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Application of Failure Mode and Effect Analysis to the Powder Coat
Process
Joan Burtner
Department of Mechanical and Industrial EngineeringMercer University, Macon, GA
Paint Cell Project
• Interdisciplinary team– Industrial management– Industrial engineering
• Technical advisor - Joan Burtner
• External client – Georgia manufacturer – Practices Six Sigma philosophy
Presenter: Dr. Joan Burtner, Mercer University 2
Powder Coat Process Overview• Material - powdered paint• Two basic application methods
– Part is lowered into a fluidized bed of the powder, which is electrostatically charged
– Powdered paint is electrostatically charged and sprayed onto the part
• Curing – Part placed in an oven - powder particles melt and
form a continuous film
Presenter: Dr. Joan Burtner, Mercer University 3
Powder Coat Equipment
• Spray Gun Corona charging guns -electric power used to
generate the electrostatic charge Tribot charging guns - electrostatic charge
generated by friction between the powder and the gun barrel
“Bell” charging guns -powder charged by being "flung" from the perimeter of the "bell
Presenter: Dr. Joan Burtner, Mercer University 4
Powder Coat Facility
TypicalSprayBooth
Courtesy: www.thefabricator.com
Accessed March 12, 2004
Presenter: Dr. Joan Burtner, Mercer University 5
Quality Issues
• Surface preparation• Operators
– Training– Skill
• Coverage• Color change• Cleanliness/ contamination
Presenter: Dr. Joan Burtner, Mercer University 6
Preliminary Process Map
Presenter: Dr. Joan Burtner, Mercer University 7
Load
Wash
Unload
Paint
Cure
Dry
Rework Accept
Key Customer Requirements
• Minimal paint thickness
• Even coverage
• Scratch-free parts
Presenter: Dr. Joan Burtner, Mercer University 8
# Process Step
Process
Input
Paint
Thickness
Even
Coverage
Damage
FreeTotal
Customer Imp 7
Customer Imp 9
Customer Imp 10
1 Load Hook 3* 3 3 78**
2 Load Conveyor 3 3 3 78
3 Paint Spray Gun 9 9 1 154
4 Cure Temp 3 3 1 58
Presenter: Dr. Joan Burtner, Mercer University 9
Cause and Effect Matrix
* Correlation values 0, 1, 3, 9 **Sample calculation 7*3+9*3+10*3=78
Control Charting Deliverables
• Target Factor - paint thickness• Data collection plan• Documentation of plan as standard operating
procedure• Control chart training materials• Control charts of baseline data
Presenter: Dr. Joan Burtner, Mercer University 10
Control Charting Locations
• Factor - paint thickness
• 5 locations• Repeated measures• 25 samples for
baseline chart
Presenter: Dr. Joan Burtner, Mercer University 11
North
West Middle East
South
Control Charting Sample Preliminary
• Range not in control
252015105Subgroup 0
4.54.03.53.02.52.01.51.00.5
0.0
Sam
ple
Mea
n
1
6 5 5 6 5 6
1
Mean=1.818
UCL=3.186
LCL=0.4504
6
5
4
3
2
1
0
Sam
ple
Ran
ge
1
1
R=0.7272
UCL=2.376
LCL=0
Xbar/R Chart f or SB
Presenter: Dr. Joan Burtner, Mercer University 12
Control Charting Sample Results - Revised
• Range in control Xbar not in control
2010Subgroup 0
3.5
2.5
1.5
0.5
Sam
ple
Mea
n
51 1
15
12
2
56 6
65
22
2
1
Mean=1.698
UCL=2.511
LCL=0.8855
1.5
1.0
0.5
0.0
Sam
ple
Ran
ge
R=0.4322
UCL=1.412
LCL=0
Xbar/R Chart f or SBrev ised
Presenter: Dr. Joan Burtner, Mercer University 13
Designed Experiments
• Dependent variable - paint thickness• Factor 1 - location• Factor 2 - shift• Statistical software package - Minitab
Presenter: Dr. Joan Burtner, Mercer University 14
Failure Modes and Effects Analysis (FMEA) Techniques
• 48 process steps selected for investigation• 4 experts polled
– Operators– Management
• Ratings entered into basic FMEA worksheet• RPNs calculated• Process steps ranked by RPN (high to low)
Presenter: Dr. Joan Burtner, Mercer University 15
Failure Modes and Effects Analysis - Category Ratings 1
• Severity of Effect (10-1)– Hazardous without warning– Hazardous with warning– Loss of primary function– Reduced primary function performance– Loss of secondary function– Reduced secondary function performance– Minor defect noticed by most customers– Minor defect noticed by some customers– Minor defect noticed by discriminating customers– No effect
Presenter: Dr. Joan Burtner, Mercer University 16
Failure Modes and Effects Analysis - Category Ratings 2
• Likelihood of Occurrence– 9 Very High: Almost inevitable– 7 High: repeated failures– 4 Moderate: Occasional failures– 2 Low: Relatively few failures– 1 Remote: Failure is unlikely
Presenter: Dr. Joan Burtner, Mercer University 17
Failure Modes and Effects Analysis - Category Ratings 3
• Ability to Detect (10-1)– Cannot detect 10– Very remote chance of detection– Remote chance of detection– Very low chance of detection– Low chance of detection– Moderately high chance of detection– High chance of detection– Very high chance of detection– Almost certain detection 1
Presenter: Dr. Joan Burtner, Mercer University 18
Risk Priority Number Example Calculations
• Paint Material – accident or transport failure– Potential Failure Effect
• Lack of paint consistency• Severity of Effect rating 4
– Potential Cause• Dropped powder• Likelihood of Occurrence rating 3
– Current Control• Lifting procedures• Ability to Detect rating 3
• Severity*Likelihood*Detection = 36 = RPN
Presenter: Dr. Joan Burtner, Mercer University 19
Failure Modes and Effects Analysis Results
• Ratings ranged from 300s to 20s• Uncontrolled process steps eliminated• Critical controlled process steps
– Powder application - operator – Cure process– Powder application - spray gun– Loading– Unloading
Presenter: Dr. Joan Burtner, Mercer University 20
Control Plan Worksheet• Critical to Quality (CTQs) factors listed according
to RPN ranking• Process step as listed in process map• Inputs/outputs• Process specifications• Measurement system• Current control plan
– Control method– Who– Where– When – Reaction plan
Presenter: Dr. Joan Burtner, Mercer University 21
Control Plan Follow-up
• Revision of current standard operating procedures (SOP)
• Establishment of standard operating procedures for CTQs that do not already have an SOP
• Periodic review
Presenter: Dr. Joan Burtner, Mercer University 22
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