automotive design avoiding plastic design pitfalls©1992-2015. paul a. tres. all rights reserved....

©1992-2015. Paul A. Tres. All rights reserved.

AUTOMOTIVE DESIGN Avoiding Plastic Design Pitfalls

Paul A. Tres ETS, Inc.

Bloomfield Hills, MI

Excerpts from the 7th English edition of DESIGNING PLASTIC PARTS FOR ASSEMBLY by Paul A. Tres,

© Carl Hanser Verlag, Münich 2014


Fixing Honda Pitfall


Lower Back Comfort Zone

FORE & AFT ADJUSTMENT Provides 2” (50 mm) of infinitely adjustable fore and aft displacement

VERTICAL ADJUSTMENT Five positions allow 2” (50 mm) of vertical adjustment in 0.5” increments

Lumbar Comfort


Aftermarket Lumbar Support


Lumbar Gear Drive


• Number of gear teeth = 14 • Metric module = 1.00 • Pressure angle = 20o

• Tooth arc thickness = 1.83 mm • HOB addendum = 1.33 mm • HOB tip radius = 0.43 mm • Roll angle for loading = 42.556o

• Tooth face width = 4.5 mm • Gear input torque = 953.5 N·mm • Root diameter = 12.052 mm • Y –Lewis form factor = 0.37039 • Load tangent to base circle = 144.956 N • Load normal to tooth center line = 119.872 N • Parabola height = 1.72 • Parabola base = 1.995 • Bending moment arm = 1.422 N·mm • Load radius at center of tooth = 7.954 N

Satellite Gear Calculations


Satellite-Sun Gears FEA


Satellite Gear MSA


0 10 20 30 40 50 60 Strain, %

Stre

ss, M

Pa

Stress, kpsi

16

14

12

10

8

6

4

2

0

120

100

80

60

40

20

0

-40oC

0oC

23oC

80oC

100oC 120oC

70

Tensile Stress/Strain Curves Delrin® 111P NC010 Lot VLD5M37, ISO 11403

Polymer Used: Delrin® 111P NC010


0.04” (1 mm)

Solution


Fixing Mercedes Pitfall


Washer Fluid Bottle


PP Grade PD-626 Units

Yield Stress 4,400 psi

Yield Strain 13 %

Flexural Modulus @ 1% secant 170,000 psi

Rockwell Hardness N/A R Scale

Heat Deflection Temperature @ 66 psi 190 oF

Notched Izod Impact @ 73oF 0.5 ft∙lb/in

Water Absorption after 24 hour N/A %

Density 0.9 g/cm3

Melt Flow Rate 12 dg/min

Polypropylene Properties


Hot Plate Welding Process

Press

Press

Press

Press

Fusing area

Fixtures


Weld Joint Design

1.3t = 0.105” (2.6 mm) 0.08” (2 mm)

0.27” (6.8 mm)

0.16” (4 mm)


Bottle Volume Increased - 7.6l


Weld Joint Desired

0.16” (4 mm)


Weld Joint Achieved


Deep Draw Warpage


Blow Molding for Redesign

• 9” deep draw induces large warpage

• Increasing 5l initial volume to 7.6l compounded the problem

• Welding tried to compensate for warpage

• Creates pre-stress condition in the weld joint

Solution

Blow molding process

eliminates the design pitfall


Thank you! Questions??

automotive design avoiding plastic design pitfalls©1992-2015. paul a. tres. all rights reserved....

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