eye of agamotto
I am a big fan of Marvel movies and Science Fiction in general. It has been one of the stronger forces in my life moving me towards engineering as a career. Seeing artefacts and technology made in these films and TV shows gets my brain ticking on how I could make that same thing or how that mechanism works. When watching the Eye of Agamotto work in Dr Strange I kept thinking how could I make one that works just like the movie. There is a very strong community online when it comes to Cosplay and making props, so I knew a lot of people would want to print them out once the files were available.
looking for my eye
The internet is a gold mine mixed with a rubbish dump when it comes to searching for exactly what you want. Whenever I start a project I always start by looking to see if anyone has already done what I was attempting to do. There were a few generic models of the eye from the comics which has a different look to the movie version. There were also several of the movie prop but I also thought that I could do better. When designing a prop or replica it is important to find as many good quality images as possible to construct your prop with a lot of detail. Many images that I found were too small, fuzzy, far away or taken on someones phone at the cinema. I only managed to find one good photo of a replica prop that was on display at the movie opening. So using this image I got to work in designing the assembly.
Computer aided design (CAD)
I know anyone who has wanted to get into design would know what this means. But almost everyone confuses CAD with DESIGN, I know I certainly did when I first left University and began work as an engineer. CAD is just a 3D modelling program. Just because someone knows how to use CAD it does not mean they understand the fundamentals of design. I use PTC Creo 3 as my CAD program. I use this because that was what I was trained to use while at work and some years ago I purchased a full license. In my first year as a mechanical design engineer I created some horrible prototype parts which I had spent hours and days on. After all that effort I was quickly educated by my senior engineers why my designs were completely wrong and given instruction as to why. Many times I had to redesign parts over again. But it was not time wasted. Every minute, hour and day I spent challenging myself in using the program the better and faster I became later. By pushing yourself to use CAD designing your own parts you will learn much better and faster than sitting with a generic tutorial.
For the majority of my projects I will use this CAD program to show how I made my designs, but don't confuse the CAD explainations with design. Pay attention to the steps and use them on any CAD program you like.
Getting a sense of size
A photo has no real sense of size and scale. Without detailed drawing dimensions I would have to guess as to how big this prop needed to be. So using a ruler I choose a length that I would be happy with and then scaled the image I found on the internet. With the size determined I began creating an overlay sketch. This would be the basis for the entire prop and would be used in all components of the assembly.
With an overlay sketch completed I was now able to create the surfaces that would become the shell. I would only make it rough and then refine the details at a later stage. This shell began to grow and I would add details from the picture, but again because I did not have any additional measurement info I would be creating it on my own.
This project actually required a method of using CAD is called "Surface Modelling". It involves making many line sketches on multiple Datums (planes). The sketches are then brought together by blending surfaces between them which match the curvatures of the line sketches. Once all the surfaces are created they will be merged together and then solidified (become a CAD solid part). This is an advanced method of using CAD and takes a long time learn correctly. It took me over 4 years to start into the basics of this method which takes longer than straight solid modelling, but produces much more complex geometry.
Building the Assembly
As I started to design and make details into the model I could see that the final model would require several pieces (called an assembly in CAD). One technique that I use is to start off with one part (in this example the top case) and almost build all features of the Eye as one piece, then I would save multiple versions. Each version would be saved as a new component name, then I would use extrusions to remove soild material from my model. This allows me to have good placement and common alignment between parts and also give me a sense of breaking the original model into pieces. I ended up with 6 individual parts that would then take on their own features to complete the model.
I kept focusing on the large parts of the model and then towards the end I would add the fine details like grove lines on the eye lids and symbols on the outer shell. You should always leave rounds and drafts until right at the end of finishing the individual parts of your model as these do not make robust features to make references to in your CAD.
I thought and researched for a long time on how I would make the eye open and close like the move. I spent a lot of time on Thingiverse looking for other areas where people had made 3D printed moving parts. One design stuck out to me very strongly – The Venus Box. It uses a cam mechanism to operate is own curved box opening. The mechanism was very fluid in motion and so I looked to use a similar CAM concept. However, space was at a premium so I would be scaling it down and plus I needed to work out where the CAM slides and rail would be.
In the end I placed the CAM rails under the eyelids and the sliders in the rotating part. On my Zortrax m200 printer at the 0.09mm resolution the opening and closing worked just fine. The CAM operates by having the slider balls inside the rail grove on the eye lids. The rotation made by the user’s hand on the Inner Eye component is translated into rotation on the 2 eye lids both rotating in opposite directions to each other so that they open and close.
But I have noted that with printouts from people in the community they were not as successful on operating the mechanism. This is mainly due to the tolerances and resolution of other machines. However, looking back on this design now I would probably look at designing some form of geared rotating piece. This would lead to less wear on the parts over time and make a more robust part.
Prototyping – FMD 3D Printing
This model was designed to be 3D printed using an FDM (Fused deposition modeling) printer. I wrote a lesson plan for High School Students to understand this technology and chemistry. You can download it here (Lesson Plan – 3D Printing and Plastics).
When I designed the parts I kept in mind the semi-flexibility of FDM materials for allowing the Inner Eye to be assembled in the sliding grove which requires a slight bending to insert. I also broke up the components into individual pieces so that they were optimized for printing on an FDM build platform.
A great video of printing, painting and finishing this model was created by Uncle Jessy on Youtube.
This has been my most downloaded model so far on both Thingiverse and Pinshape. Cosplay models usually have a large fanbase so I was not surprised by this. Download it for free and enjoy, I would love to see your prints.