ENME371: Product Engineering and Manufacturing, Final Design Presentation (Group), DW272 DeWALT Drywall Scrugun Grip Redesign. All rights and ownership of both the DW272 and our group's proposed changes belong to DeWALT and/or its parent companies.

1. DW272 GRIP HOUSING
REDESIGN
GROUP 19: THE ALL NIGHTERS
SYED ELAHI, LIONEL NOUKETCHA, RICHARD HENRY,
SYED RAHMAN, NNA-AYUA OKAFOR, RYAN MILLER

2. INTRODUCTION
Proposal to redesign grip contact section of DeWalt DW272 Drywall
Screwdriver in order to reduce grip force necessary for operations
Top grip composed of Polyamide
Pistol Grip composed
of part Polyamide,
part OM6160-9

3. SUMMARY OF COMPONENT REDESIGN
The areas of the grip handle in contact with a user’s hand will be
redesigned for optimal friction achieved through:
 Redesigned surface texture
 Addition of OM6160-9 around full contact area on upper and lower grip
positions
 Increased upper lip width
Ultimate goal of requiring less grip (normal force) from user
Results in less user fatigue over long durations of use

4. INTRODUCTION TO SUBSYSTEM
The Switch and Housing are vital components
for efficiency and performance
• Fits the user’s hand comfortably for extended use
• Designed for ease of use and quick application
• Housing must be durable enough for harsh work environments
Function of component
• Designed and composed for optimal friction, allowing
User to focus on the tasks for extended periods of time
• Composed of material to withstand drops and significant
Impact on jobsite.
Force(avg. at impact) = 1.4kg*9.8m/s=13.72N
Momentum(at impact from 6ft drop)=13.72N*6m/s=82.2Nm/s

5. CURRENT DFM INFORMATION
Material
 Upper grip is simply composed of PA6GF33
 Pistol casing is composed of PA6GF33, backend wrapped In OM6160-9
Approximate manufacturing cost for component
 Material cost: $8,188
 Mold cost: $30,320

6. DFM ISSUES ADDRESSED
 Back of the field case maintains uniform thickness
 By introducing through holes and snap fits secondary and finishing operations
have been reduced as much as possible.

7. ISSUES WITH CURRENT DESIGN
Low coefficients of friction in upper grip due to:
 Material Choice
 Surface Finish
 Small upper lip dimensions
As a result, the user must apply more force which can cause the user to fatigue
quicker over time.

8. DESIGN PROPOSAL

9. COEFFEFICIENT OF FRICTION FOR TPE TEST
 Used simple “Inclined Plane” test
 Measured height of wrist when the part began slipping
 Trigonometry used find angle

10. COEFFICIENT OF FRICTION FOR OM6160-9
BY EXPERIMENT


11. COEFFICIENT OF FRICTION FOR PA6-GF33
BY EXPERIMENT

12. NEW DESIGN MODEL:
DEALING WITH TORQUE

13. TOP GRIP TORQUE OPPOSITION MODEL:
SUPPORTING MATH


14. HANGING TOP GRIP DROP OPPOSITION MODEL:
WITHOUT CONTOURING


15. HANGING TOP GRIP DROP OPPOSITION MODEL:
WITH CONTOURING


16. MATERIAL
Polyamide PA6-GF33 base
 High tensile strength, elasticity,
resistance to abrasion
 Entire housing is composed of this
material in order for it to withstand
harsh working environments
Versaflex™ OM6160-9 outer
finish
•
•
•
Thermoplastic elastomer with a soft
rubbery grip
Molded to encompass all possible points
of grip contact
Provides excellent grip and friction in all
desirable positions between user’s hand
and tool

17. MANUFACTURING PROCESS
•Plastic Injection Molding
•Used to make the polyamide section of the field case and handle
cover
•Over Mold Injection
•Used to add the TPE surface to the plastic components
•Plastic for the handle and field case is molded in a PIM machine
•Thermoplastic Elastomer (TPE) injected with a secondary mold over-top
the newly shaped plastic handle
•Process is typically used to add better interfaces to housing systems
•The TPE used for the DW272 is specifically designed to bind to the type
of plastic the housing is made of

18. DFM ISSUES ADDRESSED BY PROPOSED
DESIGN
 One DFM guideline we followed is we
maintained smooth transition. We do not have
any stepped thickness transition
 In our proposed design, we have maintained
adequate draft angles wherever applicable.

19. COST COMPARISON
Factors
Old Handle Cover
New Handle Cover
New Field Case
Volume (in3)
0.4181
0.6272
0.3727
Tolerance (in)
Low (<= 0.02)
Low (<= 0.02)
Moderate (<= 0.01)
Surface Roughness Not Critical(Ra > 32) Not Critical(Ra > 32) Not Critical(Ra > 32)
Complexity
Very Simple
Simple
Simple
Part Weight (oz)
0.27
0.40
0.24
Production Rate
(per hour)
413
413
395
Material Costs
$3,500
$5,018
$3,170
Production Costs
$6,871
$6,871
$7,176
Tooling Costs
$10,897
$17,067
$13,253
Total
Manufacturing
Costs ($)
$21,268
$28,956
$23,600
*100,000 parts produced; 5% defect
rate; ABS-GF10 material for all @
$1.39/lb

20. CONCLUSION
A redesigned surface finish and replacement of contact areas
with OM6160-9 material will decrease user fatigue and increase
user performance.
 User’s increased comfort and performance satisfaction.
 Users operate more efficiently. No waste of excess energy on the job.
 Comfortable in the hand for extended periods of time.
 Cost effective to implement, manufacture and produce.

21. IMAGE SOURCES AND SOME PRIMARY
REFERENCES
http://www.engr.sjsu.edu/minicurric/images/lecture_powerpoints/DFMA_II_Design
_Guidelines.pdf
http://en.wikipedia.org/wiki/File:Polycaprolactam.svg
http://www.custompartnet.com/materials/
http://www.materialdatacenter.com/
Dieter, George Ellwood., and Linda C. Schmidt. Engineering Design. 5th ed. Boston:
McGraw-Hill Higher Education, 2009. Print.
http://catalog.ides.com/datasheet.aspx?I=47200&FMT=PDF&E=75180