If you’re optimizing injection molding for thin-walled parts or PET preforms, external cooling for preforms is a proven strategy to shorten cycle time without sacrificing quality. This guide explains what external cooling is, why it matters, and how a combined air-and-water method—pioneered by IVIROBOT—improves productivity, consistency, and energy efficiency.
What is external cooling for preforms?
External cooling for preforms refers to cooling processes applied after the part leaves the mold. Instead of relying entirely on in-mold cooling, a portion of the heat removal is completed outside the mold using controlled air and/or water cooling. This approach is especially effective for thin-walled components and high-throughput production lines where every second of cycle time matters.
Why not cool 100% inside the mold?
In-mold cooling typically accounts for 60–80% of the total molding cycle.
Extending in-mold cooling to 100% significantly increases total cycle time, reduces line throughput, and raises unit costs.
Moving 20–30% of cooling outside the mold balances the trade-off between adequate part cooling and overall production efficiency.
Key benefits of external cooling for preforms
Shorter cycle times: Offloading part of the cooling stage from the mold reduces clamp time and increases shots per hour.
Higher throughput with stable quality: Properly designed external cooling prevents warpage, sink, and internal stress while maintaining dimensional stability.
Uniform temperature drop: Combined air and water cooling accelerates and equalizes surface temperature reduction, minimizing hot spots and overcooling.
Better energy efficiency: Optimized cooling reduces unnecessary mold chill time, lowering energy consumption per part.
Higher automation levels: Inline external cooling supports continuous, automated handling of preforms and thin-walled parts.
Traditional vs. advanced external cooling
Traditional method: Air cooling only (blowing air on parts after ejection). This is simple but can be slow and uneven for demanding geometries.
Advanced method (IVIROBOT): Hybrid water + air cooling. This flexible system provides precise thermal control, enabling faster, more uniform cooling and improved repeatability.
How IVIROBOT’s external cooling for preforms works
Hybrid cooling architecture: Integrates water cooling and air cooling in a coordinated sequence or simultaneous application.
Precision temperature control: Tailors cooling intensity to part geometry and material behavior to avoid localized overcooling or overheating.
Flexible implementation: Adaptable to different preform sizes, wall thicknesses, and line speeds without sacrificing stability.
Designed for continuous production: Ideal for high-spec thin-walled products requiring consistent quality at scale.
Applications
PET preforms and beverage packaging components
Thin-walled technical parts
High-cavitation, high-speed injection molding lines
Facilities focused on reducing cycle time and energy per part
Measurable outcomes
20–30% of total cooling shifted outside the mold
Reduced overall cycle time and improved OEE (Overall Equipment Effectiveness)
Lower internal stress and deformation rates
Higher line automation and reduced manual intervention
Best practices for implementing external cooling
Analyze heat load: Map thermal profiles across the preform to identify areas prone to hot spots or uneven cooling.
Match cooling media to needs: Use water cooling for rapid heat extraction and air cooling for fine-tuning and drying.
Control dwell and flow: Optimize air velocity, water flow rate, and exposure time to prevent surface defects.
Synchronize with handling: Integrate with robots, conveyors, and part grippers to maintain takt time and part stability.
Monitor and adjust: Use temperature sensors or IR cameras to maintain consistent, repeatable cooling performance.
Why choose external cooling for preforms now
Manufacturers facing competitive cycle-time targets, energy reduction goals, and strict dimensional tolerances can gain immediate benefits from external cooling. IVIROBOT’s hybrid solution delivers faster, uniform cooling that shortens cycles and stabilizes quality—ideal for modern, automated molding environments.
FAQ
What percentage of cooling should occur outside the mold?
Typically 20–30%, with 60–80% handled by in-mold cooling, depending on part design and performance targets.
Is water cooling safe for preforms?
Yes. When controlled, water cooling rapidly removes heat without inducing stress; air cooling complements it for uniformity and drying.
Will external cooling affect part quality?
Properly implemented, it reduces internal stress, warpage, and deformation while improving consistency and dimensional stability.
Can I retrofit external cooling to existing lines?
In many cases, yes. Systems can be integrated with existing robots, conveyors, and QC checkpoints with minimal disruption.
Interested in implementing external cooling for preforms? Contact IVIROBOT to evaluate your line, quantify cycle-time savings, and design a hybrid cooling solution tailored to your parts and production targets.
