3D Print Project

This post is about designing and printing an object with a 3D printer. It will cover what software was used to design and print, along with the parameters of the project. This post will also cover the types of materials, mainly plastics, that were available to use.

The main constraints for this project was that it needed to be designed by the student and fit within 1.5 x 1.5 x .25 inch box. Dr. Harris suggested some 3D modeling software such as SoildWorks or Tinkercad. I choose to use another software called Creo. I am currently using Creo in my Engineering Graphics class, so I am already familiar with it. Here is the process:

The first step was to sketch the design. The design is the final dimensions, except for height. This sketch is not included, as the one below is a better example. Once the paper sketch was completed the design could then be put into Creo. The design needed to be finalized before starting in Creo. If you are going to use Creo, you need to know exactly what the design is. As mentioned in previous posts, Creo is a not meant for creativity. Here is the first Creo sketch:

Sketch 1. This does show the dimensions.

The design was fairly simple. First a 1.5 x 1.5 inch square was sketched out in Creo. The design consists of a backwards 'E', a 'P' and the a small 'S'. This stands for my initials, EPS, and is effectively my monogram. The main pieces are 1/4" wide which makes the two gaps 3/8 x 5/8 inch. The 'P' was also simple. A circle was made with a diameter of 3/4" and then two lines were made. These two lines were made tangent with the circle and then this shape was connected with the backwards 'E'. A concentric circle was made with the center point of the larger with a diameter 1/4" and the same process was repeated.

Once those steps were done, the 'S' was next. This was difficult because I did not know how to make a letter in Creo. As it turns out, there is a text option. Choosing the font for the 'S' took the most time, about 10 minutes.

The next step was to extrude the sketch. This was done with the extrude tool. The overall thickness needed to be 1/4", so the logo was extruded to 1/8". Here is the extruded sketch:

Extrude 1, this was 1/8"

There needed to be a base in order for the 'S' to stay in place. This was done by making another sketch on the bottom face. This was also a 1.5 x 1.5 inch square.

Sketch 2, Creo can be hard to use, that is why it is sideways.

The sketch was then extruded 1/8" making the final piece 1/4" thick.

Extrude 2

There are a few limitations with a 3D printer, such as sharp corners. 3D printers handle smooth or rounded corners better than sharp ones. The four outside corners were smoothed with the round tool, the radius was set to 1/8". It was a simple matter of clicking on the corners to rounded. The model took an hour to complete, a small part of a free evening. Here is the final model:

Final model

Once the model was completed it needed to be saved to the correct file type. The default file type for Creo is a '.PRT', but the 3D printer software needs an different type such as a '.STL' or '.OBJ'. This was done by selecting 'save as' and then choosing the file type. The file type used was '.STL'. This was tricky, the part does need to be selected and then saved. A .STL file basically saves the model as polygons and simple shapes.

The printers in the FabLab are on a server. One of the laptops in the FabLab had to be used in order to access the server. Once this was accomplished, the printer could then be selected.

The printer that was used is a Printrbot Simple. This printer seemed to give good results and was simple to use. The Printrbot takes a code called 'G-code'. G-code gives the printer points or concordats to follow. It is accomplishes this by slicing the model into .8 millimeter slices or layers. In order to turn a .STL or .OBJ file into G-code, a third-party program had to be used. One of the TA's recommended a software called Cura. Cura is convenient because the model of printer is selected and then the file is loaded into Cura. The model is then positioned in Cura and then printed.

There were two different options for the printing material, known as filament. This filament is 1.5mm thick, comes in spools and a variety of colors. The two types of plastic available were ABS and PLA. ABS is the classic plastic, Lego bricks are ABS. PLA is a corn based product which will eventually degrade. For this process, Dr. Harris wanted the students to use PLA as these are first prints and in case of any mistakes. PLA can go into a landfill, but if ABS is used, your mistakes with literally last forever.

Here is the print in process with purple PLA filament:

Beginning of print

Approximately 1/3 done

Printing progress bar

Approximately 3/4 done

The overall print time was 45 minutes. The printer took 10 minutes to heat up and then 35 minutes to print. This printer gave fairly clean results. There were three other printers running at the same time and those were not printing nearly as cleanly. The results are decent, especially for a first print. Here is the finished piece:

Top-down view

Slanted view

There are still lines on the print, which could be sanded smooth. There is a trick with ABS to remove the lines on the piece. The piece is suspended over acetone bath in a sealed container. The acetone vapors react with the ABS plastic, acetone will dissolve ABS. The process does not take too long, maybe 45 minutes to an hour. However, this process can be sped up if the acetone is heated. This would create more vapor. It is recommended that you read this article as it goes into further detail. This article does talk about using an acetone bath which would accomplish the same effect.

Since this piece is simply a rough piece, more a proof of concept, it does not need to be finished. There was some basic clean up, a few thin strands of material from the print head. You will also notice that the curves are not smooth. This is due to the file type. The .STL saves the model as simple shapes, so the curves are made of triangles.

Overall, this project was quick and fun. This project took 2:15 - 2:30 to complete. The model took an hour or so to design it, another half hour to convert it and prep for printing. The overall print time was 45 minutes. The most tedious step was the print it self. It did feel like watching paint dry, unexciting.

There is really nothing that I would change, I might use ABS in a future print. I am happy with the print, and the color is not half bad either. This piece came out exactly 1.5 x 1.5 x .25 inches, which is one of the parameters. I will eventually mirror the design so that it can be used to make a sand mold and then casted in either copper or brass. This will  be used as a brand for branding various objects.

I do not wish to share these files, as they are of a private/personal nature and I do not want the them or the print to be recreated. If you do wish to obtain the files, drop me an Email.