General Design Principles for DuPont Engineering Polymers - Module

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Figure 11.91 Heading tool Tool stroke Heading tool D d Support plate Heading tool Figure 11.92 Heading tool 0.7 t t 0.1 t 0.2 t 0.7 t 90° Pilot D>d 1.0 t Ø 1.4 t Ø 2.5 t Ø 1.5 t Ø t r 0.1 Figure 11.93 Riveting operations 1. Positioning of tool 2. Stroke Pre-load spring Pre-load sleeve Plastic fitting Pre-load spring Heading tool Pilot sleeve 1.5 t 3. Finishing head 122 Riveting Operations Permanent deformation is produced by pressure rather than by impact. The suggested tool and spring preload for various shaft diameters are given in the table below. t 2 mm 3 mm 4 mm 5 mm 6 mm 8 mm 10 mm Pre-Load Spring 20 kg 45 kg 80 kg 120 kg 200 kg 300 kg 500 kg Tool-Load (min.) 40 kg 90 kg 160 kg 240 kg 400 kg 600 kg 1000 kg Relaxation of Shaft and Head The tendency for a formed head to recover its original shape after deformation depends upon the recovery properties of material used and on environmental temperature. Caution • When riveting unmodified Zytel ® nylon it is advisable to have the part conditioned to equilibrium moisture content before riveting, in the dry state the material is too brittle. Impact modified materials such as Zytel ® ST and Zytel ® 408 nylon resins can be riveted in the dry-as-molded state. • When riveting onto sheet-metal it is necessary to remove all burrs from the edges of the hole in order to prevent shearing of the head. To ensure no recovery, as normally requested when joining sheet metal to plastic, riveting should be effected by ultrasonics. Practical Examples For examples of riveted parts, see Figure 11.94. Design for Disassembly To improve the recyclability of plastic parts, components should be designed in such a way, that disassembly is possible wherever possible. Aspects which should be considered for this are: • Use standard materials, whenever possible; • When multiple materials have to be used in one part, use assembly techniques which allow easy disassembly at a later stage; see also Table 11.01; • Disassembly, when applicable, should be possible by using robots; The design should allow easy cleaning and re-use of the part; • The part material should be recognizable by part coding, for example >PA66-35 GF< for polyamide 66 with 35% glass fiber reinforcement; • Inserts (other materials) should be easily removable, for example by using “breaking out” techniques.
Figure 11.94 Applications of riveting a. Pump impeller b. Impeller c. Speed-reducer housing Table 11.01 Comparison of Assembly Techniques for Plastic Parts Assembly technique Material combination Recyclability Disassembly Screw arbitrary good good, but time consuming Snap-fit arbitrary very good good, when properly designed Press-fit arbitrary good poor–reasonable Welding family members very good not possible (not always applicable) Bonding arbitrary poor poor Overmolding arbitrary reasonable poor 123
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dDuPont Engineering Polymers Genera
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8—Gears . . . . . . . . . . . . .
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1—General Introduction This secti
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Prototyping the Design In order to
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2—Injection Molding The Process a
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As a general rule, use the minimum
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Figure 3.11 Cored holes Figure 3.12
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Figure 3.19 Mold-ejection of rounde
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• Zytel ® nylon resin—Parts of
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4—Structural Design Short Term Lo
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Form of section Area A d d R R 1 1
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Table 4.03. Formulas for Stresses a
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Form of bar; manner of loading and
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Figure 4.01 Creep Stress (S), MPa (
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Figure 4.05 Creep in flexure of Zyt
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Example 1 It there are no restricti
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Determine the moment of inertia and
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Figure 4.11 Stress curves The compu
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Rim Design Rim design requirements
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Figure 5.08 Chair Seat Zytel ® 71
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Cantilever Springs Tests were condu
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7—Bearings Bearings and bushings
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debris is moved around continuously
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Table 7.01 Coefficient of Friction*
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Figure 7.15: Connecting rod spheric
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8—Gears Introduction Delrin ® ac
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9—Gear Design Allowable Tooth Ben
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Delrin ® 500. See the section on D
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Figure 9.06 Sizes of gear teeth of
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The following additional examples i
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In practice, the most commonly used
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Driving Gear Meshing Gear Table 9.0
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A full-throated worm gear is shown
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Worm Material Gear Material Possibl
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10—Assembly Techniques Introducti
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For these materials, the finer thre
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Table 10.01 Self-Threading Screw Pe
Page 75 and 76: Figures 10.07 and 10.08 show calcul
Page 77 and 78: Undercut Snap-Fits In order to obta
Page 79 and 80: Cantilever Lug Snap-Fits The second
Page 81 and 82: 11—Assembly Techniques, Category
Page 83 and 84: Figure 11.03 Drill spindle position
Page 85 and 86: Inertia Welding By far the simplest
Page 87 and 88: Machines for Inertia Welding The pr
Page 89 and 90: This is not always easy, because ap
Page 91 and 92: The holder a, will have equal and o
Page 93 and 94: Calculations for Inertia Welding To
Page 95 and 96: If, for example, the angles of the
Page 97 and 98: Welding Double Joints The simultane
Page 99 and 100: Figure 11.37 Commercial bench-type
Page 101 and 102: Heat is generated throughout the pa
Page 103 and 104: Figure 11.45 Tapered or stepped hor
Page 105 and 106: Weld strength is therefore determin
Page 107 and 108: ) General Part Design The influence
Page 109 and 110: eticule in the eye piece is suitabl
Page 111 and 112: For this reason, if the strength of
Page 113 and 114: Figure 11.64A shows a variation whi
Page 115 and 116: 3. Vibrations, generated either by
Page 117 and 118: If one part is only vibrated at twi
Page 119 and 120: Another joint design, with flash tr
Page 121 and 122: Figure 11.82. A linear welded motor
Page 123 and 124: B) Commercial linear and angular we
Page 125: Hot Plate Welding of Zytel ® One o
Page 129 and 130: Tolerances may be difficult to hold
Page 131 and 132: are used in either hand- or power-o
Page 133 and 134: ather than scrape, these drills wil
Page 135 and 136: The polishing operation is performe
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