Dirk Noordegraaf - Sabic
-
Upload
themadagen -
Category
Spiritual
-
view
1.015 -
download
0
Transcript of Dirk Noordegraaf - Sabic
Themadag Mikrocentrum Verbinden van Kunststoffen24 April 2012
Dirk Noordegraaf
Mechanical Assembly of Plastic Components
No. 1
Assembly Methods
ScrewsBolt and nutsNailsSnapfitsInsertsRivetsHeat/sonic inserts
hot plateultrasonicvibrationlaserelectromagnetic
Cyanoacrylates 2K, UV Acrylates hot melt1K, 2K epoxy1K, 2K Polyurethane1K, 2K Silicone
Mechanical Adhesives Welding
No. 2
Time
Deformation = Constant
Mechanical Fixing = Managing Stress and Stress relaxation
Inserts, Screws, Snapfits all introduce local permanent stress and/or elongation
No. 3
Relaxation modulusRelaxation modulus
Rela
xati
on
s m
od
ulu
s E r
Time
= 5%
No. 4
Time t (log)
εεεε
1
2
3
4
Maximum allowable elongation
No. 5
Short term longtermProduct Polymer unreinforced reinforced unreinforced reinforced
Lexan* resin PC 4 1 - 4 1) 0,8 0,4 - 0,5Noryl* resin PPO/PS 3 - 4 2) 1 - 2 1) 0,6 - 0,7 0,4Cycolac* resin ABS 2 1 - 2 1) 0,5 0,4Cycoloy* resin PC/ABS 3 0,6Ultem* resin PEI 5 0,5 - 3 1) 1 0,5Valox* resin PBT + PET 3 1 - 3 1) 2 1Xenoy* resin PC/PBT 4 1 - 3 1) 2 1Noryl GTX* resin PPE/PA 3 2 - 3 1) 2 1
Maximum allowable elongation
1) Depending nature and loading of the filler.
2) Depending ratio PPE/PS
No. 6
Stress [ h ]
σ 1
σ 2
σ 3
σ 1> σ 2> σ 3
Elon
gatio
n [ %
]
Maximum allowable stress
No. 7
Material 23 °C 50 °C 70 °C 100 °C 120 °C 175 °C
Cycolac * resin
Cycoloy * resin
Noryl * resin
Reinforced 1)
Lexan* resin
Valox* resin
Ultem* resin
12
13
8-1428
1435
1021
2643
2
5-1024
1128
-
3-721
721
3,513
-
0-312
3,514
1330
-
-
-5
-7
8
-
-
--
--
720
Maximum allowable stress
unreinforced
Reinforced 1)unreinforced
Reinforced 1)
Unreinforced 2)
Reinforced 1)unreinforced
1) Depending nature and loading of the filler.
2) Depending ratio PPE/PS
No. 8
Managing stress
Surface area
Wall thickness
No peak stresses (circular bosses, trilobal screws)
Radii everywhere
Screws
Mechanical Assembly of Plastic Components
No. 10
Screw Joints
Molded in ThreadThreadforming ScrewsThreadcutting ScrewsMetal InsertsBolt and Nut
No. 11
Screw Assembly
advantages/disadvantages
Separable Extra production stepVibration proof Extra partSelf regulating Local stress concentration
No. 12
Basic rulesBeware of sinkmark when boss is located on the backside of A surface
keep wallthickness/rib ratio
No automatic X / Y positioning by the screw. Centric boss needed.
Screw Assembly
In molded threadScrew Assembly
No. 14
In molded threadNote• use maximal radii both for external as well as internal thread • do not use tapered thread
Screw Assembly
No. 15
Threaded pipe connection
Max. torque for ¾ thread Ultem* 2400 resin 135 NmNoryl* GFN1740V resin 100 NmNoryl* GTX830 resin 90 Nm
Tensile strengthUltem* 2400 resin 180 MPaNoryl* GFN1740V resin 165 MPaNoryl* GTX830 resin 110 MPa
Maximum Torque correlated with Tensile Strenght
InsertsScrew Assembly
No. 17
Fully reversible assembly External profile determine torque and pull out forceAvoid sharp edges
Heat insert US insert Expansion insert Threadcutting insert
Inserts
Screw Assembly
No. 18
Boss Design
Boss outer diameter at least twice insert outer diameterHole ø = insert outer ø - 0.5 mmInserts should stand slightly above the surface of the plastic so that the bolt rests on the top surface of the insert and not on the plastic part.
D
2*D
D+0.5 mm
R=0.25W
W
D ~ 0.5W for reduced sink mark
0.5-1.5°Draft angle
Reduce mass
2 mm for flash
0.05 –0.2 mmD
2*D
D+0.5 mm
R=0.25W
W
D ~ 0.5W for reduced sink mark
0.5-1.5°Draft angle
Reduce mass
2 mm for flash
0.05 –0.2 mm
ScrewsScrew Assembly
No. 20
Threadcutting Screws
Use only for rigid plastics to avoid high stresses
45°±5°
Thread forming
Generally used for plastics
Screw Assembly
No. 21
Diameter screw is determined by the maximum stress at stripping
Unreinforced resinsdhole = 0,8 x dscrew
Reinforced resins dhole = 0,88 x dscrew
Lead-in counterbore to reduce radial edge stresses
outer d1.7-2.5*d
Hole d
d
0.3-0.5d
ThreadEngagement
1.7-2.2*d
s
A
R
R
detail A
d+0.2mm
Wallthickness
Boss design
Screw Assembly
No. 22
30°
Frad
Fax F
Frad = 0.26FFax = 0.97F
Flank angle • 30° for low radial stresses
Thread pitch• max. 8° for vibration
resistance
Core diameter• small to enable material flow• enough space for displaced
material
Tolerances• only + tool to reduce
thread stripping
Screw Design
Screw Assembly
No. 23
Screw installation process
Positioning and fixation
Alignment
Installation• torque• speed
Screw Assembly
No. 24
Installation torque
Thread engagement
torque
threadforming
Thread friction
Clamp force
Stripping torque
Screw headin contact with boss
thread forming
head in contact without clamp load
(installation torque Ti)
destruction of the joint
(stripping torque Ts)
Screw Assembly
No. 25
Torque versus hole diameter
Torque versus hole diameter
0
0.5
1
1.5
2
3 3.2 3.4 3.6 3.8
diameter mm
torq
ue N
m
installation torquestrip torque
Material Lexan* resin 161Screw PT K40 Depth 6 mmSpeed 400 RPM
Largest difference between installation and strip torque is at 3.4 mm
No. 26
Torque versus installation speed
Cycolac* resin4.0 mm hole5.0 mm screw8.0 mm depth
heat generationweakens andmelts boss athigh speed
torque and flankstress decrease 0
1
2
3
0 500 1000 1500 2000 2500
driver speed (rpm)to
rque
(Nm
)
installation torque
stripping torque
optimal driver speed
SnapfitsScrew Assembly
No. 28
Strain in constant width and thickness beamStrain in constant width and thickness beam
3 * f * h2 * l2
=
h
f
l
x 100%max = 93,2 MPa (103,5) max = 3,7 % (4,5)F = 20,1 N (20,7)
Nonlinear FE analysis
l = 10 mmh = 2 mmf = 1,5 mmb = 3 mmE = 2.300 N/mm2 (manual
calculation)
max
Fbending =f*E*b*h3
4*l3
3 *E* f * h2 * l2
=max Length is a dominant factor in the snapfit
max
No. 29
Conical SnapfitsConical Snapfits
0,3 0,4 0,5 0,6 0,7 0,8 0,9 1,0
R = ho hs/
1,0
1,1
1,2
1,3
1,4
1,5
1,6
1,7
1,8
1,9
2,0
2,1
2,2
Ks
h0
hs
f
max=3 *f * hs
2 * l2 * Ks100 %
Ks = Geometry factor
max = 58,7 MPa max = 2,3 %F = 12,3 N
l = 10 mmh1 = 2 mmh2 = 1 (0.8) mmf = 1,5 mmb = 3 mmE = 2.300 N/mm2
max = 52,4 MPa max = 2,0 %F = 10,8 N
No. 30
Insertion and Pull-out Forces
h
f
l c
F
FF2 12 1
F : deflection forceF1 : insertion forceF2 : pull-out force1 : insertion angle: pull out anglef : deflection
http://www.sabic-ip.com/webtools/redirect?tool=snapfit
PressfitsScrew Assembly
No. 32
Press fits
Shaft/Hub Joint Bush/Housing Joint
No. 33
Key parameters for a press fitKey parameters for a press fit
Diametric Interference [ U ]Relative Diametric Interference [ U R ] Relaxationsmodulus [ E r (t) ]Coefficient of friction [µ 0 ]
http://www.sabic-ip.com/webtools/redirect?tool=bosscalc
No. 34
2
D2D1p
d = D1+ UF
D 1 = Hub inner diameter (nominal) D 2 = Hub outer diameterU = Interference (d - D1)p = Holding pressure [ MPa ]F = Assembly force
Key parameters for a press fitKey parameters for a press fit
Interference U is diameter difference between joining parts
The relative Interference is:Interference U
Nominal diameter D1x 100 %
No. 35
Maximum interferences for unreinforced Lexan* resin and Noryl* resinMaximum interferences for unreinforced Lexan* resin and Noryl* resin
Plastic shaft/Plastic hub
Metal shaft/Plastic hub
0,2 0,3 0,4 0,5 0,6 0,7
7
8
9
10
11
12
13
Max
imum
inte
rfer
ence
(μm
/mm
of t
he s
haft
Hub inner diameter / hub outerdiameter( D1 / D2)
Calculation exemple
No. 36
Calculation exampleCalculation example
D2D1p
d = D1+ U
L
D1 = 8 mmD2 = 12 mm (18 mm)
Maximum interference
D1 / D2 = 8 / 12 = 0,66= 8 / 18 = 0,44
Value 7,6 * 8 = 60,8 µ8,4 * 8 = 67,2 µ
The maximum allowable interference is
0,06 mm( 0.067 mm)
No. 37
Summary
• Mechanical fastening particularly advantageous is the assembly needs beunassembled during life time
• Managing long term lower level stresses in mechanical joint of keyimportance to prevent failure
• Performance, peak stresses and maximum allowable stresses for mostmechanical joints are very well predictable
No. 38
SABIC-IP Global Disclaimer
THE MATERIALS, PRODUCTS AND SERVICES OF SABIC INNOVATIVE PLASTICS HOLDING BV, ITS SUBSIDIARIES AND AFFILIATES (“SELLER”), ARE SOLD SUBJECT TO SELLER’S STANDARD CONDITIONS OF SALE, WHICH CAN BE FOUND AT http://www.sabic-ip.com AND ARE AVAILABLE UPON REQUEST. ALTHOUGH ANY INFORMATION OR RECOMMENDATION CONTAINED HEREIN IS GIVEN IN GOOD FAITH, SELLER MAKES NO WARRANTY OR GUARANTEE, EXPRESS OR IMPLIED, (i) THAT THE RESULTS DESCRIBED HEREIN WILL BE OBTAINED UNDER END-USE CONDITIONS, OR (ii) AS TO THE EFFECTIVENESS OR SAFETY OF ANY DESIGN INCORPORATING SELLER’S PRODUCTS, SERVICES OR RECOMMENDATIONS. EXCEPT AS PROVIDED IN SELLER’S STANDARD CONDITIONS OF SALE, SELLER SHALL NOT BE RESPONSIBLE FOR ANY LOSS RESULTING FROM ANY USE OF ITS PRODUCTS OR SERVICES DESCRIBED HEREIN. Each user is responsible for making its own determination as to the suitability of Seller’s products, services or recommendationsfor the user’s particular use through appropriate end-use testing and analysis. Nothing in any document or oral statement shall be deemed to alter or waive any provision of Seller’s Standard Conditions of Sale or this Disclaimer, unless it is specifically agreed to in a writing signed by Seller. No statement by Seller concerning a possible use of any product, service or design is intended, or should be construed, to grant any license under any patent or other intellectual property right of Seller or as a recommendation for the use of such product, service or design in a manner that infringes any patent or other intellectual property right.SABIC Innovative Plastics is a trademark of Sabic Holding Europe BV* Trademark of SABIC Innovative Plastics IP BV