JP7718322B2 - Production sequence planning system - Google Patents

Description

The present invention relates to a production sequence planning system.

In the field of this technology, a production sequence planning system has been known, as described in Patent Document 1, for example. This system divides parts into multiple part groups based on the order in which parts are used in multiple downstream processes and the shipping times at which parts are shipped from an upstream process to the multiple downstream processes, and then standardizes the production sequence of the parts for each part group. This production sequence planning system makes it possible to produce the parts required for each downstream process while adhering to 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.

Japanese Patent Application Laid-Open No. 2017-188026

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

The present invention was made to solve these technical problems, and aims to provide a production sequence planning system that can plan a production sequence while simultaneously taking into account the production constraints of each manufacturing process.

The production sequence planning system of the present invention is a production sequence planning system that plans the 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 level 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 for the 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.

In the production sequence planning system of 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, making it possible to plan a production sequence that simultaneously takes into account 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.

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 highest priority production constraint, and determines the production sequence with the lowest calculated evaluation score as the production sequence for the product. In this way, since the production sequence with the lowest 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.

Furthermore, in the production sequence planning system according to the present invention, if the evaluation scores of 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 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 for 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 next highest priority production constraints 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.

Furthermore, in the production sequence planning system according to the present invention, if a trade-off occurs between the production constraints of a preceding process and the production constraints of a following process in a production sequence created based on the production plan and the production lead time, the production sequence determination unit preferably restructures the production sequence to resolve the trade-off 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 constraints of the preceding process and the production constraints of the following process can be resolved.

This invention makes it possible to plan production sequences that simultaneously take into account the production constraints of each manufacturing process.

1 is a schematic configuration diagram showing a production sequence planning system according to an embodiment; FIG. 10 is a diagram illustrating an example of production constraints for each manufacturing process, and the priorities and weights of the production constraints. 1 is a flowchart showing a production sequence planning method using the production sequence planning system. FIG. 10 is a schematic diagram showing an example of creating a tentative production sequence for a body process based on a production plan. FIG. 10 is a schematic diagram showing an example in which the production lead time of the body process is reflected. 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. FIG. 10 is a schematic diagram showing an example of rearranging a production sequence. FIG. 10 is a diagram showing the number of violations of production constraints. FIG. 10 is a diagram for explaining calculation of evaluation scores for a production sequence. FIG. 10 is a diagram illustrating an example of constraints, KPI units, and unit fluctuation ranges. FIG. 10 is a diagram illustrating an example before normalization is introduced. FIG. 10 is a diagram illustrating an example after normalization is introduced.

An embodiment of a production sequence planning system according to the present invention will now be described 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 with multiple specifications on a production line having multiple manufacturing processes, and more specifically, is a system that determines the production sequence for each day's products based on a production plan for each product by schedule. Below, an example will be described in which vehicles with 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.

Figure 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 using 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.

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

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 production leveling in each manufacturing process. The acquisition unit 11 outputs the acquired production constraints that hinder production leveling in each manufacturing process (hereinafter simply referred to as "production constraints for 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.

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

The production plan includes the vehicle specifications and the number of units of each specification to be produced each day, and is created, for example, by the production planning department based on order information provided by the sales department. For example, as shown in Figure 4, this production plan may include information such as two units of specification A, two units of specification B, and two units of specification C. Once the production plan is entered into a dedicated terminal (not shown) by the production planning department, it is automatically sent to the acquisition unit 11. Furthermore, various information regarding vehicle specifications is stored in advance, for example, in the production sequence planning system 10.

The production lead time for each manufacturing process refers to the time from when a vehicle enters a manufacturing process to when that process is completed (for example, the time from when an assembly process begins to when it is completed).

Production constraints for each manufacturing process are factors that hinder production leveling in that manufacturing process, and are acquired by the acquisition unit 11 in a list of items such as target process, constraint type, constraint conditions, and explanation, as shown in Figure 2. Specifically, as shown in Figure 2, in the body process, two consecutive roof vehicles cannot be sent down the production line due to body equipment issues. In the assembly process, the interval between four-wheel drive vehicles is limited to nine vehicles in order to allow backup outside the production line.

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, priorities are set in three levels, represented by the numbers "1," "2," and "3." Of these, the highest priority is "3," and the lowest is "1."

For example, of 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 in this way based on the degree of impact on production, it is possible to control the production constraints that you want to prioritize.

In addition, 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, just as it does when setting priorities. That is, the greater the impact on production of a production constraint, the greater the weight it is set to. The weights that are set are displayed, for example, as numbers from "1" to "10," with larger numbers representing greater weights. In this way, it is possible to further finely divide the priorities of multiple production constraints that have been set to the same priority.

The priority setting unit 12 outputs the priority and weight of each production constraint that it has set to the production sequence determination unit 13.

The production sequence determination unit 13 determines the production sequence for vehicles based on the production plan, production lead time for each production process, and production constraints for 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 multiple 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 the production constraint with the highest priority among the priorities set by the priority setting unit 12 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 vehicles.

Then, 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 highest priority production constraints are the same, the production sequence determination unit 13 calculates the evaluation score for 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 lowest evaluation score as the vehicle production sequence.

Furthermore, if a conflict occurs between the production constraints of a preceding process and those of a following process in a production sequence created based on the production plan and production lead time, the production sequence determination unit 13 will rearrange the vehicle production sequence to resolve the conflict using a temporary vehicle holding area provided between the preceding and following processes, and will calculate the above evaluation score for the rearranged production sequence. This production sequence determination unit 13 will be described in further detail below.

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

The 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.

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.

For example, as shown in Figure 4, if the daily production plan is to produce two vehicles each of specification A, specification B, and specification C, the production sequence determination unit 13 creates a tentative production sequence by arranging the vehicles in the following order along 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. Note that if two vehicles each of specification A, specification B, and specification C are produced and the leveling of vehicle specifications is not taken into consideration, there will be 90 possible production sequence patterns.

Next, in step S12, which reflects 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 vehicle production sequence based on the reflected results.

For example, as shown in Figure 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 assume production leveling and reflect the production lead time for each specification vehicle, rearranging the production sequence of the vehicles. As a result, the provisional production sequence shown in Figure 4 will change to the following order in the direction of travel of the production line: first specification A vehicle, first specification C vehicle, second specification A vehicle, first specification B vehicle, second specification C vehicle, second specification B vehicle (see Figure 5).

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

Next, in step S14, which reflects the production lead time for the painting process, the production sequence determination unit 13 reflects the production lead time for each specification in the painting process in the tentative production sequence for the painting process created in step S13, and further rearranges the vehicle production sequence based on the reflected results.

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.

Here, we will explain in detail the trade-offs in production constraints between the preceding and following processes and how to restructure the production sequence, using Figures 6 and 7.

For example, as shown in Figure 6(a), if two vehicles with specification B are lined up in a row, there will be no problem with the production constraints of the body process, but there will be problems with the production constraints of the assembly process. In other words, if two vehicles with specification B are lined up in a row, a trade-off will arise between the production constraints of the body process and the assembly process.

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

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 when rebuilding. The storage capacity refers to the maximum number of vehicles that can be placed in storage. In this embodiment, an example is given in which the number of vehicles that can be moved and the storage capacity are both three, but the number of vehicles that can be moved and the storage capacity may be the same or different.

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 for 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.

At this time, the production sequence determination unit 13 reorganizes the production sequence as follows. First, as shown in FIG. 7, the production sequence determination unit 13 sends vehicles A, B, and C directly. Here, "directly" means that the vehicles pass through the storage without being put into it. Next, the production sequence determination unit 13 sequentially stores vehicles D and E in the storage. Thereafter, the production sequence determination unit 13 sends vehicles F and G directly. After sending vehicles F and G directly, the production sequence determination unit 13 causes vehicle E, of vehicles D and E that have entered the storage, to leave first. Then, because vehicle D, which has entered the storage, has been overtaken by vehicles F, G, and E and the limit of three vehicles that can be moved has been reached, the production sequence determination unit 13 also leaves vehicle D. Thereafter, the production sequence determination unit 13 sends vehicle H directly. This completes the reorganization of the production sequence.

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

Next, 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:

First, the production sequence determination unit 13 determines whether there are any violations of the production constraints for each manufacturing process shown in Figure 8 in the vehicle production sequence (i.e., the tentative production sequence for the assembly process), and if there are any violations, it counts them as violations of the relevant production constraints.

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 the "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.

Furthermore, the production sequence determination unit 13 calculates the evaluation score for each production sequence using the method described above, compares the calculated evaluation scores, and selects the production sequence with the smallest evaluation score.

In addition, 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 highest priority production constraints are the same, the production sequence determination unit 13 calculates the evaluation score for 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 lowest evaluation score as the vehicle production sequence.

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

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

Once the evaluation score for the production sequence has been calculated, the production sequence determination unit 13 compares it with the evaluation scores for the production sequences stored in its memory, and selects (in other words, determines) the production sequence with the smallest 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).

Then, once the evaluation score for the second production order has been 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 for the provisional 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 for the provisional optimal production order, the production sequence determination unit 13 selects the second production order as the provisional optimal production order and updates the production order by deleting the old provisional optimal production order (i.e., the first production order) and its evaluation score stored in memory and storing the second production order and its evaluation score in memory (step S17).

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 stored in memory (i.e., the first production order), 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 production order update.

Furthermore, as shown in Figure 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 the evaluation scores for the second and third production orders in the same manner as described above using the number of violations of the production constraint with the next highest priority (here, priority "2") and the weight corresponding to the production constraint with the next highest priority (priority "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. Furthermore, 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 sequence determination unit 13 calculates and compares the evaluation scores in the same manner as described above using the number of violations for each of the production constraints with the next highest priority (here, priority "1") and the weights corresponding to each of the production constraints with the next highest priority (priority "1").

In addition, in the production sequence planning method according to this embodiment, if the units of the KPIs (key performance indicators) to be evaluated differ due to production constraints, a technique called normalization is used, which allows production constraints with different evaluation scales to be compared using the same scale. Specifically, as shown in Figure 10, for example, there are many production constraints, each with different KPI units and unit fluctuation ranges.

For example, if the same priority is assigned to "Continuous Spacing Constraint," "Specification Grouping," and "Rebuild" as shown in Figure 10, and the weights are set in the order of "Continuous Spacing Constraint" >> "Specification Grouping" >> "Rebuild" (for example, the respective weights are "10," "2," and "1"), then, as shown in Figure 11, no matter how much the weights are adjusted, differences in the vehicle user's orders (in other words, orders) will mean that the production order that should be selected cannot be selected simply by the above-mentioned "Number of Violations x Weight."

In other words, as can be seen from the set weights (see Figure 11), it would be best to prioritize the "sequential interval constraint" and select the first production sequence with the fewest violations, but because the second production sequence has a lower evaluation score than the first production sequence, the second production sequence ends up being selected.

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 for the number of violations to "10," the normalized value for the number of transitions to "100," and the normalized value for the number of storage entries to "1000." Then, the production sequence determination unit 13 divides the original number of violations by these normalized values (e.g., 5/10 = 0.5 for the first production sequence), the original number of transitions by these normalized values (e.g., 50/100 = 0.5 for the first production sequence), and the original number of storage entries by these normalized values (e.g., 200/1000 = 0.2 for the first production sequence). In other words, these violations are converted into values between 0 and 1. Next, the production sequence determination unit 13 uses the converted violation counts to calculate evaluation scores for each constraint using the method described above, and selects the production sequence with the lowest calculated evaluation score. By doing this, the evaluation score for the first production order will be lower than that of the second production order, and the first production order will be selected.

Next, in production sequence update step S17, the production sequence determination unit 13 stores the production sequence selected in step S16 in memory as the provisional optimal production sequence.

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

If it is determined that evaluation of all production sequences has not been completed, processing returns to step S11, and the processing of steps S11 to S18 is repeated. On the other hand, if it is determined that evaluation of all production sequences has been completed, processing 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" described in the claims.

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.

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 lowest calculated evaluation score as the vehicle production sequence. By determining the production sequence with the lowest 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.

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 for 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.

In addition, because it is possible to plan a production sequence that simultaneously takes into account production constraints that hinder the leveling of production across multiple processes, it is possible to avoid discrepancies between the planned production sequence and the actual production sequence. This improves production leveling, while also reducing disruptions in parts procurement caused by discrepancies between the planned and actual production sequences and reducing parts inventory. Furthermore, by being able to avoid discrepancies between the planned and actual production sequences, 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.

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 stages, with four or more stages.

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

Claims (3)

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. 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. 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.