Wednesday, September 16, 2015

Paper Construction for Prototyping.

Paper construction has become an integral part of my prototyping process.  In fact, I begin almost any 3D modeling and fabrication project by first creating a paper mock-up.

Here is a brief tutorial, for beginners, to show the actual construction process.

**This tutorial assumes that you have already created a paper template.  There are many useful tools for creating flat templates, including Pepakura Designer, 123D Make, Rhino's flatten commands, and other CAD platforms that include sheet metal feature such as Autodesk Inventor or Solidworks.  Personally, I use Solidworks to create flat patterns because of its very intuitive sheet metal operations - and because that's generally where I do all of my 3D modeling.

Here, I have created a template for a simple box.  An over-sized matchbox, if you will.

I start by printing the template to scale, and mounting the paper to .3" cardboard. To mount, I use LOCTITE light-duty spray adhesive - this is tacky enough, but still re-positionable if I mess up alignment.

Shake the spray adhesive for a good 15 seconds before using.  Apply in a spraybooth or a well-ventilated area.  Often I do my spraying-of-things outdoors, if it isn't too cold or windy.  Here I'm using the spray booth at my University.

Here is a quick video demonstrating how I apply the adhesive.

Just a few light passes that overlap the entire sheet.

After applying the adhesive, I begin sticking it to the cardboard by first lining up two of the corners.  

A quick video demonstrating the rest of the application process:

Slowly roll the paper down onto the cardboard, smoothing it out with your hand to avoid air pockets or wrinkles.

Next, it is time to cut and fold.  You'll need a straight-edge (preferably metal), a cutting mat, an x-acto knife (sharp!), and optionally a scissors if you'd like to cut some of the simple parts of the pattern that way.

Additionally, you will need a tool to score the fold lines.  DO NOT use the xacto knife - you dont want to cut through the paper, only to slightly weaken it so it will bend where you want it to.  You want something firm and slightly blunt.  I have used a bent paperclip before - but recently I've been using a ballpoint pen.

Oh, and also you will need glue or tape if you want the thing to stay together.

I start with the outside edges.  Hold the straight edge along the line you'd like to cut.  Hold the x-acto knife firmly, just below the knurled part of the shaft.  Make sure the as you slide the blade, it is butting up against the straight edge, perpendicular to the work table.  The blade should literally slide along the straight edge, letting it guide the cut.

For inside corners, start your cut at the intersection and move outward.

For outside corners, it is best to overlap your cuts to avoid annoying little clinging corner bits.

Here I have finished cutting both patterns.  It is now time to score your fold lines.

Like I said, I often use a ballpoint pen.  They are easy to come by, and they provide a blunt surface, and the ball inside of the tip allows the tool to glide quite effortlessly, even when applying a lot of pressure.  I dont usually mind the fact that they leave lines of ink (obviously, they do) because after all, it is just a prototype.

Use the scoring tool just as you would the x-acto blade.  Apply lots of pressure as you score!

The point here is to disturb the consistency of the paper right at the folding points, so when it comes time to fold the paper does exactly what I want it to.

Here I have scored the pattern.

Next its time to fold.  If you score it properly, this part is a breeze.

Before gluing, I like to try to just hold the pattern together and make sure I understand how everything should line up.

For glue, I'm going to use one of my favorites: Krazy Glue.  It dries krazy fast, and hold very firmly. This bottle comes with a built-in applicator brush, which is quite handy for projects like this.

If you are worried about getting glue on your skin, toss on some rubber gloves!

Apply glue to tabs.

Hold glued areas firmly until dry.

And presto!  A paper thingy.

I now have a place to store my over-size paper prototype matches.  :)

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