While I was working with the Mauldin High School engineering students, one of the seniors, Stefan said that he and his dad were working on an old Kawasaki motorcycle.  The button for the horn was broken and they couldn't find a replacement.  Using an AutoDesk Cad program, I'm not sure which one, Stefan created a 3d model based on the broken button that they pulled off the bike.  We sliced and printed it 3mm black ABS and he took it home, only to find that it didn't quite fit.  We took the .stl file he had, and imported into GoogleSketchUp.  We made three or four different versions of the button, each with minor dimension and shape differences.  He took them home and this one worked perfectly.  I'm not sure how long he worked on the original design file, but we spent about 30 minutes tweaking it and another 15 minutes printing them.  #Abstract2Actual ca. 2:00

One of the Senior engineering students at Mauldin High School wanted to showcase his design skills by creating a custom plaque that he could take with him off to college.  I have no idea how long it took him to design, but It was very detailed, so I imagine he had a lot of hours in it.  The print time on this plaque was four and a half hours.

To make the lettering and emblem stand out, I switched out the filament on the fly when the print job got to the last flat layer of the plaque.  It turned out really cool.

We used 3mm orange ABS and 3mm white ABS for this project

My Airwolf3d v5.5 is based on the open source Prusa-Mendel design.  Much of today's 3d printing is founded on the concept of a "free" self replicating rapid prototyping machine, a.k.a. reprap.  Not only is the software used  to run the machine freely available to the public, in many cases, the hardware designs are too.
Free, in this context, doesn't mean it doesn't cost anything.  It just means that anyone is freely licensed to use, copy, study, and change the software in any way, so long as they comply with the license terms.  I donated to Slic3r and Pronterface, two of the opensource projects that I regularly use.  I was also compelled to find a way to give something back to the community since I was getting so much from the people who make free 3d printing possible.
I decided to take my Airwolf3d v5.5 and use it to help the local high school engineering students build a 3d printer of their own.  I knew that they had an engineering program and that they used 3d modeling software as a part of their curriculum.  They were able to design lots of things, but were limited to building puzzle cubes with wooden blocks.  It was the only affordable build option they had.
I purchased an Airwolf3d v5.5 kit for the school, We used my printer to print out the structural components, gears, mounts, etc, in school colors.  We also re-designed a custom electronics case with the school name on it.  They named their machine JOOS.

In the middle of printing parts for the 3D printer, the students wanted to know what other kind of things they could make with this machine.  We took a detour to thingiverse.com and the students picked out this model to build. Thingiverse is a great website where you can share and download 3D designs.

Now that I had a machine that could produce custom designed parts, I had to find an affordable design program.  I had used a trial version of Autodesk Invent in the past, but it was cost prohibitive for someone who is just playing around with ideas that may never amount to anything.  I found Google SketchUp which is free for personal use.  I really like the tutorials on the SketchUp learning page.

They start you off with the very basics, and within a couple of hours you can be designing moderately complex things.  I don't know if my earlier experience with AutoDesk was a help or a hindrance.  On one hand, I understood the basics of 3d modeling, on the other, I expected there to be tools for what I considered basic functions like countersinks, chamfers, and threads.

The printing time for the base component shown above is 5:25.  The bulk of the design time was figuring out how the actual size of the printed holes vs. the theoretical hole size in the SketchUp model.  Another challenge was the countersink of the the holes.  A theoretical 1/4-20 screw fits into a theoretical 1/4 inch hole quite nicely.  But when you actually print it, they don't work so well.  Tolerances and clearances have to be built into the design.

I was thrilled that I got my little test blocks to print.  So I decided to try and print something a little bigger.  It was just a 3 inch square block about a half inch thick with some beveled edges and screw holes.  I tried to print it many times, but it would get about half way through the build and the extruder would jam up. I tried and tried and tried, but to no avail. I figured there might be something wrong with my file, so I decided to go with a "known good" source file.  I broke down and printed the gear set that Airwolf3d suggested I print in the first place.

Great news, the gear set printed, without a hitch!  Bad news, I must be doing something wrong with my own design files.  Back to the books I went and I learned lots of things.  Different plastics melt at different temperatures.  You can define this when you "slice" the file before printing it.  There are about a hundred other parameters you can define when you slice the file.

So what is slicing?  That is the process of translating a three dimensional CAD file (usually in .stl format) into commands that the printer controller can understand.  The file that the printer controller reads is called a gcode.

Airwolf3d recommended I use an open source slicer program called Slic3r.  Looking at all of the things you can control there was a bit overwhelming, but I eventually learned where to fine and set the basic parameters such as temperature, speed, and slice thickness.  Airwolf3d also provided me with some prebuilt slicer configuration files that worked with my 5.5 printer.  These configurations were the basis of my work, and I just tweaked them here and there as I learned how to use the features.

It was two weeks of trial and error, mostly error, before I successfully printed anything.  This first functional part was a mirror hanger.  This is a 1.5" X 1.5" X 0.0625" square with a rounded top to act as a hinge.  It was a very simple part, but the hard earned knowledge I acquired building it will take me a very long way.