Long-Bolt Clamping Assembly for Thermally Stable AACMM Joints
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Solution Overview
Problem
Portable articulated arm coordinate measuring machines (AACMMs) face challenges with joint loosening due to thermocycling, which affects calibration accuracy and reliability.
Innovation Solution
The AACMM incorporates a clamping arrangement with a tension spring to restrict non-rotational movement between axis assemblies, and uses a combination of materials like steel and other metals for the arm and fasteners, along with a yoke cap and fasteners that extend over at least 50% of the arm's length, to resist creep and maintain joint integrity.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If standard fastening connections are used in AACMM, then the device is easier to manufacture and assemble, but the connections loosen over time due to thermocycling, affecting calibration accuracy
Solution Approach 1:
The clamping arrangement is divided into distinct functional segments: a clamping mechanism with adjustable fasteners for securing the joint, a tension spring for maintaining clamping force, and positioning features for precise alignment. This segmentation allows each component to be optimized independently while working together to prevent joint loosening during thermocycling.
Solution Approach 2:
The clamping arrangement incorporates dynamic elements including an adjustable fastening mechanism that can be tightened or released as needed, and a tension spring that dynamically maintains clamping force. This allows the connection to adapt to thermal expansion and contraction while maintaining secure joint integrity.
2Strength
If material combinations are used for arm and fasteners, then the connection strength is improved, but the manufacturing complexity increases
Solution Approach 1:
Different materials are used in different locations of the clamping arrangement: steel fasteners and yoke cap for high-strength clamping surfaces, and compatible materials for the arm components. This local differentiation of material properties optimizes connection strength at the joint interface while maintaining ease of manufacture for the overall assembly.
Solution Approach 2:
The clamping arrangement employs composite construction combining steel fasteners and yoke cap with other metal components. This composite approach leverages the high strength and creep resistance of steel where most needed, while using other materials where appropriate for manufacturing ease and overall system compatibility.
3Stability of the object's composition
If fasteners extend over longer arm length, then the stability against creep is improved, but the device complexity increases
Solution Approach 1:
The fasteners are pre-positioned and distributed along at least 50% of the arm length during manufacturing, establishing stable clamping points before operation. This preliminary distribution of fasteners prevents creep by maintaining consistent clamping force across critical joint locations throughout the arm's operational life.
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 effectively reduces the risk of joint loosening and maintains calibration accuracy by providing a secure mechanical connection that withstands temperature variations and mechanical stress.
Implementation Method 1
The yoke cap and the plurality of fasteners form a tension spring that restricts non-rotational movement of the second component relative to the first component
Implementation Method 2
each of the plurality of nuts is mounted within the interior of the arm via an adhesive
Data Source
AI summary
An assembly includes a first component including an arm having a first end and a second end, a plurality of nuts positioned within an interior of the arm, a yoke cap, a plurality of fasteners threadably coupled with the plurality of nuts to affix the yoke cap to the first end of the arm, and a second component positioned between the first end of the arm and the yoke cap. The second component is rotatable about an axis relative to the arm.