A new approach to Wire-Arc based Additive Manufacturing Process

A new approach to Wire-Arc based Additive Manufacturing Process

Introduction

We all know that Additive manufacturing has been used as a design and prototyping platform for nearly two decades but times are changing now and the Industry has switched on from prototyping to product making. Although in its infancy, it has clearly demonstrated its ability to revolutionize the way products can be designed, manufactured and marketed. Productivity of AM has been the talk of the town since its inception to the market as a competitor to subtractive manufacturing.

Due to process parameters,AM is typically suited for small or medium sized parts in low to medium volumes. Part size is typically limited,particularly with powder-bed fusion process.So,for Industrial applications the shift has moved towards Direct Energy Deposition (DED) which has larger deposition rates and are suitable to manufacture large components.

One promising DED technique is Wire Arc Additive Manufacturing (WAAM), which produces near net shape of the component by retrofitting the conventional welding setup.

What is WAAM?

WAAM is an additive manufacturing technology which deposits materials layer by layer by using electric arc as the heat source and wire as feedstock.

History of WAAM

  • The origin of WAAM dates back to 1926,where a Scientist named Baker had patented the use of electric arc as a heat source to generate 3D objects.
  • In 1983,shape welding was used to manufacture high quality large nuclear steel parts.
  • In 1993,Prinz and Weiss patented “Shape Deposition Manufacturing” with CNC milling.
  • From 1994-1999, Cranfield University patented “Shaped Metal Deposition(SMD)” for manufacturing Engine casings with different materials.

Why WAAM?

  • In Powder bed fusion process,it is not possible to build large components. WAAM is best suited for manufacturing large components
  • Less Material wastage -As it deposits the material in a layer by layer fashion to achieve the final part design.
  • Increased Design Flexibility- We can build any complex geometry using this process.
  • Reduction in lead time & Cost compared to conventional machining,Casting & Forging.

System Architecture of WAAM

A typical WAAM machine consists of the following :

  1. A Standard Welding equipment which includes welding power source,torch and wire feeding systems.
  2. A CNC Gantry table ( 3 or 5 axis )
  3. Argon gas cylinders
  4. Inert Gas chamber( In case of reactive materials)
  5. A computer Interface which converts the CAD design to G-codes

Process flow for WAAM

The process flow for the Wire Arc Additive Manufacturing is explained below

  1. A CAM software is used to program the tool paths and to program the starting and stop points of the welder and a wire feeder. The software is capable of converting any 3D Model into a 3D Printable code. The first step in this process is to ‘Slice’ the 3D model into numerous 2D layers which is then laid out in terms of precise paths for the 3D Printer to work on
  2. The CAM code is converted into coordinate system locations, based on the input design.
  3. The welding torch moves in the position of the coordinates and triggers the wire feeder to deposit the material in the path.
  4. Arc is ignited and the wire begins to feed into the molten weld pool in the given direction.
  5. Once the first layer is finished, the sufficient cooling time is given and the welding torch moves vertically and the second layer starts printing.
  6. Once after printing required number of layers, the final part is taken out. Then it goes through cleaning and machining process.

Materials Explored

  • Titanium Alloys
  • Aluminium alloys
  • Steels ( Maraging,stainless)
  • Invar
  • Inconel
  • Copper Alloys

Industrial Applications of WAAM

  • Mainly in Aerospace Industries to build bombardier Landing gear rib,Wing spar.
  • Impellers
  • Turbine blades
  • Shrouds & Linkages for various Industries

Market Players

  • Cranfield University in collaboration with various Industries (WAAMAT programme)
  • Norshk Titanium
  • Gefertec Gmbh

Future Challenges

  • Controlling the microstructure of materials through their solidification pattern
  • Minimize the defects like porosity,lack of fusion,oxidation
  • Developing thermal simulation models.
  • Establish online monitoring and control system.

Thus WAAM has proven to be a suitable alternative for large parts with complex geometries used in critical applications. With more research works being done all over the world, WAAM has the real caliber to evolve as an alternative to conventional manufacturing process for particular applications.

References

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