IML Printing Process & Quality Control Key Points_Technical Support

IML Printing Process & Quality Control Key Points

Author:SWITEK

Release Date:2026.08.26

What Are the Printing Processing Workflow and Quality Control Key Points of In-Mold Labels (IML)?

In-mold labels typically have a thickness between 60–100μm, with their shape determined by the container contour. Since they have no backing paper and must adapt to high-temperature heat melting, their printing processing—from tension control, corona treatment, and printing to die cutting and static elimination—follows strict technical standards.

I. Key Control of IML Printing & Prepress

01. Tension Control & Large Core 152mm Core

Using a 152mm large-diameter core tube ensures minimal material deformation near the core;配合 the printing press automatic tension control system guarantees high-precision registration.

02. Dyne Value & Corona Treatment Anti-Static Accumulation

When surface tension is below 40 dynes, corona treatment is required to improve ink adhesion. However, random corona frequency should be controlled as much as possible to avoid excessive static electricity causing label separation difficulties.

03. Multi-Method Printing Selection Offset/Flexo/Gravure/Screen

Offset printing suits multi-variety, small-batch jobs; letterpress/flexo UV suits medium to large batches with vivid colors; gravure printing has a thick, scratch-resistant ink layer, ideal for ultra-large batch, long-run jobs.

04. Static Elimination & Workshop Temperature/Humidity Constant Temp & Humidity

All stations—printing, die cutting, sheet cutting, etc.—must be equipped with static eliminators. Ideal environmental control is temperature 21°C±2°C and relative humidity around 50%, preventing stacking adhesion.

05. Precise Control of Ink & Fountain Solution Prevent False Drying & Emulsification

Offset fountain solution dosage is reduced by 10%–15% compared to conventional, with pH controlled at 6–6.5; use quick-drying or UV ink, and the label placement arrangement direction must be parallel to the machine stretching direction.

II. Post-Processing, Packaging & Automated Labeling Molding

01. Hot Stamping & Professional Varnishing Anti-Deformation Over-Varnish

Supports anodized aluminum foil stamping; after printing, scratch-resistant, non-shrinking dedicated infrared/UV varnish must be used to protect the ink, ensuring labels are flat and not curled, with no adhesion when stacked.

02. Linerless Dedicated Die Cutting Hardened Steel Cutting Tools

In-mold labels are linerless, requiring dedicated steel cutting tools经过 quenching and hardening treatment. Supports inline rotary die cutting, or sheet cutting then die cutting using a wine label die cutting machine.

03. Splint Protective Packaging Hard Box Shrink Film

Due to uneven surface ink layer thickness, finished products must be packaged in rigid paper boxes, or have splints placed at both ends, strapped and sealed with shrink film, to prevent warping and edge bump damage.

04. Robot High-Precision Label Placement IML Robot

After packaged sheet labels are sorted by the label separation device, a robot equipped with special fixtures picks them up with millisecond-level precision and precisely places them into injection/blow mold cavities.

05. High-Temperature Fusion Integrated Molding Seamless Fusion

After the mold closes, the molten plastic and label solid adhesive backing rapidly互溶 and bond under high temperature and pressure. Upon demolding, the result is a high-quality integrated product with seamless appearance and non-peelable properties.

III. Summary & Exchange

In-mold labeling (IML) printing and molding is a systematic engineering spanning printing, materials science, and high-precision automation. Only by controlling tension, static elimination, die cutting, and the mold insertion precision of automated robots can the perfect quality of every finished product be guaranteed.

SWITEK focuses on high-speed in-mold labeling robots and automation system integration, committed to helping you bridge the "last mile" of IML production. If you have any needs, please feel free to contact us!

SWITEK Contact Information

WhatsApp/WeChat/Phone: +86 18665171961

Website: www.switek.com.cn

Address: No. 5, Tangbian Nanwei Industrial Park, Chashan Town, Dongguan City, Guangdong Province

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