According to MIT, researchers have created 3D models to consider the restrictions of the 3D printing during the design process. In experiments, they showed that their approach could be used to produce materials that cut off much more precisely in the way they are intended.
“If you do not take these restrictions into account, printers can either over- or subtract, so that your part is more difficult or easier than intended. “With our technology you know what you get in terms of performance, since the numerical model and the experimental results match very well.”
The approach is described in the journal materials and design in an open access paper co-autorized by Carstensen and PhD student Hajin Kim-Tackowiak.
With 3D printing, materials with more complex internal structures can be produced. “3D printing processes generally offer us more flexibility, since we do not have to develop any forms or forms for things that are produced by more traditional means such as injection formations,” said Kim-Tackowiak.
Theory meets reality
Since the 3D printing has made production more precisely, you have methods for designing complex material structures. One of the most advanced computer design techniques is topology optimization, with which new and often surprising material structures are generated that can exceed conventional constructions, in some cases that approach certain performance thresholds. It is currently being used to design materials with optimized rigidity and strength, maximized energy absorption, liquid permeability and more.
However, topology optimization often creates designs in extremely fine scales that reliably reliably had 3D printers. The problem is the size of the print head that extrudes the material. If, for example, the design looks at a layer of 0.5 millimeters thick and the print head can only extrude 1 millimeter thick layers, the final design is distorted and imprecise.
Another problem has to do with the way 3D printers generate parts, with a print head extruding a thin material bead while gliding over the pressure area and gradually building parts by layer. This can cause a weak bond between the layers and make the part more susceptible to separation or failure.
The researchers tried to tackle the separation between the expected and the actual properties of materials that result from these restrictions.
“We thought we knew these restrictions at the beginning, and the field has better quantified these restrictions, so that we can design just as well with this process,” said Kim-Tackowiak.
In earlier work, Carstensen developed an algorithm that introduced information about the pressure nozzle size in design salgorithms for radiation structures. For this paper, the researchers set up this approach in order to include the direction of the print head and the corresponding influence of the weak bond between layers. They also worked with more complex, porous structures that can have extremely elastic properties.
With the approach, users can add the design salgorithms that extrudest the middle of the pearl from a print head and the exact position of the weaker binding area between the layers, variables. The approach also automatically dictates the path that the print head should hit during production.
The researchers used their technology to create a number of repeated 2D designs with different sizes of hollow pores or density. They compared these creations with materials made with traditional topology optimization designs of the same density.
In tests, the traditionally designed materials of their intended mechanical performance more than materials that were developed with the new technology of researchers in material density under 70%. The researchers also found that conventional constructions consistently overlaid during the production. Overall, the researchers' approach led to complex 3D printed parts with more reliable performance among most densities.
“One of the challenges of topology optimization was that you need a lot of specialist knowledge to achieve good results. As soon as you take off the designs from the computer, the materials behave as you thought,” said Carstensen. “We just try to get these high-fidelity products.”
A new design approach
The researchers believe that this is the first time that a design technology is responsible for both the print head size and the weak bond between the layers.
“If you design something, you should use as much context as possible,” said Kim-Tackowiak. “It was worth seeing that a more context in the design process makes its final materials more precise. This means that there are fewer surprises. Especially if we insert so many more arithmetic resources into these designs, it is nice to see that we can correlate what comes from the computer, which comes from the production process.”
In future work, the researchers hope to improve their method for higher material densities and for various types of materials such as cement and ceramics. Nevertheless, they said that their approach was an improvement compared to existing techniques that often require experienced 3D print specialists in order to take into account the restrictions on the machines and materials.
“It was cool to see that only by the size of their deposition and the values for bonding real estate they receive designs that would have necessary advice from someone who has worked in the room for years,” said Kim-Tackowiak.
The researchers say that work paves the way to design with more materials. “We want this to enable the use of materials that have not taken into account people because printing with them has led to problems,” said Kim-Tackowiak. “Now we can use these properties or work with these quirks instead of not using all material options that are available to us.”