Machine Tool Thermal Displacement Correction via Dual Position Measurement

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Solution Overview

Problem

Machine tools face challenges in maintaining processing accuracy due to thermal expansion and deformation, which existing cooling devices fail to adequately address, leading to errors in spindle axis and tool post positioning.

Innovation Solution

A machine tool design incorporating spindle and tool side position measuring units with fixed reference positions allows for accurate measurement and correction of the distance between the spindle axis and the cutter edge, accounting for thermal displacement by using a calculating block to determine relative positions and perform necessary corrections.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Temperature

If a cooling device is used to suppress thermal expansion, then thermal deformation is reduced, but the device becomes too huge and bulky

Engineering Contradiction:

Improvethermal expansion suppressionVSAvoidcooling device size

Core Design Contradiction:

TemperatureVSVolume of moving object

Solution Approach 1:

The patent replaces the mechanical cooling device with a measurement and correction system. Instead of physically cooling the components to prevent thermal expansion, the invention measures the actual thermal displacement using scales and readout units, then corrects the tool position electronically based on these measurements, eliminating the need for bulky cooling equipment.

Inventive Principle:

Principle #28Mechanics substitution (Replace mechanical system)

Solution Approach 2:

The patent introduces scales and readout units as intermediary measurement devices between the mechanical components. These intermediaries enable indirect measurement of thermal displacement without requiring direct physical intervention or cooling of the components, allowing for precise measurement and correction of thermal effects.

Inventive Principle:

Principle #24Intermediary (Mediator)

2Measurement precision

If only relative position of tailstock to headstock is measured, then thermal displacement correction is possible, but error occurs when tool post thermal displacement occurs

Engineering Contradiction:

Improvethermal displacement correctionVSAvoidspindle axis to tool distance accuracy

Core Design Contradiction:

Measurement precisionVSManufacturing precision

Solution Approach 1:

The patent divides the measurement system into two independent segments: one measuring the position of the headstock (or tailstock) relative to the machine bed, and another measuring the position of the tool post relative to the machine bed. This segmentation allows each measurement to be independent and accurate, and the corrections can be combined to achieve precise tool positioning even when thermal displacement occurs in different components.

Inventive Principle:

Principle #1Segmentation

Solution Approach 2:

The patent implements a feedback mechanism where the measured positions from both the headstock/tailstock and tool post are continuously monitored, and the tool position is corrected based on these feedback measurements. This ensures that any thermal displacement in either component is detected and compensated for in real-time.

Inventive Principle:

Principle #23Feedback

3Ease of operation

If headstock and tailstock are arranged with fixed positional relationship, then scale readout is possible, but the system cannot adapt when headstock or tool post moves in spindle axial direction

Engineering Contradiction:

Improvescale readout capabilityVSAvoidmovement flexibility

Core Design Contradiction:

Ease of operationVSAdaptability or versatility

Solution Approach 1:

The patent transitions from a static measurement system to a dynamic one. Instead of relying on a fixed positional relationship between headstock and tailstock, the system uses independent measurement of each component's position relative to the machine bed, allowing either component to move freely in the spindle axial direction while maintaining accurate measurement and correction capabilities.

Inventive Principle:

Principle #15Dynamics

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 ensures precise measurement and correction of thermal displacement effects, enhancing processing accuracy and machine precision by accurately determining the relative distance between the spindle axis and the cutter edge, thereby improving overall machine tool performance.

Implementation Method 1

thermal expansion and/or thermal deformation tend to occur at a machine bed and various parts of the machine tool because of a cutting heat and/or heat emission

Methodology Applied

Scientific EffectThermal expansion: Thermal Expansion

Data Source

PatentUS8631727B2Machine tool

Publication Date: 2014.01.21 MURATA MASCH LTD

AI summary

A machine tool includes a spindle side position measuring unit measuring a spindle axial position in a spindle radial direction relative to a first reference position and a tool side position measuring unit measuring the position of a tool post relative to a second reference position. The spindle side position measuring unit includes a first scale extending in the spindle radial direction and a first readout unit, one of a base end portion of the first scale and the first readout unit is disposed at a spindle axis and the other of the base end portion of the first scale and the first readout unit is disposed at the first reference position. One of a base end portion of a second scale and a second readout unit is disposed on the tool post and the other is disposed at the second reference position.