Inventor Modeling of Office Chairs

Modeling office chairs in Inventor requires a combination of ergonomic principles and functional design, achieved through step-by-step modeling and parameter adjustments.

I. Model Construction Basics

1. Virtual Human Modeling: Construct an ergonomic virtual human based on the Hanavan model, referencing Chinese adult body size standards (95th percentile for women aged 18-55) to determine dimensions for various body segments, such as height, sitting height, and hip width. Set human body density (approximately 1000 kg/m³) and equivalent elastic modulus (for subsequent mechanical simulations) to ensure the model aligns with real human proportions.
2. Office Chair Basic Framework: Design the overall chair outline based on virtual human dimensions, including components such as the seat, backrest, armrests, and five-star casters. The initial model can be simplified as a combination of geometric shapes (e.g., cuboids, cylinders), with subsequent refinement.

II. Functional Design and Modeling Key Points

1. Seat Adjustment Mechanism

   • Lever Mechanism Design: Draw straight lines and arcs through sketches to define the range of angle changes between the seat and the horizontal plane (e.g., 5° forward tilt for desk work, 10° backward tilt for deep rest). Use symmetric constraints and dimension annotations to ensure mechanism motion accuracy.
   • Surface Treatment: After stretching sketches to generate solids, trim the seat edges with new surfaces to eliminate sharp ends; perform similar operations on the sides to achieve smooth surface transitions. Spring components can be generated through helical line sweeps, with elastic parameters set to simulate cushioning effects.

2. Backrest Adjustment Mechanism

   • Hinge Four-Bar Mechanism: Design the connection between the backrest and seat as a four-bar structure, enabling angle adjustment through slots and spring rods. The angle between the backrest and seat ranges from 95° to 105° during rest and expands to 127° during deep rest.
   • Modeling Steps: Create a two-dimensional sketch to define bar lengths and connection points, then stretch to generate solids; use trimming tools to process contact surfaces between the backrest and seat, ensuring interference-free motion. Slot switches incorporate locking structures through Boolean operations.

III. Detail Optimization and Dimension Matching

1. Rounding and Hole Processing: Round sharp corners on the backrest and model edges (radius 2-5mm) to enhance comfort; create ventilation holes (diameter 10-20mm) on the seat through stretching and cutting.
2. Surface Thickening and Hiding: Convert thin-walled structures (e.g., backrest mesh) into solids using the 'Thicken' command; hide non-critical surfaces (e.g., lofted surfaces generated from auxiliary lines) to simplify the model.
3. Human Body Dimension Correction: Consult national standards for sitting human body dimensions, considering additional height for shoes (+10mm) and additional width for clothing (+10mm) to correct design dimensions. For example, the seat depth should exceed the 95th percentile of the distance from hip to knee, rounded to the nearest 5mm multiple.

IV. Verification and Adjustment

After completing the modeling, test the adjustment range of the seat and backrest using Inventor's 'Motion Simulation' module to check for mechanism jamming; use 'Stress Analysis' to verify the strength of key components (e.g., five-star casters), ensuring compliance with office scenario load requirements.