CNC Workpiece Alignment Using 3D Scanning for Hybrid Manufacturing
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Solution Overview
Problem
Existing CNC machining techniques face challenges in accurately aligning workpieces of irregular shapes, particularly those produced by additive manufacturing, due to their non-prismatic formations, which complicates the use of touch probes and requires impractical clamping methods.
Innovation Solution
A method involving the use of 3D scanning with handheld devices like mobile phones to generate scanned images of workpieces and fiducials, establishing a coordinate system, and aligning CAD models within these images, allowing for precise alignment and machining without the need for conventional probing or alignment with machine axes.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If touch probes are used to acquire workpiece position and orientation, then measurement can be performed, but the method becomes challenging and impractical for workpieces of irregular shape and non-prismatic formations
Solution Approach 1:
The patent replaces the mechanical touch probe system with an optical 3D scanning system. Instead of using physical contact probes to measure workpiece geometry, the system uses optical scanners to capture the complete 3D surface geometry of the workpiece, including fiducial markers. This substitution eliminates the operational difficulties of probing irregular shapes while maintaining measurement precision.
Solution Approach 2:
The patent creates a digital 3D copy of the physical workpiece through scanning. The scanned point cloud data represents a digital replica of the workpiece geometry, which can then be processed and aligned with the CAD model computationally. This copying approach allows for easier manipulation and measurement compared to direct physical probing.
2Manufacturing precision
If conventional probing methods are used for additive manufactured preforms, then machining can be performed, but clamping methods become impractical due to non-prismatic shapes
Solution Approach 1:
The patent introduces fiducial markers as intermediary elements that facilitate the manufacturing process. These markers are attached to the workpiece and serve as reference points for the scanning and alignment process. By using these intermediaries, the system can accurately locate and clamp irregularly shaped preforms without requiring complex custom fixtures for each unique geometry.
Solution Approach 2:
The patent changes the approach from mechanical fixture design to digital coordinate system transformation. Instead of designing physical fixtures for each preform shape, the system uses software-based coordinate system alignment between the scanned workpiece and CAD model. This parameter change from physical to digital domain enables versatile clamping strategies for various geometries.
3Adaptability or versatility
If 3D scanning with handheld devices is used, then alignment of irregularly shaped workpieces can be achieved, but the system complexity increases compared to conventional probing
Solution Approach 1:
The patent employs a universal fiducial marker design that can be used with any workpiece geometry. The same fiducial marker template serves multiple functions: providing geometric reference for scanning, enabling coordinate system establishment, and facilitating alignment with the CAD model. This universality reduces system complexity despite the enhanced adaptability to various workpiece shapes.
Data Source
AI summary
A method of computer numerical control (CNC) machining and of hybrid manufacturing are set forth. A more precise alignment of a computer-aided design (CAD) workpiece model, workpiece, and a CNC machine tool is furnished via employment of the method. The method has proved particularly useful for preform workpieces fabricated by additive manufacturing. The part outcome can more closely conform to the intended final part geometry. In an implementation, a coordinate system is established in a CNC machine tool, and a workpiece is fixed in the CNC machine tool. The fixed workpiece is scanned, and the coordinate system is located in the scanned image. Further, a computer-aided design (CAD) model of the workpiece is aligned in the scanned image, and the coordinate system is utilized as the work coordinate system, among other possible steps of the method.