3-D Printing for Non-Engineers: Rapidly Prototyping with Rapid Prototyping Machines
3-D Printing for Non-Engineers: Rapidly Prototyping with Rapid Prototyping Machines
3-D Printing for Non-Engineers: Rapidly Prototyping with Rapid Prototyping Machines

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    As part of our annual IP3 Awards (this year is our 10th anniversary so it is a roast!) (and tickets are still available!) we are planning on showing off Public Knowledge’s very own Makerbot 3D printer.  However, we had a problem.  The 3D printer works by pulling plastic off of a spool. IP3 is a rollicking affair, and we cannot be sure that there will always be someone there to spin the spool. Therefore, we needed something that would hold the spool of plastic and feed it to the printer.  Could we 3D print a solution?

    Thingiverse, a website that serves as a repository of 3D printing designs, was the logical first place to look.  Thingiverse users are incredibly talented, and are certainly more competent to design anything than I am.  And there are a number of great solutions for holding and feeding plastic on the site.  Two in particular caught my eye, so I downloaded the files and printed them out.

    These were good solutions, but they were not perfect for us.  The larger one bolted exactly onto the top of the printer and sturdily held the spool of plastic.  Unfortunately, it held the plastic a bit too sturdily.  The printer could not pull the plastic freely – it still required someone to spin the spool every few minutes to keep the plastic flowing.  The smaller one was a better fit for the spool, but did not bolt cleanly onto the printer.  Also, the upper walls were a little thin, so when I printed them they were too fragile. 

    That left one obvious option for an attorney with no engineering background to speak of: design my own.

    Although what I need seems simple, there are plenty of places it can go wrong.  First, it needs 4 holes properly spaced and sized so that it can be bolted onto the printer.  Second, it needs to hold the spool high enough to clear the front of the printer.  Third, it needs to hold the spool firmly enough to support it, but lightly enough to allow it to turn freely.  All of these things can be addressed in the design stage, but also need to be tested in the real world.  This is especially true because I did not really know what I was doing, significantly increasing the likelihood of an idea-to-design-to-reality “translation error.”

    My first step was to make sure that I had the hole spacing right.  Makerbot 3D printers come with a number of extra holes drilled in them that make it easy to attach new things –assuming the new thing matches up with the holes.  I did some measuring, fired up Sketchup (free software that is pretty easy to use and can be used for designing 3D parts), and designed my first prototype focusing on the hole spacing.  Once it looked close, I printed it out.

    As luck would have it, I got my hole spacing right on the first try.  However, the holes were a bit too big.  Our Makerbot kit came with a bunch of extra M3 screws that I planned to use to attach the holder to the printer.  The holes needed to be big enough to allow the bolt to pass through while small enough to allow the top of the bolt to secure the holder. 

    What size would be just right?  I was not sure.  Fortunately, I had 4 holes to test it with.  For my second prototype I reduce the hole three times, giving me four different size holes.  I also cut a side of the prototype to allow it to fit onto the top of the printer.

    It turned out that the first size reduction was the right one.  I sized all of the holes accordingly and printed out another version just to make sure resizing did not screw up the alignment.

    The base was functionally done.  However, the two designs I downloaded from Thingiverse before had a feature that I was feeling confident enough to reproduce.  The holes were actually different diameters at different depths, allowing the bolt to be recessed into the holder.  I needed to print another prototype to make sure that the spool could clear the front of the printer, so I decided to print it with the fancy holes.

    With the base fully done, it was time to start thinking about the walls that would actually hold the spool.  Here I ran into a problem.  The diameter of the base was small enough to fit on the top of the printer, but also just about as small as the interior of the spool.  That meant that it would not hold the spool high enough to clear the front of the printer. 

    For the next prototype I added three arms to support the spool, and the walls to hold the inside of the spool.

    Good news, the arms worked.  Bad news, the walls were a bit on the “too firm” side and would not allow the spool to spin freely.  Time for the 6th version.

    With this one, I had it right.  The walls were the right size, the arms held the spool, and the holes matched up with the printer.  It was time to print out the full holder and bolt it onto the printer.

    And that was that.  The spool now sits firmly (but not too firmly) on the top of the printer, feeding it automatically.  The printer can run without constant attention, and the spool will not fall and break (er, again).

    Perhaps more importantly, even I (someone without a technical background) was able to bring the holder from idea to reality in an afternoon of designing, testing, and revising.  I got real feedback when it worked and did not work.  It was easy to make changes to the design on the computer and see those designs become real products that I could test with my hands.

    So come on by to the IP3 awards and check it out.  Or go to Thingiverse and download the file to print – or improve – yourself.