This is an instructable that will guide you through the process that I used in the spring of 2012 as part of my enrollment in Igor Siddiqui's Prototype seminar course. I worked in collaboration with Jeff McCord on this for one semester developing the concept, fine tuning and executing the production process, and final assembly.
The final prototype was selected to be displayed in the 2012 West Austin Studio Tour.
1. Create 3d model + export to printer
2. Print forms and prep for casting
3. Cast 3d form into alginate, creating mold
4. Pour casting medium into alginate mold
5. Assemble final product
Step 1: Create 3d model + export to printer
Create 3d model
In the software of your choice (I used Rhino), create a 3d form.
Notes on form:
As this is designed to be a light fixture, the goal is to create a small module with a void cut through the center of the form. This will allow a path for the light to shine through in the final fixture. My partner and I chose to create a pyramid-type form as the baseline design. We then used a single plane and sliced through the form. We repeated this process for each of the other modules, each time ensuring that we rotated the plane at a different orientation, which allowed for each of the modules to be unique from one another.
We stopped at four modules, but you could theoretically make an infinite number of these from a single baseline design.
Export model to printer
Ensure that you have clean geometries (printable) prior to exporting the model. Export to the software type needed by the 3d printer of your choice. I used a '.stl' file format to send to the printer, as that's what UT Austin's School of Architecture's digital lab printer requires.
You can create a .stl file in almost any modeling program that can generate 3D objects (Rhino, Revit, AutoCad, FormZ, Viz, 3Ds-Max, etc.).
Step 2: Print forms and prep for casting
After sending your modules to print, allow time for prints to set.
Post process models
After models have set, remove any remaining material adhered to the surface of the model. Compressed air is usually the recommended method.
Apply super glue (or other binding agent) to the 3d prints. This will create a water resistant coating on the modules, which is important for the casting steps of the process.
Note: Apply binding agent in a well ventilated area. Wear respirators for extra precaution to prevent the inhalation of fumes.
My preferred binding agent is Zap Thin CA super glue.
Step 3: Cast 3d form into alginate, creating mold
For this step, you will need alginate. I purchased mine from Smooth-On, a very good distributer of casting mediums. I selected the non-toxic version that doesn't include crystalline silica (a known carcinogen).
A good guide to follow is Smooth-On's website: http://www.smooth-on.com/gallery.php?galleryid=273
Steps for making alginate mold:
1. Begin by creating a containment field to hold alginate mixture.
2. Alginate is a powder that is mixed in equal parts with water for proper consistency. Measure out the appropriate amount of water. With 80° F / 27° C water, Smooth-On's Alja-Safe® will have a working time of 8 minutes and a de-mold time of 10 minutes.
3. Begin by pouring water into the mixing bucket, then carefully add alginate powder. Mix thoroughly in order to avoid lumps. Note: Using a drill powered turbine mixer to mix the alginate will ensure a proper and thorough mixture.
5. Submerge the 3d forms upside-down into the bucket of alginate. Hold in place until alginate sets up enough to hold form without the support of your hand.
6. Slowly and careful wiggle the form free of the alginate. Caution: removing the form too quickly can cause tearing in the mold.
7. Once the form has been removed, the alginate mold is ready to be cast into.
Step 4: Pour casting medium into alginate mold
Steps for casting modules:
1. Mix your desired medium to cast with (plaster of paris, cement, urethane, silicone, etc.). We chose to use a mixture of portland cement and plaster of paris (Rockite) mixed with water. Follow the directions for each of the mediums you choose.
2. Pour mixture into alginate mold. Allow ample time to set. Remove cast piece.
3. Apply finishing touches, i.e. sanding, etc.
Step 5: Assemble final product
At this step, you have a few options to select from, which will determine the type of hardware / lights that you will need.
One option is to affix a single LED-light module to the back side of your piece.
Another is to gang a series of modules together and mount onto a translucent panel.
In our case, we selected the second option; we wanted to create a 4x4 system for our first prototype. The image shows our 'cut sheet' of the finished module.
Step 6: Enjoy your own endless design possibilities!
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