Insert Molding Complex Geometries Sacrificial Material

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Solution Overview

Problem

Injection molding of complex parts with undercuts and varying wall thicknesses faces challenges such as difficulty in forming undercuts and warpage due to shrinkage, which can lead to deformation and sink marks, especially when thicker and thinner portions meet during the molding process.

Innovation Solution

The method involves using insert molding, where preformed inserts with sacrificial material are overmolded and then machined to create the desired geometry, allowing for the formation of complex geometries with undercuts and varying thicknesses without the shrinkage issues associated with traditional molding processes, using the same polymer material for compatibility and bonding.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Manufacturing precision

If traditional injection molding is used to form complex parts with undercuts and varying wall thicknesses, then the molding process is simple, but the parts suffer from warpage, deformation, and sink marks due to shrinkage

Engineering Contradiction:

Improvedimensional accuracyVSAvoidmolding process complexity

Core Design Contradiction:

Manufacturing precisionVSDevice complexity

Solution Approach 1:

The part is divided into multiple segments: a base layer molded first, followed by insert pieces positioned in specific locations, and then additional material molded over the inserts. This segmentation allows different regions to be optimized independently - the base layer provides structural support while insert pieces create localized thickness variations and undercut features without causing warpage in the entire part.

Inventive Principle:

Principle #1Segmentation

Solution Approach 2:

Insert pieces are pre-formed with sacrificial material before being placed in the mold. These inserts are positioned in advance to define the desired final geometry, including undercut regions. The sacrificial material is then removed after molding, leaving the desired complex geometry. This preliminary action allows complex features to be created without the shrinkage issues of molding thick sections directly.

Inventive Principle:

Principle #10Preliminary action

2Strength

If thicker sections are molded to avoid warpage, then structural integrity is improved, but sink marks and deformation occur when thicker and thinner portions meet

Engineering Contradiction:

Improvestructural integrityVSAvoidsurface quality

Core Design Contradiction:

StrengthVSManufacturing precision

Solution Approach 1:

Different regions of the part have different thicknesses and material properties as intended by design. The insert pieces create localized thick sections only where needed for structural support or to create specific geometric features like undercuts. The base layer maintains uniform thickness for cosmetic surfaces. This local differentiation avoids the sink marks that occur when trying to maintain uniform thickness throughout the entire part.

Inventive Principle:

Principle #3Local quality

3Adaptability or versatility

If tool actions are used to form undercuts, then the molding process is straightforward, but complex undercut geometries are difficult or impossible to achieve

Engineering Contradiction:

Improvegeometric complexityVSAvoidmolding process simplicity

Core Design Contradiction:

Adaptability or versatilityVSEase of manufacture

Solution Approach 1:

Sacrificial material serves as an intermediary to create undercut geometries. The insert pieces are molded with sacrificial material in regions that will become undercuts. After the part is molded and ejection, the sacrificial material is removed (via machining, drilling, or other removal methods), creating the desired undercut geometry. This intermediary approach allows complex undercuts to be formed without requiring complex mold tool actions.

Inventive Principle:

Principle #24Intermediary (Mediator)

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 approach enables the creation of robust injection molded articles with complex geometries and varying thicknesses, preventing warpage and allowing for the formation of undercuts that would be difficult or impossible with traditional tool actions, while ensuring a strong thermal and mechanical bond between layers.

Implementation Method 1

a molded article is made by injecting a softened material into a mold and then hardening the material in the mold

Methodology Applied

Scientific EffectInjection molding:

Implementation Method 2

injecting a softened material into a mold and then hardening the material in the mold

Methodology Applied

Scientific EffectHardening: Phase Change

Data Source

PatentUS12122077B2Forming complex geometries using insert molding

Publication Date: 2024.10.22 MICROSOFT TECHNOLOGY LICENSING LLC

AI summary

Examples are disclosed herein that relate to creating undercuts and other complex geometries in an injection molded article. One example provides a method of forming an injection molded article comprising an undercut structure, the method comprising inserting an insert piece into a mold for forming the molded article, the insert piece comprising sacrificial material, injection-molding the molded article, thereby incorporating the insert piece into the injection molded article, and machining the insert piece to form the undercut structure from the sacrificial material.