Tool Spindle Bearing Layout for Thermal Stability and Precision

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Solution Overview

Problem

Existing tool spindles suffer from large deformations and increased weight due to the distance between the load application point and the fixed bearing section, compromising precision, especially in high-precision applications like centerless cylindrical grinding.

Innovation Solution

A tool spindle design with a bearing device having fixed bearing sections on both the tool interface and coupling section sides, utilizing materials with near-zero thermal expansion coefficients, reducing the distance between these sections and enhancing rigidity and precision.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Manufacturing precision

If the fixed bearing sections are provided on both sides of the drive device, then the spindle shaft is supported, but the distance between the load application point and the farther fixed bearing section is relatively large, leading to large deformations

Engineering Contradiction:

Improvespindle precisionVSAvoiddistance between bearing sections

Core Design Contradiction:

Manufacturing precisionVSLength of moving object

Solution Approach 1:

Instead of placing fixed bearing sections on both sides of the drive device as in conventional designs, this invention inverts the arrangement by positioning both fixed bearing sections on one side of the drive device. This inversion reduces the distance between the load application point and the farther bearing section, thereby minimizing deformations and improving spindle precision.

Inventive Principle:

Principle #13The other way round (Inversion)

Solution Approach 2:

The invention repositions the fixed bearing sections along the axial dimension of the spindle, concentrating them on one side rather than distributing them symmetrically. This dimensional reorganization reduces the effective span length, decreasing bending moments and deflections without compromising support adequacy.

Inventive Principle:

Principle #17Another dimension (Dimensionality change)

2Manufacturing precision

If the fixed bearing sections are provided on both sides of the drive device, then the spindle shaft is supported, but the tool spindle becomes relatively long overall, and thus the weight is relatively high

Engineering Contradiction:

Improvespindle precisionVSAvoidspindle weight

Core Design Contradiction:

Manufacturing precisionVSWeight of moving object

Solution Approach 1:

By inverting the conventional symmetric bearing arrangement and placing both fixed bearing sections on one side of the drive device, the overall axial length of the spindle is reduced. This length reduction directly decreases the spindle weight while maintaining adequate support for the spindle shaft, thus resolving the contradiction between precision and weight.

Inventive Principle:

Principle #13The other way round (Inversion)

3Manufacturing precision

If the distance between fixed bearing sections is reduced, then deformations are minimized, but the bearing device must absorb higher radial and axial loads

Engineering Contradiction:

Improvespindle precisionVSAvoidradial and axial loads on bearing device

Core Design Contradiction:

Manufacturing precisionVSForce

Solution Approach 1:

The invention changes the load distribution parameters by repositioning the bearing sections, which concentrates the load-absorbing function on a shorter span. The bearing device is designed to handle increased localized loads through parameter optimization, achieving both reduced deformations and adequate load capacity.

Inventive Principle:

Principle #35Parameter changes

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

The design minimizes deformations and weight, allowing for high-precision applications by reducing the length of the spindle and absorbing radial and axial loads effectively, particularly suitable for centerless grinding machines.

Implementation Method 1

a bearing device supporting the spindle shaft in the spindle housing, wherein the spindle shaft, and preferably the spindle housing, is made of a material having, at least in one direction, a thermal expansion coefficient in a range with a lower limit of [-10*10^-6 K^-1

Methodology Applied

Scientific EffectLoad bearing:

Implementation Method 2

the spindle shaft, and preferably the spindle housing, is made of a material having, at least in one direction, a thermal expansion coefficient in a range with a lower limit of [-10*10^-6 K^-1

Methodology Applied

Scientific EffectThermal expansion: Thermal Expansion

Data Source

PatentEP4606521A1Tool spindle and machine tool comprising a tool spindle

Publication Date: 2025.08.27 TSCHUDIN URS

Figure 1
Figure 2

AI summary

Tool spindle (1), comprising: a spindle shaft (3) which extends along a spindle axis (3a) and to which a tool can be coupled in a rotationally fixed manner at a tool interface (31); a spindle housing (2) which accommodates the spindle shaft (3); a drive device (4) which is coupled to a coupling section (33) of the spindle shaft (3) for rotational drive, a bearing device (4) which mounts the spindle shaft (3) in the spindle housing (2), wherein the spindle shaft (3), and preferably the spindle housing (2), is made of a material which has a thermal expansion coefficient of substantially zero in at least one direction.To ensure high precision requirements, the bearing device (4) has a first fixed bearing section (4a) on the tool interface side and a second fixed bearing section (4b) on the coupling section side, wherein the bearing device (4) is arranged along the spindle axis (3a) between the tool interface (31) and the coupling section (3) and supports the spindle shaft alone.