Eddy Current Sensor for Machine Tool Runout Detection
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Conventional eddy current sensors in automatic tool changers face detection accuracy issues when the tool change operation is performed at higher speeds due to increased runout, leading to potential collisions and damage, and the need to increase the gap between the sensor and the tool complicates accurate detection.
Innovation Solution
An eddy current sensor with a spiral-shaped coil and a soft magnetic core disposed at the axial center, configured to face the tool holder's outer peripheral surface, allows for increased detection distance without compromising accuracy by enhancing magnetic flux density and directivity.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the gap between the eddy current sensor and the tool is increased to prevent collision during high-speed tool change operations, then the reliability of the tool changer is improved, but the detection accuracy of the eddy current sensor deteriorates
Solution Approach 1:
The patent applies parameter changes by modifying the physical dimensions of the eddy current sensor components. Specifically, it increases the coil diameter from conventional sizes to 3-8mm, and extends the core length to 2-5mm, thereby changing the sensor's detection characteristics to achieve both increased detection distance and maintained accuracy
Solution Approach 2:
The patent uses composite construction by combining a spiral coil with a soft magnetic core in a specific configuration. The coil is wound in a spiral pattern around a cylindrical soft magnetic core, creating a composite structure that enhances magnetic flux density and extends detection range while maintaining precision
2Productivity
If the tool change operation is performed at higher speed to reduce cycle time, then the productivity is improved, but the runout of the tool increases causing collision risk
Solution Approach 1:
The patent applies beforehand cushioning by designing the eddy current sensor with extended detection distance capability, which acts as a buffer zone. This allows the sensor to detect tool runout and potential collisions from a safer distance, enabling higher tool change speeds while maintaining reliability through early detection and warning
3Length of stationary object
If the coil diameter is increased to extend detection distance, then the gap between sensor and tool can be increased, but the sensor size and complexity increase
Solution Approach 1:
The patent applies nested doll principle by placing the spiral coil around a cylindrical soft magnetic core, with the coil winding nested concentrically around the core. This nested configuration allows the detection function to be extended while keeping the overall sensor structure compact and manageable, avoiding excessive complexity
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
Prevents collisions between the sensor and the tool while maintaining detection accuracy by increasing the gap, ensuring reliable operation even at higher tool change speeds.
Implementation Method 1
an eddy current sensor which is disposed so as to face an outer peripheral surface of a flange (11B) of the tool holder (11) with a predetermined gap (distance) therebetween and detects the outer peripheral surface of the flange (11B) as electrical signals of displacement
Implementation Method 2
the eddy current sensor includes a coil formed in a spiral shape and held in a bobbin serving as a cylindrical container, and a core serving as a soft magnetic body disposed at an axial center of the coil
Data Source
Figure 1(a)~1(c)
Figure 2
Figure 3
AI summary
A machine tool with an automatic tool changer that mounts a tool holder 11 to which a tool 25 is attached on a spindle head 26 and machines a workpiece 24 includes an eddy current sensor 1 disposed such that a measurement end surface 1-4 faces the outer peripheral surface of a flange 11B of the tool holder 11, and a data processor 3 that detects runout of a tool 25-1 mounted on the spindle head 26 based on data obtained by measurement by the eddy current sensor 1. The eddy current sensor 1 includes a coil 1-2 formed in a spiral shape and held in a bobbin 1-3 serving as a cylindrical container, and a core 1-1 serving as a soft magnetic body disposed at the axial center of the coil 1-2 on the measurement end surface 1-4 side. The machine tool can perform a tool change operation at a higher speed without compromising the detection accuracy.