10 Key Details to Check During Mold Base Inspection

When reviewing our finalized drawings, we sometimes skip the full design checklist due to time constraints. However, for critical areas, we must always keep key details in mind. The following 10 points are essential for ensuring optimal mold performance and part quality.

1. Add Springs Under Return Pins

When lifters (angled lifters) contact the A-side core at the parting line, install springs or urethane pads under the return pins to ensure the ejector plate retracts first by 2–3 mm. This protects both the lifters and the parting surface from damage.

2. Add Guide Pillars for Hot Runner Systems

If the mold uses hot nozzles, guide pillars must be added to the hot runner manifold plate. These pillars should extend 20–30 mm above the nozzle tips to facilitate easy assembly/disassembly and provide alignment and protection for the nozzles.

3. Add Lifting Threads on the Clamp Plate for Hot Runner Molds

For molds with hot runners, include lifting threads (eyebolts) on the front clamp plate. This allows mold technicians to lay the mold flat during hot runner installation or removal, improving safety and efficiency.

4. Include Clearance Holes for Lifter Screws in the Bottom Ejector Plate

When designing lifters, don’t forget clearance holes for lifter block screws—not only in the top ejector plate but also in the bottom plate. Without them, disassembly becomes difficult.

5. Include Process/Assembly Screws on Ejector & Bottom Plates

In molds with many lifters, add temporary assembly screws to the ejector system to simplify lifter fitting and installation. Note: Shoulder screws on the ejector plate may remain installed, but those on the bottom plate must be removable for lifter and ejector pin alignment.

6. Add Center Springs and Guide Pins for Mold Bases Longer Than 650 mm

For mold bases exceeding 650 mm in length, install center springs and guide pins (center supports) to ensure balanced ejection, prevent lifter/ejector seizure, and reduce plate deflection.

7. Increase Ejector Plate Thickness by 5 mm for Bases ≥ 6060

For mold bases sized 6060 or larger, increase the thickness of all ejector plates by 5 mm. Even for smaller bases with numerous holes (for lifters, ejector pins, support pillars, etc.), consider adding 5–10 mm thickness to maintain structural strength.

8. Ensure Mold Base Guide Pins Retract Before Slider Angle Pins

In molds with long-stroke sliders, the angle pins can be quite long. To protect them during mold closing, the main mold base guide pins must retract before the slider angle pins engage.

9. Locate Water Inlet/Outlet on the Non-Operator Side

Place cooling water connections on the non-operator side (opposite the part ejection side) to avoid interference with part removal and improve accessibility for hose connections.

10. Mark Hot Nozzle Cooling Circuits with Identification Codes

Each hot nozzle requires its own dedicated cooling circuit. Clearly label these circuits on the mold base (e.g., G1, G2, G3…) to allow quick identification and proper connection of chilled water lines for nozzle temperature control.