurality of subsequent products having the attributes different from each other and the next production paths for the plurality of subsequent products based on the calculated increase in load time for each of the product path combinations.

[0019] Preferably, the load time calculation unit calculates an evaluation value for each of the product route combinations by the following formula (2), and the production route determination unit determines the plurality of subsequent products having the attributes different from one another and the next production routes for the plurality of subsequent products based on the calculated evaluation value for each of the product route combinations. Evaluation value = Load time × (1 + α × Number of setup changes) Equation (2) In equation (2), α is a weighting coefficient for the number of changeovers, which adjusts how much importance is attached to the number of changeovers.

[0020] Preferably, the initial production route determination unit determines the initial production route for the leading product, which is a plurality of products having different attributes.

[0021] Preferably, when candidate production routes that are candidates for the next production routes of the plurality of next products, which are determined based on the calculated increase in load time for each of the product route combinations, interfere with each other, the production route determination unit determines the candidate production route for the next product with the smaller increase in load time as the next production route for that next product, and reserves the determination of the next production route for the next product with the larger increase in load time.

[0022] The present invention also provides a production path determination program for determining production paths for a plurality of types of products to be produced through a plurality of processes in a production line having a plurality of processes in which work in each of the processes can be performed in parallel by a plurality of processing units, the production path determination program causing a computer to function as an initial production path determination unit that determines an initial production path, which is the production path for a leading product to be first input into the production line; a load time calculation unit that calculates, for all product path combinations that are combinations of the undetermined product and the production path, an increase in load time, which is the time required to produce a product input into the production line when an undetermined product, whose production path is yet to be determined, is input into the production line after a product whose production path has been determined; and a production path determination unit that determines, based on the calculated increase in load time for each of the product path combinations, a next product, which is the undetermined product to be input into the production line next, and a next production path, which is the production path for the next product. [Effects of the Invention]

[0023] According to the present invention, in a production line having a plurality of processes, in which the work of each process can be performed in parallel by a plurality of processing units and into which a plurality of types of products are input, it is possible to quickly determine a production route for a plurality of products that is an ideal solution that minimizes load time, or a production route for a plurality of products that is close to the ideal solution. [Brief explanation of the drawings]

[0024] [Figure 1] 1 is a schematic diagram illustrating the configuration of a production route determination device according to a first embodiment. [Figure 2] FIG. 1 is a diagram showing a production line according to a first embodiment. [Figure 3] FIG. 2 is a diagram showing possible production routes in a production line according to the first embodiment. [Figure 4] FIG. 1 is a diagram showing a plurality of subunits included in one processing unit. [Figure 5]FIG. 3 is a diagram showing a cycle time table showing an example of the cycle time of each subunit for each type of product in the production line according to the first embodiment. [Figure 6] FIG. 2 is a diagram showing an initial production route for a plurality of leading products in the first embodiment. [Figure 7] 1 is a Gantt chart for a plurality of lead products produced in an initial production route. [Figure 8] This is a Gantt chart when part number w001-L1 is sent to production route 1. [Figure 9] This is a Gantt chart when part number w001-L1 is sent to production route 26. [Figure 10] FIG. 10 is a diagram illustrating the effect of the first embodiment. [Figure 11] FIG. 10 is a diagram showing a production line according to a second embodiment. [Figure 12] FIG. 10 is a diagram showing possible production routes in a production line according to a second embodiment. [Figure 13] FIG. 10 is a diagram showing a cycle time table showing an example of the cycle time of each subunit for each type of product in the production line according to the second embodiment. [Figure 14] FIG. 11 is a diagram showing an initial production route for a plurality of leading products in the second embodiment. [Figure 15] FIG. 1 illustrates an example of a flow shop. [Figure 16] 16 is a Gantt chart for the flow shop shown in FIG. 15. [Figure 17] 10 is an evaluation value graph showing evaluation values ​​for a plurality of product route combinations. [Figure 18] FIG. 10 is a diagram showing product numbers that can be processed by each processing unit in Plan A. [Figure 19] FIG. 10 is a diagram showing product numbers that can be processed by each processing unit in Plan B. [Figure 20] FIG. 10 is a diagram showing product numbers that can be processed by each processing unit in Plan C. [Figure 21] FIG. 10 is a diagram illustrating the effects of the first and second embodiments. DETAILED DESCRIPTION OF THE INVENTION

[0025] First Embodiment FIG. 1 is a schematic diagram of the configuration of a production path determination device 10 according to the first embodiment. The production path determination device 10 according to the first embodiment is configured by a server computer. However, the production path determination device 10 may be any device as long as it can perform the functions described below. For example, the production path determination device 10 may be a personal computer or the like.

[0026] The input / output interface 12 is an interface for inputting various information to the production path determination device 10, or an interface for outputting various information from the production path determination device 10. Specifically, information required for the production path determination process by the processor 16, which will be described later, is input from the input / output interface 12, and information indicating the results of the production path determination process by the processor 16 is output from the input / output interface 12.

[0027] The input / output interface 12 may be, for example, a network interface configured from a network adapter, etc. The network interface enables the production path determination device 10 to communicate with other devices, receive various types of information from other devices, and transmit various types of information to other devices.

[0028] The input / output interface 12 may be an input interface configured with, for example, a keyboard, a mouse, a touch panel, etc. The input interface allows the user to input various information to the production path determination device 10.

[0029] Furthermore, the input / output interface 12 may be, for example, an output interface including a display such as a liquid crystal panel or a speaker, etc. The output interface enables the production path determination device 10 to output various information to a user or the like.

[0030] The memory 14 is configured to include, for example, a hard disk drive (HDD), a solid state drive (SSD), a read only memory (ROM), or a random access memory (RAM). The memory 14 may be provided separately from the processor 16 described below, or at least a portion of the memory 14 may be provided inside the processor 16. A production path determination program for operating each unit of the production path determination device 10 is stored in the memory 14.

[0031] The processor 16 includes at least one of a general-purpose processing device (e.g., a CPU (Central Processing Unit)) and a dedicated processing device (e.g., an ASIC (Application Specific Integrated Circuit), an FPGA (Field Programmable Gate Array), or a programmable logic device). The processor 16 may not be a single processing device, but may be configured by the cooperation of multiple processing devices located in physically separate locations. As shown in FIG. 1, the processor 16 performs the functions of an initial production path determination unit 18, a load time calculation unit 20, and a production path determination unit 22 according to a production path determination program stored in the memory 14.

[0032] As will be described in more detail below, processor 16 executes processing to determine production routes for multiple types of products produced through multiple processes in a production line that has multiple processes and in which work for each process can be processed in parallel by multiple processing units. In particular, the processor executes processing to determine a production route for multiple types of products that is an ideal solution that minimizes the load time, which is the time required to produce products input into the production line, or a production route for multiple types of products that is close to the ideal solution. In this specification, this processing is referred to as optimization processing for production routes in the production line. However, as mentioned above, optimization processing includes not only obtaining a production route as an ideal solution, but also processing to obtain a production route close to the ideal solution. In addition, in this specification, the production route for multiple types of products is referred to as a production plan.

[0033] Before describing the details of the initial production path determination unit 18, the load time calculation unit 20, and the production path determination unit 22, the production line L1 in the first embodiment will be described.

[0034] FIG. 2 is a diagram showing a production line L1 according to the first embodiment. The production line L1 is composed of three processes, processes 1 to 3, and a buffer B provided between each process. That is, on the production line L1, each product is produced by passing through the three processes, processes 1 to 3, in order. Each process has five processing units U. That is, processing units U capable of performing the work of process 1 include processing units #1 to #5, processing units U capable of performing the work of process 2 include processing units #6 to #10, and processing units U capable of performing the work of process 3 include processing units #11 to #15. Note that the work performed by each processing unit U is a work-in-progress item in the middle of production, and in this specification, the term "product" also includes work-in-progress items.

[0035] Products that have undergone process 1 in any of the processing units #1 to #5 are temporarily collected in buffer B1 located after process 1. Note that in this embodiment, there is no upper limit to the amount of products that can be stored in buffer B. Therefore, products that have completed process in processing units #1 to #5 can be moved from processing units #1 to #5 to buffer B1 without waiting, regardless of the amount of products in buffer B1. In other words, in this embodiment, production line L1 does not experience blocking, where a product cannot be passed to a subsequent process because the processing of a subsequent process is not complete even after the processing of a previous process is complete. The products are then transported from buffer B1 to any of the processing units #6 to #10, where they undergo process 2. The products that have undergone process 2 in any of the processing units #6 to #10 are temporarily collected in buffer B2 located after process 2. The products are then transported from buffer B2 to any of the processing units #11 to #15, where they undergo process 3. Products that have undergone work in process 3 in any of the processing units #11 to #15 are considered to be completed and are output from production line L1. The products (finished products) output from production line L1 are transported to, for example, a finished product warehouse.

[0036] In production line L1, there are 125 possible production paths for products, as shown in part in FIG. 3: 5 (the number of processing units U capable of performing the work of process 1) × 5 (the number of processing units U capable of performing the work of process 2) × 5 (the number of processing units U capable of performing the work of process 3). For example, production path 1 is processing unit #1 → processing unit #6 → processing unit #11, and production path 2 is processing unit #1 → processing unit #6 → processing unit #12. Thus, in this embodiment, a production path refers to the path of processing units U through which products flow. Note that a production line L1, like production line L1, which consists of multiple processes and in which the work of each process can be performed in parallel by multiple processing units, is also called a flexible flow shop. Information indicating the production paths available for production line L1, such as that shown in FIG. 3, is stored in advance in memory 14.

[0037] FIG. 4 is a diagram showing the configuration of one processing unit U. Each processing unit U included in the production line L1 is composed of one or more subunits S. The multiple subunits S are arranged in series in a line. The subunits S may be processing machines that perform processing in each step.

[0038] In this embodiment, the processing unit U capable of performing the work of step 1 is composed of three subunits S, the processing unit U capable of performing the work of step 2 is composed of four subunits S, and the processing unit U capable of performing the work of step 3 is composed of one subunit S. Of course, the number of subunits S constituting each processing unit U is not limited to these. In this specification, each subunit S is referred to as subunit Pxx. The number in the ones digit after P indicates the processing order in each processing unit U, and the number in the tens digit indicates the process number. For example, the first subunit S constituting the processing unit U capable of performing the work of step 1 is referred to as subunit P11, the second subunit S constituting the processing unit U capable of performing the work of step 1 is referred to as subunit P12, and the first subunit S constituting the processing unit U capable of performing the work of step 2 is referred to as subunit P21.

[0039] There are no buffers between the subunits S. Therefore, blocking can occur between the subunits S. For example, if subunit P12 has not finished working on the previous product when subunit P11 finishes working on it, subunit P11 cannot send the worked product to subunit P12, which is the subsequent process, and subunit P11 cannot start working on the next product.

[0040] In this embodiment, the subunit S is a processing machine that performs work, but as long as the cycle time (the time required for the subunit S to perform work) is stable, the subunit S may include a human (worker). Note that one subunit S can only perform work on one product, and cannot perform work on multiple products at the same time.

[0041] The cycle time, which is the time required for each subunit S to perform work on a product, is acquired in advance. Then, a cycle time table showing the cycle time of each subunit S is stored in advance in memory 14. Figure 5 shows an example of a cycle time table for each type of product.

[0042] Before explaining the cycle time of each subunit S, we will explain the products produced on the production line L1 in this embodiment. In this embodiment, 100 types of products are produced on the production line L1. The type of product is represented by the product's part number. In other words, products with the same part number are the same type of product, and products with different part numbers are different types of product. Specifically, on the production line L1, 100 product parts numbers w001 to 100 (i.e., 100 types) are produced.

[0043] In this embodiment, multiple types of products (multiple product numbers) are produced in multiple units on production line L1. Specifically, 12 lots of each product number are produced. That is, in this embodiment, production line L1 produces 12 lots of 100-unit product numbers each, for a total of 1,200 lots of products. A lot is a unit of production consisting of one or more products of the same type. In this embodiment, one lot consists of one product. Note that multiple lots of products of each product number do not necessarily have to be produced, and only one product may be produced. Furthermore, the number of products produced for each product number does not have to be the same.

[0044] Furthermore, among the multiple types of products produced on production line L1, some have different product attributes. In this embodiment, the multiple types of products produced on production line L1 have five product attributes, numbered 1 to 5. Specifically, as shown in Fig. 5, products with part numbers w001 to 020 have a product attribute of "1," products with part numbers w021 to 040 have a product attribute of "2," products with part numbers w041 to 060 have a product attribute of "3," products with part numbers w061 to 080 have a product attribute of "4," and products with part numbers w081 to 100 have a product attribute of "5." In other words, the larger the part number, the larger the value of the product attribute.

[0045] The cycle time of each subunit S for each part number (type) is acquired in advance, and a table such as that shown in FIG. 5 is created. For example, in the example of FIG. 5, the cycle time for part number w001 of subunit P11 included in each processing unit U (processing units #1 to #5) that performs the work of process 1 is 25 seconds, and the cycle time for part number w001 of subunit P12 included in the processing unit U that also performs the work of process 1 is 40 seconds. Incidentally, in the example of FIG. 5, the cycle time of each subunit S is shown in a fairly simplified manner, but the cycle times of each subunit S for each part number are generally different from one another. Note that in this embodiment, one lot is one product, so the cycle time for one lot of each subunit S is shown in the table shown in FIG. 5.

[0046] The time required to produce a product input into the production line L1, i.e., the load time, may include not only the processing time (cycle time) of each subunit S shown in FIG. 5 but also the waiting time (starving time) that occurs when a subunit S is ready to work (waiting for a product) but has not yet finished work in the previous process. In this embodiment, if the product attributes of the product worked on by a certain subunit S and the product that the subunit S will work on next have different product attributes, a task switching time is required between the work on the two products, and this task switching time may also be included in the load time. The task switching time is, for example, the time required for preparatory work, such as changing jigs, to work on a product with different product attributes (this preparatory work is called a "setup changeover"). The task switching time may be determined for each subunit S, or a uniform time may be determined for all subunits S. In this embodiment, the task switching time is set to a uniform 25 seconds for all subunits S.

[0047] Below, we will explain the details of the initial production path determination unit 18, the load time calculation unit 20, and the production path determination unit 22, as well as the algorithm for the optimization process of the production plan for the production line L1 by the processor 16. In this specification, the optimization process method described below is called the sequential allocation method. In the following embodiment, an example will be described in which a production path is determined for each lot. If each lot consists of one product, it can be said that a production path is determined for each product. However, as will be described later, it is also possible to assume that products of the same part number are produced together (multiple lots of the same part number are continuously input into the production line L1), and to determine a production path for each part number.

[0048] The initial production path determination unit 18 determines, from among a group of products scheduled to be produced on the production line L1, a leading product that is the first product to be put onto the production line L1, and an initial production path that is the production path for that leading product. In this embodiment, the initial production path determination unit 18 determines a leading lot that is the first lot to be put onto the production line L1.

[0049] Specifically, the initial production path determination unit 18 references the cycle time table (see FIG. 5) stored in memory 14 and determines the first product from the group of products based on the time it takes to reach the final process (process 3 in this embodiment), which is the last of the multiple processes included in the production line L1. The initial production path is determined to be the production path through which the first product reaches the final process earliest. This is because if the first product reaches the final process first, subsequent products introduced onto the production line L1 afterwards are less likely to experience blocking or starving in relation to the first product. Referring to FIG. 5, in this embodiment, the first lot with part number w002 is determined to be the first product. Hereinafter, the Yth lot with part number XXX will be referred to as wXXX-LY. For example, the first lot with part number w002 will be referred to as part number w002-L1.

[0050] The initial production path determination unit 18 can determine multiple lead products (and their initial production paths). In particular, the initial production path determination unit 18 determines multiple lead products and their initial production paths so that the initial production paths of the multiple lead products do not interfere with each other. The initial production paths not interfering with each other means that when multiple lead products are simultaneously input into the production line L1, no blocking, starving, or changeover occurs until the production of the multiple lead products is completed.

[0051] In this embodiment, the initial production path determination unit 18 determines five lots, namely, product number w002-L1, product number w022-L1, product number w042-L1, product number w062-L1, and product number w082-L1, as lead products (lead lots). Then, as shown in FIG. 6, the initial production path determination unit 18 determines the initial production path for item number w002-L1 to be production path 1 (processing unit #1 → processing unit #6 → processing unit #11), determines the initial production path for item number w022-L1 to be production path 32 (processing unit #2 → processing unit #7 → processing unit #12), determines the initial production path for item number w042-L1 to be production path 63 (processing unit #3 → processing unit #8 → processing unit #13), determines the initial production path for item number w062-L1 to be production path 94 (processing unit #4 → processing unit #9 → processing unit #14), and determines the initial production path for item number w082-L1 to be production path 125 (processing unit #5 → processing unit #10 → processing unit #15).

[0052] The initial production path determination unit 18 calculates the load time when the determined lead product is produced along the initial production path. FIG. 7 is a Gantt chart for multiple lead products produced along the initial production path. Note that the Gantt charts for part numbers w042-L1 and 062-L1 are omitted from FIG. 7. As described above, the initial production paths for the multiple lead products do not interfere with each other, so starving or changeovers do not occur in the production of the multiple lead products. Therefore, referring to the cycle time table in FIG. 5, the time required for the work in process 1 for each lead product is 90 seconds (20 seconds for the work by subunit P11, 30 seconds for the work by subunit P12, and 40 seconds for the work by subunit P13), and the time required for the work in process 2 for each lead product is 140 seconds (40 seconds for the work by subunit P21, 30 seconds for the work by subunit P22, 25 seconds for the work by subunit P23, and 45 seconds for the work by subunit P24). For simplicity, the time required for the work in process 1 and the time required for the work in process 2 for each lead product are set to be the same, but they may be different. Therefore, as shown in Figure 7, each lead product reaches process 3 230 seconds after being put in (90 seconds for the work in process 1 and 140 seconds for the work in process 2).

[0053] Of the multiple lead products, the product number w082-L1 takes the longest time to work in process 3, and the time required for the work in process 3 for product number w082-L1 is 40 seconds (40 seconds for the work by subunit P31). Therefore, production of product number w082-L1 is completed 270 seconds after input. In other words, the load time when multiple lead products are produced on the initial production route is 270 seconds.

[0054] The initial production path determination unit 18 determines production paths for five of the 1200 lots, leaving 1195 lots of products for which production paths have not yet been determined (referred to as "undetermined products" in this specification).

[0055] The load time calculation unit 20 calculates the increase in load time when an undetermined product is put into the production line L1 after a product whose production route has already been determined, for all combinations of the undetermined product and the production routes that can be taken on the production line L1 (these combinations are referred to as "product route combinations" in this specification).

[0056] FIG. 8 shows a Gantt chart for an example of a product route combination in which product number w001-L1 is sent to production route 1 (processing unit #1 → processing unit #6 → processing unit #11) after multiple lead products, that is, a Gantt chart for the combination of product number w001-L1, an undetermined product, and production route 1. When the undetermined product is introduced into production line L1, blocking, starving, or changeovers may occur in relation to the multiple lead products that have been introduced earlier. Therefore, the increase in load time for each product route combination also takes into account blocking time, starving time, and operation changeover time due to changeovers.

[0057] 8, for example, in subunit P21 of processing unit #6 in process 2, a starving time occurs after the processing of part number w002-L1 (leading product) is completed and before the processing of the next part number w001-L1 begins. Taking this starving time into consideration, the load time for the combination of part number w001-L1 and production route 1 is 325 seconds, and the increase in load time is 55 seconds (325 seconds - 270 seconds (load time of multiple leading products)).

[0058] FIG. 9 also shows, as an example of a product route combination, a Gantt chart when product number w001-L1 is sent to production route 26 (processing unit #2 → processing unit #6 → processing unit #11) after multiple leading products, that is, a Gantt chart for the combination of product number w001-L1, which is an undetermined product, and production route 26.

[0059] In the example of FIG. 9, in processing unit #2, work is performed on part number w022-L1, which is the lead product, followed by work on part number w001-L1. Here, the product attribute of part number w022-L1 is 2, and the product attribute of part number w001-L1 is 1. Therefore, in each of subunits P11, P12, and P13 included in processing unit #2, a work switching time is required before work on part number w001-L1 begins. In FIG. 9, the work switching time is indicated by black dots. Taking this work switching time into consideration, the load time for the combination of part number w001-L1 and production route 26 is 350 seconds, and the increase in load time is 80 seconds (350 seconds - 270 seconds (load times for multiple lead products)).

[0060] In this way, the load time calculation unit 20 calculates the increase in load time for all product route combinations (1195×125=149,375 combinations) of the 1195 lots other than the five leading products and the 125 production routes.

[0061] The production path determination unit 22 determines the next product, which is an undetermined product to be put into the production line L1 next, and the next production path, which is the production path for the next product, based on the increase in load time for each product path combination calculated by the load time calculation unit 20.

[0062] In principle, the production route determination unit 22 selects, from among multiple product route combinations, the product route combination that results in the smallest increase in load time (referred to in this specification as the "minimum combination"), and sets the undetermined product and production route included in the selected minimum combination as the next product and next production route.

[0063] There may be a case where there are multiple minimum combinations among multiple product route combinations. In such a case, the production route determination unit 22 determines the next product and the next production route in the following procedure.

[0064] The production path determination unit 22 selects one combination from the minimum combinations, focusing on the increase in work time of the process close to the final process of the production line L1 (process 3 in this embodiment), and sets the undetermined product and production path included in the selected combination as the next product and next production path.

[0065] Specifically, if there is one minimum combination among the minimum combinations that has the smallest increase in work time in process 3, which is the final process, the production path determination unit 22 determines the undetermined product and production path that constitute the minimum combination among the minimum combinations that has the smallest increase in work time in process 3 as the next product and next production path. Note that the work time in process 3 here is a time that takes into account not only the cycle time in process 3 but also the starving time and work changeover time in process 3.

[0066] If there are multiple minimum combinations with the smallest increase in work time in process 3, the production path determination unit 22 takes a first intersection set, which is the intersection of a set of minimum combinations with the smallest increase in work time in process 3 (multiple minimum combinations) and a set of minimum combinations with the smallest increase in work time in process 2, which is the process immediately before the final process (multiple minimum combinations).If the first intersection set contains one minimum combination, the production path determination unit 22 determines the undetermined product and production path that make up that minimum combination as the next product and next production path.

[0067] If there are multiple minimum combinations included in the first intersection set, the production path determination unit 22 selects a second intersection set, which is the intersection of the first intersection set and the set (multiple minimum combinations) for which the increase in work time in process 1, which is the process immediately preceding process 2, is the smallest. If there is one minimum combination included in the second intersection set, the production path determination unit 22 determines the undetermined product and production path that make up that minimum combination as the next product and next production path.

[0068] If there are multiple minimum combinations included in the second intersection, the production route determination unit 22 determines whether or not there is a minimum combination that includes the same production route as the initial production route determined by the initial production route determination unit 18 among the multiple minimum combinations included in the second intersection. If there is one minimum combination that includes the same production route as the initial production route among the multiple minimum combinations included in the second intersection, the production route determination unit 22 determines the undetermined product and production route that constitute this minimum combination as the next product and next production route. In this specification, the rule that selects the same production route as the initial production route is referred to as the "serial priority rule." Whether or not to apply the serial priority rule may be selectable by the user, etc.

[0069] If there is no minimum combination having the same production route as the initial production route among the multiple minimum combinations included in the second common set, or if there is multiple minimum combinations, the production route determination unit 22 determines the undetermined product and production route that constitute the minimum combination having the lot with the smallest product number (the lot with the smallest lot number if the product numbers are the same) among the multiple minimum combinations included in the second common set as the next product and next production route.

[0070] As described above, the production route determination unit 22 determines one next product and the next production route.

[0071] Once the production path determination unit 22 has determined the next product and the next production path, the load time calculation unit 20 calculates the increase in load time for all product path combinations of the remaining 1,194 lots and 125 production paths (1,194 x 125 = 149,250 combinations). Then, based on the load time calculated by the load time calculation unit 20, the production path determination unit 22 determines the product to be put onto production line L1 after the next product and its production path, using the same processing as described above.

[0072] The load time calculation unit 20 and the production path determination unit 22 repeat the above-mentioned process for all lots, thereby determining the production paths, i.e., the production plans, for all lots of 1200 units.

[0073] In the above-described embodiment, the production route was determined sequentially for each lot, but assuming that products of the same part number (same type) are produced together (multiple lots of the same part number are continuously input into production line L1), the production route may be determined for each part number.

[0074] Specifically, the initial production path determination unit 18 selects a leading part number as the leading type to be put into production line L1 first, and then determines an initial production path for that selection, the load time calculation unit 20 calculates the load time for all part number (type) route combinations which are combinations of undetermined part numbers as undetermined types, which are part numbers for which a production path is undetermined, and production paths, and the production path determination unit 22 determines the next part number (next type), which is the part number to be put into production line L1 next, and the production path for that next part number, based on the increase in load time for the calculated part number route combination.

[0075] By determining a production route for each product number, it is possible to reduce the amount of calculations performed by the load time calculation unit 20 and the production route determination unit 22. This reduces the time required to determine a production route for multiple types of products. On the other hand, when a production route is determined for each lot, the amount of calculations performed by the load time calculation unit 20 and the production route determination unit 22 increases, and the time required to determine a production route for multiple types of products increases, but the production route that is finally output for multiple types of products can be closer to the ideal solution.

[0076] Fig. 10 shows data on the production routes for multiple types of products determined by the above-described processing by the processor 16. It can also be said that Fig. 10 illustrates the effects of this embodiment. Fig. 10 shows the degree to which the load time reaches the ideal solution and the planning time, which is the time required to determine the production route, for each of the following cases: when the production route is determined for each lot and the serial priority rule is not applied; when the production route is determined for each lot and the serial priority rule is applied; when the production route is determined for each part number and the serial priority rule is not applied; and when the production route is determined for each part number and the serial priority rule is applied.

[0077] First, we will explain the ideal solution. An ideal production plan (which minimizes the load time) for production line L1 is one in which, in the final process, process 3, no setup changeover occurs (no task changeover time), no starving occurs (no starving time), and the work in the five processing units U included in process 3 is completed at the same time, completing the production of all products. The load time for this ideal production plan can be estimated from the cycle time table shown in Figure 5.

[0078] The total working time in process 3, the final process, can be calculated from the total cycle time for each lot in process 3 (i.e., subunit P31). In Figure 5, the total cycle time for each lot in process 3 is N seconds. Furthermore, assuming that the five processing units U included in process 3 finish production of all lots at the same time, the ideal production time in process 3 is N / 5 seconds, which is N seconds divided by 5 (the number of processing units included in process 3).

[0079] Meanwhile, the time it takes for each lot to reach process 3 can be calculated from the cycle times for processes 1 and 2. The time it takes for the first lot of each part number to reach process 3 is the sum of the cycle times for processes 1 and 2 for each part number. However, the sum of the cycle times for processes 1 and 2 for each part number differs for each part number. Therefore, in this embodiment, the average value of the sum of the cycle times for processes 1 and 2 for all part numbers is assumed to be the time it takes for the first lot of each part number to reach process 3. Here, the average value of the sum of the cycle times for processes 1 and 2 for all part numbers is assumed to be m seconds.

[0080] From the above two points, the load time of the ideal production plan is (N / 5) + m seconds, which is N / 5 seconds plus m seconds. Hereinafter, the load time of the ideal production plan will be referred to as the load time of the ideal solution. The degree of attainment of the ideal solution in Figure 10 is obtained by dividing the load time of the ideal solution by the load time of the production plan determined by processor 16.

[0081] As shown in Figure 10, when the production route is determined for each lot, the degree of reaching the ideal solution is higher compared to when the production route is determined for each part number. Furthermore, when the serial priority rule is applied, the degree of reaching the ideal solution is higher compared to when the serial priority rule is not applied. This is because applying the serial priority rule is thought to often reduce the possibility of waiting times and starving in the buffer. In particular, when the production route is determined for each lot and the serial priority rule is applied, the degree of reaching the ideal solution is 99.5%, meaning that a production plan that is quite close to the ideal solution can be created.

[0082] Furthermore, by determining the production route for each part number, the planning time can be significantly reduced compared to when the production route is determined for each lot. In particular, when the production route is determined for each part number and the serial priority rule is applied, a production plan with a 98% success rate in reaching the ideal solution can be created in 8 minutes. This is a significantly faster planning time than conventional methods. Even when the production route is determined for each lot, the planning time is approximately 104 minutes (even when the serial priority rule is applied), which is shorter than conventional methods.

[0083] Second Embodiment The configuration of the production path determination device 10 according to the second embodiment is the same as the configuration of the production path determination device 10 according to the first embodiment (see FIG. 1), and therefore a description thereof will be omitted. However, in the second embodiment, the processing contents of the processor 16 (initial production path determination unit 18, load time calculation unit 20, and production path determination unit 22) are different from those in the first embodiment.

[0084] 11 is a diagram showing a production line L2 according to the second embodiment. Like the production line L1 according to the first embodiment (see FIG. 2), the production line L2 is composed of three processes, processes 1 to 3, and a buffer B provided between each process. In the production line L2, each process has 10 processing units U. That is, the processing units U capable of performing the work of process 1 include processing units #1 to #10, the processing units U capable of performing the work of process 2 include processing units #11 to #20, and the processing units U capable of performing the work of process 3 include processing units #21 to #30.

[0085] Products that have undergone work in process 1 in any of the processing units #1 to #10 are temporarily collected in buffer B1 located after process 1. Note that in the second embodiment, there is also no upper limit to the amount of products that can be stored in buffer B. The products are then transported from buffer B1 to any of the processing units #11 to #20, where they undergo work in process 2. The products that have undergone work in process 2 in any of the processing units #11 to #20 are temporarily collected in buffer B2 located after process 2. The products are then transported from buffer B2 to any of the processing units #21 to #30, where they undergo work in process 3. The products that have undergone work in process 3 in any of the processing units #21 to #30 are completed and output from production line L2. The products (finished products) output from production line L2 are transported to, for example, a finished product warehouse.

[0086] In production line L2, there are 10 (the number of processing units U that can perform the work of process 1) × 10 (the number of processing units U that can perform the work of process 2) × 10 (the number of processing units U that can perform the work of process 3) = 1000 production routes for the product, as part of which is shown in Figure 12. Information indicating the production routes that can be taken in production line L2, such as that shown in Figure 12, is stored in advance in memory 14.

[0087] Each processing unit U included in production line L2 is composed of multiple subunits S arranged in series. In this embodiment, the processing unit U that can perform the work of process 1 is composed of seven subunits S, the processing unit U that can perform the work of process 2 is composed of nine subunits S, and the processing unit U that can perform the work of process 3 is composed of one subunit S.

[0088] It is assumed that 100 products with product numbers w001 to 100 are produced on production line L2. However, while in the first embodiment, one lot consists of one product, and 12 lots of products of each product number are produced, in the second embodiment, one lot consists of multiple products of the same type. Specifically, in the second embodiment, one lot consists of 12 products, and two lots of products of each product number are produced (i.e., 24 units each). In other words, 200 lots (100 product numbers x 2 lots) are produced on production line L2, and a total of 2,400 products (200 lots x 12 units) are produced. It is assumed that the multiple products included in one lot are produced together on the same production route.

[0089] A cycle time, which is the time required for each subunit S to perform work on a product, is acquired in advance. A cycle time table indicating the cycle time for each subunit S is then stored in memory 14 in advance. FIG. 13 shows an example of a cycle time table for each type of product on production line L2. The cycle time shown in the table in FIG. 13 indicates the time required for each processing unit to process one product. Similarly to the first embodiment, the multiple types of products produced on production line L2 have five product attributes, numbered 1 to 5. Specifically, as shown in FIG. 13, products with part numbers w001 to w020 have a product attribute of "1," products with part numbers w021 to w040 have a product attribute of "2," products with part numbers w041 to w060 have a product attribute of "3," products with part numbers w061 to w080 have a product attribute of "4," and products with part numbers w081 to w0100 have a product attribute of "5." In other words, the larger the part number, the larger the product attribute value.

[0090] In the second embodiment, a delivery time is set for each product part number. Figure 13 also shows the delivery time for each product part number.

[0091] The load time in the second embodiment may also include the processing time (cycle time) in each subunit S shown in Fig. 13 as well as the starving time. The load time may also include the task switching time required for setup changeover that occurs when the product attributes of the product worked on by a certain subunit S and the product that the subunit S will work on next are different. In this embodiment, the task switching time is set to a uniform 57 seconds for all subunits S.

[0092] Below, the initial production path determination unit 18, the load time calculation unit 20, and the production path determination unit 22 in the second embodiment will be described in detail, and the algorithm for the optimization process of the production plan for the production line L2 by the processor 16 will be described.

[0093] The initial production path determination unit 18 determines, from among a group of products scheduled to be produced on the production line L2, a leading product that is the product to be first introduced onto the production line L2, and an initial production path that is the production path for that leading product. In this embodiment, the initial production path determination unit 18 determines a leading lot that is the lot to be first introduced onto the production line L2.

[0094] The initial production path determination unit 18 can determine multiple lead lots (and their initial production paths). In particular, the initial production path determination unit 18 determines multiple lead lots and their initial production paths so that the initial production paths of the multiple lead lots do not interfere with each other. Furthermore, the initial production path determination unit 18 may determine multiple lots related to products having different product attributes as lead lots and determine initial production paths for the multiple lead lots.

[0095] In this embodiment, the initial production path determination unit 18 determines the following 10 lots as the leading lots: product number w001-L1 (product attribute "1"), product number w011-L1 (product attribute "1"), product number w021-L1 (product attribute "2"), product number w031-L1 (product attribute "2"), product number w041-L1 (product attribute "3"), product number w051-L1 (product attribute "3"), product number w061-L1 (product attribute "4"), product number w071-L1 (product attribute "4"), product number w081-L1 (product attribute "5"), and product number w091-L1 (product attribute "5"). Then, as shown in FIG. 14, the initial production path determination unit 18 determines the initial production path for item number w001-L1 to be production path 1 (processing unit #1 → processing unit #11 → processing unit #21), determines the initial production path for item number w011-L1 to be production path 112 (processing unit #2 → processing unit #12 → processing unit #22), determines the initial production path for item number w021-L1 to be production path 223 (processing unit #3 → processing unit #13 → processing unit #23), determines the initial production path for item number w031-L1 to be production path 334 (processing unit #4 → processing unit #14 → processing unit #24), and determines the initial production path for item number w041-L1 to be production path 445 (processing unit #5 → processing unit #15 → processing unit #26). The initial production route for product number w051-L1 is determined to be production route 556 (processing unit #6 → processing unit #16 → processing unit #26), the initial production route for product number w061-L1 is determined to be production route 667 (processing unit #7 → processing unit #17 → processing unit #27), the initial production route for product number w071-L1 is determined to be production route 778 (processing unit #8 → processing unit #18 → processing unit #28), the initial production route for product number w081-L1 is determined to be production route 889 (processing unit #9 → processing unit #19 → processing unit #29), and the initial production route for product number w091-L1 is determined to be production route 1000 (processing unit #10 → processing unit #20 → processing unit #30).

[0096] The initial production path determination unit 18 determines production paths for 10 of the 200 lots, leaving 190 lots for which production paths have not yet been determined (referred to as "undetermined lots" in this specification).

[0097] The initial production path determination unit 18 calculates the load time when the determined leading lot is produced along the initial production path.

[0098] The load time calculation unit 20 calculates the increase in load time when an undetermined lot is input into the production line L1 after a lot whose production route has already been determined, for multiple combinations of the undetermined lot and the production routes that can be taken on the production line L1 (these combinations are referred to as "lot route combinations" in this specification).

[0099] In this embodiment, one lot is made up of multiple products (12 in this embodiment), and when calculating the increase in load time for one lot route combination, a method can be considered in which, based on a Gantt chart or the like, the multiple products included in the lot are simulated to be sequentially input into the production route. However, this method requires that the calculation based on the Gantt chart be repeated for multiple products (12 in this embodiment), which increases the amount of calculation. Therefore, in this embodiment, the load time calculation unit 20 calculates the increase in load time for each lot route combination using the method described below.

[0100] As a simple example, consider a flow shop consisting of machines 1 to 3 (three processes) arranged in series, as shown in Figure 15. Here, assume that the cycle time of machine 1 is 3 seconds, the cycle time of machine 2 is 5 seconds, and the cycle time of machine 3 is 2 seconds. In other words, machine 2 has the longest cycle time of the three machines, and is therefore the bottleneck of the flow shop.

[0101] Figure 16 is a Gantt chart showing the sequential introduction of multiple products into the flow shop. As shown in Figure 16, the load time (t1) for the first product is 10 seconds. When the second product is then introduced, because Machine 2 is the bottleneck as described above, Machine 2 completes processing of the second product 5 seconds after it completes processing the first product (8 seconds later). Adding the cycle time of Machine 3 to this, the load time (t2) for the second product is 15 seconds. Similarly, the load time (t3) for the third product is 20 seconds, and the load time (t4) for the fourth product is 25 seconds.

[0102] In this way, the load time for the first product must be calculated using a Gantt chart, but the load time for the second and subsequent products can be calculated by adding the cycle time of the bottleneck machine.

[0103] From the above, in the second embodiment, the load time calculation unit 20 calculates the increase in load time for each lot route combination using the following formula (1). Load time of the first product in the lot + (number of products in the lot - 1) × cycle time of the bottleneck in the product path (1)

[0104] The calculation time for the second term in formula (1) is negligibly short. Therefore, by using formula (1), the amount of calculation and calculation time for the increase in load time for each lot path combination can be reduced. Note that when the initial production path determination unit 18 calculates the load time for the leading lot, the calculation may also be performed using formula (1).

[0105] In this embodiment, the load time calculation unit 20 further calculates an evaluation value based on the calculated load times for a plurality of lot route combinations. Specifically, the load time calculation unit 20 calculates the evaluation value using the following equation (2). Load time × (1 + α × number of setup changes) (2)

[0106] Here, the load time in formula (2) is the sum of the load time for the lot that has been determined so far and the increment of the load time for the lot route combination. Note that in formula (2), the load time may be replaced with the increment of the load time to calculate the evaluation value.

[0107] The number of setup changes is the number of setup changes that occur when an undetermined lot related to the lot route combination is input into the production route related to the lot route combination. The evaluation value calculated by formula (2) becomes larger when the number of setup changes occurs. In other words, it can be said that this is a value that places importance on the number of setup changes.

[0108] Furthermore, α in Equation (2) is a weighting coefficient for the number of setup changes, which adjusts how much importance is attached to the number of setup changes. In this embodiment, α is set to 0.1. Note that when α is set to 0, the term for the number of setup changes becomes 0, and an evaluation value is calculated that does not take the number of setup changes into consideration. On the other hand, when α is set to a maximum, the evaluation value significantly emphasizes the number of setup changes. In this case, even if there is a production route candidate for a certain lot that can shorten the overall load time even when a setup change occurs, if α is set to a maximum, the evaluation value will become significantly large as soon as a setup change occurs, making it impossible to select such a production route. Therefore, a moderate value for α is desirable, and in this example, 0.1 is an appropriate value, i.e., a value that minimizes the load time.

[0109] The smaller the evaluation value, the more suitable the lot route combination is for the next lot and its production route. Alternatively, the increase in load time may be used as the evaluation value.

[0110] When the load time calculation unit 20 calculates the evaluation values ​​for a plurality of lot route combinations, an evaluation value graph such as that shown in Fig. 17 is obtained. In the evaluation value graph shown in Fig. 17, the X axis indicates the undetermined lot, the Y axis indicates the production route number, and the Z axis indicates the evaluation value. Note that in Fig. 17, the direction of the Z axis is reversed, so that the smaller the evaluation value, the more positive the value is on the Z axis. It should be noted here that Fig. 17 is an evaluation value graph showing the evaluation values ​​of each lot route combination when the 10 leading lots shown in Fig. 14 are determined.

[0111] As will be described later, the production path determination unit 22 determines the next lot, which is the undecided lot to be inserted into the production line L2 next, and the production path for that next lot, based on the evaluation value graph. In other words, the undecided lots included in the evaluation value graph are candidates for the next lot. Here, the undecided lots included in the evaluation value graph (i.e., the undecided lots included in the lot-path combinations for which the load time calculation unit 20 has calculated the load times and evaluation values) may be all of the remaining undecided lots, or may be some of the remaining undecided lots. In this embodiment, the load time calculation unit 20 determines only undecided lots with product numbers that are close to due date as candidates for the next lot based on the due date of each product number (see FIG. 13 ), and calculates evaluation values ​​for only the undecided lots with product numbers that are close to due date. Therefore, the graph in FIG. 17 shows only the undecided lots with product numbers that are close to due date. As shown in FIG. 17 , the undecided lots are grouped by product number on the X-axis.

[0112] In the evaluation value graph of Fig. 17, the evaluation value drops in the areas indicated by A to E. This is because no changeovers occur in the areas indicated by A to E. This will be explained by focusing on area A.

[0113] As described above, FIG. 17 is an evaluation value graph showing the evaluation values ​​of each lot-route combination when the 10 lead lots shown in FIG. 14 are determined. Therefore, it is determined that the lead lot with product attribute "1" will be input into production routes No. "1" and "112." Here, the processing unit for process 1 of production route No. "1" is processing unit #1, and the processing unit for process 1 of production route No. "112" is processing unit #2. In other words, in processing units #1 and #2, work is performed on a product with product attribute "1." Here, the processing unit for process 1 of production routes No. "1 to 100" is processing unit #1, and the processing unit for process 1 of production routes No. "101 to 200" is processing unit #2. Therefore, if the production route of an undetermined lot whose product attribute is not "1" is set to one of production routes No. "1 to 200," a changeover will be necessary at least in the processing unit for process 1 (processing unit #1 or #2). Therefore, in FIG. 17, the evaluation value of the lot route combination of the production route "1 to 200" and the undetermined lot with a product attribute other than "1" (product attribute "2 to 5") is large.

[0114] On the other hand, in processing the first lot, in processing units #3 and #4, work is performed on products with product attribute "2" in process 1 of production route Nos. "223" and "334", in processing units #5 and #6, work is performed on products with product attribute "3" in process 1 of production route Nos. "445" and "556", in processing units #7 and #8, work is performed on products with product attribute "4" in process 1 of production route Nos. "667" and "778", and in processing units #9 and #10, work is performed on products with product attribute "5" in process 1 of production route Nos. "889" and "1000". Here, the processing unit for process 1 of production route Nos. "201 to 300" is processing unit #3, the processing unit for process 1 of production route Nos. "301 to 400" is processing unit #4, the processing unit for process 1 of production route Nos. "401 to 500" is processing unit #5, the processing unit for process 1 of production route Nos. "501 to 600" is processing unit #6, the processing unit for process 1 of production route Nos. "601 to 700" is processing unit #7, the processing unit for process 1 of production route Nos. "701 to 800" is processing unit #8, the processing unit for process 1 of production route Nos. "801 to 900" is processing unit #9, and the processing unit for process 1 of production route Nos. "901 to 1000" is processing unit #10. Therefore, if the production route of an undetermined lot with product attribute "1" is set to one of the production routes "201 to 1000," a changeover will be required at least in the processing units of process 1 (processing units #3 to 10). Therefore, in FIG. 17, the evaluation value of the lot route combination of the production route "201 to 1000" and the undetermined lot with product attribute "1" is large.

[0115] As described above, among the lot route combinations of the production route "1-200" and the undetermined lot of the product attribute "1", there may be some that do not require a changeover, and the lot route combinations that do not require a changeover may have a very small evaluation value, as in area A. Note that among the lot route combinations of the production route "1-200" and the undetermined lot of the product attribute "1", there may be some that require a changeover (in process 2 or 3), and the evaluation value for such lot route combinations will be high.

[0116] Using the same principle as in area A, area B of low evaluation values ​​may exist among the lot route combinations of production route "201-400" and undecided lots with product attribute "2", area C of low evaluation values ​​may exist among the lot route combinations of production route "401-600" and undecided lots with product attribute "3", area D of low evaluation values ​​may exist among the lot route combinations of production route "601-800" and undecided lots with product attribute "4", and area E of low evaluation values ​​may exist among the lot route combinations of production route "801-1000" and undecided lots with product attribute "5".

[0117] The production route determination unit 22 determines the next lot and the production route of the next lot based on the evaluation value graph as shown in Fig. 17. Specifically, based on the evaluation value graph, a lot route combination having a small (preferably the smallest) evaluation value is determined, an undetermined lot related to the determined lot route combination is set as the next lot, and a production route related to the determined lot route combination is set as the production route of the next lot.

[0118] In particular, in this embodiment, the production route determination unit 22 determines multiple next products (next lots in this embodiment) having different product attributes and the next production routes for the multiple next products based on the evaluation value graph. For example, if the evaluation value graph is as shown in FIG. 17, the lot route combination with the smallest evaluation value is determined within area A, the undetermined lot related to this lot route combination is set as the next lot with product attribute "1", and the production route related to this lot route combination is set as the production route for this next lot. Similarly, the lot route combination with the smallest evaluation value is determined from each of areas B to E, and each next lot with product attributes "2 to 5" and the production route for each next lot are determined. That is, in this embodiment, five next lots and their production routes are determined from one evaluation value graph.

[0119] Once the production path determination unit 22 has determined the next lot and its production path, the load time calculation unit 20 calculates the above evaluation values ​​for the remaining 185 undecided lots (or undecided lots among them with the nearest due date) and 1,000 product path combinations, and obtains an evaluation value graph again. Then, based on the obtained evaluation value graph, the production path determination unit 22 determines multiple subsequent lots to be put into production line L2 just after the next lot, and their production paths, by processing similar to that described above.

[0120] The load time calculation unit 20 and the production path determination unit 22 repeat the above process for all lots, thereby determining the production paths, i.e., the production plans, for all lots of 200 units.

[0121] 17, the reason why there is an evaluation value region for the undetermined lot of each product attribute is that the multiple lots for which the production routes were determined immediately before (here, these are the multiple leading lots determined by the initial production route determination unit 18) include lots related to product attributes "1 to 5." If all leading lots were lots related to product attribute "1," only the evaluation value for the lot route combination including the undetermined lot of product attribute "1" would be a low evaluation value, and in the evaluation value graph, low evaluation value regions A to E would be aligned along the Y axis.

[0122] In such a case, a lot route combination including an undetermined lot related to product attributes "2 to 5" will inevitably require a changeover, and the evaluation value is not necessarily low, but the production route determination unit 22 determines a lot route combination including an undetermined lot for each product attribute. For example, from among the lot route combinations including an undetermined lot of product attribute "2", the lot route combination with the lowest evaluation value is identified, and the undetermined lot included in this lot route combination is set as the next lot, and the production route included in this lot route combination is set as the production route for the next lot. The same applies to product attributes "3 to 5" (and of course, also to product attribute "1").

[0123] As a result, in the evaluation value graph next calculated by the load time calculation unit 20, the lots for which the production routes were previously determined include lots related to product attributes "1 to 5," and therefore the evaluation graph will have low evaluation value regions for each product attribute, as shown in FIG. 17.

[0124] Therefore, for example, even if it is not possible to include lots related to product attributes "1 to 5" in the multiple leading lots due to some circumstances, by including lots related to product attributes "1 to 5" in the multiple next lots at an early stage as possible, it will be possible thereafter to preferably identify lot route combinations from the low evaluation value region for each product attribute.

[0125] There may be cases where the production routes for multiple next lots determined by the production route determination unit 22 interfere with each other. Therefore, the production route determination unit 22 may determine candidate production routes for multiple next lots and multiple production routes for the multiple next lots through the above-mentioned processing, and then check whether the candidate production routes for the multiple next lots interfere with each other.

[0126] If multiple production route candidates interfere with each other, the production route determination unit 22 determines the production route candidate with the smaller evaluation value among the multiple interfering production route candidates as the production route for the next lot related to that production route candidate.On the other hand, the determination of the production route for the next lot related to the other production route candidates (i.e., the production route candidate with the larger evaluation value) among the multiple interfering production route candidates is put on hold, and the next lot is returned to the undetermined lot.

[0127] In the first embodiment, each time the next product and the next production route are determined, a combination of one next product and the next production route is determined based on the increase in load time for all product route combinations. However, in the second embodiment, multiple combinations of next lot and production routes can be determined each time the next lot and the production route for that next lot are determined. This reduces the amount of calculation and calculation time required to determine a production plan. Note that, even in the second embodiment, the production route determination unit 22 can employ an embodiment in which a combination of one next lot and production route is determined each time the next lot and the production route for that next lot are determined.

[0128] The effects of the second embodiment will be described below. In an actual production line L2, it is rare that all processing units U can perform work on all product part numbers, and in many cases the processing units U that can perform work on each part number are limited. For this reason, three plans A to C were considered here, which limit the processing units U that can be allocated to each part number. The processing units U that can perform work on each product part number in each plan are shown in Figures 18 to 20.

[0129] FIG. 18 is a diagram showing the product numbers that each processing unit can process in Plan A. In Plan A, all processing units U are capable of working on all product part numbers in processes 1 to 3. FIG. 19 is a diagram showing the product numbers that each processing unit can process in Plan B. In Plan B, it is assumed that work on each product part number in processes 1 to 3 can be performed by only five processing units U each. FIG. 20 is a diagram showing the product numbers that each processing unit can process in Plan C. In Plan C, it is assumed that all processing units U are capable of working on all product part numbers in processes 1 and 2, and that work on each product part number in process 3 can be performed by only five processing units U each. The number of production paths for Plans A, B, and C are 1,000, 125, and 500, respectively.

[0130] A production plan is created by trialing a sequential allocation method incorporating speed-up measures for plans A to C, and the calculation time for the production plan is compared with that of the first embodiment. FIG. 21 is a diagram showing the calculation time for the production plan according to the first and second embodiments. FIG. 21 shows the calculation time required to determine the production plan for each of plans A to C for each combination of the number of products in one lot, the method for calculating the load time increase, and the method for determining the next lot and its production route. Note that in the method for determining the next lot and its production route, "determining multiple production routes for the next lot" means that the load time calculation unit 20 determines multiple production routes for the next lot each time it calculates the load time (or evaluation value) for each lot-route combination, and "determining one production route for the next lot" means that the load time calculation unit 20 determines one production route for the next lot each time it calculates the load time (or evaluation value) for each lot-route combination.

[0131] The combination of "1" for the number of products in one lot, "calculate for each product" as the calculation method for the increase in load time, and "determine a production route for one next lot" as the method for determining the next lot and its production route is the combination according to the first embodiment. With this combination, it took 28,214 seconds to determine the production route for Plan A, 6,798 seconds to determine the production route for Plan B, and 16,193 seconds to determine the production route for Plan C.

[0132] The combination of "12" products in one lot, "using Equation (1)" as the calculation method for the load time increase, and "determining one production route for the next lot" as the method for determining the next lot and its production route is a combination according to one aspect of the second embodiment. In this combination, the load time calculation unit 20 determines the next lot and its production route one lot at a time each time it calculates the evaluation value for each lot-route combination. Since one lot consists of 12 products, production routes are determined for each of the 12 products. This combination also differs from the first embodiment in the calculation method for the load time increase. In this combination, the calculation time required to determine the production route for Plan A is 2,082 seconds, the calculation time required to determine the production route for Plan B is 557 seconds, and the calculation time required to determine the production route for Plan C is 1,232 seconds, which is shorter than the first embodiment.

[0133] The combination of "12" products in one lot, "using formula (1)" as the calculation method for the load time increase, and "determining multiple production routes for the next lot" as the method for determining the next lot and its production route is a combination related to the best mode of the second embodiment. With this combination, each time the load time calculation unit 20 calculates the evaluation value for each lot-route combination, a production route is determined for each of five lots, i.e., 60 products. With this combination, the calculation time until the production route is determined for Plan A is 669 seconds, the calculation time until the production route is determined for Plan B is 168 seconds, and the calculation time until the production route is determined for Plan C is 360 seconds, which is significantly shorter than in the first embodiment.

[0134] Although the embodiment of the present invention has been described above, the present invention is not limited to the above embodiment, and various modifications are possible without departing from the spirit of the present invention. [Explanation of symbols]

[0135] 10 production path determination device, 12 input / output interface, 14 memory, 16 processor, 18 initial production path determination unit, 20 load time calculation unit, 22 production path determination unit.

Claims

1. 1. A production path determination device for determining production paths for a plurality of types of products produced through a plurality of processes in a production line having a plurality of processes in which work in each of the processes can be performed in parallel by a plurality of processing units, comprising: an initial production path determination unit that determines an initial production path, which is a production path for a leading product that is first input into the production line; a load time calculation unit that calculates an increase in load time, which is the time required to produce a product introduced into the production line when the undetermined product, whose production route is undetermined, is introduced into the production line after the product, whose production route has been determined, for all product route combinations, which are combinations of the undetermined product and the production route; a production path determination unit that determines a next product, which is the undetermined product to be next introduced into the production line, and a next production path, which is a production path for the next product, based on the calculated increase in load time for each of the product path combinations; A production path determination device comprising:

2. the initial production path determination unit determines the leading product based on a time until a final process that is the last of the plurality of processes is started, and determines, as the initial production path, a production path in which the final process of the leading product is started earliest.

2. The production route determination device according to claim 1.

3. the initial production path determination unit determines the initial production paths of the plurality of leading products so that the initial production paths of the plurality of leading products do not interfere with each other.

3. The production route determination device according to claim 1 or 2.

4. the plurality of types of products include products having different attributes, When the product that the processing unit has worked on and the product that the processing unit will work on next have different attributes, a work changeover time is required between the work on both products; The load time calculation unit calculates an increase in the load time in consideration of the task switching time.

2. The production route determination device according to claim 1.

5. when there are a plurality of minimum combinations which are the product route combinations that minimize the increase in the load time, the production route determination unit determines the next product and the next production route from among the minimum combinations, with emphasis on the increase in the operation time of a final process that is the last process among the plurality of processes; 2. The production route determination device according to claim 1.

6. When there are a plurality of minimum combinations which are the product route combinations that minimize the increase in the load time, the production route determination unit determines, among the minimum combinations, the undetermined product and the production route that constitute the minimum combination that includes the same production route as the initial production route, as the next product and the production route of the next product.

2. The production route determination device according to claim 1.

7. the production line is a line that produces a plurality of each of the plurality of types of products, A plurality of products of the same type are continuously fed into the production line, the initial production path determination unit determines the initial production path of a leading type to be initially input into the production line; the load time calculation unit calculates the load time for all type-route combinations that are combinations of the undetermined type, which is a type of product for which the production route is undetermined, and the production route; the production path determination unit determines a next type, which is the undetermined type to be next introduced into the production line, and a production path for the next type, based on the calculated increase in load time for each of the type-path combinations.

2. The production route determination device according to claim 1.

8. In the production line, the production line is determined for each lot consisting of a plurality of products of the same type, the initial production path determination unit determines an initial production path, which is a production path for a leading lot that is initially input into the production line; The load time calculation unit calculates an increase in load time, which is the time required to produce a lot input into the production line when the undetermined lot, whose production path has not been determined, is input into the production line after the lot, whose production path has been determined, by: Load time of the first product in the lot + (number of products in the lot - 1) x cycle time of the bottleneck in the production route a calculation is performed for a plurality of lot route combinations, which are a plurality of combinations of the undetermined lot and the production route, the production path determination unit determines a next lot, which is the undetermined lot to be subsequently input into the production line, and a production path for the next lot, based on the calculated increase in load time for each of the lot path combinations.

2. The production route determination device according to claim 1.

9. the production path determination unit determines the plurality of subsequent products having the attributes different from each other and the subsequent production paths of the plurality of subsequent products based on the calculated increase in load time for each of the product path combinations.

5. The production route determination device according to claim 4.

10. The load time calculation unit calculates an evaluation value for each of the product route combinations using the following formula (2): the production route determination unit determines the plurality of subsequent products having the attributes different from each other and the subsequent production routes of the plurality of subsequent products based on the calculated evaluation value for each of the product route combinations.

10. The production path determination device according to claim 9. Evaluation value = Load time × (1 + α × Number of setup changes) ... Formula (2) In equation (2), α is a weighting coefficient for the number of changeovers, which adjusts how much importance is attached to the number of changeovers.

11. the initial production path determination unit determines the initial production path of the leading product, which is a plurality of the products having the attributes different from each other; 10. The production path determination device according to claim 9.

12. When candidate production routes that are candidates for the next production routes of the plurality of next products, which are determined based on the calculated increase in load time for each of the product route combinations, interfere with each other, the production route determination unit determines the candidate production route for the next product with a smaller increase in load time as the next production route for the next product, and reserves the determination of the next production route for the next product with a larger increase in load time.

10. The production path determination device according to claim 9.

13. 1. A production path determination program for determining production paths for a plurality of types of products produced through a plurality of processes in a production line having a plurality of processes in which work in each of the processes can be performed in parallel by a plurality of processing units, the program comprising: Computer, an initial production path determination unit that determines an initial production path, which is a production path for a leading product that is first input into the production line; a load time calculation unit that calculates an increase in load time, which is the time required to produce a product introduced into the production line when the undetermined product, whose production route is undetermined, is introduced into the production line after the product, whose production route has been determined, for all product route combinations, which are combinations of the undetermined product and the production route; a production path determination unit that determines a next product, which is the undetermined product to be next introduced into the production line, and a next production path, which is a production path for the next product, based on the calculated increase in load time for each of the product path combinations; A production route determination program characterized by causing the program to function as a production route determination program.

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