Opening Sequence of Three-Plate Molds
A three-plate mold (also known as a three-plate injection mold) is a common structure in injection mold design, particularly suited for complex cavities and multi-cavity applications. Its structure includes the mold base, moving plate, fixed plate, ejector plate, and more. Due to the multiple actions required during the opening process, the correct opening sequence is critical to ensuring smooth mold operation, preventing damage, and enhancing production efficiency.
Overview of the Opening Sequence
The opening sequence of a three-plate mold is more complex than a two-plate mold, primarily due to its multiple plates and intricate motion mechanisms. Typically, the opening sequence involves the following stages:
Separation of the Ejector Plate and Fixed Plate:
The ejector plate detaches from the fixed plate, initiating the release of the runner system.
Separation of the Moving Plate and Fixed Plate:
The moving plate retracts from the fixed plate, opening the main parting line.
Sprue Release from the Injection System:
The sprue is pulled free from the nozzle, ensuring clean separation of the runner.
Ejection of the Workpiece:
Ejector pins advance to push the molded part out of the cavity.
Mold Closing Preparation:
All components reset to their initial positions for the next cycle.
The entire process requires coordinated movements of each component in sequence to prevent jamming, part deformation, or structural damage during operation.
Debugging and Validation of the Opening Sequence
Manual Opening Test:
Use a pry bar to simulate the opening actions, verifying that the parting surfaces separate in the designed order.
Measure the opening distances for all three stages (deviation from theoretical values ≤ 0.5mm).
Dry-Cycle Test:
Perform mold opening/closing at 30% of the injection machine’s maximum speed to observe mechanism stability.
Check plate parallelism variations with a dial indicator (fluctuation ≤ 0.02mm throughout the cycle).
Material Trial Validation:
Conduct initial trials with PP (polypropylene) material (shrinkage rate: 1.5%~2%) to reduce the risk of part sticking or surface scratches.
Monitor gate separation and ejection smoothness, adjusting timing parameters if necessary.
