The Sky Printer is an adaptable, cable-based delta-gantry system that can span large areas with a minimal footprint. The Sky Printer is designed for large- scale applications in potentially remote locations. It can be understood as the evolution of the conventional 3d-printer.
We are a team of two architecture students from California College of the Arts in San Francisco. (team members: Thomas Monroy, Taole Chen)The project was developed in the FA14 Creative Architecture Machines Advanced Studio taught by Jason Kelly Johnson and Michael Shiloh (also check out the Digital Craft Lab which is the overarching research department at CCA).
We think the project has immense potentials that we were only able to graze in the two months we had to develop it and were surprised that no one has really attempted it before us. Although the cable-based system inherently has issues with stability, rigidity and may not be easily adapted to very precise applications, there are distinct advantage that point to an exciting future for computer-aided construction:
Within the constraints of the studio class, we focused on additive clay printing as a method to test the system, but the Sky Printer is really much more than just a printer, as we envision it to have an exchangeable tool set that would include grapplers, drills, spades, analysis tools, etc.
We'd like to mention and thank the people who have helped us, either directly or indirectly, realize this project. Being architecture students with no practical knowledge in engineering, we relied a lot on available online and offline resources:
The Sky Printer is an easy to replicate system and we will publish our findings in the following steps, in the hope that others will start picking up on the idea and develop it even further.
Step 1: Material List
Things you'll need:
If you are planning on printing with clay:
Step 2: The Tool Head
The tool head, at this point, is open for iteration. Ours simply had to be able to hold the silicone tube with a nozzle and be able to attach to strings. The images are ordered in reverse chronology, so the first one is the most recent one. Notice that in the later iterations the strings are attached to a ring, rather than a fixed point. We hypothesized that this would resolve an issue we had of the tool head not being level when moved too much in certain directions. Theoretically, it should balance out the differing heights at the three anchor points. It worked to some extent, but there's still a lot of room for development.
The bolts were used for weight. Acrylic and PLA are both very light weight, so we had to increase the weight for stabilization.
We put up process images of several rather than one single tool head, because we want to demonstrate that you don't have to rely on a specific machine to make it. Fortunately, we had a Type-A Series 1 and laser cutters at our disposal, but the first extruder was entirely hand-cut in a matter of minutes.
We included one .stl file for 3d printing and one .dxf ready for laser-cutting, but we do encourage to experiment with and design your own tool head, as ours is by no means perfect.
For example, at one point we bought a 6 DOF IMU (Six Degree-of-Freedom gyroscope+accelerometer) so we could potentially neutralize tool head wiggling, but did not have time to implement it. Due to the cable-based construction, the tool head wiggles whenever it is moving. It was also not imperative for us to solve this quirk of the system, as the wiggle actually helps when printing clay.
Step 3: The Winch Casing
Similarly to the tool head, the winch casing evolved through the course of the studio. The last iteration has two slots for bolts that you can slide around so it can hang onto a variety of ledges. You can also just bolt it down to a straight ledge or to an anchor that you can bolt/hang onto the wall.
Point is, it's actually very flexible. All you need is a method to fixate it the winches somewhere high up in a space. At one point, we just used a few clamps to clamp the stepper motors to unistruts that were hanging around in our studio.
Step 4: Wiring
The wiring is pretty simple. There is a USB port, terminals for the steppers, connection for a regular computer fan, and power.
Notice our power supply says it's an AC supply. Don't mind it, it's lying! We checked it with a multimeter and it is in fact DC. Speaking of which, always check your power supply with a multimeter before connecting to anything, especially when you're dealing with expensive electronics like the TinyG!
As for the stepper wiring, the colors will be different with every model. But Michael taught us a simple trick using a multimeter that should also help you find the right pairs every time (Bipolar steppers always have 2 pairs of wires, if it has more than 4 wires, it's not bipolar).
You are now connected!
Step 5: System Setup
The setup is pretty straight forward. Find a suitable space with three fixation points somewhere high up and a safe place to keep your TinyG. We were able to complete the entire setup in under an hour.
The hard part is calibrating the system inside grasshopper. Because we did not include any feedback sensors, the Sky Printer doesn't know where its tool head is located. So we need to manually measure out the height of the winches, the distance to each other, and their respective distance to the center point. The center point is important, because it acts as the homing origin. We needed to first find it by measuring it out physically, and then move the tool head above it and set it as origin in Gcode to achieve accurate movements.
Step 6: Understanding Software
A crucial part of the project was the coding which was all carried out within Grasshopper (it's a visual programming language). The program itself requires you to have Rhino 5, a NURBS-based modeling software which is commonly used in architecture, but also industrial design. You can download a free 90-day trial, after which you have to purchase the software.
To install grasshopper, you can download it from their website.
You will also need the Firefly plugin.
Further instructions can be found inside the grasshopper script which is included in the attachment.
Step 7: Printing With Clay
We are in a love-hate-relationship with clay-printing. The results are beautiful when they succeed, but the complexities of the material make it a very challenging project to tackle.
Step 8: Word of Caution
Compressed air can be dangerous. You will absolutely positively need a pressure regulator when working with compressed air. We didn't have a clue in the beginning, so we connected the PVC chamber straight to the air compressor. Fortunately, we didn't glue down the end pieces (which we should have done, another mistake) and once the 150 psi shot into the tube, it only transformed the tube into a cannon instead of a pipe bomb which would have caused some serious damage as we were holding the contraption in our hands. Another lucky coincidence was that we happened to point it towards the corner between the floor and a wall, so it didn't hit anyone (it only left a huge dent in a piece of MDF and a slightly bruised finger).
Also, eye protection, gloves and gas masks are recommended, as the clay can be damaging to the human body when exposed for too long.
Step 9: Clay Formula
The science of mixing clay is an entirely different beast altogether and we are nothing but kids lost in a strip club. We are absolutely clueless regarding the optimal composition of clay and found a working formula by trial and error, and with a lot of help from others who came before us. We also used a measuring cup, which measures volume, whereas clay is usually measured in weight. But it worked. (to some extent, our clay artefacts are still prone to cracking, and we were not able to fire them in a kiln: instant crack)
Here's the formula:
You would want a less viscous mix (more like a clay slip) so it can move through the hose effortlessly. We also used photo lights (flood lights or heat guns work as well) to bake the prints while they're printing, to decrease their drying time and increase stability. With this method, we were able to achieve a maximum angle of about 30 degrees, after which the artefacts started collapsing.
If you're in the Bay area, the ingredients can be purchased at Ceramics & Crafts Supply, which is located in SOMA, San Francisco.
Step 10: Material Chamber
The material chamber we put together by going to the hardware store and finding the right fittings on site. We are not putting up a component list as (a)we don't know the names for more than half of the components, and (b)the exact form doesn't matter as long as it is an air-tight chamber. For the second chamber, we have a cylinder made out of acrylic in the center, so we could see how much clay we had left in the chamber.
Step 11: The Results
Payoff for our blood, sweat and tears.
Step 12: Potential and Improvements
Technically, there's a lot to improve. We have identified a few points that would be our next steps in the development process: