How to Design the Undercut Mold?

An undercut mold is a type of mold specifically designed to mold products with an inverted structure. The undercut structure refers to a partially reversed or recessed area on the surface of the part, which makes it impossible to demolding the part from the mold without a special design. To overcome this problem, undercut molds are designed with a special mechanism to achieve smooth demolding of the part from the mold.

Features of Undercut Molds

Special Demoulding Mechanism: To cope with the undercut structure, the mold is often equipped with a slider, a lifter, a core pulling mechanism, etc.
Complex mold structure: Compared with ordinary molds, the structure of undercut molds is more complex and requires higher part precision.
Higher Processing and Maintenance Costs: Due to the difficulty in design and manufacturing, the cost of undercut molds is also increased accordingly.

Common Applications of Undercut Molds

Auto Parts: Such as bumpers, dashboards, etc.
Household Appliance Housings: Such as washing machines and refrigerator housings.
Consumer Electronics: Such as mobile phone housings and remote control housings.
Medical Devices: Such as complex surgical instruments and housings.

Design Method of Undercut Mold

1. Analyze Product Structure

Determine Undercut Area: Mark all reverse structures in the product that need special treatment.
Calculate Undercut Angle: When the undercut angle is small, direct molding can be achieved through appropriate demolding force; when the undercut angle is large, a demoulding mechanism needs to be designed.

2. Select Demolding Mechanism

Slider Mechanism

Suitable for lateral undercuts.
The slider moves sideways when the mold is opened to demolding the undercut area.

Ejector Mechanism:

Suitable for Smaller Undercut Structures.
The demoulding of the undercut area is achieved through the tilt angle and ejection action of the ejector rod.

Core Pulling Mechanism:

Suitable for internal undercuts.
Undercuts are released by threaded core pulling or other mechanical means.

3. Design the Gating System

Gate Location: Close to the undercut area to ensure uniform filling.
Cold Runner or Hot Runner: Choose the appropriate runner type to reduce material waste.

4. Cooling System Design

Due to the complex structure of the undercut mold, the layout of the cooling system is more important.
Design cooling channels around moving parts such as sliders and lifters to avoid local overheating.
Optimize the cooling water path to ensure uniform temperature of the entire mold.

5. Mold Flow Analysis and Optimization

Verify the Filling Effect of the Undercut Area: ensure that the material can be fully filled.
Optimize the Demoulding Force: Evaluate the possible stress concentration during the molding process through mold flow analysis.

Multi-cavity Mold: Cooling System Design

Cooling Channel Layout: Cooling channels should be as close as possible to the cavity surface while avoiding affecting the strength of the mold.
Uniform Cooling: Ensure that the cooling rate of all cavities is consistent to avoid deformation or warping of the part.
Cooling Medium Selection: Select cooling water or oil according to the material and design a fast circulation system.

Common Problems and Solutions for Undercut Mold Design

Excessive Demoulding Force

Solution: Optimize the angle of the top or slider to reduce friction in the undercut area.

Mold Wear

Solution: Use high-hardness materials to make sliders and top parts, and lubricate them regularly.

Product Deformation or Warping

Solution: Improve the design of the cooling system to ensure uniform temperature.

Poor Undercut Filling

Solution: Adjust the gate position or increase the injection pressure.

Design Example Of Undercut Mold

Take the automobile bumper mold as an example. Its undercut structure is usually located on the side and inside of the part.

Slider Design: The slider releases the lateral undercut through the movement of the guide rail.
Cooling Layout: Cooling water channels are arranged inside the slider to ensure the cooling effect.
Mold Steel Selection: Select materials with high wear resistance and corrosion resistance (such as H13 steel).

Undercut mold design requires sufficient technical experience and a deep understanding of product structure. From analyzing the undercut structure to selecting the demoulding mechanism, and then to mold optimization, each step requires careful planning and execution. We are a professional undercut mold manufacturer. If you need a competitive inquiry, please feel free to contact us!