1. Using Mechanical Fasteners to Assemble Plastic Parts
Dane Taylor
Ray McKee
Jason Saggese

2. Purpose Explain Mechanical Fasteners in Plastics
Designing for Various of Fasteners
Effects of Using Fasteners

3. Outline Types of Fasteners Inserts Effects of Fastener Uses
Design Considerations
Material Property Effect

4. Types
Permanent Assemblies
Pre-molded Insert
Rivets
Key Headed Screws

5. Types Non-Permanent Assemblies Thread Cutting Screws
Thermosetting
High Modulus Materials
Thread Forming Screws
Semi-Crystalline
<200,000 psi Modulus

6. Types Non-Permanent Assemblies Molded-in Threaded Inserts
Positioning
Nuts and Bolts

7. Types Specially Designed Thread Pitch and Angle Trilobe Push-in
1,000,00 Modulus
Push-in
Double Lead

8. Inserts Molded-in Threaded Expansion Helically Coiled
Cap Nuts
Helically Coiled
Ultrasonic Insertion

9. Effects of Fastener Uses
Machine Screws vs. Plastic Designed Screws
Automated Assembly Lines
Molding Technique

10. Effects of Fastener Uses
Problems
Thread Stripping from Disassembly/Assembly
Poor Design
Extended Cycle Time

11. Design Considerations
Bosses
Inner Diameter
Pitch Diameter of Screw
Outer Diameter
2.5 X ID

12. Design Considerations
Bosses
Length
Thread forming
Minimum – 2.5 X Pitch Diameter
Thread Cutting
At least – 3 X Diameter

13. Design Considerations
Assembly
Deflection
Surface Area of Screw Head
Washers
Tapping
Ductile Materials
Cold Flow
Heat During Drilling

14. Material Property Effects
Stiffness
Acceptance Without Cracking
Crystallinity
Deforms around Screws
Annealing
Reduces Creep
Greater Life Expectancy