3D Printing, Rapid Prototyping, Additive Manufacturing? What is the Difference?

imageThe technology called 3D Printing is getting a lot of press lately. Articles like “3D Printing is the New Personal Computer” and “The New MakerBot Replicator Might Just Change Your World” are all over this place in the fall of 2012.  For those of us who have been printing 3D parts since the early 1990’s, this new frenzy can be a imagebit annoying. At every trade show that PADT goes to these days a large number of non-technical people come up and start telling us about 3D Printing and how it is going to “change everything.”  The next question is almost always “Is that a big 3D Printer?” as they point at a nice big FORTUS 400.  “Well, no, that is a digital manufacturing center, which is a rapid prototyping technology that uses similar technology to 3D Printing but it is much more precise, the material…” and by that point their eyes glaze over and they start playing with the model of the USS Enterprise we put out on the table to attract people.

By sorting through branding, media hype, and the confusing array of new low cost technologies, some clarity can be found and direction for those of us who use these technologies for product development. 

Additive Manufacturing

The first place to start is to recognize that we are talking about additive manufacturing technologies.  Taking a part definition and adding material through a variety of methods to make a physical part.  In almost every case, you build a part by adding thin layers of material one on top of another. The additive process differentiates this type of manufacturing from molding, forming, and machining – all of which remove or shape material.

The advantage of additive manufacturing is that you have very few constraints on the shape of your final part and there is no tooling, no programming, and very little manual interaction with the process.  This has huge advantages over the traditional manufacturing methods when it comes to speed.  Although you pay a price in strength, material selection, and surface finish, you can get parts quickly without a lot of effort.

Rapid Prototyping

Additive manufacturing took off in the late 80’s because it allowed engineers to make prototypes of their parts quickly and easily.  Rapidly.  And that is why for almost twenty years, most people who use additive manufacturing refer to it as rapid prototyping.  And to this day, most of the users of additive manufacturing use it for making prototypes as part of their product development process.  RP sounds better than AM, and better describes what you use the technology for rather than the technology. So that name took off and has stuck.

Other Names, Other Uses

As the technology got better, and especially as the materials got better, people started using additive manufacturing for other uses beyond making prototypes.  And, as is the way of companies that are trying to sell stuff, the manufacturers starting coining new names for the applications as users come up with them:

  • Rapid Patterns: making a part that will be used as a pattern in a downstream manufacturing process.  This is very common with jewelry in that the pattern is used in a lost-wax process for casting.  It is also used a lot with soft tooling, where the pattern is used to make a negative mold out of a soft rubber material.
  • Rapid Tooling: Making fixtures and molds using additive manufacturing. Tools can be used as patterns for forming, patterns for casting, or even for making molds for injection molding.
  • Direct Digital Manufacturing:  This is one of my favorite names and abbreviations – DDM.  The difference here is that the additive manufacturing process is used to make a final product, not just a prototype. 
  • Rapid Manufacturing: The same as Direct Digital Manufacturing, but without the alliteration.

3D Printing

According to Wikipedia the term 3D Printing was invented at MIT in 1995 when someone used an inkjet printing head to “print” a binder on to a bed of powder.  They used a printer to do their additive manufacturing, and used the term 3D Printing to describe it. By the way, they went on to form ZCorp, the second most popular additive manufacturing process in the world. 

Even though it started being used to refer to an inkjet printing based approach, the name spread over time. The term really caught on because it is so descriptive. Additive Manufacturing, and even Rapid Prototyping, do not make a lot of sense to non-engineers. 3D Printing makes sense immediately to pretty much anyone.

Those of us who are diehards really want 3D Printing to refer to lower cost, affordable devices that make lower end prototypes.  And if you look at how the name is applied by the manufacturers, that is generally how it was used.  Here is a screen shot of the Stratasys home page, and see how they split their systems into 3D Printers and 3D Production systems:


But the name is working so well that we are seeing a shift towards refereeing to additive manufacturing as printing.  3DSystems is going full bore and as of this writing, refers to their whole line as “Printers” and differentiates them by calling them “personal, professional, and production.”


What is Old is New Again

So it looks like the trend is towards 3D Printing becoming the new term for an old technology. And those of us who call them RP machines will have to stop doing that, or just accept that we will be met with blank stares when we do.  So next time someone comes up to tell me they just read an article in Good Housekeeping about how they will be able to make replacement parts for their dish washer in the garage with a 3D Printer, I will smile and say “That is great. In fact, we use almost all of the major 3D Printing technologies in house at PADT, and we resell the most popular 3D Printers from Stratasys, Inc.  That includes that big FORTUS 900.  It is a big and accurate 3D Printer”