## 2 Literature Review  
At present, the research on the coating design of machine tools mainly includes studies of coating materials, coating processing, and coating applications and evaluation.  
(1) The material properties of the coating are employed in conjunction with the product in order to optimize it. [PERSON] et al. [6] developed a novel approach applying several PVD and CVD (coating + substrate) integrated systems for the purpose of austenitic stainless-steel machining, which increased the tool wear life performance. [PERSON] et al. [7] experimentally evaluated the machining performance of TiAlN-, AlCrN-, and TiAlN/AlCrN-coated carbide cutting tools and uncoated carbide cutting tools for machining Inconel 825 alloy. [PERSON] et al. [8] obtained sol-gel coating materials with an enhanced corrosion protection capacity for galvanized steel by incorporating organic precursors into an epoxide-functionalized silica-zirconia matrix, which could extend the service life of the galvanized parts. [PERSON] et al. [9] fabricated thermoplastic polymer composites using different lateral flow materials as fillers and confirmed the improvement of their mechanical properties. [PERSON] et al. [10] used a new ionic co-discharge method to prepare Ag-Bi nanocomposite coatings, which significantly improved the mechanical properties of the coatings.  
(2) Combined with various modern technologies, quality control research on the coating process has been carried out. [PERSON] et al. [11] determined the optimum CNC machining parameters for the wood surface quality through the optimization and adjustment of CNC machining parameters by ANN (artificial neural network). [PERSON] et al. [12] proposed a new method that can be used to capture and edit the anisotropic behavior of effect coatings, allowing users to quickly explore and evaluate the visual effects of anisotropy on effect coatings in a virtual environment. [PERSON] et al. [13] developed an artificial intelligence method to automatically classify coated parts, which has shown great potential in controlling the plating process parameters. [PERSON] et al. [14] developed an Ni-Cr-40 Al2O3 coating on stainless steel (SS316L) substrate by high-speed flame spraying and then used post-treatment agitated friction machining, providing an effective solution to the problem of corrosion in fluid machinery.  
(3) Various measuring devices have been developed in combination with different research methods to optimize the evaluation of coating applications. [PERSON] [15] developed a measuring device that can analyze coating colors and flash values at multiple angles with a high angular resolution, which was helpful in developing the appearance of effective coatings. [PERSON] et al. [16] used a prototype infrared transmission microscope to assess the micron-level coating coverage on a polypropylene-based conveyor, identifying the machine breakdown by identifying artefacts in the coating. [PERSON] et al. [17] discussed and evaluated the imaging capabilities of PAUT (5 MHz) and near-field microwave imaging systems (33.5 GHz) for multiple artificial surface defect samples and benchmarked the images produced by the systems to avoid the machine breakdown or material defects.  
As can be seen from the above study, these studies on the coating design of machine tools mainly focus on technical areas, such as the materials, processing technology, and application evaluation, while coating research related to the optimization design of the product appearance is lacking. This study combines eye-tracking experiments and virtual reality technology to further research and establish design criteria.