Optical Scale Assembly With Selectable Zero-Expansion Reference
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Existing optical scales do not allow the scale-grating and scale-holder to thermally expand independently and consistently with the machine, leading to inaccuracies and misalignments due to differing thermal expansion coefficients of materials, especially in varying temperatures.
Innovation Solution
The optical scale features a system where the scale-grating and scale-holder can be fixed with free longitudinal slipping positions, allowing them to expand independently without interference, with easily selectable FEP points that do not require preventive drilling or alignment, using elastic-thrust screw clamping and pressure pins to maintain stability and alignment.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If the scale-holder is made of aluminium to protect the scale-grating, then the protective function is improved, but thermal expansion differences cause misalignments and measuring errors
Solution Approach 1:
The scale system is divided into independent segments: the scale-grating support and the scale-holder are separated and can move independently relative to each other. This segmentation allows each component to expand or contract according to its own material properties without constraining the other, thereby maintaining measurement precision while preserving the protective function of the aluminium scale-holder.
Solution Approach 2:
Free longitudinal slipping means act as an intermediary mechanism between the scale-grating support and the scale-holder. These slipping means allow relative movement in the longitudinal direction, accommodating thermal expansion differences between the steel/glass scale-grating support and the aluminium scale-holder, thus preventing misalignment while maintaining protection.
2Stability of the object's composition
If the scale-grating and scale-holder are rigidly fixed together, then alignment stability is improved, but thermal expansion constraints cause distortions and measuring errors
Solution Approach 1:
The connection between the scale-grating support and scale-holder transitions from a static rigid fixation to a dynamic system with controlled relative movement. The free longitudinal slipping means enable the system to adapt dynamically to thermal expansion changes, allowing each component to maintain its dimensional stability independently while preserving overall alignment through the slipping mechanism.
3Ease of manufacture
If the FEP position is fixed during manufacturing, then production simplicity is improved, but adaptability to different machine configurations is reduced
Solution Approach 1:
The scale system incorporates multiple selectable FEP positions along the scale-grating, making it a universal solution that can adapt to different machine configurations and applications. The scale-holder can be positioned at various locations relative to the scale-grating support, each position serving as a potential FEP, thus providing multi-functionality without complicating the manufacturing process.
Solution Approach 2:
Multiple FEP positions are pre-configured on the scale-grating during manufacturing, allowing the system to be adapted to different machine configurations simply by selecting and positioning the scale-holder at the appropriate location. This preliminary preparation of multiple positions enables versatility while maintaining production simplicity.
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 measurements by allowing thermal expansion to occur freely and consistently with the machine, reducing distortions and misalignments, thereby improving machining accuracy across varying temperatures.
Implementation Method 1
all materials expand as a function of their coefficient of linear thermal expansion λ and their temperature
Implementation Method 2
elastic-thrust screw clamping fasteners
Data Source
Figure 1
Figure 2A~2B
Figure 3
AI summary
An optical or magnetic scale for taking linear measurements comprises a scale-holder (P) integral with a fixed or moving part of a machine, and a scale-grating support (2, 2v) housed inside said scale-holder (P) and scanned by a transducer (T), wherein the transducer (T) slides along the scale-holder (P) and is integral with a moving or fixed element of said machine. The scale-holder (P) and the scale-grating support (2, 2v) are respectively fixed to the machine and the scale-holder (P) at a single fixed position forming their respective FEP, and said FEPs are independently selectable from several predefined positions (6, 9). The scale-holder (P) and the scale grating support (2, 2v) are furthermore fastened to the machine and to the scale-holder (P), respectively, at one or more additional free longitudinal slipping positions.