Holy Grail Project - Re-Usable Collapsible Cup From Sustainable Materials

In brief... A 'Re-Design' project - How to make your own fold-down, re-usable cup that collapses from 16cm high down to 2cm, can fit in a pocket or clip onto a belt, holds hot beverages without burning your hand and is made almost entirely from sustainable, used materials.

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

You will require:
- 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

You will need:
- 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

In order to achieve the fold pattern of the cup around the cylindrical section, a template must first be made. I have supplied an image below that can be scaled to create a cup of any size, sourced from http://www2.eng.cam.ac.uk/~sdg/dstruct/cylinders.html. This page is also fairly compulsory reading at this stage.

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

Assuming you are using a folder for your source of plastic, you'll probably want to get one flat sheet out of it. Just grab that scalpel and split the folder along its seams. Usually you should end up with at least two large flat panels.

Step 5: Applying the Template to Plastic

Take the printed template, and double-sided tape it firmly onto the back of your polypropylene sheet. The idea behind using a translucent colour is that you can see the template through the 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

Getting the plastic sheet into a cylindrical shape is where the project begins to get a little tricky. As you know, the horizontal lines, and the lines at 60 degrees, are mountain folds, so I like to begin by folding these. Just crease each line firmly in the right direction, then open it back out . After you've done these, you have to try and flatten it back out and do the valley folds in the opposite direction. This is more difficult given the surface irregularity.

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

I'll be frank with you, this part of the project took a long time to get right and it's pretty frustrating, so if you're trying to do this at home, you may have to persevere with it. This is one part of the project I hope to refine soon, so any comments are appreciated.

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

Now that you have the collapsible part made, it'll probably need a top and bottom. The bottom is simply a hexagonal peice, but the top obviously has to have a hole for the cap and a strap coming off it that the cap is attached with.

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

The last piece of the cup is the cap that allows it to seal, whether flat, or extended and filled. Having access to a cost-price objet rapid prototyper machine at uni, and an impending deadline, I bit the bullet and had this part printed (it might also have been because it looked really cool, and I wanted to test it).

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.

Step 10: Using the Cup

If you put the cap through the hole on the end of the strap, you're done! I hope that my instructions have been comprehensive enough to achieve this - if not, let me know - so all that's left now is how to use the cup. I believe the best way to convey this is via the sequential images below. Enjoy, and happy building.