Differential Thickness Pipe Extrusion with Segmented Mandrel Forming

Resolve Bottlenecks,
Find Innovative SolutionsGenerate Solutions

Solution Overview

Problem

Existing extrusion molding methods for differential thickness pipes face challenges in achieving a larger diameter difference between large and small diameter parts without excessive increase in processing load, especially when lengthening the pipe.

Innovation Solution

The method involves using a mandrel with small and large outer diameter regions and a sleeve to expand the base end of the raw pipe and then reduce the tip end, allowing for a larger diameter difference while maintaining manageable processing loads.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Shape

If the outer diameter of the raw pipe is increased to achieve a larger diameter difference between large and small diameter parts, then the diameter difference can be larger, but the diameter reduction rate becomes larger and processing load increases excessively

Engineering Contradiction:

Improvediameter differenceVSAvoidprocessing load

Core Design Contradiction:

ShapeVSForce

Solution Approach 1:

The mandrel is divided into multiple sections along its longitudinal axis, including a large diameter section, a small diameter section, and an intermediate section. This segmentation allows different regions of the pipe to be formed with different wall thicknesses and diameters in a single extrusion process, achieving the desired diameter difference without increasing the raw pipe outer diameter excessively.

Inventive Principle:

Principle #1Segmentation

Solution Approach 2:

The mandrel features locally varied geometry with specific sections having different diameters. The large diameter section corresponds to the thick-walled part of the pipe, while the small diameter section corresponds to the thin-walled part. This local variation in mandrel geometry creates the differential thickness pipe structure with controlled diameter difference and manageable processing load.

Inventive Principle:

Principle #3Local quality

2Shape

If the diameter reduction amount is increased to maintain the small diameter part outer diameter, then the diameter difference can be achieved, but extrusion resistance becomes larger and extrusion output must be reduced

Engineering Contradiction:

Improvediameter reduction amountVSAvoidextrusion output

Core Design Contradiction:

ShapeVSPower

Solution Approach 1:

The extrusion process is made dynamic by using a mandrel with varying diameter along its length rather than a uniform diameter. This dynamic geometry allows the extrusion resistance to vary along the pipe length, with lower resistance in regions corresponding to the small diameter section of the mandrel, thereby maintaining adequate extrusion output while achieving the required diameter reduction.

Inventive Principle:

Principle #15Dynamics

3Length of moving object

If the pipe length is increased to produce long differential thickness pipes, then the product length can be arbitrary, but contact area with the plug increases and processing load increases due to frictional force

Engineering Contradiction:

Improvepipe lengthVSAvoidfrictional force

Core Design Contradiction:

Length of moving objectVSForce

Solution Approach 1:

The mandrel is segmented into multiple longitudinal sections with different diameters. This segmentation reduces the contact area between the mandrel and the pipe wall in any given cross-section, thereby reducing frictional force. The segmented structure allows long pipes to be produced without excessive accumulation of frictional resistance along the entire length.

Inventive Principle:

Principle #1Segmentation

Solution Approach 2:

The mandrel exhibits local quality variations in its diameter along the longitudinal direction. This creates regions of different contact pressure and frictional force distribution. By strategically designing the mandrel geometry, high-friction regions are minimized and low-friction regions are maximized, enabling the production of long pipes with controlled processing load despite increased total contact area.

Inventive Principle:

Principle #3Local quality

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 production of differential thickness pipes with larger diameter differences and arbitrary length without excessive processing load, suitable for applications requiring high mechanical strength.

Implementation Method 1

expanding an outer diameter of a base end part of the raw pipe

Methodology Applied

Scientific EffectPlastic deformation: Plasticity

Implementation Method 2

pressing the end part on the base end side of the raw pipe with the sleeve to push the raw pipe into the small inner diameter region of the container to reduce the diameter of the raw pipe

Methodology Applied

Scientific EffectCompression: Compression

Data Source

PatentUS20250135518A1Extrusion molding method of differential thickness pipe and extrusion molding apparatus of differential thickness pipe

Publication Date: 2025.05.01 SANGO CO LTD

AI summary

An extrusion molding method utilizes a mandrel with a small outer diameter region having an outer diameter corresponding to a raw pipe inner diameter and a large outer diameter region having a larger outer diameter than the raw pipe inner diameter on its tip and base end sides respectively. The mandrel is pushed into the raw pipe set in a container which has a small inner diameter region having an inner diameter smaller than a raw pipe outer diameter and a large inner diameter region which has a larger inner diameter than the raw pipe outer diameter on its tip and base end sides respectively to expand a diameter of raw pipe end part on a base end side of the raw pipe. Thereafter, the base end side of the raw pipe having the mandrel inserted inside is pushed into the small inner diameter region of the container.