basics of design i
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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 andfasteners
11 parts
Integrated
Into 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 es L
h
2
[mm]
Es = [MPa]sses
Es = Secant Modulus
Snap-Fit Design
HeightWidthDeflection lengthDeflection undercutAngleDeflection forceEngagement force
mmmmmmmmdegreeNewtonNewton
hbLfAlphaQF
POM High Viscosity 8
POM 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
PBT
GR PBTGR PETTPC-ET
3-4
0.7-1.50.5-0.815-20
General case
Approx. valuesfor
e [%]
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Undercuts rounded to
avoid tearing of part &
stress concentration.
Ejectors should be
large to avoidpenetrating 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 onImpact Strength
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Stress
Concerntration
Factor
3.0
2.5
2.0
1.5
1.00 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 PET
30% GR PET
30% GR PBT
30% GR Nylon 6.6 (DAM)
30% GR Nylon 6.6 (Cond.)
Nylon 6.6 (DAM)
POM Med. Viscosity
POM High Viscosity
Nylon 6.6 (Cond.)
210.000
70.000
19.500
11.000
10.000
10.000
7.500
3.300
3.200
3.100
1.600
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.
228
Moment ofInertia forA, B and C
2520 mm3
Compared to Amaterialsavings
up to 22.9 %
Compared to A
materialsavings
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
tH, 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 foruniform wall thickness.Design wall thickness as thin as possible and only as thick as
necessary.
Use ribbing instead of greater wall thickness.
Provide radiusing.
Provide demoulding tapers.
Avoid undercuts.
Do not design to greater precision than required.
Design multi-functional components.
Use economic assembly techniques.
Gate moulding on the thickest wall.
Ten rules for designers
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A Polymer for Every
Application