Specializing in the production of screen printing machine, pad printing machine and its printing auxiliary equipment
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Specializing in the production of screen printing machine, pad printing machine and its printing auxiliary equipment
How to pad printing on bottle cap?
一、Pad printing process:
Pad printing on bottle caps involves a detailed process to ensure precise and durable results. Here's a structured approach:
1. Design Preparation: Prepare a steel plate with a pattern/logo
2. Material Considerations
Cap Material: Determine if caps are plastic (e.g., PP, PE) or metal. This affects ink selection (e.g., solvent-based for plastics, UV-curable for fast curing).
Surface Pre-Treatment: Clean caps with isopropyl alcohol to remove contaminants. For plastics, use corona treatment to enhance ink adhesion.
3. Machine Setup
1) Install pad printing machine: Set up pad printing head (silicone head) and fixture.
2) Selection of silicone pad : Choose a silicone head with moderate hardness according to the curvature of the bottle cap (commonly used hardness is Shore A 15-25 °).
3) Fixture design: Customize a fixed device that matches the bottle cap to ensure stability and no displacement of the cap during printing.
4) Adjust parameters:
Scraper pressure: evenly scrape off excess ink on the rubber plate.
Pressure and time of the transfer head: affects the ink transfer amount (usually pressure is 0.2-0.5MPa, contact time is 0.5-2 seconds).
4. Printing operation
Automatic/semi-automatic printing:
Pad Transfer: The silicone pad presses onto the plate, picks up ink, and stamps onto the cap. Adjust pressure to ensure full contact without smudging.
Multi-Color Printing: Use registration systems for alignment. Each color layer requires a separate plate and pad.
5. Drying or Curing
Drying Method: UV-curable inks require UV lamps; solvent-based inks may need air drying or ovens. Ensure proper curing time to prevent smearing.
6. Quality Control
Inspection: Check for clarity, color alignment, and defects. Use tape tests for adhesion.
Post-Processing: Handle cured caps carefully during packaging to avoid scratches.
二、Key points for attention
1) Bottle cap pretreatment
Clean surface oil stains and release agents (can be treated with alcohol or plasma).
For non-polar materials such as PP/PE, corona treatment or flame treatment is required to improve ink adhesion.
2) Printing head matching
Curved bottle caps require curved silicone heads to avoid pattern distortion during printing.
The silicone head needs to be cleaned regularly to prevent ink residue from affecting accuracy.
3) Color register
When printing with multiple colors, the positioning system needs to be calibrated, and the fixture needs to ensure that the bottle cap is placed at the same angle every time.
4) Environmental control
Control the temperature and humidity in the workshop (recommended temperature of 20-25 ℃, humidity of 50-70%) to prevent ink from drying too quickly or sticking.
三、Common Problems and Solutions
1) Ink peeling: Check if the material pre-treatment is sufficient, or replace with ink with stronger adhesion.
2) Pattern blurring: Adjust the pressure of the transfer head, reduce ink viscosity, or shorten transfer time.
3) Color difference issue: Regularly clean the adhesive plate to ensure even ink mixing.
四、Production Scaling
Manual VS Automated: Use manual machines for small batches; automate with conveyors and robotic arms for high volume.
