Low-Expansion Tool Spindle Layout for Precision Grinding

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Solution Overview

Problem

Existing tool spindles suffer from large deformations and increased weight due to a significant distance between the load application point and fixed bearing sections, which affects precision and are unsuitable for high-precision applications like centerless cylindrical grinding.

Innovation Solution

A tool spindle design with fixed bearing sections arranged on one side of the coupling section, utilizing materials with a low heat expansion coefficient, such as CFRP, and a compact bearing arrangement to reduce deformation and weight, enhancing precision and stiffness.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Manufacturing precision

If fixed bearing sections are provided on both sides of the drive device, then the spindle shaft is well-supported, but the distance between load application point and fixed bearing section becomes large causing deformations

Engineering Contradiction:

Improvespindle precisionVSAvoiddistance between bearing sections

Core Design Contradiction:

Manufacturing precisionVSLength of moving object

Solution Approach 1:

The bearing device is repositioned from a symmetric arrangement on both sides of the drive device to an asymmetric arrangement where both fixed bearing sections are located on one side of the coupling section. This dimensional repositioning reduces the distance between the load application point at the tool interface and the nearest fixed bearing section, minimizing deformations while maintaining support stability.

Inventive Principle:

Principle #17Another dimension (Dimensionality change)

2Reliability

If fixed bearing sections are arranged on both sides of drive device, then support is provided, but tool spindle length and weight increase

Engineering Contradiction:

Improvesupport stabilityVSAvoidspindle weight

Core Design Contradiction:

ReliabilityVSWeight of moving object

Solution Approach 1:

One of the fixed bearing sections that would traditionally be placed on the opposite side of the drive device is extracted from that position and relocated to the same side as the other bearing section. This extraction and relocation reduces the overall length and weight of the spindle while the remaining two bearing sections on one side continue to provide adequate support stability.

Inventive Principle:

Principle #2Taking out (Extraction)

3Manufacturing precision

If bearing distance is reduced, then precision is improved, but load-bearing capacity may be affected

Engineering Contradiction:

Improveabsolute deformationsVSAvoidload-bearing capacity

Core Design Contradiction:

Manufacturing precisionVSStrength

Solution Approach 1:

The spindle shaft is constructed from carbon fiber reinforced plastic (CFRP), a composite material that provides high stiffness and strength-to-weight ratio. This allows the bearing distance to be reduced for improved precision while the CFRP material maintains adequate load-bearing capacity despite the shorter support span.

Inventive Principle:

Principle #40Composite materials

4Manufacturing precision

If material with low heat expansion coefficient is used, then thermal deformation is reduced, but material selection becomes constrained

Engineering Contradiction:

Improvethermal stabilityVSAvoidmaterial selection freedom

Core Design Contradiction:

Manufacturing precisionVSAdaptability or versatility

Solution Approach 1:

Carbon fiber reinforced plastic (CFRP) is selected as the material for the spindle shaft and housing. CFRP provides a heat expansion coefficient close to zero, ensuring thermal stability and minimal thermal deformation. While material selection is constrained, the chosen composite material satisfies both the precision requirements and can be manufactured using conventional composite fabrication processes.

Inventive Principle:

Principle #40Composite materials

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 achieves high precision and compactness, suitable for high-precision applications by minimizing deformations and weight, allowing for efficient handling of radial and axial loads while maintaining precise tool guidance.

Implementation Method 1

the spindle shaft, and preferably the spindle housing, is made of a material, which has, at least in one direction, a heat expansion coefficient in a range with a lower limit of [-10×10^-6/K, -5×10^-6/K and -2×10^-6/K] and an upper limit of [+2×10^-6/K, +5×10^-6/K and +10×10^-6/K], in particular essentially zero

Methodology Applied

Scientific EffectThermal expansion: Thermal Expansion

Data Source

PatentUS20250269491A1Tool spindle and machine tool comprising a tool spindle

Publication Date: 2025.08.28 TSCHUDIN URS

AI summary

A 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 receives the spindle shaft (3); a drive device (4), which is coupled to a coupling section (33) of the spindle shaft (3) for rotationally driving, a bearing device (4), which supports 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, at least in one direction, a heat expansion coefficient of essentially zero. To ensure high precision requirements, the bearing device (4) has a first tool interface-side fixed bearing section (4a) and a second coupling section-side fixed bearing section (4b), wherein the bearing device (4) is arranged along the spindle axis (3a) between tool interface (31) and coupling section (3) and supports the spindle shaft exclusively.