Spar Mill Work-HolderUniversity of Idaho

2008 Capstone Project

Sponsored By Boeing

Sparmill Team:Members: Ryan Mathews, Andy Florence, Ben Puyleart.

Instructor: Jay McCormackMentors: Chris Huck, Russ Porter

2

3

Problem DefinitionBackground:•Boeing’s Auburn Plant manufactures airplane wing spars which are the primary structural component that runs the length of the wing. •The spar mill work holder secures the aluminum work piece while the mill shapes the components, which can be over 150 feet in length. •Currently, the work piece is hydraulically clamped down onto the work holder. •The current spar mill work-holder in place at the Boeing Company’s Auburn Skin and Spar Division has been causing a maintenance problem for the last 15 plus years due to hydraulic failures.

Problem:The product opportunity is to reduce the occurrence of failure in the current work-holder while maintaining clamping specifications.

4

Understanding The ProblemProblem tear down-Function chart

5

Requirements and Specifications  Specs (a.k.a Functional requirements or Voice of the company)

Requirements (a.k.a Voice of the customer or Customer requirements)

Clamping

force

Clamp spacin

g

total downtim

e Repair time

X - Accessabil

ity for repair

Service life

Fits base

dimensions

Has man

ual clam

ps

Average

clamping time

applied

force deviat

ion

provde

linear movement

stored force

in clamp

s when not in

useHold work piece in place during cutting x x             x      Maintain current clamping positions   x x                  

Reduce maintenance effort       x x              Fit in standard machine base             x       x  

Survive hostile environment           x            Support different work holders (dovetail and flat) with a common actuator base             x          Allow for the manual clamping               x        Provide signal that maintenance is needed                   x    

Safe operating environment                       xUnits of measure lb inch hr/failure min/week min/failure years in   hours lb in lbTarget values 1500 12 1 to 2 1500 10 10 7X4.6   8 200 1.5 0

6

Concept designs

7

Final DesignKey Features:Common Shaft: Rigidly connects two clamps to reduce the quantity of hydraulic cylinders

Spring System: Springs supply 1500 [lb] clamping force rather than the hydraulic cylinders

Release Arm: Allows for release of the spar. Prevents side loading of the hydraulic cylinder.

8

Final Design-Exploded View

9

Final Design-Manufactured Prototype

10

Final Design-Manufactured Prototype

11

DFMEA-(Design Failure Mode Effects Analysis)

ITEM AND FUNCTION POTENTIAL FAILURE MODE(S)

POTENTIAL EFFECT(S) OF FAILURE

SEV

CLASS

POTENTIAL CAUSE(S) OF

FAILURE

OCCUR

CURRENT DESIGN

CONTROLS

DETECT

RPN

RECOMMENDED ACTIONS

Springs IncompressibleSpars could not be released/no changeover 3 

Aluminum chips in spring housings 7

Detect failure when clamps do 3 63Change

            not open  Design chip shielding mechanism

               Quick preventative maintenance

                techniques

                   

Ensure cylinders can't apply more pressure than needed

•One example with recommended actions

12

Spring Testing

Spring rate: 430 [lbf/in]

0 0.5 1 1.5 2 2.5 3 3.5 4 4.50

200

400

600

800

1000

1200

1400

1600

1800

f(x) = 429.558823529412 x − 17.1764705882352

Force 1Force 2Linear (Force 2)Force 3

Deflection [in]

Spri

ng F

orce

[lb

f]

No hysteresis effect

13

Force TestingHydraulic pressure: 520 [psi]Cylinder Force: 2144 [lbf]Clamping Force: 1244 [lbf]Friction Effects: causing lower clamping forceFrictional Torque: 2102 [lbf*in]Clamping Force Torque: 9165 [lbf*in]Spring Torque: 11267 [lbf*in]

14

More Force Testing

15

Requirements and Specifications  Specs (a.k.a Functional requirements or Voice of the company)

Requirements (a.k.a Voice of the customer or Customer requirements)

Clamping

force

Clamp spacin

g

total downtim

eRepair

time

X - Accessabil

ity for repair

Service life

Fits base

dimensions

Has man

ual clam

ps

Average

clamping

time

applied

force devia

tion

provde

linear movement

stored

force in

clamps

when not in

useHold work piece in place during cutting x x             x      Maintain current clamping positions   x x                  

Reduce maintenance effort       x x              Fit in standard machine base             x       x  

Survive hostile environment           x            Support different work holders (dovetail and flat) with a common actuator base             x          Allow for the manual clamping               x        Provide signal that maintenance is needed                   x    

Safe operating environment                       xUnits of measure lb inch hr/failure min/week min/failure years in   hours lb in lbTarget values 1500 12 1 to 2 1500 10 10 7X4.6 y  8 200 1.5 0Measured values 1244 12 1 to 2 47 10 10 7x4.6 y 8 256 1.3 0

16

Retrofitting Cost Estimate(Per 2 Foot Section)

Rocker Arm and Shaft Assembly$510.00Pushrods $24.00Springs (2 each) $115.00Hardware (bolts/pins/chain) $40.00Spring Housing $80.00Labor $250.00Total $1019.00

(Costs in bulk would likely be considerably less)

17

Future Work/ Recommendations•Shielding of the spring and cylinder.

•Possible heat treating of common shaft and keyways.

•Improve ease of cylinder changeout (quick release fittings).

•Alter design for quick and inexpensive retrofitting of current base.

•Develop automatic safety lockout system.

18

Appendix of Photos

19

20