Fixing Mesh in Complex 3d Printing Models
There is nothing more frustrating than to spend many hours of designing your 3d model, only to find out you will encounter an error when it’s time to upload or print it, right? But fret not! This tutorial will help you fix the errors as you prepare for 3d printing. Follow the guidelines and solution below to have a seamless uploading and printing of your 3d model.
- Reducing Polygon Count
In printing complex 3d models, generating .stl and .gcode files can be made a lot quicker and easier if your 3d model doesn’t contain unnecessary polygons. Since the polygon have no depth, the thickness of an object is often defined by the volume within a closed set of polygons. If there are gaps, your model will not be printed as the printer won’t read your model as a solid object. Furthermore, too much polygons in a 3d model may become too much work for your servers and printers to handle.
Fortunately, there is a method known as “polygon reduction” that helps us solve our problem with printing complex 3d models. In this section, we will learn about 2 polygon reduction techniques that will help us remove the unnecessary internal surfaces of our 3d models, whether you are printing solid filled models, or hollow, but closed structured models.
Combine vs. Boolean Union
When your model is made of multiple objects, make sure that they are joined in the right way. In Maya, you can achieve this and merge 2 object together by using the Combine or Boolean Union. Either method used will result in a single object. Below is an example of mockup object made out of a cone and a torus.
Figure 1.1.1 Cone and Torus Mockup Design
1.2 Combine Method:
When 2 models are merged using a Combine operation, the resulting object will contain ALL vertices of the 2 source objects. As you can see on the design below, all of the vertices in the 2 objects are visible,including the vertices in the internal structure. Resulting in an overlapping/crossing surfaces. These overlapping surfaces may not join up correctly when printed.
Figure 1.2.1: Combining 3d model using the Combine Method
When to use Combine Method?
You can use Combine method if:
- you want to keep the internal structure of both source objects.
- you want to create a new internal structure with the combined object.
1.3 Boolean Union
The Boolean Union, on the other hand, will delete all the unnecessary internal surfaces of the 2 object formed. It will only retain and merged the existing surfaces outside.
Figure 1.3.1: Combining 3d model using the Boolean Union
When to Use Boolean Union?
You can use the Boolean Union method if:
- you want to print a filled object
- you want to print an object with no visible internal structure
Note: If you intend to print a filled or closed object (with no visible internal structure) always use the Boolean Union operation and NOT Combine.
- Correcting Vertex Normals
A polygon have two types of normals. The vertex normals and the face normal. By default, all polygons have a face normal direction. But many polygon meshes don’t have the vertex normals.
Vertex normals define the way how your model is built. Which faces are facing outwards, what’s in the front and back of the surface. In order for your 3d model to be printed, the gcode generator needs to know which side of the surface is the outside (for smooth and high quality extruding) and which one is the reverse (for filling).
Figure 2.1: Checking Vertex Normals in 3d model
- Your 3d Model must be Water-Tight
For models originating from animation, gaming, VFX foundations, one thing to keep in mind is that your model must be watertight. Watertight is a term often used to describe a 3d mesh that is suitable for 3d printing. It means that your 3d model should enclose and should have no holes, cracks, duplicate vertices, or missing features on the mesh.
It’s as if your model can hold a water in its interior space, without spilling out. Continuously check your model for unwelded edges, lines, vertices and loose faces to make sure your model is ready to 3d print (see checklist below). An example of watertight check is shown in the figure below.
Figure 3.1.1: Checking Watertight in a 3d Model
You will know if your 3d model is watertight and is ready for 3d printing if:
- It has no one dimensional planes,shells or extruded edges
- No double sided faces
- No self intersecting faces
- No open faced holes
- No unwelded verts or edges
About the Author:
Bobby Lin is the co-founder of the recently launched 3d designing and printing crowdsourcing website, Mylocal3DPrinting.com. Mylocal3DPrinting.com is an online work platform that centers on 3d designing and printing industry and it aims to help 3d entrepreneurs have their prototype created by an international pool of exceptional 3d designers at a relatively affordable crowdsourced price. If you are an entrepreneur that needs a prototype created, or a designer on the lookout for awesome projects proposed by 3d entrepreneurs, you can visit our website Mylocal3DPrinting.com and post your project for free.
Bobby Lin is also interested in video production jobs and video editing jobs. And because of his passion for video industry, he will be launching his own website soon, called Valoso.com, which aims to help business leaders have their video concept created by an international pool of exceptional video creators and video editors at a relatively affordable price.
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