Conceptual Design of a High-Speed Wire EDM Robotic End-Effector Based on a Systematic Review Followed by TRIZ

Sergio Tadeu Almeida,Songlin Ding,John Mo,Xiangzhi Wang,Cees Bil

doi:10.3390/machines9070132

Abstract

Exotic materials such as titanium offer superior characteristics that, paradoxically, make them hard-to-cut by conventional machining. As a solution, electric discharge machining (EDM) stands out as a non-conventional process able to cut complex profiles from hard-to-cut materials, delivering dimensional accuracy and a superior surface. However, EDM is embodied in CNC machines with a reduced axis and machining envelope, which constrains design freedom in terms of size and shape. To overcome these CNC constraints, traditional machining using six-axis industrial robots have become a prominent research field, and some applications have achieved cost efficiency, an improved envelope, and high flexibility. However, due to the lack of stiffness and strength of the robot arm, accuracy, material rate removal, and surface finishing are not comparable to CNC machining. Therefore, the present study investigates the design of a novel WEDM combined with six-axis robotic machining to overcome the limitations of traditional robotic machining and enhance EDM applications. This study extends the work of a conference paper to confirm potential outcomes, quantifying and ranking undesired interactions to map technical problems and applying the TRIZ approach to trigger solutions. Finally, an effective robotic end-effector design is proposed to free EDM from CNC and deliver robotic machining as a flexible and accurate machining system for exotic materials.

Highlights

For both electric discharge machining (EDM) and industrial robotic arms (IR), most of the best practices, advances, strengths, and limitation can be found in the form of methods, processes, and tools (MPT)
As an outcome of a systematic review, we found the current opportunities and limitations in EDM and IR machining and how they have been addressed
IR mature programming software can assist flexible processes configurations, and increased sensing is applied for EDM stochastic parameters

Summary

Introduction

Exotic materials have received much attention, including superalloys, ceramics, composites, semi- and superconductors [1]. The most prominent industry examples are observed within the two groups. The first focuses on cutting tools (e.g., carbide and polycrystalline diamond), which are used, for example, to drill large diameter holes in airframes [2] or to machine composite materials [3]. The second group focuses on hard-to-cut metals, such as titanium, molybdenum, and superalloys, with applications in highly demanding aerospace, automotive, and military applications, and are important in medical equipment [4] and bio-implants [5]. Exotic materials are often characterised by poor thermal conductivity, high toughness, ultra-hardness, and extremely high hardening behaviour that, when combined, will lead to laborious machining [6]. Exotic materials come under the category of hard-to-cut materials [7]

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