Molded threaded fastener

With plastic materials, the designer also has a greater choice of bonding techniques than with many other materials. Thermosets must be adhesively bonded or mechanically joined, but most thermoplastics can also be joined by solvent or heat welding. Additionally, plastic parts can be designed for assembly by means of molded-in, snap-fit, press-fit, pop-on, and threaded fasteners so that no additional adhesives, solvents, or special equipment is required. 

Machine Screws, Bolts. Parts molded of thermoplastic resin are sometimes assembled with machine screws or with bolts, nuts, and washers (Fig. 7.6), especially if it is a very strong plastic. The threads used to engage the mechanical fastener may either be molded into the part (molded-in threads or molded-in inserts) or attached after the molding operation (post-molded inserts). 

Ultrasonic equipment can also be used for mechanical fastening operations. Ultrasonic energy can be used to apply threaded inserts to molded plastic parts and to heat stake plastic studs. 

The requirement for assembly of castings is limited since casting can make complex shapes. The most common methods are adhesives and fasteners. Self-tapping screws can be used with most of the materials used for casting. Threaded inserts can be molded in place, however they are difficult to salvage in the event of a reject moldment because the material is a thermoset and the inserts cannot be melted out. Threaded inserts can also be glued or tapped in place. 

Ultra-Mold, Mold-in insert threaded, Dodge, Emhart Fastening Teknologies... 

The high modulus and creep resistance of reinforced PPS compounds make them more suitable than many other plastic materials for fastening with bolts, screws, or rivets. For one-time bolted assemblies, tapped or molded-in threads with bolts screwed in three to four diameters may be used. However, with bolted assemblies where repeated assembly and disassembly of parts are expected, or if torque retention at elevated temperature is a concern, ultrasonic or molded-in metal inserts may be used. Molded-in metal inserts should be preheated to the mold temperature before being placed in the tool for molding. For assembly with self-tapping screws, BF-type or BT-type steel thread cutting screws work well, using hole sizes as recommended for phenolformaldehyde thermosets by the... 

Mechanical fastener connections are used when there is the need to disassemble the components. The most common reason for disassembly is for repair of the internal components of a device, which can be electronic, mechanical, or both. There are two main types of mechanical connections for assembling polymer components that will be considered. One type is the threaded inserts and bolts. The other common situation is when screws are threaded directly into the unthreaded polymer for mechanical fastening of another component. Threads can also be molded into the polymer component. Molding in threads increases the cost of the molding operation. 

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