DW272 GRIP HOUSING REDESIGN

GROUP 19: THE ALL NIGHTERS

SYED ELAHI, LIONEL NOUKETCHA, RICHARD HENRY,

SYED RAHMAN, NNA-AYUA OKAFOR, RYAN MILLER

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

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

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

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

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.

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.

DESIGN PROPOSAL

COEFFEFICIENT OF FRICTION FOR TPE TEST

Used simple “Inclined Plane” test

Measured height of wrist when the part began slipping

Trigonometry used find angle

COEFFICIENT OF FRICTION FOR OM6160-9 BY EXPERIMENT

COEFFICIENT OF FRICTION FOR PA6-GF33 BY EXPERIMENT

NEW DESIGN MODEL:DEALING WITH TORQUE

TOP GRIP TORQUE OPPOSITION MODEL:SUPPORTING MATH

HANGING TOP GRIP DROP OPPOSITION MODEL:WITHOUT CONTOURING

HANGING TOP GRIP DROP OPPOSITION MODEL:WITH CONTOURING

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

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

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.

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

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.

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