Mandrel Tool for Precision Holes in Composite Materials

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Solution Overview

Problem

Existing methods for producing holes in components made from fusible plastics and fiber-reinforced composite materials result in low precision and material weakening, respectively, due to the inability to effectively manage stress peaks and maintain structural integrity.

Innovation Solution

A tool and method utilizing a mandrel with upper and lower tool parts featuring cavities to absorb displaced material, ensuring precise hole formation with reinforced edges and reduced stress peaks, while maintaining the structural integrity of continuous fiber-reinforced plastics by distributing material effectively and allowing for the rearrangement of reinforcing fibers.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Ease of manufacture

If a heated tool is pushed through a plastic body to produce holes, then the holes can be produced with simple process, but the precision of the holes is low

Engineering Contradiction:

Improveprocess simplicityVSAvoidhole precision

Core Design Contradiction:

Ease of manufactureVSManufacturing precision

Solution Approach 1:

The tool is divided into upper and lower tool parts with a cavity between them to receive displaced material, separating the hole formation function from the material displacement management function. This segmentation allows precise hole formation while managing material flow independently.

Inventive Principle:

Principle #1Segmentation

Solution Approach 2:

The cavity is pre-formed in the tool parts before the actual hole production. This preliminary preparation of the receiving space for displaced material enables the mandrel to push material into the cavity without causing stress peaks, thereby achieving high precision hole formation.

Inventive Principle:

Principle #10Preliminary action

2Manufacturing precision

If an opening is preformed and then enlarged by a grinding tool to form a through opening in fiber-reinforced composite material, then the through opening can be produced, but the technical effort required is great and the grinding process breaks through the fibers of the material which is thereby weakened

Engineering Contradiction:

Improvethrough opening qualityVSAvoidtechnical effort

Core Design Contradiction:

Manufacturing precisionVSDevice complexity

Solution Approach 1:

The tool combines hole formation and material displacement management into a single integrated operation. The mandrel simultaneously creates the hole and pushes displaced material into the cavity, eliminating the need for separate pre-forming and enlarging steps, thereby reducing technical effort while maintaining precision.

Inventive Principle:

Principle #5Merging (Combining)

Solution Approach 2:

The displaced material that would normally cause stress peaks and weaken the material is converted into a beneficial reinforcement for the hole edge. The cavity receives this displaced material and uses it to thicken the wall around the hole, transforming the harmful stress-inducing material into a strengthening element.

Inventive Principle:

Principle #22Blessing in disguise (Convert harm into benefit)

3Productivity

If material displaced by the mandrel is not managed, then the production process is simple, but stress peaks build up in the area of the hole leading to premature material fatigue

Engineering Contradiction:

Improveproduction efficiencyVSAvoidmaterial fatigue resistance

Core Design Contradiction:

ProductivityVSReliability

Solution Approach 1:

The cavity acts as an intermediary between the mandrel and the component material. It receives and accommodates the displaced material, preventing direct contact between the mandrel and the hole edge material, thereby eliminating stress peaks while maintaining production efficiency.

Inventive Principle:

Principle #24Intermediary (Mediator)

Solution Approach 2:

The displaced material is converted from a harmful factor causing stress peaks into a beneficial reinforcement. By directing this material into the cavity where it thickens the hole edge, the invention transforms the source of potential failure into a strengthening feature that improves reliability.

Inventive Principle:

Principle #22Blessing in disguise (Convert harm into benefit)

4Reliability

If the cavity volume corresponds to the displaced material volume, then stress peaks are avoided, but the tool design becomes more complex

Engineering Contradiction:

Improvestress peak preventionVSAvoidtool design complexity

Core Design Contradiction:

ReliabilityVSDevice complexity

Solution Approach 1:

The cavity is designed with specific local geometry (circular or oval shape, constant depth or increasing depth) tailored to the specific requirements of hole reinforcement. This localized optimization achieves stress peak prevention without requiring complex overall tool design, as the cavity geometry is straightforward and easy to manufacture.

Inventive Principle:

Principle #3Local quality

Data Source

PatentEP2763826B1Tool for producing a hole in a component

Publication Date: 2018.03.28 REHAU AG & CO

Figure 1A~1B
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AI summary

The present invention relates to a tool for producing a hole (127) in a component (123) made of thermoplastic, endless fiber-reinforced and/or duroplastic materials by means of a mandrel (121), comprising an upper tool part (101) with an opening (109) for feeding through the mandrel (121) and a lower tool part (103) with an opening (111) for introducing the mandrel (121), wherein the upper and/or the lower tool part (101) (103) comprises a cavity (105) (107) at the opening (109, 111) for receiving the material displaced during the production of the hole (127).