The injection molding machine can achieve central drawing (also known as core pulling or core drawing) by using a hydraulic or servo-driven core pull system. This is essential for molding complex parts with undercuts, internal cavities, or threaded sections that require a movable core.
How Central Drawing Works in Injection Molding
- Core Pull Mechanism:
- Mold Design Considerations:
- Application of Central Drawing:
- Machine Requirements:
A hydraulic cylinder or servo motor moves the core in and out of the mold cavity.
The core remains in place during injection and cooling.
After solidification, the core retracts to allow part ejection.
The mold must have a movable core insert.
The core pull function must be synchronized with the injection and ejection cycle.
Sliders or lifters may be used for lateral movements.
Threaded parts (bottle caps, threaded connectors)
Internal undercuts (automotive clips, snap-fit designs)
Hollow structures (pipes, medical tubes)
The injection molding machine should have core pull circuits (hydraulic or servo-driven).
Programmable control systems to manage the core pull sequence.