The use of hot melt adhesive film in mold heat transfer requires material preparation, mold and film processing, transfer operation, post-processing and inspection, and key details such as temperature control and pressure uniformity must be paid attention to. The following are specific operation procedures and precautions:
I. Operation process
1. Material preparation
Hot melt adhesive film selection:
Choose the type of adhesive film according to product requirements: select TPU glossy silicone hot melt adhesive film for high gloss and color saturation; select TPU matte silicone hot melt adhesive film for anti-reflective or low-key texture.
Confirm the specifications of the adhesive film: thickness (usually 0.05-0.2mm) and width must match the mold and substrate.
Substrate preparation:
Clean the surface of the substrate: use alcohol or special cleaning agent to remove oil and dust to ensure that there are no impurities.
Pretreatment (optional): Perform corona treatment or apply primer on difficult-to-stick materials (such as PP, PE) to improve adhesion.
Mold preparation:
Check the mold surface: ensure that there are no scratches or unevenness to avoid affecting the transfer effect.
Preheating mold (if necessary): Set the preheating temperature (usually 80-120℃) according to the type of film to improve the fluidity of the film.
2. Film and mold processing
Film cutting:
Cut the film according to the mold size, leaving a 3-5mm margin to prevent displacement during transfer.
Film positioning:
Attach the film flatly to the mold surface, use a roller or scraper to remove bubbles and ensure a tight fit.
Fix the film: Use high-temperature resistant tape or magnetic clamps to fix the edges to prevent falling off during transfer.
3. Transfer operation
Equipment preheating:
Set the temperature of the thermal transfer machine: adjust according to the melting point of the film (TPU film is usually 120-160℃).
Set pressure: adjust according to the thickness of the substrate (usually 0.2-0.5MPa) to ensure that the film fully penetrates the substrate.
Place the substrate: Align the cleaned substrate with the mold position and gently place it on the film to avoid movement and misalignment.
Hot press transfer:
Start the heat transfer machine and keep the pressure and time stable (usually 10-30 seconds, refer to the film manual for details).
Observe the state of the film: it is transparent after melting, indicating good adhesion.
4. Post-processing and inspection
Cooling and curing:
After the transfer is completed, move the product to the cooling table for natural cooling, or use cold air to accelerate curing (avoid deformation caused by rapid cooling).
Peeling the mold:
After the film is completely cured, slowly peel off the mold to prevent pulling and damaging the pattern.
Quality inspection:
Check the transfer effect: whether the pattern is complete, without bubbles, and without warping.
Test adhesion: After scratching with a hundred-grid knife, use tape to stick and tear it to observe whether it falls off (the standard must reach 4B or above).
II. Key points
1. Temperature control
Film melting point matching: Too low temperature will cause the film to not be completely melted and insufficient adhesion; too high temperature may cause the film to carbonize or the substrate to deform.
Segmented temperature control (if necessary): For complex molds or thick substrates, segmented heating can be used to ensure uniform heating.
2. Pressure uniformity
Avoid excessive local pressure: It may cause deformation of the substrate or overflow of the film, affecting the appearance.
Use flexible gaskets: Place silicone gaskets between the substrate and the mold to buffer the pressure and improve uniformity.
3. Time control
Short-term high efficiency: Too long transfer time may cause the film to age, and too short time may result in poor adhesion.
First trial production: It is recommended to conduct a small batch test first and adjust to the optimal time parameters.
4. Environmental requirements
Clean workshop: Dust may adhere to the surface of the film, resulting in particles after transfer.
Humidity control: High humidity environment may affect the viscosity of the film, and it is recommended that the humidity be ≤60%.
3. Common problems and solutions
Problem Possible causes Solutions
Pattern blurry Temperature is too high or pressure is too high Reduce temperature or pressure to shorten transfer time
Film falls off Temperature is insufficient or substrate is not clean Increase temperature, re-clean substrate and pre-treat
Bubble generation Air between film and substrate Use roller to remove bubbles before transfer
Substrate deformation Pressure is too high or cooling is too fast Reduce pressure and use natural cooling
4. Application cases
Electronic product housing:
Use TPU glossy silicone hot melt adhesive film to transfer LOGO, and achieve high gloss and wear-resistant logo effect through precise temperature control (150℃) and pressure (0.3MPa).
Automotive interior parts:
Use TPU matte silicone hot melt adhesive film to transfer wood grain pattern, and avoid deformation of interior panels through segmented heating (mold 120℃, substrate 140℃) and flexible gasket buffering.