millner [at] media.mit.edu E15-020F, 20 Ames st, Cambridge, MA 02142
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Weekly Assignments
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The Magic Maracas
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Inspiration
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I thought it would be interesting to make a press-fit object with
sides that don't meet at a 90 degree angle
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Project files
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magic maracas sDraw file dump
*in order for the maraca pieces in the files to fit together after
you cut them out, you may have to do one of two things: (1) try
changing the speed and power settings on the cutter (because the tiny
amount of material the laser blasts away can alter the press-fit
strength); or (2) tweak the "tabs" on each piece that
presses together
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Look how fun it is to shake this magic maraca!! The inside of the
press-fit maraca is full of acrylic scraps. Scraps bounce around to
make music we all know and love.
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This close up shows how all the parts fit together (parts are shown
below). It was tough to make sides that meet each other at a 45 degree
angle (that's why boxes are popular projects). I thought through how
the dimensions of many parts of the maraca would fit together (taking
into account how the laser would alter the actual size of the physical
parts). For the sides that meet at an angle, I found trial and error
(using cardboard first) useful.
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Here is a look at the bottom. Notice the clamp where the handle meets
the noise-maker. There are slots in the handle for this clamp to go
through - inserting the clamp forces the handle to expand to make a
SUPER SNUG fit into the noise-maker. This is to ensure safety in case
someone wants to use this as a baby rattle. We don't want the top
flying off and letting the dangerous-if-swallowed acrylic parts leak
out.
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In this photo, you'll see the output of the maraca's sDraw file.
Cardboard is a great way to test how the pieces fit together. It is
usually easy to find cardboard that is 1/8" thick if you plan on
using 1/8" acrylic sheets. Two things to keep in mind that the
settings on a laser cutter influence how parts fit together. For
example, a laser can move quickly over cardboard using a low power
laser (50%) and still cut it. It may take more power and slower
movement to cut acrylic pieces. Playing with different speeds and
powers alters how much material is melted away while cutting. This is
important to note because you still may have to make adjustments after
the cardboard fits snuggly (as I had to - see the picture below).
The parts shown are: tabbed noisemaker sides (8 needed); handle
slots (2 parts); top and bottom handle clamps (using 1 worked out
well); noisemaker top and bottom (the bottom has an insert for the
handle and slits tabs)
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Process notes/tips
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-tool settings: to cut a 1/8" sheet of acrylic, I set the power
to 100 and the speed to 10 on the Epilog laser cutter.
-making good tabs is an acquired skill. I relied upon keeping a
sDraw file that has each side of the maraca laid out as
overlapping rectangles that haven't been merged or subtracted yet.
When I needed to change the tab sizes, I would go to the properties of
each tab and modify the size by a millimeter or two
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Things to think about
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Cardboard gives way to pressure a lot more gracefully than acrylic
does. When I first tried acrylic with slot sizes that worked for the
cardboard prototype, the pressure I put on the handle while trying to
jam them together caused it to break. It doesn't do much for your
project, but it's a great stress reliever ;p
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