3D printing opens the door to an entirely new way to reuse your existing 3D content. But 3d printing is also a new type of printing paradigm with its own limitations and requirements.
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There are five basic guidelines or rules we suggest to get the best results out of your 3D printing:
- All normals are pointed in the same direction
- No holes or open geometry
- Object surfaces all have thickness
- No overlapping edges or geometry
- Target 600,000 to 800,000 polygons
These guidelines apply no matter what 3D package you are using; all examples here are using Shade 3D ver 14.
New in Shade 14.1.1! Shade 3D Printing Assistant lets you diagnose and solve almost all issues in preparing 3D models for 3D printing. Look for the yellow box for information regarding 3D Print Assistant.
Shade Master IKEDA designed Hanako over five years ago, and it was never designed for 3D printing. It would be very difficult to print Hanako as a 3D resin model and get near perfect results. I am going to illustrate using these five rules and 3D print Hanako, taking you through each rule, step-by-step.
3D Printing Rule 1: All Normals Pointed in the Same Direction
In the case of Hanako, which has loads of optional clothing, hairstyles and fingernails, you want to use the Switch Joint to locate and remove anything you don’t want to 3D print.
Here, we are using OpenGL display and looking only at the head, body and basic bikini.
*If your graphics card doesn’t support this level of OpenGL display, then you can confirm this using single sided display (Viewport menu View Display > Display > Single Side) or normal display, and setting view properties to display Normals (Viewport menu View Display > Display > Show Normals).
This makes it a snap to check the direction of normals with relatively low polygon models. You can see that red lines indicate each normal and their direction.
You can see here the direction of the normals on Hanako’s head. To flip the normals all in the same direction, select the head, then from the Browser select the Flip Face checkbox to flip all the faces to pointing outward.
3D Printing Rule 2: No Holes or Open Geometry
Hanako looks like she’s all a single, sealed surface, but that’s not true. The upper neck in relation to the head and the lower neck in relation to the body are all open surfaces. This needs to be fixed.
To illustrate how this is done, lets close off the head.
Because the head is a polygon mesh, you can easily close this how by selecting the vertexes of the edge and then degenerate them to a point (menu Tools > Modify > Degenerate to Point).
3D Printing Rule 3: Surfaces Have Thickness
It is all too easy when modeling to create surfaces that have no thickness - or more technically - without any volume. But all real world objects have volume, and 3D printers require object to have volume in order to print real world objects.
Hanako has hair that looks great when rendered, but the parts have no thickness. We have to modify these in order to make sure the 3D printer has hair objects to print.
The original hair consists of are open line objects within curved surface parts, each forming is a simple strip shape. The hair appearance using a mask or “trim map” and a texture map. These objects have no thickness - yet.
Duplicate the surface Part, then convert it into a polygon mesh.
In Shade 3D, select each Surface Part of the hair group and then go to menu Tools > Convert > Convert to Polygon Mesh…, then set parameters in the Convert to Polygon Mesh dialog. Or you can select the Surface Part and then go Tools > Create > Bevel….
Treat the result like any other polygon mesh and apply the first rules.
3D Printing Rule 4: No Overlapping Edges or Geometry
Still looking at the hair, we have groups of polygon objects that overlap each other. Step by step, select each hair object and use Boolean operations to combine the objects.
In Shade 3D, select one after the next and use Tool Parameters > Target Union Source.
3D Printing Rule 5: 600,000 to 800,000 Polygons
If you have any features related to animation, such as inverse kinematics, bones, or in the case of Shade, joint parameters, you will want to fine tune your model to make sure everything is set up how you want. Check small details, such and the direction of finger tips.
With Hanako, we made some adjustments to the joint parameters in the finger tips.
With the exception of the clothing and hair, the body of Hanako is already low polygon. However if you are translating into STL format, you may want to fine tune the number of polygons by hand.
Interactively, double check your work. Some hardware begins to generate errors if STL files have more than 800,000 polygons, so keeping it in the range of 600,000 to 800,000 polygons is safe.
After you export to whatever your target format is, such as STL, you should double-check the number of polygons in the exported model.