How to Prepare your Render/Animation Model for 3D Printing - Part 1 of 2
Written by: Laurie Berenhaus
For everyone who has experience creating digital models for renders, animation, visual effects, etc., you have many things to consider when creating your models, such as poly flow, preparation for possibly rigging your character, blend shapes, color/normal/displacement maps, etc.
Expert 3D Animators that are new to 3D printing have expressed their frustration in uploading their geometry straight to the printers. This tutorial is designed to help bring your models ready for animation, ready to be 3D Printed.
In this lesson, we are going to go over the principles necessary to prepare your render/animation-ready model for 3D Printing. This lesson is software agnostic, and is an important overview for any animator to print in 3D. Part 2 of the series will take you through, step-by-step, a model from design to print.
- Design for Your Material
- Design for Real World Physics
- Making Your Mesh Water-tight
- Be Careful of Protruding Appendages/ Thicken Vulnerable Areas
- When Needed, Hollowing Your Model with Escape Holes
- Separate and Interlocking Parts
- Remove any Smoothing Modifiers
- Export in Readable Format for Printers
- Print and Share!
1. Design for Your Material:
In animation software, your model exists in a world without gravity or physics. For your model to exist in physical space, you’ll need to keep the material’s characteristics in mind. Our design guidelines by material explain material characteristics, detailed printing specs, tolerances and design tips. To better understand the strengths and weaknesses of a material, it can sometimes be helpful to see the printer in action -- here are some videos that showcase the process well:
Which material should you choose?
It depends on the characteristics of what you’re trying to print. Many designers are looking to print an animated character in full color.
2. Design for Real World Physics:
Take the time to review how your model’s weight will be distributed. If you want your model to stand by itself and not topple over, make sure the bottom of your model has a strong grounding. Maybe your model needs a base, thicker legs, or multiple points of contact on the ground to hold it up.
Size your model to fit your needs and the printers. When we say “Maximum Bounding Box,” in our Material Design Guidelines, that is how large a model can be printed in the given material. Size is especially important for prints that fit together like puzzles or are worn, like rings.
Because of casting processes, certain materials may experience shrinkage. Brass, Bronze, Silver, and Steel, may experience shrinkage during production of &plusmin; 0.125 mm. Ceramic prints shrink about 3% when fired in the kiln and expand outward 1.0mm from being glazed.
Based on material, your model’s size might shift during production. Therefore be sure to make allowances ahead of time in your model file, so your print fits accordingly.
Pro-tip: It helps if you have a grid visible in your 3D modeling software to confirm size. In some cases, units found in a modeling software do not sync up with real world units. You may have to adjust your settings or re-scale your model in Netfabb.
Some specific tutorials to learn more by 3D modeling software:
3. Making Your Mesh Water-Tight:
A water-tight mesh is achieved by having closed edges creating a solid volume. If you were to fill your geometry with water would nothing leak out? Check your normals and make sure they all face outward. Any flipped normals will be read as holes by the printer. You may have to clean up any internal geometry that could have been left behind accidentally from booleans.
Normals facing out:
No internal geometry left behind from booleans:
4. Be Careful of Protruding Appendages/ Thicken Vulnerable Areas:
Outstretched appendages from the core of your model might snap off during or after printing, if the point of contact or joint is too thin. In 3D Printing, these appendages can sometimes be referred to as wires.
For example, if you are printing a character, pay close attention to wrists, shoulders, neck, and ankles. During the production process, some materials are very delicate (like a sandcastle) when just printed and can also break during handling or cleaning. In some cases, an air blaster is used in order to remove any support material. Will your model survive this process? You might need to re-consider the pose of your character in order to bring appendages back to the core to create supported wires over free wires. This will add to the strength of your model.
Here is an example with arrows pointing towards vulnerable areas, such as where the cat’s tail connects to the body, the thin ears, and legs, etc:
5. When Needed, Hollowing Your Model with Escape Holes:
The price to print your model is mostly based on the volume of material used. Hollowing out your 3D model
can help you save on the expense of your print.
When printing with Shapeways, your model is created in a tray full of support material, such as wax for our Frosted Detail or plastic nylon powder for our Strong & Flexible Plastic. It is best to have an escape hole so the excess material can be removed, which we re-use in future print batches.
This is especially necessary for Strong & Flexible models that are dyed (such as Coral Red, Violet Purple, Hot Pink or Royal Blue) because if excess powder is trapped inside your model, the model will not dye evenly. It is important that the escape holes are large enough for the support material to escape. If the support material cannot all be removed at first, it may leak out during the dying process, contaminating the dye and ruining the batch.
Visit our Materials Page to review the needed size for escape holes in each material. For example, our Design Guidelines for escape holes in Brass is 4.0mm diameter for one escape hole and 2.0mm if you have two or more:
Pro-tip: You can attempt to print your walls based on the minimum allowance of what the material can handle, but with larger models or models with a more complex design, it is possible that those walls will crack. For extra support, it is suggested to create walls thicker than the minimum.
6. Separate and Interlocking Parts:
3D printing uniquely allows for creation of intricate, interlocking, movable pieces without assembly. The level of intricacy and detail that industrial 3D printers can produce is unparalleled. We encourage you to experiment with different types of joints and mechanisms so your finished print can have moveable parts. A great example of this is Theo Jansen
If your finished product is meant to be larger than the size of the printer bed, or if you are looking for something to assemble like a puzzle or toy, you can create separate parts that can interlock after printing. See World’s Smallest Cube or Modibots.
If you are creating separate or interlocking parts, make sure there is a large enough distance between tight areas. 3D Printing production such as SLS, makes moving parts without assembly a possibility, that wasn’t there before. Take advantage of this strength, by creating enough clearance that the model’s pieces do not fuse together or trap support material inside. This can lead to the dying issue mentioned earlier when escape holes were discussed.
8. Remove Smoothing Modifiers:
Unlike hard-surface modeling, when creating organic forms in a 3D modeling software, you usually start with a low poly mesh for easy changes and fast building.
To create this high-poly feel with a low poly count, you typically use a smoothing modifier for faster render time. Each software has a different name for this setting: Maya has Nurbs, 3DS Max has Curves, Lightwave has SubDs, etc. This does not present any issues during rendering or animation, however 3D printers do not read smoothing modifiers. Thus, designers need to remove them and raise your sub-division level to re-create the illusion smooth modifiers offer. Now your model has a higher resolution.
Pro-tip: If your 3D model is referencing a UV Map for a texture map, be mindful of altering your geometry. Depending on your 3D modeling software this may be an issue. Try creating a UV Map after you have sub-divided your mesh.
Here is the same geometry with and without a smoothing modifier:
Now maintain the illusion of the smoothing modifier, by sub-dividing your mesh:
9. Export in Readable Format for Printers:
Modeling software typically has a format that is native to their own program. This is great for saving your work in progress, however when you are ready to export your model to be printed, you need a readable format. Shapeways accepts designs in STL, OBJ, X3D, DAE, Collada or VRML97/2 (WRL) for color information. STL is most common and in some cases a plugin may be needed to help you export your file depending on your 3D modeling software.
10. Print and Share:
Now that you have your file ready to go, upload it to Shapeways and send it to our printers. Words cannot describe how excited I was, when I opened my first package. When your model has printed, share it with your friends, fellow CG artists, and fellow Shapies on the Forums
. By getting more eyes on your model, you may inspire others to create something new or get feedback from other modelers on your design.
The process to prepare a 3D model for printing is often unique to everyone, but hopefully these guidelines provide a foundation for you. Stay tuned for Part 2 of the series, where I take you step-by-step through an example - my model of a Sphynx Cat that I had originally designed for a render.
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