Written by Jeff Greenwood Product Sales Engineer
SPIROL International Corporation
Fasteners are some of the most important parts of an assembly as they hold all of the parts together and facilitate any interaction between the components. Ideally, the selected fasteners are simple to install, provide a quality product for the lifetime of the assembly, and yield the overall lowest cost given the entire manufacturing process.
Press-fit pins are one of the most common types of pins used in modern manufacturing. The fasteners are typically easy to install and let manufacturers avoid soldering, such as when assembling electronics.
There are two general categories of press-fit pins: solid and spring pins.
Solid pins either have a smooth, uninterrupted surface (such as dowels) or are designed with retention features (such as knurls, grooves, and barbs). All solid pins are retained by displacing the host material. Conversely, spring pins are self- retained by exerting a radial force (tension) against the hole wall after installation.
There are two different types of spring pins: slotted spring and coiled spring pins.
Slotted spring pins are general-purpose fasteners typically recommended for non- critical assemblies. Oftentimes, these pins are used in applications where they’re manually installed into mild or hardened steel components. They have a gap designed for the pin to flex during installation, which lets it absorb the varying hole tolerance.
Coiled spring pins are available in light, standard, and heavy-duty options, so a designer can choose the optimum combination of strength, flexibility, and diameter suited for varying host materials and performance requirements. These pins have two, 1/4-coils of material, allowing them to flex during and after installation. The flex supports varying hole tolerances, helps dampen shock and vibration, and prevents hole damage.
Although there are several ways to use pins, the most common are shown in the Typical pin functions table below. These guidelines apply the majority of the time, but each application should be evaluated for which pin type is most appropriate.
These are some of the many considerations when determining the proper pin for an application:
• What’s the pin’s function?
• What are the strength requirements of the pin?
• What is the material of the component in which the pin will be used?
• What environment will the pin be exposed to?
• What’s the intended product lifetime or the number of cycles?
• How will the pin be installed?
Spring pins are typically preferred over solid pins because of their flexibility, lower insertion forces, and ability to accommodate wider hole tolerances. However, there are exceptions.
Solid pins are the ideal choice when precise hole locations must be maintained, it’s necessary to manually align several clearance holes, a hollow pin is unsuitable, or increased bending or shear strength is required. Solid pins are also favored when a smooth, uninterrupted surface is preferred (such as when used in conjunction with an angular component) or the head is required for a positive stop or to retain a thinner part to a thicker section of an assembly.
Coiled spring pins are superior for assemblies that are subject to dynamic loading. This is because these pins offer a unique combination of strength and flexibility, which allows them to dampen forces and vibration, preventing hole damage and prolonging the assembly life. Each type of press-fit pin serves a purpose for manufacturers.
The Features and benefits table compares the common features, advantages, and benefits for each type of pin.
Designers can optimize the performance and total manufactured cost of an assembly by selecting the proper pin for an application. To do so, the fastener options must be considered early in the design stage of a project.
One of the most important steps in selecting the ideal pin is to fully evaluate and establish the performance requirements of the intended applications. The design team should also test and validate the fasteners in prototype assemblies before a final decision is made.
To learn more about selecting the proper pin for an application, please click here to read SPIROL’s full white paper.
"Jeff Greenwood, Mhandisi wa Mauzo ya Bidhaa ya SPIROL International Corporation, anasema: ""Vifungo ni sehemu muhimu zaidi za mkutano, kwani huunganisha sehemu zote pamoja na kuwezesha mwingiliano wowote kati ya vipengele.""" Kwa mfano, viunganishi vilivyochaguliwa ni rahisi kufunga, hutoa bidhaa ya ubora kwa maisha ya mkutano, na hutoa gharama ya chini kabisa kwa kuzingatia mchakato mzima wa utengenezaji. Press-fit pini ni moja ya aina ya kawaida ya pini kutumika katika utengenezaji wa kisasa. Fasteners ni kawaida rahisi kufunga na kuruhusu wazalishaji kuepuka soldering, kama vile wakati wa kukusanya umeme. Kuna makundi mawili ya jumla ya pini press-fit: pini imara na spring. Pini thabiti ama kuwa laini, uninterrupted uso (kama vile dowels) au ni iliyoundwa na vipengele vya uhifadhi (kama vile knurls, grooves, na barbs). Pini zote imara ni kuhifadhiwa kwa kuhamisha nyenzo mwenyeji. Kinyume chake, pini za spring hujihifadhi wenyewe kwa kutumia nguvu ya radial (mzunguko) dhidi ya ukuta wa shimo baada ya usakinishaji. Kuna aina mbili tofauti za pini za spring: spring slotted na pini za spring coiled. Slotted spring pini ni general-usahihi fasteners kawaida ilipendekezwa kwa ajili ya kusanyiko zisizo muhimu. Mara nyingi, pini hizi hutumiwa katika maombi ambapo wao ni manually imewekwa katika vipengele laini au hardened chuma. Wao kuwa na pengo iliyoundwa kwa ajili ya pini ya flex wakati wa ufungaji, ambayo inaruhusu kunyonya kutofautiana shimo uvumilivu. Coiled spring pini zinapatikana katika mwanga, kiwango, na chaguo nzito, hivyo mbuni anaweza kuchagua mchanganyiko bora ya nguvu, kubadilika, na kipenyo inafaa kwa ajili ya vifaa mbalimbali mwenyeji na mahitaji ya utendaji. Pini hizi zina coils mbili za 1 4 za nyenzo, na kuwaruhusu kugeuka wakati na baada ya ufungaji. flex inasaidia kutofautiana shimo uvumilivu, husaidia dampen mshtuko na vibration, na kuzuia shimo uharibifu. Ingawa kuna njia kadhaa za kutumia pini, kawaida ni kuonyeshwa katika kawaida pin kazi meza hapa chini. Miongozo hii inatumika zaidi ya wakati, lakini kila maombi inapaswa kutathmini kwa aina gani ya pini ni sahihi zaidi. Hizi ni baadhi ya kuzingatia wengi wakati wa kuamua pini sahihi kwa ajili ya maombi: • Nini kazi ya pini? • Ni nini mahitaji ya nguvu ya pini? • Ni nini nyenzo ya sehemu ambayo pini itatumiwa? • Pini hiyo itaathiriwa na mazingira gani? • Ni nini lengo la maisha ya bidhaa au idadi ya mizunguko? • Pini hiyo itawekwaje? Spring pini ni kawaida preferred juu ya pini imara kwa sababu ya kubadilika yao, chini ya kuingiza vikosi, na uwezo wa kukidhi tolerances pana shimo. Hata hivyo, kuna mambo fulani yasiyo ya kawaida. Pini imara ni chaguo bora wakati sahihi shimo maeneo lazima kudumishwa, ni muhimu kwa mkono align mashimo kadhaa clearance, pin tupu ni haifai, au kuongezeka bending au shear nguvu inahitajika. Pini imara pia hupendekezwa wakati uso laini, usio na usumbufu unapopendekezwa (kama vile wakati unatumiwa pamoja na sehemu ya pembe) au kichwa kinahitajika kwa kuacha chanya au kuhifadhi sehemu nyembamba kwa sehemu nene ya mkutano. Coiled spring pini ni bora kwa ajili ya makusanyiko ambayo ni chini ya mzigo nguvu. Hii ni kwa sababu pini hizi kutoa mchanganyiko wa kipekee wa nguvu na kubadilika, ambayo inaruhusu yao dampen nguvu na vibration, kuzuia uharibifu shimo na kupanua maisha ya mkutano. Kila aina ya pini ya kufungia inatumika kwa kusudi fulani kwa watengenezaji. Jedwali la Vipengele na Faida linalinganisha sifa za kawaida, faida, na faida kwa kila aina ya pini. Wabunifu wanaweza kuboresha utendaji na jumla ya gharama zinazozalishwa ya mkutano kwa kuchagua pini sahihi kwa ajili ya maombi. Ili kufanya hivyo, chaguzi za kifungo lazima zizingatiwe mapema katika hatua ya kubuni ya mradi. Moja ya hatua muhimu katika kuchagua pini bora ni kwa kikamilifu kutathmini na kuanzisha mahitaji ya utendaji wa maombi inayokusudiwa. Timu ya kubuni inapaswa pia mtihani na kuthibitisha fasteners katika makusanyiko ya mfano kabla ya uamuzi wa mwisho ni kufanywa. Ili kujifunza zaidi kuhusu kuchagua pini sahihi kwa ajili ya maombi, tafadhali bonyeza hapa kusoma SPIROL ya kamili nyeupe karatasi.