3D Printed and Laser Cut Split-Flap Display Character

Traveling has always been a source of inspiration for me, a window into the blend of engineering and art that shapes the world’s most iconic hubs of human activity. Among these, airports and train stations have left a lasting impression, with their dynamic environments designed for efficiency, connection, and a hint of nostalgia. One element that has always captured my attention is the split flap display—the mechanical marvel that announces arrivals and departures with its signature clicking sound.

The split flap display at Frankfurt Airport, one of the busiest travel hubs in the world, stood out to me in particular. Its rhythmic flipping of characters—effortlessly combining form and function—left me mesmerized every time I passed by. It wasn’t just a practical way to communicate information but also a design statement that evoked a sense of wanderlust and timelessness. The display’s ability to create excitement and order amidst the chaotic flow of passengers resonated with me deeply.

This project stems from that fascination. Inspired by the countless journeys and the unique charm of split flap displays, I set out to design and build a character for my own split flap display. My goal was to honor this iconic piece of technology while exploring how its mechanical beauty could be adapted to modern, personal applications.

3D Printed Parts

1. PLA Filament
2. Main Housing
3. Hexagonal Shaft

Laser Cutting Parts

1. 2.8mm MDF
2. 2 Flap Spools
3. 26 Letter Flaps

Hardware Parts

1. 3 M3 Screws
2. 1 M3 Nut
3. 1 8x22x7 Ball Bearing
4. 6 8-32 Screws
5. 3 2" 8-32 Female to Female Standoffs

Electronic Parts

1. 1 Arduino Uno
2. 1 5V Stepper Motor
3. 1 ULN2003 Stepper Motor Driver Board

The main housing and shaft are crucial components of the split flap display and can be 3D printed together in a single session. This approach ensures that both parts are printed with consistent material properties and alignment. Follow these steps for optimal results:

Print Setup

1. Orientation:
2. Place the main housing on the print bed in the exact orientation shown in the provided reference photo. This orientation minimizes overhangs and ensures structural integrity.
3. Lay the shaft horizontally to maintain a smooth cylindrical surface and avoid unnecessary overhangs.
4. Material:
5. Use PLA for both components due to its ease of use and adequate strength for this application.
6. Supports:
7. Enable supports in your slicing software for the main housing to ensure proper bridging for internal cavities and overhanging features.
8. Supports will also help to print the cavity within the shaft which allows it to rotate with the stepper motor
9. Layer Height:
10. Set the layer height to 0.2mm for both parts. This strikes a balance between detail and print time while ensuring good surface quality.
11. Infill:
12. Use an infill density of 15% with a grid or cubic pattern for the main housing to provide sufficient strength while keeping the print lightweight.
13. For the shaft, the same 15% infill density is sufficient, as PLA offers the necessary rigidity for rotational forces.

Post-Processing

Once the print is complete, carefully remove the supports from the housing and inspect both parts for any rough edges. Use sandpaper or a file to smooth out any imperfections, especially on the shaft, to ensure it rotates smoothly within the housing. Printing both parts together streamlines the process and ensures that they are ready for assembly as soon as they are finished.

The spools, which hold and rotate the flaps of the split flap display, need to be precisely laser-cut for smooth operation. These spools will be fabricated from 2.8mm MDF using the provided .dxf files. Follow these instructions for successful laser cutting:

Preparing for Laser Cutting

1. Material Selection:
2. Use 2.8mm MDF as the material for its uniform thickness, ease of cutting, and strength-to-weight ratio, which is ideal for this application.
3. File Setup:
4. Open the provided DXF file in the laser cutter’s compatible software.
5. Ensure that the scale is set to 1:1mm.
6. Laser Cutter Settings:
7. Refer to the manufacturer's recommended settings for cutting 2.8mm MDF. Typical settings may include:
8. Power: Around 60–80%, depending on the laser's wattage.
9. Speed: Adjust for clean cuts, typically between 10–20mm/s.
10. Focus: Properly calibrate the laser focus for precise cuts.
11. Conduct a small test cut to verify the settings before cutting the entire design.
12. Layout:
13. Both spools are arranged in the DXF file to minimize the space occupied

Cutting Process

1. Start Cutting:
2. Begin the cutting process and monitor the machine to ensure clean and consistent cuts throughout.
3. Watch for any excessive charring or incomplete cuts, and adjust settings if necessary.
4. Removing Components:
5. After the cutting is complete, carefully remove the spool pieces from the MDF sheet to avoid damaging the edges.

By following these steps, you’ll produce high-quality spools that integrate seamlessly into the split flap display mechanism.

The flaps of the split flap display are a key feature, displaying the characters that make the mechanism come to life. As each flap is double decided with its letter and the one after, a 2-step process will be utilized. In this step, the top half of the letters will be engraved onto the 2.8mm MDF without cutting the flaps. It is essential to engrave only at this stage, as the flaps will be cut in a subsequent step. Proper alignment during setup is critical for ensuring accuracy later.

Preparation

1. Material Setup:
2. Secure a sheet of 2.8mm MDF onto the laser cutter bed. Ensure the MDF is flat and firmly placed against the top-left corner of the laser cutter’s workspace. This positioning is critical to maintain alignment between the engraving and cutting steps.
3. File Preparation:
4. Load the provided design file into your laser cutter’s software. Make sure the letters or symbols to be engraved are clearly distinguished from the cutting lines (e.g., by using different colors or layers). This distinction ensures that the laser will apply the correct settings only to the engraved areas.

Engraving Process

1. Laser Settings:
2. Use the manufacturer-recommended engraving settings for 2.8mm MDF. Typical settings include:
3. Power: Low enough to etch the surface without cutting through.
4. Speed: High enough for clean and consistent engraving.
5. Focus: Ensure the laser is focused precisely to achieve sharp and clear details.
6. Starting Position:
7. Set the laser’s starting position at the top-left corner of the MDF. This is critical for ensuring that the engraved design aligns perfectly with the cuts in the next step.
8. Engraving:
9. Begin the engraving process, ensuring that only the letters or symbols are engraved. Monitor the laser cutter to confirm it does not cut through the MDF or stray from the designated engraving areas.

Post-Engraving

1. Inspect the Engraving:
2. After engraving is complete, inspect the letters or symbols to ensure they are cleanly etched and legible.

By engraving only and maintaining consistent alignment with the top-left corner, you ensure that the design will remain perfectly positioned for the cutting step, resulting in precise, professional-quality flaps.

In this step, the flap outlines will be cut, and the bottom halves of the letters will be engraved onto the 2.8mm MDF. This requires precise alignment of the material and differentiation in the laser cutter’s settings for engraving and cutting. Careful preparation will ensure the top and bottom halves of the letters align seamlessly on the final flaps.

File Setup

1. Differentiating Engraving and Cutting:
2. In the design file, assign different colors or layers to distinguish between the engraving (bottom halves of the letters) and the cutting (flap outlines).
3. Configure the laser cutter’s settings to recognize these distinctions:
4. Engraving Settings: Low power and high speed to etch the bottom halves of the letters without cutting through the MDF.
5. Cutting Settings: Higher power and slower speed to cleanly cut through the MDF for the flap outlines.

Material Setup

1. Flipping the MDF:
2. Take the engraved MDF sheet from the previous step and flip it 180 degrees vertically so that the previously engraved top halves of the letters are now upside down and at the bottom of the sheet.
3. Positioning the Board:
4. Place the MDF onto the laser cutter bed, ensuring the new bottom-left corner of the MDF aligns with the laser cutter’s origin point (bottom-left corner of the workspace).
5. Aligning the Design:
6. Adjust the design file so that the bottom-left corner of the design aligns with the bottom-left corner of the MDF sheet. This ensures that the flap outlines and bottom-half engravings will perfectly align with the existing top-half engravings.

Engraving and Cutting Process

1. Start the Laser Cutter:
2. Run the laser cutter with the engraving settings first to etch the bottom halves of the letters. Ensure the engraving begins exactly where the top halves ended.
3. The laser cutter will then switch to cutting settings to cleanly cut out the flap outlines from the MDF.
4. Monitoring the Process:
5. Carefully monitor the laser cutter during this step to ensure the engraving and cutting are precise and aligned.

Post-Processing

1. Inspect the Flaps:
2. Once the process is complete, remove the flaps and inspect them to ensure that the top and bottom halves of the letters are perfectly aligned and legible. Check that the flap edges are cleanly cut.
3. Cleaning:
4. Use sandpaper or a soft cloth to remove any char or soot from the edges of the flaps for a polished finish.

By flipping the MDF vertically and aligning the design correctly, this step ensures that both the engraving and cutting are precise and consistent, resulting in professional-quality flaps with seamlessly engraved characters.

Assembling the Laser-Cut Spools

With the laser-cut parts for the spools prepared, you can now assemble them into a functional unit to hold the flaps. Proper alignment and secure attachment are essential for ensuring smooth operation of the split flap display. Follow these steps for accurate assembly:

Alignment Check

1. Flap and Shaft Holes:
2. Before assembly, align the two spools by stacking them together. Verify that:
3. The flap holes on both spools line up precisely.
4. The shaft hole in the center of the spools is perfectly aligned.
5. Misalignment at this stage could cause issues when inserting the flaps or mounting the spools onto the shaft.

Attaching the Standoffs

1. First Spool:
2. Take one spool and fully screw the three 8-32 standoffs into the inner three holes using 0.5-inch screws. Tighten the screws firmly to ensure the standoffs are securely attached and perpendicular to the spool.
3. Second Spool:
4. Position the second spool so that its holes align with the standoffs on the first spool. Use 0.5-inch screws to connect the second spool to the standoffs.
5. Important: Leave a gap of 1/8 inch between the second spool and the standoffs. This gap is intentional and allows for easier insertion of the flaps during the next assembly steps.

Final Inspection

1. Once assembled, double-check the alignment of the flap holes and shaft hole. Ensure that the gap left for flap insertion is consistent around the circumference of the spools.
2. Confirm that the assembly is sturdy, with no loose screws or wobbling standoffs.

By carefully aligning the spools and attaching the standoffs with precision, you ensure a solid foundation for the flaps and reliable rotation of the spool in the final assembly.

The casing serves as the structural support for the split flap display, housing the motor, ball bearing, and other critical components. Follow these steps to properly assemble the casing and prepare it for operation:

Installing the Ball Bearing

1. Ball Bearing Placement:
2. Locate the designated cutout for the ball bearing on the left side of the casing.
3. Insert the 22x8x7 ball bearing into the cutout, ensuring a snug and flush fit.
4. Double-check that the bearing is secure and properly seated, as it will support the shaft and ensure smooth rotation of the spools.

Attaching the Motor

1. Motor Installation:
2. Position the motor on the right side of the casing, aligning its mounting holes with the pre-drilled holes in the casing.
3. Use screws to securely fasten the motor directly to the casing.
4. Ensure the motor is tightly attached, as it will drive the rotation of the flaps and must remain stable during operation.

Adding the Back Screw

1. Flap Rotation Stopper:
2. Locate the bottom slot near the back of the casing, where the flaps will rotate.
3. Insert a screw into this slot to act as a stopper for the flaps. This ensures that as the flaps rotate, they hit the screw to stop in the correct position, creating a consistent display.
4. Adjust the screw so it protrudes just enough to stop the flaps without impeding their free movement or causing damage.

Final Inspection

1. Verify that all components are securely attached to the casing.
2. Rotate the ball bearing by hand to confirm smooth movement.
3. Check that the motor is aligned with the casing and that the stopper screw is positioned correctly to intercept the flaps during rotation.

By carefully assembling the casing with the ball bearing, motor, and stopper screw in place, you ensure the structural integrity and proper functionality of the split flap display mechanism.

With the spools and casing assembled, the next step is to insert the flaps into the spools in the correct order. Proper organization and careful handling are essential to ensure smooth operation of the split flap display.

Organizing the Flaps

1. Alphabetical Order:
2. Arrange all the flaps alphabetically based on the letter formed by the top half of each flap. This step ensures that the flaps display the correct sequence when the spool rotates.
3. If the order becomes confusing, refer to the original DXF file to verify the proper sequence.
4. Double-Check the Order:
5. Before proceeding, double-check that all flaps are in the correct order. Misplaced flaps can disrupt the functionality of the display.

Inserting the Flaps

1. Prepare the Spool:
2. Ensure the assembled spool has enough space to accommodate the flaps by leaving the screws on the second spool slightly loose, as instructed earlier.
3. Insert Each Flap:
4. Starting with the first flap, gently slide it into the corresponding slot on the spool.
5. Apply constant pressure to the flaps as you insert them to prevent them from popping out of the spool. Use both hands if necessary to guide the flaps evenly into place.
6. Repeat the process for each flap, maintaining the correct order as you progress around the spool.
7. Verify Alignment:
8. After inserting all the flaps, rotate the spool by hand to ensure that each flap sits securely in its slot and does not interfere with the movement of adjacent flaps.

Securing the Flaps

1. Tighten the Screws:
2. Once all the flaps are inserted, tighten the screws on the second spool to close the gap between the spools. Ensure the screws are tightened evenly to secure the flaps in place without warping the spool.
3. Check that the flaps are held firmly but can still rotate freely when the spool turns.

Final Inspection

1. Ensure all flaps are inserted in the correct order and are securely held in place.
2. Manually rotate the spool again to confirm smooth operation and alignment of the flaps.

By carefully organizing and inserting the flaps into the spool, and then tightening the screws to secure them, you complete the assembly of the flaps, setting the foundation for a fully functional split flap display.

With all the components prepared and partially assembled, it’s time to complete the final assembly of the split flap display's mechanical structure. This step involves mounting the spool and aligning it with the shaft, bearing, and motor.

Step 1: Partially Insert the Shaft

1. Prepare the Shaft:
2. Take the shaft and inspect it to ensure it is clean and free of debris.
3. Partially insert the shaft into the bearing on the left side of the casing. Push it in just enough to provide stability but leave enough length to attach the spool later.

Step 2: Insert the Spool

1. Position the Spool:
2. Carefully place the assembled spool into the casing, ensuring the flaps face outward and have enough clearance to rotate without obstruction.
3. Align the central hole of the spool with the partially inserted shaft.
4. Push the Shaft Through:
5. Gently push the shaft through the spool’s central hole, ensuring it passes smoothly without damaging the flaps or misaligning the spool.
6. Continue pushing the shaft until it exits the spool and aligns with the motor’s mounting hole on the right side of the casing.

Step 3: Secure the Shaft to the Motor

1. Align with the Motor:
2. Insert the end of the shaft into the motor’s coupling. Ensure it fits snugly and aligns correctly with the motor's axis.
3. Tighten any screws or fasteners on the motor coupling to secure the shaft in place.

Step 4: Final Check

1. Inspect the Assembly:
2. Rotate the spool by hand to ensure smooth operation and that the flaps move freely without binding or misalignment.
3. Check that the shaft is securely seated in the bearing, spool, and motor.

Completion

The mechanical assembly of the split flap display casing is now complete. At this stage, the structure is fully functional in terms of mechanical movement but does not yet include the electronics. This provides a solid foundation for wiring and programming the display in the next steps.

Now that the mechanical assembly is complete, it's time to set up the electronics for controlling the split flap display. This involves connecting the Arduino to the driver board and configuring the connections to control the stepper motor.

Step 1: Connecting Power and Ground

1. Power and Ground Connections:
2. Begin by connecting the power (VCC) and ground (GND) pins from the Arduino to the appropriate jumper cables on the jumper board.
3. Make sure the power and ground connections are properly secured to avoid any interruptions in power delivery.

Step 2: Connecting the Stepper Driver Inputs

1. IN1 to IN4 Connections:
2. Use jumper cables to connect the Arduino pins 8, 9, 10, and 11 to the IN1, IN2, IN3, and IN4 pins on the driver board, respectively.
3. These connections will control the individual coils of the stepper motor.

Step 3: Connecting the Stepper Motor

1. Plug the Stepper Motor:
2. Locate the white port on the driver board, which is designed to connect to the stepper motor.
3. Plug the stepper motor’s cable into this white port securely, ensuring all pins are properly connected.

Step 4: Connecting the Arduino to the Computer

1. Connect the Arduino:
2. Using a USB cable, plug the Arduino into your computer. This will allow you to upload code and provide communication between the Arduino and the computer.
3. Make sure the Arduino is recognized by your computer’s IDE for programming.

Final Check

1. Verify Connections:
2. Double-check that all jumper cables are correctly connected, the stepper motor is plugged in, and the Arduino is connected to the computer.

Once all the electronics have been plugged in and the board establishes a connection with your computer, open up the Arduino IDE and copy and paste the following code. Ensure you have selected the Arduino Uno as your board.

Initial Orientation

To ensure the split-flap prints out hello, rotate the spool so that A is the character showing before the code begins. Once running, the split-flap will constantly spell out HELLO.

And with that, you've successfully made a split flap character! The hope is that this will serve as a basic building block to build more complex displays like the ones I mentioned in the introduction.