Coordinate Gantry Measuring Machine Statically Determinate Constraints
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Solution Overview
Problem
Gantry machines face limitations in measurement precision due to their large dimensions and dimensional instability of the foundation, leading to deformations and relative displacements that result in measurement errors, which are difficult to compensate.
Innovation Solution
A gantry machine design featuring a statically determinate constraint system between the pillars and longitudinal members, where the pillars are connected at specific points to minimize deflection and cross members are used to form a rigid frame that uncouples deformations from pillar movements, allowing for easy compensation of roto-translations.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Stability of the object's composition
If the longitudinal members are constrained to the pillars, then the machine structure is stable, but deformations are generated on the longitudinal members leading to measurement errors
Solution Approach 1:
The constraint system is segmented into multiple independent constraints distributed at different locations (ends and middle of longitudinal members). This segmentation allows the system to accommodate pillar deformations locally while maintaining overall frame stability, preventing the transmission of deformations to the longitudinal members.
Solution Approach 2:
The constraint mechanisms act as intermediaries between the pillars and the longitudinal members. These constraints allow relative movement and rotation, decoupling the deformations of the pillars from the longitudinal members while maintaining structural connectivity and stability.
2Length of stationary object
If the machine dimensions are increased to measure large objects, then the measuring range is improved, but the machining tolerances and foundation stability deteriorate
Solution Approach 1:
The large-scale frame is segmented into multiple components (longitudinal members, cross members, pillars) connected through flexible constraints. This segmentation allows each component to be manufactured with standard tolerances while the overall structure achieves high precision through the decoupling of deformations.
Solution Approach 2:
The constraint system changes the mechanical parameters of the connection between pillars and longitudinal members, allowing rotation and relative movement. This parameter change enables the structure to accommodate foundation instabilities and machining tolerances while maintaining measurement precision.
3Strength
If the pillars are constrained rigidly to the longitudinal members, then the structural rigidity is improved, but the measurement errors due to foundation instability increase
Solution Approach 1:
The constraint system introduces dynamic flexibility to the connection between pillars and longitudinal members. The constraints allow rotation and relative movement, enabling the structure to adapt to foundation instabilities while maintaining sufficient rigidity for measurement through the overall frame geometry and cross member support.
Data Source
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AI summary
A co-ordinate gantry measuring machine (1), having a fixed structure (2) comprising three pillars (3, 4 , 5) designed to be fixed to a foundation or to a machine bed, a pair of horizontal longitudinal members (7, 8) parallel to one another, supported by the pillars (3, 4, 5) and provided with guides (15, 16), and a mobile unit comprising a carriage (17) supported by the longitudinal members (7, 8) and mobile along the guides (15, 16); the longitudinal members (7, 8) are connected together by a pair of cross members (9, 10) to form a frame (6) supported by the pillars (3, 4, 5) via a statically determinate system of constraints (25, 26, 27).