Press Fit Animal Planet

PRESS FIT ANIMAL PLANET

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Sarah Hirschman
M.Arch. 2011

I like figurines, and I like what they bring out in people, especially when they're a little bit unexpected.

You can check out two other figurine-related projects of mine here and here.

I began this project by drawing my idea out - I find that if I start drawing pieces in CAD or modeling immediately, I forget something integral to the design, or I don't think all the parts through fully enough.

Then I downloaded some images of animals for reference material, organized them so that they were basically in scale with one another, and began to trace...

I had thought that I would be able to vinyl cut all the the small details as an applique to the lasercut animal bodies, but this turned out not to be the case.

After drawing single strokes, I made sure to "outline stroke" in Illustrator, so that I would have fully solid shapes, and no strokes in my design template.

This meant that when I was finished tracing, I could "Live Paint" [a totally useful and highly used feature in Illustrator] the fields, removing any stroke, so that the design consisted solely of black and white field shapes.

You can download this .png file here.

I then exported the AI file as a .png and emailed three versions of it to myself. One was just the basic outlines for the pink foam [see below], and the other two were the detail add-on appliques. Here you can see why that 'Live Paint' tool was really useful, since the Vinyl Cutter treats strokes as thought they were outlined, rather than hairline.

I took some pink craft foam [usually a children's art project material] and applied a backing material of yellow adhesive vinyl.

Then I ran some tests. They initially came out very bad, like this one, using 90gm force and 20 speed. The monitor who was helping me, James Coleman, suggested that perhaps we needed to begin to score the material a few times, rather than plowing through the whole thing at once, and rather than bringing out the whole length of the blade at one time.

So we did a few scoring tests, finally deciding on a technique that involved one pass of light scoring, and three passes of heavier cutting.

The light first pass settings, using a .5mm blad depth, were 20gm force, and speed of 2.

The next three passes were with a blade depth of 1mm, a force of 60gm, and a speed of 2. This brought the blade right down to lightly scoring the vinyl backing material.

Many of these pieces had to be pulled out and cleaned up manually, however, since the geometry was quite tight and the pieces so small.

You can download the "just the outlines" file that I used for the vinyl cutter here.

Next, it was time to test out tolerances for the press-fit connections on the lasercutter, using 3mm-thick masonite, which is basically a wood composite sheet material.

I identified three different types of connecitons in my designs - the hinge joint, the v-in-v joint, and the plug joint, so I tested all three of these in different configurations to see what worked best where.

You can download this test sheet in .dwg format here.

Because the pieces of masonite I bought at the store were only 24" long, and not the full 32" of the laser cutter bed, I made sure to indicate that on my AutoCad cutsheets, to make sure I didn't go off the cutable material.

I used the suggested masonite settings of Laser Power: 85%, Speed: 7%.

Strangely, the machine read-out actually indicated that the speed was 9%, so I started to add a percent or two to my sent settings, so that the machine would read for what I was going for.

As it turns out, I needed about four passes of the lasercutter to make a clean cut through the masonite.

When the pieces were ready, I was easily able to tell what connections would work for this material, generally squeezing connections by about 1mm in two directions.

I went back through my cutsheets (prepared earlier from the AI file), and adjusted all the tabs. I find when adjusting for tab tolerances that it's easier to think about connections as involving one sort of piece, rather than two. For example, if I had a plug-in connection, I would adjust only the plug, rather than the tab that fit into it. This made it easier for me to keep track of what I was doing.

You can download these two cutsheets as a .dwg here. Please note that I was a tiny bit careless, and many of the insertion tabs were not trimmed after I adjusted their sizes, meaning that there are some corners with overlapping curves.

Also please note what I discuss below - if you're going to use these files, you might want to better account for some space for the slides in the short sides of the box.

My connections were perfect and tight, but not too tight, for almost all aspects of the construction, except for one important part. In the top side of my slider-box, I was planning on layering two pieces of masonite to create tracks for the animal-holders to slide through. I miscalculated and ended up tighenting up these ocnnections in error, which meant that in order for me to slide the sliders effectively, I needed to cut the outside edge of the box. Boo.

The great unsung hero of this project is the rubber mallet. My connections were designed to hold fast, which means that for the most part, they aren't connections I could have made with just my hands, or with constant pressure along whole edges. This rubber mallet served me well in getting everything in line.

During laser cutting of the animals, I began to notice that after a couple of passes, small pieces in my design started to be getting much smaller very quickly.

I don't think these problems would have arisen if the box were just larger overall, perhaps 50% larger, but as it was, some pieces, such as tails and ears were physically about five or six millimeters wide. Many of them fell by the wayside.

Once my "stages" were lasercut, I affixed scenes that my animals might find themselves in to them - a farmyard, a desert, new york city, and red curtains. This way, the animals can have a nice diversity of scenery and feel like they're traveling a bit.