Coordinate Positioning Machine With Removable Metrology Zones
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Solution Overview
Problem
Articulated robots face challenges in achieving high accuracy and repeatability due to cumulative positional errors from their serial mechanical linkages, making them less suitable for demanding applications despite their versatility and reach.
Innovation Solution
A manufacturing system that combines a coordinate positioning machine with a metrology arrangement, allowing the machine to switch between lower-accuracy and higher-accuracy zones within its working volume, using a hexapod metrology arrangement to provide precise position measurements when coupled, thereby enhancing accuracy and repeatability.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If an articulated robot with multiple rotary joints is used to achieve versatility and large reach, then the robot can perform a wide variety of manufacturing operations with high flexibility, but cumulative positional errors from the serial mechanical linkages reduce accuracy and repeatability
Solution Approach 1:
The system divides the working volume into multiple zones based on accuracy requirements. High-accuracy zones utilize the metrology arrangement for precise operations, while other zones operate with the robot's standard positioning system. This segmentation allows the robot to maintain versatility across the entire workspace while achieving high accuracy only where needed, resolving the contradiction between flexibility and precision.
Solution Approach 2:
A removable metrology arrangement acts as an intermediary between the robot and the workpiece in high-accuracy zones. This intermediate measurement system compensates for the robot's cumulative positioning errors by providing independent, high-precision position feedback, enabling accurate operations without compromising the robot's overall versatility.
2Manufacturing precision
If a metrology arrangement is permanently coupled to the robot to improve accuracy, then high-precision measurements can be obtained throughout the working volume, but the system complexity and cost increase significantly
Solution Approach 1:
The metrology arrangement is designed to be dynamically configurable rather than permanently fixed. It can be removably coupled to the robot when high accuracy is needed and decoupled when not required. This dynamic approach allows the system to adapt its complexity level based on task requirements, maintaining simplicity for routine operations while enabling high precision when necessary.
Solution Approach 2:
High accuracy is provided locally in specific zones where it is actually needed, rather than uniformly across the entire working volume. The metrology arrangement is deployed only in high-accuracy zones, allowing the system to achieve precision where required while maintaining overall system simplicity and avoiding unnecessary complexity in areas where standard accuracy suffices.
3Manufacturing precision
If calibration is performed to reduce positional errors, then the robot's positioning accuracy improves, but calibration of non-Cartesian machines with multiple rotary joints is a significant challenge requiring complex procedures
Solution Approach 1:
The system replaces complex mechanical calibration procedures with a metrology-based measurement approach. Instead of attempting to mechanically compensate for all positioning errors through calibration, the metrology arrangement directly measures actual positions and provides correction data, simplifying the error compensation process while achieving high positioning accuracy.
Data Source
AI summary
A manufacturing system includes: a coordinate positioning machine having a structure moveable within a working volume of the machine, a drive arrangement for moving the structure around the working volume, and a positioning arrangement for determining the position of the structure within the working volume with a first accuracy; and a metrology arrangement to which the machine is removably couplable, such that when the machine is coupled to the metrology arrangement, with the structure being moved by the drive arrangement, the metrology arrangement is able to measure the position of the structure with a second accuracy that is higher than the first accuracy.