As latest products persist to be designed and developed to sustain todays hi-tech advancements, the need for cornpact, a reliable fastening system is becoming more critical and challenging.
Requirements such as sheet metal too thin to tap, minimal space, secure grounding, sealing; anti-vibration characteristics and serviceability call for a clever approach to modern assembly. Self-clinching fasteners answer these needs by providing strong, reusable threads in thin sheet metal. Similar self- raising fasteners are also available for PC boards. Both types install into a round hole, which may be punched or drilled.
Simple and Efficient Design
The fasteners are offered in the form of internal threaded nuts or standoffs and externally threaded studs, in a wide variety of sizes and materials. Self-clinching fasteners are designed to be pressed into sheet metal with a steady squeezing force, resulting in the cold-flow of sheet material into the clinch profile of the fastener. When fully seated, the fastener is permanently attached to the structure and provides superior push-out and torque out performance. Installation may be performed with a standard hydraulic shop press. Special presses are available for automatic feeding and high-speed installation of self-clinching fasteners.
Once installed, the fasteners take up very little space, while providing strong threads for initial assembly and future servicing. Cost of installation and maintenance is greatly reduced as compared to separate nuts and screws. Also, product integrity is improved, since loose hardware cannot fall into the enclosure, causing unforeseen problems during servicing. A floating nut version also provides compensation for misalignment of mating panels.
To guard against loosening from vibration, locking features are available such as crimped threads or nylon inserts for nuts and nylon patches on studs. Special coatings are also available to protect threads from the adhesion of weld spatter and various electro-paint processes, eliminating the need for labour intensive capping or plugging.
In addition to installation and servicing advantages, self-clinching fasteners also provide a higher level of performance. Nuts, studs and standoffs offer a high resistance to pull-through, push-out and torque-out, by virtue of their clinch profile design. These values greatly exceed the operating forces exerted in normal use. To address various application requirements, the fasteners are available in a choice of materials such as hardened steel, stainless steel, hardened stainless, aluminum, brass and phosphor bronze with complimentary finishes of Zinc, cadmium, black oxide, nickel, copper flash or tin.
Fastener selection is dependent on the characteristics of the material into which it is to be installed, such as
·Composition (carbon steel, stainless, aluminum, fibreglass.etc.)
And to the elements to which it may be exposed, such as:
·Electrostatic discharge paint
And to the application in which it is used, such as:
·Stacked PC boards
Key points to consider when selecting the proper self-clinching fastener are:
I. The panel must be a ductile material, which is softer than the hardness of the fasteners that are to be installed. This allows the parent material to "cold flow" into the clinch profile, securely locking it into place.
2. Do not deburr mounting holes, since the sharp edge of metal around the hole aids in securing the fastener in the sheet metal panel.
3. Place fastener squarely into the punched side of the sheet to assure proper orientation and hole diameter.
4. Press fastener into place with a steady squeezing force to fully embed the fastener into the sheet material.
(Note: When installed properly, the resultant torque-out value of a self-clinching fastener will normally exceed the torsional strength of the mating fastener screw threads).
Broaching fasteners are specifically designed to install into rigid materials such as fiberglass and epoxy substrates used for PC boards. The fasteners are pressed into a round hole and held in place by an meddling fit. Popular versions of breaking fasteners are clashes used to load PC boards as well as a variety of nuts and studs for electrical attachment and assembly. Both self-clinching and raising fasteners provide distinct advantages over the installation of conventional nuts and machine screws. Loose hardware requires labour intensive and time-consuming assembly operations, and always poses a threat to falling into sensitive areas during assembly or servicing.
Permanent attachments, such as welding, riveting and adhesives, although reliable, prevent disassembly. Welding also introduces additional undesirable conditions, including tedious orientation, heat. fumes and resultant weld splash. A wide variety of self-clinching or broaching nuts, standoffs or studs are generally readily available in a choice of materials and finishes, to satisfy most electro-mechanical applications. When used, the end result is usually an overall cost savings and added product value. Typical market applications include consumer electronics, telecommunications, computers, appliances, trading equipment, lawn and garden power equipment, HVAC, instrumentation, plant machinery, automotive accessories, lighting fixtures and other miscellaneous fabricated sheet metal products. Uses vary widely, and are only limited to the mechanical designers imagination.
|Posted : 8/12/2005|