3D printing has long been used for prototyping. Although CAD models are very good, often it is not very clear how well a prototype device works until you have a physical model. Whether a 3D printed model is really needed or just a cool thing to have depends on the circumstances. In Chapter 1, we talked about when to use a 3D printer vs. other technologies (or just cardboard and duct tape). How accurate and how functional your model needs to be should drive your choice of technology.
People often ask why a prototype on a screen is not good enough. For many things, it might be, but it is challenging to imagine how a consumer product will feel in your hand or to explain how different parts of a landscape will fit together. Architects usually build models of their projects so that people can see how the parts fit into each other and into the scenery around it, but now they can use 3D prints instead of foam board. Unless the 3D print requires a lot of post-processing or is large and time-consuming to reprint, it is likely to be easier to change a 3D print than a hand-sculpted model.
Prototyping
One thing to consider when creating a prototype is the level of detail required and the budget. If both the fidelity can be low and money is tight, you should probably just use some cardboard and duct tape. If the accuracy needs to be higher than that, a filament-based print is a good next step. Finally, a resin or powder print and some post-processing might to be in order if the model needs to have fine detail and look like the real thing.
Another reason to create a prototype that can be 3D printed is that it makes it easy for remote collaborators to have their own copies. Instead of shipping around fragile and expensive models, everyone can print one locally. A model can be iterated internally on a $200 filament printer using cheap PLA. Once form and fit are settled, a final version can be printed in another material, painted, and so on. Or for that matter, the CAD file can go on to be fabricated using a different technology altogether.
As we discussed in Chapter 10 about short-run manufacturing, many common injection-molding plastics now are available as filaments. It may be possible to 3D print a functional prototype or a small production run using an in-house 3D printer. The one thing to be cautious of though is that the mechanical properties of an injection-molded and 3D printed part will be different. Even though they are of the same plastic, the 3D print will be stronger within than across layers, but the injection-molded one should have the same properties in all directions. Some printing technologies, like resin printing, produce more isotropic parts than filament printing. The increasing variety of 3D printable materials makes it more likely that the feel of a prototype can also be close to the final product.
Science and Math Modeling
3D printing can create a model of something that is inherently 3D, but perhaps not readily available at human scale—a single molecule, for instance. Figure 12-1 shows a 3D model of an ice molecule from our 2016 Apress book, 3D Printed Science Projects. The model creates one water molecule which you then have to assemble into ice crystals.
Ice crystal model (model from 3D Printed Science Projects)
A first question to ask is whether the model you are considering creating really is inherently three-dimensional. We have seen people make flat 3D printed versions of diagrams. You can do that, but why? Even for the visually impaired community where that might make sense, there are faster and cheaper solutions for that sort of thing, like swell paper. For example, 3D printing an essentially 2D periodic table without adding any insights does not make a lot of sense, but for some reason it is one of the first things people think of creating. On the other hand, adding another feature to the table for the third dimension might be interesting, like ones on www.thingiverse.com that use the third axis to show how properties of the elements like reactivity and density vary.
If a concept is abstract and naturally three-dimensional, as long as the relationships among the axes are correct and line up with the math, or physics, or what-have-you being described, a model can bring a lot of insight. Figuring out how to create the model is a learning experience, too, as you (or your students) wrestle with how to have the model’s geometry show the concept you have in mind.
As we discussed in Chapter 13, a free program exists to 3D print terrain (although the software noted there is limited to a resolution of a few city blocks). This makes it possible to create very accurate models of watersheds or wetlands for urban planning or public information purposes.
Mathematicians have always created models for their own use and to teach students. However, the ability to have a 3D printer on your desk or in your department can be a game changer. Many mathematical modeling programs will directly export a 3D printable file. The challenge can be the complexity of the print and possibly extracting support from very intricate models.
Medical Visualization
3D prints are increasingly being used for planning surgeries. Full-color models of a patient’s anatomy can be created based on CAT scans or other imaging data. At the high end, multicolor resin prints (including clear or translucent parts to show relative position of the skull) can be created for complex surgeries like brain tumor removals.
SLA anatomical model (image courtesy of 3D Systems)
Visualization Best Practices
Making a 3D model is harder than it looks. Most textbooks have more or less the same 2D projection of 3D objects, and you may have to do a surprising amount of research to get the 3D form factor. If you want your model to come apart in a way that reflects the real system, you will find you need to research the physics or chemistry or anatomy in question thoroughly.
There are no hard and fast rules for this. Blind users of our models from our Apress 3D Printed Science Projects books have taught us that tactile models need to tell a story, and there needs to be an obvious and unambiguous beginning point for exploration of a model. A good test of this quality is to imagine how you might explain the model to someone blind. If they pick up the model and have a written explanation of what the model is, will they know where to start their tactile exploration and what the important features are?
We have found that thinking about making the models accessible to tactile-only users leads to designs that are good for all users, visually impaired or not. The broader name for this way of thinking is Universal Design, if you want to search on the term for more inspiration.
Similarly, there is often a temptation to add a lot of detail to a model to show off your 3D printing skills. However, this can make a model overly complicated and fragile and even can hide some of the simple elegance of many science and math concepts. This is a tactile equivalent of using ten fonts and sound effects on a PowerPoint slide; you can do it, but your message will be lost in the racket such techniques create.
Consider how to make your model as simple as possible rather than trying to have as much information shown as possible. Our blind friends, for example, did not like Braille labels on their models since they are hard to distinguish from physical features. Make sure your model has a point that it is making, and design the minimal form that gets that point across.
When we develop models for publication that we intend others to be able to print, we try to make them easy to print. For example, we avoid support and small features if at all possible. We also assume that many users will have poorly tuned printers and so do not publish models that are a 3D printed tour de force.
Summary and Questions for Review
In this chapter, we discussed the use of 3D prints for visualization, either as a form and fit prototype, or to help students or professionals think about a system in 3D. We also discussed that less can be more when designing a physical model of a concept and that there is a lot to be gained by thinking about what story the model will be telling its users.
- 1.
You are creating a model of a museum building’s exterior that will be about four inches on a side to use in a fundraising display. Describe what details you would feel are necessary to include and why.
- 2.
Imagine a 3D printed model of a human blood cell. What are a few key features you would include? How would you describe what the model is showing to a blind person? Where would you start and then how would you guide an exploration from there?
- 3.
What are two or three principles to keep in mind when you design a 3D printed prototype that will make the transition to production as seamless as possible?