Overhangs overview
Identifying and managing overhangs in your 3D model
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Identifying and managing overhangs in your 3D model
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Overhangs are surfaces of a 3D print that are weakly supported or totally unsupported by the layers of material underneath them. Such surfaces include the underside of the arms in the letter “T” and “Y.”
Unsupported overhangs are challenging to produce because of how 3D printers deposit material: one layer at a time from the bottom up. If a “T” is printed standing upright, the print will proceed without issue until attempting to print the arms. Without anything to support the underside of the arms, the material deposited by the printer will droop due to gravity and fall toward the build plate, ruining the print.
Note that by printing the “T” upside down, the print is successful.
In the case of a “Y,” the arms are more likely to print successfully since they angle upward. The success of the print depends on the angle between the underside of the arms and the vertical plane. The smaller the angle, the greater chance of success. Typically, features with angles less than 45º from the vertical plane will print fine. We generally recommend not pushing this limit.
A flat, overhanging surface spanning a short distance is treated differently by the printer. In this case, the printer will deliberately attempt to “bridge” the gap, printing in the direction that minimizes the amount of overhanging material. If your design has flat overhangs, ensure that they are less than .25” in length.
Supports are a scaffolding, printed separately from the part you’re trying to produce and are printed to uphold overhanging surfaces. Supports significantly increase the time and cost of a print, and they often leave behind unsightly aberrations on the outside surface; therefore, it is highly recommended that parts are designed not to need supports. Only in exceptionally rare cases do we accept the need for supports in your design.
Generally, the expense in time, money, visual quality, and functional quality isn’t worth the use of supports when solutions exist that eliminate the need for supports entirely without compromising the look or intent of the design.
The general outer profile of a form
Curved bottom surfaces
Inside of thin, dome-like forms
Rounded edges that approach tangency with the build plate will falter at the very bottom. Implementing a small chamfer here will alleviate the issue without compromising the form.
Thin dome-like features require that the interior surface be tapered to extend no less than 24 degrees from the build plate at the top. Tapering introduces the need for infill between the interior and exterior surfaces.
If a part is flat at the top (or can be made flat by splitting the body into two parts), mitigating an overhang can be as easy as simply flipping the part over during printing.
By splitting an otherwise unprintable body into two, overhanging surfaces on the underside of a print can be flipped over and made into topside surfaces of a print.
Sometimes other manufacturing constraints take precedence and require that support material be used in order to successfully produce a part. Instead of relying on the finicky supports automatically generated by Gcode slicing software, supports can be manually modeled into the part that requires them. This ensures that the entirety of the surface gets the support it needs.
Translucent parts visually benefit from having as little infill as possible. Instead of tapering the inside surfaces like in the case of vertically-oriented translucent parts, horizontally-oriented parts benefit from instead manually modeling thin lines into the body that will serves as supports for the overhanging interior surface.
The weight cavity “ceiling” is one of very few cases that we permit the use of support material. Since the amount of support material is relatively low, the visual aberrations left behind by the support material are obstructed from view by the metal weigh, and the alternatives are limited and more trouble than they’re worth, we accept the need for supports here.
