Introduction: PENTOMOLOGY Display

By plus.google.com/1026325120530230

I like entomology displays but I love absurd humor this project combines both in that it answers the question "What is the inside of a crystal clear pen like ?"

This Instructable will detail how to create the design using the free and open source softwares FreeCAD and Inkscape

This Instructable is sponsored by the company JUSTWAY that provided the 3D print at the heart of this project.

Supplies

  1. Computer with Freecad (free) and Inkscape (free)
  2. Cork sheet (at least 13x18cm)
  3. Clothespins (~10)
  4. Pliers
  5. Access to transparent/translucent Resin 3D printing (I have used the online services of Justway)

You can download the 3D model directly here

Step 1: Designing the Tip End

  1. In the "Part design" workbench, create an Hexagon shape about 7.3mm across (between 2 parallel sides) with a 4mm diameter hole in the middle
  2. Extrude this shape 20mm
  3. Create a 9° filet on one side

Step 2: Designing the Folding Out Section

The angle between 2 consecutive sides of an hexagon is 120° and we want to completely open the hexagone which is to means progressively getting the angle from 120° to 180°

  1. In the "Part design" workbench, create an Hexagon shape about 7.3mm across (between 2 parallel sides) with a 4mm diameter hole in the middle
  2. Create 6 datum planes parallel the the original hexagon face, these datum planes should be 3mm appart from one another
  3. On each datum plane, create a progressively more "open" hexagon. We have 6 datum planes, creat the open hexagon with 130° angles, then 140°, 150°,160° and 179° (the last one is 179° not 180° because I could not find a way for the "additive pipe" tool to work with the angles being 180°)
  4. Select the schematic on the first datum plane and the schematic on the last datum plan, use "additive pipe" and in this tool menu, choose "Section transformation->multisections", clic on each schematic on each of the datum planes

Note: this "Folding out section" is identical in my design on both ends of the pen but you could change them as you like

Step 3: The Middle Part

This part needs to look more "organic" than the rest of the pen, Freecad is not the best tool for this, I prefer to use a different tool: inkscape. We design this part flat on inkscape and then we import it in Freecad to make it 3D

  1. Create a random shape keeping in mind that in the final display, the sides of the pen should look as if it was actually stretched on the "dissection table" but it also has to "naturally" connect to the attached "folding out" part which are 25mm wide. For this, in Inkscape, I have used the "pen tool" to create the basic shape using lines with sharp transitions
  2. I selected all the summits of the shape (called nodes in Inkscape) and I rounded them off using "Node tool->Make selected nodes smooth"
  3. I also drew hole shapes and placed then on the shape where pin would have streched the "pen skin"
  4. Perform a boolean operation between the holes the original shape "Path->Difference"
  5. Save as SVG file
  6. Import the shape in Freecad: File->import->your_image.svg->SVG as geometry
  7. Select all the imported path
  8. go to workbench "Draft" then use the tool "Draft to sketch", this creates a sketch
  9. In the "Part design" workbench, create a body, drag and drop the created sketch
  10. pad the sketch 1.5mm

Step 4: The Butt End

In BIC pens, the butt end hold a small plastic part that indicates the color of the pen. This design also has to accommodate for this part

  1. In the "Part design " workbench, create an Hexagon shape about 7.3mm across (between 2 parallel sides) with a 4mm diameter hole in the middle
  2. Pad this shape 20mm
  3. Create a bigger hole on one side 6mm in diameter
  4. Cut this hole 8mm deep



Step 5: 3D Model Assembly

In a new file in Freecad, in the the "Part" worbench

  1. Import all the parts (5 in totals with 2 different instances of the "folding out" part)
  2. Move/rotate them as necessary to achieve the desired design (right clic->transform)
  3. Perform Boolean "union" operation on all the parts (assemble 2 parts at a time)

Step 6: Display Assembly

I bought a picture frame with a 13x18cm display space. I removed the glass and on the frame back I stuck a sheet of 3mm cork (I bought the cork in the form of a roll with a sticky side). The 3D model is held only with clothespins to resemble entomology displays, I mixed and matched the colors of the clothespins and I have used both color-headed clothespins and "headless" clothespins. Since 3mm cork is not that thick, it is required that the clothespins are inserted with a narrow angle.

Pinning the pen is quite easy because the holes are already there, it is a different story for the pen cap, if you choose to have it in the display, using pliers makes piercing the the thick plastic of the cap much easier.

Step 7:

I have had parts 3D printed in metal or sls plastic before, but the reason it made particularly a lot of sense for this project to use the services of justway is that they offer transparent resin printing ! It allows the model to come out perfectly clear just like the BIC pen I was trying to imitate !

Beyond "just" the transparent resin 3D printing services Justway offer, they also have numerous different processes of 3D printing available ! Such companies open up a lot of possibilities !

Justway offers 3D printing services but also multi-axis CNC machining, sheet metal, injection molding, vaccum forming etc. I have only used their 3D printing services as of now but I can think of a lot of projects that their other offering would be perfect for !