Additive Manufacturing Processes

Frontmatter

Chapter 1. Introduction

Abstract

Additive manufacturing (AM), a concept existing for the last 10,000 years, is defined and positioned among other manufacturing processes. The role of tools to separate processes is given. Its main difference from machining is highlighted, and the relation between its complexity and cost is visited. It is classified into two major categories: additive layer manufacturing and additive non-layer manufacturing. Various AM processes are summarized with few lines each, which will provide a quick glimpse into all AM processes. The roles of various processes in processing metals, ceramics, polymers, composites and functionally graded materials are succinctly mentioned.

Sanjay Kumar

Chapter 2. Classification

Abstract

In order to classify additive manufacturing (AM) processes, it is checked why they are different from each other. Their differences in terms of materials, energy sources, types of feedstocks used and conveyance of feedstocks are studied and attempts are done to classify on the basis of these differences. AM processes, whether they are additive layer manufacturing type or additive non-layer manufacturing type, are each classified into three types: material bed process, material deposition process and motionless material process. This classification allowed to accommodate all existing AM processes. Besides, this classification provides plenty of space to accommodate future AM processes.

Sanjay Kumar

Chapter 3. Laser Powder Bed Fusion

Abstract

Both selective laser sintering (SLS) and selective laser melting (SLM) are laser powder bed fusion. This chapter provides working of SLS and SLM and the role of their various parameters. Fabrication speeds due to these processes are low which is one of the drawbacks of additive manufacturing; this chapter provides various methods to increase the speed. It is reasoned why there are only two binding mechanisms (liquid phase sintering and full melting) instead of four (liquid phase sintering, full melting, solid state sintering and chemical-induced binding) in laser powder bed fusion. Application of the process in the repair of a 3D part, though not commonly practiced, is given.

Sanjay Kumar

Chapter 4. Electron Beam Powder Bed Fusion

Abstract

Electron beam powder bed fusion (EPBF) is a process in which an electron beam is used to scan a powder bed. In order to comprehend beam-powder bed interactions and the role of various process parameters such as scan speed and beam power, it is essential to know how a beam is generated and manipulated. This chapter describes the process in detail and clarifies the roles of electric current and voltage. The process competes with selective laser melting (SLM), and it is of interest to know how this process is different. Detailed difference between EPBF and SLM is given.

Sanjay Kumar

Chapter 5. Other Powder Bed Processes

Abstract

Beam based powder bed fusion makes complex parts, but the process is slow, energy-inefficient and is not cost-effective to make low-value parts. Powder bed processes such as high speed sintering, selective heat sintering, binder jet three-dimensional printing and other emerging processes (micro heater array powder sintering, localized microwave heating based additive manufacturing, multi jet fusion) are more energy-efficient and cost-effective – the present chapter describes these processes. There are various types of scanning such as pointwise scanning, linewise scanning and areawise scanning which impact fabrication rate and resolution. Difference between these types of scanning is explained.

Sanjay Kumar

Chapter 6. Beam Based Solid Deposition Process

Abstract

Beam based solid deposition process is used to fabricate large parts having medium complexity. This chapter describes laser beam based and electron beam based solid deposition process. Different types of powder depositions such as coaxial continuous, coaxial discrete and off-axial are given while laser-powder interactions are briefly explained. How repair occurs is explained with an example while difference between two types of feedstocks such as wire and powder in terms of their efficiencies in processing is elaborated.

Sanjay Kumar

Chapter 7. Other Solid Deposition Processes

Abstract

It is essential to know arc before knowing arc based additive manufacturing (AM) processes such as gas tungsten arc welding based AM, gas metal arc welding based AM and plasma arc welding based AM. Similarly, it is essential to know cold spray before knowing cold spray based AM. This chapter attempts to describe arc, cold spray and related AM processes. There are friction based processes such as additive friction stir deposition and friction surfacing based AM – these are explained. Extrusion based processes based on both filament and pellet are given.

Sanjay Kumar

Chapter 8. Liquid Based Additive Layer Manufacturing

Abstract

Liquid based AM processes are varied: in one extreme very big parts can be made by photopolymerization and in the other extreme thinner lines are deposited for electronics applications; besides, this is the liquid which has started non-layer based AM processes. This chapter has brought all processes together, though it deals only with layer based processes. While photopolymer bed and liquid deposition process are briefly mentioned, water based process and slurry based process are dealt with in somewhat detail. This chapter has reasoned why the name stereolithography is illogical, and thus photopolymer bed process described in Chap. 2 can instead be a better name. Four-dimensional printing utilizes liquid based AM processes and therefore its relation with liquid based AM processes is mentioned.

Sanjay Kumar

Chapter 9. Air and Ion Deposition Processes

Abstract

For fabricating a part of size some 100 microns or few millimetre, a resolution of nanometre is required. There are some processes such as aerosol jetting and electrochemical additive manufacturing (AM) which add ions by ions or atoms by atoms to make parts with a possibility to have nanometre resolution. These processes have potential to be applied in the area of fabricating electronic lines and parts having micropores. This chapter describes these air based and ion based processes and explains why electrolytic solution based AM processes have potential to overcome manufacturing problems posed by layer upon layer processes.

Sanjay Kumar

Chapter 10. Additive Non-layer Manufacturing

Abstract

The progress of additive manufacturing (AM) is hindered due to some of its unavoidable demerits. The cause of one of its demerits, that is staircase effect, is due to a fixed build direction. Additive non-layer manufacturing (ANLM) processes such as CLIP, 2PP and CNC accumulation do not have a fixed build direction, and these processes are therefore free from such demerit. These processes thus show a promising route to fabricate an AM part free from any inaccuracy arising due to staircase effect. This chapter describes disadvantages of additive layer manufacturing processes and analyzes various ANLM processes.

Sanjay Kumar

Chapter 11. Sheet Based Process

Abstract

Sheet based process uses machining but is generally dealt in the realm of additive manufacturing (AM). It brings a question whether sheet based process is an AM and if it is not an AM then whether it is hybrid AM. It could be easy to know whether it is AM, but it could not be so easy to know whether it is hybrid AM because there exists no criteria and definition for hybrid AM. This chapter applies the concept of hybrid manufacturing to sheet based process to check whether it is hybrid AM. Various sheet based processes such as ultrasonic consolidation, laminated object manufacturing and friction stir AM are briefly explained.

Sanjay Kumar

Chapter 12. Future Additive Manufacturing Processes

Abstract

Existing additive manufacturing (AM) processes need to be developed in order to demonstrate their potential for product fabrication. There is some scope for development of powder bed fusion by incorporating extra deposition tracks and extra powder hoppers which is given. Incorporating extra nozzle in laser solid deposition process will help make complex products – this is explained. Existing AM processes are not capable to utilize all available resources for product development, classification of AM processes suggests the development of new AM processes that will utilize untapped resources in new way. These new processes could be particle bed process, non-photopolymer bed process and sheet bed process which are given.

Sanjay Kumar

Backmatter