Thermal Displacement Correction Using Machine-Dependent Coefficients
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Solution Overview
Problem
Conventional thermal displacement correction methods in machine tools require frequent and burdensome measurements to adjust for deviations between calculated and actual thermal displacement amounts, leading to suspended machining cycles and limited adaptability to changing environments.
Innovation Solution
A thermal displacement correction apparatus that calculates an adjustment value using a machine-dependent and machining condition-dependent coefficient, allowing for real-time adjustment of the thermal displacement correction amount based on an approximate expression derived from machining experiment data, reducing the need for repeated measurements and minimizing cycle suspension.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If frequent measurements are performed to adjust thermal displacement correction amount, then correction precision is improved, but machining cycle is suspended and productivity decreases
Solution Approach 1:
The system performs preliminary measurement and calculation of machine-dependent and machining condition-dependent coefficients before actual machining. These pre-calculated coefficients are stored and automatically applied during machining, eliminating the need for frequent measurements during production and maintaining continuous machining cycles while ensuring correction precision.
Solution Approach 2:
The system establishes a feedback mechanism where measurement results from initial experiments are used to calculate correction coefficients, which are then applied during machining. The system continuously monitors machining conditions and adjusts correction amounts based on pre-established relationships between machining parameters and thermal displacement, maintaining precision without interrupting production.
2Measurement precision
If manual measurement and adjustment is performed to match thermal displacement correction amount with actual displacement, then correction accuracy is improved, but operation complexity and time consumption increase
Solution Approach 1:
The system performs self-adjustment by automatically calculating correction amounts based on pre-stored coefficients and current machining conditions. The numerical controller automatically applies the machine-dependent and machining condition-dependent coefficients to compute the appropriate thermal displacement correction without requiring manual measurement or adjustment operations, improving both accuracy and ease of operation.
Solution Approach 2:
The system changes the approach from manual parameter adjustment to automatic parameter calculation. By establishing mathematical relationships between machining parameters (speed, feed rate, depth of cut) and thermal displacement through initial experiments, the system automatically determines correction amounts based on these parameter changes during machining, eliminating manual intervention while maintaining high accuracy.
3Ease of operation
If constant adjustment value is used after initial setting, then operation simplicity is maintained, but adaptability to changing machining environments deteriorates
Solution Approach 1:
The system transitions from static constant adjustment values to dynamic correction amounts that automatically adapt to changing machining conditions. By establishing relationships between machining parameters and thermal displacement through initial experiments, the system dynamically calculates appropriate correction amounts based on actual machining conditions (speed, feed rate, depth of cut), maintaining both operational simplicity and environmental adaptability.
Solution Approach 2:
The system performs preliminary experimentation to establish the relationship between machining conditions and thermal displacement before actual production. The machine-dependent and machining condition-dependent coefficients obtained from these preliminary studies are stored and automatically applied, enabling the system to adapt to different machining environments without requiring manual re-adjustment while maintaining operational simplicity.
4Measurement precision
If multiple measurements are performed to change adjustment value, then correction precision is improved, but measurement time and cycle suspension frequency increase
Solution Approach 1:
The system performs comprehensive measurement and coefficient calculation in advance during machine setup and initial experimentation phases. The machine-dependent and machining condition-dependent coefficients are determined through preliminary tests covering various machining conditions. During actual production, these pre-established coefficients are automatically applied, eliminating the need for repeated measurements and significantly reducing time loss while maintaining high correction precision.
Solution Approach 2:
The system establishes a feedback loop where initial measurement results are used to calculate correction coefficients, which are then applied during machining. This single-phase measurement approach, combined with automatic calculation based on machining parameters, achieves high precision without requiring multiple measurement iterations during production, thereby minimizing time loss and cycle suspensions.
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
Enables precise and timely adjustment of thermal displacement correction amounts in machine tools, reducing measurement frequencies and maintaining accuracy without suspending machining cycles, even in varying environments.
Implementation Method 1
the main spindle and the feed screws expand to cause their displacements in machine positions due to heat generated from the motors, frictional heat caused by rotation of bearings, and frictional heat in engagement parts of ball screws and ball nuts of the feed screws
Data Source
AI summary
A thermal displacement correction apparatus for a machine tool first determines the coefficient k in E=a+k|F| where F is a thermal displacement correction amount and E is an adjustment value (first step). Next, in actual processing, a is set if a has not been set yet (second step). After a and the coefficient k are determined in advance, thermal displacement correction unit is enabled and an operation of a machining program is started. The thermal displacement correction amount F is calculated, the adjustment value E is calculated based on E=a+k|F|, a thermal displacement correction amount F′ after adjustment (=E×F) is calculated, and F′ is sent to the thermal displacement correction unit.