How We Solved Air Trap and Part Sticking Problems in a Two Color Wheel Mold

Two Color Injection Mold Case Study: Solving Air Trap and Part Sticking in a PP+TPE Wheel Mold

Two color injection molding can provide excellent functional and aesthetic results, but multi-material products also introduce additional challenges during mold trials.

In this project, Focare Mould developed an 8+8 cavity two color injection mold for a PP+TPE wheel. During the mold trial and optimization process, two issues were identified: air trap and part sticking in the cavity.

This case study shows how our engineering team analyzed these issues and proposed targeted mold modifications to improve the molding performance.

Project Overview

The product is a bicolor wheel consisting of a rigid PP structure combined with a TPE outer section.

The mold was designed as an 8+8 cavity bicolor mold and tested on a Yizumi 360T injection molding machine.

Mold Specifications

Challenge 1: Air Trap During Injection Molding

During the mold trial, an air trap was observed on the molded product.

Air trapping is an important issue to address during injection molding because trapped air can affect the appearance and consistency of the molded part.

For a multi-cavity two color mold, proper venting is especially important because the mold must maintain stable molding conditions across multiple cavities.

Focare's Modification

After evaluating the problem, our team proposed a targeted cavity modification.

The solution was to reduce 0.015 mm thickness in the cavity of both the first and second injection to improve the venting condition.

Modification

Before:
Air trap was observed on the molded wheel during the mold trial.

Action:
0.015 mm cavity thickness adjustment was proposed for both the first and second injection.

Purpose:
Improve mold venting and reduce trapped air during injection.

Challenge 2: Part Sticking in the Cavity

Another issue identified during the mold trial was that the molded products were being held in the cavity, creating a part-release problem.

Reliable part release is particularly important for an 8+8 cavity mold, where stable and repeatable ejection is necessary for production.

Focare's Modification

To address the sticking issue, our team proposed another localized cavity adjustment.

For the second injection cavity, we suggested reducing the thickness by 0.15 mm to address the sticking problem.

Modification

Before:
The molded product was held in the cavity.

Action:
0.15 mm thickness adjustment was proposed in the second injection cavity.

Purpose:
Improve part release during the molding process.

Engineering Optimization for PP+TPE Two Color Molding

This project demonstrates why mold trials are an important part of two color injection mold development.

A mold may have the correct basic structure, runner system and injection configuration, but actual molding conditions can reveal localized issues that require further optimization.

For mold , the optimization work focused on two specific areas:

1.Venting improvement for the air trap issue

2.Cavity adjustment for the part sticking issue

Instead of making broad changes to the mold, Focare Mould proposed targeted modifications based on the actual problems observed during the trial.

This approach helps optimize the mold while maintaining the original two color mold design and production concept.

Looking for a Two Color Mold Manufacturer?

Focare Mould specializes in the design and manufacturing of two color molds, 2K injection molds and multi-material injection molds for household products, handles, wheels, containers and other plastic applications.

If you are developing a PP+TPE product or experiencing molding challenges with an existing two color mold project, our team can review your product design and provide a preliminary mold solution.

Contact Focare Mould for your next two color injection mold project.