I'm a third year year industrial design/mech eng student studying in Australia (fun :-) ), and for a recent assignment, we familiarised ourselves with the movement known as redesign - a collaboration of product designers who endeavor to take used components/materials, and make new products from them in a sustainable way (http://www.redesigndesign.org/ is a main website if you're interested).
My personal project, therefore, was to prevent the purchase of plastic P.E.T water bottles by devising a cup that was convenient and portable to carry around and use every day (after all, in many places, the health standards are higher for tapwater than bottled). Moreover, it had to be long lasting, easy to clean, recyclable, and able to hold the hot uni-cafe coffee I inevitably need, after staying awake all night working on things like, well, this.
The result is a cup that can hold more than a can of soft-drink when full, yet is about 2cm thick when flattened, and fits easily in a pocket (it can also be looped securely onto a belt). The shape does not transmit heat to the hand easily, and best of all; it's made mostly from the polypropylene covers of used folders where the spine had broken. I write this instructable in the hopes that others may also manufacture one, and I intend, with time, to refine this project further.
Step 1: Materials
- Polypropylene plastic sheet, approximately 0.5mm thick. If you wish to adhere to redesign principles, I got mine from a marbig folder that had split along a seam- you can use any brand or translucent colour that has a flat section larger than 23cm x 26cm.
NOTE: It's important that the plastic is PP as it has 'living hinge' fold characteristics that allow it to be continuously bent without eventually snapping. Check the recycling code - it should have a 5 in the middle of the recycle symbol, and PP underneath it. If you can't, try going to: http://www.modernplastics.com/how_to_identify_plastics.htm
Step 2: Tools
- a scalpel or stanley knife
- a metal ruler
- a thick, dark pen or marker
- double-sided tape
- a soldering iron, preferably with a 4mm wide chisel tip
- access to an objet 3D printer, or similar rapid-prototyper machine - I know this is very unlikely, so I could either supply the part that requires it, or you could improvise, using some acrylic rod for the material, and a metal lathe to shape it(more detail later).
Step 3: Template for Fold Lines
Without going into too much detail of the design process, the idea was initially inspired by research done, in part, into collapsing cylindrical structures by Taketoshi Nojima (you may be interested in his paper: Modelling of Folding Patterns in Flat Membranes and Cylinders by Origami).
If you take this template and use a photocopier or printer to scale it to 22cm high (top line to bottom), then you will have a template of the exact same size as mine. Alternatively, you may wish to scale down the whole cup - it's a relatively simple operation. Whatever you do, print it out, or draw it on paper with your dark marker.
Step 4: Obtaining the Plastic Sheet
Step 5: Applying the Template to Plastic
You then need to take up your scapel again, and cut along the outline, MINUS the tabs (ignore these and cut staight down the fold, they aren't needed). Following this, grab the metal ruler and use the corner to score along all the mountain and valley folds. In early models, I flipped the plastic and scored mountain and valley folds on opposite sides, but I found that as long as scores were made, the plastic would fold either way easily.
The rationale behind the metal ruler is that some trials with a scalpel or soldering iron occasionally went all the way through - as you can imagine, holes aren't a good feature in a cup.
Step 6: The Folding Commences
When you've got the whole sheet creased, you have to start accentuating the folds so the diamonds start to close up. This is easiest if you start at one of the acute corners and work your way across the sheet. As the pictures show, you end up with a tube that has a spiral gap down it's length.
Step 7: The Seam
With your soldering iron in hand, try to pinch the cylinder so the edges of the seam align. Do this for ONE panel at a time, or it'll be pretty much impossible to line up. Using the chisel tip of the iron, run it down the touching edges to fuse them together. This essentially becomes just another fold line. Do this all the way down, and the cylinder should end up with a spiral, zigzagging seam that acts as just another mountain fold line. Now to add the top and bottom...
Step 8: Bottom, Top, and Strap for the Cap
Again, I have provided a template for this - have a look. As with the previous one, it can be made to any scale to suit a personal cup, but if you're building to my specs, then the hexagon in the plan should be inscribed in a circle of 68mm.
The strap coming off the top hexagon (with the cap on the end) is designed so that it wraps fully around the bottom of the cup and plugs into the top, sealing the cup, and holding it in compressed form. Therefore, the first section of the strap should be the compressed height of your tube (in my case 2cm), followed by the width of the cup (for me, 6.5cm), followed by another depth, then a final peice with a hole cut out to accomodate the central cap.
The cup can also be closed when extended to form a travelmug, the strap forming a carry handle.
At this stage, use a marker to draw the plan, and cut a top (with strap) and bottom out the plastic. Line it up and fuse the edges as before with the soldering iron. Not much to go now...
Step 9: The Cap
I fully realise that it's hard to find facilities that do this, and probably expensive (mine was AU$7.80 at cost price, which is about a 5th of what a company would charge), so I would suggest that you turn it out of acrylic rod on a metal or hobby lathe - not particularly hard, given the simple shape. Either way, let me know, and I can e-mail out a dimensioned CAD file for a range of programs.
One particular advantage of the rapid prototyped part is that when I refine the project into a commercial product, the cap could easily have personalised embossing, specified by the individual buyer or corporate reseller.