Explore our core pre-assembled mechanical fastening units designed to resist transverse harmonic resonance, eliminate washer assembly bottlenecks, and safeguard electronic and mechanical integrity.
In high-vibration operational environments—spanning electric vehicle battery packs, high-speed rail bogies, industrial robotic arms, and aerospace electronics—fastener failure is overwhelmingly caused by transverse dynamic displacement rather than axial over-stretching.
According to pioneering research by Gerhard Junker (DIN 65151), when a clamped joint is subjected to transverse cyclic motion perpendicular to the screw axis, the relative movement between the contact threads causes instantaneous neutralization of friction. In this state, friction drops to zero in the circumferential direction, and the internal thread ramp angle forces the bolt to back out.
Standard flat washers and spring split lock washers provide negligible dynamic locking under severe transverse shear because their elastic recovery distance is insufficient to match the micro-plastic settling of contact asperities. Furthermore, split lock washers often splay open under elevated tightening torques, accelerating joint degradation.
In automated OEM environments, assembly speed and quality variance dictate operating margins. While conventional multi-piece fasteners require multiple feeder bowls, indexing arms, and manual inspection gates, SEMS fasteners streamline supply chain logistics:
1. Inventory Streamlining: Combines distinct SKUs (screws, flat washers, spring washers) into 1 single unified part number, reducing purchasing overhead by 66%.
2. Tightened K-Factor Distribution: Pre-assembled captive washers feature controlled lubricating coatings and known bearing surface geometries, yielding a narrow friction coefficient window (±0.02) for consistent torque-tension translation.
3. Cleanroom Compliance: Captive assemblies prevent the scraping metal debris often created when loose split washers bite unpredictably into structural casings during high-speed torquing.
Selecting the optimal washer geometry within a SEMS unit is critical to neutralizing the dominant stress mode—whether axial thermal expansion, rotational torque shear, or localized dynamic bending.
Conical disc springs provide high spring forces in compact axial spaces. Designed specifically for bolted joints subject to embedding, relaxation, and thermal cycling. Upon clamp-down, the conical washer deforms elastically, continuously storing potential energy that compensates for micro-yield in clamped components.
Features multiple hardened helical teeth twisted along their axis. When compressed, the sharp serrations bite mechanically into both the fastener head and the workpiece substrate. This micro-mechanical interlocking creates an instantaneous breakaway torque barrier that arrests rotational unthreading.
Delivers moderate, uniform spring rates across 3 or 4 continuous wave peaks. Ideal for fragile bearing surfaces, electronic printed circuit boards (PCBs), lightweight aluminum housings, and polymer enclosures where high concentrated point loads would crack the mating component.
Combines a hardened flat washer (DIN 125/433) adjacent to the bearing substrate with a split helical spring washer (DIN 127B) beneath the screw head. The flat washer spreads the clamp load evenly, while the spring lock washer preserves initial preload tension against high transverse shear.
| Washer Configuration | Locking Principle | DIN / ISO Standard | Junker Test Performance | Ideal Application Scenario |
|---|---|---|---|---|
| Conical Belleville Spring | Elastic deformation & high reserve strain energy | DIN 6796 / ISO 10670 | Excellent (>80% preload retention) | Heavy powertrain, EV battery pack busbars, structural flanges |
| Serrated External Tooth | Mechanical bite / frictional tooth edge gouge | DIN 6798-A / ISO 10511 | Good under medium transverse vibration | Electrical grounding terminals, sheet metal enclosures |
| Wave Curved Spring | Continuous multi-point axial deflection | DIN 137-B / DIN 137-A | Moderate (prevents rattle & play) | PCB assemblies, optic instruments, consumer electronics |
| Helical Split + Plain Flat | Spring deflection paired with bearing load distribution | DIN 127B + DIN 125A | Moderate (standard industrial benchmark) | General machinery frames, HVAC compressors, industrial pumps |
| Dual Wedge-Locking Washers | Cam wedge geometry (rise angle > thread lead angle) | DIN 25201 | Superior (>95% preload retention) | Mining equipment, railway track fasteners, wind turbine nacelles |
From micro-electronics subjected to ultrasonic transit resonance to 800V automotive drivetrains, our custom anti-vibration SEMS fasteners are tailored to specific mechanical, chemical, and electrical profiles.
Battery enclosures, inverter busbars, and motor mounts undergo continuous road-induced harmonic vibration alongside extreme thermal cycling (-40°C to +125°C). Our stainless steel 304/316 and Class 8.8/10.9 alloy steel SEMS screws feature high-resilience Belleville washers coupled with blue nylon prevailing-torque patches, preventing relaxation in composite and aluminum pack enclosures.
Micro-fasteners (M1.2 to M3.0) for smartphones, drone flight controllers, and server racks cannot tolerate washer loss or stripped drive recesses. Our Torx and Phillips pan-head SEMS fasteners utilize custom Delrin plastic washers and captive copper spacers to provide mechanical cushioning and electrical grounding without PCB substrate fracture.
Solar combiner boxes and wind turbine nacelle sensors are exposed to cyclic wind buffet and moisture ingress. Our sealing SEMS screws combine vulcanized EPDM or fluorosilicone O-rings captive underneath stainless steel heads, achieving simultaneous IP67/IP68 ingress protection and anti-loosening torque endurance over 25-year service lives.
Articulated robotic wrists and pick-and-place end-effectors experience continuous bidirectional centrifugal acceleration. Traditional fasteners back out due to multi-axis inertia. SEMS fasteners integrated with serrated contact teeth and anaerobic micro-encapsulated coatings provide failsafe secondary security during emergency stops.
Across our 20,000 m² primary facility in Dongguan and specialized hubs in Shaoguan and Wuhan, YH Fastener operates integrated multi-station cold-formers, automated washer collation rings, and multi-laser optical sorting lines.
Strict incoming wire rod inspection (Spectrochemical chemical assay, eddy current testing for surface seam cracks). Sourcing strictly verified annealed grades: AISI 304, AISI 316, 10B21, SCM435, and titanium alloys.
High-speed multi-station headers cold-form heads (Phillips, Torx, Hex Socket, Tri-Wing) without thermal stresses. Fiber grain lines follow the fastener contours uninterrupted, maximizing head-to-shank shear fatigue life.
Proprietary rotary dial feeder rings orient and position washers onto pre-thread blanks at rates up to 350 pcs/min. Blanks pass optical sensors to verify washer presence and orientation before thread rolling.
Precision flat-die or cylindrical-die thread rolling expands the blank diameter to the major thread crests, mechanically locking the washer behind the shank while forming work-hardened, smooth root radii for elevated fatigue strength.
Controlled-atmosphere continuous mesh-belt furnaces achieve precise core and case hardness without hydrogen embrittlement. Surface finishes include Eco-friendly Geomet, Zinc-Nickel (1500h salt spray), Black Oxide, and Dacromet.
Multi-camera 360-degree glass plate optical inspection systems check thread pitch, concentricity, washer presence, head crack absence, and plating thickness to guarantee aerospace-level PPM consistency.
Addressing core mechanical, standardization, testing, and operational queries encountered by automotive design engineers and global procurement managers.
A SEMS fastener is manufactured with the washer permanently captured on the blank prior to thread rolling. Because the thread's major crest diameter is larger than the washer's internal hole diameter, the washer can never fall off or be forgotten during assembly. This guarantees correct joint specification, eliminates manual assembly steps, and ensures automated robotic feeders run without jamming.
Standard fasteners lose 100% of their preload within 300 to 500 transverse vibration cycles. High-grade anti-vibration SEMS fasteners—specifically those utilizing conical Belleville washers (DIN 6796) or paired wedge lock washers—retain over 80% to 90% of their initial clamping force after 2,000 cycles, because the spring deflection absorbs shear displacement without allowing the thread faces to slip.
Yes. YH Fastener routinely manufactures custom SEMS units combining metal shanks with high-performance polymers (Nylon 66, Delrin, PEEK, PTFE), brass conductive washers, and vulcanized EPDM/FKM elastomeric sealing gaskets. These designs are widely utilized in electronic isolation, anti-galvanic corrosion assemblies, and IP67 waterproof junction boxes.
SEMS fasteners introduce a known, repeatable friction interface between the fastener under-head and the washer top. Because this interface is factory-controlled and typically treated with uniform dry lubricated platings (Zinc-Nickel, Waxed Passivations), the total torque scatter (ΔK) is reduced by up to 40% compared to loose, unwashed, field-lubricated components, providing tighter clamp load repeatability.
Our plants operate under ISO 9001, ISO 14001, and IATF 16949 quality management frameworks. Every export batch is accompanied by EN 10204 3.1 Material Test Reports (MTR), heat treatment hardness charts, salt spray test certificates, dimensional inspection logs, and full PPAP Level 3 documentation packages upon client request.
Yes. Dual-locking solutions are common in critical aerospace and EV applications. We apply pre-coated engineering nylon (e.g., Nylok Blue, 3M Scotch-Grip) or micro-encapsulated anaerobic adhesives directly onto the screw threads, while capturing a Belleville or wave washer under the head. This combines mechanical spring compensation with prevailing-torque thread locking.
Complete product portfolio comprising precision thread-forming, captive shoulder spacers, nylon-patch locking screws, and extreme-duty high-speed assembly fasteners.
