JPH10263995A - Production scheduling system - Google Patents

Abstract

PROBLEM TO BE SOLVED: To form an effective production schedule as a whole by repeatedly correcting a schedule formed from a local judgment based on a dispatching rule in consideration of the whole schedule to improve the final process completion time of each product. SOLUTION: Only the process possibly contributing to the improvement of the final process completion time is detected to make computation efficient and to increase the improvement effect (S7). Whether a schedule is improved as a whole by a change of the processing sequence or not is judged on the detected process (S8). When it is judged that the whole schedule is improved (S9), the changed schedule is used as the new schedule (S10), then the study is returned to the step S5, and whether there is no room for improvement or not is checked.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a production scheduling method for efficiently producing various types of products in a production system comprising a plurality of processes and producing a plurality of types of products. is there.

[0002]

2. Description of the Related Art In an actual production system, since the number of processes and the number of products are large, an enormous number of combinations exist in the production schedule. Therefore, it is almost impossible to search for these combinations to find an optimal schedule within a realistic time. For this reason, in the production scheduling method generally performed conventionally, when there are a plurality of products that can be processed by each processing device, a product to be processed is selected by a dispatching rule based on a certain rule. You are creating a schedule.

Various types of dispatching rules have been proposed in accordance with the characteristics of production systems and production requirements. A typical example is a first-in, first-out (FIFO) system that processes products that arrive early.
FirstOut) method, a method for processing products in the order of priority determined in advance for each product such as an express processing product, a method for processing products with a long (short) processing time first, and many (less) processes remaining until processing is completed. ) There are a method of processing products first, and a method of preferentially processing products that have little room for delivery.
Further, a method of using these dispatching rules in combination or dynamically changing the priority according to the progress of a product has been proposed. For example, the reference time of each process is obtained in advance for each product, and according to the actual progress, the priority of a product having a large delay from the reference time is set to be high, so that the variation in the processing for each product is reduced. Have been proposed.

FIG. 5 shows an example of a conventional production scheduling method. Next, referring to FIG. 5, the most representative dispatching rule, the first-in first-out method (Fi
A production schedule creation method using rst in first out) will be described. In the figure, L1 to L5 are products,
M1 to M5 represent processing devices for processing these products, respectively, and here, the products L1 to L5 are scheduling target products. FIG. 5A shows the initial state of the scheduling target portion. The product L1 is waiting for processing by the processing device M3, the product L2 is being processed by the processing device M2, and the product L3 is being processed by the processing device M3. . . And so on. FIG. 5B shows a processing device in each process after each product. For example, a product L1 is a processing device M1, M3, M4, M6.
Are processed in this order. Note that the process shown in FIG. 5B is a scheduling target process of each product.

FIG. 5C shows an example of a production schedule created by a FIFO (first in first out) method. From the initial state, the processing of the product L3 in the processing device M3 ends first, and the processing device M3 becomes usable. At this point, the products L1 and L2 are candidates for products to be processed next by the processing device M3. The product L1 is already waiting for processing by the processing device M3, and the product L2 is still being processed by the processing device M2. Therefore, the product L1 is allocated to the processing device M3 according to the FIFO rule. The product L3
Since the processing device M4, which is the next processing device, is still processing the product L4, the product L3 enters a processing waiting state. next,
The processing of the product L5 in the processing device M5 ends. At this point, the next processing device M7 of the product L5 is in a usable state. The product candidate to be processed next by the processing device M7 is the product L
3, L5, since the product L3 is still being processed by the processing device M3, the product L5 is allocated to the processing device M7 according to the FIFO rule.

[0006] Next, the processing of the product L2 in the processing device M2 ends. The product L1 has already been assigned to the processing device M3 next to L2, and the product L2 is in a process waiting state because it is under processing. Next, the processing of the product L4 in the processing device M4 ends. At this point, the processing device M4 becomes available, and the product L3 that has been waiting for processing is assigned to the processing device M4. Further, since the product L4 is in a usable state for the next processing device M6, the processing device M6 is
Assigned to Hereinafter, by the same procedure, FIG.
Is created.

[0007]

By the way, as mentioned above, many dispatching rules have been proposed and actually used. However, each of these dispatching rules determines which product process is to be assigned next to the available processing equipment, and takes into account the processing of these products in further steps. Not. Therefore, there is no guarantee that the selection in the next step is always effective in the subsequent step. As a result of preferential processing in the next step, the delay is increased in the subsequent step, and as a result, the final processing completion time is set. Sometimes it will be delayed. This is because, when the number of processes and the number of products increase, many competitions between products in each processing apparatus occur, and these causal relationships are complicatedly intertwined. Therefore, an object of the present invention is to provide an efficient production scheduling method from the global viewpoint of the entire schedule as well as the accumulation of local judgments in the next process as described above.

[0008]

According to the production scheduling method of the present invention, when performing production in accordance with a production order and a process chart showing production processing, the production processing order in each processing apparatus is determined. In a production scheduling method in which a production schedule is created by calculating a processing time of each processing step of a product, a production schedule is created by selecting a product to be processed in each processing device according to a predetermined dispatching rule. A first means, a second means for detecting a process which may improve the processing completion time of each product with respect to the production schedule created by the first means, and 3. Determine whether changing the processing order improves the overall production schedule
Means, and if it is determined to be improved, a fourth means for setting a schedule in which the processing order has been changed as a new production schedule, and a production schedule which is successively improved by repeating the above operations And a fifth means.

In a production scheduling method according to a second aspect of the present invention, in the first aspect of the present invention, the second means is configured to execute processing in a processing sequence corresponding to a critical path from an initial state to completion of processing of the product. A process in which the processing time is improved by changing the order is detected.

According to a third aspect of the present invention, in the production scheduling method according to the first or second aspect, even if the third means changes the processing order, the order is changed between the product and the process. By confirming that the processing completion time of the product is not affected, it is determined that the overall schedule is improved.

According to a fourth aspect of the present invention, in the production scheduling method according to the first or second aspect, after the third means changes a processing order of the product in the process,
Subsequent schedules are created according to the dispatching rules, and by comparing the entire schedule before and after the change, it is determined whether or not the schedule can be improved. If the schedule is determined to be improved, the schedule after the change is newly created. Production schedule.

According to a fifth aspect of the present invention, there is provided the production scheduling method according to any one of the first to fourth aspects,
This is for giving a work instruction to the processing device in the usable state as to which product should be processed next.

[0013]

An embodiment of the present invention will be described below with reference to the drawings. Embodiment 1 FIG. FIG. 1 is a diagram showing a processing procedure of the production scheduling method according to the present invention. Next, this processing procedure will be described in detail below. In FIG. 1, first, a target range of production scheduling is set. That is, products to be scheduled and up to which process of these products are to be set are set. In addition, you may set by time (1 day etc.) instead of a process. Of course, the whole production system, that is, the final process of all products may be targeted (step S1).

Next, the current state (current step, processing or waiting state, processing or waiting start time) of each product to be scheduled and the processing device used by these products and recognition of subsequent steps. Is performed (step S2). Note that, also in this embodiment, the initial state is, for example, the same as that in FIG. That is, the product L1 is waiting for processing by the processing device M3, and the product L2 is being processed by the processing device M2. . . And so on. Next, scheduling initial setting is performed with the current time as an initial time and the current state as an initial state (step S3). That is, the state at the initial time in the production schedule of FIG. 3A is the initial setting.

Under the initial state set above, a production schedule of a target range is first created using dispatching rules, and this is set as an initial schedule (step S4). As a result, a production schedule (initial schedule) as shown in FIG. Details will be described later with reference to FIG. Next, for the schedule created above, the processing completion time up to the target process (or the final process) of each product is checked, and the completion time is further advanced in consideration of the productivity and delivery time of the line. Whether there is a product to be improved as described above (step S
5). As a result, if there is no product requiring improvement, the created production schedule is determined to be satisfactory, and the process ends. In the example of FIG. 3A, the products L1, L2,
L3 has a processing wait time, and there is room for improvement.

If there is a product to be improved, a product to be improved is selected based on some criterion such as a product having a particularly large delay (step S6). Note that the above steps S5 and S6
May be automatically performed by a computer according to some rules, or may be determined by displaying schedule results. Alternatively, the subsequent processing may be performed on all products. Here, it is assumed that the product L1 is selected as the product having the longest processing waiting time.

Next, the processing completion time is improved for the product to be improved, but not every process of the product contributes to the improvement of the final processing completion time. Therefore, even if blindly attempting to change the use order of the processing apparatus in all the steps, the calculation time is increased and the effect of the improvement is small. Therefore, by detecting only the steps that may contribute to the improvement of the final processing completion time, the calculation can be made more efficient and the improvement effect can be enhanced (step S7). The processing time in each step is fixed, and is the minimum required time. Therefore, what is to be improved is the waiting time in the processing device.
Therefore, by focusing only on the process in which the processing waiting time has occurred, it is possible to detect a process that may improve the final processing completion time.

Therefore, as an example, by using the critical path in the graphical representation of the schedule, it is possible to efficiently detect a process that may improve the final processing completion time. FIG.
3A is a graphical representation of the production schedule (initial schedule) of FIG. The arrows in the figure indicate the order of processing, for example, the product L1 is the processing device M1, M3, M4, M
6 are processed in order. In addition, thin arrows between products indicate the order in which the processing devices are used. For example, product L
The thin arrow (which overlaps with the thick arrow in the figure) from the processing apparatus M3 of the third processing apparatus to the processing apparatus M3 of the product L1 is the processing apparatus 3
Indicates that processing is performed in the order of products L3 and L1.

A thick line in the graph indicates a critical path relating to the completion of the processing of the product L1 (the processing of the processing device M6). That is, from the initial state, the product L
1 shows a processing sequence that determines the processing completion time of the first processing. In this case, the processing completion time of the product L1 is set to the processing end time of the processing device M3 of the product L3.
3, the processing device M3, M5 of the product L2,
This shows that the processing time in M6 and the processing time in the processing device M6 of the product L1 are added. Therefore, in order to improve the processing completion time of the product L1,
It can be seen that any of the steps included in these critical paths needs to be improved. In the example of FIG. 3A, there is a possibility of improvement in changing the use order of the processing device M6 (from the order of the products L2 and L1 to the order of the products L1 and L2) or changing the use order of the processing device M3. Change (product L1, L2
From the order of the products L2, L1). Therefore, these are detected as steps that can be improved.

Next, it is determined whether or not the schedule as a whole can be improved by changing the processing order for the process detected above (step S8). Various methods can be considered for this determination.For example, for example, when the processing completion time of at least one product is improved by changing the order and the processing completion time of another product is not affected, Obviously, there is a method of determining that the schedule is improved as a whole. Therefore, when judging by this method, in the example of FIG. 3A, when the processing order is changed in the processing device M6, the processing completion time of the product L1 is improved. Since the completion time is delayed, it is not determined in this case that improvement is made as a whole.

Further, in order to know how the overall schedule is changed by the order change, the dispatching rule is again used based on the changed order, and the same procedure as that used when the initial schedule is created in step S4. , Create a schedule. Whether or not the resulting production schedule is improved compared to the original schedule can be determined from various viewpoints depending on the purpose required of the production system. For example, when the delivery date is emphasized, there may be a case where it is better to slightly delay other products that have a spare delivery date so that the product can be delivered in time.
In the example of FIG. 3A, regarding the processing device M6, even if the order is changed, the processing completion time of one of the products is delayed, so that it cannot always be determined that the schedule is improved as a whole.

Next, a change in the order of the processing device M3 will be considered. If the processing device M3 is changed to process the product L2 before processing the product L1, the processing completion time of the product L2 is clearly improved. Also, the product L1 is provided by the processing device M3.
In any case, the processing time of the processing device M4 is waiting in the next process, and
4 is not affected by the processing time. Therefore, in this case, it is determined that the schedule is improved as a whole. As described above, when it is determined that the overall schedule is improved (step S9), the changed schedule is set as a new production schedule (step S10).
Returning to step S5, it is examined whether there is room for further improvement. In the above description, steps S1 to S6
Constitutes the first unit, step S7 constitutes the second unit, step S8 constitutes the third unit, and step S8
Steps S5 to S1 constitute the fourth means.
0 constitutes a fifth means.

FIG. 3B shows an example of schedule improvement by changing the processing order in the processing device M3. Comparing the improved schedule of FIG. 3 (b) with the initial schedule of FIG. 3 (a), in the improved schedule of FIG. 3 (b), the processing completion time is improved for both products L1 and L2. You can see that it is. FIG. 4B shows a graph expression and a critical path for the improved schedule. If the above procedure is repeated and there is finally no product to be improved, a satisfactory schedule has been created as a whole, and the process ends.

Next, referring to FIG. 2, step S4 in FIG.
A method of creating an initial schedule according to the dispatching rule in the first embodiment will be described. First, the initial time is set as the processing time in the scheduling process (step S11). Next, among the products being processed at the set processing time, a product that finishes the process of the process earliest is obtained (step S12). Then, the processing end time of the process of the product is set as a new processing time (step S13). At this time, it is determined whether or not the processing of all the processes to be scheduled for the product has been completed (step S14). If the processing steps still remain, it is determined whether or not the processing device for the next step of the product is usable (step S15). If it is not usable, the processing device is put into a processing waiting state for the product (step S1).
6). If the processing device is in a usable state, it is determined by the dispatching rule whether the product is selected as the next processing product of the processing device (step S17). The process starts (step S18). If it is not selected, the processing unit is set to a processing waiting state (step S16).

Next, the processing apparatus for the process of the product is made usable, and the product to be processed next is selected according to the dispatching rules (step S20). If it is determined in step S14 that all the processes to be scheduled have been completed for the product, it is determined whether the processing has been completed for all the products to be scheduled (step S19). If the processing of all products is completed, the initial schedule has been created, and the processing ends. If there is a product that has not been completed, the process of step S20 is performed.

Next, in step S20, it is determined whether there is a product selected by the dispatching rule (step S21). If so, it is determined whether the selected product is in a processing waiting state of the processing apparatus (step S21). Step S2
2). If it is in the processing waiting state, the processing of the selected product in the processing device is started (step S23). If there is no product selected by the dispatching rule in step S21, the process returns to step S12 and repeats the above processing. In step S22, if the selected product is not yet in the processing waiting state of the processing apparatus, the process returns to step S12 and repeats the above processing. By the above procedure, an initial schedule based on the dispatching rules is created.

Note that the above procedure is not limited to creating the initial schedule, but also when creating the production schedule after the order change, by setting the processing start time of the order change as the initial time in step S11. The same can be applied. As described above, according to the production scheduling method of the present embodiment, unlike the conventional method in which only the next process is considered and a schedule is created, the entire schedule result is reviewed and room for improvement is examined.
An efficient production schedule can be created as a whole.

In addition, according to the production schedule created by the above-described procedure, by giving a work instruction to each processing device at the time of actual line operation, efficient operation of the entire line can be performed. For example, in the example of FIG. 5 described above, in the initial state of FIG.
When the user issues a work instruction as to which of the product L1 and the product L2 should be processed first after the processing of the product L3, the product L1 is allocated first in the conventional first-in first-out method.
However, in the method according to the present invention, a production schedule as shown in FIG. 3 can be created in consideration of further steps. As a result, by allocating the product L2 first, more efficient line operation can be performed as a whole.

[0029]

According to the production scheduling method of the present invention, the final processing completion time of each product is improved in consideration of the entire schedule with respect to the schedule created by the local judgment based on the dispatching rule. There is an effect that an efficient production schedule can be created as a whole by repeating the correction for the above.

Further, according to the production scheduling method of the present invention, according to the efficient production schedule,
By giving a work instruction to each processing device during the actual operation of the production line, there is an effect that the entire line can be efficiently operated.

[Brief description of the drawings]

FIG. 1 is a flowchart showing a processing procedure of a production scheduling method according to the present invention.

FIG. 2 is a flowchart showing a processing procedure for creating an initial schedule based on a dispatching rule in the production scheduling method according to the present invention.

FIG. 3 is a diagram for explaining a graphical representation of a production schedule and a critical path.

FIG. 4 is a diagram showing an example of a production schedule created by the present invention.

FIG. 5 is a diagram for explaining a production scheduling problem to which the present invention is applied.

[Explanation of symbols]

 L1-L5 products, M1-M5 processing equipment.

Claims (5)

[Claims] When producing according to a process chart showing a production order and a production process, a production schedule is determined by determining a processing order of products in each processing apparatus and calculating a processing time of each processing step of each product. In the production scheduling method to be created, a first means for creating a production schedule by selecting a product to be processed in each processing apparatus in accordance with a dispatching rule given in advance, and a production schedule created by the first means A second means for detecting a process that may improve the processing completion time of each product with respect to the schedule, and whether the overall production schedule is improved by changing the processing order of the product in the process. A third means for judging whether or not the schedule has been changed if the processing order has been changed; The fourth means and production scheduling system, characterized in that a fifth means for improving the production schedule sequential By repeating the above operation for a new production schedule. 2. The method according to claim 1, wherein the second unit detects a process in which a processing time is improved by changing a processing order in a processing sequence corresponding to a critical path from an initial state to completion of processing of the product. The production scheduling method according to claim 1, wherein: 3. The method according to claim 1, wherein the third unit confirms that even if the processing order is changed, the processing completion time of the product and another product whose order is changed in the process is not affected. 3. The production scheduling method according to claim 1, wherein it is determined that the schedule is improved. 4. The third means, after changing a processing order of the product in the process, creates a subsequent schedule according to a dispatching rule, and compares the entire schedule before and after the change, The production scheduling method according to claim 1, wherein it is determined whether or not the schedule is improved, and if it is determined that the schedule is improved, the changed schedule is set as a new production schedule. 5. The production scheduling method according to claim 1, wherein a work instruction as to which product is to be processed next is given to the processing device in an available state.