Seamless vs. Sewn: The Core Truths for Underwear & Loungewear

1. Seamless (无痕) – The Invisible Bond

• Definition:
  Garments knitted in one piece using 3D circular machines (18-24 gauge), then shaped by steam heat-pressing (120-150°C) to fuse layers without stitches.
• Suitable Fabrics:
  Elastic synthetics (Nylon/Spandex blends ≥85%), MicroModal, Bamboo viscose.
• Key Traits:
  • Zero seams → Eliminates chafing (ideal for sensitive skin)
  • 360° stretch → Unrestricted movement for sports
  • Lightweight (0.2-0.5mm thickness)
• Production Flow:
  Yarn → 3D knitting → Steam molding → Laser cutting → Quality control

2. Sewn (车缝) – The Strategic Stitch

• Definition:
  Cut fabric panels joined by industrial sewing machines using lockstitch (ISO 4915 Type 301) or overlock (Type 504) techniques.
• Suitable Fabrics:
  Woven cotton, Linen, Heavy knits (>250gsm), Quilted insulation.
• Key Traits:
  • Reinforced seams → Handles tension at stress points (waistbands/gussets)
  • Structured silhouette → Holds shape for tailored loungewear
  • Repairable → Damaged seams can be re-stitched
• Production Flow:
  Fabric → Cutting → Stitching (flatlock/overlock) → Trimming → Inspection

When to Choose Which

Coming Next: Anatomy of a Classic Men’s Brief – Sewn Process Exposed

Ever wonder how 12 fabric panels become 1 indestructible brief? Our next Factory Floor Diaryreveals:

• Step-by-Step Journey:
  1. Precision cutting of cotton interlock panels (back/front/gusset)
  2. 4-thread overlock stitching (ISO 4915 Type 504) at crotch seam
  3. Waistband application with dual-needle topstitching
  4. Elastic bonding via ultrasonic welding (no threads)
  5. Final inspection under tension simulators
• Critical Machines:
  • Juki DDL-9000 lockstitch for flat seams
  • Pegasus overlock for stretch zones
  • Ultrasonic bonder for tagless finish

Email me at carter@xiyigarments.com to see the assembly line video!

Want a specific detail? Email me at carter@xiyigarments.com like: “How is gusset reinforcement tested?”