Key Takeaway Points

i. The sequence of operations associated with AM metal processing is differentiated from other metal processing operations that require manual intervention or constant supervision. Many AM metal processes can take hours to build a part but require expert oversight to assure the process is properly set up, the safety envelope is verified, and the procedure is followed.

ii. Post-processing operations, inspection, and quality assurance rely primarily on the modification of existing inspection methods to assure a repeat- able process, allowable levels of flaws, and a component that meets quality standards. The size, distribution, nature, and origin of AM metal defects in some cases challenge existing NDE methods.

iii. Standards are being developed to assist in the certification of critical components and are needed to fully realize the adoption of AM metal processing in wide-scale industrial production.

Overview of 4D Printing

Additive manufacturing (3D printing) is itself an emerging technology and is in fact over thirty years old already. As SPI Lasers has continuously reported, the technology is now becoming more mainstream, but is still very heavily underutilized considering its potential. The potential to economically and time efficiently 3D print ANYTHING is an irresistible proposition. 3D-printed materials are not the end of the story though, as there are techniques to create materials/objects which can be pre-programmed to operate in a certain way.

A Definition of 4D Printing

The term 4D printing was first coined by TED professor Skylar Tibbits in his February 2013 speech at the MIT Conference.

A definition of 4D printing may be:

The use of a 3D printer in the creation of objects which changes or alters their shape when they are removed from the 3D printer. The objective is that objects are made to self-assemble when exposed to air, heat, or water; this is caused by a chemical reaction due to the materials utilized in the manufacturing process.

The Difference between 4D and 3D Printing

Think of 4D printing as the same as 3D printing with the addition of time. By adding time to 3D printing, the concept of 4D printing is born. This enables objects to be pre-programmed in various ways to react to a range of different stimuli.

4D printing is futuristic but has a very exciting future. 4D printing delivers the possibility of designing any transformable shape, which can be made from a large selection of materials. These different materials will have many different properties and a range of potential applications and uses. There is a real opportunity for the creation of dynamic self-assembling objects which could transform and be used in a wide range of industries and in a large number of applications.

Potential Applications for 4D Printing

Applications of 4D printing are particularly suited to changes in environmental circumstances:

Architecture: Buildings which are delivered in a flat pack form but entirely self-assemble when the right stimuli are added.

Clothing: Clothes and footwear which change the appearance and function (e.g. clothes which naturally adapt/change to the size/contours of the wearer).

  • a) An example is shoes which become waterproof during rain or react to other external atmospheric conditions
  • b) Military clothing, e.g. clothes which camouflage, cool, and/or insulate soldiers by reacting to different input environments

Food: The 4D printing of food using a number of techniques.

Health: Multiple applications including nanotechnology uses:

  • a) There is the possibility of inserting implants into the human body, which self-deform to a plan when inserted with surgical intervention (e.g. cardiac tubes)
  • b) Using 3D printers injected with stem cells to print slices of liver and other organs
  • c) Using 3D printers to print skin, the shape of which changes over time depending on conditions

Home appliances: Products in the home, such as a chair which upon purchase self-assembles through heat stimuli applied by a home hairdryer.

Transport: Roads which self-heal potholes.


  • 1. Briefly explain post-processing and finishing.
  • 2. Discuss nondestructive test methods.
  • 3. Discuss destructive test methods.
  • 4. Explain standards and certification.

Multiple-Choice Questions

  • 1. PBF-EB uses a powder bed preheat of up to_.
  • a) 600°C
  • b) 700°C
  • c) 800°C
  • d) 900°C Ans: (b)
  • 2. HT furnaces used to treat metal parts may need to operate at_

and use inert atmospheres, such as argon or vacuum, when processing certain materials.

  • a) High temperatures
  • b) Moderate temperatures
  • c) Low temperatures
  • d) None of the above Ans: (a)
  • 3. HIP is a process that uses high temperatures and high gas over pressures to

heat a part to a temperature below melting and at pressures of_.

  • a) 80 MPa
  • b) 90 MPa
  • c) 100 MPa
  • d) 110 MPa Ans: (c)
  • 4. _inspection may or may not detect lack of fusion defects as

poorly bonding locations may not be detected.

  • a) Radiographic
  • b) Heat treatment
  • c) Fractography
  • d) All of the above Ans: (a)
  • 5. Ultrasonic testing (UT) uses_sound waves to penetrate a metal


  • a) Subsonic
  • b) Sonic
  • c) Supersonic
  • d) Ultrasonic Ans: (d)
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