Block 3 - lecture 1

Question 1

3 categories of variation?

Answer 1

• within-piece variation
• piece-to-piece variation
• time-to-time variation

Question 2

assignable sources of variation?

Answer 2

• equipment
• material
• operators
• methods
• environment
• measurements

Question 3

examples for variation from equipment?

Answer 3

• tool wear
• machine vibration
• electrical fluctuations

Question 4

examples of variation from material?

Answer 4

• tensile strength
• ductility
• thickness

Question 5

examples of variation from environment?

Answer 5

• temperature
• light
• radiation
• humidity

Question 6

examples of variation from operators?

Answer 6

• personal problems
• physical problem
• lack of training

Question 7

Size of variation due to inspection vs from other sources?

Answer 7

should be 1/10th of other sources

Question 8

causes of variation?

Answer 8

random or assignable

Question 9

control charts for variable data?

Answer 9

• Xbar and R-charts
• Xbar and s-charts
• charts for individuals (x-charts)

Question 10

Xbar charts?

Answer 10

used to plot averages for each subgroup

Question 11

Xbar chart advantage?

Answer 11

quick way to show variation

Question 12

solid line in the centre of an Xbar chart?

Answer 12

Could be:

• average of averages (X double bar)
• reference value (Xbar0)
• population mean (mu)

Question 13

dashed upper and lower lines on an Xbar chart?

Answer 13

control limits

used to judge the variation

Question 14

Control limits vs Specification limits?

Answer 14

• control limits are used to measure variation

- Spec limits are the product requirements

Question 15

How are the control limits positioned?

Answer 15

±3 standard deviations

99.73% within them

Question 16

How to determine if a process is out of control?

Answer 16

if a subgroup is out of the control limits on an Xbar chart

Question 17

R chart?

Answer 17

used to plot the range of each subgroup

Question 18

when would more/less inspections be needed?

Answer 18

More inspections are needed when the process is out of control

Question 19

what does it mean if an individual value is out of the control limits?

Answer 19

nothing, they refer to the averages

Question 20

what does it mean if a subgroup has an average out of the control limits?

Answer 20

the process is out of control

Question 21

uses of a control chart?

Answer 21

1. quality improvement
2. determining process capability
3. deciding on specifications
4. production improvement decisions
5. product release/upscaling