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

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

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

Types Permanent Assemblies Pre-molded Insert Rivets Key Headed Screws

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

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

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

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

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

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

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

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

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

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