Northwestern University Robert R. McCormick School of Engineering and Applied Science

Advanced Manufacturing Processes Laboratory

Surface Texturing

Motivation

Surface textures have a decisive impact on the functional performance of products. Proper patterns on structured surfaces could dramatically improve their optical, mechanical, thermal and biological properties. These structured surfaces usually have periodic patterns with micro/meso-scale features and cannot be fully described by conventional surface topography parameters, such as roughness, waviness, etc. Since they define the ultimate performance of many industrial components and products, micro-structured surfaces are assuming an ever-increasing role.

Challenges

It is difficult to efficiently and accurately machine micro-structure features on 3-D free-form surfaces, especially at mass production scales.

TMG Design

Fig. 1 Resonant-mode 2-D TMG design

Elliptical vibration texturing

Fig. 2 Principle of the Elliptical Vibration Texturing

Research Work

The development of the proposed process is composed of three interwoven tasks. Firstly, a resonant-mode tool vibration generator that can deliver the required elliptical trajectory at an ultrasonic frequency is designed and optimized. Secondly, a process simulation model is presented to study the surface generation mechanics including the minimum chip thickness and plowing effects. The process is then further extended to create channels and grid patterns by selecting proper combinations of the process parameters. Finally, the developed process is applied to create different micro-structures for surface wettability control.

Photos

Experimental Configuration

Fig.3: Experimental configuration: (a) machine setup and (b) zoom-in view.

 

Surface Topography

Fig. 4: Surface topography of machined examples.

 

Generated simulated topography

Fig. 5: Examples of generated and simulated surface topography of micro channels

 

Water droplet morphology

Fig. 6: Water droplet morphology on textured cylindrical surfaces. 

 

Results