"ATIS-Minder" 3D Design & Modelling

3D Printing Brief: "ATIS-Minder" Cockpit Dial
Project Summary
Design and model a functional, two-part rotating dial (an ATIS-Minder) used by pilots as a visual memory aid to track the current ATIS (Automatic Terminal Information Service) broadcast letter (A–Z). The design must prioritize tactile quality, clear readability, and stable operation in a vibration-prone environment.
I. Functional & Dimensional Requirements
Feature Requirement Specification
Overall Size (Max) Compact for cockpit use. Outer Diameter: $50 \text{mm}$ to $60 \text{mm}$ (Choose optimum based on design)
Total Height (Max) Low-profile assembly. Assembled Height: $\approx 10 \text{mm}$ to $15 \text{mm}$
Rotation Front Dial Disc must rotate smoothly on a central pivot/shaft. Movement must be high-friction (stiff) to prevent free-spinning during flight vibration but easy to adjust manually.
Lettering Must be clearly visible and high-contrast. Embossed or Engraved letters A–Z (skip I, O), evenly spaced. Depth/Height: $\approx 0.5 \text{mm}$ to $1.0 \text{mm}$.
Pointer/Indicator Fixed reference point. A clear, contrasting pointer must be integrated into the Backing Plate or be a fixed component above the dial face.
II. Component Breakdown (Must be Separate STL Files)
1. Front Dial Disc (Rotating Part)
o Circular face with the full ATIS alphabet (A-Z) around the perimeter.
o Designed with a central bore/recess to fit onto the pivot shaft of the Backing Plate.
o Must include a feature (e.g., small knurling or slight ridge) to aid manual grip and rotation.
2. Backing Plate / Mount (Fixed Part)
o The stationary base for the entire unit.
o Must incorporate the Pointer/Indicator design.
o Must house the pivot shaft/post for the Front Dial Disc.
o Attachment Cavity: Design a shallow, recessed cavity for a round magnetic disc (e.g., $10 \text{mm}$ diameter $\times 2 \text{mm}$ deep) for mounting. The exact magnet dimension must be specified in the CAD notes.
3. Friction Element (Optional Separate Print)
o A thin washer or spacer (e.g., $\approx 0.2 \text{mm}$ to $0.5 \text{mm}$ thickness) to be placed between the two main parts to ensure rotational friction.
III. 3D Modeling & Printing Specifications
• File Format: Deliverable required as .STL (Stereolithography) and/or .STEP (Standard for Exchange of Product Data).
• Dimensional Accuracy: All holes/shafts must account for a clearance fit of $0.2 \text{mm}$ to $0.4 \text{mm}$ to allow for free rotation after printing.
• Print Optimization: The parts must be oriented and designed for standard FDM (Fused Deposition Modeling) printing with minimal or no support structure required for clean features.
• Material Target: Design for use with PLA+ or PETG.
• Aesthetics: High-quality finish expected. Curved surfaces should be modeled with sufficient STL resolution (e.g., Chordal Tolerance $\approx 0.1 \text{mm}$; Angular Tolerance $\approx 1^\circ$) to avoid visible faceting.