Research at PEARL Group

Metal additive manufacturing (AM) is gaining significant attention in the modern industrial world due to the inherent design freedom that facilitates complex part production. Moreover, the technology offers exceptional benefits such as mass customization and minimal scrap formation. However, the parts/components produced using metal AM always exhibit poor surface integrity and lack of geometrical form accuracy. Moreover, fabrication of internal features (holes) having smaller dimensions is challenging in metal AM due to the detrimental effects of build orientation. Therefore, post-processing of metal additive manufactured (AM) parts/components is inevitable for enhancing the acceptability of these components at application level in industries. Thus, a low energy electric discharge assisted surface post-treatment approach was proposed and investigated with an aim to overcome the limitations of metal AM parts. Wire electrical discharge polishing (WEDP) and electric discharge internal processing (EDIP) are the two variants considered for finishing external (planar + non-planar) and internal AM features respectively. The proposed approach proved to be efficient in enhancing the surface integrity (sub-micron finish) and form accuracy of metal AM surfaces irrespective of variations in part geometry and differences in material properties.

Ultra-precision machining aims to achieve atomic-scale accuracy and surface finish to create mirror- like surfaces that are used in optics, electronics, biomedical and aerospace industries. The process utilizes diamond tools to produce aspherical, free-form and structured optical components such as lenses, mirrors and diffraction gratings. The achievable precision depends on the machine capacity as well as the process limit. Nowadays, advance machines with resolution control of 1 nanometer were already developed. However the machining process is limited by the size effect. The main contributor for the size effect is found to be the edge radius of the tool. Below a certain ratio of uncut chip thickness to edge radius the process becomes un-scalable due to material strengthening effect. The fundamental mechanism responsible for the strengthening effect and its relation to the surface integrity is not clearly understood. Our research investigates the above shortcoming using both experimental and numerical methods from materials perspective.

Heat-assisted machining, and more specifically, laser-assisted machining (LAM), is an innovative manufacturing technique that combines the precision of machining with the localized application of high-intensity laser energy to enhance the material removal process. In LAM, a focused laser beam is directed at the workpiece material, creating a localized region of intense heat. This thermal energy softens the material, reducing its hardness and making it easier to machine. This added heat assists in various machining operations, such as drilling, cutting, and milling, allowing for improved process efficiency and reduced tool wear. Moreover, laser-assisted machining provides greater control over material removal, resulting in higher precision and surface finish quality. One of the key advantages of laser-assisted machining is its versatility. It can be applied to a wide range of materials, including metals, ceramics, and composites, which may be challenging to machine using conventional methods due to their hardness or brittleness. LAM can significantly increase the tool life by reducing wear and friction, making it particularly useful in high-precision applications where tool longevity is essential. Additionally, the localized heat input minimizes the heat-affected zone (HAZ) and distortion in the workpiece, ensuring the integrity of the machined parts. 

Vibration assisted machining (VAM) was introduced in 1950’s in order to improve the machining performance of various machining processes. Low or high frequency vibration is introduced to the tool to provide an intermittent cutting action with the idea of reducing the contact time between the tool and worksurface. By reducing the contact, the traditional machining disadvantages such as excessive cutting force, high cutting temperatures, severe tool wear and poor surface quality can be improved. Surfaces with micro or nano features can be fabricated with VAM, which can provide useful functions such as friction performance, wettability of surface etc. VAM is classified as one-dimensional VAM, two-dimensional VAM and three-dimensional VAM based on the directions along which the vibration is applied.