Picture of Giant Inflatable Robot
Otherlab has been doing a lot of inflatable fabrication lately, and we thought it was about time to write an Instructable about it.  What better subject to inflatable-ize than the Instructables robot itself?  Here's the high level view of the fabrication process.
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Step 1: Design 3D model and decompose into panels

Picture of Design 3D model and decompose into panels
For us, the first step to constructing an inflatable is designing the 3D model using a CAD program like AutoCAD or Solidworks.  Using artistic license, we added a third leg to make the robot more stable.  Further, inflatable shapes tend towards a sphere when inflated, so some allowance must be made.  For example, to prevent the legs from splaying we pointed them inwards.

With the model in hand, we use Rhino (available as a Work In Progress download for Mac) to unroll "developable" surfaces which lie flat and can be sewn together into the original model.

Next, we need to add 10 mm seam allowances and arrange the parts onto printable pages.  Using Illustrator or Inkscape, we can take the DXF output of Rhino and use 'Path Offset' to add seam allowance.  The panels with allowances can be arranged manually to fit on printable pages.  This method works well but can be really tedious with many panels.  

As an experiment, we read the output of Rhino and programmatically added seam allowances and nested the parts on paper stock.

Step 2: Print panels and cut them out

Picture of Print panels and cut them out
Now we print out the panels with seam allowances.  We used a Roland Versacam with 48" bed, but any printer will do if you tile the panels across multiple pages.  After printing, the tiled pages can be cut and taped together.

Once the panels are printed, we need to cut the shapes out of the fabric.  For small parts, you can cut the paper and fabric in one step, but for larger ones it is often easier to cut the paper first.  Use weights to ensure the paper pattern doesn't slip around on the fabric while cutting.
vanduzco1 year ago
Could you please elaborate more about the flattening process in rhino? Are you using any especial plug in?
superpants3 years ago
Have you got any recommendations on what type of polyurethane to use for the bladder or where to obtain it?
otherlab (author)  superpants3 years ago
Hi Mike, Thermoplastic polyurethane (TPU) is tough to get your hands on. We used 6 mil (.006") thickness, but depending on your use, you can go up to 20 mil. Macmaster sells very small quantities. You could try following up with one of the manufacturers listed here. We obtained our roll by talking to a major distributor and buying from one of their industrial customers.
I'm working on another project that also requires TPU that's 6 mils thick. Macmaster only sells 15 mils and up.
I heard that the bladder inside a football is made of TPU. Any other ideas on where I could scavenge for TPU?

Thanks, Ryan

PS- Your info on TPU has already gotten me further than hours of googling, so thanks a million!!
bob shea3 years ago
Is there a less expensive 3D program available? Could you create this in sketch up if need be?

Probably a dumb question, but I am new to 3D.
Give 123D a try!
Honus3 years ago
That is super cool! What type/weight of fabric is used for the envelope?
otherlab (author)  Honus3 years ago
We used 18 oz. for heavy-duty parts and 10 oz. for intricate parts.  It's a PVC-coated polyester as used for tarps.  We bought it here.
excellent work, can facilitate the filing ed rhino, 3d separation as illustrated in one of the images that you see all the parts for the esamblaje and the file should be printed on plotter to cut and make the templates, I intereza much your idea, you just have to be supplemented to provide a better use, it occurs to me, placing resistant bases and to include real wheels on the feet to include at least two engines to do remote shooting, using all the lighter elements possible to avoid compromising the stability or decrease the size of the robot additionally occurs to me to write a space in the belly, kind transparent window where you can place a laptop or mini laptop according to the firmness you may have, I say this to show some messages or add sound to the robot, (your idea of cushions or airbags as muscle is also very good, would have to see that maybe the chance for deploying a small cylinder of compressed air inside the doll) so I imagine it spinning within a shopping mall as part of an energy-saving advertising campaign, please send me information by mail or Esponda here, thanks
Honus otherlab3 years ago
Edgar3 years ago
I wish I had a Dollar for every Inflatable Santa this Instructable will sprout, this Christmas, that's a huge great idea!
...And did I mention, Videos, please?
Edgar3 years ago
Kiteman beat me to it, but stil...
Video, Video!
Lindie3 years ago
Very cool! Great job!
I actually spent part of my senior sculpture project in college working on inflatables and I have to say, not all fabric is built the same. In fact, very very few are air tight, even if they "feel" like a bouncy castle or those inflatable Christmas Santas. The bladder idea is genius because I just covered my fabrics on the inside with sealant and didn't always get the best results.
mikeasaurus3 years ago
Kiteman3 years ago
Robot punching bag?

That requires a video!