3D printing has some incredible capabilities including increased design freedom, lower cost, and faster lead times. High customization and the capability to produce products with increased geometric complexity are two of the main benefits of designing for 3D printing. Additionally, there are also some constraints that designers should be aware of when designing for 3D printing. These include support structures, dimensional accuracy, minimum feature sizes, surface quality, and assembly tolerances.
We’ve have created the ultimate 3D printing design guide to help you design better 3D printed products!
Dimensional accuracy is the variance between the dimensions specified on the CAD model and the dimensions on the actual printed part. It will depend on the type of 3D printing method used, but typical accuracy values for fused filament fabrication (FFF) are +/- 0.010 IN.
We conducted a test inspection when calibrating our printers on 1 IN test coupon cubes and achieved the following results.
Maximum Bridge Distance
Maximum bridge distance refers to the largest gap that can be spanned without support from one feature to another without failure. Adjusting the cooling, temperature, and material will cause this value to change, but a typical PLA material can span a gap of approximately 20 mm unsupported. In this example, the bridge length specified in the CAD file was printed, but the result was very stringy and a non-solid structure. By the 25 mm bridge section, the filament started to become less solidified as the distance increased.
Minimum Hole Size
Minimum hole size refers to the smallest hole that can be printed without the hole simply being filled in with material. FFF machines can typically achieve hole sizes as small as 2 mm. As can be seen in the example below, the walls began to close in on the engraved details. The pins also started to lose their shape.
Minimum Wall Thickness
A minimum width of material is required for 3D printed walls. Typically, for FFF machines, anything smaller than 1 mm could have gaps or deformities. In this example, the 0.5 mm wall seen below, although larger than the size of the 0.4 mm nozzle still came out with some holes in the feature.
Minimum Feature Size
Minimum feature size indicates the smallest detail that the 3D printer will be able to print with full resolution. Features need to be larger than the size of the nozzle. In most instances, the minimum feature size that can be printed without deformities or gaps is 2 mm.
Support Overhang Angle
3D printers cannot print in midair and there is a maximum angle upon which a printer can print before distortion happens. Typically, anything under a 50-degree angle can be printed without support material. Some machines and material can print with slightly higher angles, but 50 degrees is the standard.
Many times, designers want to design text directly on a 3D printed part, either embossed or engraved. Both types of indented or extruded text should have a minimum width of 2.0 mm and a minimum of 0.5 mm extrusion length. Similar to the pins and holes example, the larger text has no problem maintaining a sharp and crisp outline, but as the size decreases the plastic begins to disform.
Maximum Overhang Length
Max overhang length is similar to overhang angle and max bridge distance except the angle is 90 degrees and the overhang does not connect to another feature. The feature is hanging in midair at 90 degrees from the model. Typically, such extrusions can protrude from the model max length between 1-2 mm. In this example, the furthest point on the edge is 6 mm away from the model and the overhang begins to warp.
Tolerances For Assembly
The tolerance gap between components in an assembly will vary depending on how tight the components are required to fit together. For a transition fit, a 0.5 mm gap can be used. If an interference fit is desired, then a 0.2 mm tolerance can be used. For a lose fitting clearance, that allows for more freedom to move, a gap between 0.6 and 0.8 mm can be used. In this example, a 0.5 mm clearance allows the two components to be easily connected and disconnected.
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