JP4774970B2 - Quality control method, quality control program and quality control system - Google Patents

Description

  The present invention relates to quality control, and more specifically, calculates a process control capability index based on quality control data obtained in a product manufacturing process, and calculates a process loss cost when the value is equal to or less than a predetermined value. The present invention relates to a quality control method, a quality control program, and a quality control system that are ranked and presented.

  In manufacturing a product, a statistical management method is generally used in which quality characteristics are measured for the entire manufacturing process, and the measured data is statistically captured and managed. Xbar-R control charts, P control charts, process capability indexes, etc. are well known as statistical control methods. Set control standards for these quality characteristics and pass or fail based on the set values. Judgment is made. Then, the cause of the failure is predicted centering on the process having a high failure rate, and the management state is restored by taking an appropriate measure against the cause of the failure.

  For example, FIG. 11 and FIG. 12 show an example of a conventional management method. A management item is set for each process of the manufacturing process, and a process capability index (Cp value) is obtained from the measured data. Then, the process whose process capability index is below a predetermined value is extracted, the rank is assigned as the importance from the small value, and the cause is dealt with from the highest rank (ie, from the smallest Cp value). (In other words, since the process capability index indicates the ability to produce a product, the cause of the problem has been dealt with from the lowest ability). FIG. 11 is obtained from the quality control data obtained for the middle process in the large process and the process capability index in the management item in the middle process. FIG. 12 shows the Cp value of 1.33 or less extracted from the Cp values of FIG. 11, and is ranked because the Cp value is small. Here, the Cp value of drilling 1 in the part A production line is 0.67, which is the smallest value and ranks first, indicating that there is a problem in quality control at the drilling 1 processing speed. Next, the one with the lowest Cp value (rank 2) is the chemical cleaning 1 of the part B production line.

There has been proposed a method for accurately predicting the cause of a defect and improving it quickly. In this method, management criteria are set for management items, importance is set for each management item, management items are checked, and the check results, management items, and importance are displayed. . Since the management items are displayed according to the magnitude of the influence on the defect, the defect can be efficiently improved (for example, Patent Document 1).
Japanese Patent Laid-Open No. 2002-202807

  As shown above, statistical management methods are generally used in quality control. For example, when the process capability index falls below a predetermined value, it is judged that the importance is high from the low value. Then, it has been performed to rank and display and improve defects.

  This method can certainly cope with the cause of a process with low production capacity, but when considering the loss cost when the quality characteristics are corrected to return to the control target value, The loss cost is not necessarily the highest. For example, the cost with the third highest rank of the process capability index may be the highest in terms of loss cost. In other words, even if the process capability index is low, the loss cost is low if the manufacturing cost or production volume of the process is small. Rather, even if the process capability index is somewhat large, the loss cost is low. Is advantageous. Thus, there is a problem in improving the process with the process capability index. The same applies when the defect rate is simply obtained.

  Moreover, although the patent document 1 shown above is considered that the influence degree with respect to a defect is decided according to the preset importance, the disclosure on the basis for determining the importance is not made, and the importance is determined. If it is based on experience values, it can be considered that judgments differ depending on the person, and there is a problem.

  The present invention obtains a loss cost required for restoration from quality management data (that is, a cost when correction is made so as to become a management target value), ranks and presents them, a quality management method, a quality management program, and quality The purpose is to provide a management system.

The quality control method, quality control program, and quality control system of the present invention are configured as follows.
(1) 1st invention 1st invention calculates | requires the loss cost at the time of correcting so that it may become the management target value of the process when the process capability index of each process is below a predetermined value, and ranks it. It is a quality control method to go and present.

  The principle will be described with reference to FIG. The first invention includes a manufacturing cost storage procedure 10, a management reference value storage procedure 20, a quality control data storage procedure 30, a process capability index calculation procedure 40, a loss cost calculation procedure 50, and a loss cost presentation procedure 60. These individual components will be described.

  The manufacturing cost storage procedure 10 stores the manufacturing cost for each manufacturing process. For example, material costs, labor costs, power costs, etc., generated in the process.

  The management reference value storage procedure 20 stores a management item predetermined in each process and a set value for the management item. The set value includes the target value of the management item.

  The quality management data storage procedure 30 measures and stores quality management data for the management items of each process.

  The process capability index calculation procedure 40 calculates a process capability index based on the management reference value stored in the management reference value storage procedure 20 and the quality management data stored in the quality management data storage procedure 30.

The loss cost calculation procedure 50 extracts a management item in which the process capability index obtained in the process capability index calculation procedure 40 is equal to or less than a predetermined value, and determines the loss cost in the process of this management item as a variation in quality control data. It is determined using a predetermined loss function based on the manufacturing cost and the production amount of the product. ,
The loss cost presentation procedure 60 ranks and presents the loss cost for the obtained process according to the magnitude of the loss amount.
(2) Second invention The second invention is the cost when it is assumed that the loss cost of the first invention is corrected so that the value of the quality control data becomes the target value set in the management item. This is the cost of variation when the difference from the target value of the management item is not corrected.
(3) Third invention In the third invention, data of an error factor and a signal factor for a control factor is stored in advance, and the control of a management item whose process capability index is equal to or less than a predetermined value using the data. The correction value for the factor is obtained and presented. The quality control method of the first invention further includes a quality engineering data storage procedure.

  The principle will be described with reference to FIG. The fourth invention includes a manufacturing cost storage procedure 10, a management reference value storage procedure 20, a quality control data storage procedure 30, a process capability index calculation procedure 40, a loss cost calculation procedure 50, a loss cost presentation procedure 61, and a quality engineering data storage procedure. 70. Among these, the manufacturing cost storage procedure 10 to the loss cost calculation procedure 50 are the same as those in the first invention, so that the description thereof is omitted.

  The quality engineering data storage procedure 70 stores quality engineering data of an error factor that is a factor of variation of the control items with respect to the control factor and a signal factor that is a factor that changes the value of the control factor.

The loss cost presentation procedure 61 is a management item corresponding to the ranked loss cost obtained in the first invention and the quality control data and quality engineering data obtained in the ranked loss cost process. A correction value for the set value is obtained, and the ranked loss cost and correction value are presented.
(4) Fourth invention The fourth invention is the quality control program of the first invention.
(5) Fifth Invention The fifth invention is the quality management system of the first invention.

  According to the first invention, the loss cost for the management item that deviates from the management standard is presented. Therefore, it is possible to provide a quality control method capable of taking measures for improvement from the item with the largest loss.

  According to the second invention, the loss cost as a producer is clarified, and by comparing the loss cost for variation when the average value of quality control data is not adjusted with the cost for adjusting the average value, the average It is possible to provide a quality control method capable of examining the validity of the value adjustment method.

  According to the third aspect of the invention, since a correction value for the management standard can be obtained based on quality engineering data, it is possible to provide a quality management method capable of quickly setting an appropriate management standard.

  According to the fourth to fifth inventions, it is possible to provide a quality management program and a quality management system capable of achieving an efficient improvement procedure.

  An embodiment of the present invention will be described with reference to FIGS.

  First, a configuration example of the entire quality management system will be described with reference to FIG. FIG. 3 shows an example of the manufacturing process of the plating process. In the manufacturing apparatus of each manufacturing process (pretreatment process 301, water washing 1 process 302, plating process 303, water washing 2 process 304, drying process 305, inspection process 306). The attached sensor 200 acquires quality management data and sends the quality management data to the server 100. The sensor 200 attached to each manufacturing process detects the value of the management item shown at the bottom of the process name, and transmits the detected data as quality management data. For example, in the pretreatment step 301, the chemical concentration, the liquid temperature, the processing time, and the liquid circulation amount of the chemical liquid are detected at predetermined times by the respective sensors 200, converted into digital amounts, and transmitted.

  When the server 100 receives the quality control data sent from the sensor 200, the server 100 stores these data in a predetermined storage location, and at the same time the process capability with a management reference value set in advance based on the data stored for a certain period of time. The index is calculated, and the loss cost is calculated and displayed on the display described below.

  FIG. 4 is a configuration example of a computer that manages the entire quality management system. A control unit 110 for controlling programs and data, a display 120 for displaying a loss cost to a process manager, a KB (keyboard) 130 for inputting data for setting a management reference value, a production plan for plating processing From the production plan storage unit 140 for storing the data, the manufacturing cost storage unit 150 for storing the manufacturing cost for each process, the management reference value storage unit 160 for storing the management items and their management reference values for quality control, and the sensor 200 A quality control data storage unit 170 for storing the transmitted quality control data, an error factor for the control factor, a quality engineering data storage unit 180 for storing the signal factor quality engineering data, and a main memory 190 for executing the quality control program Constitute.

  The quality management program further includes a management standard setting unit 191, a quality management data acquisition unit 192, a process capability index calculation unit 193, a loss cost calculation unit 194, a correction value calculation unit 195, and a loss cost presentation unit 196. The function of each part of these quality control programs will be described next.

  For example, the management reference setting unit 191 performs a process of storing the target value (median value), the upper limit value, and the lower limit value for the management item input by the process manager in the management reference value storage unit 160.

  The quality management data acquisition unit 192 stores the quality management data sent from the sensor 200 at regular time intervals in the quality management data storage unit 170.

  The process capability index calculation unit 193 calculates a process capability index based on the quality management data stored in the quality management data storage unit 170 and the management reference value stored in the management reference value storage unit 160 at regular intervals. The calculated process capability index is stored in the management reference value storage unit 160 together with the average value, maximum value, minimum value, and variation of the quality control data.

  The loss cost calculation unit 194 stores the number of annual production plans stored in the production plan storage unit 140 and the manufacturing cost storage unit 150 for those whose process capability index calculated by the process capability index calculation unit 193 is equal to or less than a predetermined value. The annual loss cost is calculated based on the cost for each process and the quality control data stored in the quality control data storage unit 170.

  The correction value calculation unit 195 calculates a correction value for the management criteria of the management item for the management item whose process capability index calculated by the process capability index calculation unit 193 is a predetermined value or less with reference to the quality engineering data storage unit 180.

  The loss cost presentation unit 196 arranges the calculated loss costs in descending order of the amount of loss and displays the calculated correction values on the display 120 together with the calculated correction values.

  Next, data examples of the manufacturing cost storage unit 150, the management reference value storage unit 160, and the quality engineering data storage unit 180 will be described.

  FIG. 5 shows an example of data stored in the manufacturing cost storage unit 150. There are large processes and intermediate processes. For each intermediate process, material costs, labor costs, power costs, subtotals of those costs, It consists of repair costs, which are costs for repairing in the middle process. In FIG. 5, the major process is composed of three major processes, the part A production line, the part B production line, and the A / B part assembly line, and each large process has a plurality of middle processes shown in FIG. Yes.

  For example, drilling 1, which is the fourth middle process of the part A production line, has a material cost of 1,000 yen, a labor cost of 200 yen, and a power cost of 30 yen. It costs 230 yen, and it costs 230 yen because no material costs are required for restoration. When the entire process of the part A production line is completed, the cost required for it is 5,850 yen, and the repair cost is 2,910 yen. Similarly, the total cost of the entire process of the part B production line is 7,120 yen, the repair cost is 5,790, and the A / B parts assembly line is 14,820 yen and 3,200 yen, respectively. It is shown that.

  FIG. 6 shows an example of data stored in the management reference value storage unit 160. The management reference value storage unit 160 includes one or more management items for each intermediate process, and management reference values and quality characteristics for the management items. The management reference value includes a center, which is a target value, an upper limit, and a lower limit, and a reference value is set in advance for each. The quality characteristic is an average value, maximum value, minimum value, variation, and Cp value, and is a value calculated based on the acquired quality control data. The variation here is the standard deviation (σ), and the Cp value is the value of the process capability index as shown below.

Cp = (standard upper limit−standard lower limit) / 6σ
In general, the process capability index is often represented by the symbol Cpk, and the Cp value is a function of variation σ with respect to the standard width, whereas Cpk is a function of the bias of the average value. If there is no bias in the average value, Cp = Cpk. Here, since the average value is adjusted, the Cp value is used. Note that the value of Cpk is represented by Cpk = (1-k) * Cp, and the value of k is the following equation.

k = ((standard upper limit + standard lower limit) / 2−average value) / (standard upper limit−standard lower limit) / 2
For example, in the case of drill rotation speed, which is a management item of the drilling 1 process, the center of the management standard is 800, an upper limit 850, and a lower limit 750. Although the unit is not shown in the figure, it is rpm (revolution per minute). And the average value 822, the maximum value 835, the minimum value 810, the variation 8.77, and the Cp value are 1.90 from the data obtained by measurement.

  FIG. 7 shows an example of data in the quality engineering data storage unit 180, and FIG. 7 (a) shows the relationship between the error factor and the signal factor with respect to the control factor. For example, the adhesive viscosity, which is a control factor, has a coating temperature as an error factor, and is related to the coating pressure as a signal factor.

  FIG. 7B shows the basic function. For example, the relationship between the coating pressure and the adhesive weight is in the range of values between the two straight lines shown in the figure. This linear function can be shown as a single straight line in the ideal state (no error exists), but as an error that changes the slope of the function between the application pressure and the adhesive weight, it varies depending on changes in temperature and solvent concentration. If the viscosity changes, even within the control range, there will be a range of slopes in the positive worst case and the negative worst case. The narrower the slope, the closer to the ideal state.

  Similarly, the relationship between the load and displacement in bonding changes in inclination due to errors such as temperature and humidity, and the smaller the fluctuation range, the closer to the ideal state.

  FIG. 7C shows the effect of each factor (A, B... H) on the quality (or characteristics), and the SN ratio (indicated by a dotted line) is an error (difficult to manage) such as the environment or use conditions. The higher the value, the better the stability. Sensitivity is a response characteristic. The S / N ratio and sensitivity can be expressed by the following equations.

ここで、β ：比例定数
ｒ ：入力の大きさ（信号の大きさ）
Ｖｅ：誤差分散
Ｓβ：比例定数の変動
この式から分かるように、ＳＮ比の大きさは誤差分散Ｖｅに対する感度の安定性を示している。

Where β: proportionality constant
r: input size (signal size)
Ve: error variance
Sβ: Fluctuation of proportionality constant As can be seen from this equation, the magnitude of the SN ratio indicates the stability of sensitivity to the error variance Ve.

  Next, the loss cost used in the present invention will be described. The loss cost is calculated using a loss function shown in FIG. 8 as a loss cost L1 when the difference from the target value is not corrected and a loss cost L2 when the difference is corrected to the target value. Since the loss function shown in FIG. 8 is generally known, a description thereof will be omitted, but a calculation method will be described using a specific example.

  In the part A manufacturing line of FIG. 5, when the hole diameter exceeds the functional limit Δ0 of 70 μm in the drilling 2 process and the assembly is discarded, the cost A0 (equal to the consumer loss of FIG. 8) is 5 , 850 yen, the repair cost A when the hole diameter is small and repairable (equal to the manufacturer's loss in FIG. 8) is 2,450 (from the overall repair cost 2,910 in FIG. 5, drilling 1 and drilling 3 230 yen x 2 is subtracted). The tolerance is 45.3 μm by adding the values of A, A0, and Δ0 to the equation for obtaining the tolerance Δ in FIG. 5, and the loss costs L1 and L2 are 578 yen and 306 yen, respectively (VT is not shown but 22 μm) , Ve is the variation of the hole diameter 2 of the quality characteristic of FIG. 6 is 16 μm). Since the values of L1 and L2 obtained here are loss costs per part, if the number of parts produced is 10,000 per year, the annual loss costs L1 and L2 are 5.78 million yen and 3.60 million yen, respectively. become. Thus, the loss cost is determined in consideration of the production number.

  Next, a processing flow example of the computer 100 of the quality management system will be described with reference to FIG. First, the computer acquires quality control data sent from the sensor 200 in each process. This data is accumulated in the quality control data storage unit 170, and an average value, maximum value, minimum value, variation, and Cp value (Cp value is obtained by the above-described formula) are obtained at a predetermined timing, and a management reference value is obtained. Write to the storage unit 160 (S110, S120).

  If all the Cp values in the management reference value storage unit 160 exceed 1.33, the process ends as it is (No in S130), but there are cases where the Cp value is 1.33 or less (S130). In the case of Yes), the loss costs L1 and L2 are calculated in consideration of the annual production number by the method described above. Ranking is performed in descending order of the calculated loss cost. (S130-S150).

  Next, with respect to the control factors of the three management items ranked higher, correction values are obtained with reference to the quality engineering data storage unit 180 shown in FIG. 7 (S160).

  The loss costs of L1 and L2 ranked in S150 and the correction value obtained in S160 are displayed on the display 120. Then, the management reference value and the setting of the manufacturing apparatus are corrected based on the obtained correction value (S170, S180).

  FIG. 10 shows an example ranked with the loss cost L2 obtained in S150. FIG. 10 corresponds to the data examples of FIG. 5 and FIG. Comparing the rank of FIG. 10 with the conventional Cp value rank of FIG. 12, it can be seen that they are completely different.

It is a principle diagram of the first invention. It is a principle diagram of the second invention. It is a structural example of a quality control system. It is a structural example of the computer of a quality control system. It is an example of data of a manufacturing cost storage part. It is an example of data of a management standard value storage part. It is an example of data of a quality engineering data storage part. It is a formula for calculating the quality cost. It is an example of the processing flow of a computer. An example of ranking by annual loss cost. It is an example of the Cp value calculated from quality control data. It is an example of the ranking by the conventional Cp value.

Explanation of symbols

DESCRIPTION OF SYMBOLS 10 Manufacturing cost storage procedure 20 Management reference value storage procedure 30 Quality control data storage procedure 40 Process capability index calculation procedure 50 Loss cost calculation procedure 60 Loss cost presentation procedure 61 Loss cost presentation procedure 70 Quality engineering data storage procedure 100 Computer 110 Control unit 120 Display 130 Keyboard 140 Production plan storage unit 150 Manufacturing cost storage unit 160 Management standard value storage unit 170 Quality management data storage unit 180 Quality engineering data storage unit 190 Main memory 191 Management standard setting unit 192 Quality management data acquisition unit 193 Process capability index calculation Section 194 Loss cost calculation section 195 Correction value calculation section 196 Loss cost presentation section 200 Sensor 301 Pretreatment process 302 Water washing 1 process 303 Plating process 304 Water washing 2 process 305 Drying process 306 Inspection process

Claims (5)

Computer
A manufacturing cost storage procedure for storing the manufacturing cost for each process of the product to be manufactured;
Management reference value storage procedure for storing quality control management items predetermined for each process and management reference values including target values for the management items;
Quality management data storage procedure for measuring quality management data for the management items and storing the obtained quality management data;
A process capability index calculation procedure for determining a process capability index based on the control reference value and the stored quality control data;
The management item whose calculated process capability index is equal to or less than a predetermined value is extracted, and the loss cost in the process of the extracted management item is calculated based on the variation in the quality control data, the manufacturing cost, and the production amount of the product. A loss cost calculation procedure for determining a loss cost using a predetermined loss function for
Loss cost presentation procedure for ranking and presenting the loss cost for the determined process by the size of the amount;
The quality control method characterized by having. The loss cost is
A cost in which the value of the quality control data is corrected to be a target value of the management item and a cost in a case where a difference from the target value of the management item is not corrected.
The quality control method according to claim 1, wherein: The quality management method further includes a quality engineering data storage procedure for storing quality engineering data of an error factor that is a factor of quality variation and a signal factor that is a factor that changes quality with respect to the control factor of the management item. Have
The loss cost presentation procedure ranks the loss cost for the process obtained in the loss cost calculation procedure by the amount of the amount, and from the ranked quality control data of the loss cost and the quality engineering data The quality control method according to claim 1, wherein a correction value for the set value of the corresponding management item is obtained, and the ranked loss cost and the correction value are presented. On the computer,
A manufacturing cost storage procedure for storing the manufacturing cost for each process of the product to be manufactured;
Management reference value storage procedure for storing quality control management items predetermined for each process and management reference values including target values for the management items;
Quality management data storage procedure for measuring quality management data for the management items and storing the obtained quality management data;
A process capability index calculation procedure for determining a process capability index based on the control reference value and the stored quality control data;
The management item whose calculated process capability index is equal to or less than a predetermined value is extracted, and the loss cost in the process of the extracted management item is calculated based on the variation in the quality control data, the manufacturing cost, and the production amount of the product. A loss cost calculation procedure for determining a loss cost using a predetermined loss function for
Loss cost presentation procedure for ranking and presenting the loss cost for the determined process by the size of the amount;
Quality control program to execute. Manufacturing cost storage means for storing the manufacturing cost for each process of the product to be manufactured;
Management reference value storage means for storing a quality control management item predetermined for each process and a management reference value including a target value for the management item;
Quality management data storage means for measuring quality management data for the management items and storing the obtained quality management data;
Based on the management reference value and the stored quality control data, a process capability index calculating means for obtaining a process capability index;
The management item whose calculated process capability index is equal to or less than a predetermined value is extracted, and the loss cost in the process of the extracted management item is calculated based on the variation in the quality control data, the manufacturing cost, and the production amount of the product. A loss cost calculating means for determining a loss cost using a predetermined loss function for
Loss cost presenting means for ranking and presenting the loss cost for the determined process by the size of the amount;
A quality control system characterized by comprising:

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