Vladimir Bulatov, Shapeways 3D Graphics Researcher, said this as he explained why our newly launched 3D model Wall Thickness Tools were such a challenge to build. “I am a 3D modeler and when I first started thinking about automatically measuring and fixing a model’s wall thickness for 3D printing, I thought the problem was unsolvable.” How can designers continue to push the boundaries of design with 3D printing, unhampered by manufacturing guidelines? This challenge was too large for us to ignore, and we set off close to four (4!) years ago to solve what seemed impossible.
3D printers, like any manufacturing tool or machine, have limitations on the minimum distance between two points, known as ‘minimum wall thickness.’ Designing with minimum wall thickness in mind is important but difficult, so giving designers feedback on their designs is critical, especially as 3D printing becomes more accessible.
Wall Thickness Tools are two innovations by Shapeways that are available for free to the entire 3D design and 3D printing community.
- Wall Thickness Visualization automatically identifies the areas where your model might need adjustment in order to meet minimum wall thickness to survive 3D printing and post processing.
- Wall Thickness Fixing automatically thickens your model’s walls to the minimum recommended thickness for a specified material. Fixed models can be printed or downloaded for further adjustment.
We don’t have the silver bullet, but we do think the tools will make a significant impact. As with other creative industries where feedback is critical, giving 3D designers immediate feedback is a leap. It was a substantial undertaking, so we’re sharing why it was such a difficult challenge, our discovery process, how it works, and ultimately how we hope it will impact the 3D print community.
Why is wall thickness such a difficult challenge to solve?
The goal was to create tools to help designers identify and fix potential problem areas prior to 3D printing. The solution had to provide accurate and relevant data, in order to help 3D designers speed up the design and iteration cycle.
Man vs Machine
Take, for instance, a triangle: at the very tip, the wall thickness gradually becomes zero. The same concept applies to the edges of a blade of grass. The wall thickness will eventually get below the minimum wall thickness requirement for 3D printing. Yet these objects are printable and a 3D Printing Engineer would know that. But is it possible to create an algorithm that provides exact wall thickness measurements only when it is a problem?
Measurement Complexity
Another challenge is measurement complexity. For example, imaging drilling a hole into one side of a 1x1x1cm solid cube, but stop short just before the drill goes all the way through the other side. Looking at this model physically would not reveal that the bottom of the hole is too thin to be 3D printed. Thus, even if you were using software to measure wall thickness point by point, you would need to know to measure that particular point.
Furthermore, we see a lot of complex 3D models, designed by our community, that push the boundaries of design. In order for us to accept every creation by any designer, the Wall Thickness Tools can not be limited by complexity.
Our Discovery Process
The ideas of Alexandru Telea and Andrei Jalba, published in the academic paper, Voxel-Based Assessment of Printability of 3D Shapes were our starting point in developing the Wall Thickness Visualization Tool. Over the past four years, we developed three versions of the Visualization & Fixing tools, each building on the learning from the last.
The simplicity of the tool is deceiving, as the algorithmic power required to run the tools against a constant stream of 3D models require up to 25 computer servers running simultaneously. We host more than one million 3D models, receive thousands of model uploads per day, and, as a result, manage the biggest 3D printing database in the world. The breadth of 3D models uploaded by our community plays a critical role in our discovery process, as the designs span organic, geometric, architectural, parametric, and sculptural 3D models, representing a huge range of design complexities and needs. We run the wall thickness tool algorithms across thousands of uploaded models to validate the tool’s performance against actual printability as determined by our 3D Printing Engineers.
How it Works
Now let’s circle back to the question of: “Is it possible to create an algorithm that provides exact wall thickness measurements only when it is a problem?” We answered this question by changing it.
We shifted the question from “What is the wall thickness and is it too thin?” to “How do we enable designers?” The information that is valuable to a design isn’t necessarily the exact thickness of the wall, but to the visual identification of potential problem areas. When designers have information about potential problems, they’re empowered to decide whether it’s a problem worth solving.
The Wall Thickness Visualization Tool does this by automatically measuring the distance between two points, in real-time, through the entire model. It then classifies areas as ‘safe’, ‘suspect’, or ‘unsafe’, for the designer to determine which areas should be fixed (such as a thin wire) and not be fixed (such as details or edges).
The Wall Thickness Fixing Tool creates a ‘thin walls skeleton’ for area suspected of not meeting minimum wall thickness requirements. It then inflates this skeleton to what the minimum wall thickness should be (known as ‘fixes’ or ‘delta geometry’). The fixes are combined with the original model to create the ‘fixed model’.
Fixed models are just one way to adjust a model to ready them for 3D printing, but not necessarily the ideal way for the needs of the designer. The images below demonstrate how the the tool thickens a thin wall, but creates a potentially undesirable protrusion on the flat surface on the right side of the model. Thus, the tool’s value is in providing immediate guidance on preparing a model for 3D printing, as well as the fixes themselves, and are meant to empower designers to update their designs as needed and much more quickly.