For the uninitiated, 3D printing can seem like a pretty straight forward job. You fire up the 3D printer, load up the file containing the model you want to 3D print and watch the magic happen. However, this process involves many different stages and processes. 3D printing enthusiasts and professionals use different software to design the models. They also use different materials in printers depending on the model they’re printing. They also use different printing technologies, depending on the complexity of the 3D model.
It’s perfectly natural to feel frustrated when you start encountering problems while designing and printing your own 3D model. Worry not, for we are here to help you! In this article, we’ll give you a rundown of most common mistakes and how to avoid them when designing a 3D model for 3D printing.
If you’re feeling too lazy to read through the entire article, here’s a table of contents so you can jump to the part you’re interested in:
Mistake #1: Ignoring Material Guidelines
When designing a 3D model for printing, before you even start with the design, you have to think about the materials you’re planning to use in the printing process. 3D printing materials come in many different forms and have different strengths and weaknesses.
Not all materials are created equal. Some are very brittle, which means that they are not good for support structures. Some materials are very flexible, which means you can use them for models that will be exposed to a lot of bending. Some are solid, which means they are perfect for designing gears, replacement parts, and other stuff that will be exposed to wear and tear. There’s also the question of color, you don’t want to make a replacement part that’s in a different color than the thing you’re trying to repair.
While designing the 3D model, you have to consider all the qualities of the material you’re going to use. Before you start, you have to examine what are you going to use your 3D model. After you’ve determined what purpose will the model fulfill, you will have an easy time choosing the right materials for the 3D printing process.
For example, if you are designing a replacement part for the bathroom sink. You won’t be using a material that has low water resistance, you would want to use ceramics (provided that you have access to a 3D printer that can print Ceramics). Ceramics come with their set of design recommendations that you’ll have to consider when designing the 3D models such as supporting overhanging parts, strengthening parts of the model that are sticking out, rounding corners and many other things.
Thankfully, material producers either ship the material design guidelines with the material or have it on their website.
Two most commonly used materials in 3D printing are PLA and ABS. PLA, or polylactic acid or polylactide, is a biodegradable material derived from corn starch. PLA is the most cost-effective material for 3D printing. While it has a very high tensile strength, its low elongation, and the fact that it melts at 49 degrees Celsius, making it a very brittle material. However, thanks to its very low shrinkage rate, making it perfect for large parts such as fan blades, molds, and prototypes.
ABS, or Acrylonitrile Butadiene Styrene, is much more mechanically stronger material due to its high glass transition temperature and high amount of bending before breaking. The company that pioneered this material is none other than Lego. ABS is a go-to material for the majority of mechanical applications. This material can also be acetone vapor finished, which will give your part a greater water resistance, and a beautiful glossy look. Keep in mind that the acetone vapor finish is somewhat costly and time-consuming, but the results speak for themselves.
If you need more flexibility in your model, you can use flexible materials such as nylon. These type of materials come with their own hidden cost of being quite difficult to print. You will have to paint a PVA mixture on the print bed in order for the material to properly adhere. You also won’t be able to print complex parts. Additionally, these materials are more likely to ooze out of the nozzle, which results in a hairy and less precise print. You will have a hard time removing support material because of its high adhesion, which means that the finished model will be scared if you’re not careful.
Mistake #2: Ignoring Printing Technology
After you have determined what materials you are going to use for your 3D model, you have to check what 3D technology you will have to utilize to print your model.
For example, if you want to print using materials such as ABS or Polyamide, you will be able to print interlocking parts while with other materials this is impossible.
Depending on what you’re planning to print , you have to pick the right 3D printing technology.
If you want to print using plastic or Alumide, you have a couple of options. You can use fused deposition modeling (FDM), which is the most popular 3D printing technology because it’s the most affordable. This process involves extruding melted material through a nozzle to print a cross-section of the model one layer at a time. The bed lowers each time a layer is finished, and this process is repeated until the model is finished. FDM is a go-to technology for printing small detailed parts that can endure a lot of mechanical stress. Because FDM printers use materials like ABS, you can also treat the models with acetone vapor to make them waterproof and give them a glossy look. Many companies use FDM to make various parts, from LEGO bricks to whitewater canoes.
Besides FDM there is also the SLS, or laser sintering technology. SLS is a process that involves melting successive layers of material powder in order to print a 3D model. This technology is excellent for making complex interlocking mechanisms. Parts printed with SLS technology have excellent isotropic mechanical properties, which means they are perfect for functional prototypes and models that have to perform some mechanical action. You also don’t have to use support structures while printing, which means you can go wild with the complexity of your 3D model.
However, SLS does have its drawbacks. For starters, SLS printed parts have grainy surfaces and internal porosity that requires a lot of work touching up the parts after they’ve left the printer. You also can’t print large flat surfaces and small holes because they are prone to warping and overheating, which leads to even more post-processing. And lastly, off-the-shelf SLS 3D printers are pretty scarce and are almost exclusively available to big companies. This means that you’ll have to find a service that offers SLS printing.
If you want to print multi-colored parts, just like with the ABS or Alumide, you have a couple of options.
The first option is the Binder Jetting. This process involves an automated roller spreading a layer of powder onto the print bed. Excess powder is pushed to the sides, which ensures the print bed is filled with a layer of packed powder. After the powder has been packed, the print heads simultaneously apply a liquid binder and color, creating a cross-section of the 3D model.
The biggest benefit of Binder Jetting is that it can produce very large and complex parts because it’s not limited by thermal effects such as warping or cracking.
However, you can’t make small detailed models, which means you are limited to large models.
Another popular option is SDL 3D printing, which involves layers or adhesive paper successively glued together with a heated roller, and cut into shape by a cutter laser. This type of printing technology is perfect for rapid prototyping because you can make somewhat complex models that can be used as a proof of concept. Just keep in mind that models won’t be water resistant and very susceptible to tearing because they’re basically made out of paper.
Mistake #3: Ignoring Wall Thickness
The most common reason why some 3D models come out wrong is that people are ignoring wall thickness. If you model the walls of your 3D model too thick, it will cause internal stress, which will, in turn, cause problems while printing. And if you make the walls too thin, you won’t be able to print the fine details of your 3D model.
Fortunately, there is a simple chart that you can follow in order to avoid any problems with printing. In the table below, you can see the recommended and absolute minimal thickness for the most popular materials.
We recommend you don’t make your walls as thin as possible because there is no guarantee that the 3D model will come out good. We recommend you stick with the recommended thicknesses for obvious reasons.
So, why are there any limitations, anyway? There is a number of limiting factors you have to consider, both during and after 3D printing. 3D printers print parts one layer at a time, so if a feature is too thin, you are risking the resin deforming or even detaching. This means that there isn’t enough material to stick to the main body of the 3D model.
Additionally, just like you’d want to have a strong and stable support structure for your 3D model if the model itself has thin walls, it will likely bend before the resin dries and cures.
Even if you managed to print a 3D model that has thin walls, you still have to clean it and remove support materials. Cleaning involves water jetting the excess material from the 3D model, which means that you are risking breaking the model. Moreover, to even print a thin wall, you will have to use extra support material. And when you remove the material, the part is even more fragile.
People often confuse minimum wall thickness with the resolution of the 3D model. Resolution determines how precise and detailed the model can be, provided that the walls are thick enough to provide structural support.
You can think of resolution as to how accurate the 3D model can be for printing. Resolution is very similar to dimensional tolerance. For example, a hollow sphere can be in high resolution, but if the walls are too thin, it will collapse under its own weight. The resolution will determine how smooth the surface of the sphere will be. The lower the resolution, the more “steps” will the curvature have.
There are some exceptions to the wall thickness/thinness. Some features of the 3D model can be printed below the recommended minimum thickness. You can print ribbing, cross supports, flat, and supporting components. However, this is somewhat risky because you’re risking warping your model while it prints.
We understand that you want to push your design to its limits, however, we suggest you stick with the recommended thicknesses. Even if you manage to print your model, you are risking breaking your model while cleaning it.
The main takeaway is that you have to pay close attention to the thickness of the walls because it will save you a lot of time and hassle.
Mistake #4: Ignoring Software Guidelines
3D printing enthusiasts use different 3D modeling software packages. Some of these software suites are specifically developed for 3D printing, while others are intended for 3D artists and designers. Some 3D modeling software suites come with automatic wall thickness features, while others don’t.
Each 3D modeling software is a beast of its own with their own functions and processes. Depending on the software you are using, shells must be joined together, models must be made watertight, and wall thicknesses must be set.
For 3D modeling, you can use a couple of different software suites:
- Blender – a free, open-source 3D modeling software for creating anything in 3 dimensions. This app has a steep learning curve so it might not be the best choice for beginners but it’s ideal for those who are comfortable with concepts of 3D modeling. If you ever feel lost and don’t know what to do, you can always visit Blender’s support forum. It has a more than helpful community that will gladly help you with any of your problems.
- SketchUp – is a 3D modeling software suite that offers a perfect mix of simplicity and functionality. It has a user-friendly interface and a flat learning curve. Because of this, we recommend it to newbies. It’s completely free and comes with everything you need for a 3D modeling for printing, provided that you download the free STL export addon.
- TinkerCAD– is a computer-aided design a browser application that is purposely made for beginners. You can use it to make 3D models from basic shapes and customize these basic shapes to achieve precision in what you want to create. It also allows you to create 2D shapes and convert them into 3D models. You are somewhat limited compared to other applications, but it’s perfect if you’re still getting the grip of 3D modeling.
- Slash – is both extremely easy to use and refreshingly different in it’s approach to 3D modeling. Like with Slash, you design your model from big blocks. However, in Slash you can remove smaller blocks from the big block by using tools such as “hammer” and “drill”. With this software, you are essentially acting as a virtual stone cutter. Other features include a logo and 3D text maker. You can import an image and create a 3D model out of it and add 3D text to it. It is completely free and browser-based, so there’s nothing stopping you from using it today!
Mistake #5: Ignoring File Resolution
So, you’ve gone through the design guidelines. You’ve determined what material you’re going to use to print your 3D model. You’ve designed the model in a 3D modeling software of your choice. You’ve made sure the walls are thick enough. Excellent, but there is one more important thing to think about: File Resolution.
As you might be aware, you save your 3D printing designs in STL format. While exporting your design to STL format you have to pay attention to the resolution. If the resolution is too high or too low, you will run into issues while printing. You have to keep in mind that you define the resolution before you export it to STL format.
It is smart to choose 0,01 millimeters for good file export. Exporting using tolerances smaller than 0,01 millimeters is useless because 3D printers cannot print models in such fine detail. If you are exporting with a tolerance larger than 0.01 millimeters you can expect to see triangles and steps in your finished model.
This is about it for this post. Leave us your thoughts below. Did we miss anything?
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