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Basics of Design I

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Design For Assembly

Integrated Baffle, Oil Pick-Up Tube and Scrapers

Mains

Lower Skirt

Integrated baffle is captured and

located by lower skirt and cranks

mains eliminating the need for

fasteners

Oil Pan

Existing baffle oil pick-up tube w/gasket and

fasteners

11 parts IntegratedInto one

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Snap-Fit Opportunities

Integrated Snap Fits

No extra part

•Simple & reliable

•Design freedom

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L

h/2

h

f

Q

F

Alpha

f = 1.09 • s • L

h

2

[mm]

Es = [MPa]s

s

Es = Secant Modulus

Snap-Fit Design

Height Width Deflection length Deflection undercut Angle Deflection force Engagement force

mm mm mm mm degree Newton Newton

h b L f Alpha Q F

POM High Viscosity 8POM Med. Viscosity 5Nylon 6.6 DAM 2-3Nylon 6.6 Cond. 4-6GR Nylon DAM 0.5-1.2GR Nylon Cond 0.9-2.0

PBTGR PBTGR PETTPC-ET

3-40.7-1.50.5-0.815-20

General case

Approx. valuesfor

[%]

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• Undercuts rounded to avoid tearing of part & stress concentration.

• Ejectors should be large to avoid penetrating the part.

• Cycle time (specially hold pressure time) should be optimum to avoid excessive shrinkage.

POM Undercut = ((B-A)/B)

£ 5%

Undercut Design

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Break energy in J/m (Izod impact strength)

V(r = 0.023 mm)

U(r = 3.2 mm)

UV

Nylon Dry as moulded

28 740 26 : 1

Nylon Cond. 2.5 % RH

34 1340 40 : 1

POM 36 310 9 : 1

Influence of notches on…Impact Strength

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Stress Concerntration Factor

3.0 2.5 2.0 1.5 1.0

0 0.2 0.4 0.6 0.8 1.0 1.2 1.4

R/T

P = Applied Load R = Fillet Radius T = Thickness

Sharp Corners

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Wall Thickness Design

Non-uniform wall thickness

Wall Section Design

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Steel

Aluminium

55% GR PET30% GR PET30% GR PBT30% GR Nylon 6.6 (DAM)30% GR Nylon 6.6 (Cond.)Nylon 6.6 (DAM)POM Med. ViscosityPOM High ViscosityNylon 6.6 (Cond.)

210.000 70.000

19.50011.00010.00010.0007.5003.3003.2003.1001.600

Tensile E-modulus for some materials

F L

3 E I

3

x-x

d =

I = B H

12x-x

3

X

Force

x

x

L

B

H

Deflection Beam Case

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140

2.8

1.8

4.0

2.0

6.0

9.2

11.2

28

Moment ofInertia forA, B and C

2520 mm3

Compared to Amaterial savings

up to 22.9 %

Compared to Amaterial savings

up to 57.4 %

A

B

C

Profile Stiffness

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1.00 0.62 0.48 0.44 0.57 0.46 1.12 0.33

Force

W

H

t H, W, t = constant

Profile 1, deformation 1Profile 2, deformation 2

No deformation

Reference Relative deformation value versus the reference profile

Deformations with a Constant Load

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1.0 1.5 13.5 14 27.3 30 28 10.5

Reference

Relative Torsion Stiffness

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Rib Designs

Rib & Sink Marks Alternative to ribs

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Aim for Aim for uniformuniform wall thickness. wall thickness.Design wall thickness Design wall thickness as thinas thin as possible and only as possible and only as thickas thick as as necessary.necessary.Use Use ribbingribbing instead of greater wall thickness. instead of greater wall thickness.Provide Provide radiusing.radiusing.Provide demoulding Provide demoulding tapers.tapers.Avoid undercuts.Avoid undercuts.Do notDo not design to design to greater precision than required.greater precision than required.Design Design multi-functionalmulti-functional components. components.Use Use economic assembly economic assembly techniques.techniques.GateGate moulding on the moulding on the thickest wall.thickest wall.

Ten rules for designers

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A Polymer for Every Application