Introduction: GNK-USB Power Droid

Earlier in the year, I asked "the Internet" for a USB charger in the form of a "GNK Power Droid" from Star Wars. For those who may not know, GNK (pronounced "gonk") droids are secondary characters spotted in background scenes throughout the Star Wars universe, walking around as mobile power generators. (For more information, see

Unfortunately, the Internet didn't respond to my request for a "Power Droid" to power my Droid, forcing me to join the "Maker Movement" and create one for myself.

This Instructable covers a few major steps in its creation using AutoCAD and an Objet 3-D printer, courtesy of Autodesk and Pier 9.

Step 1: Reference Material and Scale

To begin, I needed to create a digital model in the likeness of a GNK. A cursory search on-line yielded plenty of imagery, from movie still frames, video games, toys, and of course home-brew projects like Halloween costumes. The creativity and interpretation across the legion of Star Wars fans inspired many different styles and variations of GNKs, with little definitive source material. In fact, there were very few drawings that could be scaled and referenced to offer guidance to build a 3-D model.

However, I found one image (above) which showed a GNK in front and side elevation, with a silhouette of a protocol droid providing scale. I also found an image (above) of a 3-D model that I believe corresponds directly to that drawing, but couldn't identify the source/owner. That, combined with an on-line reference that GNKs are about 1.1 meters tall, were all I needed to serve as reference material to build a model.

I also decided to use an Anker compact portable "lipstick" USB charger as the power source for the GNK. It's about 4" long, which helped determine approximate scale, as the GNK model had to house the charger cleanly in its body. Ultimately, I decided on creating the GNK at 1:6 scale, matching the scale of Hasbro's line of large 12" line of Star Wars action figures, which would make the GNK roughly 7" tall.

Step 2: Digital Model

With my reference material in hand, and my scale determined, I set about building a 3-D digital model of the GNK. I used AutoCAD 2013 with its robust solid-modeling tools. Other CAD, BIM, or modeling packages would work as well, but as an architect using AutoCAD since 1987, it's the tool I know best.

Having inserted and scaled the reference imagery, I proceed to draw, extrude, carve, and shape the GNK as you see in the above images.

Ultimately, I wanted the legs to be flexible, so I created the model with two materials in mind, one rigid and one flexible. To feature some details, I used the flexible material as "trim" pieces as well. In the ACAD model, you see the rigid body material in yellow, and the flex material for legs and trim in blue. These were kept as separate objects.

Also, anticipating that this would be a relatively heavy object, I hollowed the body out. To remove the support material that would come with the 3-D printing process, I carved up the body into 3 pieces vertically as well: a bottom with legs, a belt line, and a top.

With this object separation vertically and by materials, I had 5 "objects" in my model: bottom rigid, bottom flexible, belt-line rigid, top rigid, and top flexible. After a fair amount of finessing and fussing, I was ready to print!

Step 3: 3-D Printing

To 3-D print the model, I used the top-notch fabrication facilities at Autodesk's Pier 9. I chose their one of their seven "Objet Connex 500" 3D printers because of its relative ease of use, specifically selecting one with rigid white and flexible black resin loaded.

In AutoCAD, I used the "STLOUT" command, creating separate STL files for each of my five components as described in the previous step. I checked the fidelity of the STL files using Meshmixer, and then loaded them into "Objet Studio," the primary software for preparing the model parts to print.

Use of Objet Studio, as well as the Objet Connex 500 3D printer, is a topic well-covered in other Instructables, so I'll skip those details here.

The model took approximately 14 hours to print, and of course another several hours to clean the and wash the support material. Above you can see the printed components, cleaned and ready for assembly.

Step 4: Final Assembly

With the major components 3-D printed, the assembly has been pretty straightforward.

First I inserted the Anker portable charger into the cylindrical hole. I hadn't planned enough tolerance for it, so it is a fairly snug fit. I planned for this by modeling a small hole in the back, with which I can push the charger out using a jewelry screwdriver or 1/16" drill bit.

During the cleaning process, one of the cables/hoses that connect the feet to the body broke off. Luckily, it was easily re-attached with super glue!

Then, the major components (top, belt line, bottom) were easily glued together, producing the final assembly pictured above.

Step 5: GNK-USB in Action

The final product turned out every bit as good as I hoped it would!

With the portable charger firmly in place, I can charge my GNK from my laptop, and in turn use it to power my mobile devices in style. I have a Samsung Galaxy Android phone, so in fact, I use my new "power droid" to power my Droid!

Other images above show a 1:6 Jawa for scale (action figures sold separately!), details on the body, and the flexible legs in action.

Step 6: Next Steps

There are a few things I would consider changing for the next evolution of this project.

  1. Enlarge the hole which houses the charger. It really is a tight fit, and I need to build in a bit more tolerance for easy insertion/removal
  2. Universal (?) adapter to accept other chargers. Anker's charger is just fine, but there are several similarly-sized compact chargers on the market I want to accommodate as well. I'd like to consider creating a bigger opening, and 3-D printing a set of adapters to fit into that opening to accommodate a few common brands/models of chargers.
  3. Blended materials. Many of the details on the white rigid body are lost in the photos. With the Objet 3D printer, custom materials mixed from the white rigid and black flex can be used, creating shades of grey, semi-rigid materials. I'd like to play with these to highlight more of the details.

Finally, and perhaps the most important future step, is that I've inspired the next generation of "makers" in my family. This year, my oldest son has chosen to be a GNK for Halloween, and he is already dreaming of what he'll make with the 3-D printer at his school!