Application Of Knurled Insert Nut in Plastic Parts

Besides traditional mechanical fastening applications, another major use of knurled insert nuts is as inserts into plastic parts. In injection molding, heated knurled insert nuts are either embedded into the plastic part or directly injection molded. Due to the excellent thermal conductivity of brass, the heated insert quickly transfers heat to the plastic part, softening the area around the hole and facilitating insertion. This process, involving hot melting, hot pressing, ultrasonic welding, and injection molding pre-embedding, ensures a tight fit between the metal and plastic parts, providing reliable connection, locking, and fastening. It is widely used in the assembly of various types of knurled insert nuts.

To enhance the mechanical engagement with the plastic part, knurled round nuts used in injection molding are generally circular with various embossed patterns. For example, hot-melt molded round nuts are typically cylindrical, while hot-pressed or cold-pressed round nuts have a tapered or barbed shape. Knurled round nuts, with their knurled design, form a strong pull-out resistance with the plastic after it cools, crystallizes, and hardens. Carbon steel, due to its poor thermal conductivity, is prone to causing the plastic parts to loosen or crack at the contact surface due to thermal stress. Therefore, copper has become the preferred material for injection molding inserts.

Knurled cap nuts are widely used in modern electronic and communication devices. They are widely used in the plastic casings of laptops, desktop computers, GPS devices, routers, mobile phones, and wireless communication devices. Knurled cap nuts also play a crucial role in the assembly of plastic casings in home appliances, automobiles, medical devices, and electronics. These precision plastic casings require extremely high dimensional accuracy and bonding strength for internal fasteners, and knurled cap nuts not only provide stable internal threads but also effectively prevent loosening caused by repeated tightening.

In specific injection molding processes, the design of inserts must fully consider the shrinkage characteristics of the plastic material. For example, for knobs requiring manual adjustment or anti-slip properties, the design concept of knurled thumb nuts might be adopted, using fine straight or diamond knurling to enhance friction. During mold design, it's crucial to ensure the insert doesn't shift or leak material under high-pressure molten metal impact, and the nut should be flush with the top plane of the glue column, with a depth typically not exceeding 0.2mm, to ensure a smooth final product appearance and structural stability.

In the diverse applications of fasteners, the choice of different materials determines the final product performance. While steel nuts offer high mechanical strength, in high-temperature injection molding environments, steel nuts cannot conduct heat as quickly as knurled threaded nuts, easily leading to residual stress and even cracking within the plastic part. Therefore, in fields involving plastic hot melting and injection molding, knurled threaded nuts, with their superior thermal conductivity and corrosion resistance, perfectly replace traditional steel fasteners, becoming the standard configuration for internal threaded connections in plastic parts.

For applications requiring high torque or frequent disassembly, engineers utilize the knurled hex nut design. This design combines the wrench-like ease of use of a hex nut with the anti-slip properties of a knurled surface, providing exceptional torsional resistance within the plastic matrix. Simultaneously, the grooves on the knurled surface provide ample space for the molten plastic to fill, forming a barb-like mechanical locking structure upon cooling, significantly enhancing connection reliability