Production sequence planning system

Abstract

To provide a production sequence planning system capable of planning a production sequence while simultaneously considering production constraints of each manufacturing process.SOLUTION: There is provided a production sequence planning system 10 for planning a sequence for producing vehicles with multiple specifications on a production line having multiple manufacturing processes. The production sequence planning system 10 includes: an acquisition unit 11 that acquires a production plan including vehicle specifications and production quantities for each specification, production lead times for each manufacturing process, and production constraints that inhibit production leveling in each manufacturing process; a priority setting unit 12 that sets priority in stages for each of the production constraints acquired by the acquisition unit 11 based on the degree of influence on production; and a production sequence determining unit 13 that determines the production sequence of vehicles based on the production plan, production lead time, and production constraints acquired by the acquisition unit 11 and the priority set by the priority setting unit 12.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present invention relates to a production sequence planning system. [Background technology]

[0002] In the related art, a production sequence planning system has been known that divides parts into multiple part groups based on the use sequence of parts in multiple downstream processes and the shipping times at which parts are shipped from an upstream process to the multiple downstream processes, and then levels the production sequence of the parts for each part group, as described in Patent Document 1, for example. This production sequence planning system makes it possible to produce the parts required for each downstream process while observing the production constraints of the upstream process, without making complicated adjustments in the upstream process that ships multiple types of parts to multiple downstream processes. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Japanese Patent Application Laid-Open No. 2017-188026 Summary of the Invention [Problem to be solved by the invention]

[0004] However, even if the above-mentioned production sequence planning system attempts to plan a production sequence that takes into account the production constraints of each manufacturing process, the production constraints of the preceding and succeeding processes may conflict with each other, making it difficult to plan a production sequence that simultaneously takes into account the production constraints of these processes.

[0005] The present invention has been made to solve these technical problems, and has as its object to provide a production sequence planning system that can plan a production sequence that simultaneously takes into account the production constraints of each manufacturing process. [Means for solving the problem]

[0006] The production sequence planning system according to the present invention is a production sequence planning system that plans a sequence for producing products with multiple specifications on a production line having multiple manufacturing processes, and is characterized by comprising: an acquisition unit that acquires a production plan including the product specifications and production quantities for each specification, the production lead time for each manufacturing process, and production constraints that hinder the leveling of production in each manufacturing process; a priority setting unit that sets a priority in stages for each of the production constraints acquired by the acquisition unit based on the degree of impact on production; and a production sequence determination unit that determines the production sequence of the products based on the production plan, the production lead time, and the production constraints acquired by the acquisition unit and the priorities set by the priority setting unit.

[0007] In the production sequence planning system according to the present invention, the production sequence determination unit determines the production sequence of products based on the production plan, production lead time, and production constraints acquired by the acquisition unit and the priorities set by the priority setting unit, so that the production sequence can be planned while simultaneously considering the production constraints of each manufacturing process. As a result, it is possible to avoid deviations between the planned production sequence and the actual production sequence, thereby improving production leveling, reducing disruptions in parts procurement due to deviations between the planned production sequence and the actual production sequence, and reducing parts inventory.

[0008] In the production sequence planning system according to the present invention, it is preferable that the priority setting unit further sets a weight in stages for each of the production constraints based on the degree of impact on production, and the production sequence determination unit calculates an evaluation score for each production sequence created based on the production plan and the production lead time by multiplying the number of violations for each production constraint with the highest priority among the priorities set by the priority setting unit by the weight corresponding to the production constraint with the highest priority, and determines the production sequence with the smallest calculated evaluation score as the production sequence for the product. In this way, since the production sequence with the smallest evaluation score is determined as the production sequence for the product, it is possible to determine the production sequence with the fewest production constraints that hinder production leveling as the production sequence for the product.

[0009] Furthermore, in the production sequence planning system according to the present invention, when the evaluation scores of production sequences calculated by multiplying the number of violations of each of the production constraints with the highest priority among the priorities set by the priority setting unit by the weight corresponding to each of the highest priority production constraints are the same, the production sequence determination unit preferably calculates the evaluation score of each production sequence by multiplying the number of violations of each of the production constraints with the next highest priority by the weight corresponding to each of the production constraints with the next highest priority for the production sequences with the same evaluation scores, in order of decreasing priority, and determines the production sequence with the lowest evaluation score as the production sequence for the product. In this way, it is possible to reliably determine the production sequence with the fewest production constraints that hinder production leveling as the production sequence for the product.

[0010] In addition, in the production sequence planning system according to the present invention, if a trade-off occurs between a production constraint of a preceding process and a production constraint of a following process in a production sequence created based on the production plan and the production lead time, it is preferable that the production sequence determination unit restructures the production sequence so as to resolve the trade-off by using a temporary storage area for the products provided between the preceding process and the following process, and calculates the evaluation score for the restructured production sequence. By restructuring the production sequence in this way, the trade-off between the production constraint of the preceding process and the production constraint of the following process can be resolved. [Effects of the Invention]

[0011] According to the present invention, it is possible to plan a production sequence that simultaneously takes into account the production constraints of each manufacturing process. [Brief explanation of the drawings]

[0012] [Figure 1] 1 is a schematic configuration diagram showing a production sequence planning system according to an embodiment; [Figure 2] FIG. 10 is a diagram illustrating an example of production constraints for each manufacturing process, and the priorities and weights of the production constraints. [Figure 3]1 is a flowchart showing a production sequence planning method using the production sequence planning system. [Figure 4] FIG. 10 is a schematic diagram showing an example of creating a tentative production sequence for a body process based on a production plan. [Figure 5] FIG. 10 is a schematic diagram showing an example in which the production lead time of the body process is reflected. [Figure 6] FIG. 10 is a schematic diagram for explaining a trade-off relationship in production constraints in the preceding and following processes and the reorganization of the production sequence. [Figure 7] FIG. 10 is a schematic diagram showing an example of rearranging a production sequence. [Figure 8] FIG. 10 is a diagram showing the number of violations of production constraints. [Figure 9] FIG. 10 is a diagram for explaining calculation of evaluation scores for a production sequence. [Figure 10] FIG. 10 is a diagram illustrating an example of constraint conditions, KPI units, and fluctuation ranges of the units. [Figure 11] FIG. 10 is a diagram illustrating an example before normalization is introduced. [Figure 12] FIG. 10 is a diagram illustrating an example after normalization is introduced. DETAILED DESCRIPTION OF THE INVENTION

[0013] An embodiment of a production sequence planning system according to the present invention will be described below with reference to the drawings. The production sequence planning system 10 of this embodiment is a system that plans the sequence for sequentially producing products of multiple specifications on a production line having multiple manufacturing processes, and more specifically, is a system that determines the production sequence of products on a day based on a production plan for each product by schedule. The following description will be given using an example in which vehicles of multiple specifications are produced on a production line having a body process, a painting process, and an assembly process, but the products and manufacturing processes related to the present invention are not limited to this.

[0014] 1 is a schematic diagram showing the configuration of a production sequence planning system according to an embodiment. The production sequence planning system 10 is configured by a microcomputer that combines, for example, a CPU (Central Processing Unit) that executes calculations, a ROM (Read Only Memory) as a secondary storage device that stores programs for the calculations, and a RAM (Random Access Memory) as a temporary storage device that saves the calculation progress and temporary control variables, and plans the production sequence by executing the stored programs.

[0015] As shown in FIG. 1, the production sequence planning system 10 mainly includes an acquisition unit 11, a priority setting unit 12, a production sequence determination unit 13, and an output unit 14.

[0016] The acquisition unit 11 acquires a production plan including vehicle specifications and production quantities for each specification, the production lead time for each manufacturing process (i.e., the body process, painting process, and assembly process), and production constraints that hinder the leveling of production in each manufacturing process. The acquisition unit 11 outputs the acquired production constraints that hinder the leveling of production in each manufacturing process (hereinafter simply referred to as "production constraints of each manufacturing process") to the priority setting unit 12. The acquisition unit 11 also outputs the acquired production plan, production lead time for each manufacturing process, and production constraints for each manufacturing process to the production sequence determination unit 13.

[0017] In this embodiment, vehicle specifications include not only differences in the type of car (so-called car model), but also differences in color, four-wheel drive (4WD) or two-wheel drive (2WD), etc., even for the same car model.

[0018] The production plan includes the specifications of the vehicles to be produced each day and the number of vehicles of each specification, and is prepared, for example, by the production planning department based on order information provided by the sales department. For example, as shown in Fig. 4, this production plan may include information such as two vehicles of specification A, two vehicles of specification B, and two vehicles of specification C. When the production plan is input into a dedicated terminal (not shown) by the production planning department, it is automatically transmitted to the acquisition unit 11. In addition, various information related to the vehicle specifications is stored in advance, for example, in the production sequence planning system 10.

[0019] The production lead time for each manufacturing process refers to the time from when a vehicle is introduced into each manufacturing process to when that process is completed (for example, the time from when an assembly process is started to when it is completed).

[0020] The production constraints for each manufacturing process are factors that hinder production leveling in each manufacturing process, and are acquired by the acquisition unit 11 in a list of items such as target process, constraint type, constraint condition, and explanation, as shown in Fig. 2. Specifically, as shown in Fig. 2, in the body process, two consecutive roof vehicles are restricted from being sent down the production line due to the body equipment. In the assembly process, a spacing of nine four-wheel drive vehicles is restricted in order to perform backup outside the production line.

[0021] The priority setting unit 12 sets a priority for each production constraint of each manufacturing process acquired by the acquisition unit 11 based on the degree of impact on production. Specifically, the priority setting unit 12 sets a higher priority for a production constraint that has a greater impact on production. In this embodiment, the priority is set in three stages, each represented by the numbers "1," "2," and "3." Of these, the highest priority is "3," and the lowest is "1."

[0022] For example, among the production constraints for each manufacturing process shown in Figure 2, the exterior body color change in the painting process has a relatively small impact on production, so its priority is set to "1." On the other hand, the body equipment constraint has a relatively large impact on production, so its priority is set to "3." By setting the priority of production constraints based on the degree of impact on production in this way, it becomes possible to control the production constraints that you want to prioritize.

[0023] Furthermore, to prevent variations in the set priorities, the priority setting unit 12 sets weights in stages for each production constraint of each manufacturing process. At this time, the priority setting unit 12 sets weights based on the degree of impact on production, similar to setting priorities. That is, the greater the impact on production of a production constraint, the greater the weight set. The set weights are displayed, for example, as numbers from "1" to "10," with larger numbers representing larger weights. In this way, it becomes possible to further finely divide the priorities of multiple production constraints set to the same priority.

[0024] The priority setting unit 12 outputs the set priority and weight of each production constraint to the production sequence determination unit 13.

[0025] The production sequence determination unit 13 determines the production sequence of vehicles based on the production plan, production lead time of each production process, and production constraints of each production process acquired by the acquisition unit 11, and the priorities set by the priority setting unit 12. More specifically, the production sequence determination unit 13 creates a plurality of production sequences based on the production plan and production lead time acquired by the acquisition unit 11, and further calculates an evaluation score for each created production sequence by multiplying the number of violations of each production constraint with the highest priority among the priorities set by the priority setting unit 12 by the weight corresponding to each production constraint with the highest priority, and determines the production sequence with the smallest calculated evaluation score as the production sequence of vehicles.

[0026] Then, if the evaluation scores of the production sequences calculated by multiplying the number of violations of each of the production constraints with the highest priority among the priorities set by the priority setting unit 12 by the weight corresponding to each of the production constraints with the highest priority are the same, the production sequence determination unit 13 calculates the evaluation score of each production sequence by multiplying the number of violations of each of the production constraints with the next highest priority by the weight corresponding to each of the production constraints with the next highest priority for the production sequences with the same evaluation scores, and repeats this process in order of decreasing priority, thereby determining the production sequence with the smallest evaluation score as the production sequence for vehicles.

[0027] Furthermore, if a conflict occurs between the production constraints of a preceding process and those of a succeeding process in a production sequence created based on the production plan and production lead time, the production sequence determination unit 13 rearranges the vehicle production sequence so as to resolve the conflict by using a vehicle temporary storage area provided between the preceding process and the succeeding process, and calculates the evaluation score for the rearranged production sequence. This production sequence determination unit 13 will be described in more detail later.

[0028] The output unit 14 has, for example, a display or the like, and displays the vehicle production sequence determined by the production sequence determination unit 13 on the display to inform workers or the like.

[0029] A production sequence planning method using the production sequence planning system 10 will be explained below with reference to Figure 3. The production sequence planning method includes step S11 of creating a tentative production sequence for the body process, step S12 of reflecting the production lead time for the body process, step S13 of creating a tentative production sequence for the painting process, step S14 of reflecting the production lead time for the painting process, step S15 of restructuring the production sequence, step S16 of evaluating the production sequence, step S17 of updating the production sequence, step S18 of determining whether evaluation of all production sequences has been completed, and step S19 of determining the optimal production sequence.

[0030] First, in step S11 of creating a tentative production sequence for the body process, the production sequence determination unit 13 creates a tentative production sequence for vehicles in the body process based on the production plan acquired by the acquisition unit 11. At this time, it is preferable that the production sequence determination unit 13 does not create a vehicle production sequence based on special logic, but rather creates a tentative production sequence for the body process that standardizes vehicle specifications as much as possible.

[0031] For example, as shown in Figure 4, if the daily production plan is to produce two vehicles each of specifications A, B, and C, the production sequence determination unit 13 creates a tentative production sequence so that the vehicles are arranged in the following order along the direction of travel of the production line: the first vehicle of specification A, the first vehicle of specification B, the second vehicle of specification A, the first vehicle of specification C, the second vehicle of specification B, and the second vehicle of specification C. If two vehicles each of specifications A, B, and C are produced without considering the leveling of vehicle specifications, there will be 90 different production sequence patterns.

[0032] Next, in step S12 of reflecting the production lead time for the body process, the production sequence determination unit 13 reflects the production lead time for each specification in the body process in the tentative production sequence created in step S11, and rearranges the production sequence of vehicles based on the reflected results.

[0033] For example, as shown in Fig. 5, if the production lead time for specification A in the body process is 100 minutes, the production lead time for specification B is 150 minutes, and the production lead time for specification C is 50 minutes, the production sequence determination unit 13 will reflect the production lead time for each specification vehicle and rearrange the production sequence of the vehicles, assuming production leveling. As a result, the provisional production sequence shown in Fig. 4 will change to the following order in the direction of travel of the production line: first vehicle of specification A, first vehicle of specification C, second vehicle of specification A, first vehicle of specification B, second vehicle of specification C, second vehicle of specification B (see Fig. 5).

[0034] Next, in step S13 of creating a tentative production sequence for the painting process, the production sequence determination unit 13 creates the production sequence that reflects the production lead time of the body process in step S12 as a tentative production sequence for the painting process.

[0035] Next, in step S14 of reflecting the production lead time for the painting process, the production sequence determination unit 13 reflects the production lead time of each specification in the painting process in the tentative production sequence for the painting process created in step S13, and further rearranges the production sequence of vehicles based on the reflected results.

[0036] Next, in the production sequence restructuring step S15, the production sequence determination unit 13 determines whether there is a trade-off between the production constraints of the preceding body process or painting process and the production constraints of the following assembly process, and if it determines that there is a trade-off, it restructures the production sequence by using storage (i.e., a temporary vehicle holding area) provided between the painting process and the assembly process to resolve the trade-off.

[0037] Here, the trade-offs in production constraints between the preceding and following processes and the restructuring of the production sequence will be explained in detail with reference to FIGS. 6 and 7.

[0038] For example, when two vehicles with specification B are lined up in a row, as shown in Figure 6(a), there is no problem with the production constraints of the body process, but there is a problem with the production constraints of the assembly process. In other words, when two vehicles with specification B are lined up in a row, a trade-off occurs between the production constraints of the body process and the assembly process.

[0039] To resolve such a conflict, the present invention uses storage provided on the production line to create a production sequence that can resolve the conflicting production constraints. This is called restructuring the production sequence. In this case, the production sequence determination unit 13 resolves the conflict by using storage to swap the second machine of specification B with the second machine of specification A located behind it, as shown in Figure 6(b), for example.

[0040] Storage is defined by the number of vehicles that can be moved and the storage capacity. The number of vehicles that can be moved refers to the maximum number of vehicles that can be rearranged through rebuilding. The storage capacity refers to the maximum number of vehicles that can be put into storage. In this embodiment, an example will be given in which the number of vehicles that can be moved and the storage capacity are both three vehicles, but the number of vehicles that can be moved and the storage capacity may be the same or different.

[0041] For example, as shown in FIG. 7, if the production sequence rearranged by the production sequence determination unit 13 in step S14 (i.e., the production sequence reflecting the production lead time of the painting process) is in the order of vehicles A, B, C, D, E, F, G, and H in the direction of travel of the production line, and the number of vehicles that can be moved and the storage capacity are both three, then the production sequence after reconstruction will be in the order of vehicles A, B, C, F, G, E, D, and H in the direction of travel of the production line.

[0042] At this time, the production sequence determination unit 13 rearranges the production sequence as follows. First, as shown in FIG. 7, the production sequence determination unit 13 causes vehicles A, B, and C to go directly. Here, "going directly" means that the vehicles pass through the storage without being put into the storage. Next, the production sequence determination unit 13 causes vehicles D and E to enter the storage sequentially. Thereafter, the production sequence determination unit 13 causes vehicles F and G to go directly. After causing vehicles F and G to go directly, the production sequence determination unit 13 causes vehicle E, of vehicles D and E that entered the storage, to leave first. Then, because vehicle D, which entered the storage, has been overtaken by vehicles F, G, and E and the number of vehicles that can be moved has reached the limit of three, the production sequence determination unit 13 also causes vehicle D to leave. Thereafter, the production sequence determination unit 13 causes vehicle H to go directly. This completes the rearrangement of the production sequence.

[0043] Furthermore, the production sequence determination unit 13 sets the production sequence of the rebuilt vehicles as a provisional production sequence for the assembly process.

[0044] Subsequently, in the production sequence evaluation step S16, the production sequence determination unit 13 calculates an evaluation score for the tentative production sequence of the assembly process as follows.

[0045] First, the production sequence determination unit 13 determines whether or not there are any parts in the vehicle production sequence (i.e., the tentative production sequence of the assembly process) that violate the production constraints in light of the production constraints of each manufacturing process shown in Figure 8, and if there are any parts that violate the production constraints, it counts them as violations of the production constraints.

[0046] Next, the production sequence determination unit 13 extracts the production constraint with the highest priority from the priorities set by the priority setting unit 12. Next, the production sequence determination unit 13 multiplies the number of violations for each of the extracted production constraints by the weight corresponding to the production constraint with the highest priority, i.e., "number of violations x weight." As described above, the weight is a number set by the priority setting unit 12 based on the degree of impact on production, and the numerical value may differ even for production constraints with the same priority. Next, the production sequence determination unit 13 calculates the sum of "number of violations x weight" for all production constraints with the highest priority, and sets the calculated sum as the evaluation score for the tentative production sequence of the assembly process.

[0047] Furthermore, the production sequence determination unit 13 calculates the evaluation score for each of all production sequences using the above-described method, compares the calculated evaluation scores, and selects the production sequence with the smallest evaluation score.

[0048] If the evaluation scores of the production sequences calculated by multiplying the number of violations of the production constraint with the highest priority among the priorities set by the priority setting unit 12 by the weight corresponding to each of the production constraints with the highest priority are the same, the production sequence determination unit 13 calculates the evaluation score of each production sequence by multiplying the number of violations of the production constraint with the next highest priority by the weight corresponding to each of the production constraints with the next highest priority for the production sequences with the same evaluation scores, and repeats this process in order of decreasing priority, thereby determining the production sequence with the smallest evaluation score as the production sequence for vehicles.

[0049] 9, for example, the production constraints with the highest priority (i.e., priority "3") among the priorities set by the priority setting unit 12 are "side member" in the body process, "two roof units in a row" in the body process, and "six roof units apart" in the assembly process. Therefore, for any production sequence, the production sequence determination unit 13 extracts production constraints such as "side member," "two roof units in a row," and "six roof units apart," multiplies each production constraint by "number of violations x weight," and further calculates the sum of the products of all production constraints to calculate an evaluation score for the production sequence.

[0050] For example, for the first production sequence shown in Figure 9, the evaluation score = number of violations for side members × weight of side members (1 × 10) + number of violations for two consecutive roofs × weight of two consecutive roofs (1 × 5) + number of violations for six roof intervals × weight of six roof intervals (1 × 5) = 20 points. Evaluation scores for the second and third production sequences are calculated in a similar manner.

[0051] Then, once the evaluation scores for the production sequences have been calculated, the production sequence determination unit 13 compares them with the evaluation scores for the production sequences stored in the memory of the production sequence determination unit 13, and selects (in other words, determines) the production sequence with the smallest evaluation score as the provisional optimal production sequence. Note that when the first production sequence is evaluated, the provisional optimal production sequence and its evaluation score have not yet been stored in the memory of the production sequence determination unit 13, so the production sequence determination unit 13 selects the first production sequence as the provisional optimal production sequence and stores the first production sequence and its evaluation score in memory as an updated production sequence (step S17).

[0052] Then, once the evaluation score for the second production order is calculated, the production sequence determination unit 13 evaluates the second production order by comparing the evaluation score for the second production order with the evaluation score of the tentative optimal production order (here, the first production order) stored in memory (step S16). If the evaluation score for the second production order is smaller than the evaluation score of the tentative optimal production order, the production sequence determination unit 13 selects the second production order as the tentative optimal production order, deletes the old tentative optimal production order (i.e., the first production order) and its evaluation score stored in memory, and stores the second production order and its evaluation score in memory, thereby updating the production order (step S17).

[0053] On the other hand, if the evaluation score for the second production order is greater than the evaluation score for the provisional optimal production order (i.e., the first production order) stored in memory, the production order determination unit 13 does not delete the provisional optimal production order (i.e., the first production order) and its evaluation score stored in memory, and ends the update of the production order.

[0054] 9, when the evaluation scores for the second and third production orders are the same when the priority is "3," the production sequence determination unit 13 calculates evaluation scores for the second and third production orders in the same manner as described above using the number of violations for each of the production constraints with the next highest priority (here, the priority is "2") and the weights corresponding to each of the production constraints with the next highest priority (priority is "2"), and compares the two evaluation scores. As a result, the evaluation score for the third production order (80) is lower than the evaluation score for the second production order (90), so the production sequence determination unit 13 ultimately selects the third production order as the provisional optimal production order. Even if the priority is "2," if the evaluation score for the second production order and the evaluation score for the third production order are the same, the production order determination unit 13 calculates the evaluation scores for each of the production constraints with the next highest priority (here, the priority is "1") in the same manner as described above using the number of violations and the weights corresponding to the production constraints with the next highest priority (here, the priority is "1"), and compares them.

[0055] Furthermore, in the production sequence planning method according to this embodiment, when the units of KPIs (Key Performance Indicators) to be evaluated differ depending on the production constraints, a method called normalization is used that enables production constraints with different evaluation scales to be compared using the same scale. Specifically, for example, as shown in Fig. 10, there are many production constraints, each with a different KPI unit and a different fluctuation range for the unit.

[0056] For example, if the same priority is assigned to the "continuous interval constraint," "specification grouping," and "reconstruction" shown in FIG. 10, and the weights are assigned in the order of "continuous interval constraint" >> "specification grouping" >> "reconstruction" (for example, the respective weights are "10," "2," and "1"), then, as shown in FIG. 11, no matter how much the weights are adjusted, differences in the vehicle user's orders (in other words, orders) will cause a problem in which the production sequence that should be selected simply by the above-mentioned "number of violations x weight" cannot be selected.

[0057] In other words, as can be seen from the weights that have been set (see Figure 11), it would be best to place emphasis on the "sequential interval constraint" and select the first production sequence with the fewest violations, but because the evaluation score for the second production sequence is lower than that of the first production sequence, the second production sequence ends up being selected.

[0058] To solve this problem, in this embodiment, evaluation scores are calculated after normalization, which allows production constraints with different evaluation scales to be compared using the same scale. Specifically, as shown in FIG. 12, the production sequence determination unit 13 sets the normalized value of the number of violations to "10," the normalized value of the number of transitions to "100," and the normalized value of the number of storage entries to "1000." Then, the production sequence determination unit 13 divides the original number of violations by the normalized value (e.g., 5 / 10=0.5 for the first production sequence), divides the original number of transitions by the normalized value (e.g., 50 / 100=0.5 for the first production sequence), and divides the original number of storage entries by the normalized value (e.g., 200 / 1000=0.2 for the first production sequence). In other words, the production sequence determination unit 13 converts these violations into values between 0 and 1. Next, the production sequence determination unit 13 calculates evaluation scores for each of the violations using the converted numbers of violations using the method described above, and selects the production sequence with the smallest calculated evaluation score. By doing this, the evaluation score for the first production order will be smaller than that for the second production order, and the first production order will be selected.

[0059] Subsequently, in a production sequence update step S17, the production sequence determination unit 13 stores the production sequence selected in step S16 in memory as a provisional optimum production sequence.

[0060] Next, in step S18, the production sequence determination unit 13 determines whether or not the evaluation of all production sequences has been completed. For example, as described above, when two vehicles each of specifications A, B, and C are produced and the standardization of vehicle specifications is not taken into consideration, there are 90 production sequence patterns. Therefore, the production sequence determination unit 13 determines whether or not the evaluation of all production sequences has been completed depending on whether the number of production sequence patterns has reached 90.

[0061] If it is determined that evaluation of all production sequences has not been completed, the process returns to step S11, and the processes of steps S11 to S18 are repeated. On the other hand, if it is determined that evaluation of all production sequences has been completed, the process proceeds to step S19. In step S19, the production sequence determination unit 13 determines the tentative production sequence updated in step S17 as the optimal production sequence. This optimal production sequence corresponds to the "product production sequence" recited in the claims.

[0062] Once the optimal production sequence has been determined, the production sequence determination unit 13 outputs the determined optimal production sequence to the output unit 14. The output unit 14 displays the optimal production sequence on a built-in display and notifies workers, etc. This completes the series of processes, i.e., the production sequence planning is complete.

[0063] In the production sequence planning system 10 of this embodiment, the production sequence determination unit 13 calculates an evaluation score for each production sequence created based on the production plan and production lead time by multiplying the number of violations for each production constraint with the highest priority among the priorities set by the priority setting unit 12 by the weight corresponding to each production constraint with the highest priority, and determines the production sequence with the smallest calculated evaluation score as the vehicle production sequence. By determining the production sequence with the smallest evaluation score in this way, in other words, the production sequence with the fewest production constraints that hinder production leveling, as the vehicle production sequence, it is possible to plan a production sequence that simultaneously takes into account the production constraints of each manufacturing process.

[0064] Furthermore, if the evaluation scores of production sequences calculated by multiplying the number of violations of the production constraint with the highest priority by the weight corresponding to the production constraint with the highest priority are the same, the production sequence determination unit 13 calculates the evaluation score of each production sequence by multiplying the number of violations of the production constraint with the next highest priority by the weight corresponding to the production constraint with the next highest priority for the production sequences with the same evaluation scores, and repeats this process in order of decreasing priority, thereby determining the production sequence with the lowest evaluation score as the production sequence for vehicles.In this way, it is possible to reliably determine the production sequence with the fewest production constraints that hinder production leveling as the production sequence for products.

[0065] Furthermore, since it is possible to plan a production sequence that simultaneously takes into account production constraints that hinder production leveling in multiple processes, it is possible to avoid deviations between the planned production sequence and the actual production sequence. This improves production leveling, while reducing disruptions in parts procurement caused by deviations between the planned production sequence and the actual production sequence, and reducing parts inventory. Furthermore, by avoiding deviations between the planned production sequence and the actual production sequence, it is possible to suppress fluctuations in worker workloads and improve process organization. As a result, it becomes possible to flexibly produce vehicles with a wide variety of specifications.

[0066] Although the embodiments of the present invention have been described in detail above, the present invention is not limited to the above-described embodiments, and various design modifications can be made without departing from the spirit of the present invention as set forth in the claims. For example, the priority of production constraints may be set in four or more stages. [Explanation of symbols]

[0067] 10: Production sequence planning system, 11: Acquisition unit, 12: Priority setting unit, 13: Production sequence determination unit.

Claims

1. A production sequence planning system that plans a sequence for producing products of multiple specifications on a production line having multiple manufacturing processes, an acquisition unit that acquires a production plan including specifications of the product and production quantities for each specification, a production lead time for each manufacturing process, and production constraints that hinder the leveling of production in each manufacturing process; a priority setting unit that sets a priority level in stages for each of the production constraints acquired by the acquisition unit based on the degree of impact on production; a production sequence determination unit that determines a production sequence of the products based on the production plan, the production lead time, and the production constraints acquired by the acquisition unit and the priorities set by the priority setting unit; Equipped with the priority setting unit further sets a weight in stages for each of the production constraints based on the degree of impact on production; the production sequence determination unit calculates an evaluation score for each production sequence created based on the production plan and the production lead time by multiplying the number of violations of each production constraint with the highest priority among the priorities set by the priority setting unit by a weight corresponding to each production constraint with the highest priority, and determines the production sequence with the smallest calculated evaluation score as the production sequence for the product.

2. 2. The production sequence planning system according to claim 1, wherein, when the evaluation scores of the production sequences calculated by multiplying the number of violations of each of the production constraints with the highest priority among the priorities set by the priority setting unit by the weight corresponding to each of the production constraints with the highest priority are the same, the production sequence determination unit calculates the evaluation score of each production sequence by multiplying the number of violations of each of the production constraints with the next highest priority by the weight corresponding to each of the production constraints with the next highest priority for the production sequences with the same evaluation scores, and repeats this process in order of decreasing priority, thereby determining the production sequence with the smallest evaluation score as the production sequence for the product.

3. 3. The production sequence planning system according to claim 1, wherein, when a conflict occurs between a production constraint of a preceding process and a production constraint of a subsequent process in a production sequence created based on the production plan and the production lead time, the production sequence determination unit restructures the production sequence so as to eliminate the conflict by using a temporary storage area for the products provided between the preceding process and the subsequent process, and calculates the evaluation score for the restructured production sequence.

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