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For cap molds with a spiral exterior (no split line allowed, and conventional forced ejection not feasible), a spring-gear angular sliding mechanism renables low-cost, small-center-distance demolding. The core idea is to replace traditional slide blocks with "elastic angle compensation + rotational thread release."
The core (which forms the spiral threads) is split into two parts: an outer fixed sleeve with the spiral cavity, and an inner movable core (engaged with the sleeve via helical teeth). A torsion spring (adjustable preload) is connected to the bottom of the movable core. When the mold opens, the ejector pins push the product as the moving half retreats. The product’s spiral threads force the movable core to rotate a small angle (typically 3°-5°) along the helical teeth, while the torsion spring contracts to store energy. This rotation "disengages" the spiral threads from the cavity, eliminating interference during forced ejection and enabling split-line-free spiral demolding.
The helical tooth angle of the movable core matches the product’s spiral lead angle (e.g., 4° for both). This ensures full thread disengagement during rotation. The ejector stroke is calibrated to the rotation angle (ejector stroke = spiral lead × rotation angle/360°) to prevent product deformation from over-ejection.
This replaces traditional split slide blocks (which require multiple slides, angle pins, and locking blocks) with a simple "movable core + torsion spring + helical teeth" setup. Mold part count is reduced by 60%, and machining costs drop by 40%-50% (eliminating slide-related processes like wire EDM and lapping).
Without side-action slide blocks (which require extra space for retraction), the mold width can be reduced by 30%-40%. Molds that previously needed large-tonnage injection machines (e.g., 180-ton) can now fit smaller machines (e.g., 120-ton), cutting equipment and floor space costs.
To match elastic rotation, the product’s spiral threads are designed with a depth ≤0.5mm and pitch ≥5mm. This reduces resistance during rotational disengagement while preserving the thread’s functional fit.
The spring's preload is adjusted to the product size: for small products (e.g., 20mm diameter), a 0.5N·m torsion spring ensures smooth rotation during demolding, while preventing excessive core rebound after product release.
This mechanism uses "spring-gear-driven core rotation" to enable split-line-free demolding of spiral-shaped parts. It eliminates the high cost and large footprint of slide blocks, allowing the mold to fit smaller injection machines while controlling costs. It is especially suitable for small-batch, multi-spec spiral products (e.g., small bottle caps, toy spiral components).
