What Is An Overhang Face When Modeling 3D Objects For Printing?


3D Printing Troubleshooting Tips
3D Printing Troubleshooting Tips

When designing your models for 3D printing, you are required to follow stricter guidelines for modeling than what you normally would for a render or an animation. There are principles of modeling 3D objects that ensure the hardware you use is capable of creating the specific shape that you design.

An overhang face is a part of the geometry that is effectively hanging off of the model. In other words, it is not well supported by the structure of the object. As a result, these faces make require additional supports to be constructed to maintain the object’s shape while 3D Printing.

Overhang faces are not the worst things to deal with when it comes to designing 3D printable models, and the shapes that you create will likely have overhang faces regardless. So just how important is it to be able to identify and deal with this type of geometry?

How Do Overhanging Faces Affect A 3D Print?

Depending on the design of your model, it is very likely that you will have at least one face that is classed as an overhang. But what is the definition of an overhang in 3D space? Well, an overhang is any geometry that is not supported by the structure of the model.

For example, if you created the model of a demon character’s head, and decided to add a pair of horns to that head, then the horns, while attached to the head, are not supported by it. The horns hang from the head and so the faces used to construct them overhang.

You will also find that the geometry towards the bottom f your model may fall into the category of an overhang, because there is nothing below the geometry that supports it. This is perfectly normal to see though.

Using the 3D print toolbox add-on, you can go into edit mode for your model and select any faces that are classed as overhangs, like in the picture below.

Selecting Overhanging Faces

Your 3D printer requires that you use certain types of materials to create your objects, and these materials can vary in terms of their structural strength. Example materials that you would use for 3D printing include, but are not limited to:

  • Ultrafuse Stainless Steel
  • Polyvynal Alcohol Plastic (PVA)
  • Alumide Powder
  • Resin
  • Graphene

So depending on the printer that you have you can use metal, resin, plastic, or other material types for your objects. Some of these options, such as using a resin-based material, are not as structurally sound as the others, and therefore may be prone to failure either during or after the 3D print.

How Can We Solve The Issue Of Having Overhanging Faces?

Your first thought maybe that you need to adjust your design to minimize the number of overhanging faces in its geometry, but why should we change the design of our model? Surely there is a way to make it easy to print the model without compromising the design too much?

Fortunately, this issue is one that was discovered before 3D printing was even a real industry, and there are software applications that can be used to add a support structure to your 3D model so that it prints better.

You cannot send a 3D model directly to your 3D printer, as you are instead required to export the model as a suitable file type and then send it to what is referred as a splicing application. This type of software is used to prep a 3D model for the process of being physically printed.

An example application is Cura. This is an open-source and free splicing software developed by Ultimaker, which is a company that creates its own brand of 3D printers. This software is used to check over a model before converting it into a gcode file that can be used by the 3D printer to print the object.

It is also able to create a support structure for your model. This support structure is printed along with the base design and is used as a scaffold during the printing process.

This scaffold is intended to be weaker than the object itself so that when the printing process is complete you can remove the supports and then sand down the model to get your final result.

Should you use this support structure in your models? The answer is generally yes, as it allows for a safer and more efficient printing process at the expense of a small amount of material. The task of breaking off your supports is preferable to having the parts of the design break instead.

Should We Avoid Overhangs Or Is It Not Necessary?

The short answer is no, you should not have to worry that much when it comes to overhanging geometry so long as you are able to add the support material using the splicing software. That said if the overhang is not a required part of the models’ design it may still be best to avoid having it in the final export.

Most 3D printers will still be able to produce strong parts depending on the materials that are used. If the material used is weak, then the parts of the model that are less well supported will be more prone to breaking.

However, with your splicing software, you should be able to create a scaffold supporting any overhangs that you may have in your design.

What Other Issues Can Occur With 3D printable Models?

There are several more serious issues that can occur when designing your 3D models which will require fixing in Blender.

Having overhangs is often unavoidable for many 3D print designs and is in truth not that serious of an issue depending on the material used and the creation of a support structure in your splicing software. Below is a list of additional issues that can occur on your model that you should most certainly look to avoid:

  • Zero Faces/Edges
  • Incorrect Normals
  • Intersecting Faces
  • Non manifold Geometry
  • Non Flat Faces
  • Sharp Edges

All of these are avoidable so long as you have a good workflow for creating your topology, and all can create artifacts or structural weaknesses in your model. In some cases, your printer can even refuse to print the model if the software detects any substantial errors in the design.

Thanks For Taking The Time To Read Our Article

We appreciate you taking a look at this article on how overhanging faces can affect a 3D printed model. We have gathered below a small list of topics that we believe you may be interested in reading.

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