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1. Computer Controlled Machining

This week, I designed a bookshelf using FreeCAD and fabricated it using CNC machining. The process involved careful planning, modeling, and execution to ensure precision and structural integrity. By following a structured workflow, I was able to successfully manufacture a functional bookshelf with interlocking joints and artistic design elements.

1.1 Safety Protocol​

Ensuring safety is the first and most critical step before operating any CNC machine. The following precautions were taken:

  • Completion of CNC machine safety certification training to understand machine operations and potential hazards.
  • Reviewing emergency stop procedures and machine operating guidelines to handle any unforeseen issues effectively.
  • Wearing appropriate personal protective equipment (PPE), including safety glasses, hearing protection, and closed-toe shoes, to minimize risks during the machining process.

1.2 Bookshelf Design (FreeCAD Workflow)​

The design process involved breaking down the bookshelf into individual components, each carefully modeled in FreeCAD. The workflow ensured that all parts fit together seamlessly while maintaining a balance between aesthetics and functionality.

1.2.1 Backboard Assembly​

  • Sketch Development
    • A base sketch was created in the PartDesign workbench with precise dimensions (600 × 400 mm).
    • Finger joint connections were incorporated to enhance the structural stability of the bookshelf.
  • 3D Modeling
    • The sketch was extruded to a thickness of 18 mm, representing the plywood sheet used in fabrication.
    • Fillet edges with a 3 mm radius were added for a smooth and safe finish.

1.2.2 Side Panels​

  • Profile Creation
    • The side panels were designed as mirrored sketches (600 × 300 mm) to ensure symmetry.
    • Interlocking tabs were incorporated to improve the rigidity of the bookshelf.
  • Model Generation
    • The sketches were extruded to a thickness of 18 mm to match the material.
    • Each panel was positioned alongside the backboard, aligning with the connection points.
    • The Mirror tool was used to create an identical symmetrical pair.

1.2.3 Top Plate​

  • Sketch Design
    • The top plate dimensions were set to 325 × 400 mm to fit seamlessly with the side panels.
    • Dado joint features were added to provide a secure and stable connection with the bookshelf structure.
  • 3D Conversion
    • The design was extruded to 18 mm thickness, maintaining consistency with other components.
    • Pilot holes were added for easy hardware installation if needed.

1.2.4 Art Designs​

To enhance the bookshelf's aesthetic appeal, different artistic design elements were explored and integrated into the structure.

  • Curved Design
  • Skeleton Design

1.2.5 Shelf Components​

  • Base Sketch
    • Each shelf was designed with a primary dimension of 300 × 400 mm, ensuring sufficient storage space.
    • Sliding dovetail connections were implemented to facilitate easy assembly without additional fasteners.
  • Model Duplication
    • The shelf design was extruded to 18 mm thickness.
    • Multiple instances were created using the Linear Pattern tool for uniform spacing and alignment.

1.2.6 File Export​

  • The final assembly was converted into technical drawings using the TechDraw workbench for reference and validation.
  • 2D profiles were exported in DXF format (R12/LT98) to ensure compatibility with CNC machining software.

1.3 CNC Machining Process​

After finalizing the design, the CNC machining process was initiated to transform the digital model into a physical product.

1.3.1 Toolpath Generation​

  • The DXF files were imported into CAM software (MasterCAM) for toolpath planning.
  • Cutting parameters were carefully configured to ensure optimal machining performance:
    • Spindle direction: Clockwise.
    • Feed rate: 5000 mm/min.
    • Spindle speed: 15000 rpm.
    • Cutting speed: 500 mm/min.
    • FPT: 0.0833.
    • CS: 377.0028.
  • Path Planning:
    • 2D contour milling was selected for precision cutting.
    • Tool correction was applied to the right, with the calibration position set to the tool tip.
    • The maximum processing depth was adjusted to 0.05 mm for high accuracy.
  • An optimized G-code file was generated, incorporating a nesting algorithm to maximize material utilization.

1.3.2 Machine Operation​

  • The plywood sheet (18 mm thick) was securely fixed onto the CNC bed to prevent movement during cutting.
  • Tool length probing was performed to ensure precise depth control.
  • A dry test run was executed to verify the accuracy of the toolpath before initiating the actual cut.
  • The first-off production was closely monitored to ensure quality and consistency.

1.4 Assembly & Validation​

1.4.1 Component Integration​

  • All machined parts were dry-fitted to confirm proper alignment and tolerances.
  • Manual Chamfering: Some adjustments were necessary due to minor tolerance issues, requiring manual chamfering for smooth assembly.

1.4.2 Final Validation​

  • After a final inspection and validation, the bookshelf was assembled and ready for use.

1.5 Resource Management​