# Internal Induction Heating for Local Heating in Injection Molding

## TL;DR

This paper introduces a new internal induction heating method for injection molding that improves temperature control and product quality in thin-walled polypropylene parts.

## Contribution

The novel In-IH system enables rapid, localized heating by integrating the insert into the induction circuit, enhancing efficiency and flowability.

## Key findings

- Thinner inserts achieved higher surface temperatures, with a 0.5 mm insert reaching ~550 °C.
- Narrower inserts concentrated heat better, while wider ones improved temperature uniformity.
- In-IH significantly improved PP flowability, with 85.33 mm flow length at 180 °C for a 0.4 mm specimen.

## Abstract

This study introduces Internal Induction Heating (In-IH) as an efficient method for local mold temperature control in thin-walled polypropylene (PP) injection molding. Unlike conventional systems that are slow and energy-intensive, the insert is integrated directly into the induction circuit in the In-IH system, generating eddy currents for rapid and localized heating. Numerical and experimental analyses were performed to examine the effects of insert geometry and heating parameters; it was found that thinner inserts achieved higher surface temperatures—the 0.5 mm insert reached ~550 °C, while the 2.0 mm insert reached only ~80 °C—confirming an inverse relationship between thickness and temperature. Narrower inserts (25 mm) concentrated heat more effectively, whereas wider ones yielded better temperature uniformity. The cooling conditions strongly affected the temperature gradients. Mold-filling experiments demonstrated that In-IH significantly improved the flowability of PP: at 180 °C, the 0.4 mm specimen achieved a flow length of 85.33 mm, compared with 43.66 mm for the 0.2 mm specimen. At 250–300 °C, all samples approached full filling (~100 mm). The simulation and experimental results agreed, with a maximum deviation of 10%, confirming that In-IH provides rapid, energy-efficient, and precise temperature control, thus enhancing melt flow and product quality for thin-walled PP components.