Introduction: Proto_Taut: a Foam Stretching Machine

Proto[taut] is a form finding machine evolved around material elongation. It works with natural qualities of viscous and pliant materials such as phase change, tension, expansion and gravity. The Proto[taut] fabricates assigned geometry while looking at the complexity of multidirectional structural systems formed by elonging forces.

Proto[taut] is designed and built by two architecture students, Yuliya Grebyonkina and Ryan Uy, from California College of Arts in San Francisco. The studio course was called Creative Architecture Machines (Fall 2013) and the studio instructors were Jason Kelly Johnson and Michael Shiloh.


These are the items you will need for this project:

Machine Body:
Laser Cut Pieces out of 1/8" & 1/4" Acrylic
Ball Bearings for Lazy Susan

Two 12v, 1.6A, 233 oz-in Geared Bipolar Stepper Motor
One 3v, 1.7A, 68 oz-in Stepper Motor
Arduino Uno Microcontroller
Quadstepper Motor Driver Board
(Optional) Arduino ProtoShield
12v power supply
Hook-up Wire

Material and Tools:
Great Stuff Insulating Foam Sealant
Mini Spring Clamps
Water Spray Bottle
Cleaning Scraper
Zip Ties
WD-40 Lubricant Oil


Laser Cut pieces are used. The parts of the machine include 2 side walls, 2 motor-driven blocks, a tilting upper stamp platform, and a rotating bed.

The 2 motor driven blocks are composed of gears that climb up and down the side walls.
The two blocks are bridged by a tilting mechanism(the upper platform). The upper platform holds the top acrylic stamp.

The rotating bed is the part which holds the bottom acrylic stamp. While the upper platform climbs up and tilts, the bottom bed can rotate to any degree, or stay stationary.


The Body
This machine does not use a single screw and is entirely put together by zip-ties. The laser cut acrylic pieces interlock and are reinforced with a zip-tie that crosses through multiple holes. This system enables fast assembly as well as disassembly. Use the large back wall piece as a guide for spacing for the rest of the parts.

The Side Walls and Blocks
Next, assemble the side walls and the 2 motor driven blocks. Pieces of acrylic dowels were used to secure the blocks. You can use a soldering iron to flange out the acrylic dowel end as a stop. Slide the blocks into the side walls and lubricate the gears as necessary.

The Top and Bottom Platform
Next, install the top tilting platform which bridges the 2 blocks. Use zip-ties here to secure the arms to the blocks and an acrylic dowel for the sliding mechanism. Finally, install the bottom rotating bed. You will need to create a Lazy Susan with the ball bearings, which allow for a more frictionless rotation.


Shown in the diagram is the proper way to wire the stepper motors. Each motor is assigned its own channel on the quadstepper driver board. A protoshield can be used to replace the breadboard. Link the Arduino and your computer with the usb cable. Power the Quadstepper Motor Driver with the 12v power supply.


Rhino3d, Grasshopper, and Firefly are used to control the Arduino and the Stepper motors. The machine can be used to build individual foam artifacts. Moreover, it can build column-sized pieces out of a number of artifacts stacked on top of each other.

First, a curve is drawn in grasshopper. The curve is broken down into segments and each segment is calculated for motor steps, giving the two geared stepper motors a destination in the Z. The two stepper motors climb to their Z-destination, raising and tilting the stamp upper platform resulting in a proper angle for each segment.


Stamp Material
Apply the insulation foam onto laser cut acrylic stamps. You may use any material for the stamps but we found that the foam sticks best to acrylic.

Foam Initial Shape
We experimented with many shapes such as circles, square, and quadrofoils in order to find the most structural result. We learned that certain shapes cure differently from others. If the shape does not allow equal curing to all parts, the foam will fail and will be too wet in the middle and not stretch.

Foam Amount
The amount of material also matters. If you apply too much, it will cure more unevenly. If you apply too little, there will not be enough material to support the structure of the artifact. We had most success with the "square with diagonal" pattern with 3 levels of foam as it was the best balance of equal curing and material support.


After you apply the foam into the stamps, wait 20 minutes for the foam to cure before it can be properly stretched. Experiment with varying the wait time slightly for varying textures of the artifact.

Prepare to load the stamps into the machine. Raise the upper platform using Grasshopper to allow you enough room to install the stamps. Next, load the upper and lower stamp. You can use mini spring clamps to secure the top acrylic stamp onto the upper platform. The bottom rotating bed holds the bottom acrylic stamp with a clip.

When ready, lower the upper stamp down into the bottom stamp. The foam will begin to get sandwiched. Wait one minute to allow the foam to fuse together. Raise the upper platform very slowly to start the stretch. Raising the material too fast will cause it to rip.

When the two blocks reach their final height, wait another 20 minutes to allow the foam to dry. Spraying water on the foam with a water bottle sprayer will speed up the drying process. When dry, you can undo the spring clamps and remove the artifact from the machine. Use a cleaning scraper to clean up any messes.