Printing a 3D file is not so simple — first you need to know about 3D file fixing. Here are some basics:
BACKGROUND
3D printing is a blessing for architecture as it allows us to create architectural models quickly and at a reasonable cost. One of the greatest benefits of 3D printing is that you can create scale models of all sorts of structures. It’s a great way to get your clients to see your work. The real-life perspective of working with 3D models along with being able to re-print a new design is a combination that results in immaculate accuracy while building structures in the real world.
The earlier complexity and high cost of architectural models is affected greatly with 3D printing. Integrating it into your architectural firm is easy since most firms already have an in-house design team that uses CAD applications. In such a case, you can simply connect your 3D printer to your computer, or hire a professional 3D printing service if you don’t have the required services in-house.
Elevations that were a problem in 2D are easy to create in 3D printing. You’ll be able to understand them simply by rotating the drawing, as you would a physical model.
Another wonderful thing about 3D printing is that you can avoid human errors. With the freedom to design without worrying about this, you can try new things since test models are quick, accurate and cost effective to create.
To create useful 3D models, you must master the techniques of creating 3D printed models. It is complex process but as discussed, very rewarding. It’s important to be mindful of a few things before as well as while you create a 3D print for a 3D model. Here are some of them.
SOFTWARE AND FORMATS
3D Modeling Software
Step one to create the perfect 3D print is to understand the 3D modeling software. Software applications allow you to build from scratch, or to convert a 2D model into 3D. There are over a hundred different models and you can select one based on your personal requirement. Ensure you understand all features of the software you decide to purchase. Keep in mind that some software will require certain hardware and you should make your decision based on that combination. Budget, level of expertise, scale and print size will help you take your decision. It’s important to spend the early days figuring out exactly what your requirement is so that you don’t invest in the wrong software.
File Format
The most common file format for 3D printing is Standard Triangle Language, or STL. Your design will be translated into triangles in a 3D space. While exporting the file you will need to define a tolerance for the export, defined as the maximum distance between the original shape and the STL mesh you are exporting. Try and avoid printing a tolerance less than 0.01 mm as 3D printers cannot print at this level of detail.
We’ve talked about the other file formats at the end of the article.
SHELLS AND PARTS OF THE MODEL
The Parts of your 3D Model
Shells or nodes are the components or parts of your 3D model and will be present irrespective of the software you use. They make up the final model and each model can have from a few, to a thousand shells. Experimenting and using shells that are different from what other architects use could be what makes your entire structure unique. You must understand exactly what shells are needed, and where they must go.
Ensure the Shells are Solid and Watertight
Your model will not be able to print properly if it has holes of gaps in it. Flat open surfaces will need to have some thickness. To ensure this, follow the vertex-to-vertex rule. The rule states that all adjacent triangles share two common vertices and if you don’t comply with this rule, you might end up with holes of gaps in your file. Even though it’s possible to fix this with applications, you should be able to do so manually. Either through the process of capping, or by forming a new triangle with common vertices as per the rule. Be careful of floating unused points as these would create new gaps.
Another option is to fill gaps by converting your file from one format to the other. Since converting might cause new gaps, it is better to first identify all the gaps, and then take care of them after formatting to the new format. Having many shells can help, since you can repair a faulty shell, or create a new one in case one shell is damaged and causing the problem.
Unsupported or Floating Shells
While unsupported shells are alright in virtual architectural models, they become difficult to deal with when printed. It’s important to identify any floating or unsupported shells before printing, which requires diligence. Doing so will go a long way in prevent mishaps in the final 3D printed model.
Caution against Too Many Shells
While it is completely up to you how many shells your model would need, be cautious against working with too many unnecessary shells in your structure. Your architectural model needs to be simple and clean and the best way to achieve this to use only what you need. Fewer shells are easier to manage while too many only complicate matters. Too many shells at a time of repair becomes complex too.
Fewer shells can ensure you section your model well and only print sections needed, at a maximum scale. Printing at maximum scale is good because it reduces the need for thickening.
DOUBLE CHECKING DETAILS
The Correct Polygon Count
Your geometry topology and overall polygon count are important to successfully create a 3D printable model. Try to keep the geometry clean and the polygon count to a minimum. Not only will this help avoid potential gaps, but will also minimize the model file size. But remember, the lesser the number of polygons, the more faceted the model looks so don’t just try to reduce the count and end up compromising on the quality of the model.
Positioning your ‘Normal’
Most 3D models consist of triangular polygons, each of which has three points and a ‘normal’ which is the invisible line perpendicular to the surface of the polygon. Ensure the normal is facing toward the outside of the shell. This is because normals tell the printer which way to add the material, and this way the material will be added from outwards.
Inside vs. Outside
To determine the volume of a model, most 3D modeling programs distinguish between the inside and the outside surfaces. You must double check your files to make sure all normals are facing the right direction to avoid inward-facing or reversed faces.
How Small is too Small to Print?
What is the SPF or smallest printable feature on a 3D printer? Well, it depends on the scale, overall design and complexity of the project. Some features might be too delicate to print and you can use “non-contact” fixtures to attach them to the model to prevent breakage. It will take a bit of an experienced guess to understand what features might be too delicate. You can try test-printing models to fully understand what works best for you.
Assigning Thickness to Each Wall
When shifting from visual 3D models to printed 3D models, an important addition is wall thickness. While visual 3D models don’t require them, it is important each surface in your 3D print has been assigned wall thickness. You will need to feed in information about how thick you need each wall to be, or if the model is to be entirely solid. Being careful about this can go a long way in avoiding printing problems.
PRINTING THE MODEL
Co-planar surfaces Can be Tricky
Do be careful while working with co-planar surfaces as these can cause all sorts of problems in 3D printing, particularly while working with colored or textured AEC models.
Your Printer Might Find Overlapping Confusing
Intersections or internal overlapping in your model might confuse the printer about what exactly to print. While preparing to print a model, be careful of this. Think of it in a 2 dimensional space first, to help understand the best way to deal with these intersections.
Printing Multiple Parts
While printing more than one part, upload each separate object individually. Group models are not always a good idea. If you need to print many small parts, you could consider designing a grid container for your 3D prints.
Printing the Tiny Details
Small decorative details such as engravings or embossing must be of a certain size in order to appear properly on your model. The exact minimum size would depend on the material you use to print. It’s important to ensure you stick to this so that everything is readable once printed.
EXTRA MATERIAL
Artificial Support
Speaking of SPF, what do you do about the elements of a model that you know might not survive the entire process of 3D printing?
Artificial support is a good option. These can be categorized into integrated – that eventually becomes a part of the final model – and removable – that can be removed after the finishing is complete.
Hollow vs Solid Models
If the primary aim of your model is to show off its exterior detail, save up on material by printing a hollow model. Though you will need to ensure they’re sturdy enough to not topple, they needn’t be entirely solid. Solid materials aren’t necessarily a bad thing as they will be stronger and harder to break. But they can get too heavy and more expensive to build.
Building Escape Holes
While building a hollow model, material might get trapped inside since printers print layer by layer. To fix this, incorporate escape holes in your design through which you can remove any extra material.
By being mindful of these factors, you are already closer to printing your 3D models perfectly. An important point touched upon earlier was the 3D printing file formats you can use. We’d talked about STL, but here are three others that are popular.
POPULAR 3D FILE FORMATS
Using the correct 3D file format is a crucial step as the format of your file will decide what information the 3D printer will receive. You can choose what works best for you as per each format’s specifications. Here are the four most popular ones.
STL (Standard Triangle Language)
This format is the most popular in the world, and was developed by Chuck Hull in 1987. It saves your model as a surface of geometrical shapes, turning it into a triangular mush, but does not carry information about the models texture or color. However, most people do not find this an issue.
STL ensures your model has no holes or overlaps, which is a process known as Tessellation, which can save you lots of hassle during printing.
OBJ
OBJ is short for Object and is the next most common file format. The advantage it has over STL is that it stores color, material and texture data so you can print in multicolor. Not only does it offer Tessellation, but also advanced options like free-form curves and surfaces.
The downside is that it is more complex than the STL and it is not easy to repair in this format.
OBJ file comes with an MTL file which is responsible for storing color information. It can be hard to keep track of both while transferring.
AMF (Advanced Module File)
This format was introduced by ASTM in 2013 solely with the purpose of catching up with the evolving Additive Manufacturing technology.
AMF stores information about the geometry, color, material, lattices, duplicates and orientation.
Just like STL, it turns the surfaces of 3D models into mesh. The difference is that the triangles have a sleek finish owing to the fact that the triangles can be curved.
3MF
This format too was designed for Additive Manufacturing needs, by Microsoft. They have a special body called 3MF Consortium to work the 3MF. It consists of geometries, color, materials and textures and has an open source.
Once you decide what file format works best for you, you can get started with your 3D printing. Be mindful of being thorough with your model before printing to avoid errors, but also be creative and have fun!
If you get stuck and need help, contact us and we’ll do our best to help you.
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