Transcript DCDOV Process for DFSS

DFMA – Design for Manufacture
and Assembly
Shin Ta Liu
Ph.D. CSSBB, CQE, CRE
Principal Consultant
Lynx Systems
12529 Cloudesly Dr
San Diego, CA 92128
Web site: www.lynxsys.net
Email : [email protected]
Phone: 858-366-4951
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DFSS Process
DCDOV
Goals
Tools
Define
Obtain customers needs and wants
Translate customers needs and
wants to VOC list
Market/Customer Research, Kano
analysis, stakeholders analysis,
operation cross walk
Concept Development
Develop Design
Feature/functional requirements
based on VOC
QFD. TRIZ, Axiomatic Design
Design Development
Identify engineering and
process parameters based on
the design features/functional
requirements
CTX, DFX, DOE, Taguchi
methods
Optimize Design
Identify optimal settings for the
engineering and process
parameters based on the
performance, robustness,
production and other
requirements.
RSM, FMEA update, sensitivity
analysis, Taguchi Methods
Verify Capability
Establish the designed
product/process is capable of
meeting the design target and
requirements.
Verification/qualification tests,
validation tests, simulation,
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statistical analysis
DFMA process
Start
Design for
Assembly
Physical, Process structure,
transfer function specifications
Specify material,
process and early
cost estimate
Recommend improved
materials and process
Select the best
assembly process
structure
Design for
Manufacture
Detailed Design for Minimum
manufacturing costs
Prototype
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DFMA Algorithm
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Determine criticality of a part
a part is critical if
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–
–
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- move relative to all other parts already assembled, or
- different material than all being assembled
- separated from other parts assembled.
Physical coupling of “un-critical” parts with a “critical
part”
Reassess assembly time for new configured parts
Analyze the manufacturability of new configured part
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DFMA Example
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DFMA-Example 1 Analysis
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DFMA Worksheet for Datum Design
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Item
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Base
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1
•
1
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3.5
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2.9
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Bush
•
2
•
0
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12.3
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10.2
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Motor Subassembly
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1
•
1
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9.5
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7.9
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Motor Screw
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2
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0
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21.0
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17.5
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Sensor Subassembly
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1
•
1
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8.5
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7.1
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Setscrew
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1
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0
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10.6
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8.8
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Standoff
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2
•
0
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16.0
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13.3
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End plate
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1
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1
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8.4
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7.0
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End-plate screw
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2
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0
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16.6
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13.8
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Plastic bush
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1
•
0
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3.5
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2.9
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Thread lead
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-
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-
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5.0
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4.2
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Reorient
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-
•
-
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4.5
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3.8
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Cover
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1
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0
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9.4
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7.9
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Cover Screw
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4
•
0
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34.2
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26.0
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TOTALS
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19
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4
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160.0
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133.0
Number
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Theoretical Part
Count
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Assembly Time(s)
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Assembly Cost
(cents)
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DFMA Example 1 Analysis
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Total actual assembly Time T1= 163 s
Theoretical total part count is 4 and average
assembly time is 3 s. Theoretical assembly
time T2= 4 x 3 s = 12 s
Calculate Design Efficiency :
 
T2
12 s

 0.07362
T1
163s
or 7.362%
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DFMA Recommended
redesign
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Bushes are integral to the base
Snap-on plastic cover replaces standoff
,cover ,plastic bush, six screws.
Using pilot point screw to fix the base,
which redesign to be self-alignment.
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DFMA- An Improved Design
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DFMA Worksheet for an Improved Design
Item
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Base
•
1
•
1
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3.5
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2.9
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Motor
Subassembly
Motor Screw
•
1
•
1
•
4.5
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3.8
•
2
•
0
•
12.0
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10.0
•
1
•
1
•
8.5
•
7.1
•
Sensor
Subassembly
Setscrew
•
1
•
0
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8.5
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7.1
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Thread leads
•
-
•
-
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5.0
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4.2
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Plastic Cover
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1
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0
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4.0
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3.3
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TOTALS
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7
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4
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46.0
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38.4
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Number
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Theoretical
Part Count
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Assembly
Time(s)
Assembly Cost
(cents)
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DFMA Cost Differential Worksheet
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New Design
Cost,$
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Item
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Cost, $
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12.91
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Base (nylon)
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13.43
Bush(2)
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2.40
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Motor Screw(2)
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0.20
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Motor Screw(2)
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0.20
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Setscrew
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0.10
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Setscrew
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0.10
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Standoff(2)
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5.19
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Endplate
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5.89
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End-plate Screw
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0.20
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Plastic bush
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0.10
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Cover
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8.05
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Plastic Cover (include
tooling)
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8.00
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Cover screw(4)
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0.40
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Totals
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35.44
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21.73
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Old Design
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Item
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Base (Aluminum)
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DFMA –Calculate Total Saving
Total Saving =
Saving from Assembly Time Reduction
+ Saving from parts reduction
= $0.95 + $13.71
= $14.66
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Improved Assembly Design Efficiency
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Total actual assembly Time T1= 46 s
Theoretical total part count is 4 and average
assembly time is 3 s. Theoretical assembly
time T2= 4 x 3 s = 12 s
Calculate Design Efficiency :
T2 12s
 
 0.26087
T1 46s
or 26.087%
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Design for Assemblability &
Manufacturability
-Summary
Design Guides:
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Minimize the number of setup and stages.
Analyze the existing manufacturing and assembly function.
Revisit the physical structure (of the design) which customize
to the local processing capability
Apply the most appropriate (not latest) technology.
Use Axiomatic design to create Modular design of the parts.
Design for minimum number of parts using physical coupling
Choose the appropriate material for easy manufacturing
Apply the layer assembly principles.
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