Machine Tool Thermal Compensation With Adaptive Measurement Timing
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Solution Overview
Problem
Existing thermal displacement compensation methods for machine tools face challenges in maintaining accuracy, particularly when environmental conditions change, due to overlearning issues that lead to increased errors in unlearned temperature environments, resulting in insufficient compensation.
Innovation Solution
A thermal displacement compensation apparatus and method that includes a temperature measuring unit, thermal displacement estimating unit, compensation unit, data recording unit, and a displacement measurement timing diagnostic unit, which compares past and current temperature information to determine when to measure displacement, optimizing the learning of the thermal displacement estimation formula and reducing measurement frequency in unchanged conditions.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If machine learning is performed using measured data to obtain a thermal displacement prediction formula, then the thermal displacement compensation is adjusted to the environment of using the machine tool, but overlearning occurs in which the error increases for unlearned data
Solution Approach 1:
The system performs preliminary learning using measured data groups before actual machining operations. A learning execution unit accumulates temperature-displacement data pairs and performs offline learning to create a prediction formula. This preliminary action ensures the system adapts to the specific machine tool environment while having sufficient unlearned data for validation, preventing overlearning.
Solution Approach 2:
The system uses feedback from measured displacement data to validate and refine the thermal displacement prediction formula. The learning execution unit compares predicted displacement with actual measured displacement, using this feedback to adjust the prediction model. This feedback mechanism ensures the model generalizes well to unlearned scenarios while adapting to the specific environment.
2Measurement precision
If displacement measurement is performed frequently to improve learning accuracy, then the thermal displacement compensation accuracy is improved, but the measurement time and system complexity increase
Solution Approach 1:
The system performs displacement measurements periodically at predetermined time intervals rather than continuously. The measurement execution unit is triggered at specific intervals to collect temperature-displacement data pairs for learning. This periodic measurement approach provides sufficient data for accurate thermal displacement prediction while significantly reducing measurement time and system complexity compared to continuous measurement.
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 approach improves the accuracy of thermal displacement compensation by effectively learning the relation between temperature and displacement, minimizing errors in unlearned environments and reducing unnecessary displacement measurements, thus enhancing machining precision.
Implementation Method 1
thermal distortion of each unit in the machine tool is caused by the influence of heat generation in machine by a main spindle and a feed axis operation
Data Source
AI summary
A thermal displacement compensation apparatus includes a temperature measuring unit, a thermal displacement estimating unit, a thermal displacement compensation unit, a displacement measuring unit, a data recording unit, a thermal displacement compensation learning unit, and a displacement measurement timing diagnostic unit. The displacement measuring unit measures a displacement of a machine tool after compensating an axis command value. The thermal displacement compensation learning unit determines a thermal displacement estimation formula based on temperature information and the displacement recorded in the data recording unit. The displacement measurement timing diagnostic unit compares the temperature information at a past displacement measurement recorded in the data recording unit with current temperature information obtained from the temperature measuring unit, and determines whether to measure the displacement by the displacement measuring unit or not at a predetermined diagnosis timing.