Dual-Cast Slush Mold Design for Recyclable Interior Trim

Solution Overview

Problem

Traditional slush molding processes for automotive interior skins, such as instrument panels and door uppers, result in high scrap rates and non-recyclable materials, with the foam-in-place process being time-consuming and inefficient.

Innovation Solution

A dual cast slush mold system involving a mold with a negative and positive side, using two polymeric powder boxes to form dual polymer layers, where the second layer expands and is compressed to a specific thickness, followed by cooling and removal, reducing cycle time and scrap while enabling recyclability.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Manufacturing precision

If traditional foam-in-place process is used after slush molding, then the skin can be formed with desired haptics, but the process becomes time-consuming and generates high scrap rates

Engineering Contradiction:

Improvehaptic qualityVSAvoidcycle time

Core Design Contradiction:

Manufacturing precisionVSProductivity

Solution Approach 1:

The patent combines the skin forming and foam creation into a single integrated slush molding process. Two polymeric powders are simultaneously molded in the same mold cavity, where one polymer forms the skin layer and the other forms the foam layer, eliminating the need for separate foam-in-place operations and reducing cycle time.

Inventive Principle:

Principle #5Merging (Combining)

Solution Approach 2:

The invention uses composite material structure with two different polymeric powders having distinct properties. The first polymer provides the skin layer with desired surface characteristics and haptics, while the second polymer provides the foam layer with appropriate density and cushioning properties, achieving multiple functions in a single molded part.

Inventive Principle:

Principle #40Composite materials

2Manufacturing precision

If traditional foam-in-place process is used after slush molding, then the skin can be formed with desired haptics, but scrap rates increase to 40% and materials become non-recyclable

Engineering Contradiction:

Improvehaptic qualityVSAvoidscrap rate

Core Design Contradiction:

Manufacturing precisionVSLoss of substance

Solution Approach 1:

The patent combines the skin forming and foam creation into a single integrated slush molding process. Two polymeric powders are simultaneously molded in the same mold cavity, where one polymer forms the skin layer and the other forms the foam layer, eliminating the need for separate foam-in-place operations and reducing cycle time.

Inventive Principle:

Principle #5Merging (Combining)

Solution Approach 2:

The invention enables full recyclability of the molded parts. Since both layers are formed from polymeric powders in a single molding process without adhesives or foaming chemicals, the entire part can be ground and reprocessed into new parts, eliminating the 40% scrap rate associated with traditional multi-step processes.

Inventive Principle:

Principle #34Discarding and recovering

3Ease of manufacture

If calendar roll foam is cut, heated and glued onto the skin, then the foam and skin can be assembled, but the process is time-consuming and creates non-recyclable composite materials

Engineering Contradiction:

Improveassembly capabilityVSAvoidcycle time

Core Design Contradiction:

Ease of manufactureVSProductivity

Solution Approach 1:

The patent combines the skin forming and foam creation into a single integrated slush molding process. Two polymeric powders are simultaneously molded in the same mold cavity, where one polymer forms the skin layer and the other forms the foam layer, eliminating the need for separate foam-in-place operations and reducing cycle time.

Inventive Principle:

Principle #5Merging (Combining)

Solution Approach 2:

The invention performs preliminary action by pre-forming both the skin and foam layers with precise geometry during the initial molding process. The mold cavity is designed to create the final part shape with both layers already in their correct positions and configurations, eliminating the need for subsequent cutting, heating, and gluing operations.

Inventive Principle:

Principle #10Preliminary action

4Device complexity

If single layer slush molding is used, then the process is simple, but the part lacks the desired foam structure and haptic properties

Engineering Contradiction:

Improveprocess simplicityVSAvoidfoam structure quality

Core Design Contradiction:

Device complexityVSManufacturing precision

Solution Approach 1:

The invention uses composite material structure with two different polymeric powders having distinct properties. The first polymer provides the skin layer with desired surface characteristics and haptics, while the second polymer provides the foam layer with appropriate density and cushioning properties, achieving multiple functions in a single molded part.

Inventive Principle:

Principle #40Composite materials

Solution Approach 2:

The patent applies partial action by selectively melting different portions of the two polymeric powders to different extents. The first polymer is melted to form a smooth skin layer, while the second polymer is melted to a lesser extent to create the foam structure, achieving both skin and foam properties in a single process.

Inventive Principle:

Principle #16Partial or excessive action

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

The system significantly reduces cycle time, scrap, and costs, producing parts with better radius definition and allowing for 100% recyclability, eliminating the need for gluing foam layers.

Implementation Method 1

heating the mold, in a pre-cast heating step, to a pre-cast temperature

Methodology Applied

Scientific EffectHeating: Heating

Implementation Method 2

at least a portion of the first polymeric powder melts and forms a first polymer layer on the negative side of the mold

Methodology Applied

Scientific EffectMelting: Melting

Implementation Method 3

heating the mold, in a post-cast heating step, to a post-cast temperature

Methodology Applied

Scientific EffectHeating: Heating

Implementation Method 4

During the post-cast heating step, the second polymer layer expands from a first thickness to a second thickness

Methodology Applied

Scientific EffectThermal expansion: Thermal Expansion

Implementation Method 5

The mold is then cooled and the trim panel is removed from the mold

Methodology Applied

Scientific EffectCooling: Cooling

Data Source

PatentEP4617035A1Dual cast slush mold system, methods, and apparatuses

Publication Date: 2025.09.17 CPK INTERIOR PROD INC

Figure 1~2
Figure 3
Figure 4

AI summary

Methods, systems, and apparatuses of manufacturing an automotive interior trim panel are provided. The method includes providing a mold having a negative side and a positive side, heating the mold using a first heater and a second heater, coupling the mold to a first powder box containing a first polymeric powder, molding a first polymer layer on the first side of the mold by rotating the mold, coupling the mold to a second powder box containing a second polymeric powder, and molding a second polymer layer on the first polymer layer by rotating the mold. The method further includes heating the second polymer layer during which the second polymer layer expands, compressing the thickness of the second polymer layer, cooling the positive side of the mold to reduce the temperature of the first polymer layer and the second polymer layer, and removing the part from the mold.