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How To Make A 3D Printed Architecture Model

Picture of Mikkel Kring
by Mikkel Kring
Apr 24, 2017

3D printing architecture models offer a lot of advantages – but you do have to consider some things first. Here‘s what you need to know of you want to 3D print architectural models. 

3D printing has been one of the most talked about technologies this decade. Some consider it the beginning of the third industrial revolution. Others have even compared it to the invention of computers, predicting that these machines could have a similar impact.

For architects, the technology could not have come sooner. 3D printed designs have been a godsend for the industry, allowing engineers to quickly and cost-effectively create scale models of complex structures.

Amazingly, there have also been full structures built using the technology. In the Netherlands, the first 3D printed house was recently completed. We’ve had the same success in China where engineers have managed to build houses using 3D printed materials. Just recently, the first 3D printed bridge was erected in Spain.

Here’s a picture of the recently completed 3D printed bridge in Spain:

In this guide though, we want give serious thought to the 3D printed architecture models only. While all the big building and stylish bridges printed using 3D technology in different parts of the world are a marvelous sight, the main impact of 3D printed in the industry has been in model production.

Architectural models are some of the most complex products. Creating even a relatively simple model can take many weeks and typically costs hundreds, in special cases even thousands of dollars.

But not with 3D printing. This technology has completely revolutionized the architectural modeling process. And not just in terms of price. Even timing has improved. Models that would have in the past taken days to create can now be completed in hours.

That’s not all. 3D printing has benefited architectural modelers in three other ways:

1. Seamless Integration: Most architectural firms already use CAD applications and have in-house design teams. This means that a firm bringing in a 3D printer doesn’t need to change anything. You just connect the printer to your computer to start making 3D printed architecture models. If you don’t own a 3D printer, you can have your model printed by a professional 3D printing service.

2. Added Design Possibilities: 3D printers allow architects to design freely without worrying about human errors. This usually results in highly accurate models. With this freedom, you can push your boundaries of design and try new possibilities because you can quickly, accurately, and cost-effectively render test models.

3. Better Perspective: Lastly, and perhaps most importantly, no amount of drawings, blueprints, or digital 3D models can replicate the “real-life” perspective that you get with 3D printed architectural scale models.

Revising models can be difficult. But not when you have the 3D printer. These printers allow you to tweak your design and re-print the new design in minutes. This often results in immaculate accuracy both with the models and when constructing structures out there in the real world.

1. Getting Started: Planning for the Modeling Process

Before we look at how to create quality models using the technology, let’s first discuss how you can plan for the process.

Creating 3D printed architectural models is a complex process that demands high levels of concentration. You must master the techniques. Otherwise, you may never create useful models. Nevertheless, we’ll try to keep things as simple as possible.

It Starts With 3D Thinking

Before you start printing anything, take a moment to think about what you’d like to print. The ability to think in 3D is your greatest asset. Most designers are so used to 2D designs that whatever we think of these days is in two dimensions.

You have to stop that and start projecting your ideas in 3D. Those elevations that can be impossible to create on a 2D plane will no longer be a problem. In 3D printing, you’ll be able to instantaneously comprehend them simply by rotating the object as if it were in your hand.

Understand the Different 3D Modeling Software

To help with the modeling, you’ll need 3D modeling software. These software applications can be used to create 3D models from scratch, of you can use them to reconstruct your 2D model into a 3D model.

There are multiple 3D modeling software products in the market and your selection should be based on your needs. What types of 3D models do you want to create? Fully investigate the features of each software to determine what is best for you.

Remember that cost can also be a major factor. Different 3D modeling software are priced differently. Choose one within your budget. You will also need to factor in the hardware requirements of the software you choose – some programs will require a dedicated workstation desktop or high-end laptop while the more basic apps will require at the very least a dedicated GPU with at least 1GB of dedicated video memory. Most popular gaming-oriented PCs should fit the bill. A clever way of gaining access to the premium software packages when you’re on a low budget is to go with a trial version to start off.

Some popular 3D printing and modeling software tools to consider include:

Most of these software packages have the ability to import 2D geometry files for 3D modeling. However, each software can only support certain 2D files. So make sure the software you choose will support the 2D files you use. You can also browse more 3D printing specific software packages here.

Decide On a Scale And Print Size for Your 3D Model

Just like with 2D applications, it’s important to spend the early days thinking about the scale you want to construct in. Of course, the simplest model is the 1:1 where you can use your knowledge of common sizes for windows, doors, ceiling heights, and so on.

As long as you can plan ahead and keep your scale factor and smallest printable feature (SPF) in mind, we also recommend this scale.

Understand that 3D Models Come in Shells

It doesn’t matter which CAD or 3D modeling application you choose, creating a 3D architecture model will produce what are called shells. Shells, also known as nodes, are simply components or parts. They are what make up the glorified final model.

For instance, a normal door usually has the main frame, pane, door knobs, and so on. These are what are called shells. Windows have their shells too, the frame, lock, pane, etc. and, when talking about a building, its shells include the wall, ceiling, roof, windows, doors, walls, staircases, railing posts, and so on.

A single architecture model can comprise dozens, hundreds, or even thousands of shells. This number sometimes depends on the architecture. Since no two architects are the same, you may want to include certain shells in your model that a different architect may not care for. The bottom line is that you must be aware of all your shells. Know what is needed and know where each piece goes.

2. Getting You Feet Wet: Creating 3D Printable Architectural Models

To successfully create 3D printed architectural models you’ll be covering several topics. We’ll look at each of the topics in detail shortly. But here is a summary of the list:

  1. Creating watertight, solid shells
  2. Eliminating holes
  3. Geometry topology and polygon/facet count
  4. Inverted normals
  5. Coplanar (overlapping) surfaces
  6. Floating shells
  7. Smallest Printable Feature (SPF)
  8. Strength and support
  9. Hollowing a model
  10. Removing unnecessary geometry

1. Creating Watertight, Solid Shells

In 3D printing, best results are only achievable if you feed the printer with watertight, solid geometry. It doesn’t matter whether you’re using 2D drawings, mesh modeling techniques, splines, or a dedicated 3D modeling application. The shells must be watertight.

Let’s use a demonstration to understand what watertight, solid shells are.

Take an example of a six-sided cube. For the cube to be called watertight and solid, all the six sides must be modeled. If you only have five sides, that cube is neither watertight nor solid. Such a model is said to be an open shell with a hole. Any geometry that has holes or gaps in it cannot print correctly.

The same applies to flat open surfaces with zero thickness. If these surfaces are not thickened to make them solid and watertight, they cannot be printed correctly.

So, how do you remove the holes and gaps in your input?

2. Removing Gaps and Holes

A common mistake modelers make with 3D files is failing to comply with the vertex-to-vertex rule. The rule states that all adjacent triangles share two common vertices. When you fail to comply with this rule, you may end up with holes or gaps in your file.

You can attempt to repair such errors with various computer applications. However, you should also know how to repair the errors manually. One manual option is to delete the three triangles/ polygons (below left) where the error is occurring and fill the hole. This is also known as capping.

Alternatively, you can combine the two smaller triangles/polygons to form just one large triangle. You’d end up with two same sized triangles/polygons. If you choose to go this route, remember to delete any floating unused points. These unused, floating points can themselves cause gap errors.

The third option is to delete the bigger triangle/polygon and construct two new polygons/ triangles similar the remaining once. You’ll end up with something that looks like this:

Other than vertex-to-vertex issues, holes or gaps in 3D files can also result from the conversion process i.e. when converting or translating your file from one format to another. This is because the conversion process often results in missing or distorted geometry that can in turn cause holes or gaps.

Sometimes, the amount of missing or distorted, or even overlapping geometry can be extreme that repair becomes a problem. Since you usually have to manually identify the holes before attempting to fix them, it may just be impossible to work on all the errors.

Again, certain editing software can be used to attempt to repair the model, but only on a surface by surface basis. That’s where having a lot of shells can help. When you have more shells, you can just repair one shell after another and if one is damaged beyond repair, create a replacement. But if you have only a few shells, then repairing a damaged shell might be very difficult. There are also disadvantages of having a lot of shells as you’ll learn later on.

3. Geometry Topology and Polygon/Facet Count

Another factor you need to pay keen attention to if you want to successfully produce quality 3D printable models is your geometry topology and overall polygon count. Ideally, the geometry should be clean and the polygon count low.

Going back to our six-sided cube, that’s one of the perfect models you can have for 3D printing. It has six, four-point polygons/surfaces which are perfect for printing. When you convert such a file into VRML, for example, you’ll get 12 triangles which are just the original six squares each sliced into half. Twelve is still a low enough count.

But if you subdivide each of the six surfaces into several smaller squares, you will still maintain the cube geometry, but you will now have hundreds or polygons. When you then convert such a file into VRML, the result will be worse because the number of polygons will be multiplied by two. For instance, if the original file had 384 small squares, the new one will have 768 small triangles; the same cube geometry, but with an unnecessarily high number of polygons.

We recommend that you avoid such high polygon counts. Unless you have a good reason for them, keep the polygon count to a minimum. This can help avoid potential gaps but more importantly will minimize the model file size.

Another example would be a one-inch sized sphere. If you want a very smooth 3D model, you can use 10,000 polygons to create the sphere. However, you can also model the sphere with 2,500 polygons. It won’t be as smooth as the 10,000 polygon sphere but when printed on the 3D printer, you may not even notice the difference.

In the figure below, the sphere on the left has the highest number of polygons while the one on the right has the lowest number of polygons.

You can see that the fewer the number of polygons, the more faceted the model looks. So, although we advocate for fewer polygons, don’t reduce the polygon number at the expense of model quality.

The scale of your model should determine how many polygons you need to use. This is especially true for curved surfaces such as the sphere we just mentioned. The goal is to have enough polygons so that the end result doesn’t have a “faceted” appearance when printed.

There is no rule used to determine the number of polygons you need for your model. You’ll be relying on your experience.

However, there are a few tips to keep in mind. For instance, if your object is parametric, you can increase the polygon count parametrically. If it is a mesh and has no parametric history, then you can use subdivision features or your modelers tessellate to generate smoother, denser meshes.

Just remember that whenever you’re converting your 3D models to VRML, 3DS, PLY, or STL, the model will be triangulated which will increase the polygon count.

4. Inverted normals

Most 3D models consist of triangles. Whether it’s ZPR, STL, PLY, 3DS, or VML, they all consist of triangular polygons. Each polygon has three points and what is called a normal (or surface normal) direction.

A normal is an invisible line that is perpendicular to the surface of the polygon. The correct way to position your normals is facing outwards. The normals should face towards the outside of the shell.

The reason for this is simple. Normals tell the printer which way to add material. When your normals are facing outwards, the material will be added from outwards. If your normals are facing inward, this results in material suppression.

Fortunately, most 3D packages come with tools that make it easy to correct normal positioning automatically. Make sure to correct the normals before printing, otherwise you may get unsatisfactory 3D prints.

5. Dealing with Co-planar surfaces

Co-planar surfaces can cause all kinds of problems in 3D printing. They result in unpredictable or unacceptable prints and as such should be avoided, especially when printing colored or textured AEC models.

Let’s use an example to illustrate this point. Say, you have two wall shells that you want to slide together to create a corner of a building or house. The moment you do that, you’ll have two overlapping, outside surfaces where the two wall shells meet.

This usually doesn’t present a problem when you want to 3D print a monochrome architectural model where both walls are of the same color. The joint will just take the color of any of the walls and everything will be fine.

However, imagine a situation where one wall is supposed to have a different color from the other. Or, assume that the two walls are supposed to have different textures. There will be a problem where the two walls overlap because the convergence point will try to pick the characteristics of both walls.

In 3D printing, this can result in unpredictable and unacceptable results. In fact, if you can rotate the model to highlight the convergence point, you’ll see that the corner surface flickers since the two walls compete against one another.

The best way to avoid this problem is to avoid co-planar surfaces in the first place. You’ll have correctly textured corners and high-quality 3D prints.

6. Dealing with floating shells

The other thing you need to avoid when working on 3d printable architectural models is floating shells. Although unsupported shells or geometry are perfectly welcome for rendering architectural 3D scenes, a virtual walk through or an animation, they make 3D printing a little more difficult and may cause undesired results.

So, identify any floating points before you begin printing and remove all of them. This will allow you to print high-quality models.

The problem, however, is that in many cases, identifying these floating points before printing is not easy. Most modelers can only locate them after printing. For this reason, diligence on the part of the modeler is very important. You must take the time to thoroughly inspect your model before printing.

7. Smallest Printable Feature (SPF)

3D modelers are also always asking questions about SPF. What is the smallest printable feature on a 3D printer?

Our answer is simple – it depends. Since all models are different in scale, overall design, and complexity, it is impossible to say that a certain SPF value would work effectively for all modeling projects.

However, under normal circumstances, the following figures will serve you just fine:

  • For load bearing features, use ~0.12 to 0.20 inches (3 to 5mm)
  • For non-load bearing features, use ~0.06 to 0.12 inches (1.5 to 3mm)
  • For ornamental/fine detail features, use ~0.02 to 0.04 (0.5 to 1mm)Load bearing features are features such as walls, window frames, columns, and any overhanging features that aren’t supported.But we again want to stress that these are just our values. SPFs are completely up to the modeler and are greatly depend on the characteristics of your model. For example, walls can be thicker than 5mm, especially if the wall supports multiple other structures.In fact, if design permits, always go with higher measurements i.e. thicker features. Thick features are easier to excavate, gross/fine de-powder, and infiltrate.Beware too that there are certain features that may be too delicate to print. Such structures need “non-contact” fixturing to cradle the structure in a bid to minimize warping and prevent breakage during part removal or finishing. As you 3D print more and more models, you’ll gain more experience on this topic and learn what to print and what may not survive the finishing process. If you’re uncertain about the durability of certain features, a good option is to test print the model to prove the robustness of those features.

8. Strength and Support

We would also like to touch on strength and support for 3D models. As already mentioned, some elements of a model may not be able to survive the processing/finishing process which includes excavation, de-powdering, and infiltration. In such circumstances, artificial support may be needed.

There are two categories of artificial support systems in 3D modeling; integrated and removable.

Integrated supports

Integrated support is the support that eventually becomes part of the model even after finishing. It includes thickening of shells such as windows, columns, doors, and walls, and the addition of interior arches and columns.

Removable supports

Also known as fixtures, removable support are structures that are only brought in to support the model during finishing. After finishing is completed, the structured are carefully removed and discarded.

Examples of such structures include a roof overhang covering the entrance of a building. Printing the overhang while it is attached to the building is never a problem. However, during the excavation stage of finishing, the overhang can be destroyed.

To avoid this problem, you can introduce a simple support piece in your model, such as a cube, which can be used to hold the overhang in place through the finishing process. Once finishing is completed, this piece can be removed and thrown away.

9. Hollowing your model

Ideally, you should build completely solid models because solid models can support themselves. They aren’t easily toppled over.

However, if your main goal is exterior detail, then internal structures will matter little. So, you may want to save on material and considering that solid models consume a lot of material, may consider hollowing your model.

There isn’t a problem with this. In any case, solid models can be very heavy. Hollowing can reduce the weight while saving you powder, binder, and infiltrate.

Alternatively, you can also introduce a drain hole. The drain hole can then be used to remove any unused powder from the interior of the model.

10. Removing unnecessary geometry

As already mentioned, the number of shells you will use on your model is completely up to you. You don’t have to use a specific number of shells just because someone else did. You decide what you want to model, determine how many shells will allow you to create the best model, and work with that number.

We just want to caution you against including unnecessary shells in your structure. Architectural 3D models, at their best, are simple and clean. This means that you should only focus on what you need. Don’t add shells that serve little purpose. These shells will complicate the model for no good reason.

For example, if your goal is to show the exterior design of a house, with zero concern for internal spaces, floors, and geometry (walls, doors, furniture, bathroom fixtures, etc), then there is no need to include shells for that internal geometry. Delete those shells from the model file.

You will be left with far fewer shells which makes shell management easier. This can be critical when shells need to be repaired. During repair, the more shells you have, the tougher the job gets.

Additionally, having fewer shells when creating a model of a design concept can allow you to section your model and print only the section of interest at maximum scale. Printing at maximum scale is advantageous because it reduces need for thickening.

4. Mistakes to Avoid when Creating 3D Architectural Models

As we finish, let’s look at some of the common mistakes that you should try to avoid when printing 3D architectural models.

1. Ignoring the Materials Properties

In 3D modeling, each material is different. A material can be strong or it can be brittle. A material can also be flexible, or it can be solid. Some are also light or heavy, smooth or rough, and so on.

Do not ignore these material characteristics. If you choose the wrong material, your models might come down crumbling before they even reach the finishing stage. Or, the material may be too hard, making rounding off corners impossible. So, select your materials early, learn their characteristics by reading the material guide, and stick to the guides.

2. Ignoring 3D Printing Technology

Other than chemical characteristics, different materials also support different printing technologies. For instance, on most printers, you may be able to print interlocking parts with materials such as ABS, Alumide, and Polyamide. But most of these printers don’t support printing of interlocking parts with materials such as gold, bronze, silver, or resin.

You need to get familiar with what technologies your material supports. This can be done by mastering material categories. Typically, materials that belong to the same category, such as silver, gold, bronze, and brass are likely to support the same design technologies. But don’t just assume that all metals can be printed anyhow. For more information, again turn to our material guides.

3. Ignoring Wall Thickness

We want to stress that wall thickness is very important. Problems linked to wall thickness are by far the most common cause of unprintable 3D models. When walls are too thin, small parts on the model can become fragile and could break off easily.

On the other extreme, walls that are too thick often cause internal stress that may lead to cracking or even breaking. So, be extremely careful with this. If need be, test print to see how the walls are behaving before creating the final model.

4. Ignoring Resolution

The number of polygons used in your model is critical to the quality of the finished product. Keep in mind that this is a model for something much bigger. The real life structure will reflect the appearance of the model. So, the model has to look exactly like the desired product.

If you choose a lower resolution by choosing to work with a smaller number of polygons, the resulting model will be faceted and the final structure may also be faceted.

The 3D modeling process is a very technical process. Architectural modelers must be extremely careful at every stage of the project if you are to create high-quality models.

Some of the key areas you need to pay close attention to are thickness and resolution. Ignoring those two can be your downfall. In addition to the two, you also must take very seriously the identification and removal of gaps and holes. While they may not completely damage your model, those two can leave you with extremely poor 3D prints.

Finally, choose your 3D printing technology wisely. There are more than a dozen 3D printing software programs in the market at the moment and they are all different in one way or the other. Find what suits your project.

If you keep all these in mind, the only other thing you’ll need is a solid PC to work from and you’ll have a rewarding and enjoyable printing experience!

License: The text of "How To Make A 3D Printed Architecture Model" by All3DP is licensed under a Creative Commons Attribution 4.0 International License.

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