Machine Tool Spindle Temperature Control for Accurate Probe Fetching
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Solution Overview
Problem
The challenge in machine tool operations is the thermal expansion and deformation of spindle shafts due to heat generated during machining, which affects the accuracy of geometrical probes when quickly mounted after spindle rotation, leading to potential errors in workpiece referencing, and existing solutions either result in costly downtime or imprecise thermal modeling.
Innovation Solution
A method that determines the optimal time to fetch a geometrical probe by measuring spindle temperature parameters, such as temperature values and their derivatives, to ensure thermal equilibrium, thereby avoiding unnecessary downtime and ensuring precise probe usage without requiring extensive calibration or thermal modeling.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If a long waiting time is implemented before fetching the geometrical probe, then thermal equilibrium is achieved and measurement precision is improved, but productivity deteriorates due to unnecessary downtime
Solution Approach 1:
The waiting time before probe fetching is made dynamic rather than static. The control device determines the optimal waiting time based on real-time temperature measurements from the spindle, allowing the system to adapt the waiting period to actual thermal conditions. This resolves the contradiction by implementing a dynamic waiting time that is long enough to ensure thermal equilibrium (improving measurement precision) but not excessively long (maintaining productivity).
Solution Approach 2:
A feedback mechanism is implemented where temperature sensors continuously monitor the spindle temperature, and this information is fed back to the control device. The control device uses this feedback to determine when thermal equilibrium has been reached and when it is safe to fetch the probe. This feedback loop ensures measurement precision is maintained while avoiding unnecessary waiting time that would reduce productivity.
2Measurement precision
If a conservative waiting time is defined for all practical purposes, then measurement precision is ensured, but productivity deteriorates due to excessive downtime
Solution Approach 1:
The waiting time parameter is changed from a fixed conservative value to a variable value determined by actual temperature measurements. The control device calculates the optimal waiting time based on the measured temperature difference between the spindle and the probe, allowing the system to use shorter waiting times when thermal conditions permit, thus reducing time loss while maintaining measurement precision.
Solution Approach 2:
The system performs self-service by automatically monitoring its own thermal state through temperature sensors and making autonomous decisions about when to allow probe fetching. This eliminates the need for manual intervention or overly conservative fixed waiting times, optimizing both measurement precision and time efficiency.
3Measurement precision
If thermal modelling is implemented to determine probe fetching time, then measurement precision may be improved, but device complexity increases and results become imprecise
Solution Approach 1:
The complex thermal modelling process is extracted and replaced with direct temperature measurement using sensors. Instead of implementing complex mathematical models to predict thermal behavior, the system directly measures the actual temperature of the spindle and uses this real data to determine the optimal probe fetching time. This extraction of the modelling step simplifies the device while maintaining or improving measurement precision.
Solution Approach 2:
The theoretical thermal modelling approach is replaced with a practical sensor-based measurement system. Rather than using complex computational models to estimate thermal conditions, the system substitutes this with direct physical measurement of temperature, providing accurate real-time data without the complexity and imprecision of modelling.
4Productivity
If the geometrical probe is fetched immediately after spindle rotation, then productivity is improved by reducing downtime, but measurement precision deteriorates due to thermal effects
Solution Approach 1:
The system performs preliminary temperature measurement and evaluation before allowing the probe to be fetched. The control device monitors the spindle temperature in advance and determines the optimal moment to permit probe fetching based on thermal conditions. This preliminary action ensures that the probe is only fetched when thermal equilibrium is sufficient, maintaining measurement precision while minimizing the waiting time that would affect productivity.
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 allows for accurate and reproducible determination of the probe-fetching time based on actual spindle temperature, reducing downtime and ensuring precise measurements by ensuring thermal stability, regardless of previous spindle activity or calibration conditions.
Implementation Method 1
at least one temperature sensor (11) arranged and configured to measure a spindle temperature value
Implementation Method 2
heat generated by spindle bearings and/or a spindle motor is spread to a spindle shaft as well as to the rest of the machine tool connected to the spindle
Implementation Method 3
This heat transfer generates mainly an expansion of the spindle shaft length as well as a deformation of the machine structure
Implementation Method 4
the temperature difference between the warm spindle shaft and the geometrical probe generates heat transfer
Data Source
Figure 1~2
Figure 3a~3c
AI summary
The invention is related to a method for using a geometrical probe (5) with a spindle (3) of a machine tool (1), wherein - in a probe fetch waiting state of the machine tool (1), at least one temperature parameter related to a temperature of the spindle (3) of the machine tool (1) is determined by measuring at least one temperature value for the spindle (3), and - a time for fetching the geometrical probe (5) is determined depending on the at least one temperature parameter.