JPS6361138B2 - - Google Patents

Description

[Detailed description of the invention]

[Technical field] The present invention relates to a logistics control method, particularly in production progress management, a merging control method that allows easy processing in subsequent processes in a logistics route where many branches or mergings occur between the initial stage process and the final stage. It is related to. [Prior Art] In various processing or assembly processes in a factory, it is necessary to accurately manage work in progress at each process, and it is known that such physical distribution management has a large impact on production efficiency. For example, in recent years, a logistics control method known as the Kanban system in the automobile industry is useful for optimizing in-process inventory within a factory and simplifying its management. As is well known, the above-mentioned kanban system aims to reduce the in-process inventory in the factory by requesting the delivery of the required amount of products or parts from the post-production process to the pre-production process in order. It is extremely useful in production and in production processes where a number of process paths are increasingly integrated. However, although this type of kanban system is useful for managing required parts in subsequent processes, it does not have more detailed logistics information, so it is difficult to manage products or parts that are still in progress (hereinafter referred to as work-in-progress). There was a problem that no consideration was given to the order in which the products were supplied. Particularly, in recent years, in the mass production of a wide variety of products, work-in-progress has complex branching and merging of process routes, making it impossible to properly manage and control the process. In particular, at the merging section where multiple processes are combined and sent to the subsequent process, the order of merging becomes a big problem in order to facilitate the equipment or work in the subsequent process, and the processing at this juncture makes it difficult for the subsequent process to proceed. The leveling of work is achieved, and even in high-mix mass production or high-mix low-volume mass production, the effect of such leveling can significantly improve the overall production efficiency. In general, in a multi-product mass production process, production progress management must be performed by combining different parts on a single processing or assembly line, and the combination of such different parts has changed in recent years due to the diversification of consumer tastes. There may be hundreds of types of processing or assembly depending on the type, and the processing time or difficulty in each process differs depending on the type. If the flow is stopped in the process, or if the processes are performed in a different combination each time, the procedure changes frequently in a particular process, resulting in a similar flow stop or a decrease in efficiency. There has been a demand for optimal control of the order in which workpieces in progress are supplied to a line at a junction. For example, if we take an automobile assembly line as an example, there are cars that are easy to assemble and cars that are difficult to assemble in a particular assembly process, and by sending these at an appropriate frequency, leveling of the process is promoted and the overall production The progress balance is significantly improved, and specifically, the waiting time in each process is reduced, which often contributes to improved efficiency. These problems are noticeable on car body outfitting assembly lines, etc., and there is a big difference in assembly time between cars with many accessories and cars with few accessories, and cars that are difficult to assemble are continuously running on such assembly lines. When the assembly process is fed, the assembly process becomes saturated, and if these defects occur in each process, they will eventually cause problems that stop the entire line. It is necessary to supply vehicles with different assembly difficulty levels at an appropriate frequency. On the other hand, there are cases where performing the same type of work continuously in other processes can significantly improve the efficiency of the process, and in such cases, it is necessary to continuously perform work in progress that has been made into a lot, that is, has the same type of post-process. In some cases, it may be necessary to do so, and it is also necessary to consider this type of rotatization at the merging section. For example, when painting a car body in the car assembly process, painting the same color can be done quickly by continuous work, but if the color of the car body changes, the paint must be replaced in the painting process each time. It is understood that the preparation requires a great deal of effort and time.
Further, paint is wasted during such setup, which significantly reduces the efficiency of the painting process. Therefore, for such a painting process, it is preferable to continuously flow unfinished works of the same color. Another example of effective rotorization is the process of drilling holes in engines, etc., and attaching and detaching the drill to a drilling machine requires a large amount of setup effort in such a process, and it is difficult to replace workpieces in progress that are to be worked with drills of the same diameter. Continuous flow is preferred to improve efficiency. Therefore, in a production line that handles a large number of parts, merging control that takes into account the above-mentioned leveling is required at each merging point, but conventionally,
There is no way to effectively carry out such control, and it has often relied on the intuition and skill of workers at each site. Processing at the merging section as described above occurs not only when predetermined workpieces in progress are merged along the normal route, but also at the merging section where defective products are corrected in each process. The quality of the products is partially checked and defective products are removed from the line, passed through a special correction line, and returned to the original line.When such sideways corrections are made, the previously orderly process is However, if the above-mentioned leveling is taken into consideration at the return junction to the line, it is possible to minimize the disturbance and perform optimal machining. [Object of the Invention] The present invention has been made in view of the above-mentioned conventional problems, and its purpose is to take into account leveling in the subsequent process at the merging section, thereby improving the overall An object of the present invention is to provide an improved logistics control method that can significantly improve production efficiency. [Structure of the Invention] In order to achieve the above object, the present invention provides a logistics control method in which workpieces in progress supplied from a plurality of pre-processes are combined into a single post-process at a confluence point and transported serially. The machining conditions, including the difficulty level of the work in the subsequent process, are displayed on each work in progress, and the machining conditions are read from each work in progress fed to the merging point, and a predetermined number of workpieces serially conveyed immediately before the merging point are read. The work difficulty level of the work in progress and the work difficulty level of the work in progress to be merged are each individually multiplied by coefficients and then added together to obtain an evaluation function, and the evaluation function is compared with at least one reference value. , determine whether or not to merge so that the work difficulty level in the subsequent process is leveled, and if the evaluation function is less than the reference value and the merge is possible, send the work in progress to the subsequent process,
On the other hand, if the evaluation function exceeds a reference value to indicate whether or not to merge, the work in progress is made to wait in the previous process. [Embodiments] Preferred embodiments of the present invention will be described below based on the drawings. FIG. 1 shows the merging work of in-process workpieces at a merging point using the physical distribution control method according to the present invention, in which the in-process workpieces W carried by the conveyor 10 from the first pre-process are It is merged with other workpieces at the merging point X and transported to the subsequent process by the same conveyor 10. On the other hand, from the workpieces in progress W carried by the conveyor 12 from the second pre-process, only those needed for the post-process of the conveyor 10 are selected and
They will be sorted and transferred to The work-in-progress W can be handled as any product, but for example, in the embodiment, a car can be assumed as the work-in-progress W, and after passing through a pre-process that differs depending on the type of car, the work-in-process W can be handled as a post-process, such as a painting process. , it is preferable to consider a confluence section for sending to the vehicle body assembly process. A roller conveyor 14 is provided to send workpieces W in progress from the conveyor 12 to a merging point Wait while facing X. Another pusher 20 is provided at this opposing position, and a desired workpiece W is pushed out from the standby position toward the merging point X and conveyed to the subsequent process by the conveyor 10. Each in-process workpiece W sent from the two preceding processes toward the confluence point X has predetermined individual machining conditions for the subsequent process displayed on a label or the like, and these individual machining conditions can be read. Therefore, label readers 22 and 24 are provided immediately before the merging point X, and are comprised of, for example, a bar code reader or a detection camera, and input these individual processing conditions to the merging control computer 26. The merging control computer 26 calculates various types of merging control according to the present invention, which will be described later.
By supplying a merging signal to the merging point X, the unfinished work W supplied to the merging point A wait signal is given to a certain gate 28 to suppress the supply of the in-process work W carried from the first pre-process to the subsequent process, thereby controlling the desired merging action at the merging point X. be done. The roller conveyor 14 is provided with a retention sensor 30 consisting of a limit switch or the like, which can notify the merge control computer 26 that the number of workpieces W retained at the merge point X exceeds a predetermined value. The physical distribution control method according to the present invention will be explained below based on FIG. In the present invention, workpieces in progress W on both conveyors 10 and 12 in FIG.
It is also possible to determine whether or not both of them can be merged at the merge point X, or it is also possible to determine whether or not only one work in progress can be merged. In the following description, an example of a control method will be described in which calculation is performed to determine whether or not workpieces in progress can be merged, which are supplied to the merge point X only via the conveyor 12 and roller conveyor 14 from the second pre-process. . FIG. 2 shows a flowchart of the first embodiment of the physical distribution control method according to the present invention. When the merging control computer 26 starts, it first determines whether or not there are workpieces in progress to be merged at the merging point X; This can be known from the data of the label reader 24, or it can be determined by a workpiece sensor provided on the stopper 18. If there is no work in progress to merge at the merging point X, normal operation of the main line, that is, the line formed by the conveyor 10, is instructed and the process returns to the next control cycle. On the other hand, if there is an in-process work at the merging point That is, the machining conditions of a predetermined number of, for example, five work-in-progress works W that were serially transported to the subsequent process immediately before the work-in-progress work currently being judged are also read. In the example, when the subsequent process is a car body assembly process, the above-mentioned processing conditions are expressed by the assembly difficulty level, and are the processing conditions for the work in progress currently waiting at the merging point X position, that is, the work difficulty level. Let x be ₀ , and let the difficulty level of the previous 5 work-in-progress works that have already been sent from the confluence point X to the subsequent process be respectively
x ₁ , x ₂ , x ₃ , x ₄ , x ₅ , and these six processing conditions, that is, the work difficulty level, are detected.In practice, such detection is performed by label readers 22 and 24 for each work in progress. The information is read from the label attached to the workpiece W and supplied to the merging control computer 26 as electrical information. When the machining conditions of the unfinished workpieces to be merged and the machining conditions of a predetermined number of unfinished workpieces that have already been serially conveyed to the subsequent process are read as described above, the merging control computer 26 performs processing based on these machining conditions. It is determined whether or not to merge. In the embodiment, this determination of whether or not to merge is performed by calculating an evaluation function based on the work difficulty level or the work difficulty level and a weighting coefficient. This evaluation function y is obtained from the processing conditions x ₀ to x ₅ and weighting of these according to the transport order. Next, the merging control computer 26 compares the evaluation function y with reference values A and B, and determines whether or not merging is possible so that leveling can be performed in the subsequent process. Roughly speaking, the determination of whether or not this merging is possible is performed if the evaluation function is smaller than A, that is, the lower reference value, then even if the work in progress is merged, sufficient work can be done in the subsequent process, so the merging is not performed. On the other hand, if the evaluation function is larger than this lower reference value A, merging this work in progress will make processing in the subsequent process troublesome, and it will be kept on standby waiting for the next merging chance. . However, if a judgment is made based only on the lower reference value A in this way, the number of workpieces in the standby state tends to increase too much, so in this embodiment, the upper reference value B is set separately from the reference value A If the evaluation function y is larger than the upper reference value B, the work in the subsequent process will be extremely difficult, so such merging is prevented. If there is an evaluation function, it is determined whether to merge or wait depending on the amount of retention at the merge point X. That is, when the evaluation function y is between the two reference values A and B, the presence or absence of stagnation is determined based on the signal from the stagnation sensor 30, and when the number of stagnation exceeds a predetermined value, for example 5, post-processing is performed. It allows merging even with evaluation functions that would make the work a little complicated, and eliminates excessive stagnation. On the other hand, if the evaluation function y is between the two reference values A and B and there is no stagnation, or if the evaluation function y is larger than the upper reference value B, the merging is blocked and only the normal main line is allowed to flow. Control takes place. Therefore, according to the present invention, the processing conditions of each work in progress are calculated together with the processing conditions of a plurality of work in progress serially conveyed before it, and the confluence control is performed so that post-process processing is performed optimally. As a result, it is possible to obtain a well-balanced process progress effect that does not cause local work delays even in production progress management that includes branching and merging with complicated branches. The calculation of the above-mentioned evaluation function is, in principle, performed based on both the machining conditions in the post-process, particularly the difficulty of the work, and a weighting coefficient based on the order of sending.The latter weighting coefficient is determined according to the machining interval in the post-process. Generally, if the machining interval in the post-process is long enough, it is preferable to determine the evaluation function based only on the machining conditions, that is, the work difficulty level, without weighting. When the machining interval is short, that is, when the workpieces in progress W are continuously fed with almost no margin, it is preferable to weight them based on the feeding order, and the earlier the workpieces are sent out, the more the workpieces are fed. The weight is set small. An example of calculation of the evaluation function will be explained below. The basic evaluation function calculation in this embodiment is performed based on the following formula. y=ax ₀ +bx ₁ +cx ₂ +dx ₃ +ex ₄ +fx _5Here , x ₀ indicates the machining conditions, that is, the difficulty level, in the subsequent process of the joining workpieces in progress, and x ₁
~x ₅ is the 5 that was serially conveyed to the subsequent process immediately before that
The processing difficulty level of each work in progress is shown, and each difficulty level information is determined according to the following examples. Also, a to f are weighting coefficients,
When weighting is necessary, different values are assigned according to the transport order, or when weighting is not necessary, all values are set to "1". Case 1 (Table 1) Processing conditions, that is, work difficulty: 10, 5, -
Evaluation functions based on various combinations when four types of -10 are applied to each x, and the weighting coefficients are a = 1, b = 1, c = 0.5, d = 0.33, e = 0.25, f = 0.25. If y is determined as follows, and the reference values for determining whether or not to merge are as follows: lower reference value A = 9 and upper reference value B = 15, then whether or not to merge is determined for each of the following 20 combinations.

【table】

[Table] In case 1, whether or not to merge is possible, the 〇 mark indicates a merging instruction, the △ mark indicates a judgment based on the amount of retention, and the × mark indicates a merging prevention. Case (Table 2) This is a case where weighting is removed under the same conditions as Case 1, and the coefficient is a = b = c = d = e = f = 1, and lower reference value A = 0 upper reference value B = 20 is set to .

【table】

[Table] Case 3 (Table 3) The weighting coefficient is the same as Case 1, but the processing conditions, that is, the work difficulty level, are set to four types: 10, 8, 6, and 4, and the lower standard value A = 25 and the upper standard The value B=28 is set.

【table】

[Table] Case 4 (Table 4) This is a case where the weighting is removed under the same conditions as the difficulty level of Case 3, and the lower standard value A = 40 and the upper standard value B = 48 are set.

【table】

[Table] As described above, the desired case is selected according to the vehicle type or article handled in each process, and Table 5
shows a list of processing conditions and weighting coefficients for each case, and Table 6 summarizes the evaluation results.

【table】

[Table] As is clear from the above examples, a desired evaluation function is selected depending on the article to which the present invention is applied,
In practice, if there is idle time for each workpiece in a process in which the workpieces are transported relatively slowly, the weighting coefficient based on the transport order as in case 2 or case 4 is removed, while the When there is little time, merging control using weighting coefficients based on the transport order can be achieved. FIG. 3 shows another embodiment of an automobile assembly line to which the physical distribution control method according to the present invention is applied, and the same members as those in FIG. The characteristic feature of the second embodiment is that a worker M is placed at each merging point . Therefore, the operator M operates the operation button 42 based on this display to perform predetermined merging control using the pusher 20 described above. The display 40 has three types of display, for example, blue, yellow, and red, and each display color indicates merging, judgment based on the amount of retention, and standby. FIG. 4 shows a control flow chart of the second embodiment, which is almost the same as the chart in FIG.
The difference is that after the merging is determined based on the evaluation function, the merging control computer 26 simply displays the lamps on the display 40, and the worker M performs a predetermined operation depending on the display color. It becomes possible to perform control for each confluence point X, taking into account the operator's judgment. [Effects of the Invention] As described above, according to the present invention, merging control at a merging point, which has not been performed conventionally, can be made easier or equalized in subsequent processes based on various processing conditions. This makes it possible to perform well-balanced process control without causing local delays in the entire line, and to provide an extremely suitable logistics control method for processing or assembly lines that include complex branching and merging.

[Brief explanation of drawings]

FIG. 1 is a schematic explanatory diagram showing a preferred first embodiment to which the physical distribution control method according to the present invention is applied, FIG. 2 is a flowchart diagram showing control operations of main parts in the first embodiment, and FIG. 4 is a schematic configuration diagram showing a second embodiment of the present invention, and FIG. 4 is a flowchart of main parts in the second embodiment. 10...First conveyor, 12...Second conveyor, 26...Merge control computer, X...Merge point, W...Work in progress, x ₀ ...Processing conditions for work in progress to be merged, x ₁ ~ x ₅ ... Processing conditions for work in progress that was serially transported just before the merging decision,
y...Evaluation function.

Claims (1)

[Claims] 1. In a logistics control method in which in-process workpieces supplied from a plurality of pre-processes are merged into a single post-process at a confluence point and conveyed serially, each in-process work has a The processing conditions including the work difficulty are displayed, and the processing conditions are read from each work in progress supplied to the merging point, and the work difficulty and the merging target of a predetermined number of work in progress serially transported immediately before the merging point are displayed. An evaluation function is obtained by multiplying the work difficulty of each in-process work by a coefficient and performing an addition operation, and then comparing the evaluation function with at least one reference value to level out the work difficulty in the subsequent process. If the evaluation function is below the standard value and the merging is possible, the in-process work is sent to the next process, and on the other hand, if the evaluation function exceeds the standard value and the merging is possible, the in-process work is sent to the next process. A logistics control method characterized by waiting in a pre-process. 2. A physical distribution control method according to claim 1, characterized in that the work in progress at the merging point is automatically supplied by an automatic supply device. 3. A physical distribution control method according to claim 1, characterized in that the determination of whether or not to merge at the merge point is made by a display on a display, and the operator operates the supply device based on this display. 4. In the method according to any one of claims 1 to 3, the reference value for determining whether or not to merge is composed of at least two reference values, and the added evaluation function is less than or equal to the lower reference value. If the evaluation function is between the lower reference value and the upper reference value, the work in progress is flown to the next process as it can be merged, and if the number of accumulated workpieces exceeds a predetermined value, the work in progress is flown to the subsequent process. On the other hand, until the number of retained pieces exceeds a predetermined value, the in-process work is held in the previous process as a failure to merge, and when the evaluation function exceeds the upper standard value, the work in progress is determined to be rejected regardless of the number of retained pieces. A logistics control method characterized by making a workpiece stand by in a previous process.