Pump Impeller Injection Molding with Segmented Core Removal

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Solution Overview

Problem

The manufacture of pump impellers with complex, aerodynamically optimized flow channels is challenging due to undercuts that prevent the use of lost cores, making it difficult to produce closed impellers in one piece by injection molding without additional assembly steps.

Innovation Solution

The method involves using reusable cores divided into parts that can be removed radially along a curved path, creating free space to disengage from undercuts, allowing for the formation of complex flow channel geometries without lost cores, enabling one-piece injection molding of pump impellers from plastic or metal.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Shape

If lost cores are used to form complex flow channels with undercuts, then complex flow channel geometries can be achieved, but the manufacturing process becomes more complex and costly

Engineering Contradiction:

Improveflow channel geometryVSAvoidmanufacturing process complexity

Core Design Contradiction:

ShapeVSDevice complexity

Solution Approach 1:

The core is divided into multiple separable parts (first core part and second core part) that can be removed independently. The first core part is removed radially outward to create free space, enabling the second core part to be disengaged from undercuts by moving into this free space. This segmentation allows complex flow channel geometries to be formed with reusable cores rather than lost cores.

Inventive Principle:

Principle #1Segmentation

2Shape

If impellers are assembled from several parts to accommodate complex flow channels, then complex geometries can be achieved, but assembly steps and manufacturing costs increase

Engineering Contradiction:

Improveflow channel geometryVSAvoidmanufacturing simplicity

Core Design Contradiction:

ShapeVSEase of manufacture

Solution Approach 1:

Inventive Principle:

Principle #1Segmentation

3Ease of manufacture

If integral cores are used for injection molding, then manufacturing is simpler, but complex flow channel shapes with undercuts cannot be formed

Engineering Contradiction:

Improvemanufacturing simplicityVSAvoidflow channel geometry

Core Design Contradiction:

Ease of manufactureVSShape

Solution Approach 1:

Inventive Principle:

Principle #1Segmentation

Solution Approach 2:

The removal process utilizes multiple dimensions: the first core part is removed in the radial direction, creating free space that allows the second core part to move in a combination of radial and axial directions to disengage from undercuts. This multi-dimensional removal approach enables complex geometries that cannot be achieved with single-direction core removal.

Inventive Principle:

Principle #17Another dimension (Dimensionality change)

4Ease of manufacture

If reusable cores are used instead of lost cores, then costs are reduced, but complex flow channel geometries with undercuts cannot be formed

Engineering Contradiction:

Improvemanufacturing costVSAvoidflow channel geometry

Core Design Contradiction:

Ease of manufactureVSShape

Solution Approach 1:

Inventive Principle:

Principle #1Segmentation

Solution Approach 2:

Inventive Principle:

Principle #17Another dimension (Dimensionality change)

Data Source

PatentEP2202044B2Method for injection moulding of a pump propeller

Publication Date: 2014.05.07 GRUNDFOS MANAGEMENT AS

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AI summary

The method comprises forming a core, which defines flow channel (8) in interior of an impeller (1), from two core parts from which a first core part is extracted along a curved web radial from the flow channel after injection molding process and subsequently a second core part (26) carries an additional relative movement between the impeller and the second core part in a direction transverse to pulling direction of the second core part before or during the extracting process. The pulling direction of the two core parts passes radial towards outside along a curved web. The method comprises forming a core, which defines flow channel (8) in interior of an impeller (1), from two core parts from which a first core part is extracted along a curved web radial from the flow channel after injection molding process and subsequently a second core part (26) carries an additional relative movement between the impeller and the second core part in a direction transverse to pulling direction of the second core part before or during the extracting process. The pulling direction of the two core parts passes radial towards outside along a curved web in longitudinal direction of the flow channel. The two core parts of the core, which define the flow channel in the interior of the impeller lie to each other in axial direction or circumferential direction related to the impeller-rotation axis and carry the relative movement between the impeller and core part in axial direction or in circumferential direction. The relative movement is carried out between the impeller and the core part. The impeller is freely movable in a direction transverse to pulling direction of the core parts. The core has three core parts, where two core parts are movably mounted on different parts of external tool. The first core part is subjected on a first part of the external tool and the second core part is subjected on a second part of the external tool. The first and second part of the tool are moved to each other after the pulling process. The two core parts are guidable to each other.