This week in ENGI 210, we were tasked with 3D printing an object on two different 3D printers in the OEDK. However, these objects could not be just any object we wanted; they had to be impossible! This means that they could not possibly be manufactured or functional if one attempted to created it using a different technique. Moreover, these objects will then be packaged in small gum ball cases, piled into the OEDK’s gum ball machine, and available for purchase to all OEDK users.

Prior to this assignment, I had some experience 3D printing simple parts for my ENGI 120 project. However, I had never printed a complex object with integrated moving parts, so I was very excited to get started!

The first order of business was to sift through the Thingiverse website for a CAD file of an impossible object that could be printed on a scale small enough to fit into the gum ball shell. I liked the idea of 3D printing an animal with various movable joints. I had collected a few favorites, but decided to go with a multi-jointed impossible slug! The design was simple and small enough to curl into the gum ball casing. I simply downloaded the STL file onto a flask drive and headed over to the MakerGear 3D printing station to start a print!

When I opened the STL file in the MakerGear 3D printing program, I noticed that the total length of my slug with 11 centimeters. I knew that the object would be able to curl up to some degree to fit into a small space, but I was a little worried it was still too big for the gum ball case. Therefore, I decided to scale the slug down to half of its original size. Additionally, because the print was relatively small and simple, I decided against building a support raft under my part. I ran the print, waited roughly ten minutes, and hurried back over to the printer to collect my creation!

The print had gone smoothly, but it would not pop off of the printing bed! I had to detach the bed from the printer and bend and chisel to get my object off. It did eventually come off, but my slug did not go unscathed…

I am not sure if many are aware, but healthy slugs tend to have two tentacles on their heads, not just one :'(. I knew I would have to re-run my print due to the lost tentacle, but I also realized that I could definitely scale up on the size of my object. This first iteration fit into the gum ball casing easily with room to spare!

I simply hopped back onto the same 3D printing computer, and re-opened my slug STL file. This time, however, I scaled the initial size down 25% rather than 50%. I also added a support raft underneath my print in hopes that the extraction process would be easier and less tragic than my previous attempt. I ran the print, waited about twenty minutes, and returned to find a new slug creation!

The extraction from the raft was much easier and the new slug did not suffer any injuries in the process! After removing the support material, there was not much else to post-process on my object, considering there were no frayed edges or parts to sand down. Additionally, I liked the all white coloring of my slug and did not feel the need to alter its appearance.

I also preferred its larger size compared to my first print.

I then tested its fit within the casing only to discover that gum ball cases are perfect housing alternatives for slugs!

Now that I had one print finalized, it was time to make my way to the wet lab to tackle a higher quality commercial print of my slug! I was initially unfamiliar with the different printers in the wet lab, so I skimmed through a few of the old ENGI 210 blog posts to gain insight. I read about both the Fortus and the Objet, and decided that the Objet may be more user friendly.

With that in mind, I made my way over to the Lab Tech table to gain access to the wet lab and recruit a knowledgable partner in my slug printing endeavors! Setting up the print on the program in the wet lab was similar to the MakerGear process, but we did run into some complications. These complications lead to a much longer set up process than I had anticipated and resulted in our team doubling in size…

We finally mediated the issues by simply rebooting the program. Ha. We then successfully sent the file to the Objet and waited for the print to commence and finish!

About thirty minutes later, I removed my slug from the Objet to find it covered in what resembled slime. I realized that this excess material is the support material that the Objet creates for each job. Danny suggested that I use the low power setting on the water jet to remove it from my piece. He noted that using the high power setting may destroy the fine joints of my object. The lower setting took a little bit of time to completely remove the support material, but the pieces of my object stayed intact and it was eventually free of slime!

There is a noticeable difference in my two different slugs. One can easily tell that the Objet print is higher fidelity. I also like the glossy finish from the Objet, and the material has a better feel than the MakerGear prints do.  However, both slugs were a success, and they both fit nicely in the gum ball casings.

Obviously, these slugs are selling for 25 cents a piece in the OEDK. However, if I were to sell them on my own, a bit more thought and appreciation would factor into the price. As for time of labor, I probably worked for a total of two hours on the project, charging 5$/ hour. The Objet charged me exactly $2.10 to print my high fidelity slug. I used a number of complex machines to complete this project, including the MakerGear 3D printer and the Objet 3D printer. I consider my OEDK machine usage to be more of a rental relationship with the OEDK. These machines belong to the OEDK but are available for me to use. Therefore, in order to integrate these expenses into my final cost I have considered the fact that industry average for overhead, consisting of machine rentals, tools, etc., is 15% of the finalized materials and labor pricing. Therefore, my resulting calculations set the price of each slug at $6.96.

This project was simple, but truly a blast to tackle and complete. 3D printers are mesmerizing to operate and observe. I love the gum ball machine concept and cannot wait to share all of our cool objects with anyone who has a little extra change!