Kinematic Mount Wave Spring Isolation for Laser Scanner Accuracy
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Solution Overview
Problem
Existing coordinate measurement machines (CMMs) with laser scanners face inefficiencies due to non-constant errors caused by kinematic mounts, which can lead to deflections in the laser scanner assembly, especially when the touch probe contacts a measured article, making it difficult to account for these errors accurately.
Innovation Solution
The implementation of an articulated arm CMM with a kinematic mount that includes a nut with a threaded portion, a wave spring or coil spring, and a padding member to mechanically isolate the base plate from the articulated arm, allowing for secure mounting while minimizing deflections and thermal influences.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of operation
If a kinematic mount is used to allow easy removal and replacement of the laser scanner, then ease of operation is improved, but measurement precision deteriorates due to forces causing deflections in the laser scanner assembly
Solution Approach 1:
A compliant mounting mechanism is introduced as an intermediary between the kinematic mount and the laser scanner assembly. This compliant mechanism acts as a mediator that absorbs mounting forces through controlled deflection, preventing these forces from being transmitted to the laser scanner and touch probe, thereby maintaining measurement precision while preserving ease of operation
Solution Approach 2:
The mounting mechanism transitions from a rigid connection to a compliant connection by changing the mechanical stiffness parameter. The compliant mounting mechanism allows controlled deflection under load, transforming the force transmission characteristics to protect the measurement system from deflections caused by kinematic mount forces
2Device complexity
If the laser scanner is intimately mounted with the touch probe to combine measurement functions, then device complexity is reduced, but measurement precision deteriorates due to force transmission causing deflections
Solution Approach 1:
The compliant mounting mechanism serves as an intermediary layer between the integrated laser scanner and touch probe assemblies. This intermediary absorbs and isolates forces generated during touch probe contact, preventing force transmission to the laser scanner while maintaining the physical integration and reduced complexity of the combined mounting structure
3Reliability
If rigid mounting is used to secure the laser scanner firmly, then reliability is improved, but measurement precision deteriorates due to inability to accommodate thermal expansion and deflection
Solution Approach 1:
The mounting mechanism changes from a rigid, fixed-stiffness connection to a compliant, flexible connection that can accommodate dimensional changes. The compliant mounting mechanism allows controlled deflection and thermal expansion without compromising the stability and reliability of the laser scanner mounting, while simultaneously maintaining measurement precision
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 configuration enhances the accuracy of measurements by reducing non-constant errors and thermal effects, allowing for more precise geometry data acquisition with reduced deflection and improved handling of the laser scanner assembly.
Implementation Method 1
a spring, particularly a wave spring or a coil spring, or a padding member mounted on the receiving portion between the nut and the base plate, such that movement of the nut along the receiving portion causes the spring or the padding member, respectively, to urge the base plate against the articulated arm to secure the kinematic mount, the spring or the padding member, respectively, mechanically isolating the base plate from the articulated arm
Implementation Method 2
the spring or the padding member, respectively, mechanically isolating the base plate from the articulated arm
Data Source
AI summary
An articulated arm can include a plurality of articulated arm members, a probe, a receiving portion at a distal end comprising a threaded portion, and a base at a proximal end. A base plate can kinematically mount on the receiving portion and have a hole positioned such that the probe passes through the hole. The base plate can also couple to a laser and an optical sensor located on opposite sides of the hole. A nut can threadably mount to the threaded portion of the receiving portion. Further, a wave spring can mount on the receiving portion between the nut and the base plate. Thus, movement of the nut along the receiving portion can cause the wave spring to urge the base plate against the articulated arm to secure the kinematic mount. The wave spring can then mechanically isolate the base plate from the articulated arm.