ISO 5623:2022

Overview

ISO 5623:2022 specifies quality levels for imperfections in joints of thermoplastic moulded components that arise from the joining process. It covers production-quality acceptance criteria for a wide range of thermal joining processes (ultrasonic, infrared, vibration, laser, hot plate, spin, hot gas convection, heat staking, etc.). The standard defines three graded quality levels - B (stringent), C (intermediate) and D (moderate) - and provides dimensional limits for common imperfection types. ISO 5623 is intended as a reference for application specifications and production inspection; it addresses imperfections caused by joining, not defects from prior poor fit-up or in-service damage.

Key topics and requirements

• Three quality levels (B, C, D) mapped to DFMEA severity classes (B: 9–10; C: 6–8; D: 0–5). These levels are selected before production (preferably at enquiry/order stage).
• Process coverage: ultrasonic welding, ultrasonic spot welding, infrared welding, hot gas convection welding, vibration welding, spin welding, laser welding, hot plate welding and heat staking (hot air, electrical, infrared, ultrasonic).
• Imperfection types are listed and defined (examples include cracks, gas cavities, degraded polymer inclusions, lack of fusion, cold fusion, misalignment, excess weld material, thermal damage and tool marks).
• Dimensional limits: imperfections are quantified (e.g., gas-cavity sum diameters and misalignment tolerances are specified as percentages of component wall thickness - commonly B ≤ 5%, C ≤ 10%, D ≤ 15% for cavities; misalignment limits similarly scale with quality level).
• Inspection guidance: primarily aimed at visual testing; measurement can follow EN 12814‑5, EN 13100‑1/2/3 or other methods (computed tomography, active thermography, terahertz, laser scanning). Non‑destructive methods may require supplementary inspection criteria.
• Use in quality systems: intended for drafting application specifications; allows different quality levels for different joints within the same component when required.

Practical applications

• Use ISO 5623 when defining acceptance criteria for welded or joined thermoplastic parts in production.
• Apply it in supplier contracts, incoming inspection plans, and production control to ensure consistent, documented criteria for joint imperfections.
• Helpful for process engineers, quality engineers, designers and contract manufacturers to balance design requirements, service conditions and inspection costs.

Related standards

• ISO 23512 - Thermal joining process specification (TJPS) and preparation before joining
• EN 14728 - Designations of thermal joining imperfections (basis for table numbering)
• IEC 60812 - Failure modes and effects analysis (FMEA/FMECA)
• EN 12814‑5, EN 13100‑1/2/3 - Measurement and inspection references
• ISO/TC 138 - Standards for joining plastic pipes and fittings

Keywords: ISO 5623, thermoplastic joining, quality levels, weld imperfections, ultrasonic welding, laser welding, hot plate welding, thermal joining, TJPS, production quality.