Download - Grip housing redesign final presentation
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DW272 GRIP HOUSING REDESIGN
GROUP 19: THE ALL NIGHTERS
SYED ELAHI, LIONEL NOUKETCHA, RICHARD HENRY,
SYED RAHMAN, NNA-AYUA OKAFOR, RYAN MILLER
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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 composedof part Polyamide, part OM6160-9
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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
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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=13.72NMomentum(at impact from 6ft drop)=13.72N*6m/s=82.2Nm/s
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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
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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.
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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.
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DESIGN PROPOSAL
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COEFFEFICIENT OF FRICTION FOR TPE TEST
Used simple “Inclined Plane” test
Measured height of wrist when the part began slipping
Trigonometry used find angle
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COEFFICIENT OF FRICTION FOR OM6160-9 BY EXPERIMENT
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COEFFICIENT OF FRICTION FOR PA6-GF33 BY EXPERIMENT
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NEW DESIGN MODEL:DEALING WITH TORQUE
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TOP GRIP TORQUE OPPOSITION MODEL:SUPPORTING MATH
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HANGING TOP GRIP DROP OPPOSITION MODEL:WITHOUT CONTOURING
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HANGING TOP GRIP DROP OPPOSITION MODEL:WITH CONTOURING
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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
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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
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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.
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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
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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.
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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