JPH09136246A - Method and device for evaluation of optimum indication point - Google Patents

Abstract

PROBLEM TO BE SOLVED: To increase the efficiency of a production line and know the optimum indication point quantitatively by adding the amount of stock in an entire production line to a time needed until a product is completed in the same dimension, and judging which is optimum to give the production sequence indication to which process. SOLUTION: For example, when a purchase order which indicates the type of an ordered vehicle is input into a host computer 29 of a office by a dealer 23 which receives the order of the purchase of a vehicle from a customer, the hot computer 29 of the head office plans the production sequence schedule of the vehicle as a product based on the purchase order data obtained by collecting the purchase orders. Also, the amount of stock in the entire production line, for example, when a production sequence indication is given to a second process 25 or a first process 27 and a time needed until the product is completed according to the production sequence indication are added to each other in the same dimension. Thus the host computer 29 judges which is optimum to give the production sequence indication to which process among multiple processes 25 and 27.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a production line which is composed of a plurality of processes and produces a plurality of types of products, and to which process a production order instruction made based on order data is given, the stock amount. Also, the present invention relates to an evaluation method and an evaluation device of an optimum designated point for judging whether or not it is optimum by judging from the completion time.

[0002]

2. Description of the Related Art Conventionally, for a production line which is composed of a plurality of processes and produces a plurality of types of products, a production order instruction made based on order data has been given to the entire production line. That is, the production line including a plurality of processes was also treated as one block. For example, in JP-A-6-9022,
Production bases that are production lines, factory warehouses that store products,
Although it has been shown that production control is carried out sequentially upstream in each of the distribution bases for delivering products to customers, using order data, inventory parameters, monthly average inventory, etc. for each product. Is treated as one block as a production base. In addition, Japanese Unexamined Patent Publication No.
In Japanese Patent No. 364571, as a production line simulation system, a method of evaluating a production plan by displaying a delivery date compliance rate and inventory changes is shown, but the production line is treated as one block.

[0003]

However, the conventional production management system has the following problems. (1) Since the production line is processed as one block, there is only one way to give an instruction to the production line which is composed of a plurality of processes and produces a plurality of types of products. It was not possible to give the production instruction to the optimum instruction point where the efficiency could be improved. In addition, there is no method for determining which of the plurality of steps is best for the production line. Further, no consideration was given to waste generated by the stock of intermediate products existing between the processes of the production line. (2) In order to judge the optimality of the production line, it is necessary to consider two different dimensional factors of the stock quantity and the completion time. However, in the conventional method disclosed in Japanese Patent Laid-Open No. 4-364571, both of them are considered. It was only calculated in dimensions and displayed separately, and the overall judgment of both was still dependent on the experience and intuition of the operator. Therefore, as the number of types of products increases, it has become difficult to objectively evaluate an optimal production plan.

The present invention has been made in order to solve such a problem, and which method is used for a production line, which is composed of a plurality of processes and produces a plurality of types of products, based on order data. It is an object of the present invention to provide an evaluation method and an evaluation device for an optimum instruction point that can judge whether it is optimal to give a production order instruction to a process.

[0005]

The optimum pointing point evaluation method, production line and evaluation apparatus of the present invention have the following features. (1) It is an evaluation device that judges the quality of a production sequence instruction point for instructing the production sequence of products made based on order data for a production line that is composed of a plurality of processes and that produces a plurality of types of products. Then, by summing the inventory quantity of the entire production line when the production order instruction is given to each step of the plurality of steps and the time until the product is completed in accordance with the production order instruction, and summing up, It is determined which one of a plurality of processes is best to be given a production order instruction. (2) Further, the evaluation method of the optimum designated point of the present invention is
In the evaluation method described in (1), a value is defined by defining a function with the stock amount and the time as input variables, and a value calculated by the function for each input variable is multiplied by a weighting factor and added. Is used as the evaluation value. (3) Further, the production line of the present invention is optimized using the evaluation method of the optimum designated point described in (1) or (2).

(4) Further, the optimum pointing point evaluation device of the present invention is composed of a plurality of processes, and (a) a product made based on order data for a production line producing a plurality of types of products. Is an evaluation device for judging the quality of a production sequence instruction point for instructing the production sequence of the production sequence, and the inventory amount in the entire production line when the production sequence instruction is given to each process of a plurality of processes, and the production sequence. The same dimensioning means for equalizing and summing the time until the product is completed according to the instruction, and (b) Optimal for determining which of a plurality of steps the production order instruction is best given. It has an indication point judging means. (5) Also, the optimum pointing point evaluation device of the present invention is
In the evaluation device described in (4), input variable storage means for defining and storing a function having the inventory quantity and the time as input variables, and a value calculated from the function for each input variable, respectively. The present invention is characterized by having a weight addition means for multiplying and adding a weight coefficient and an output means for outputting the value added by the weight addition means as an evaluation value.

[0007]

Embodiments of the present invention will be described below in detail with reference to the drawings. FIG. 4 shows the process of the method for evaluating the optimum designated point. That is, the process data of each production process of the production line to be evaluated is input (S
1) The optimum instruction point evaluation device evaluates the optimum instruction point (S2), and outputs the optimum instruction point that can operate the production line most efficiently (S3). FIG. 5 shows the hardware configuration of the evaluation device for the optimum designated point. The evaluation device is a personal computer 11, a CPU 14 which is a calculation means, a production process data file 12 which is a data storage means, an evaluation index file 13,
It is composed of an evaluation result file 15. The evaluation index file 13 stores a shape index used in an evaluation function to be described later and a weighting coefficient for the lead time and the stock amount.

The CPU 14 is a ROM 17 for storing a program for implementing the method for evaluating the optimum designated point according to the present invention, and a RAM for temporarily storing data.
Contains 18 etc. The ROM 17 is a function g for obtaining the inventory amount of the entire production line when a production order instruction is given to a specific process i of a plurality of processes.
(Zi) calculation program 172, f (Ti) calculation program 171 which is a function for calculating the lead time which is the time until the product is completed according to the production order instruction given to the specific process i, and each calculation program A Hi calculation program 173 that multiplies the result value by a weighting factor to add dimensionlessly, and an optimum designated point determination program 174 that determines the maximum value of Hi and determines the optimum designated point are stored. Here, f (Ti) calculation program 171, g (Z
i) Calculation program 172 and Hi calculation program 173
The same dimensioning means is constituted by. Also, the production process data file 12 and the evaluation index file 1
3. The evaluation result file 15 is a file name stored in a disk or the like. In addition, the personal computer 1
A data input display terminal 16 which is an input / output terminal such as a keyboard and a CRT is connected to the terminal 1.

Next, the structure of the data stored in each file will be described. FIG. 9 shows the structure of the production process data file 12. Since this process data is modeled for the production line shown in FIG. 12,
First, the production line in FIG. 12 will be described. Parts required for assembling the product are delivered from the parts manufacturer 21 to the production factory 22 by truck or the like. The delivered parts are stored in the parts inventory storage 24 in the production factory 22. The production line of the production factory 22 includes the second process 25 and the first process 25.
The production line is composed of two processes, process 27, for assembling and processing a plurality of types of products, for example, passenger cars. The second step 25 is to store the parts at the parts inventory storage 24 at the start of production.
The processed semi-finished products are transported to the semi-finished product storage space 26 for storage. Also, the first step 27
Stores the semi-finished products required at the start of production in the semi-finished product storage area 26
The finished product obtained from the above is processed and the finished product is transported to the finished product storage area 28 for storage. Further, the finished product is transported to the store 23.

In the above model of the production line, an ordering order indicating what kind of vehicle has been ordered is input to the head office host computer from the dealer 23 who has received a vehicle purchase order from the customer. The host computer of the head office makes a production order plan of vehicles, which are products, based on the order data obtained by collecting the order orders. In a production line, production is started in a production order instructed by a specific process among a plurality of processes. The specified process that receives the production instruction from the host computer and starts the production is called an instruction point.

Each lead time in the process is indicated by an arrow. The lead time in the second step 25 is Tp2,
The lead time in the first step 27 is Tp1. The transportation time from the parts inventory storage 24 to the second process 25 is Ta1
The transportation time from the second process 25 to the semi-finished product storage space 26 is Ta2, the transportation time from the semi-finished product storage space 26 to the first process 27 is Ta3, and the transportation time from the first process 27 to the finished product storage space 28. The transportation time to Ta4 is Ta4, and the transportation time from the finished product storage 28 to the store 23 is Tout. As a point for instructing the production sequence of the products made based on the order data, for example, the second step 25 (I2 in the figure)
Indicated by ), The first step 27 (indicated by I1 in the figure), and the finished product inventory (indicated by I0 in the figure).

For example, in the case of instructing the production sequence plan in the first step 27, that is, in the case of using I1 as the instructing point, FIG.
Shown in As an order received from the store 23, A,
It is assumed that B, C and A are issued. In this case, the host computer 29 directs the production sequence A, B, C, A to the first step 27. Therefore, as shown in FIG. 2, the vehicle completed in the first step 27 is an order itself from the sales shop 23 and is transported to the sales shop 23 as soon as it is completed. Is zero. On the other hand, in this case, in the second process 25, the production order is determined by supplementing the semi-finished product storage space 26 with the semi-finished products used in the first process 27.

Next, FIG. 3 shows the case where the production sequence plan is instructed in the second step 25, that is, the case where I2 is the instruction point. As an order received from the store 23, A, B,
Suppose C and A are issued. In this case, the host computer 29 sets the production sequence A, B, C, A in the second step 25.
To instruct. The second step 25 is the production sequence A,
Since the semi-finished products are produced according to B, C, and A, and the produced semi-finished products are directly transported to the first process 27, the stock amount in the semi-finished product storage space 26 is zero. Further, since the finished product produced in the first step 27 is transported as it is to the store 23, it can be considered that the inventory amount of the finished product storage 28 is zero. In other words, it is only necessary to store the inventory of the parts in the parts inventory storage area 24 as the inventory, and the inventory amount of the entire production factory 22 can be reduced, and the inventory management cost can be reduced accordingly. However, the lead time for delivery to the store 23 becomes long because the time from the second step 25 is added, and the time from the customer's order to the delivery of the product becomes long, which impairs the customer's willingness to purchase. Becomes

The case where the designated points are I1 and I2 has been described above. However, when the designated points are changed, two contradictory characteristics, that is, the production lead time and the stock amount, change, so which is the best designated point. Was difficult to determine. The present invention proposes a method of determining an optimum designated point by making the contradictory characteristic values of the lead time and the stock amount into the same dimension and summing them. The specific method will be described below.

FIG. 9 shows the structure of the production process data file 12 which is the concrete data of the production line to be evaluated. The number of steps in the production line is 2 in this embodiment.
It is a process. The lead time in the first step 27 is T
p1 = 5 hours, and the lead time in the second step 25 is Tp2 = 3 hours. Further, the transportation time Tout from the finished product storage 28 to the dealer 23 is 10 hours, and the transportation time Ta4 from the first process 27 to the finished product storage 28 is Ta4 =
It takes 0.1 hours, and the first process 2 from the semi-finished product storage 26
No. 7, the transportation time Ta3 = 0.08 hours, and the transportation time Ta2 = 0.
It is 05 hours, and the second process 25 from the parts inventory storage 24
The transportation time Ta1 is 0.05 hours. In addition, the type of finished product S0 = 100 types, and the type of semi-finished product S1
= 20 types, and the types of parts S2 = 5 types. Also,
The standard stock amount of each part and finished product is the standard stock amount of finished products V0 = 5, and the standard stock amount of semi-finished products V1 = 10.
The standard inventory quantity of parts is V2 = 20. These process data are input to the personal computer 11 from the data input display terminal 16 and stored in the production process data file 12.

Next, the evaluation index file 13 shown in FIG.
Will be described. In the present embodiment, the weighting factor W = 0.25 for the lead time and inventory, the shape index (a) of the lead time evaluation function f (T) = 0.5, and the shape index of the inventory quantity evaluation function g (Z). (B) = 0.01 is input to the personal computer 11 from the data input / display terminal 16 and stored in the evaluation index file 13. These coefficients will be described in detail later.

Next, regarding the evaluation method of the optimum designated point,
A detailed description will be given based on the flowchart of FIG. First, after initializing the designated point i = 0 (S11), it is determined whether or not i = N (S12). When i is not N (S11, NO), the designated point i The lead time Ti at the time is calculated (S13). Next, the inventory quantity Zi of the component (finished product) at the designated point i is calculated (S14). Next, the evaluation value Hi is calculated (S15). Next, the evaluation value H
The i is stored in the evaluation result file 15 (S16).
The method of calculating Ti, Zi and Hi will be described in detail later. Next, after setting i = i + 1 (S17), S1
Return to 2. Then, S3 to S7 are repeated until i = N. When i = N (S12, YES), H1, H
2, ... Find the maximum i in HN (S18),
The evaluation result file 15 is stored and stored as the optimum designated point (S19). This is the end of the process.

Here, the lead time Ti of the designated point i
Is the total of the process lead time and the transportation time from the designated point i to the store 23. The inventory quantity Zi of parts (finished products) at the designated point i is the total inventory quantity located upstream of the designated point i. The evaluation function Hi of the designated point i is calculated by the following formula. Hi = Wf (Ti) + (1-W) g (Zi) where f (Ti) is the lead time function and is represented by the formula f (Ti
) = E- ^aTi , which is a value shown in the graph in FIG. 6, and is specifically stored in the f (Ti) calculation program 171. In FIG. 6, the lead time Ti is T
When i = 0 (induction), f (Ti) = 1 is excellent, and as Ti increases, f (Ti) approaches 0 and deteriorates. That is, the lead time Ti is the time from the receipt of an order from the customer to the delivery of the product, and as Ti increases, the customer's dissatisfaction increases.

In the present embodiment, as shown in A of FIG.
An exponential function is adopted as f (Ti). The exponential function is adopted in this model because the smaller the lead time Ti is, the more the evaluation value is affected and the lead time Ti is
This is because it is assumed that the effect will decrease as the value increases. That is, in FIG. 6A, when the lead time Ti changes by 10 days, the change amount is b when the lead time Ti is small, whereas the change amount is only d when the lead time Ti is large. is there. Further, if the influence is considered to be constant regardless of the magnitude of the lead time Ti, the straight line B in FIG. 6 may be adopted.

Further, g (Zi) is a stock quantity function and is represented by the mathematical expression g.
The ^value is represented by (Zi) = e- ^bZi and is a value shown in the graph in FIG. 7. Specifically, it is stored in the g (Zi) calculation program 172. The inventory quantity Zi is Zi = 0 (zero inventory)
In the case of, it is shown that f (Ti) = 1 is excellent, and Zi
As g becomes larger, g (Zi) approaches 0 and becomes worse. That is, the inventory management cost can be reduced as the inventory quantity decreases. In this embodiment, as shown in C of FIG. 7, an exponential function is adopted as g (Zi). The exponential function is adopted in this model because the smaller the stock quantity Zi, the more the evaluation value is affected, and the stock quantity Zi
This is because it was assumed that the effect would decrease as i increases. If the influence is considered to be constant regardless of the magnitude of the inventory quantity Zi, the straight line D in FIG. 7 may be adopted.

Next, f (Ti) = e- ^aTi , and g (Zi
) = E- ^bZi The method of determining the constants a and b will be described. a and b are parameters for determining the shape of the evaluation function. Also, a and b play a role of making different dimensions of Ti and Zi non-dimensional and making them the same dimension.
If a and b are large, the shape will be abruptly reduced when i changes. Empirically, the lead time Ti and the inventory quantity Zi are
It is known that when it exceeds a certain value, it becomes worse rapidly.
The certain period is a period in which the customer can spend the lead time Ti, and the upper limit of the storage space in the inventory amount Zi. Therefore, in the present embodiment, empirically, the period during which the customer can spend is α days, and the inventory upper limit is β, and in the present embodiment, a = 1 / α and b = 1 / β.
That is, assuming that α is 2 days and β is 100, a = 0.
5, b = 0.01 is used.

W is a weighting function, and 0≤W≤1. The weighting function W indicates which of two different quantities, the lead time Ti and the stock quantity Zi, is to be emphasized. When W = 0, only the inventory function Zi is considered, and when W = 1, only the lead time Ti is considered. Two importance levels can be arbitrarily determined at the intermediate value. In the present embodiment, the lead time T
Since the model considering i and the inventory quantity Zi in the ratio of 1: 3 was considered, W = 0.25. The evaluation function Hi is T
It is expressed as a function determined by two variables i and Zi and takes a value of 0 to 1. The closer to 1, the better the comprehensive evaluation is. Next, the structure of the evaluation result file 15 is shown in FIG. The lead time function value Ti, the inventory quantity function value Zi, the designated point evaluation value Hi, and the optimum designated point flag are stored in the evaluation result file 15 as the evaluation result.

Next, a specific example will be described. That is, FIG.
By using the production process data shown in FIG. 10 and the evaluation index shown in FIG. 10, the three designated point candidates I1 in FIG.
Which point in I2 and I0 should be given the production order,
Stock time and time from ordering products to completion 2
From one perspective, we will examine whether the most efficient production is possible. The lead time Ti at the above three designated points is calculated. T0 = Tout = 10h T1 = Ta3 + Tp1 + Ta4 + Tout = 0.05 + 5 + 0.1 + 10 = 15.15h T2 = Ta2 + Tp2 + Ta2 + Ta1 = 0.05 + 3 + 0.08 + 15.15 = 18. 18h Next, inventory quantity Z of parts (finished products) at the above three designated points
Calculate i. Z0 = S0 × V0 + S1 × V1 + S2 × V2 = 100 × 5 + 20 × 10 + 5 × 20 = 800 pieces Z1 = S0 × V0 + S1 × V1 = 100 × 5 + 20 × 10 = 700 pieces Z2 = S0 × V0 = 100 × 5 = 500 pieces

Next, the evaluation function Hi is calculated. H0 = 0.25 * e- ^{0.5 * 10} + (1-0.75) * e-0.01 ^{* 800} = 1.90 ^{* 10-3} H1 = 0.25 * e- ^{0.5 * 15.15} + (1-0. 75) xe ^{-0.01 * 700} = 0.81 x 10 ^-3 H2 = 0.25 xe ^{-0.5 * 18.28} + (1-0.75) xe ^{-0.01 * 500} = 5.07 x 10 ^-3 FIG. 11 shows a summary of the above. According to FIG. 11, since the value of H2 is the largest, i is the designated point.
I2 of 2 is judged to be optimum, and the optimum designated point flag is set.

FIG. 8 is a graph showing the specifically obtained evaluation function Hi. The X-axis is the inventory quantity Zi, the Y-axis is the lead time Ti, and the Z-axis is the evaluation function Hi.
When I0 is the designated point, Z0 = 800, T0 = 10
and h0 = 1.90 × 10 ^-3 . Also, I1
When the designated point is, Z1 = 700, T1 = 15.
15 h and H1 = 0.81 × 10 ^-3 . Also,
When I2 is the designated point, Z2 = 500, T2 = 1
It is 8.18 h and H2 = 5.07 x 10 ^-3 . That is, the point at the highest position on the Z axis is the optimum designated point.

As described in detail above, according to the optimum pointing point evaluation method and evaluation apparatus of the present embodiment, the entire production line when a production order instruction is given to each step of a plurality of steps Zi and the lead time Ti until the product is completed according to the production order instruction are made equal to each other and summed up, and which of the plurality of steps is best given the production order instruction? Since it is determined that in the production line consisting of multiple processes,
It is possible to quantitatively grasp the optimum instruction point that can maximize the efficiency of the production line. In addition, the amount of intermediate stock existing in the production line can be optimized.
Further, the functions g (Zi) and f (Ti) having the stock quantity Zi and the lead time Ti as input variables are defined, and the weighting coefficient (1-W), W is added to the value calculated from the function for each input variable.
Since the value obtained by multiplying and adding is used as the evaluation value, it is possible to balance the importance of the inventory quantity Zi and the lead time Ti by selecting the weighting function according to the property of the product produced on the production line. it can. Further, according to the production line optimized by the evaluation method according to the present embodiment,
The most productive production line can be realized.

Although the embodiments of the present invention have been described above, the present invention is not limited to the above embodiments, and various design changes can be made without departing from the spirit of the present invention. For example, in the present embodiment, the inventory quantity Zi
Although only the lead time Ti and the lead time Ti are evaluated, the same applies even if other factors are added depending on the characteristics of the product. Although the exponential function has been described as a function of the inventory quantity Zi and the lead time Ti, and g (Zi) and f (Ti), a linear function or another function may be used depending on the characteristics of the product.

[0028]

According to the optimum pointing point evaluation method and evaluation apparatus of the present invention, the stock amount of the entire production line and the production order instruction when the production order instruction is given to each process of a plurality of processes. According to the above, the time until the product is completed is made the same dimension and summed up to determine which of the multiple processes is best to give the production order instruction. It is possible to quantitatively grasp the optimum instruction point that can maximize the efficiency of the production line among the configured production lines. In addition, the amount of intermediate stock existing in the production line can be optimized.

[Brief description of the drawings]

FIG. 1 is a flow chart showing the operation of an optimum pointing point evaluation method and evaluation apparatus of the present invention.

FIG. 2 is an explanatory diagram when a production order instruction is given to a first step 27.

FIG. 3 is an explanatory diagram when a production order instruction is given to a second step 25.

FIG. 4 is a flowchart showing a method of evaluating an optimum designated point.

FIG. 5 is a block diagram showing a configuration of an evaluation device for an optimum designated point.

FIG. 6 is a data diagram of a lead time function f (Ti).

FIG. 7 is a data diagram of an inventory function g (Zi).

FIG. 8 is a data diagram showing an evaluation function Hi.

FIG. 9 is an explanatory diagram showing a configuration of a production process data file 12.

10 is an explanatory diagram showing the structure of an evaluation index file 13. FIG.

11 is an explanatory diagram showing the structure of an evaluation result file 15. FIG.

FIG. 12 is an explanatory diagram showing a configuration of a production line that is an evaluation target.

[Explanation of symbols]

 11 personal computer 12 production process data file 13 evaluation index file 14 CPU 15 evaluation result file 16 data input / display terminal 17 ROM 171 f (Ti) calculation program 172 g (Zi) calculation program 173 Hi calculation program 174 optimal designated point determination program

Claims (5)

[Claims] 1. An evaluation method for judging quality of a production sequence instruction point for instructing a production sequence of products produced based on order data for a production line which is composed of a plurality of processes and produces a plurality of types of products. In, in the case where the production order instruction is given to each step of the plurality of steps, the stock amount in the entire production line and the time until the product is completed according to the production order instruction are equalized and summed. By doing so, it is determined which one of the plurality of steps is best to give the production order instruction to, which is an evaluation method of an optimum instruction point. 2. The evaluation method according to claim 1, wherein a function having the inventory quantity and the time as input variables is defined, and a weighting coefficient is added to a value calculated from the function for each input variable. A method for evaluating an optimum designated point, which is characterized in that a value obtained by multiplying is used as an evaluation value. 3. A production line optimized using the method for evaluating an optimum designated point according to claim 1 or 2. 4. An evaluation device for judging the quality of a production sequence instruction point for instructing a production sequence of products produced based on order data for a production line which is composed of a plurality of processes and produces a plurality of types of products. In, in the case where the production order instruction is given to each step of the plurality of steps, the stock amount in the entire production line and the time until the product is completed according to the production order instruction are equalized and summed. Evaluation of the optimum designated point, which has the same dimensioning means and an optimum designated point judging means for judging which one of the plurality of steps is best to give the production order instruction. apparatus. 5. The evaluation apparatus according to claim 4, wherein an input function storage unit that defines and stores a function having the inventory quantity and the time as input variables, and is calculated from the function for each input variable. An optimum pointing point evaluation apparatus, comprising: a weight addition unit that multiplies each value by a weighting coefficient and adds the weight value; and an output unit that outputs the value added by the weight addition unit as an evaluation value.