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January 7, 2019
In the world of 3D printing, the correct elaboration of 3D models is essential to achieve a good quality when it comes to printing.
Compatible files for 3D printing software (e.g. Simplify 3D) are of STL extension, different from a 2D render or image. These files are elaborated in most of the 3D modeling programs:
In the modeling process the user has to consider that the resulting part must be composed of a single solid. That is to say, the surfaces of the model have to define a single totally closed volume since open or intersecting surfaces do not allow its correct reading.
In the following note you will find different rules with some values to respect for FDM/FFF technology. This will help us to optimize the design to achieve the highest 3D printing quality.
Note: These rules and values are indicative to highlight the designer's work. The restrictive values of the 3D printers depend on the equipment and are different from those indicated.
Theminimum recommended for this type of shape is 1 mm wide, smaller becomes more complex or even impossible. Here the minimum thickness deposited by the extruder is taken into account. For a peak of 0.4mm the value automatically set by the slicing software is 120%, that is, 0.48mm. Therefore, a thickness of 1 mm is enough to have at least two passes.
This is the same case as point 1. Any thickness that is thinner than the width of the wire deposited by the extruder will disappear in the preview of the slicing software, and therefore will not materialize.
Whena part has areas that exceed an angle of 55º in height (as shown in the image), the printer has to create a support surface called a support so as not to print in the air. Although the part can be made correctly, the printing time will increase and the quality in the area will not be the same. Therefore, it is recommended in the same design to stay below 55º with respect to the perpendicular plane of the printing surface (i.e. the hot bed).
Inthe drawing we see two cases of texture with relief or openwork. In this case the minimum width is smaller than in the first two examples because these parts are not entirely necessary for the structure of the design. Some clear examples of this are the letters, drawings, textures or details that we put on (or in) the design.
Unlike the cantilever case, in this example the print has an A-pillar and a B-pillar to use as support points The distance between these two pillars connects to what we call a bridge. While I can make bridges longer than 30 mm without supports, the best quality without supports is achieved below this value. Then, depending on the case, it will be convenient or not to place supports.
Forthe openwork holes in the design we must give them at least a diameter of 0.2 mm, otherwise they will look more like a 3D printing error than an intentional geometry of the design.
Forthe interlocking parts we must leave a minimum tolerance of 0.3mm and a maximum of 0.5 mm depending on the geometry of the part and the type of interlocking we are looking for. It is important to keep in mind that with 3D printing we can think of making movable parts in one part. For this we simply have to design a weak joint between parts (to support the parts during printing) and then break the joint. We can see some examples of hinges here.
Whenwe see details of this style, that is, that are separated from the main body of the design, it is important that they are not too thin. In fact if we want them to stand out and come out with good quality we should make them thicker than the walls of the first of cases. Some examples of this can be antennas, beams, grids, etc.
Thisexample changes from the previous one simply because of the pin geometry. When the detail of the model is circular we recommend working with a diameter of at least 3 mm to achieve the best quality.
Withrespect to the dimensional accuracy of the part, we refer to the variation in measurements that may occur in 3D printing with respect to the original digital design.
