Process Key Points of Injection Molds for Security Camera Housings

Security camera housings are precision plastic structural components that integrate aesthetic appearance, assembly accuracy, dust and waterproof protection, as well as outdoor weather resistance. Most products feature thin-walled curved surfaces equipped with lens recesses, waterproof grooves, dense screw posts, snap undercuts and other intricate structures. Such parts are prone to defects including warpage, weld lines, sink marks, ejection whitening, scratch damage and dimensional deviation during molding, which imposes stringent standards on mold design and injection molding process control.

1. Core Design Specifications of Injection Molds

For parting and draft design, the parting line follows the maximum outer contour of the product and stays completely off visible cosmetic surfaces to eliminate obvious parting lines. The draft angle for smooth exterior surfaces is no less than 1.5°, while matte textured surfaces require a 2° to 3° draft angle to prevent demolding scratches and whitening. Slanted lifters and side cores are installed for internal snaps and undercuts to avoid deformation and cracking from forced ejection. All waterproof grooves and sealing steps are finished with R0.3 rounded corners to reduce stress concentration and stabilize waterproof assembly performance.

For gating system layout, compact indoor camera housings adopt submarine pinpoint gates hidden on internal assembly areas to leave invisible trimming traces. Large outdoor shells use balanced hot runner systems to shorten melt flow paths and minimize severe weld lines and short shots. Fan-shaped side gates are applied for transparent lens covers to deliver steady melt flow and eliminate bubbles and flow marks. Trapezoidal runners and extended cold slug wells are used to trap cold material and prevent surface speckles, while multi-cavity molds adopt balanced runner layout to ensure uniform filling across all cavities.

Uniform cooling serves as the fundamental solution to shell warpage. For 1.2–2.0 mm thin walls, cooling channels are arranged 10–15 mm away from cavity surfaces with denser layout on thin sections. Surrounding baffles are added around heat-concentrated features such as screw posts and lens bosses for targeted cooling. Separate temperature control circuits are configured for core and cavity plates to avoid uneven color and thermal deformation. Cooling channels of Φ8–Φ12 mm with smooth arc corners deliver consistent heat dissipation, and cooling rings are fitted around hot runner nozzles to stop gate yellowing and carbon accumulation.

Adequate venting eliminates burn marks, gas lines and incomplete filling. Segmented vent slots with a depth of 0.015–0.02 mm are machined along the parting line, with insert vents added at ribs, weld line intersections and trapped-air dead zones. Flash wells are reserved at deep rib ends to fully exhaust entrapped air. The ejection system combines flat ejector pins, straight ejector pins and sleeve ejectors. Sleeve ejectors are mandatory for all screw posts to disperse ejection force and avoid sink marks and whitening. Large ejector pins and ejector blocks are prohibited on visible cosmetic surfaces to maintain flawless appearance.

In terms of mold steel selection, S136H pre-hardened stainless steel is used for cosmetic cavities for outstanding polishing, texturing and anti-rust performance. Mold bases adopt P20 or 50# steel, while sliders, lifters and cavity inserts are manufactured from 718H to sustain stable long-term mass production. All fitting surfaces are precision ground with dimensional tolerance controlled within ±0.03 mm to guarantee consistent assembly gaps.

2. Material Selection Standards

ABS resin is used for conventional indoor housings for favorable fluidity, smooth surface finish and cost efficiency. Outdoor camera shells exposed to sunlight, drastic temperature shifts and humidity require ASA or PC/ABS alloy, which deliver superior UV resistance, anti-aging property and crack resistance. All raw materials must be fully dried before molding: ABS is baked at 80–85 °C for 2–4 hours, and PC/ABS blends at 90–110 °C to remove moisture and suppress silver streaks, bubbles and post-molding cracking.

3. Injection Molding Parameter Control

For temperature regulation, barrel temperature is maintained between 200–230 °C and mold temperature at 55–65 °C. Slightly elevated mold temperature improves weld lines and flow marks on high-gloss precision parts. Excessively high temperature triggers polymer decomposition, yellowing and black specks, while insufficient temperature causes poor fluidity, short shots and sink marks. Nozzle temperature needs strict monitoring to avoid carbon buildup.

Multi-stage injection velocity is implemented for filling: low speed at gates to prevent melt scorching from direct impact, medium steady speed for main shell bodies, and moderately boosted speed for thin intricate sections to achieve full filling. Packing pressure operates in two phases: high initial pressure compensates material shrinkage to reduce sink marks, and low stabilizing pressure releases internal stress and restrains warpage. High-pressure high-speed direct injection is strictly forbidden to prevent flash and stress cracking.

Sufficient cooling time is set according to wall thickness to fully solidify the shell and reduce post-demolding deformation. The mold opens at a steady low speed, with extra deceleration buffer when passing undercuts and snaps to avoid edge chipping and surface scratches. Robotic automatic picking replaces manual handling; direct human contact with cosmetic surfaces is banned to avoid fingerprints and abrasions.

4. Defect Rectification & Production Quality Management

Warpage is corrected by optimizing cooling channel layout, balancing core/cavity temperature, lowering packing pressure and adjusting injection velocity segments. Obvious weld lines are improved by expanding vent capacity, raising mold temperature and tuning filling speed. Ejection whitening and scratches are resolved by enlarging draft angles, balancing ejection systems, polishing mold cavities and adjusting undercut fitting clearances. Sink marks are eliminated via optimized rib design, revised packing parameters, relocated gates and enhanced localized cooling.

First articles undergo full inspection of dimensions, appearance, waterproof grooves and assembly clearances. Routine visual inspection is conducted every two hours during mass production to check surface defects, gate residues, flash and deformation. Molding parameters including barrel, mold and oil temperature are locked without arbitrary adjustment. Cosmetic parts are produced in dust-free workshops to eliminate black specks from floating particles. Regular mold maintenance involves cleaning vents, parting lines and scaled cooling channels to preserve molding precision.

The core principle of housing molding lies in stabilized temperature, pressure, velocity and venting. Standardized mold design and precise parameter tuning effectively cut defect rates, delivering camera shells with uniform appearance, precise dimensions, solid structure and reliable waterproof performance for long-term field operation.