Shaft Encoder Contact Detection for Accurate Workpiece Positioning
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Solution Overview
Problem
Current methods for determining the position of a workpiece in machine tools are time-consuming and prone to measurement errors due to residual slag and large tolerances, especially when using cast components, which can lead to incomplete material removal and extended machining times.
Innovation Solution
A device and method utilizing a measuring arrangement with a measuring scale and position encoders on a shaft, combined with a processing device that evaluates position values to determine contact between a tool and workpiece, allowing for precise detection of shaft deflection and rotation, thereby facilitating accurate positioning and machining.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If a probe is used to determine workpiece position by contact, then the workpiece position can be measured, but the measurement is inaccurate due to residual slag on cast components
Solution Approach 1:
The patent replaces the mechanical contact-based probe measurement system with a vibration-based measurement system. A vibration exciter generates vibrations in the tool, and vibration sensors detect these vibrations. The vibration characteristics change when the tool contacts the workpiece surface, allowing detection without relying on mechanical probe contact that is affected by residual slag.
Solution Approach 2:
The patent utilizes mechanical vibration as the core measurement principle. A vibration exciter generates controlled vibrations in the tool, and vibration sensors detect changes in vibration amplitude, frequency, or phase that occur when the tool contacts the workpiece surface. This vibration-based approach can distinguish between residual slag and actual metal surface through subtle vibration pattern changes.
2Measurement precision
If a probe is swapped with the tool for measurement, then workpiece position can be determined, but the process becomes time-consuming
Solution Approach 1:
The patent merges the measurement function with the tool itself. The tool is equipped with vibration exciters and vibration sensors, eliminating the need for separate probe measurement operations. This integration allows the tool to perform both machining and measurement functions, removing the time-consuming tool swapping process.
Solution Approach 2:
The patent enables continuous measurement during the approach to the workpiece. The vibration-based measurement system operates continuously as the tool moves toward and contacts the workpiece, rather than requiring discrete probe measurement steps. This continuous measurement process eliminates idle time and maintains productive action throughout the operation.
3Measurement precision
If residual slag is present on the workpiece surface, then measurement errors occur, but the slag cannot be distinguished from the actual surface
Solution Approach 1:
The patent uses vibration analysis to detect subtle differences in mechanical properties between residual slag and actual metal surface. The vibration exciter generates vibrations that propagate differently through slag versus metal, and the vibration sensors detect these differences in vibration patterns, allowing discrimination between the two surface conditions.
Solution Approach 2:
The patent implements a feedback mechanism where vibration sensor data is continuously monitored and analyzed. The system compares vibration patterns against expected patterns for slag versus metal contact, providing real-time feedback that enables accurate discrimination between residual slag and actual workpiece surface, even when they appear similar visually.
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 solution enables faster and more accurate determination of workpiece position, reducing measurement errors and machining time by distinguishing between actual surface contact and residual slag, ensuring precise material removal and efficient machining processes.
Implementation Method 1
at least one position encoder disposed in a stationary manner with respect to the shaft, and a processing device. The position encoder is adapted to scan the measuring scale and generate position values from the measuring scale for indicating a position of the shaft
Data Source
AI summary
In a device and method for determining a contact between a tool and a workpiece, which are displaceable relative to each other, the tool or workpiece being rotationally fixedly connected to a shaft, the device includes a measuring arrangement including a measuring scale rotationally fixedly disposed on the shaft and at least one position encoder disposed in a stationary manner relative to the shaft, and a processing device. The position encoder is adapted to scan the measuring scale and to generate position values indicating a position of the shaft. The position values are fed to the processing device, which determines contact between the tool and the workpiece by evaluating a progression of the position values and signals the result of the evaluation by the status of a displacement signal.