CNC Positioning Accuracy via Liquid Level Reference
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Solution Overview
Problem
Conventional methods for determining positioning accuracy in CNC machines, especially large ones, are inadequate due to limitations in measuring displacement errors, as they often fail to provide reliable position determination at varying positions on the machine tool head.
Innovation Solution
A method and system using a system of communicating vessels filled with liquid, where a distance sensor or electrode is used to determine the z-coordinate by measuring the distance or electrical potential difference between the machine tool head and the liquid surface, allowing for accurate positioning error calculation across different machine geometries and sizes.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If laser trackers or interferometer telescoping ball bars are used to measure positioning errors, then measurement capability is provided, but reliable position determination cannot be made for large machines at different positions due to excessive distance from laser source
Solution Approach 1:
The patent introduces a liquid level system as an intermediary reference that spans the entire machine table. The liquid surface acts as a continuous reference plane that can be measured at any position across the machine, eliminating the need for direct line-of-sight to a distant laser source. This mediator enables accurate positioning measurement throughout the large machine workspace.
Solution Approach 2:
The patent transitions from measuring in the horizontal plane (x-y coordinates) to using a vertical reference (z-coordinate via liquid level). By establishing a reference system based on the vertical liquid surface height, the measurement approach changes dimensions, allowing position determination across large horizontal distances through vertical level measurement.
2Reliability
If conventional measurement methods are used, then some positioning errors can be detected, but they fail to provide accurate measurements across the entire machine table for large machines
Solution Approach 1:
The patent divides the large machine table area into multiple measurement zones by placing several vessels at different locations. Each vessel provides a local reference point, and by combining measurements from multiple segmented locations, the system achieves comprehensive coverage of the entire large machine table area with reliable measurements throughout.
3Manufacturing precision
If a distance sensor is used to measure z-coordinate, then positioning accuracy in z-direction can be determined, but the method must be adapted for different machine geometries and sizes
Solution Approach 1:
The patent creates a universal measurement system where the liquid level reference can be applied to any machine geometry or size. The vessels are placed on the machine table surface, and the liquid surface provides a common reference plane that works regardless of the specific machine configuration, making the system adaptable and versatile across different CNC machine types.
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
Enables precise determination of positioning accuracy in the z-direction for various machine geometries and sizes, allowing for effective compensation of positioning errors, thereby improving the overall accuracy and reliability of CNC machines.
Implementation Method 1
a distance sensor is mounted to the machine tool head... approaching the surface of the liquid with the distance sensor
Implementation Method 2
arranging a plurality of vessels on the machine table, wherein the vessels are in fluid connection with each other to form a system of communicating vessels
Data Source
AI summary
A method for checking positioning accuracy of a CNC machine with a machine tool head and a machine table using an x, y, z coordinate system, the method comprising:a) arranging a plurality of vessels on the table, the vessels in fluid connection with each other to form a system of vessels, the vessels filled with a liquid,b) mounting a distance sensor to the tool head,c) positioning the tool head to a position above the surface of the liquid in one of the vessels,d) a determining the z coordinate for which the distance sensor touches the surface of the liquid,or,for a predetermined position of the tool head in z direction above the liquid, determining the distance between the distance sensor and the liquid;steps c) and d) are repeated for each vessel to determine a z coordinate of the surface of the liquid.