Today, hybrid manufacturing technology has drawn significant interests from both academia and industry due to the capability to make products in a more efficient and productive way. Although there is no specific consensus on the definition of the term ‘hybrid processes’, researchers have explored a number of approaches to combine different manufacturing processes with the similar objectives of improving surface integrity, increasing material removal rate, reducing tool wear, reducing production time and extending application areas. Thus, hybrid processes open up new opportunities and applications for manufacturing various components which are not able to be produced economically by processes on their own. This review paper starts with the classification of current manufacturing processes based on processes being defined as additive, subtractive, transformative, joining and dividing. Definitions of hybrid processes from other researchers in the literature are then introduced. The major part of this paper reviews existing hybrid processes reported over the past two decades. Finally, this paper attempts to propose possible definitions of hybrid processes along with the authors’ classification, followed by discussion of their developments, limitations and future research needs.

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A review of hybrid manufacturing processes – state of the art and future perspectives

The surface integrity of machined metal components is critical to their in-service functionality, longevity and overall performance. Surface defects induced by machining operations vary from the nano to macro scale, which cause microstructural, mechanical and chemical effects. Hence, they require advanced evaluation and post processing techniques. While surface integrity varies significantly across the range of machining processes, this paper explores the state-of-the-art of surface integrity research with an emphasis on their governing mechanisms and emerging evaluation approaches. In this review, removal mechanisms are grouped by their primary energy transfer mechanisms; mechanical, thermal and chemical based. Accordingly, the resultant multi-scale phenomena associated with metal machining are analyzed. The contribution of these material removal mechanisms to the workpiece surfaces/subsurface characteristics is reviewed. Post-processing options for the mitigation of induced surface defects are also discussed.

Surface integrity in metal machining - Part I: Fundamentals of surface characteristics and formation mechanisms

Electrochemical machining of complex components of aero-engines: Developments, trends, and technological advances

From Germany’s Industry 4.0 mission to Made in China 2025 and Make in India mission to British Factory of the Future in 2050, digital manufacturing (DM) is promoting in the world’s major industrial countries as a technology foundation of the future manufacturing. At the same time, in the different segments of the DM realm, different forms of information technologies (IT) are flourishing such as the following: computer-aided manufacturing, robotics control in manufacturing, and process simulation. This paper is aimed to review the latest initiatives of DM in the leading universities and major industrial countries. Along with, a critical literature review of various initiatives in the area of DM-assisted hybrid additive manufacturing (DM-HAM) has also been carried out. DM-HAM seems to be very promising for next generation multi-operational manufacturing as it is time saving and economical. The highlights of this review will provide a guide for the upcoming research activities in the area of DM-HAM.

A review of digital manufacturing-based hybrid additive manufacturing processes

This article discusses the recent advances in polishing of advanced materials. Ninety-five journal articles published in 2005–2007 are briefly introduced. The topics are advances in chemical mechanical polishing (CMP), fluids for polishing, modeling of polishing, polishing of brittle materials, robotic polishing, polishing with vibrations or beams, and friction in polishing processes. CMP is perhaps the hottest research topic in the articles reviewed. Many “noncontact” processes are developed using magnetic fluids, electrorheological fluids, and abrasive flow for polishing of complicated geometries or difficult-to-approach regions. Modeling of polishing processes helps to understand the polishing mechanisms and is thus increasingly performed worldwide. More research on simulations of polishing processes can be expected in the near future. Polishing of brittle materials is also highly demanded. Automatic polishing of curved surfaces using robots and CNC machines, and polishing with vibrations and beams are...

Recent Advances in Polishing of Advanced Materials

Investigation of the electrochemical dissolution behavior of Inconel 718 and 304 stainless steel at low current density in NaNO3 solution

Electrochemical Dissolution Behavior of the Nickel-Based Cast Superalloy K423A in NaNO3 Solution

Effect of the breakdown time of a passive film on the electrochemical machining of rotating cylindrical electrode in NaNO3 solution

A new electrochemical machining (ECM) process named rotate-print ECM (RPECM) is proposed to meet the requirement of machining revolving parts with complex convexity structures. During the RPECM process, a revolving cathode tool was employed to replace a set of complicated block tools used in conventional sinking ECM process. In this paper, the design method of the revolving cathode tool based on the analysis of an equivalent model for the RPECM process was emphasized. The radius and window edge contour of the cathode tool were designed by optimizing the motion trails of the window edge points and their deviations from the required sidewall profile of the target convexity. A cylindrical test piece was machined experimentally to verify the designed tool. The results showed that the machined cylinder surface is smooth without any flow tracks and residual ribs. A convexity with complex top face contour was fabricated successfully. It can be seen that the sidewall profile is tapered and the edge is nearly trenchant. The processing error of the sidewall profile can be effectively controlled by optimizing the radius and window size of the cathode tool.

Cathode design and experimental study on the rotate-print electrochemical machining of revolving parts

Stray corrosion is a common phenomenon that occurs at the surface adjacent to the machining area during electrochemical machining (ECM). It can cause unwanted metal removal and has a substantial effect on the ECM precision. Standard through-mask ECM prevents stray corrosion with a locally insulated anode, which requires the insulating material to be positioned accurately and applied through a complex process, including resist application, exposure, developing, and stripping. This paper presents a new method for reducing stray current attack by using an iron coating on the surface of the anode workpiece in NaNO3 solution. The application of the iron coating to the whole initial surface of the workpiece does not require precision, and the process is simple and economical. Because the iron coating is passivated at low current densities and can be easily applied or removed, it can be used to reduce the stray current attack. The η-i curves of the nickel-based alloy, Inconel 718, show that its dissolution efficiency is higher at low current densities, indicating poor localization and severe stray corrosion during ECM. A simulation and an experimental study of ECM a convex on iron-coated and uncoated Inconel 718 workpieces were performed. The results showed that the iron coating on the surface of the workpiece significantly improves the machining accuracy. It reduces stray corrosion and the amount of stray removal on the non-machined top surface of the convex workpiece.

Zengwei Zhu

Papers

Investigation of the electrochemical dissolution behavior of Inconel 718 and 304 stainless steel at low current density in NaNO3 solution

Electrochemical Dissolution Behavior of the Nickel-Based Cast Superalloy K423A in NaNO3 Solution

Effect of the breakdown time of a passive film on the electrochemical machining of rotating cylindrical electrode in NaNO3 solution

Cathode design and experimental study on the rotate-print electrochemical machining of revolving parts

Reduction of stray corrosion by using iron coating in NaNO3 solution during electrochemical machining