SPC Case Study, IMEN371 Quality Management, POSTECH Presented at October, 2019

1. SPC Case Study
“Coffee Mix”
품질경영 ASSN2 7조
산업경영공학과 20170425 김우찬
산업경영공학과 20170932 공도현
산업경영공학과 20170947 이준희

2. 2
1. Introduction: Case study topic, Background
2. Process and result of data gathering
3. Process and result of SPC
and capability analysis
4. Conclusions and Recommendations
5. Lessons learned

3. 3
• Coffee is the second most popular drink for Korean nations,
after water and grain tea.
• The annual coffee consumption for 20s and older surpassed
400 cups(Jeon, 2017).
• Coffee mix is the largest share of the entire coffee market.
• The coffee mix is the largest in the coffee market with 1.05
trillion won(Kang, 2016).
The ranking considered in the intake is
Taste > Brand > Raw Materials
(Korea Consumer Agency, 2014).
Taste
56.5%
Brand
27.7%
Raw
Materials
13.4%
Calories
1.1%
Caffeine
Content
1.3%
321 339
382 386
413
2012 2013 2014 2015 2016
Annual coffee consumption for aged 20+
State 1. Coffee Consumption is getting higher. State 2. Taste is the most important factor
for coffee mix.

4. 4
The concentration & weight of coffee mix is the main factor for determining flavor,
which is the first ranked factor for consumer factor of coffee mix.
The company(Namyang) proposes a standard concentration of coffee mix(French cafes)
at 80 ml to 100 ml of water per 10.9 g of coffee mix(figure at below).
In other words, the weight of coffee mix in a stick affects the taste of coffee.
So in this project, our team is looking at the weight of the coffee mix.
✓ Is Coffee Mix(French café) produced at a constant weight (10.9 g)?
By measuring the process capability, examining the quality control of coffee mix
and further suggesting the direction of quality development of coffee mix will be proceeded.

5. Common & Assigned cause in Manufacturing
5
We looked for possible Common & Assigned causes
during the manufacturing process of the coffee mix in relation to our topic(weight).
• The schematic drawings of the process were compiled in an article from Lee (Lee, 2012).
* It has been considered that there will be no causes related to weight in the process prior to this process.
Grinding Extraction & Dry Packaging
<Assignable>
<Common>
- Foreign substances during
the grinding process
- Time to run the grinder
- Insufficient moisture removal
- Difference in the size of the
particles in the previous grinding
process
- Entrance size of
packing stick
- Failure to control
packing content
- Beans’ characteristics
*
- Drying environment
(humidity, temperature) - Packaging Cutting Mistake

6. 6
• Data gathering methods
• Randomly select 100 coffee mix sticks from the 300
sticks-box product and weigh them as shown in the
picture.
• Criteria for Weight
• The definition of weight of the coffee mix is
the weight Content in a stick.
• Data Sampling
• After the raw data has been made,
sampling is proceeded.
• Sample Size = 5
• Coffee mixes are mass-produced, the expected
costs of improving the assignable cause are very
high. So the sample size is chosen as 5.
• # of Sample = 20
• Though the single data is not a single process, it
can be considered as reflecting the process
since it merges the results of several process.△ Measuring the weight of the coffee mix

7. 7
X1 X2 X3 X4 X5
Sample #1 10.8 10.9 10.8 10.8 10.9
Sample #2 10.8 10.9 10.9 10.9 10.9
Sample #3 10.9 10.9 10.8 10.8 10.8
Sample #4 11 11 10.9 10.9 10.9
Sample #5 10.9 10.9 11 11.1 11
Sample #6 10.9 10.9 11 10.9 10.9
Sample #7 10.9 10.9 10.8 10.9 10.9
Sample #8 10.9 11 10.8 11 10.9
Sample #9 10.9 10.9 10.8 10.8 11
Sample #10 10.8 10.9 10.9 11 10.9
Sample #11 11 10.9 11.1 10.9 10.9
Sample #12 11 11 10.9 10.9 10.9
Sample #13 10.8 10.8 10.9 10.8 11
Sample #14 10.9 10.9 11.1 10.9 11
Sample #15 10.9 10.9 11 10.9 10.8
Sample #16 10.8 10.9 10.9 11.1 10.9
Sample #17 10.8 10.9 10.9 10.9 10.8
Sample #18 11 11 10.8 10.8 10.8
Sample #19 10.9 10.9 10.9 11 10.9
Sample #20 11 10.8 10.9 11 10.9
△ Gathered & Sampled Data

8. • 1 point > 3 standard deviations form CL
: It is the basic option for control charts.
• 9 points in a row on same side of CL
: It means that mean shift has occurred. We can think it is out of control.
• 6 points in a row, all increasing or all decreasing
: We thought this is occurred because an assignable cause affected.
• 14 points in a row, alternating up and down
: Repeating increases and decreases over 14 times is a periodic assignable cause.
8△ R Chart Setting Options △ X-bar Chart Setting Options

9. 9
# of sample = 20
Total mean = 10.905
Standard Deviation = 0.3077
LCL =10.8127, UCL = 10.9973
✓ The first R chart was at in-control state
✓ Every samples were in between LCL and UCL.
✓ X-bar Chart was also at in-control state.
➢ Typically, occurring out-of-control eliminates out-of-control points after
finding assignable causes of the points, and repeating it until getting into
in-control state.
➢ However, the first-made R and X-bar chart were already in-control state.
➢ Standard Deviation is low. It means value of sample are distributed narrowly.

10. 10
✓ Normality test results within the Kolmogorov-Smirnov test showed that
P-value was > 0.15 and accept H0(null hypothesis).
✓ Thus, process capability analysis is possible.
The data set should be confirmed as it is normal distribution before process capability analysis.
<Kolmogorov-Smirnov Test>

11. 11
• Quality characteristic : N-type
• The concentration of coffee is the main factor for determining flavor, which is the first ranked
factor for consumer factor of coffee mix.
• The concentration is will be primarily determined by the weight of coffee mix.
• 𝑪 𝒑𝒌
• 𝑪 𝒑𝒌 represented with 0.42
• If we had used a more-detailed scale, we could have obtained a higher 𝑪 𝒑𝒌 value.
①
② ①
②

12. 12
Topic Selection
• Topic Selection;
The weight of coffee mix is the important factor
in determining the taste of coffee.
• We decided to define 𝑪𝒑𝒌 of coffee mix(French
cafes)
Data gathering & Construction of Control Chart
• Data gathering
• Total : 100
• Sample Size = 5, # of sample = 20
• The first-made R and X-bar chart were already
in-control state.
• Standard Deviation is low. It means value of
sample are distributed narrowly.
Process Capability
• Normality Test
• Kolmogorov-Smirnov test reveals that the data is
normally distributed
• Computing Process Capability
• Quality characteristics : N-type
• LSL: 10.8127g , USL: 10.9973g
• 𝑪𝒑𝒌: 0.42

13. 13
1. Reduce the size of particles
• To reduce the deviation in weight of coffee mix, it is recommended to reduce the size
of the coffee mix particles.
• Reducing the size of the particles allows management for weight on a detailed scale.
• Therefore, the effect of reducing deviation in coffee mix mass can be seen.
2. Controlling Environment of previous processes
• The manufacturing processes associated with weight were in the final phases.
• In other words, the distribution of the final weight of the coffee mix should be minimized
through the management of precise manufacturing processes.

14. • Construction of Control Chart
• We were able to draw the R chart and X-bar chart using the data of control.
• Common & Assignable cause
• The process of producing coffee mix was investigated. It was going through a very complicated
and systematic process. Each process would have common and assignable cause,
but it was not easy to know all cause. In other words, it is hard to find all cases of variation.
• Companies’ Quality tests
• When looking at the charts in the process of this project, the company may have completed
quality tests. It leads to the fact that the company is making efforts to manage quality to sell
products on the market.
• Minitab software
• Minitab enabled various analyses and statistical inspections of the data.
14

15. 15
French Café Specification
http://company.namyangi.com/product/product.asp?cd=6
Jeon, E. (Ed.). (2017, May 24). 377 cups of coffee per adult in Korea, drink at the
company after lunch! Retrieved from
http://www.sommeliertimes.com/news/articleView.html?idxno=5178.
Kang, J. (2016, November 22). Change in the market for instant coffee...the rapid
growth of coffee beans. Retrieved from
https://www.yna.co.kr/view/AKR20161122162600030.
Korea Consumer Agency. (2014). 커피믹스 품질시험 결과보고서. 시험결과보고서, 4-38.
Lee, J. (2012, December 26). ‘100 won café’ Coffee mix, 30 years of knowhow?
Retrieved from
http://m.mtn.co.kr/news/news_view.php?id=2012122610590434308#_enliple.