3D Double-Sided Letters in an 'Open and Close' Sign

I love mechanisms, gears, and moving parts. So, when I saw the 3D printing filament that comes in two colors, I thought it would be fun to create a sign of a word where gears could rotate each letter to reveal another word in a different color. This is how the idea for this project was born: to create a sign that changes from "open" to "close".

Before 3D printing:

• 3D modeling software (I use Inventor)
• 3D printer
• Dual-color filament (I used a silk blue and green type)
• Black filament.

After 3D printing:

• Nails glue
• 3D printed figures
• Paint (I used metallic gouache)
• Brush

The first thing I did, was to decide on the words to use and determine which letters would be modeled together. I noticed that "CLOSE" has one more letter than "OPEN," so I started thinking about how to solve this. I came up with the idea of using a simple figure instead of an additional letter. For cases where such a sign might be used in a store, the store's logo could be a suitable option. I finally decided to use a heart, arranging the letters as follows: C-❤, L-O, O-P, S-E, E-N.

In the program you use for modeling, start by creating a square as a guide for the size of the heart and letters. In my case, I used Inventor and made a 4cm x 4cm square. However, when I attempted to 3D print the pieces, I realized not all would fit on my printer, so I scaled all the pieces down to 66% before printing them.

After creating the square, draw the additional figure there, whether it's a logo or a simple shape. In my case, I made an inclined heart, thinking that if the right side almost forms a straight line, any accompanying letter to its right will look much better.

Next, create another square of the same size, keeping the same center, but do it on a different plane. On this square, place the first letter so that the heart and the letter intersect, appearing as an X when viewed from above.

Extrude the heart in both directions so that it extends at least 4 cm or more in total.

Now the letter C is being extruded, but when performing this action, it's important to select the option for extrusion by intersection (as shown in the image)

Afterward, I created a drawing on the top part of the figure. I drew a circle that would touch the corners of the shape, and in its center, I drew another smaller circle that I'll use to create a void extrusion for the axis that supports the letter to pass through. I noted down the diameter of the outer circle on a sheet to understand the space the letter will need to rotate without colliding with another.

Now the small circle drawn for the axis is being hollowed out with an extrusion.

After saving the file, you can create a copy of it and edit the steps where the heart and the letter were placed, adding the letters of the second piece 'L-O'. If you are using software like Inventor where some steps can be edited and the rest are recreated automatically, this method will work for you. Otherwise, you will need to repeat all the steps with the new letters. 

If you are able to do it automatically, I recommend still checking the drawing on the top part, as the measurements of the corners will vary depending on the shape, and the center may also shift.

Do the same for the missing figures: O-P, S-E, E-N.

With the measurements I had noted from the circles I drew on each of the figures to understand the required rotation spaces, I identified the largest measurement and used it as a guide. I divided this measurement by two, which gave me 24mm, and I used this for creating the gears.

I thought about how to create a structure that would support everything, and I concluded that the best option was to design it in pieces. My 3D printer handles circles better when they are parallel to the print bed, and if I were to print the entire figure in one piece with circles parallel to the bed, it would waste a lot of support material. 

So, with this idea in mind, the first thing I did was create a rectangle with holes for each of the gear and letter axes.

To create the sides of the structure, I considered the height of the gears at the top and the height of the letters at the bottom.

Initially, I created the axes with the width of the holes designed in the letters and the rectangles of the structure. However, (In further steps) when I 3D printed the letters, the base of the structure, and one of the small axes, it didn't work well due to the thickness of the 3D printing layers, which caused the measurements not to be exactly as modeled. At that point, I experimented with the measurements and made new prints of the small axis until I achieved the perfect width for my printer and the printed structure and letters.

There are two sizes of axes because some will only support the gears, while the longer ones are for both gears and letters.

Next, I decided to conduct a test by creating an assembly file, where I placed all the pieces I had created so far to see how the mechanism would look.

I made a copy of the file for the large axis and modified its top section. Then, I created an additional piece (handle) to match this modification on the top of one of the axes, allowing me to operate the mechanism and move the letters.

I also made an additional copy of the original frame structure and covered some of the holes, leaving only those necessary for the large axes (where the letters go).

Next, I placed the gears on the axes, ensuring they were centered on the small axes and positioned at the same height on the large axes as on the small ones.

After positioning them as desired, I applied a bit of glue to keep them in place on the axes so that they rotate along with them.

After the glue had completely dried, I placed the axes onto one of the rectangles of the structure, alternating between large and small axes: one large, one small, one large, one small, and so on. In the center, I positioned the axis that has a different shape to hold the handle.

Then I placed another rectangle of the same shape as the one I had placed before, so that the gears are sandwiched between these two rectangles.

I applied a small amount of glue on each side and added the 'structure sides' pieces.

Then, I placed each letter figure on the axes. Once they were in the desired positions to spell out 'open' and 'close', I applied a small amount of glue to secure them. Additionally, I attached the handle on the top of the central axis, enabling the rotation of the gears and consequently the letters.

The letter 'O' in 'close' looked incomplete because of how it was cut off by the 'P', with the axis covering its bottom part. Therefore, I decided to paint part of the axis in this section to make the 'O' look complete.

Finally, I glued the bottom part of the structure (the one with fewer holes than the others) and let it dry.

Here it is! You've completed your custom Open/Close mechanism. Now, easily control how the letters display using the handle in the center. Have fun and enjoy your new project!