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2025

Stanley Amaechi

Stanley Amaechi

I am a software engineer with over a decade experience in project cost management. I am passionate about AI and ioT and also a Fab Academy Student at Fab Lab Oulu.

This site is my personal portfolio developed during Fab Academy 2025.

© 2025 Stanley Amaechi | Template by Bootstrapious

Creative Commons License

This work is licensed under a Creative Commons Attribution-NonCommercial-ShareAlike 4.0 International License.

Week 7 - Computer-Controlled Machining

This week focused on computer-controlled machining, specifically designing and fabricating a large-scale object using a CNC machine. I designed a mobile workspace with integrated coffee holder and writing surface, exploring techniques for creating press-fit joinery and curved surfaces without using fasteners or glue.

CNC Machining Project

Tasks

  • Group Assignment:
    • Test runout, alignment, speeds, feeds, and toolpaths for the shopbot
    • Document our group's workflows and safety procedures
  • Individual Assignment:
    • Design and fabricate something big (~meter-scale)
    • Create a design that utilizes press-fit construction without fasteners or glue
    • Incorporate curved surfaces into the design

Process explanation

Group Assignment

For the group assignment, I collaborated with Lauri Hallman and Shahmeer Adnan Rana to explore CNC machining best practices, focusing on the Rensi e2-1325 CNC milling machine available in our lab.

Group Assignment Documentation

CNC Machine Testing Results

Parameter Test Method Results Implications
Runout Dial indicator measurement 0.02mm Excellent precision for smooth cuts
Alignment Test square cuts Within 0.1° of square Great for press-fit joinery
Speed & Feed - OSB Multiple test cuts Feed: 3000mm/min
Speed: 18000rpm		 Optimal for clean cuts in OSB
Tool Life - 6mm Flat End Mill Continuous cutting test ~4 hours in OSB Plan for tool changes on large projects
Key Finding: OSB proved to be an excellent material for large-scale fabrication, offering good structural integrity while being cost-effective. However, tool wear increases significantly when cutting through areas with dense resin pockets.

Individual Assignment

Design Process

Design Brief

I designed a mobile workspace that includes:

  • Writing surface with adjustable angle
  • Integrated coffee cup holder
  • Storage space for supplies
  • Wheels for mobility
  • Press-fit joinery with no fasteners or glue
Design Constraints
  • Material: 18mm OSB (Oriented Strand Board)
  • Machine bed size: 1300mm × 2500mm
  • Available tools: 6mm flat end mill, 6mm ball nose
  • Interlocking joints must be precise enough to hold without fasteners
  • Design must be sturdy enough for daily use
Initial Design Sketch
Fig 1 - Initial concept sketch of the mobile workspace
Design Evolution
Design Version 1
Version 1

Basic structure with simple joints

Design Version 2
Version 2

Added curved surfaces and cup holder

Design Version 3
Version 3 (Final)

Refined joints and optimized material usage

CAD Modeling with Fusion 360

I used Fusion 360 to create a parametric 3D model of my workspace. The parametric approach allowed me to easily adjust the joinery tolerance and overall dimensions.

Key Modeling Steps
Step 1: Base Structure

Created the base structure with parameters for material thickness and joint clearance.


// Parameter Examples
Material_Thickness = 18mm
Joint_Clearance = 0.2mm
Overall_Height = 850mm
Base Structure Model
Fig 2: Base structure model
Step 2: Joint Design

Designed press-fit joints with slight interference for stability. Used tabs and slots with rounded corners to avoid stress concentration.

Joint Detail
Fig 3: Press-fit joint detail
Step 3: Curved Surfaces

Created the curved writing surface using loft and sweep operations. The coffee holder was designed using a revolve operation.

Curved Surface Modeling
Fig 4: Creating curved surfaces
Step 4: Assembly Simulation

Simulated the assembly process to verify that all components fit together properly without fasteners.

Assembly Simulation
Fig 5: Assembly simulation view
Final 3D Model
Final 3D Model
Fig 6: Final 3D model with all components

CNC Preparation & Fabrication

Toolpath Generation

I exported my design as 2D drawings and prepared the toolpaths using NC Studio. For the curved surfaces, I used a ball nose end mill to achieve a smooth finish.

2D Toolpaths
2D Toolpaths
Fig 7: 2D cutting toolpaths for flat components
3D Toolpaths
3D Toolpaths
Fig 8: 3D toolpaths for curved surfaces
Optimized Material Layout

To minimize waste, I carefully arranged all parts on an 1200mm × 2400mm OSB sheet. The nesting optimization saved approximately 25% of material compared to my initial layout.

Material Layout
Fig 9: Optimized material layout
Fabrication Process
Step 1: Machine Setup
  • Secured OSB sheet to machine bed using T-track clamps
  • Set origin point at bottom left corner of material
  • Performed tool zero using touch-off plate
  • Verified emergency stop functionality
Machine Setup
Fig 10: CNC machine setup
Step 2: Cutting Process
  • Cut 2D profiles first with 6mm flat end mill
  • Changed to 6mm ball nose for 3D surface machining
  • Used tabs to keep parts secured during cutting
  • Total cutting time: approximately 3.5 hours
Cutting Process
Fig 11: Machine during cutting operation
Assembly Process

The press-fit design allowed for easy assembly without fasteners. Some joints required light tapping with a rubber mallet to ensure tight connections.

Video 1: Time-lapse of assembly process

Final Results

Final Result Front View
Fig 12: Front view of completed mobile workspace
Final Result Side View
Fig 13: Side view showing curved writing surface
Detail of Joints
Fig 14: Close-up of press-fit joints
Detail of Cup Holder
Fig 15: Detail of integrated coffee cup holder
Observations & Performance
  • Structure is remarkably sturdy despite using only press-fit joints
  • Curved writing surface provides ergonomic comfort during use
  • Coffee holder securely fits standard mug sizes
  • Mobile platform allows easy movement between workspaces
  • The overall assembly can be disassembled for transport or storage

Resources utilized

Reflection

Summary

This week's project allowed me to explore large-scale digital fabrication using CNC technology. Creating a functional piece of furniture pushed me to consider structural integrity, material properties, and precision joinery. The challenge of designing without fasteners or glue forced creative solutions for connections, while the requirement for curved surfaces expanded my CAD skills. The final mobile workspace successfully combines form and function while demonstrating the capabilities of computer-controlled machining for creating practical, large-scale objects.

Main Difficulties

  1. Press-Fit Tolerance:
    Finding the perfect tolerance for press-fit joints (0.2mm worked best) Material inconsistency affected joint tightness Had to adjust some joints after initial test cuts
  2. Tool Path Optimization:
    Balancing cutting time vs. quality for 3D surfaces Determining optimal step-over for smooth finish Managing tool changes efficiently
  3. OSB Material Properties:
    Dealing with rough edges requiring sanding Inconsistent density affecting cutting depth Managing chip extraction during deep cuts

Main Learnings

  1. Joint Design Principles:
    Mastering press-fit joint design for structural stability without fasteners
  2. Large-Scale Fabrication:
    Planning and executing a meter-scale project on CNC equipment
  3. 3D Toolpath Generation:
    Creating and optimizing 3D toolpaths for curved surfaces
  4. Material Optimization:
    Efficiently nesting parts to minimize material waste

Model Files