Solve the quality of the outer surface of the 200-liter closed steel drum (2)

QC results report

Solve the quality of the outer surface of the 200-liter closed steel drum (2)

Dalian Co., Ltd.

Fifth, find the main cause of the problem

In the PDCA cycle, in order to find out the main factors affecting the quality of the paint, we went to the site to conduct research and investigation, and also held a symposium of workshop directors, team leaders and long-term paint workers. To express various opinions on various factors affecting the quality of the paint, and to discuss and discuss, and then draw a causal analysis of the unqualified paint of the 200L closed steel drum according to the reason why the proposed 25 pieces of paint are unqualified. 7).

Figure 7 200 liter closed steel barrel painting process and operation checklist

Table 7 200 liter closed steel barrel painting process and operation checklist

Adjusting the elements
Process regulations
Sun XX
Zhang XX
History XX
Liu XX
Remarks
Degreasing
Not divided
Degreasing
Not divided
Degreasing
Not divided
Degreasing
Not divided
Paint viscosity Pas
27
26
26
27
26
28
26
27
27

June 3

clear

21 ° C

Drying time h
twenty four
twenty four
twenty four
twenty four
twenty four
twenty four
36
48
72
Material quota kg
0.15
0.16
0.14
0.15
0.16
0.13
0.15
0.16
0.14
Construction method
Operating procedure
correct
correct
correct
correct
correct
correct
correct
correct
Adhesion
level 2
level 2
Level 3
level 4
level 2
level 4
level 4
level 4
level 4
Film thickness μm
20±3.0
13
17
19
16
17
15
18
16
Total output
Class production (a)
132
142
128
124
146
136
148
134
1089
Number of unqualified products (a)
11
45
9
32
14
45
12
54
222
percentage%
8.3
31.7
7
25.8
9.7
33.1
8.1
40.8
20.4%

Figure 8 voting arrangement diagram

As can be seen from the process operation checklist, most workers operate in accordance with the process requirements, and the rate of non-conforming products after the operation of the game, the de-oiled steel drum is 8.3%, and the steel drum that has not been degreased Up to 32.8%. From this operation competition, we verified the operation process of the workers, verified the equipment, and initially confirmed that the oil on the surface of the steel drum was the main factor causing the failure. From the current production situation of our factory, the front and middle stages of the 200L closed steel drum have imported equipment and patents from the United States, the United Kingdom, and the United States in the 1980s. The efficiency is high, the quality is good, and the finishing process is manual. The operation of degreasing is not only inefficient, but also inferior in quality, which is far from meeting the needs of production. Therefore, the cleaning and degreasing equipment is the key to solving the problem of painting quality outside the 200L closed steel drum.

Sixth, develop measures plan

We chose the process of alkaline degreasing and re-cleaning. Compared with the one-day process, the new process has increased the two processes of degreasing and cleaning (Fig. 9), which not only solves the problem of oil stain on the surface of the steel drum, but also solves the adverse factors affecting the quality of the steel drum surface. After cleaning, the surface temperature of the steel drum is increased, which also plays a significant role in the drying of the paint in the next process. In order to make the planned measures feasible, we have developed corresponding countermeasures (Table 8).

Figure 9 Comparison of old and new technology

Table 8 Improve the quality of the paint for the outer coating of 200 liter closed steel drum

Serial number
Cause item
aims
Measure
principal
schedule
1
Adhesion is greater than grade 3; paint film thickness is 17μm; individual 15μm; surface paint is dull; there is a large stripping phenomenon. Super national standard adhesion is less than 2 grade; paint film thickness is 20μm; surface is bright, no rust, no paint stripping phenomenon. Design and organize the construction of 200 liter steel drum degreasing equipment; carry out technical guidance; change the process; strict process discipline. Sun XX
Kang XX
Zhao XX
Liu XX June-September
2
The original record is not perfect; the test instrument lacks 20%; the workpiece factory has poor sanitary conditions and the pass rate is 50%. Every day, the original record is made for each shift; the test instrument reaches 100%; the hygiene level of the work site is over 90%. Establish and improve the original recording; establish quality information feedback; establish external paint quality science and technology files; strengthen process hygiene management; strict post responsibility system.

Kang XX
Miao XX
Liu XX

June-September
3
Paint viscosity fluctuations are too large 2-3Pas; formulate degreasing formula. The paint viscosity fluctuation is controlled at 0.5-1Pas; high efficiency and low consumption. Train the operator; learn the method of measurement and require a minimum of twice a day; the laboratory staff helps to prepare; 1-2 times a week. Wan XX
Qu XX June-July

7. Formulate countermeasures and implement measures plan

In the design, we predict the sales status of 200L closed steel drums in the next 5 years. The probability of high demand is 0.3, the probability of medium demand is 0.5, and the probability of low demand is O. 2. In order to ensure the appearance quality of steel drums and produce qualified products, there are two options: Option I: to build a new degreasing, cleaning and drying production line, which requires an investment of 200,000 yuan. Scheme II: Renovation of existing equipment Invest 30,000 yuan. The annual sales profit under various objective conditions is listed in Table 9.

Table 9 Sales profit statement (unit: 10,000 yuan)

Scheme\probability
High demand (probability 0.3)
Medium demand (probability 0.5)
Low demand (probability 0.2)
I new
200
150
50
II reconstruction
150
100
50

The decision steps for the best solution are as follows:

1. Draw a decision tree diagram, as shown in Figure 10.

2. Calculate the expected value:

The expected value of 1 point I is calculated: (0.3x 200+0.5 x150+0.2 x 50)X 5 - 20 -705 (ten thousand yuan)

Expectation of 2 points II calculation: (0.3 xiso+0.5 x 10010 0.2 x 50)x5- 3=522 (ten thousand yuan)

3. Compare the expected values ​​of point I and point II and cut off point II. In the design implementation, we found the best solution and assisted in the completion of the construction task.

Figure 10 De-oiling plan decision tree diagram

Description: â–¡ indicates the decision point. The branch from it represents the action that can be taken. â—‹ indicates the natural state point. The branch from which it is derived is a probability branch. // indicates pruning, which is eliminated.

Eight, the result is compared with the original

1. Quality result

Then, 30 steel drums were randomly sampled to measure the film thickness. According to the data (Table 10), the histogram (Fig. 11) was used to calculate the process capability index Cp=1.2, and the ideal results were obtained (Table 11). Through one cycle, the rate of non-conforming products in the 200L. closed steel drum painting process decreased from the average of 26.04% in June-September to about 3.1% (Figure 12).

2. Benefit result

1 Social benefits: The improvement of the quality of the outer surface coating not only reduces the labor intensity of workers, improves the working environment, but also changes the long-term existence of China's foreign trade exports. The status quo of first-class products and second-rate packaging has reduced claims, ensured the strong competitiveness of Chinese products in the international market, and gained good social reputation.

2 Saving value: The non-conforming product rate of the 200L closed steel barrel painting process in our factory is high for a long time. In order to ensure the quality, we have to use the secondary painting, even to the user warehouse for three times. After the process is improved, the quality is fully guaranteed by one application. In the current year, our factory produces 200L closed steel drums with a capacity of 200,000 (annual production capacity of 500,000, 40%).

Annual saving value (ten thousand yuan) = 20x5 = 1 million yuan

Table 10 Film thickness dimension measurement table (unit: μm)

20
18
20
20
twenty two
20
20
twenty one
20
19
20
19
20
20
20
20
twenty one
twenty one
twenty one
19
twenty one
twenty one
20
19
20
19
20
20
twenty one
19

Figure 11 Paint film thickness histogram

Table 11 Frequency Distribution Table

Dalian Barrel Factory
Frequency distribution table
Product number
TO11
Process verification form
Paint shop in a workshop
product name
200 liter steel drum
year month day
Process name
Painting
Group No
Group distance
Center value xi
Frequency statistics (a)
Frequency fi
Simplify the central value ui
Fiui
Fiui2
1
17.5-18.5
18
-
1
-2
-2
4
2
18.5-19.5
19
6
-1
-6
6
3
19.5-20.5
20
15
0
0
0
4
20.5-21.5
twenty one
7
1
7
7
5
21.5-22.5
twenty two
1
2
2
4
-
h=1, a=22

30

Σfi

-

1

Σfiui

twenty one

Σfiui2

Result calculation

Figure 12 Non-conforming product rate chart

IX. Standards, legacy issues and future plans

Develop a process quality management point table (Table 12) and a work instruction book. From then on, this process is regularly measured by the operator, which lays the foundation for the implementation of management chart control.

Remaining problems: the thickness of the paint film is uneven, and there are water drops on the outer surface of the steel drum, which affects the quality of the coating and is put into the next step.

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