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Digital Sculpting, 3D Printing and Animatronics

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This Instructable is going to show how to use digital sculpting software and a 3D printer to create a skin for an animatronic puppet. I am currently an art student studying entertainment/industrial design and have access quite a bit of high tech equipment, such as digital sculpting software, laser engravers and 3D printers. I was brainstorming ideas for my thesis project when I realized that there can be many advantages to using these tools to create animatronic characters. Digital sculptures are much easier to transport and use far less materials than traditional methods. Plus, it is very difficult to carry a sculpture and molds back and forth to school when riding a bicycle! They are also more accurate and (in my opinion) easier to change and refine. When paired with a 3D printer, one can be holding just about any model in a day or two. This process just one way to integrate digital and rapid prototyping tools into the design process and to eliminate some of the waste involved in bringing an animatronic creature to life, without limiting creative possibilities.
 
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Step 1: The Traditional Method

I am using photos of an animatronic eel that I recently created to help illustrate how the traditional process works. The sculpture was first sculpted and detailed. It was then molded in Ultracal 30, which is a type of plaster that can withstand the heat necessary to bake the foam latex skin. A layer of clay that is the desired thickness of the final skin is placed inside along the inner wall of the mold and more plaster is then layered inside to fill the remaining space, creating the core. After the mold and core are finished, foam latex is mixed up and poured into the mold. The core is placed inside and the mold is closed. It is then baked and the foam skin is ready. I'm not going to go into too much detail as to how this process works since there is quite a bit of info on creating molds and foam latex pieces to be found in books and on the internet. But it is important to keep in mind these basic steps though, since the digital workflow differs in a few key ways.

Step 2: Designing the Digital Sculpture

I designed the digital sculpture for this project using Zbrush 3.1. I have also used Silo, which is much more affordable (under $200 for the professional version) and offers a displacement painting feature that is similar to sculpting in Zbrush, but most 3D modeling software will work fine to create most models. I drew up several pages of sketches using Sketchbook Pro before committing to a design. I had to be sure that the printer could produce the level of detail I desired and that the creature would not be too difficult to mold. I chose a simple design since I only had a couple of weeks to get everything done and to eliminate as many potential problems as I could. I decided to produce a creature called Three-Armed Ground Leech that is was based on one of my concept sketches. The design appeared to be rather easy to mold and did not require an extremely high level of final detail, which I was sure the printer could accommodate. A small scale test print of an early sketch helped me to refine the design.

Step 3: Creating the Digital Sculpt

Zbrush has many features that make it easy to produce really great sculptures without having to invest a lot of time. Again, I'm not going to get into too much detail on how to use Zbrush, since the concepts can translate to many 3D modeling/sculpting programs. Since I knew what I wanted the creature to look like, I began by creating the core of the sculpture first. This differs from the traditional method because you must have the sculpture fully molded before you can make the core. The digital core was duplicated and was used as the starting point for my sculpture. I made sure to thoroughly check the sculpture as I was developing it to make sure there was adequate space between it and the surface of the core. Knowing that this space would eventually become the final skin, I made the sculpt thicker in areas where I did not want as much movement and thinner in areas that move more. Some of the details seen in the final rendering were left out of the final model because they could have been problematic to the molding process.

Step 4: Preparation of the Digital Files

The final sculpture and core were exported from Zbrush and imported into Rhino 3D. This was done to make it easier for me to scale the models and add registration points that would be necessary to make sure everything was where it needed to be during the molding and casting process. Both the sculpture and core shared the same origin when imported, which made it easy to check that everything was properly aligned. Identical registration columns were set the same distance apart so both pieces would fit in the appropriate place in the final mold. After the registration was added, the core and the sculpture were exported in the proper file format to be sent to the 3D printer.

Step 5: Rapid Prototyping

The finished files were sent to a Dimension SST 1200 ABS printer. It prints by layering heated ABS plastic and a support material in .010" layers. The support material dissolves away when placed in a special bath after the model has finished printing. The ABS models are durable and can be molded several times as opposed to a clay model that is usually destroyed in the molding process. This reduces material waste and can allow for several molds to be made if many castings will be necessary. If further detail is desired, you could sculpt on the surface with clay or if you would like a permanent solution, Apoxie Sculpt from Aves is great. It is a non-flammable, non-hazardous synthetic clay that sets a 2-3 hours without shrinkage. In this case, I like the fingerprint-like texture the printer left behind, so I decided to leave the model how it was. Before committing to the full size sculpture, I printed a quarter scale version of each to make sure they were what I wanted. You can see how the core and sculpture register into a test mold box.

Step 6: Molding The Sculpture

I designed the mold box in Rhino around the models and fabricated if from laser cut acrylic. This allowed me to accurately place registration points in the mold box that matched core and sculpture. I attached the sculpture to the mold box, sealed it and measured the interior volume with water so I knew how much silicone to mix up for the mold. After thoroughly drying the box and sculpture, I poured the silicone. While double checking for leaks, I noticed that the sculpture was floating in the silicone. I had to pour the silicone back out and re-mount the sculpture using a couple of screws. I poured the silicone back in and let it set for 18 hours.

Step 7: Casting the Skin

After the mold had set, I removed it from the mold box and cut the sculpture free using a razor blade. The shape of the sculpture allowed me to create a one piece mold, making the process rather simple. Next, I lubricated the interior of the mold with petroleum jelly to act as a release agent for the silicone skin, since silicone will bond to silicone. I placed the core inside the mold and put both in the mold box, being sure to securely mount the core in the registration holes. I mixed up the appropriate amount of silicone and poured it into the mold and let it set. When I removed the core and skin from the mold the next morning, I noticed that I had a hole and thin spots on one side. The hole was caused by the hasty re-mounting of the sculpture in the mold box when I noticed it was floating. I decided to modify the core sculpture and to reprint a new one instead of modifying the existing core. The castings that used the new core were much better. I tinted the rest of the castings by mixing a small amount of oil paint into the silicone before pouring them into the mold.

Step 8: Designing and Building the Mechanism

I decided to use tentacle mechanisms to give the creature movement because they are simple to build and seemed to fit the creatures personality the best. I first built a few test mechanisms out of whatever was available to make sure they would give me the movement I wanted. I designed the final mechanisms in Rhino by taking cross sections of the core mesh and laser cutting them out of some scrap acrylic. The center piece was 3D printed from a section of the same core mesh. Since all of the final pieces were extracted from the core, I knew that they would fit precisely into the skin, allowing for better movement and greater accuracy. I was able to build the entire mechanism (with the exception of the center piece and a few small sections of thin steel wire) from scrap materials that I have saved from other projects or taken out of scrap bins. This helped save some money on the project and reduced waste.

Step 9: Installing Servos and Final Assembly

Since I was building the leech for my graduation project, I mounted the mechanism to a box with an open back to show how the servos were connected. I made the servo brackets from scrap aluminum and the box from some poplar I had from another project. The cables run down the center umbilical and connect to the servo horns. Here is a video of the movement: http://www.youtube.com/watch?v=pY9mn1jmH3s

Feel free to ask any questions or for more information about the process. This is my first Instructable and any feedback is appreciated!
hed4208 months ago
I wanted to see a video of it moving with the skin on. :(
chicopluma3 years ago
we also use rhino in my college, but i haven`t used the printer yet, i think it is for second year projects
Rob K5 years ago
Our University has one of these printers not sure what model. The cost for use to use it is $4.50in3.

I have a few things I need to print but I will keep it as a surprise till then. I think they will be interesting.
Wehrdo Rob K4 years ago
I know this is really old, but I'm going to reply anyway.

That's really expensive considering at Shapeways it's only $1.50 for their cheapest material, including shipping it to your front door.
Rob K Wehrdo4 years ago
Its per CM though.

The dial from my combo lock is around 38$
Wehrdo Rob K4 years ago
Oh, my bad.  I thought you said cm3.  I would love to have a 3d printer that I could use at my school, but for now I'll have to use Shapeways.
doktorvortexx (author)  Rob K5 years ago
Can't wait to see them!!!
SinAmos5 years ago
Your Zbrush works needs work, but I feel like you wasted this opportunity. I also feel like this instructable doesn't apply to the general audience, as we don't have a 20,000 dollar piece of equipment, so you really aren't helping us here.
There's an online service (name escapes me) where they rapid prototype with this exact printer. These pieces would set a person back less than 100 dollars, shipped within a few days. I think this is an incredibly detailed account of a really cool project. ...searching....
Again, an online service, which is cool, but not really DIY.
doktorvortexx (author)  SinAmos5 years ago
You could build your own printer if you had the time. I would like to build something like this that prints in plastacine clay though. http://www.instructables.com/id/3D-chocolate-printer-made-from-LEGO/ The cost of the machines should inspire everyone to build one of their own.
a reprap or similar will only set you back about a thosuand these days, less if you already have parts. :)
Yeah reprapor fab@home are both fairly cheap options.

Fab@home costs around $2000
I think I saw somewhere that all of the RepRap parts can be bought for ~$600
getting a portion of your project manufactured doesnt preclude it from being 'diy' You DIY with metal tubing, thats manufactured. etc...
Interesting =)
waiting for a name/link
doktorvortexx (author)  Proteus5 years ago
You can contact me at: www.jameshudakdesign.com
doktorvortexx (author)  frollard5 years ago
Thanks!!! Check out my Blurb book I created for the process notebook if you want more info. http://www.blurb.com/bookstore/detail/602475
doktorvortexx (author)  SinAmos5 years ago
There are several 3D printing services that can print models in a variety of materials for a reasonable cost. One example is http://www.shapeways.com/ which does not require one to own a machine. Soon Desktop Factory will be offering a machine for around $5000 which is not unreasonable considering how prices continue to drop. http://www.desktopfactory.com/ The Zbrush model was specifically designed to be simple and since the level of finish was not as important as completing the process, I opted to spend more time on completing the rest of the work instead of creating a great digital model.
DragonX7775 years ago
good idea for building haunted house monsters
DainiusGB5 years ago
that is soo coool! if i had enough money i would totally get one of those 3d printersl!
frollard5 years ago
I uploaded your video to youtube with credits:

http://www.youtube.com/watch?v=pY9mn1jmH3s

use that link to embed it! (much easier to use!)
doktorvortexx (author)  frollard5 years ago
Thanks again!
it's great! you have much experience on this!
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