Welded Articulated CMM Joints for Lightweight Measurement Accuracy
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Solution Overview
Problem
Conventional portable coordinate measuring machines face challenges in achieving high accuracy due to thermal and load-induced warping, resulting in reduced precision and are often bulky and heavy, making them less desirable.
Innovation Solution
A portable coordinate measuring machine is designed using a welding approach for assembling rotary joints from separate parts, which is less expensive and time-consuming than machining from a single block of steel, and employs an articulated arm error mapping process to correct potential imprecision, allowing for improved precision and reduced weight.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If conventional portable coordinate measuring machines use traditional machining or casting methods to manufacture joints, then manufacturing precision may be maintained, but weight and bulk increase significantly
Solution Approach 1:
The joint is divided into multiple separate components (barrel, connecting portions, etc.) that are welded together rather than machined from a single block. This segmentation reduces material usage and weight while maintaining structural integrity through welding and error mapping compensation.
2Measurement precision
If conventional portable coordinate measuring machines use improved accuracy designs, then measurement precision increases, but device complexity and manufacturing cost increase
Solution Approach 1:
An articulated arm error mapping process is implemented to measure and compensate for imprecision introduced by welding. This feedback mechanism allows the system to correct for manufacturing variations, achieving high accuracy without requiring extremely complex manufacturing processes.
3Ease of manufacture
If welding is used to assemble joint parts, then manufacturing cost and time are reduced, but potential imprecision is introduced
Solution Approach 1:
The welding process is followed by an error mapping measurement process that quantifies the imprecision introduced. This feedback allows for computational compensation of welding-induced errors, maintaining manufacturing simplicity while achieving required precision.
4Measurement precision
If portable coordinate measuring machines are designed for high accuracy, then measurement precision improves, but portability deteriorates due to increased weight
Solution Approach 1:
By segmenting the joint into weldable components rather than using a single heavy machined block, the overall weight is reduced while maintaining accuracy through error mapping. This enables high-precision measurements in a portable form factor.
Data Source
AI summary
A coordinate measurement machine (CMM) includes a manually-positionable articulated arm having first and second ends. The articulated arm includes a plurality of arm segments and a plurality of rotary joints. The first end includes a connector configured to connect to a measurement probe. The second end includes a base for mounting the CMM. A housing of at least one rotary joint from the plurality of rotary joints has a cylindrical outer surface that engages a) the base or b) a connecting portion that connects the at least one rotary joint to another rotary joint from the plurality of rotary joints, the housing welded to the base or to the connecting portion.