1. Fabric & Component Preparation
A. Material Selection
- Main Fabric: 95% Cotton + 5% Spandex interlock knit (180-220g/㎡)
Why? Balanced breathability (ISO 11092: 0.08 m²·K/W) and 30% crosswise stretch (ASTM D2594). - Critical Components:
- 1.5cm wide polyester-covered elastic (Tensile strength ≥25N/cm, ISO 13934-1)
- Antibacterial gusset fabric (Silver-ion coated, ISO 20743 compliant)
B. Precision Cutting
- Cutting Table Setup:
- 10 fabric plies stacked on GERBERcutter XLs7000
- Laser-guided alignment (Tolerance: ≤0.5mm)
- Key Panels:
- Front panel ×1 (with fly opening notch)
- Back panel ×1
- U-shaped gusset ×1
- Waistband casing ×1
- Edge Treatment: Silicone oil spray to prevent fraying during sewing.
2. Core Sewing Sequence (5-Stage Protocol)
Stage 1: Front Panel Assembly
- Operation: Layer front panel + double gusset lining
- Machine: 3-thread overlock (JUKI MO-6714S)
- Parameters:
- Stitch length: 2.8mm
- Seam allowance: 8mm
- Pre-tension fabric 3% to prevent curling
Stage 2: Gusset Reinforcement
- Operation: Join U-gusset to front/back panels
- Machine: 4-needle 6-thread flatlock (PEGASUS 747-34)
- Critical Settings:
- Needle type: NTX70 (ballpoint)
- Thread tension: 25cN ±2
- Form chain-stitch ventilation holes
Stage 3: Side Seam Construction
- Operation: Align and stitch front/back panels
- Machine: 3-thread overlock (JUKI MO-3616)
- Quality Control:
- Stretch seams to 150% → No thread breakage (ISO 13935-2)
- Seam slippage ≤3mm under 80N load (ASTM D434)
Stage 4: Waistband Engineering
- Step A – Elastic Pre-treatment:
Heat-set at 50°C for 3min (eliminate retraction stress) - Step B – Casing Application:
- Fold waistband casing over elastic
- Stitch with twin-needle coverstitch (JUKI MF-7900)
- Stitch density: 12 stitches/3cm
- Reinforcement: Bar tack at side seams (Tensile ≥80N)
Stage 5: Leg Opening Finishing
- Process:
- Turn hem inward 5mm
- Apply formaldehyde-free hot melt adhesive (GB 18401-2010 certified)
- Topstitch with 1/8″ (3.2mm) narrow overlock
- Result: Invisible edge with 200+ wash cycles durability
3. Post-Production & Quality Assurance
| Process | Equipment/Standard | Key Metrics |
|---|---|---|
| Steam Molding | 3D mannequin press | 110°C/8sec @ 0.3MPa |
| Antimicrobial Treatment | Electrostatic spray booth | ≥99% coverage (AATCC 100) |
| Final Inspection | Tension tester + Metal detector | Seam strength ≥45N, Ø≤0.8mm metal |
4. Production Pitfall Solutions
- Fabric Shrinkage: Pre-shrink at 40°C (20m/min conveyor speed)
- Twisted Elastic: Laser-guided alignment jig (Error rate <0.1%)
- Bacterial Contamination: UV-C sterilization tunnel (254nm/30sec)
Coming Next: The Seamless Advantage – Why Elite Sportswear Demands Invisible Construction
Beyond stitches: How 3D knitting redefines athletic performance. In our next technical deep dive, explore:
- Biomechanical Liberation:
24-gauge circular knitting enables 12-directional stretch zones (lab-tested per ISO 13934-1) – eliminating restrictive seams at hip rotation points. - Sweat Management Breakthrough:
Monolithic construction reduces moisture retention by 47% vs. stitched counterparts (AATCC 195 vertical wicking tests). - Proven Endurance Edge:
87% of marathon runners in blind trials reported zero chafing with seamless designs (Nike ACG athlete survey).
Email me at carter@xiyigarments.com to see the assembly line video!
