Plastics Mould and Product Design Tech.


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Plastics Mould and Product Design Tech.

Chapter 1

PART DESIGN PROCESS: CONCEPT TO FINISHED PART

7 Design Process

8 Defining Plastic Part Requirements

8 Mechanical Loading

8 Temperature

8 Chemical Exposure

8 Electrical Performance

8 Weather Resistance

8 Radiation

8 Appearance

9 Agency Approvals

9 Life Expectancy

9 Dimensional Tolerances

9 Processing

9 Production Quantities

9 Cost Constraints

9 Assembly

10 Thermoplastic Processing Methods

10 Injection Molding

11 Extrusion

12 Thermoforming

12 Blow Molding

13 Rotomolding

14 Optimizing Product Function

14 Consolidation

14 Hardware

14 Finish

15 Markings and Logos

15 Miscellaneous

15 Reducing Manufacturing Costs

15 Materials

16 Overhead

16 Labor

16 Scrap and Rework

16 Prototype Testing

Chapter 2

GENERAL DESIGN

17 Wall Thickness

20 Flow Leaders and Restrictors

22 Ribs

22 Rib Design

22 Rib Thickness

23 Rib Size

24 Rib Location and Numbers

25 Bosses

28 Gussets

28 Sharp Corners

30 Draft

31 Holes and Cores

32 Undercuts

32 Slides and Cores

34 Louvers and Vents

35 Molded-In Threads

38 Lettering

39 Tolerances

41 Bearings and Gears

Chapter 3

STRUCTURAL DESIGN

43 Structural Considerations In Plastics

44 Stiffness

44 Viscoelasticity

46 Stress-Strain Behavior

47 Molding Factors

48 Short-Term Mechanical Properties

49 Tensile Properties

49 Tensile Modulus

49 Tensile Stress at Yield

49 Tensile Stress at Break

49 Ultimate Strength

49 Poisson’s Ratio

50 Compressive Properties

50 Flexural Modulus

50 Coefficient of Friction

51 Long-Term Mechanical Properties

51 Creep Properties

53 Stress Relaxation

54 Fatigue Properties

55 Structural Design Formulas

55 Use of Moduli

56 Stress and Strain Limits

57 Uniaxial Tensile and Compressive Stress

58 Bending and Flexural Stress

62 Shear Stress

63 Torsion

64 Designing for Stiffness

64 Part Shape

67 Wall Thickness

68 Ribs

70 Long-Term Loading

73 Designing for Impact

75 Fatigue Applications

77 Thermal Loading

Chapter 4

DESIGN FOR ASSEMBLY

79 Part Consolidation

80 Mechanical Fasteners

82 Snap-Fit Joints

85 Welding and Bonding

86 Ultrasonic Welding

86 Vibration and Hot-Plate Welding

87 Spin Welding

87 Solvent and Adhesive Bonding

88 Retention Features

88 Alignment Features

90 Orientation

90 Expansion Differences

91 Tolerances

Chapter 5

MACHINING AND FINISHING

93 Drilling and Reaming

95 Tapping

95 Sawing

96 Punching, Blanking, and Die Cutting

97 Milling

98 Turning and Boring

99 Laser Machining

99 Filing

100 Sanding

100 Polishing and Buffing

101 Trimming, Finishing, and Flash Removal

Chapter 6

PAINTING, PLATING, AND DECORATING

103 Painting

103 Types of Paints

104 Paint Curing

104 Paint-Selection Considerations

105 Spray Painting

106 Other Painting Methods

106 Masking

107 Other Design Considerations for Painting

107 In-Mold Decorating

108 Film-Insert Molding

109 Metallic Coatings

109 Electroplating

110 Design Considerations for Electroplating

111 Molding Considerations for Electroplating

112 Vacuum Metallization

112 Design Considerations for Vacuum Metallization

113 EMI/RFI Shielding

113 Design Considerations for EMI/RFI Shielding

114 Printing

116 Labels and Decals

116 Texture

Chapter 7

MOLD DESIGN

119 Mold Basics

119 Types of Molds

122 Mold Bases and Cavities

123 Molding Undercuts

126 Part Ejection

128 Mold Venting

128 Parting-Line Vents

129 Vent Placement

131 Sprues, Runners, and Gates

131 Sprues

133 Runners

135 Runners for Multi-cavity Molds

138 Gates

142 Other Gate Designs

144 Gate Optimization

145 Gate Position

146 Hot-Runner Systems

146 Hot-Runner Designs

147 Hot-Runner Gates

148 Valve Gates

149 Thermal Expansion and Isolation

150 Flow Channel Size

151 Mold Cooling

151 Mold-Cooling Considerations

153 Cooling-Channel Placement

156 Cooling-Line Configuration

157 Coolant Flow Rate

158 Mold Shrinkage

160 Mold Metals

161 Surface Treatments

162 Mold Cost and Quality

APPENDICES

163 Index

 

166 Part Design Checklist