JP2005182685A - Production planning method and program - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To prepare a more suitable production plan while reflecting correction requests from a production planner, a higher-order system, or the like to an initial production plan. <P>SOLUTION: After data relating to resources and orders are read to perform data generation and various setting, the initial production plan is made (steps S1 to S3). Until a satisfactory production plan is made (loop R0), forced allotment is performed on the basis of commands for forced correction about resources and assigned dates of one or more selected works, from the production planner, the higher-order system, or the like to record a temporary production plan (steps S4 to S7). With respect to the temporary production plan, works are allotted to resources again to cancel violation of restrictions while maintaining sequences about resources, to which commanded works are allotted, and assigned dates of works allotted to respective resources (step S8). When a satisfactory production plan is made (loop R0), a result is preserved (step S9). <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

  The present invention relates to a production plan creation method and program for creating a production plan in a factory or the like by a computer.

  Conventionally, in a production planning system using a computer, for a plurality of orders, work necessary for manufacturing them is extracted, and the start date / time and end date / time, occupied resources, etc. are extracted for the extracted work. I will decide. In this case, in the production planning system, various constraints, that is, resource constraints (equipment constraints, worker constraints, etc.) and date and time constraints (delivery date and material acquisition date constraints, upstream work relative) It is required to formulate a production plan (optimum solution) that is more desirable for factories and companies while keeping as much as possible the restrictions on the general time context.

However, it is difficult to formulate an optimal solution for the following reasons.
A. Problem of number of combinations As the scale of the problem (number of orders, operations, resources, etc.) increases, the number of combinations increases explosively, so the time required to create a production plan also increases explosively.
B. Responding to constraints When plant constraints are complex, the algorithms for creating a better production plan within those constraints can also be complex, and in some cases, an effective algorithm cannot be implemented.

For this reason, the initial production plan created by the production planning system is frequently modified by the production plan creator or the production planning system. Conventionally, in such a case, the following method has been taken.
1. A person in charge of production planning manually corrects the results of production planning one by one.
2. In the production planning system, an attempt is made to improve the production plan by trial and error while changing the constraint condition or changing the allocation rule (see Patent Document 1).
3. The resource and date / time of the specific work are fixed, and other work is assigned to the production planning system.

Japanese Patent Laid-Open No. 7-210606

  However, the above-described method 1 has a problem that it requires a great deal of labor of the production plan creator. For example, when changing the scheduled date / time of one work, not only the start date / time and end date / time of the work is changed, but also the work competing with it, that is, the resource and date / time of the correction destination are already scheduled. It is necessary to change the start / end date and time for the work. In addition, for work that has a temporal restriction relationship with work to change the scheduled date and time (upstream work, downstream work, etc.), if the restriction is violated, it is necessary to resolve it. In this way, in a production plan, the modification of a plan for one operation also affects the plans for other operations, and it is necessary to modify a plan for many operations, which requires a great deal of labor from the production plan creator. Problem arises.

  In the method 2 described above, the production plan is corrected many times in the production plan system. However, in the general production plan system, the algorithm is fixed, and some parameters such as constraints are set in the production plan creator. However, if there is a request that the algorithm does not expect, a great deal of effort is required and the production plan maker can tolerate. In some cases, it may be difficult to create a production plan that can be used.

  Further, in the above-described method 3, depending on the fixed state of work and the algorithm of the production planning system, various restrictions may not be observed and an executable production plan may not be created. For example, when an upstream operation and a downstream operation are fixed (resources and date / time are fixed) for an order, if the time interval between them is too narrow, an intermediate process sandwiched between them will be assigned. There is a problem that a time constraint violation occurs. Further, when such a designation is made for a plurality of orders, there is a problem that an executable production plan cannot be created even if there is no problem with the order alone.

  The present invention has been made in view of the above problems, and a production plan capable of creating a more optimal production plan while reflecting a correction request for the initial production plan from a production plan creator or a host system or the like. A creation method and a program are provided.

Means and effects for solving the problems

  In order to solve the above-mentioned problem, the production plan creation method according to the present invention is a combination of a plurality of orders and a process necessary for manufacturing a product of the order, while maintaining a constraint condition, A production plan creation method for creating a production plan by allocating to resources selected from resources, an initial production plan obtaining step for obtaining an initial production plan that does not satisfy the constraints, and for the initial production plan A forced correction command step for selecting one or a plurality of operations and issuing a forced correction command for resources and allocation date and time, and selecting the operation selected based on the command ignoring the constraint condition A forced allocation step of allocating to the resource and updating the initial production plan as a provisional production plan, the resource allocating the work for which the command has been performed, and A constraint violation resolving step of allocating the work to the resource and updating the provisional production plan while maintaining an order related to the assignment date and time of the work assigned to each resource of the provisional production plan. It is characterized by being.

  In addition, the program according to the present invention allows a computer to select a resource selected from a plurality of resources, while maintaining the constraints, as a combination of a plurality of orders and a process necessary for manufacturing a product of the order. An initial production plan acquisition step for acquiring an initial production plan that is allocated and creates a production plan and that does not satisfy the constraints, and one or more operations for the initial production plan A forced correction command step for issuing a forced correction command for the resource and the allocation date and time, ignoring the constraint condition, and allocating the work selected based on the command to the selected resource A compulsory allocation step for updating the initial production plan as a provisional production plan, the resources for allocating the work for which the command has been performed, Causing the computer to execute a constraint violation resolving step of allocating the work to the resource and updating the provisional production plan while maintaining an order related to the assignment date and time of the work assigned to each resource of the production plan. It is for the purpose.

  According to this, forcible correction is performed based on the assigned resource of each operation and the assigned date / time command in the initial production plan with respect to the initial production plan from the person in charge of planning or the host system. Here, even if the compulsory correction based on the instruction includes a constraint violation, the initial production plan is compulsorily corrected and a provisional production plan is created. Then, it is possible to create a more optimal production plan by updating the provisional production plan so as to eliminate the constraint violation while respecting the command from the person in charge of planning or the host system.

  In addition, the constraint violation resolving step extracts, for each order, work that does not have unassigned work upstream from unassigned work of the order as candidate work, and creates a next assignment candidate work list From the candidate work list extraction step, from the next assignment candidate work list, the highest priority work extraction step for extracting the work with the earliest start date and time assigned in the provisional production plan, and the work for which the extraction has been performed, It is preferable to include a work assignment step for assigning resources assigned in the provisional production plan at the earliest date and time satisfying the constraint condition.

According to this, since the process can be executed at high speed based on the production plan creation procedure by the priority method, it becomes possible to quickly eliminate the violation of the constraint condition of the provisional production plan.
Here, the unassigned work means a work that has not yet been assigned a resource and date and time in the course of creating a production plan. The upstream work means a work that needs to precede a certain work in time. In addition, the priority method is a method in which the priority is evaluated with respect to the assignment candidate work, and the procedure of selecting one work with the highest priority and performing the assignment is repeated.

  The program according to the present invention includes a removable recording medium such as a CD-ROM (Compact Disc Read Only Memory), FD (Floppy (registered trademark) Disk), and MO (Magneto-Optic), and a fixed recording medium such as a hard disk. In addition to being able to be recorded and distributed, it can be distributed via a communication network such as the Internet by wired or wireless telecommunication means.

  Hereinafter, the best mode for carrying out a production plan creation method and a program according to the present invention will be described based on a specific example with reference to the drawings.

The procedure of the production plan creation method according to the present embodiment will be described with reference to FIG. FIG. 1 is a flowchart illustrating the processing procedure of the production plan creation method according to the present embodiment.
The process of the production plan creation method according to the present embodiment described below can be read and executed by the CPU as a program in the computer as well. Further, this program can be installed in various computer storage devices by recording it in a removable storage medium such as a CD-ROM, FD, or MO.

As shown in FIG. 1, first, each data is loaded from the auxiliary storage device into the memory by data reading (step S1).
Here, the data to be loaded is roughly classified into master data with relatively little change and data updated daily, and data used in the production plan creation method according to the present embodiment will be described below. .

  First, the contents of the master data will be described based on Tables 1 to 5 and FIG. Table 1 is a process list. Table 2 is a process relationship table. Table 3 is a resource list. Table 4 is a process resource time table. Table 5 is a list of setup change condition times. FIG. 13 is a process graph. FIG. 13 is obtained by integrating the records shown in Table 2.

  As shown in Table 1 and FIG. 13, in this example, three steps of process codes A1 to A3 as a process until the product A is manufactured from the material A, and a process until the product B is manufactured from the material B are processes. There are three steps as codes B1 to B3.

  Table 1 and the connection relationship of each process shown in FIG. 13, that is, the temporal prior and subsequent relationships are as shown in Table 2.

  As shown in Table 3, there are three types of resources 1 to 3. In addition, each resource shown in Table 3 shall always operate.

  Here, the resources and the time occupied in each process of Table 1 are as shown in Table 4.

  Table 5 shows the conditions and required time when a setup change occurs when the type of work is switched on a specific resource. In Table 5, the resource 1 is specified to have no setup change if the process code of the previous work and the post-operation is the same, and a setup change of 1 hour occurs if they are different. For other resources, no setup changes will occur.

  Next, in addition to the above master data, the contents of data updated daily will be described based on Table 6. Table 6 is an order list.

  There is an order list as data updated daily. As shown in Table 6, in this example, the type and delivery date of the ordered product are set in the order list.

  When the data described above is read, data generation and related settings are performed (step S2). Specifically, a process relationship table is assigned from the product code of each order, and a series of operations necessary for manufacturing the product is generated. For example, in the case of the order L1, since the process A1, the process A2, and the process A3 are necessary to manufacture the product A from the material A, operations corresponding to the processes, L1A1, L1A2, and L1A3 are generated. Then, a work list shown in Table 7 is generated.

  Further, for each work, a link between the preceding work (upstream work) and the subsequent work (downstream work) and a corresponding record in the process resource time table are generated.

Then, an initial production plan is created (step S3).
In the present embodiment, a case where an initial production plan is created by a priority method will be described. Here, the priority method is a method in which the priority is evaluated with respect to the assignment candidate work, and the procedure of selecting one work with the highest priority and performing the assignment is repeated. Further, in the present embodiment, the forward method, that is, a method in which each order is assigned from upstream work, and each work is assigned as early as possible (unless the constraint is violated). Create an initial production plan.

  In the following, the procedure of the initial production plan creation process will be described in more detail with reference to FIG. FIG. 2 is a flowchart illustrating the procedure of the initial production plan creation process.

First, a next assignment candidate work list is generated (step S301). Specifically, for each order, the most upstream work among the unallocated work is added to the list.
If the next allocation candidate work list is empty (step S302: NO), the initial production plan creation process is terminated.

  On the other hand, if the next assignment candidate work list is not empty (step S302: YES), the zc highest priority work is extracted (step S303). Specifically, the priority is calculated for each work in the next assignment candidate work list, and the work having the highest priority is extracted as the highest priority work. When there are a plurality of candidate resources for the work, the priority is calculated for each combination with the resource, and the combination of the work and the resource having the highest priority is extracted.

  Here, based on FIG. 3, the procedure of the process of extracting the highest priority work will be described in more detail. FIG. 3 is a flowchart for explaining the procedure for extracting the highest priority work.

First, the Best priority is set to 0 (step S30301).
Then, a priority is calculated for each combination of each allocation candidate task (loop R1) and each candidate resource (loop R2) (step S30302).
In the present embodiment, the priority is calculated based on the following criteria for each allocation candidate task and each candidate resource combination.
(1) Priority is given to the earliest possible date and time of work assignment (2) If (1) is the same, priority is given to those that have a short setup change time (3) If the process up to (2) is the same, the fault of the process is ranked higher Priority is given to (4) (3) if the same is given priority Priority is given to the earlier delivery date of order (5) If (4) is the same, random

Next, it is determined whether or not the calculated priority is higher than the Best priority (step S30303).
If the calculated priority is higher than the Best priority (step S30303: YES), the best priority is updated to the calculated priority (step S30304), and the assignment candidate work is updated as the highest priority work. (Step S30305). On the other hand, when the calculated priority is equal to or lower than the Best priority (step S30303: NO), the process is repeated for the next combination of allocation candidate work (loop R1) and candidate resource (loop R2).

  As described above, the highest priority work is extracted, and work assignment is performed as shown in FIG. 2 (step S304). Specifically, the highest priority work extracted in step S303 is actually allocated.

  Here, based on FIG. 4, the procedure of the work assignment process will be described in more detail. FIG. 4 is a flowchart illustrating the procedure of work assignment processing.

First, a reference date and time is calculated (step S30401). Specifically, the date and time that has passed by the time limit for the corresponding inter-process is calculated from the end date and time of the upstream work of the work to be assigned, and is used as the reference date and time.
Then, the available time is searched (step S30402). Specifically, for the candidate resource, the first available time after the reference date and time is searched from the available time series data (always operating in the present embodiment).
Next, it is determined whether the assignment is possible (step S30403). Specifically, as a result of the search, if the width of the available time found is longer than the time required for the work, it is determined that the assignment is possible.
As described above, if it is determined that allocation is possible (step S30403: YES), allocation is executed (step S30405). Specifically, the period from the start date / time of the found available time to the end of the required time for the work is removed from the available time of the resource. Then, the start date and time and the end date and time of the work are recorded, and the process ends.
On the other hand, if it is determined that the assignment is impossible (step S30403: NO), the reference date and time are updated to the end date and time of the found available time (step S30404), and the process returns to step S30402.

  As described above, work assignment is performed, and the next assignment candidate work list is updated as shown in FIG. 2 (step S305). Specifically, the work assigned in step S304 is removed from the next assignment candidate work list, and the downstream work is added to the next assignment candidate work list.

An example of the order Gantt chart and resource Gantt chart of the initial production plan created by the above procedure is shown in FIG. FIG. 5 is a Gantt chart showing an example of the initial production plan, where (a) is an order Gantt chart and (b) is a resource Gantt chart.
In addition, the downward triangle mark (▼) in the order Gantt chart is the delivery date of each order. Arrows in the resource Gantt chart represent temporal context constraints between operations. For example, an arrow that originates from the end of work L1A1 (right side of the rectangle) and reaches the start of work L1A2 (left side of the rectangle) means that work L1A2 can be started only after work L1A1 ends. In addition, a rectangle with a vertical line in the resource Gantt chart represents the setup change time between operations.

As can be seen from the order Gantt chart of FIG. 5A, the order L8 is delayed in delivery date. The work L8B3 is started immediately after the inter-process time of 30 minutes has elapsed since the work L8B2 is completed, but at that time, the delivery time for the order L8 has already reached 23:00.
This is directly because the completion time of the work L8B2 is late, but if it goes back further, it is a problem that the start of L2B2 is late, and moreover, fundamentally, the start of L2B1 is late. It is. That is, since the group of work (L1A1 to L7A1) that does not require setup change in the resource 1 is too large in the planned time zone, the start of the resource 3 is delayed and a large waiting time occurs in the resource 3. Yes.

Therefore, as shown in FIG. 1, the initial production plan created as described above is acquired (loop R0: initial production plan acquisition step), a forced correction command is issued (step S4: forced correction command step), and forced allocation is performed. (Step S5: compulsory allocation step), and the allocation status is recorded (step S6). Specifically, in the forced correction command, there are a case where the operator moves with a mouse or the like on the Gantt chart, and a case where the command is issued from the host system. In the forced allocation, the initial production plan is forcibly allocated on the basis of the forced correction command while ignoring the time constraints with upstream / downstream operations and the resource load. In the allocation status record, the start date and time in the production plan of each operation updated by the forced allocation and the allocated resources are recorded as a provisional production plan.
In this embodiment, the operator wants to process L2B1 and L4B1 before L5A1 and L7A1 in resource 1, and moves L2B1 and L4B1 to an earlier time on the resource Gantt chart. As a result, the allowable addition of resource 1 is exceeded, but it is forcibly allocated. As described above, the initial production plan is updated as a provisional production plan as shown in FIG. FIG. 6 is a Gantt chart showing an example of a provisional production plan, where (a) is an order Gantt chart and (b) is a resource Gantt chart.
Further, the operator moves L5A1 and L7A1 to a later time. As a result, the allowable addition of resource 1 is exceeded, but it is forcibly allocated. As described above, the provisional production plan as shown in FIG. 7 is further updated. FIG. 7 is a Gantt chart showing an example of a provisional production plan, where (a) is an order Gantt chart and (b) is a resource Gantt chart.

Next, as shown in FIG. 1, the constraint violation is eliminated (step S7: constraint violation elimination step). Specifically, the production plan is created while taking into account the forced correction command in step S4.
That is, in the present embodiment, the provisional production plan shown in FIG. 7 cannot be executed because the resource load exceeds the allowable amount. Therefore, the constraint violation is resolved and an executable production plan is created.

Here, based on FIG. 8, the procedure of the constraint violation elimination process will be described in more detail. FIG. 8 is a flowchart for explaining the procedure for eliminating the constraint violation.
The procedure for resolving the constraint violation is basically assigned by the priority method and the forward method in the same manner as the procedure for creating the initial plan shown in FIG. 2 described above. First, an operation with the earliest start date recorded in the provisional production plan is extracted from the candidate operation list.

First, a next assignment candidate work list is generated (step S701: next assignment candidate work list extraction step). Specifically, for each order, the most upstream work among the unallocated work is added to the list.
If the next allocation candidate task list is empty (step S702: NO), the constraint violation elimination process is terminated.

  On the other hand, if the next allocation candidate task list is not empty (step S702: YES), the highest priority task for eliminating the constraint violation is extracted (step S703: highest priority task extraction step). Specifically, for each work in the next allocation candidate work list, the start date and time recorded in the provisional production plan is read out, and the work with the earliest work is extracted as the highest priority work for solving the constraint violation.

  Here, based on FIG. 9, the procedure of the process for extracting the highest priority work for eliminating the constraint violation will be described in more detail. FIG. 9 is a flowchart illustrating the processing procedure for extracting the highest priority work for constraint violation resolution.

First, the Best start date and time is set as the production plan period end date and time (step S70301).
Then, for each assignment candidate work (loop R3), the recorded start date and time are read out, and it is determined whether or not the recorded start date and time is earlier than the Best start date and time (step S70302).
If the recorded start date / time is earlier than the Best start date / time (step S7032: YES), the best start date / time is updated to the recorded start date / time (step S7033), and the assignment candidate work is given the highest priority for constraint violation resolution. The work is updated (step S70304). On the other hand, when the recorded start date and time is after the Best start date and time (step S70302: NO), the process is repeated for the next assignment candidate work (loop R3).

  As described above, the constraint violation resolving highest priority work is extracted, and work assignment is performed as shown in FIG. 8 (step S704: work assignment step). Specifically, the constraint violation resolving highest priority work extracted in step S703 is actually allocated. Note that the work assignment procedure is the same as the work assignment process (see step S304 in FIG. 2 and FIG. 4) in the initial plan creation process described in step S3 above. Omitted.

  When the work assignment is performed, the next assignment candidate work list is updated as shown in FIG. 8 (step S705). Specifically, the work assigned in step S704 is removed from the next assignment candidate work list, and the downstream work is added to the next assignment candidate work list.

  FIG. 10 shows an example of an order Gantt chart and a resource Gantt chart of the provisional production plan updated by eliminating the constraint violations by the above procedure. FIG. 10 is a Gantt chart showing an example of the updated provisional production plan, (a) is an order Gantt chart, and (b) is a resource Gantt chart.

As shown in FIG. 10, it can be seen that the result of the production plan in which the constraint violation is resolved is obtained in each resource in the order specified by the operator.
However, according to the Gantt chart shown in FIG. 10, the delivery date is still delayed. That is, according to the Gantt chart shown in FIG. 10, the work allocation to the resource 3 has been improved as expected, but the processing of the resource 1 has not kept up with the delivery date. Therefore, since the resource 1 has undergone many setup changes and is operating at full capacity, the operator has no choice but to reduce the number of setup changes. Specifically, L2B3 and L4B3, L5A3 and L7A3 are processed continuously It can be judged that it is good.

Therefore, as shown in FIG. 1, since the production plan is unsatisfactory, the provisional production plan updated as described above is acquired as an initial production plan (loop R0: initial production plan acquisition step), and a forced correction command is issued. At the same time (step S4: forced correction command step), forced assignment is performed (step S5: forced assignment step), and the assignment status is recorded (step S6).
In the present embodiment, the operator wants to continuously process L2B3 and L4B3, L5A3 and L7A3 in resource 1, and moves L4B3 immediately after L2B3. As a result, the allowable addition of resource 1 is exceeded, but it is forcibly allocated. As described above, the initial production plan is updated as a provisional production plan as shown in FIG. FIG. 11 is a Gantt chart showing an example of a provisional production plan, where (a) is an order Gantt chart and (b) is a resource Gantt chart.

  Next, the constraint violation elimination process is performed again as described above (step S7: constraint violation elimination step), and a provisional production plan as shown in FIG. 12 is obtained. FIG. 12 is a Gantt chart showing an example of the updated provisional production plan, (a) is an order Gantt chart, and (b) is a resource Gantt chart.

  As shown in FIG. 11, since the number of setup changes in resource 1 is reduced, L6B3 and L8B3 are processed in resource 1 at an earlier time, and the delivery delay is eliminated.

  Then, as shown in FIG. 1, there is no dissatisfaction with the production plan (loop R0), the result of the provisional production plan in step S7 is saved as the finally obtained production plan (step S8), and the process is terminated. .

  As described above, according to the production plan creation method and program of this embodiment, based on the assigned resources and the assigned date and time of each work in the initial production plan for the initial production plan from the person in charge of the plan creation or the host system ( Step S4 in FIG. 1 is forcibly corrected (step S5 in FIG. 1). Here, even if the compulsory correction based on the command includes a constraint violation, the initial production plan is compulsorily corrected and a provisional production plan is created (step S6 in FIG. 1). Then, while respecting the command from the person in charge of the plan creation or the host system, etc., the provisional production plan is updated to eliminate the constraint violation (step S7 in FIG. 1), thereby creating a more optimal production plan. It becomes possible.

  Further, since the process can be executed at high speed based on the production plan creation procedure by the priority method (step S7 in FIG. 1), it is possible to quickly eliminate the violation of the constraint conditions of the provisional production plan. Become.

  The preferred embodiments of the present invention have been described above. However, the present invention is not limited to the above-described embodiments, and various modifications can be made as long as they are described in the claims.

  In the above-described embodiment, the work assignment for the production plan is performed by the forward method and the priority method algorithm, but is not limited thereto, and may be performed by another algorithm.

It is the flowchart explaining the procedure of the process of the production plan preparation method which concerns on this Embodiment. It is the flowchart explaining the procedure of the process of preparation of an initial production plan. It is the flowchart explaining the procedure of the process of highest priority work extraction. It is the flowchart explaining the procedure of the process of work allocation. It is a Gantt chart showing an example of an initial production plan, (a) is an order Gantt chart, and (b) is a resource Gantt chart. It is a Gantt chart showing an example of a provisional production plan, (a) is an order Gantt chart, and (b) is a resource Gantt chart. It is a Gantt chart showing an example of a provisional production plan, (a) is an order Gantt chart, and (b) is a resource Gantt chart. It is the flowchart explaining the procedure of the process of a constraint violation cancellation. It is the flowchart explaining the procedure of the process of extraction of the highest priority work for constraint violation cancellation. It is the Gantt chart which showed an example of the updated provisional production plan, (a) is an order Gantt chart, (b) is a resource Gantt chart. It is a Gantt chart showing an example of a provisional production plan, (a) is an order Gantt chart, and (b) is a resource Gantt chart. It is a Gantt chart showing an example of a provisional production plan, (a) is an order Gantt chart, and (b) is a resource Gantt chart. It is a process graph.

Explanation of symbols

R0 Initial production plan acquisition step S4 Forced correction command step S5 Forced assignment step S7 Restriction violation elimination step S701 Next assignment candidate work list extraction step S703 Top priority work extraction step S704 Work assignment step

Claims (4)

A production plan creation method that creates a production plan by allocating work, which is a combination of multiple orders and processes necessary to manufacture products of the order, to resources selected from multiple resources while complying with the constraints. Because
An initial production plan obtaining step for obtaining an initial production plan in which the constraint condition is not satisfied;
A forced correction command step for selecting one or a plurality of operations for the initial production plan and issuing a command for forced correction of resources and allocation date and time;
Ignoring the constraint condition, allocating the work selected based on the command to the selected resource, and forcing the initial production plan as a provisional production plan; and
Assigning the work to the resource while maintaining the order for the resource to which the work for which the command has been performed is assigned and the assignment date and time of the work assigned for each resource of the provisional production plan; Constraint violation elimination step to update production plan,
A production plan creation method characterized by comprising: The constraint violation elimination step includes
For each order, a next assignment candidate work list extraction step that extracts a work that does not have an unassigned work upstream from the unassigned work of the order as a candidate work and creates a next assignment candidate work list;
From the next assignment candidate work list, the highest priority work extraction step for extracting the work with the earliest start date and time assigned in the provisional production plan;
For the work that has been extracted, as a resource for allocating resources allocated in the provisional production plan, a work allocation step that allocates the earliest date and time that satisfies the constraint conditions;
The production plan creation method according to claim 1, wherein: To allow a computer to create a production plan by allocating work, which is a combination of multiple orders and processes necessary to manufacture products of the order, to a resource selected from multiple resources while maintaining the constraints The program of
An initial production plan obtaining step for obtaining an initial production plan in which the constraint condition is not satisfied;
A forced correction command step for selecting one or a plurality of operations for the initial production plan and issuing a command for forced correction of resources and allocation date and time;
Ignoring the constraint condition, allocating the work selected based on the command to the selected resource, and forcing the initial production plan as a provisional production plan; and
Assigning the work to the resource while maintaining the order for the resource to which the work for which the command has been performed is assigned and the assignment date and time of the work assigned for each resource of the provisional production plan; Constraint violation elimination step to update production plan,
A program that causes a computer to execute. The constraint violation elimination step includes
For each order, a next assignment candidate work list extraction step that extracts a work that does not have an unassigned work upstream from the unassigned work of the order as a candidate work and creates a next assignment candidate work list;
From the next assignment candidate work list, the highest priority work extraction step for extracting the work with the earliest start date and time assigned in the provisional production plan;
For the work that has been extracted, as a resource for allocating resources allocated in the provisional production plan, a work allocation step that allocates the earliest date and time that satisfies the constraint conditions;
The program according to claim 3, further comprising:

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