Quick-Connect Nut Mold with 2-Stage Collapsible Core Mold Mechanism in the Fixed Mold Section

In the fluid control and pneumatics industry, the reliability of a quick connector relies heavily on the dimensional integrity of its internal sealing and fastening features. A prominent US-based quick connector brand commissioned us to develop a mold for a critical plastic nut.

The product's geometry presented a severe engineering contradiction:

• One end features a deep, 360-degree internal annular groove designed to house a high-pressure O-ring.
• The opposite end requires high-strength internal assembly threads.
• The Critical Constraint: The effective internal diameter of the nut is only 41mm.

In such a confined space, a conventional single-stage collapsible core or lifter system cannot secure enough lateral retraction stroke to clear the deep O-ring groove without interfering with the central axis.

To achieve sufficient radial collapse within the strict 41mm boundary, our engineering team designed a proprietary 2-Stage Sequential Collapsible Core integrated entirely within the fixed half of the mold.

Mechanical Architecture:

The mechanism consists of one central cross-shaped main shaft, four precision slanted guide tracks, and eight interlocking core segments that form the full inner circumference.

Dual-Delay Sequential Kinematics:

To execute the 2-stage collapse, the fixed half is divided into a sophisticated floating plate architecture consisting of the Top Clamping Plate, three floating plates (X1, X2, X3), and the Cavity Plate (A-Plate).

1. The X1 plate is locked to the Cavity Plate.
2. The central cross-shaft is anchored to the X2 plate.
3. The slanted guide tracks are mounted on the X3 plate.

The mechanical sequence is strictly governed by two robust delay mechanisms:

• Stage 1 (Initial Collapse): As the mold opens, the Cavity Plate, X1, and X2 move backward together as a single unit, separating from the X3 plate. The slanted guide tracks on X3 force the first group of segments to slide inward, completing the primary radial collapse.
• Stage 2 (Deep Collapse): Once the first delay stroke is reached, the X2 plate stops. The Cavity Plate and X1 continue to move. The central cross-shaft (fixed on X2) now engages the remaining segments, pulling them into a secondary, deeper inward collapse.

Parting Line Separation: Only after all 8 segments have fully retracted and cleared the deep O-ring groove does the main parting line (A/B plates) separate.

Once the fixed-half O-ring groove is cleared, the moving half must address the internal threads on the opposite end. To optimize the cycle time and prevent thread galling, we implemented an In-Situ Rotation Auto-Unscrewing System.

Instead of the traditional method where the threaded core rotates and retracts simultaneously, our design keeps the threaded core axially stationary:

• Driven by a hydraulic motor, the threaded core rotates in place (in-situ).
• The rotational force of the thread pushes the molded plastic nut forward.
• This axial thrust directly forces the B-Plate (core plate) to move forward synchronously, stripping the part off the core.

This integrated "rotate-and-push" ejection eliminates the need for separate axial stroke mechanics in the moving half, reducing the mechanical cycle time by up to 30%.

Engineered to US industrial standards for unattended operations, this 2-cavity mold incorporates highly efficient feeding and ejection systems:

Submarine to Pinpoint Gating: The mold utilizes a cold runner system that transitions from a submarine gate into a pinpoint gate directly on the part's face. Upon mold opening, the shear force automatically severs the gate, cleanly separating the waste runner from the product.

This project exemplifies the pinnacle of space-optimization in tooling design. By combining a 2-stage fixed-half collapsible core with a moving-half in-situ auto-unscrewing mechanism, Spark Mould successfully navigated the extreme 41mm spatial constraint.

This custom tooling solution provided our US client with a fully automated, flash-free, and high-yield manufacturing process, proving that even the most contradictory internal undercut geometries can be resolved with innovative mold kinematics.