Spindle Tool Path Compensation for Thermal Elongation in Machining
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Solution Overview
Problem
High-precision machining tools face inaccuracies due to thermal and rotational speed-induced elongations and displacements of the shank and tool holder, leading to undesirable waiting times for thermal equilibrium before machining can commence.
Innovation Solution
A machining tool equipped with a control unit that continuously compensates for thermal and rotational speed-related displacements using a distance sensor and temperature sensors, allowing immediate machining without warm-up periods by adjusting the tool path based on real-time data from distance and rotational speed measurements.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If the main spindle and tool holder are allowed to reach thermal equilibrium before machining, then machining precision is improved, but machining time increases due to required warm-up waiting times
Solution Approach 1:
The patent applies preliminary action by measuring the tool length immediately after clamping the tool holder to the shank, before thermal equilibrium is reached. The system then compensates for thermal expansion during machining by continuously monitoring temperature and adjusting the tool path, eliminating the need to wait for warm-up while maintaining precision.
Solution Approach 2:
The patent implements feedback by continuously measuring the temperature of the shank and tool holder during machining operations. The control unit uses this temperature data to calculate thermal expansion and dynamically adjust the tool path in real-time, allowing precision machining to proceed without warm-up waiting time.
2Loss of time
If the cutting tool length is measured immediately after clamping to the shank, then machining time is reduced, but machining precision deteriorates due to thermal and speed-induced displacements during machining
Solution Approach 1:
The control unit continuously receives temperature data from sensors during machining and uses this feedback to calculate real-time thermal expansion of the shank and tool holder. The system dynamically adjusts the tool path based on these measurements, maintaining machining precision despite measuring the tool length before thermal equilibrium.
Solution Approach 2:
The patent changes the parameter being monitored from static tool length to dynamic thermal expansion. By measuring temperature and calculating expansion based on temperature changes, the system adapts to thermal conditions during machining, allowing early tool length measurement without precision loss.
3Speed
If the shank is supported by ball bearings to enable high-speed rotation, then rotational speed is improved, but thermal expansion and displacement increase due to friction heating
Solution Approach 1:
Temperature sensors mounted on the shank provide continuous feedback about thermal conditions during high-speed rotation. The control unit uses this data to calculate thermal expansion and adjust the tool path accordingly, maintaining axial displacement accuracy despite friction heating from ball bearings enabling high rotational speeds.
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 high-precision machining without the need for warm-up times, ensuring accurate tool path compensation and reducing machining inaccuracies by continuously adapting to thermal and speed-induced elongations and displacements.
Implementation Method 1
the shank thermally expands in the longitudinal direction and the rotating tool holder with cutting tool clamped thereto is displaced in the longitudinal direction
Implementation Method 2
The distance sensor is preferably a highly accurate distance sensor and especially a distance sensor for contactless measurement, e.g. an eddy-current sensor
Data Source
AI summary
The invention relates to a machining tool for machining a workpiece, including a main spindle with a driven shank, a tool holder which can be clamped in the shank, a cutting tool which is arranged on the tool holder, a distance sensor for determining a distance of the shank of the main spindle in relation to a reference point, and a control unit which is configured to perform compensation of the tool path during machining of the workpiece based on an elongation and displacement of the shank and an elongation of the tool holder holding the cutting tool, wherein the elongation and displacement of the shank is determined based on the distance determined using the distance sensor, and wherein the elongation of the tool holder holding the cutting tool is determined based on a rotational speed of the shank.