Non-Magnetic Digital Micrometer for Measuring Strong Magnets

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Solution Overview

Problem

Existing small measuring devices, such as micrometers, struggle to accurately measure strong magnets due to magnetic attraction and the difficulty in machining non-magnetic materials with high accuracy, particularly in forming threads on spindles and frames.

Innovation Solution

A digital micrometer with a main-body frame and spindle made of non-magnetic materials like austenitic stainless steel, using a thimble part with a spiral groove and engaging pin mechanism to move the spindle, and a displacement detector to ensure accurate measurement, while avoiding magnetic interference.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Productivity

If a small measuring device is used to measure a strong magnet, then the device should be compact and convenient, but the device gets strongly stuck to the magnet due to magnetic attraction

Engineering Contradiction:
Improvemeasurement efficiencyVSAvoidmagnetic attraction
Core Design Contradiction:
ProductivityVSObject-affected harmful factors

Solution Approach 1:

The harmful magnetic material (ferromagnetic components) is extracted and removed from the measuring device structure. The device uses non-magnetic materials for the frame, spindle, and all internal components, eliminating the source of magnetic attraction while maintaining the compact measuring device design for efficient measurement of strong magnets

Inventive Principle:
Principle #2Taking out (Extraction)

Solution Approach 2:

The magnetic properties of the device materials are changed from ferromagnetic to non-magnetic. By selecting materials with specific magnetic parameters (non-magnetic), the device eliminates harmful magnetic interactions while maintaining structural integrity and measurement functionality

Inventive Principle:
Principle #35Parameter changes

2Object-affected harmful factors

If the frame and spindle are made of non-magnetic material, then magnetic attraction is avoided, but machining accuracy becomes difficult to achieve

Engineering Contradiction:
Improvemagnetic attractionVSAvoidthread machining accuracy
Core Design Contradiction:
Object-affected harmful factorsVSManufacturing precision

Solution Approach 1:

The device employs composite construction combining non-magnetic materials (austenitic stainless steel, aluminum alloy, or resin) with precise mechanical features. The frame and spindle use non-magnetic materials to eliminate magnetic attraction, while threaded portions and precision surfaces are machined to high accuracy standards, achieving both material property requirements and manufacturing precision

Inventive Principle:
Principle #40Composite materials

Solution Approach 2:

Different regions of the non-magnetic components have optimized local properties. The frame and spindle body use non-magnetic materials to avoid magnetic attraction, while specific localized areas (threaded portions, measurement surfaces) are precision-machined to achieve required manufacturing accuracy, combining material properties with localized precision features

Inventive Principle:
Principle #3Local quality

3Object-affected harmful factors

If a large measuring machine is used to avoid magnetic attraction, then measurement can be performed, but manufacturing efficiency and cost are considerably affected

Engineering Contradiction:
Improvemagnetic attractionVSAvoidmanufacturing efficiency
Core Design Contradiction:
Object-affected harmful factorsVSProductivity

Solution Approach 1:

The harmful magnetic components are extracted from the measuring device, enabling a compact design that eliminates the need for large measuring machines. This allows efficient measurement of strong magnets using a portable, hand-held device, significantly improving manufacturing efficiency and reducing costs compared to large coordinate measuring machines

Inventive Principle:
Principle #2Taking out (Extraction)

Data Source

PatentEP3812694B1Digital micrometer
Publication Date: 2025.08.06 MITUTOYO CORP
  • EP3812694B1 patent drawingFigure 1
  • EP3812694B1 patent drawingFigure 2
  • EP3812694B1 patent drawingFigure 3

AI summary

There is provided a digital micrometer suitable for measuring an object to be measured that is a strong magnet. A digital micrometer includes a main-body frame, a spindle, a thimble part, and a displacement detector that detects displacement of the spindle. The main-body frame includes an U-shaped frame part, and a spindle holding part provided on the other end side of the U-shaped frame part and having a length in a direction away from an anvil. The spindle is held by a spindle holding part, provided to be movable forward and backward in an axial direction with respect to the anvil, and includes a contactor on one end face. The main-body frame and the spindle are formed of a non-magnetic material.