4. DFMEA-Power Window Motor - VEM

1.1Proprietary of VEM technologies pvt ltd. Hyderabad , india

DFMEA of

power window Motor

PWM


Objective

To prepare Design Failure Mode & Effects Analysis

For

Power Window Motor

PWM


Team members

M.Viswanatha Reddy

T.Laxmi Narayana

CHV Rama Rao

N.Nanja Reddy

R.Balaji Singh

KVR Varma

PWM


Product Overview PWM

Function:When motor is input powered, dc motor rotates and drives the worm gear assembly and shaft with the required torque. This mechanism is capable to rotate in CW and CCW direction based on window travel requirement

Application:Used in automobile (car) power window application to raise / down the window glass


Product Requirements

1. End user requirements:1.1 Window opening1.2 Window Closing1.3 Safety trip after closing1.4 Safety trip after opening1.5 Life of product

2. OEM requirements2.1 Mounting requirements2.2 Wiring harness2.3 Life of product 2.4 Reliability of product

3. Product requirements 3.1 CTQ’s of function3.2 CTQ’s of process3.3 CTQ’s of DFMA

Product requirements are identified in the following three waysEnd User requirementsCustomer (OEM) requirementsProduct requirements

PWM


Probable Design failure modes

1. Window is not closing (lifting) /opening (down)2. More noise while closing / opening.3. Load is not taking (stopping by keeping hand).4. Jerk while opening / closing.5. Tripping of motor6. Less life / Durability

Problems are listed based on power window lifter failures only

PWM


PWM

1. Window is not closing (lifting) /opening (down)

Failure-1

1. Function : Is to lift/down the window glass of car.

2. Failure mode: Window is not closing (lifting) / Opening (down)

3. Effect : Inconvenience and lack of safety

4. Cause: 1. Worm slip over knurling due to less interference2. Centre distance between gear and worm (slipping)3. Gear tooth broken due to less strength


PWMFailure-2

1. Function : Less noise (50dB) while operating

2. Failure mode: More noise while closing / opening

3. Effect : Inconvenience and less life

4. Cause: 1. Cogging torque at armature (due to no skew)2. Burr on Worm or Gear teeth3. Dust at Bearings and armature4. Unbalance in armature winding

2. More noise while closing / opening.


PWMFailure-3

1. Function : To raise the window with 6 kg load

2. Failure mode: Load not taking (stopping by keeping hand)

3. Effect : Some times window cannot lift.

4. Cause: 1. Less output Torque due to less magnetic flux of magnet2. Less output torque due to friction at bearings (dimensions)3. Less Torque between Worm & shaft knurling.

3. Load is not taking (stopping by keeping hand).


PWMFailure-4

1. Function : Smooth operation of window up / down

2. Failure mode: Jerk while opening and closing

3. Effect : Noise and inconvenience

4. Cause: 1. Few Gear tooth wornout2. Worm tooth damage3. Coupling plate slipping due to more play or more stack play

4. Jerk while opening / closing.


PWMFailure-5

1. Function : Safety trip after full travel of window.2. Failure mode: Intermediate stop

3. Effect : Inconvenience & Lack of safety

4. Cause: 1. Due to wrong PTC from vendor (mixup)2. Window travel obstruction due to external factors3. Overheat at motor due to less winding at armature

(due to miss operation)

5. Intermediate stop (Tripping of motor)


PWM

DFMEAItem/

ProcessStep

Potential Failure Mode

PotentialEffect(s)

Of Failure

SEV Potential Cause(s) Of

Failure

OCC

Current Controls

DET RPN

Window is not closing /

opening

Inconvenience & lack of

safety

8 Worm slip over knurling

4 100% functional test

(factor of safety > 2)

3 96

CD b/w gear & worm (slipping)

4 CD critical control3 96

Gear tooth broken due to less strength

2 Gear material chosen for high strength (PBT-40% GF)

3 48

More noise while

closing/opening

Inconvenience & Less life

5 Cogging torque at armature

4 Providing skew for armature

100% inspection

4 80

Burr on worm or gear teeth

6 Two stage arc cut and visual control

4 120

Dust on bearings & armature

4 Demagnetization till cap assy

3 60

Unbalance in armature winding

4Less unbalance on

OD (100% balancing)

3 60

Critical failures identification


PWM

Load is not taking

Window can’t lift

8 Less O/P torque due to less magnetic flux

3 100% inspection of magnetic flux

3 72

Less O/P torque due to friction at bearing

3 Oil less bush with turbine 90 Oil

4 96

Less torque b/w worm & Shaft Knurling

3 More interference & knurling pitch

3 72

Jerk while opening / closing

Noise & convenience

5 Few Gear tooth worn-out

2 More tooth in contact

3 30

Worm tooth damage

3 Process handling (strength factor >2)

3 45

Coupling plate slipping due to more play or more stack play

3 Circlip at end and more bush guiding

2 30

Intermediate stop

Inconvenience & lack of safety

7 Due to wrong PTC from vendor (mix-up)

3 Steel based instead of copper base (resistance)

3 63

Window travel obstruction due to external factors

3 Gasket at cap to avoid water and dust entry

3 63

Overheat at motor due to less winding at armature (due to miss operation)

3 Performance robustness to 2% winding variation

3 63


PWM

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4. DFMEA-Power Window Motor - VEM

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