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Project for MIT 2.72 Elements of Mechanical Design · Spring 2025
As a five-student team, we designed, fabricated, and verified performance of a benchtop CNC lathe, meeting uncompromising performance requirements in precision, robustness, and budget. With little time for iteration, this 12-week challenge cemented my ability to synthesize analytical skills and practical knowledge to rigorously design, build, and test a customer-ready product.
SPECS
Cuts mild steel and strengthened aluminum
30 micron repeatability
20 micron CNC resolution
40mm swing radius
100 mm maximum part
330 W maximum power draw
41 lbs total weight
350 x 350 x 500 mm envelope
Withstands 1-m drop test
Withstands tool post crash the spindle
MODELING
Formulated quantitative subsystem requirements to meet overall performance goals
Estimated cutting forces and power using first principles and empirical data
Resolved design trades using sensitivity analysis
Selected spindle bearing layout using free-body and shear-moment diagrams
Wrote excel sheet calculators to size and validate X-axis and Z-axis lead screw assemblies (stress, stiffness, thermal error, backlash, etc.)
Specced and selected off-the-shelf components (motors, lead screws, fasteners)
TESTING
Used Coordinate Measuring Machine (CMM) and dial indicators to tune perpendicularity of X+Z axes, assess spindle runout, and stiffness of individual subsystems within the structural loop
Turned and parted steel and aluminum rods to assess maximum material removal rate
TAKEAWAYS
Theoretical and practical understanding of structural loops, compliance, error stack-up, and machine elements (bearings, bolts, flexures, lead screws, belts, gears, etc.)
Formal process of decomposing complex systems into subsystems
Experience writing quantitative functional requirements to ensure overall performance
Development of process plans to ensure design for manufacturing and assembly and streamline fabrication
The power of adjustability, tuning, and metrology to achieve both precision and accuracy
Key skills: Precision machine design · Excel · SolidWorks · CNC machining · Metrology (CMM, dial indicators, etc)
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