ANALYSING MECHANICAL PROPERTIES OF A FLAT PLATE FABRICATED BY WIRE ARC ADDITIVE MANUFACTURING PROJECT REPORT

INTRODUCTION

1.1 Additive manufacturing(AM) Additive manufacturing, also known as 3D printing, rapid prototyping or freeform fabrication, is ‘the process of addition of materials on layer by layer deposition method to make objects from 3D model data, usually layer upon layer, as opposed to subtractive manufacturing methodologies such as machining.

Additive manufacturing (AM) is a technology that promises to reduce part cost by reducing material wastage and time to market. Furthermore, AM can also enable an increase in design freedom, which potentially results in weight saving as well as facilitating the manufacture of complex assemblies formerly made of many subcomponents. A basic AM system consists of a combination of a motion system, heat source and feedstock.

It is a suitable process to produce complex metal net shape parts, and not only prototypes, as before. Additive manufacturing now enables both a design and industrial revolution, in various industrial sectors such as aerospace, energy, automotive, medical, tooling and consumer goods.

Early use of AM in the form of Rapid Prototyping focused on preproduction visualization models. More recently, AM is being used to fabricate end-use products in aircraft, dental restorations, medical implants, automobiles, and even fashion products.

1.2 Classification of Additive Manufacturing processes
According to the standard terminology for AM by ASTM (ASTM F2792), AM technologies for metal components are mainly classified into

Each process is naturally suitable for certain applications. For instance, selective laser melting delivers net shape components with high resolution; however, similarly to electron beam melting, deposition rates are relatively low, and part size is limited by the enclosed working envelope.

1.3 Wire Arc Additive Manufacturing

1.3.1 Introduction
The combination of an electric arc as heat source and wire as feedstock is referred to as WAAM. The first patent was filed in 1925. WAAM hardware are welding power source, torches and wire feeding systems. Motion can be provided either by robotic systems or computer numerical controlled gantries.

1.3.2 Processes
MIG welding is common among the automated welding process. The wire is the consumable electrode, and its co-axiality with the welding torch results in easier tool path. In particular, Fronius cold metal transfer (CMT) is a modified MIG variant, which relies on controlled tip transfer mode mechanism; this is supposed to deliver beads with excellent quality, lower thermal heat input and nearly without spatter while meeting these expectations when depositing materials such as aluminium and steel.

For titanium, this process is affected by arc wandering, which results in increased surface roughness. Consequently, tungsten inert gas, or plasma arc welding, is currently used for titanium deposition. These processes, however, rely on external wire feeding; for deposition.

1.3.3 Motion control robotic system
Industrial robots are automated, programmable and capable of movement on two or more axes.
Typical applications of robots include welding, painting, assembly, pick and place for printed circuit boards, packaging and labeling, palletizing, product inspection, and testing; all accomplished with high endurance, speed, and precision. They can help in material handling and provide interfaces.
Mostly Six axis robotic system is in commercial use, because of its freeform motion.

1.3.4 End-of-arm tooling

The most essential robot peripheral is the end effector, or end-of-arm- tooling (EOT). Common examples of end effectors include

 Welding devices (such as MIG-welding guns, spot-welders, etc.),
 spray guns for painting robots,
 Grinding and deburring devices (such as pneumatic disk or belt grinders, burrs, etc.),
 Grippers (devices that can grasp and usually electro mechanical or pneumatic).
 Another common means of picking up an object is by vacuum

End effectors are frequently highly complex, made to match the handled product and often capable of picking up an array of products at one time. They may utilize various sensors to aid the robot system in locating, handling, and positioning products.
For WAAM process, we uses end-of-arm-tooling (EOT) as MIG welding torch.

1.3.5 MIG Welding or Gas metal arc welding (GMAW)
MIG is a welding process in which an electric arc forms between a consumable wire electrode and the workpiece metal(s), which heats the workpiece metal(s), causing them to melt and join.

Along with the wire electrode, a shielding gas feeds through the welding gun, which shields the process from contaminants in the air. The process can be semi-automatic or automatic. A constant voltage, direct current power source is most commonly used with GMAW, but constant current systems, as well as alternating current, can be used.

1.3.6 Metal transfer
There are four primary methods of metal transfer in GMAW,
 Globular
 Short-circuiting
 Spray
 Pulsed-spray
 Cold metal transfer

Globular
GMAW with globular metal transfer is considered the least desirable of the three major GMAW variations, because of its tendency to produce high heat, a poor weld surface, and spatter. The method was originally developed as a cost efficient way to weld steel using GMAW, because this variation uses carbon dioxide, a less
expensive shielding gas than argon. Adding to its economic advantage was its high deposition rate, allowing welding speeds of up to 110 mm/s (250 in/min). As the weld is made, a ball of molten metal from the electrode tends to build up on the end of the electrode, often in irregular shapes with a larger diameter than the electrode itself. When the droplet finally detaches by gravity, it falls to the workpiece, leaving an uneven surface and often causing spatter. As a result of the large molten droplet, the process is generally limited to flat and horizontal welding positions, requires thicker workpieces, and results in a larger weld pool.