Numerical Controller Tool Failure Detection From Processing Force

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Solution Overview

Problem

Existing industrial machinery faces challenges in accurately detecting tool failure, particularly when main shaft torque is low, leading to bulky and expensive setups, and existing sensor-based solutions are unreliable.

Innovation Solution

The implementation of a system that includes a drive mechanism, motor, position sensors, a current controller, servo controller, and a numerical controller, which calculates processing force components to determine tool failure based on threshold values and frequency analysis, eliminating the need for additional sensors.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Device complexity

If main shaft torque is used to detect tool failure, then the detection method is simple, but the detection accuracy is poor when torque is small

Engineering Contradiction:

Improvedetection method simplicityVSAvoidtool failure detection accuracy

Core Design Contradiction:

Device complexityVSMeasurement precision

Solution Approach 1:

The processing force is segmented into multiple frequency components (first component with frequency lower than predetermined frequency, second component with frequency equal to or higher than predetermined frequency). This segmentation allows different frequency components to be analyzed separately, enabling accurate tool failure detection even when the overall torque signal is small, while still using the existing main shaft torque sensor without adding new sensors.

Inventive Principle:

Principle #1Segmentation

2Measurement precision

If an additional sensor is attached to detect cutting state, then tool failure detection accuracy is improved, but the machinery becomes bulky and expensive

Engineering Contradiction:

Improvetool failure detection accuracyVSAvoidmachinery structure

Core Design Contradiction:

Measurement precisionVSDevice complexity

Solution Approach 1:

The existing main shaft torque sensor and control system are made multi-functional by implementing frequency component analysis software in the numerical controller. This allows the existing hardware to perform both its original torque measurement function and the new tool failure detection function, eliminating the need for additional sensors while maintaining high detection accuracy.

Inventive Principle:

Principle #6Universality (Multi-functionality)

Solution Approach 2:

The mechanical solution of adding physical sensors is replaced with a signal processing approach using frequency component analysis. The numerical controller processes the existing torque signal by separating it into frequency components, substituting the need for additional mechanical sensing hardware with computational analysis of the existing signal.

Inventive Principle:

Principle #28Mechanics substitution (Replace mechanical system)

3Reliability

If an additional sensor is attached to detect cutting state, then tool failure detection capability is improved, but the cost increases

Engineering Contradiction:

Improvetool failure detection capabilityVSAvoidmachinery cost

Core Design Contradiction:

ReliabilityVSEase of manufacture

Solution Approach 1:

The numerical controller performs self-service by implementing the frequency component analysis function within its existing processing capabilities. The system uses its own computational resources to analyze the torque signal and detect tool failure, eliminating the need for additional detection hardware and reducing overall system cost while maintaining reliable detection capability.

Inventive Principle:

Principle #25Self-service

4Measurement precision

If a sensor is used to detect tool failure, then detection accuracy is improved, but the system reliability decreases when the sensor fails

Engineering Contradiction:

Improvetool failure detection accuracyVSAvoiddetection system reliability

Core Design Contradiction:

Measurement precisionVSReliability

Solution Approach 1:

The system uses feedback from the existing torque sensor combined with frequency component analysis to continuously monitor tool condition. By analyzing the spectral characteristics of the torque signal, the system can detect tool failure patterns that are distinct from normal operation, maintaining high detection accuracy while using the already-reliable existing sensor infrastructure.

Inventive Principle:

Principle #23Feedback

Data Source

PatentUS11256229B2Industrial machinery and control method thereof

Publication Date: 2022.02.22 SHIBAURA MASCH CO LTD

AI summary

An industrial machinery includes: a drive mechanism driving a control target that moves work or a tool; a motor; a first sensor detecting a position of the control target; a second sensor detecting a position of the motor; a current controller controlling a supply current to the motor; a servo controller outputting a torque instruction to the current controller; and a numerical controller calculating a processing force of the control target to the work based on position information on the control target acquired from the first sensor, position information on the motor acquired from the second sensor, and the torque instruction, the numerical controller determining that the tool is in failure if an absolute value of a first component of the processing force becomes equal to or larger than a first threshold value while processing the work, the first component having a frequency lower than a predetermined frequency.