Inductive Mould Heating Stack with Ferrite-Free Coil Carrier
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Solution Overview
Problem
Existing tools for forming plastic materials face inefficiencies in heating and cooling processes, which affect production cycle times and product quality, and there is a need for a cost-effective solution to improve these processes.
Innovation Solution
A tool with a stack of layers including a coil carrier, an electrically conductive intermediate layer with lower resistivity than the top layer, a backing layer with lower resistivity than the top layer, and a thermal resistance layer, which efficiently conveys energy and mechanical loads, and incorporates cooling ducts and a conduction frame for improved heating and pressure equalization.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Use of energy by stationary object
If a coil carrier with ferrite granules and a top part is used for inductive heating, then heating capability is provided, but energy efficiency is insufficient due to eddy current losses in the ferrite material
Solution Approach 1:
The invention extracts and removes the ferrite granule layer from the heating structure. By eliminating this layer, the source of eddy current losses is removed, allowing the coil to directly induce currents in the workpiece or tool surface without energy-wasting intermediate losses in the ferrite material.
Solution Approach 2:
The invention applies different material properties to different locations: the coil carrier is made of non-magnetic material (avoiding eddy currents in the carrier itself), while the workpiece or tool surface retains its original magnetic properties. This localized differentiation ensures that eddy currents are generated only where needed (in the workpiece) and not in the heating structure.
2Productivity
If the top part is made thin to reduce specific heat and shorten cycles, then production cycle time is reduced, but mechanical strength and load-bearing capacity are compromised
Solution Approach 1:
The invention uses a composite structure combining non-magnetic material (for the coil carrier) with ferrite granules (for magnetic coupling). This composite approach allows the thin top part to maintain sufficient mechanical strength through the granular ferrite reinforcement while still achieving rapid heating and cooling cycles.
Solution Approach 2:
The invention prepares the heating structure in advance by pre-assembling the coil carrier with ferrite granules and cooling channels. This preliminary preparation allows the thin top part to be designed with optimized thickness and geometry that balances mechanical strength requirements with thermal response time, ensuring both durability and fast cycle times.
3Temperature
If cooling ducts are placed close to the top part surface, then cooling efficiency is improved, but the top part cannot withstand high temperatures without boiling the water in the ducts
Solution Approach 1:
The invention introduces a ferrite granule layer as an intermediary between the cooling ducts and the top part surface. This intermediate layer acts as a thermal buffer that allows efficient heat transfer from the top part to the cooling ducts while maintaining a temperature gradient that prevents the cooling water from reaching boiling temperatures, even when ducts are positioned close to the surface.
4Strength
If an intermediate ceramic layer is added to separate the coil carrier from the top part, then mechanical resistance is improved and cooling ducts can be placed in the intermediate layer, but device complexity increases
Solution Approach 1:
The invention combines multiple functions into the ferrite granule layer: it provides mechanical reinforcement to the thin top part, serves as a thermal buffer for the cooling ducts, and maintains magnetic coupling between the coil and workpiece. By consolidating these functions into a single layer, the overall structural complexity is reduced compared to using separate ceramic and cooling duct layers.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
This configuration enhances heating efficiency, allows for mechanical load handling, shortens production cycles, and improves product quality by maintaining peak temperatures and uniform pressure, reducing optical defects and increasing yield.
Implementation Method 1
The coil generates an oscillating magnetic field that, by inducing eddy currents, heats the mould or tool in the vicinity of the surface that will face the plastic material to be reshaped
Implementation Method 2
inductive heating, i.e. by means of a coil that is provided with a high-frequency AC pulse
Implementation Method 3
An electrically conductive intermediate layer is located between the coil carrier layer and the top layer, and the intermediate layer has a lower resistivity than the top layer
Implementation Method 4
Cooling may also be provided by means of a fluid such as water, which flows in the vicinity of the tool or mould surface
Data Source
AI summary
The present disclosure relates to a tool such as an injection moulding tool or an embossing tool. A heating device including a stack of layers is provided for heating a tool surface. The stack may include a coil carrier layer with a number of wound coils for generating a magnetic field, and a conductive top layer, being adjacent to the tool surface currents are induced in the top layer to heat the surface. Efficient heating may be provided by solutions involving low resistivity layers that lead currents to the top layer without themselves developing heat to any greater extent. A conduction frame device can be provided beneath the top layer and around the perimeter thereof to provide reliable contact with a backing layer.