10 Principles of 3D Printing

3D printed bionic ear
image via American Chemical Society publications

Last week I attended an event, “From Trinkets to Body Parts: 3D Printing – Transforming Sci-Fi Fantasy Into Reality” sponsored by the Seattle MIT Enterprise Forum. The keynote speaker was Hod Lipson, PhD, Professor of Engineering at Cornell University. Prof. Lipson gave an informative and entertaining talk centered around his 10 principles of 3D printing.

There was also a panel of 3D printing industry experts and lots of Q&A with the large audience. It seems that there is much interest in 3D printing – a not-so-new technology whose time has come?

Prof. Lipson identified 10 key principles of 3D printing in his talk:

  1. Complexity is free
  2. Variety is free
  3. No assembly required
  4. Zero lead time
  5. Zero constraints
  6. Zero skill manufacturing
  7. Compact, portable manufacturing
  8. Less waste by-product
  9. Infinite shades of materials
  10. Precise repeatability

Here is my take on the 10 principles:

1. It’s as easy to 3D print a complicated piece as it is to 3D print a simple piece.
2. Every piece that you print can be different without increasing cost or cycle time.
3. The assembly process can be part of the printing process, e.g., a bicycle chain has been 3D printed.
4. Because there is no tooling and no setup, the only lead time is the time required to start the printer and send the digital file.
5. You can fabricate things using 3D printing that could not be made any other way.
6. Since there are no precision assembly tasks, printer operators do not require specialized skills.
7. 3D printers are relatively small, portable, and inexpensive compared to injection molding machines, milling machines, punch presses, and foundries.
8. The 3D printing process does not generate waste material. Neither does modern injection molding, but processes that remove material such as milling do generate considerable waste.
9. Not only can you combine colors in infinite shades, but you can combine materials to create unique mechanical properties.
10. Within the tolerance limits of the printer (0.1 mm for commercial grade printers), every piece printed is exactly like every other piece printed.

Prof. Lipson is also the author of a new book, Fabricated: the New World of 3D Printing.

There are drawbacks and limitations to 3D printing, of course. High volume production is better suited economically for injection molding. Surface finish can be rough, requiring secondary processing, although efforts are ongoing to improve surface finish and textures. Pieces may not have isotropic physical and mechanical properties.

Prof. Lipson identified an incredible range of materials that have been used as the raw material in 3D printing: plastic, of course, sand, concrete, various types of food, paper, steel and other metals, and even living cells.

Some products that have been 3D printed: a working gun, clothing, shoes, furniture, aircraft parts, artwork, food (might be what astronauts eat on their way to Mars and beyond), a working loudspeaker, batteries and electrical circuits, and body parts.

And here are some examples of 3D printing in healthcare and medical devices. Some are in research, some in active development, and others are commercially available:

  • Invisalign braces – custom made for each patient
  • Knee meniscus
  • Heart valve
  • Ear prosthetic
  • Organs – liver, kidney, heart

3D printing of human body parts and organs is also called “bioprinting” in this 2013 New York Times article, “At the Printer, Living Tissue”. The article is pessimistic about near term prospects for 3D printed organs, although it notes that there is much research and development being conducted. Others in technology think that breakthroughs are imminent: Functional 3D Printed Organs by 2014 > ENGINEERING.com. There is a startup bioprinting company, Organovo, developing an artificial liver. The liver in its first incarnation will be suitable for drug development and testing, not for human implantation. A research team at Princeton created a functional 3D printed ear, again, not suitable for implantation: Researchers create world’s first 3D-printed bionic organ | ExtremeTech.

Takeaways: 3D printing is becoming widely known and commercially acceptable. In the medical field, it can be used for rapid prototyping and even for fabrication of low volume production parts. As the “10 principles” indicate, you can save time and money in your medical device development projects by using 3D printing.