Monthly Archives: January 2015

Making Moving Parts with a 3D Printer

3D Printers are getting more common, and are REALLY cool, but how do they work? In principle, it is quite a simple science. Most 3D printers use a plastic filament, and have a nozzle that heats up to about 200 degrees C (about 400 degrees F). This melts the plastic as it passes through the nozzle, known as an “extruder”. The 3D printer is told by a computer where and when to move its nozzle and dump out the hot melted plastic. The plastic rapidly cools, and leaves a solid behind as the extruder moves on to lay down more plastic.

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The extruder will start at the bottom and make all of the things it needs to at that elevation (known as a layer), and then move up to start the next layer. Not terribly complicated. The extruder knows where to go because of a 3D file that is run through a program called a “Slicer” that decides what to do at every layer. The printer continues this process for every layer, building the entire thing from the bottom up. The unsliced file for the spinning rings seen in the video is on the left.

This allows for some cool things! These rings are one of the coolest things we have made. You may be able to see in the image above that there are some cone like pieces sticking out of the inner rings and into the outer ones. These act like axles. They cannot be cylindrical, because the 3D printer goes from top to bottom. With cylindrical axles, there would suddenly be a layer where something would be built with nothing under it to support it resulting in scary conglomerations of plastic resembling monsters from bad science fiction. Using cones in this way solves this issue.

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As the printer makes its way to these axles, it prints the layer shown above. You can see the cone and the recess being formed. As the printer continues on its way, these will be locked in place. This allows that entire spinning ring assembly to be printed as a single item! In fact, it can’t be taken apart without breaking the entire structure! Understanding these constraints on 3D printing allows for some very interesting challenges, and ultimately some incredibly cool designs! Check out those spinning rings again. Can you see the axle cones?

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These printers aren’t just for making cool designs. NASA is currently using a brand new 3D printer in orbit aboard the ISS. One of there astronauts needed a wrench, so they sent him the design file, and he made on on board! They even shared the plans for this wrench, allowing us to print our very own!

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Space Rocks!

Space is a place of extremes.  We have extremely large objects like stars and extremely small objects like dust particles in a stellar nebula.  And then there are the objects that are more in the middle.  A good example of these in between objects are comets, asteroids, and meteoroids.  However, when these rocks come into contact with the Earth, their impact can definitely fall into the extreme category.  Literally, space rocks.

There have been many famous impacts over the course of human history.  One of the more recent examples was the recent fireball that exploded over Chelyabinsk, Russia.  The main part of the meteor broke up a few miles above the city and the resulting shockwave blasted the glass from windows all around the city.  The size of the meteor was estimated at about 20 meters across and a weight of about 12,000 metric tons.  The amount of energy released when the meteor exploded was about 20-30 times the atomic bomb dropped on Hiroshima.  Because the Chelyabinsk meteor broke apart before impact, the signature crater that defines a meteorite hitting the Earth was never formed.  But there is a very famous meteorite crater found in Arizona.

The Arizona meteor crater was formed by an impact that occurred about 50,000 years ago.  The crater is about .7 miles across, which puts the estimate for the size of the meteor at around 50 meters, more than double the Chelyabinsk meteor.  Luckily no humans were around at the time of the impact or there would have been serious amounts of damage.

Fortunately, a large meteor impact has never happened in our lifetime, however scientists theorize that an impact large enough could have global consequences.  In the Yucatan Peninsula, the Chicxulub Crater crater measures at an enormous 110 miles in diameter.  The meteor that caused the impact was likely around 6 miles in diameter!  The impact was so powerful that dust would have been thrown so high in the atmosphere that it would have spread to the far reaches of the Earth.  The dust would have absorbed a good amount of sunlight from reaching the surface of the Earth, which would have caused a lowering of the Earth’s global temperature.  If the temperature change was extreme enough, it is likely that many of the species on the planet would not have been be able to adapt to their new environment and would have died.  We call this a mass extinction event.  Scientist continue to studies meteors in hopes of better understanding and predicting impacts.


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