## Problem solving by 7 Quality Tools

Quality pays for itself. Without good quality no industry can survive competition. So it is very important to sustain quality of products. In this article 7QC tools explained which are widely used by automotive industries to short out problem and closing that by taking appropriate countermeasures.

### What are Seven Quality tools?

Basically 7 quality tools are problem solving tools, which are widely used in automobile industries. These problem solving tools not only used in Automotive industries but also in non-automobile sectors like service & Retail sectors.

These Quality tools work on PDCA cycle. PDCA stand for plan-do-check-act. For solution of any quality problem we follow funnel based approach, in which we identify problem severity and then define that problem (explain the real problem), we find possible causes (by using fishbone diagram) and then we find root cause of problem, then we take countermeasures then after we evaluate that countermeasure (Here we check effectiveness of counter measures) and finally we standardized it in documents for horizontally deployment for other parts.

### List of 7QC tools

1. Check Sheets

2. Pareto Chart/Diagram

3. Stratification, chart & PFD

4. Fish Bone Diagram/Ishikawa Diagram/Cause and Effect Diagram

5. Histogram

6. Scatter Diagram

7. Control Chart

### Why need of 7QC tools?

Because companies with Quality program (7QC tools, Quality Circle, PDCA, QMS, Kiazen activities) makes more profit. The 7 QC tools provide common methods of analysis

to help problem solving teams operate effectively. It helps in taking decisions faster and

objectively. Return on investment is increases. By implementing Quality tools following benefits can be obtained:-

- Improve Quality
- Decrease cost
- Improve Productivity
- Decrease/ Increase price
- Stay in business
- Provide more jobs
- Retune on investment

**Basically there are 7 steps of problem solving:-**

**1. Define the problem**

- Explain the problem [Details of problem]
- Project the losses [Effect of problem]
- Identify who will work on this [team to solve the problem]

**2. Data Collection**

- Collect the necessary data by using check sheets

**3. Analysis**

- Use appropriate QC tool for analysis like- control chart, pareto chart, fish-bone diagram, Histogram, scatter diagram, Flow diagram, etc.

**4. Action**

- Action is Counter-measure find out after analysis

**5. Study**

- Study the impact of action taken/Check effectiveness

**6. Standardize the solution**

- Standardize mean, we have to record it in documents for past learning, same countermeasure to be taken if new development, or Horizontal deployment in other similar process at different location/Country

**7. Continuum**

- Continue to look for other problem of shop floor and provide solution for the same.

### 1. Check sheet in 7QC tools

### 2. Pareto Chart in 7QC Tool

**Definition:-**

### How to make Pareto Chart?

- Arrange each problem classification in order from highest to lower in excel.
- Write down %age of overall total in next column.
- Write Cumulative %age in next column [for 1st defect defect percentage will be same as %age of overall total, for 2nd it will be sum of %age of overall total + cumulative %age of 1st one, and so on. Excel formula could be
**=$E2+D3**, and the scroll down. - Select data sheet and insert column chart.
- For Cumulative %age-change chart type to “Line with marker”.
- You can delete %age of overall total by clicking in excel

Here is Check sheet in below picture:-

Preto chart based on above data sheet will be like this:-

Left vertical axis of pareto chart has count or cost as per data. Each vertical bar represent contribution to the total, the bar at the left has highest contribution to count and cost. Each right vertical axis represent percentage demarcation. A cumulative line is used to add %age from each bar.

From above pareto chart photo we can have two understanding, first- Identification of bar which is contributing the most, here it is Dent, second- by cumulative line we determine how much of total problem will fixed by addressing the highest few.

Here pareto principle is 80% results are determined by 20% of the causes, therefore we should try to find 20% of defect which are causing 80% of all defects.

__Conclusion of pareto chart__

__Conclusion of pareto chart__

So if we take care of only Dent defects we can take care [or Reduce] of 50% problems, and if we take care of both Dent and scratch we can take care of 70% problems.

### 3. Stratification, Flow chart & PFD in 7QC tool

**Stratification**is process of data arrangement, in which we separate the data so that pattern can be seen. Because when we collect data from different section and analysis on the whole, then we can not get purpose of analysis. So we use stratification for data arrangement.

Flow Chart is visual illustration of sequence of operation, process to make a product. In flow chart we not only give name or number for process we also give some symbols which indicates action being done for different operations.

Graphs are pictorial descriptions of any data. Some of Bar graph are Bar graph, Line graph, Pie graph, Radar Graph. By pictorial description we can summaries data in very short also long data can be explained very easily by pictorial description.

### 4. Fishbone Diagram/ Cause and Effect diagram/Ishikawa Diagram

#### How we use fishbone diagram to find root cause of problem?

Mostly 5th or 4th why could be root cause, but it differ case to case.

### 5. Histogram in 7QC tool

- Future performance of process,
- Identify change in process
- Predict whether production lot with this process can meet customer requirement.

**Histogram is 7QC tool by which we can see process shape, process centering and process speared.**

### How to make Histogram?

- No of Bin/No of Bar/No of Classes [All same thing]
- Width of Bin/Bar/Class
- Class Boundary

- No of Bin/No of bar/No of Classes are dependent upon number of data measured. It could be represented by [k], generally it is square root of Number of data. Here number of data is 100, so No of class/No of bin/No of Bar would be 10.
- Class width can be calculated by Dividing Range [Max observation-Min observation] by No of Bins. It will be 220-190=30, and 30/10=3.
- Class Boundary is table in which first value is minimum observation, which is 190. Second will be 190+3=193, and go on adding till all measurement placed in their classes.

**=FREQUENCY(A3:J12,D17:D27),**here D17 is 190, and D27 is 220.

No value is out of spec, maximum was 210, and minimum was 190. Here we calculate frequency count for histogram, we obtain below result:-

And histogram will made on the basis of above data, for that we will first insert bar chart, then we will select data and scroll down under frequency count. Next will be class boundary on x-axis, that is all.

From the above Histogram, we can see frequency distribution is normal, which indicate variation is zero, and values are more about mean.

Standard deviation is amount of variation within data range. More standard deviation mean more variation and less value of standard deviation is less variation. It is represented by sigma. It is generally spread, which indicate average distance of individual number with respect to mean. if we have to calculate standard deviation of 1, 2, 3 mean will be 6/2=3 and standard deviation will be under square root (1-2)²+(2-2)²+(3-2)²/3 = 1.

### 6. Scatter Diagram or Scatter Plot in 7QC tool

Scatter diagram will be plotted between HRB &TS, HRB will be on X-Axis and TS will be on Y-Axis. Here just ignore Red values in above picture.

From the above scatter diagram we see there is positive correlation between HRB and TS, since all points are closer to line. Various types of scatter plot is as below:-

- If R>0-it indicate there is positive linear relation
- If R<0- It indicate there is negative linear correlation.

### 7. Control Chart in 7QC tool

- If no value go out of UCL & LCL.
- Most points are close to average
- Equal number of point below or above center line

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