3D printed part that would be (extremely) difficult to make another way. Photo credit: Axel Hindemith Lizenz: Creative Commons CC-by-sa-3.0 de

This is in part motivated by Jon Evan’s recent article on TechCrunch (http://techcrunch.com/2012/11/03/one-of-these-things-is-not-like-the-other/) but more to add to the discussion of new manufacturing technologies from my experiences that have been brewing for a while.  I agree with Evan’s thesis that 3D printing is alike 2D printing only in name, but my experience is that 3D printing are a great tool, but will not be a total revolution in manufacturing as some suggest.

I am starting a PhD in Mechanical Engineering soon and have been using 3D printers, waterjet machines, and laser micromachines for three or four years now on a prototyping basis.  I am writing this mainly directed for the software tech crowd that has recently become more interested in hardware.  Some of my conclusions:

1. We will not see 3D printers in everyone’s home

I don’t see 3D printing as being a new fixture in everyone’s home.  This is because 3D printing:

1. requires design input, which requires developed skill and time
2. is a slow process, and
3. materials are (currently) poor quality from an engineering perspective

I do see growth in residential use, but only by the same kinds of people who have a wood working shop and welder in their garage, or who do I/O software or robotics projects. They are a nice cross-over between software and hardware.

3D printing needs design input, and for more than the most trivial parts, this requires computer aided design software and the skill to use it.  It’s far more work than most people are willing to invest.  If you are just going to make parts of other people’s designs, why not just outsource the production to them as well?

3D printing is slow, with even small parts taking hours to make.  Unless it’s a custom part (that you’ve designed yourself), its much quicker (and cheaper) to find something off the shelf.

3D printing materials are apparently better than they used to be, but I still find they crack often and easier than would be acceptable in most uses.  Yes, there are examples of parts that are made by 3D printing that work fine for their use, but a molded, casted, or machined part will be stronger.

2. 3D printing will not revolutionize manufacturing

For the same reasons listed above, 3D printing is not a great production technology.  But, more importantly, the economies of 3D printing are only efficient below about 10-20 parts.  After that, casting or injection molding is typically cheaper, except in a few cases I will discuss later.  At large volumes, the per-unit cost of a plastic part in injection molding could be well under a dollar, and the same part in 3D printing could be over $100.  The exception is where 3D printing is making a part that is “impossible” by other methods or that would require multiple parts and assembly.

 3. 3D printing is good for prototyping and one-offs (but not the only way)

For doing something once, whether for prototyping or if you only need one, 3D printers can be a great tool.  One cool application is surgical planning or even custom implants by 3D printing (such as http://www.bbc.co.uk/news/technology-16907104).  And it makes sense because everyone is different enough to justify and one-off part for them (and medical device costs are high enough to allow it).  But replace overseas injection-molded parts with a 3D printer in your garage?  It doesn’t make sense in nearly all instances.

There are other rapid prototyping methods such as CNC waterjet cutting and laser machining that get less attention although they are, in my opinion, more useful prototyping tools.  Typically, sheet metal is cut, then folded into a 3D prototype.  These are nice because they are typically stronger than 3D printed part, are quicker, and time scales with complexity rather than size. There are also many types of 3D printers including those that “print” rubber-like materials, hard plastics, and metals.

New rapid prototyping methods are game-changing for developing new products on a shoe-string budget, and I would wager that most of the recent success stories on Kickstarter (www.kickstarter.com) were developed with the help of 3D printing prototypes.  In this, the technology really does allow for cheap innovation where design is the major innovation.  I would go as far as to say these technologies are lowering the barrier-to-entry of hardware projects to a similar level as software, at least until the product goes to production.  Great news for hardware entrepreneurs!

As an aside on Kickstarter since I brought it up, it is interesting they recently banned virtual renderings of design projects.  Rapid prototyping allows for moving from virtual models to prototyped models easily, quickly, and cheaply.  The problem is that the prototypes in no way prove the company is ready to handle the demands of transitioning into production, or that the prototype has had any reliability testing.

4. 3D printers allow for making things that are impossible any other way

This is probably the second biggest advantage of 3D printers, after their usefulness in rapid prototyping.  3D printing allows for making shapes that are impossible using other methods, or require multiple parts and assembly in other methods.  3D printing in particular allows for printing parts that have irregular voids or holes that curve are very difficult to make with other methods.  Mechanical Engineering Magazine (http://memagazine.asme.org/) has had a few good articles on this over the past year, or the image I posted above is a good example.

5. 3D printing (and other rapid prototyping) machines are less reliable

3D printing and other automated machines, especially lower end ones, continue to have reliability issues.  Most of my experience is with industrial machines (costing in the $50-100k range), and even these have a crippling amount of downtime.  There are also issues that occur while parts are being built.  At best, you catch these early and can restart the part.  At worst, you come back later to find you part is a mess and the machine is damaged.  These machines typically don’t have feedback, so the machine can’t tell if its made a mistake.  Good ol’ lathes and mills, even of the CNC variety, are much more reliable.  But rapid prototype machines may improve in the future.

 6. 3D printing users need to decide between ownership and out-sourced services

3D printing machines are becoming less expensive, but still lock up a lot of capital.  For most users, their machine is probably going to spend most of its time waiting for a job, and only a fraction actually printing.  I have used a few services, my favorite is Protogenic by Spectrum Plastics (http://www.spectrumplasticsgroup.com/protogenic).  I have found they have the best prices and have the best customer service of any vendor I’ve ever worked with.  Typically a part is delivered within 5 business days of ordering, and prices aren’t that much more than the material used in your own machine.  Therefore, the only reasons I can see for ownership of a 3D printer are:

1. High usage
2. Need for extremely quick turnaround times
3. Desire for confidentiality (although most venders will agree to NDAs)
4. Teaching CNC control theory (ie in engineering schools)
5. To geek out

For most reading this article, this last point may be the main selling point for getting a 3D printer.  They are certainly fun and interesting toys.  And they do have niche roles in manufacturing, design, and maker culture.  But it’s time for a reality check: 3D printing is not the beginning of the end for injection molding, milling, casting, and other traditional manufacturing technologies.

Edit: there has been a vibrant discussion of this on HackerNews.  Thank you all for your thoughts and comments: http://news.ycombinator.com/item?id=4751489