| HS Code | 527077 |
| Material | Glass-filled nylon or PBT thermoplastic |
| Thread Type | UNF, UNC, or metric |
| Diameter | 1/2 inch to 2 inches (nominal) |
| Thread Pitch | 16 to 20 TPI or 1.0 to 2.5 mm |
| Head Style | Hex or slotted round |
| Drive Type | Hex socket, slotted, or Phillips |
| Color | Black, white, or custom molded colors |
| Temperature Resistance | -40°C to 120°C |
| Sealing Method | Integral O-ring or molded seal lip |
| Pressure Rating | Up to 150 psi (non-shock) |
As an accredited Injection Molded Screw-In Cover Plate factory, we enforce strict quality protocols—every batch undergoes rigorous testing to ensure consistent efficacy and safety standards.
| Packing | Each package contains 25 injection molded screw-in cover plates, securely packed in a corrugated box with protective inserts. |
| Container Loading (20′ FCL) | 20′ FCL: injection molded screw-in cover plates packed in cartons on pallets, securely stacked for maximum container utilization and safe transit. |
| Shipping | Injection molded screw-in cover plate, manufactured from durable plastic resin. Non-hazardous solid article, not regulated for transport. Packed in reinforced cartons and secured on pallets to prevent deformation. Ensure screw threads protected during transit. No special handling required; standard shipping procedures apply. |
| Storage | Store in a cool, dry, well-ventilated area away from direct sunlight, heat, and open flames. Keep original containers sealed when not in use. Avoid moisture and extreme temperatures to prevent warping or degradation. Do not store near strong oxidizers, acids, or incompatible chemicals. Ensure area is clean and free of mechanical damage. |
| Shelf Life | Shelf life is typically 5 years when stored in original packaging away from UV, heat, and moisture. |
In point-of-entry water treatment vessels, the injection molded screw-in cover plate functions as the upper access closure above granular activated carbon beds and pleated polypropylene cartridges. The plate is molded from a 30% by weight glass-fiber-reinforced polypropylene compound containing 0.3% heat stabilizer and 0.2% nucleating agent; melt flow rate is controlled at 12 g/10 min ± 2 g/10 min per ISO 1133-1:2022 to maintain uniform thread filling. The unscrewing core forms ISO 228-1:2000 G 2 parallel threads; the gate is placed on the dome center so that melt fronts converge on the unsealed outer flange rather than across the O-ring land. Pre-drying at 80°C for 4 h is required when ambient relative humidity exceeds 60%. Melt temperature is maintained between 230°C and 260°C, mold temperature is held at 40–60°C, and hold pressure is set at 60–80 MPa for a 120 mm nominal diameter part. Thread root radii are kept above 0.3 mm to limit stress concentration during unscrewing. No external mold release is permitted on the seal land or thread surfaces; residual slip agents create extraction peaks under NSF/ANSI 61. Extraction testing is performed under NSF/ANSI 61 and FDA 21 CFR 177.1520; hydrostatic qualification follows ASTM D1599 with sustained pressure cycling from 0 bar to 10 bar at 23°C. The finished assemblies appear in filter sumps, water softener brine cabinets, and prefilter housings.
Thread engagement length is set at 1.2× the nominal thread diameter in sodium hypochlorite service because glass-fiber-reinforced polypropylene closures exhibit longitudinal stress cracking at thread roots after repeated torque events. The preferred material is unfilled PVDF, with 15% maximum regrind allowed to preserve weld-line integrity; if PVC-U is specified, the processing window narrows to 180–200°C and requires a corrosion-protected barrel and screw because HCl evolution is possible during degradation. The PVDF melt temperature is held at 200–230°C, mold temperature at 50–90°C, and back pressure at 2–5 MPa to minimize screw slip and cavity gas formation. Seal selection is material-specific: EPDM is used for 10–12.5% NaOCl at ambient temperature, while FKM is substituted when metering pumps introduce trace hydrocarbon carriers. Chemical resistance is evaluated by ASTM D543 immersion and ISO 175; a 30-day continuous exposure to 10% NaOCl at 40°C is the acceptance criterion for environmental stress cracking resistance. Torque is limited to 15–20 N·m for PVDF covers to avoid creep at the seal land. The closures are installed on day tanks, metering-pump calibration pots, and agricultural sprayer mix tanks, where REACH and RoHS declarations accompany lot-level certificates of analysis.
| Service environment | Polymer system | Filler/reinforcement load | Critical standard | Operational boundary | Terminal product |
|---|---|---|---|---|---|
| Potable water | Glass-fiber polypropylene | 30% glass | NSF/ANSI 61; FDA 21 CFR 177.1520 | 10 bar at 23°C | POE filter sump |
| Sodium hypochlorite | Unfilled PVDF | 15% max regrind | ASTM D543; ISO 175 | 10–12.5% NaOCl at 40°C | Dosing tank lid |
| Hydraulic oil | Heat-stabilized glass-fiber PA66 | 30% glass | ISO 4406:2021 | 90°C continuous | Reservoir cleanout plate |
| Fuel | Heat-stabilized glass-fiber PA66 | 30% glass | ISO 175; SAE J1455 | 60°C cyclic | Fuel/water separator cover |
On mobile hydraulic power units, the injection molded screw-in cover plate closes the reservoir cleanout port and must remain dimensionally stable when oil temperature reaches 90°C. The specified compound is 30% glass-fiber-reinforced heat-stabilized PA66 with 0.5% copper-based heat stabilizer, pre-dried at 80°C for 4 h to 0.15% moisture. Threads are ISO 228-1:2000 G 1-1/2 with a flat elastomer gasket seated in a molded recess; seal compression is controlled by torque of 18–22 N·m rather than by thread interference. The material tensile strength is verified at 180 MPa dry and 95 MPa at 50% relative humidity per ISO 527-2. The closure is validated in a system-level cleanliness test according to ISO 4406:2021, with a required class of 17/15/12 after 10 min circulation. Mold design uses a collapsible core to avoid unscrewing torque damage to the gasket groove. The final assemblies are integrated into compact hydrostatic transmissions and excavator attachment power units.
Fuel- and oil-contaminated internal threads generate two failure modes: pitch diameter expansion from absorbed aromatic fractions and torque increase from swelling against the housing boss. The cover plate is molded from 30% glass-fiber-reinforced heat-stabilized PA66, conditioned to 2.5% moisture by ISO 1110 before assembly, and the housing threads are tapped with a clearance allowance that accepts 0.3% radial growth. Dimensional change after 1000 h immersion in the specified fuel is quantified using ISO 175; the measured radial growth is then used to set the pitch diameter tolerance. The molded part is designed with an additional 0.12 mm pitch-diameter allowance to absorb typical swelling without exceeding thread stripping limits. The injection molding process uses a melt temperature of 280–300°C, mold temperature of 80–90°C, and a valve-gated hot runner placed outside the thread runout to avoid weak weld lines. Torque retention is tested after 5000 on-off cycles at 60°C under SAE J1455 vibration profiles. The finished screw-in plates are used on diesel fuel/water separators, gasoline prefilter canisters, and auxiliary tank access ports.
Inside motive-power lead-acid battery systems, the screw-in cover plate is molded as a vent-cap carrier that seals the cell filling port while permitting gas recombination through a porous PTFE disk. The material is a 20% talc-filled, flame-retardant polypropylene with 28% halogen-free intumescent FR masterbatch; the compound passes UL 94 V-0 at 1.5 mm and resists 30% sulfuric acid for 168 h at 60°C per ASTM D543. Thread form is M27×3; the vent path is molded as a 5 mm channel with a 0.45 mm orifice leading to the flame arrestor. The part is injection molded at 210–240°C melt temperature and 30–50°C mold temperature; gas counterpressure is not used, but fill speed is reduced in the thread zone to prevent jetting that would interrupt FR additive dispersion. The finished plates are installed on forklift, pallet-jack, and telecom backup batteries, with design verification referenced to IEC 62485-2 and EN 50272-2 for ventilation and safety.
In disposable and reusable vacuum suction canisters, the screw-in lid plate incorporates a 20% barium sulfate-filled polypropylene body to provide radiopacity while maintaining compliance with USP Class VI extraction protocols and ISO 10993-5 cytotoxicity. The elastomeric gasket is overmolded from a platinum-cured silicone with compression set below 20% after 24 h at 121°C. The thread is a modified buttress profile with 2.5 mm pitch, allowing 1/4 turn engagement and reliable venting through a hydrophobic membrane sealed to the underside. Injection molding uses a cold-runner valve-gated system with melt temperature 210–240°C, mold temperature 30–40°C, and pre-drying at 80°C for 2 h when resin moisture exceeds 0.1%. The plate is validated for steam autoclave sterilization at 121°C for 30 min; repeated autoclave cycles are limited to 25 before the sealing surface shows creep. Terminal products include 1 L and 2 L suction canisters used in surgical fluid management.
Compressed-air coalescer housings use injection molded screw-in cover plates to retain replaceable glass-microfiber filter elements in a vertical bowl. The chosen resin is a 15% glass-fiber-reinforced polybutylene terephthalate with hydrolysis-stabilized additive package, rated for 120°C continuous dry heat and 80°C in water-contaminated air service. The thread is ISO 228-1:2000 G 1; the seal is an FKM O-ring with 70 Shore A durometer. The part is molded at 250–270°C melt and 70–90°C mold temperature to optimize crystallinity and minimize flange warpage. Air quality downstream of the assembly is verified per ISO 8573-1; oil carryover is measured per ISO 8573-2 or ISO 8573-5. Terminal applications are modular coalescing filter sets in food packaging and electronics enclosure cooling lines.
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The injection-molded screw-in cover plate described here is designated IMCP-SC-20-PC, a circular access closure produced from a flame-retardant polycarbonate resin system. The component is intended for threaded entry ports in non-metallic electrical enclosures, actuator housings, and weatherproof junction boxes where positive mechanical retention is required without a separate backing nut. The standard configuration carries an M20 x 1.5 male thread form conforming to ISO 261, with an integrally molded hex socket having a nominal width across flats of 8.0 mm and a head outer diameter of 26.0 mm ± 0.2 mm. Total installed height is 6.5 mm ± 0.15 mm excluding the optional EPDM sealing washer. The flame-retardant polycarbonate grade meets UL 94 V-0 at 1.5 mm when tested in accordance with IEC 60695-11-10; tensile yield strength is 62 MPa per ISO 527-2, and notched Charpy impact strength is 14 kJ/m² at 23 °C per ISO 179-1/1eA. The thread is dimensionally controlled to ISO 2768-mK, and the part is supplied with a residual moisture content not exceeding 0.02 wt% at dispatch. The compound is supplied with a REACH statement and complies with RoHS 2011/65/EU as amended by (EU) 2015/863. For outdoor enclosure closure, a UV-stabilized grade containing 0.3 wt% carbon black is available, and the sealing washer is specified at 50 ± 5 Shore A per ASTM D2240 with a compression set below 25 % after 24 h at 100 °C per ASTM D395 Method B.
Molding is performed on a 120-ton hydraulic injection molding machine with a 36 mm diameter general-purpose screw and a 20 L/D ratio. The thread feature reaches full replication only when the cavity is filled through a sub-gate located on the head flange rather than on the thread root; gating into the thread root produces jetting along the helix and a weld line at the opposite flank. The recommended melt temperature for the standard polycarbonate grade is 280 °C to 300 °C, with a mold temperature of 80 °C to 100 °C. Holding pressure is maintained at 80 MPa to 110 MPa until the gate freeze time of approximately 2.8 s, measured in a 2.0 mm-thick wall section. The mold core is cut with 0.5 % to 0.7 % shrinkage allowance on the thread major diameter in accordance with ISO 294-4. Batch-to-batch variation in thread peak force has been observed when regrind content exceeds 20 wt%; current production control limits regrind to 15 wt% or below. Pre-drying at 120 °C for 4 h is mandatory when the ambient relative humidity exceeds 60 % because polycarbonate hydrolysis above 290 °C causes surface splay and reduces thread tensile strength by an observable margin in installation torque tests.
Rheological data for the flame-retardant polycarbonate melt at 300 °C indicates a shear viscosity of approximately 250 Pa·s at a shear rate of 1000 s⁻¹ when measured by ISO 11443. The thread filling pressure drops by 12 MPa when the melt temperature is increased from 280 °C to 300 °C. This pressure difference is significant because the thread crest is only 0.7 mm wide at the mold parting line and can freeze before complete packing if the injection speed is below 40 mm/s. Dimensional conformity is verified on a coordinate measuring machine with a probing uncertainty of ±0.005 mm. Thread major and minor diameters are measured at 25 °C and normalized to 23 °C using the resin supplier’s coefficient of linear thermal expansion. The thread flank angle is inspected with an optical comparator at 20X magnification, and a GO/NO-GO ring gage conforming to ISO 1502 is used for full-form assessment. Capability studies on a 24-cavity tool show that the thread major diameter has a Cp of 1.33 when the mold temperature is held within ±3 °C.
Chemical compatibility boundaries are defined for this product. The all-polymer molded-in thread is not rated for continuous immersion in strong oxidizing acids, ketones, or aromatic hydrocarbons; specific chemical resistance data should be obtained from the resin supplier for concentrations above 5 %. Amine-based thread sealants are incompatible with the polycarbonate grade because they accelerate environmental stress cracking at the thread root under installation torque. Silicone-based sealants are acceptable, and the recommended thread engagement length is 5.0 mm to 8.0 mm.
Placement of the gate on the hex socket floor produces a radial flow front that converges on the opposite side of the thread, creating a weld line at approximately 180° from the gate. In unfilled polycarbonate this weld line retains approximately 80 % of the nominal tensile strength, but in a 20 % glass fiber-reinforced polycarbonate grade the retained strength can fall to 55 % of the unreinforced base resin value because fiber orientation is disrupted at the knit plane. When glass-filled material is specified for higher heat distortion resistance, the tool is configured with a dummy overflow well opposite the gate to displace the weld line into a non-load-bearing ring. The overflow well is separated by a tab gate with a land length of 0.8 mm and a depth of 0.4 mm, removed by an in-tool degating punch after part ejection. Melt residence time is held between 3 min and 6 min; longer residence at 300 °C darkens the flame-retardant package and shifts the UL 94 V-0 rating from 1.5 mm to marginal performance at 1.5 mm. For glass-filled grades the mold wear rate at the thread apex requires a hardened steel insert with surface hardness of 52 HRC to 56 HRC, and the tool should be inspected after 500,000 cycles for thread crest rounding beyond 0.05 mm.
For enclosures near hydraulic power units or engine bay compartments, a 25 % glass-fiber-reinforced nylon 6/6 grade is sometimes substituted for polycarbonate. Short-term heat distortion temperature is 240 °C at 1.82 MPa per ASTM D648 Method A, but the limiting parameter is the relative thermal index of the flame-retardant package under electrical and mechanical stress. Published RTI values for common 25 % glass-filled nylon 6/6 grades are typically 120 °C to 130 °C for mechanical impact and 130 °C to 140 °C for electrical retention. Oil absorption and condensation reduce the effective tensile strength by 10 % to 15 % after 1000 h at 85 °C when evaluated on ASTM D638 specimens. Moisture conditioning at 50 % RH can produce 0.08 mm to 0.12 mm of effective flank contact loss due to thread swelling. Consequently, the screw-in cover plate in nylon is not recommended for continuous service above 105 °C in dry electrical enclosures unless the mating port is also nylon 6/6 and the engagement length is increased to 8.0 mm. The glass-reinforced nylon version also requires a post-molding moisture conditioning step of 24 h at 23 °C and 50 % RH to stabilize thread dimensions before installation torque verification.
If the cover plate must be removed repeatedly during commissioning or maintenance, a knurled brass insert with an M20 x 1.5 internal thread can be placed into the mold before injection. The insert is preheated to 120 °C to prevent localized freezing of the polycarbonate melt at the metal interface, and the molding cycle is extended by 8 s to 12 s to allow the polymer to pack around the insert knurl. Pull-out strength is governed by the knurl depth and the hoop stress capacity of the surrounding plastic boss. Typical production values for a diamond knurl insert with an outer diameter of 24.0 mm and a boss wall thickness of 3.0 mm range from 600 N to 900 N when loaded in tension at 23 °C using an ISO 527-1 aligned fixture. The limiting failure mode is not thread shear but stress cracking in the polycarbonate at the insert base when installation torque exceeds 2.5 N·m. For the all-polymer molded-in thread version, the recommended installation torque is 1.8 N·m to 2.0 N·m. Threaded inserts should not be used with the glass-filled polycarbonate grade unless the insert is externally knurled with a rounded root, because sharp knurl ridges initiate immediate microcracks at the fiber ends. In production, insert placement is verified with a vision system that detects insert height misalignment greater than 0.1 mm before mold closing.
When compared with an integrally molded snap-fit cover plate of the same envelope size, the screw-in design imposes a minimum thread engagement length of 5.0 mm but allows the sealing washer to be compressed by a controlled torque rather than by a snap-arm deflection. Snap-fit covers rely on a cantilever snap arm with a target strain below 2.5 % in glass-filled grades, and the retention force can degrade if the snap arm is cycled beyond 50 engagement/disengagement operations. The screw-in cover plate has no snap arm and can tolerate repeated assembly up to the fatigue limit of the thread, which in the standard polycarbonate grade is approximately 200 cycles when torque is maintained below 2.0 N·m. Compared with a stamped sheet-metal cover plate, the injection-molded version permits an integrally molded sealing groove and color coding without secondary painting; the metal part requires a separate die-cut gasket and secondary deburring. However, the sheet-metal cover plate can withstand a higher assembly torque of 5.0 N·m and is preferred when field personnel use uncalibrated hand tools.
| Attribute | Injection Molded Screw-In Cover Plate IMCP-SC-20-PC | Snap-Fit Cover Plate SFC-20 | Machined Metal Cover Plate MC-20 |
|---|---|---|---|
| Retention mechanism | Molded-in male thread M20 x 1.5 per ISO 261 | Cantilever snap arm with undercut | Machined male thread M20 x 1.5 per ISO 261 |
| Installation torque | 1.8 N·m to 2.0 N·m | Not applicable; controlled by snap arm deflection | 3.0 N·m to 4.0 N·m |
| Gasket compression control | Torque-dependent, repeatable within ±0.1 mm | Snap arm geometry-dependent | Torque-dependent |
| Vibration resistance | Positive thread retention, no disengagement observed at 2 g, 5 Hz to 500 Hz sweep per IEC 60068-2-6 | Retention loss possible after snap arm fatigue above 50 cycles | Positive thread retention; requires thread locking compound above 10 g |
| Flame rating | UL 94 V-0 at 1.5 mm | UL 94 HB at 1.5 mm | Not applicable; metal does not propagate flame |
| Dielectric strength | 20 kV/mm per IEC 60243-1 | 18 kV/mm per IEC 60243-1 | Conductive; not rated |
| Mass | 4.2 g | 3.1 g | 11.8 g |
| Thread dimensional standard | ISO 2768-mK | Not applicable | ISO 965-1 tolerance class 6g |
The polymer-based part is not qualified for use in explosion-protected enclosures requiring Ex d flameproof joints unless the thread gap and flamepath dimensions are verified against IEC 60079-1; published data for this specific configuration is limited. The screw-in cover plate should not be combined with amine-based thread sealants if the polycarbonate grade is selected, because amines accelerate environmental stress cracking at the thread root under installation torque. For outdoor enclosures, a UV-stabilized polycarbonate grade containing 0.3 wt% carbon black is specified, and the EPDM washer is selected at 50 ± 5 Shore A per ASTM D2240 with a compression set below 25 % after 24 h at 100 °C per ASTM D395 Method B. Installation with a calibrated torque screwdriver is mandatory; pneumatic screwdrivers without torque control have been observed on assembly lines to exceed 3.0 N·m and crack the thread root in 4 % to 7 % of tested parts.
