Additive Manufacturing is a very important and essential topic in Industry 4.0 transformation. Additive Manufacturing may be defined as a computer-controlled 3D Printing process that creates 3-dimensional objects by depositional materials such as proper polymers, ceramics, or metals in multiple layers of equal thickness. These objects are built layer by layer which is in contrast to traditional manufacturing that often requires machining or other techniques to remove surplus material.
In details, additive manufacturing is initiated by forming computer-aided design (CAD) and modeling that arranges a set of digital features of the product and submit descriptions of the items to industrial machines. The machines perform the transmitted descriptions as blueprints to form the item by adding material layers. The layers, which are measured in microns, are added numerous times until a three-dimensional object arises. Raw materials can be in the form of a liquid, powder, or sheet and are especially comprised of plastics, other polymers, metals, or ceramics.
The term “additive manufacturing” references technologies that grow three-dimensional objects one superfine layer at a time. Each successive layer bonds to the preceding layer of melted or partially melted material. 3D printing is about to replace all other names, including additive manufacturing, and to become the generally accepted generic term for layer technology. Additive manufacturing is a very important supportive technology of industry 4.0
Why additive manufacturing is called Rapid Prototyping?
The term Rapid Prototyping is defined as a process for rapidly creating an object or part representation before the final release or commercialization. In a product development context, the term rapid prototyping was used widely to describe technologies that created physical prototypes directly from digital data.
Other manufacturing processes require a complete production planning and detailed analysis of the part geometry to determine things like the sequence of processes in which different features can be fabricated, what tools and processes must be used, and what additional fixtures may be required to complete the part.
On the other hand, Additive Manufacturing needs only some basic dimensional details and a small amount of understanding as to how the 3d printing machine works and the materials that are used. As in the sheet metal stamping process, Every different part or component requires a separate press tool for every operation such as a blanking tool, drawing tool, or punching tool.
Basic Principle of the Additive Manufacturing or 3D Printing
All additive manufactured objects are built by joining single layers of equal thickness. A 3D model in CAD software converted into the STL file. In the STL file, then 3d model is divided into cross-sections, which contains information about each layer. The layer is shaped in a two-dimensional x-y plane. The third dimension i.e. z results from multiple layers being stacked up on top of each other, but not as a continuous z coordinate.
The models are therefore three-dimensional forms that are very exact on the two-dimensional x-y plane and owing to the described procedure are then stepped in the upward z-direction, whereby the smaller the z step is, the more the model looks like the original. The following Figure shows an example of a three-dimensional additive manufactured model.
Additive Manufacturing or 3D Printing Technologies
Over the past 3 decades, researchers and industrial companies developed several techniques for additive manufacturing and rapid prototyping. The Additive manufacturing processes may divide into three phases:
- A 3D model is designed in CAD software and converted into a Standard Tessellation Language (STL) format or other newer Additive Manufacturing file format.
- 3D printing machine manipulates the file to adjust the position and orientation of the part.
- 3D printing machine or additive manufacturing machine manufactures the part by sequential layers.
Stereolithography or Polymerization
Stereolithography is the first developed rapid prototyping or 3d printing technique. The Working principle of Stereolithography is to solidify the photosensitive liquid polymer by using an ultraviolet laser.
A 3D model in CAD software converted into the STL file. In the STL file, then 3d model is divided into cross-sections, which contains information about each layer. The thickness of the layer defines the resolution, which is dependent on the equipment used. A support structure is needed to build to part on. A laser beam traces the cross-section information provided by the STL file to build the part layer by layer. When the process is completed, the excess liquid polymer is drained.
3DP Binder Jetting Technology
3DP Binder Jetting is capable of printing a variety of materials including ceramics. Some materials, like sand, require no additional processing. Other materials are typically cured and sintered and sometimes infiltrated with another material, depending on the application. Hot isostatic pressing may be employed to achieve high densities in solid metals. Binder Jetting also has the ability to print very large objects.
In the 3DP technique, polymer powder is fused using the water-based liquid binder supplied from the jet nozzle. Powder particles are glued together layer by layer. A wide range of polymers can be used for this process. It is a fast process and the material cost is low. On the other hand, the surface finish is rough.
Fused Deposition Modeling
In the Fused Deposition Modelling technique, print head liquefies the thermoplastic material and deposits in layers on the substrate. The material is heated just enough to make it viscous so that it can solidify immediately. Different types of materials can be used such as wax, metals, and ceramics. Low maintenance cost and its compact size are the positive attributes of the Fused Deposition Modelling technique. On the other hand, temperature fluctuations result in delamination and long printing time.
Selective Laser Sintering
Selective Laser Sintering is a process, where printing material such as polymers, metals, ceramics, and glass are fused together by using a carbon-dioxide laser beam. The powder material is fused layer by layer according to 3d model design. The sintered powdered material will construct the 3D design while the un-sintered will be cleaned for reuse after the part is built. SLS is used to 3D print complex parts quickly with better durability as compared to other additive manufacturing technologies.
Laminated Object Manufacturing
Laminated object manufacturing is a combination of subtractive and additive manufacturing techniques. In the Laminated Object Manufacturing process, a sheet of material represents each layer. Laser cutting is used to manufacture each sheet of material according to STL file information. Later sheets of materials are attached together by using heat and pressure. Materials such as paper, plastics, metals, and composite materials can be used as a building material.
Laser Engineered Net Shaping
Laser Engineered Net Shaping is an additive manufacturing process where melted metal powder is injected at specific points or paths layer by layer to build the 3D part according to the STL file information. This process can also be utilized to repair damaged parts.
Advantages of Additive Manufacturing
The Additive Manufacturing Processes offers many advantages that are not possible in traditional manufacturing processes. Some of the important advantages are as follows:
Generally, Additive Manufacturing only uses the raw material needed to manufacture the 3d object and leftover raw material can be used for another operation. On the other hand, A large amount of raw material is wasted in traditional manufacturing processes.
Flexibility in Production
Most of the parts need several manufacturing steps as per PPAP (Production Part Approval Process) which affects the overall quality of the product. But in the 3D printing technique, any complex part manufacture only in one process and eliminates the order of several processes on product quality.
With conventional techniques, producing a prototype may take several days or even weeks while Additive Manufacturing technologies provide the functional working prototype very soon as compared to traditional manufacturing techniques.
Variety in part-design
Since complex parts can be produced with little setup cost custom designed products can be produced with little cost very easily. Anything that can be designed in CAD software can be produced.
Additive Manufacturing processes reduce waste and do not use hazardous materials such as cooling liquids, and thus reduce pollution.
Disadvantages of Additive Manufacturing
Since very complex parts can be made by 3D printing process and many top manufacturing industries adapted this technology nevertheless it has some disadvantages as follows:
Slow Production Rate
The Additive Manufacturing process is not suitable for mass production considering its low speed for producing one part.
Rough Surface Finish
Producing the part layer by layer often results in a rough surface finish. Extra work has to be done on the parts in order to get a smooth surface finish.
Limitation in size of parts
In most of the 3D printing processes, powder materials or liquid polymers are used to manufacture parts. Due to these material’s low strength, the large size parts cannot be produced.
In 30 years, 3D printing technology has made great progress and many industries are using additive manufacturing for rapid prototyping and other commercial purposes. Since researchers are still making it better day by day, it will have a profound impact in the field of manufacturing in the future.
Even today AM has a great impact on society in many aspects such as in the field of healthcare, Decoratives, automobiles, aerospace, etc. Brand new technologies such as 3D bioprinting is a highly-advanced manufacturing platform that allows for the printing of tissue, and eventually vital organs, from cells. This could open a new world of possibilities for the medical field, while directly benefiting patients who need replacement organs.