Encoder Scale Mounting Structure for Thermal Expansion Relief
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Solution Overview
Problem
Existing metrological scales experience inaccuracies due to thermal expansion mismatches between the scale and the substrate, leading to unpredictable and undesired changes in effective thermal expansion coefficients, which affect measurement precision.
Innovation Solution
A scale arrangement with a thermal displacement relief structure comprising an intermediate member and adhesive layers with controlled thermal expansion coefficients, allowing the scale to expand and contract independently of the substrate, reducing the influence of substrate thermal expansion.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If the scale is directly mounted to the substrate, then the mounting is simple, but the thermal expansion mismatch causes measurement inaccuracies
Solution Approach 1:
An intermediate member is introduced between the scale and substrate. This intermediate member has thermal expansion properties that bridge the gap between the scale and substrate, allowing the scale to maintain its inherent thermal expansion characteristics while still being mounted to the substrate. The intermediate member effectively mediates the thermal expansion mismatch, preventing measurement inaccuracies without complicating the mounting process.
2Strength
If the scale is mastered to the substrate, then the mounting is secure, but the scale's thermal expansion is dictated by the substrate causing inaccuracies
Solution Approach 1:
The intermediate member serves as a mediator that decouples the thermal expansion relationship between the scale and substrate. It provides a secure mechanical connection while allowing the scale to expand and contract according to its own thermal properties rather than being forced to follow the substrate's expansion pattern, thus maintaining measurement precision while ensuring secure mounting.
Solution Approach 2:
The mounting structure is segmented into three distinct components: the substrate, the intermediate member, and the scale. This segmentation allows each component to have optimized properties - the substrate provides structural support, the intermediate member manages thermal expansion differences, and the scale maintains measurement accuracy. The segmentation breaks the direct thermal coupling that would otherwise force the scale to follow substrate expansion.
3Adaptability or versatility
If adhesive layers are used to attach the scale, then the mounting is flexible, but thermal expansion differences cause stress and potential damage
Solution Approach 1:
The intermediate member acts as a buffer that reduces the stress transmitted through the adhesive layers. By absorbing and distributing the thermal expansion differences, the intermediate member prevents excessive stress concentration at the adhesive interfaces, thereby maintaining attachment integrity while preserving the flexibility benefits of adhesive mounting.
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 solution significantly reduces the deviation of the scale's effective thermal expansion coefficient from its inherent value, improving measurement accuracy by minimizing the impact of substrate thermal expansion.
Implementation Method 1
a first adhesive layer for attaching the scale to the intermediate member
Implementation Method 2
the coefficients of thermal expansion of the intermediate member and of the scale conform to: −2×10−6 K−1≤CTE(intermediate member)−CTE(scale)≤2×10−6 K−1
Data Source
AI summary
A scale arrangement for a measurement encoder includes a scale and a thermal displacement relief structure. The thermal displacement relief structure includes an intermediate member and a first thermal displacement relief layer for attaching the scale to the intermediate member. The coefficients of thermal expansion of the intermediate member and the scale conform to the following:-3×10-6 K-1≤CTE(intermediate member)-CTE(scale)≤6×10-6 K-1.