16-Cavity PET Preform Mold with Dual-Stage Cam-Track Mechanism

• Product Type: PET Preform (External Neck Thread)
• Cavity Count: 16 Cavities (Arranged in 2 columns × 8 rows)
• Gating System: Fully Balanced Hot Runner System (16 Drops)
• Mold Structure: Double Parting Surface (Dual-Parting Line Split Configuration)
• Core Kinematics: Split-Cavity Slider System with Straight-to-Angular Cam Blocks

PET (Polyethylene Terephthalate) is highly sensitive to thermal gradients. Any variance in melt temperature or shear stress across the 16 cavities leads to inconsistent wall thickness, gate blushing, or unacceptable Acetaldehyde (AA) levels.

The Solution: The precision mold integrates a meticulously balanced 16-drop hot runner manifold. Each drop features localized, independent temperature zone monitoring to ensure identical rheological behavior of the melt, ensuring weight uniformity across all 16 preforms.

Rapid crystallization is the primary enemy of PET preform clarity. The thicker areas of the preform body must be chilled aggressively to remain amorphous (transparent) rather than crystalline (opaque).

The Solution: Traditional cooling channels are insufficient for tight 16-cavity clusters. This mold incorporates customized annular cooling inserts looping entirely around each individual cavity. By maximizing the cooling surface area and optimizing turbulent water flow, heat deflection is accelerated, reducing cycle times by up to 15%.

The definitive feature of this 16-cavity layout is its mechanical split-cavity (split-matrix) automation. Because the preform neck features critical external threads, the mold must open the cavity blocks laterally before the product can be safely dropped without damaging the thread profile.

Unlike larger 48-cavity configurations that frequently rely on external hydraulic or complex synchronized rack-and-pinion actions, this 16-cavity precision mold utilizes a robust, purely mechanical, high-reliability mechanical guide block assembly.

• The 16 cavities are divided into 2 distinct columns (8 cavities per column).
• Each column utilizes a split-cavity (Haf-block) design, split symmetrically into two identical halves.
• The top and bottom ends of each half-column are fitted with heavy-duty guide rollers (cam followers).
• These rollers are securely embedded within the precision-machined tracks of 4 robust guide blocks mounted symmetrically on the upper and lower sides of the moving half.

The precise timing of the cavity split is dictated entirely by the geometric profile machined into the guide blocks. Each block features a mirrored pair of tracks split into two essential phases:

When the mold opens and the ejection sequence begins, the B-plate is pushed forward. During the initial segment of this stroke, the guide rollers travel through a completely straight, linear track segment. This ensures that the neck thread inserts and the cavity halves move strictly parallel to the mold axis. The primary function here is to draw the molded thread cleanly off the stationary main core pin fixed to the backplate, preventing any lateral stripping or wiping of the warm PET thread.

Once the thread inserts have safely cleared the tip of the core pin, the rollers hit the transition zone of the cam track. Here, the tracks diverge into mirrored angles: the left-hand tracks slant outward to the left, and the right-hand tracks slant outward to the right. As the rollers force their way along these slants, the split-cavity halves are pulled laterally apart (left and right). This cleanly releases the thread profile, allowing the completed PET preforms to drop freely via gravity or a robotic take-out plate.

To ensure a mold life exceeding several million cycles, material selection is critical to resist the corrosive byproducts of PET processing and the mechanical friction of the cam rollers:

• Cavities & Cores: Premium stainless steel (e.g., DIN 1.2316 or FS136), through-hardened to HRC 48–52, providing exceptional corrosion resistance and a high-gloss finish to eliminate preform surface scuffing.
• Thread Inserts: Nitrided or hardened tool steel to withstand the repetitive abrasion of mechanical splitting.
• Cam Guide Blocks & Rollers: High-wear O1 or D2 tool steel, heat-treated to ensure the dual-stage tracks maintain micron-level tolerances over years of continuous operation.

This 16-cavity PET preform mold highlights how customized mechanical kinematics can simplify automated production. By swapping out failure-prone auxiliary cylinders for a self-contained, dual-stage mechanical cam track system, this precision mold delivers extreme reliability, minimal maintenance overhead, and highly stable cycle times for modern high-output manufacturing facilities.