Simulating Two-Shot Injection Molding with 3DEXPERIENCE

The two-shot injection molding process has transformed the plastic product design and manufacturing by allowing you to create parts of two different materials. This innovative technology provides the best of both rigid plastic for strength and softer plastic for comfort without having to create multiple components.

Modeling a multi-material part is a breeze in SOLIDWORKS, but how do you accurately simulate the two-shot injection molding process? The Plastic Injection Engineer role on 3DEXPERIENCE streamlines the simulation and analysis of multi-material plastic injection molded parts.

What is Two-Shot Injection Molding?

The process of two-shot or dual-shot molding consists of two different polymers being sequentially injected into separate cavities during the same manufacturing cycle. This results in a single well-integrated part made of two materials. The first shot creates the base structure, while the second shot adds a complementary material, mostly for functional enhancements or ergonomics.

In the example shown above, injection of the blue material starts in the left mold cavity, while injection of the red material starts in the right cavity. The right cavity already contains a part filled with the blue material before the injection molding machine begins to inject the red material.

Common Applications for Two-Shot Injection Molding

Common applications include toothbrush handles, automotive interior components, and consumer electronics. While the benefits of the two-shot molding process are clear, the process introduces complexity, such as material incompatibility resulting in less effective bonding, volumetric shrinkage or warp, short shots, or flash.

How Can Plastic Injection Engineer on 3DEXPERIENCE Help?

The Plastic Injection Engineer role on the 3DEXPERIENCE platform can help simulate the two-shot injection molding to precisely identify any defects before manufacturing. This role provides a comprehensive suite of tools for simulating injection molding processes.

The workflow for two-shot injection molding simulation for a brush handle using 3DEXPERIENCE consists of the following:

1. Assign domains to the contributing parts that are included in the simulation.
   A domain characterizes the type of component of an injection molding machine that is included in a simulation. A domain must be assigned to all geometries that contribute to a simulation. Types of domains include Plastic for mold cavities, Hot or Cold Runners, Part Inserts, and Coolant and Mold Inserts.
   

   Assigning the Plastic domain to the Handle part

2. Apply the injected plastic materials to the cavity.
3. Adjust the Process Settings.
   This option lets you specify the operational settings of an injection molding machine. The Fill, Pack, and Warp process settings are defined for the two-shot molding process based on the type of multi-shot molding. For the Fill Simulation settings, the fill rate profile can be defined as a function of time or as a percentage of the filled cavity volume.
   

   Injection molding Process Settings dialog

4. Define injection locations.
   Injection locations are defined to represent the locations where plastic materials are injected into the cavity. Any surface or a point on the part can be selected for the injection location.
   

   Plastic injection locations for both materials

5. Mesh the parts in the study.
   A tetrahedral hybrid mesh can be defined, capturing the geometry of the components, and mesh control can be defined as required. For models that have multiple bodies and share common boundaries, there is a chance that the meshes at the interfaces are non-conformal or mismatched nodes. To reduce instances of non-conformal meshes, you can specify a source geometry to project its mesh onto target geometries, using the mesh capture order, based on their coincident interfaces.
   

   The final meshed model for injection molding

6. Run the Fill, Pack, and Warp plastic simulation.
   By default, the simulation runs on the local machine using an embedded license. You can select up to eight cores per CPU to run the simulation, but you can utilize the cloud-based solver for more processing power.

Gaining Injection Molding Insight from 3DEXPERIENCE

Using the 3DEXPERIENCE SIMULIA tools, you can extract several different result plots, such as fill time, pressure, or temperature at the end of a study. Additionally, pack, sink marks, and displacement due to warpage can be generated. Gate locations, runner size, and material choice can be adjusted based on the insights gained from injection molding simulation.

Result plot for injection molding fill time

This example is just one of the applications of the Plastic Injection Engineer role. By integrating simulation into the design process, manufacturers can innovate faster, reduce costs, and deliver superior products.

To get started with leveraging 3DEXPERIENCE, learn more about SOLIDWORKS Cloud Services here.