# Research on path planning for clear aligner flexible manufacturing

## TL;DR

This paper introduces a new path planning method for manufacturing clear aligners using PCA-ICP registration and robot machining to improve automation and precision.

## Contribution

A novel PCA-ICP registration algorithm is proposed to enhance coordinate alignment and robot path planning for clear aligner manufacturing.

## Key findings

- The PCA-ICP registration algorithm achieves a maximum distance error of 0.03 mm.
- The method enables precise robot machining of clear aligners by generating accurate tool paths.
- The proposed approach effectively overcomes limitations of traditional milling path planning.

## Abstract

In recent years, clear aligner can enhance individual appearance with dental defects, so it used more and more widely. However, in manufacturing process, there are still some problems, such as low degree of automation and high equipment cost. The problem of coordinate system mismatch between gingival curve point cloud and dental CAD model is faced to. The PCA-ICP registration algorithm is proposed, which includes coarse match algorithm and improve-ICP registration algorithm. The principal component analysis (PCA) based method can roughly find the posture relationship between the two point clouds. Using z-level dynamic hierarchical, the ICP registration can accurately find the posture between these two clouds. The final registration maximum distance error is 0.03 mm, which is smaller than robot machining error. Secondly, the clear aligner machining process is conducted to verify the registration effectiveness. Before machining, the path is generated based on the well registered gingival curve. After full registration, the tool path is calculated by establishing a local coordinate system between the workpiece and the tool to avoid interference. This path is calculated and generated as an executable program for ABB industrial robots. Finally, the robot was used for flexible cutting of clear aligners and was able to extract products, ensuring the effectiveness of the proposed research. This method can effectively solve the limitations of traditional milling path planning under such complex conditions.