What Is Two-Shot Molding? The Complete Guide To Two-Shot Molding Injection Molding

How Two-Shot Molding Works

The process utilizes:

1. Rotating Mold System

• The mold rotates 180° between shots

• First material is injected into cavity A

• Mold rotates to position cavity B for second injection

2. Dual Injection Units

• Two separate plasticizing units

• Can process different materials simultaneously

• Typical accuracy: <0.1mm alignment

3. Bonding Mechanism

• Materials fuse at molecular level when second shot is injected onto still-warm first shot

• Creates permanent bond stronger than adhesive

Key Advantages of Two-Shot Molding

Common Applications

1. Consumer Electronics

• Soft-touch grips on power tools

• LED light housings with opaque/transparent sections

2. Automotive

• Two-tone dashboard controls

• Sealed switch assemblies

3. Medical Devices

• Ergonomic syringe grips

• Flexible-seal rigid housings

4. Household Two-Shot Molding Products

1. Toothbrushes with flexible gum massagers

2. Kitchen utensils with non-slip handle

   
   

   Material Selection Guidelines of Two-Shot Molding

1. Compatibility Requirements:

1. Melt temperature difference <30°C

2. Similar shrinkage rates

3. Chemical bonding capability

   2. Popular Combinations:

4. PP + TPE (for flexible hinges)

5. PC + ABS (for structural parts)

6. Clear PC + Colored ABS (for lenses)

Design Considerations

1. Bonding Surface Design

• Mechanical interlocks (undercuts, dovetails)

• Minimum 0.5mm overlap

2. Gate Positioning

• Secondary gate should face away from primary material

• Avoid flow interference

3. Wall Thickness

• Maintain uniform thickness between materials

• Transition zones should be gradual

Industry Trends

• Three-Shot Molding: Emerging for more complex parts

• In-Mold Labeling: Combining decoration with molding

• Sustainable Materials: Bio-based material combinations