Limitations of 3D Printing

By Yap Shiwen

Continued from Introduction to 3D printing.

For all the benefits and effects that come about from 3D printing, there is immense hype surrounding the technology and the industry, driven in part by the inflow of investment capital that surrounds any new phenomena. And this hype can distort awareness of the technology, its potential and its capabilities.

There are very real limits to what a 3D printer can currently do, in terms of both materials, designs and capabilities. For example, tissue engineering and food production are very real possibilities with 3D printing, but they won’t be entering the market anytime within the next year. 3d printing is still evolving and has a host of issues that will need to be resolved, IP protection and regulations among them.

Affordable and hobbyist-friendly manufacturing tools that convert polygons into physical objects, via the STL (STereoLithography) format, have been available and were present on the market before the rise of the 3D printing wave.

Desktop CNC mills – a machine tool that uses programs to automatically execute a series of machining operations – are a case in point, with applications at home or in the office and costing approximately the same as a 3D printer, with particular applications for jewelers, dentists, mechanics and steelworking hobbyists. Beyond a small community of hobbyists and specialist firms and contractors catering to niche businesses, these have not enabled or promoted on-demand manufacturing from home workshops.

Anyone can download a 3D renderer free from the Internet, with many open-source options available, such as OpenCAD, one among many. However, creating and rendering 3D design requires hundreds, if not thousands of man-hours in order to develop competency in. It requires persistence and discipline to develop the necessary skill. The following points limiting 3D printing were raised in an issue of Makezine:

• CAD is DIFFICULT. It takes hundreds to thousands of hours of training in order to learn and develop competency, let alone mastery, in CAD applications. You will require skill in using the 2D input device on a 2D screen to sketch out highly complex 3D shapes and intricate designs

• Industrial Design Matters. Most people, if given a hypothetical 3D printer that makes flawless parts out of any metal of choice, cannot produce a working nail clipper or scissors. Industrial designers spend years studying the design, potential applications and practical trade-offs of items ranging from spur gears to hundreds of diverse types of linkages, hinges, joints or cams. As an example, there are 4 sophisticated design decisions involved in designing and making a box of Tic-Tacs by a design team.

• Mechanical Engineering is Real Science. Plastics and metals are imperfect materials; there are trade-offs in balancing attributes of durability, practicality and aesthetics simultaneously – one has to give way to the other 2. Flat sheets of these materials are fragile, ductile and easily distorted. Trivial objects like phone cases and Lego bricks make use of carefully placed ribs, gussets, and bosses to prevent the parts from deforming, distorting or disintegrating. Basic engineering principles take time to master and properly apply in these products.

• Manufacturing Processes = Imperfect. Part design needs to account for manufacturing tolerances, material shrinkage, millimetre margins, minimum feature sizes, the need to support the part through the process via scaffolding and so on. This creates complications. Very few advanced designs can be rapidly sketched and disseminated without accounting for these physical factors, adjusting them for the general manufacturing method, and finally, for the specific model of the machine used to make the part.

Significant technical expertise goes into developing and making 3D printers, as well as the designs available to people online. There are still imperfections in the processes and they will be overcome, but there are limitations to what 3D printers can achieve. Casual users have to be able to overcome the barrier of the knowledge deficit, which imposes a limit to extensive use of 3D printers casually.

The existing hobbyist-friendly additive prototyping methods tend to produce parts from a very narrow choice of materials, all of which exhibit fairly poor mechanical characteristics; there are no signs that this will change in the coming years. With CNC mills, the situation is much better – but some of the essential materials remain difficult or expensive to process (for example, most rubbers don’t machine particularly well).

Material limitations are another concern. Currently, 3D printers are optimised to use a single material, usually a plastic. Most objects are made from multiple materials. An inability to print electronic circuits and their casings together is a major drawback.

There are many objects, such as firearms, that you could make with a 3D printer, but shouldn’t or wouldn’t—and not just because of legal issues. Gun mechanisms aren’t easily produced by 3D printers and will be sub-par due to the material and construction limitations. This extends to other products as well. Capability does not indicate intent.

3D printing as it currently is will not be changing manufacturing but will complement it. It serves as as way to customise designs and enhances the design work process and prototyping process, but does not fundamentally affect manufacturing workflows. While further development of the technology can change that, this is yet to be seen.

Most overhype of 3D printing comes from misunderstanding what a 3D printer is. Different machines do different things, with different goals and materials in mind, whether it is printing key chains and phone casings or printing out blood vessels and organs. And these are evolving separately. The fact that a single expensive, highly specialised machine can print bicycles from nylon or carbon fiber filament does not mean all printers can do this.

3D printers are popularly perceived as tools enabling users to directly manufacture virtually any product. This belief is misguided. Both 3D printing and CNC machining processes tend to be more useful in producing tooling patterns – shapes that serve as input to more specialized manufacturing processes. Rather than a standalone fabricator platform, they serve as part of a manufacturing workflow in manufacturing a larger object.