To achieve the effect of thick plate of silk screen printing silicone (label thickness ≥ 0.3mm with clear edges and smooth surface), it is necessary to systematically optimize materials, equipment and process parameters. The following is the technical core and operation guide:
I. Material selection and pretreatment
1. Silicone type and ratio
Basic silicone: Use high viscosity, slow-drying silicone (such as Shin-Etsu KE-1310T or Dow Corning 3140), and the viscosity must be ≥50,000 cps to support thick plate printing.
Curing agent ratio: Strictly follow the ratio of 10:1 (silicone: curing agent), with an error of ≤±1%. Too much curing agent is prone to brittle cracking, and too little curing is incomplete.
Additive regulation:
Thickener: Add 2%-3% fumed silica (such as Cabot M-5) to improve the stiffness of silicone and reduce printing collapse.
Leveling agent: Add 0.5%-1% of silicone leveling agent (such as BYK-333) to improve the surface flatness of silicone.
2. Silicone pretreatment
Vacuum degassing: After the silicone is mixed, it needs to be degassed in a vacuum environment of -0.095MPa for 10 minutes to avoid bubbles causing surface unevenness during printing.
Adjusting the glue in batches: The amount of glue adjusted in a single batch is ≤500g to prevent the silicone from settling or viscosity changes due to its own gravity.
II. Equipment and screen configuration
1. Screen parameters
Screen selection: Use 305 mesh polyester screen, screen tension ≥22N/cm to ensure that the screen does not deform during printing.
Emulsion thickness: After applying the photosensitive glue, the screen emulsion thickness is controlled at 15-20μm. Too thick will easily cause silicone residue, and too thin will result in insufficient printing thickness.
Edge treatment: The edge of the screen is chamfered with 0.1mm to reduce silicone accumulation during printing.
2. Scraper and ink return knife
Scraper hardness: Use a polyurethane scraper with 70-75 Shore A. Too low hardness will easily cause silicone leakage, and too high hardness will result in uneven printing pressure.
Scraper angle: The printing angle is controlled at 65°-75°, and the ink return knife angle is 45° to ensure that the silicone fills the mesh evenly.
3. Printing platform
Vacuum adsorption: Use a vacuum adsorption platform with an adsorption force of ≥0.05MPa to prevent the substrate from shifting during printing.
Platform flatness: The surface flatness of the platform is ≤0.02mm to avoid uneven printing thickness.
III. Process parameters and operation procedures
1. Layered printing and curing
Multi-layer thin printing: The silicone with a total thickness of 0.5mm is divided into 3-4 times of printing, and the thickness of each printing is 0.12-0.15mm.
Curing parameters:
Infrared leveling: After each layer is printed, bake it in an 80℃ infrared leveling machine for 3-5 minutes to ensure that the silicone surface is flat.
Final curing: After all layers are printed, cure them in a 150℃ oven for 30 minutes to ensure that the silicone is completely cross-linked.
2. Printing pressure and speed
Pressure control: The printing pressure is set to 0.2-0.25MPa. Too high pressure may cause silicone leakage, while too low pressure may cause insufficient printing thickness.
Speed optimization: The printing speed is controlled at 15-20cm/s. Too fast speed may cause insufficient silicone filling, while too slow speed may increase the production cycle.
3. Off-grid height and angle
Off-grid height: The distance between the screen and the substrate is kept at 0.5-1.0mm. Too small a distance may cause silicone residue, while too large a distance may cause flying glue.
Off-grid angle: Use an oblique off-grid method of 15°-20° to reduce the adhesion of silicone and the screen and reduce the risk of edge blur.
IV. Quality inspection and common problem solving
1. Quality inspection standards
Thickness inspection: Use a laser thickness gauge to take 5 points at the four corners and center of the label, and the thickness deviation is ≤±0.05mm.
Edge sharpness: Observe under a 40x microscope, and the edge serration is ≤0.1mm.
Adhesion test: According to ASTM D3359 standard, a hundred-grid knife test is used, the scratch spacing is 1mm, and the residual area after the tape is peeled off is ≥95%.
2. Common problems and solutions
Problem phenomenon Possible cause Solution
The surface is uneven. The bubbles in the silicone are not completely removed. Extend the vacuum degassing time to 15 minutes and check the sealing of the vacuum pump
The edge is blurred. The scraper pressure is uneven or the off-grid angle is too large. Adjust the scraper pressure to 0.22MPa and optimize the off-grid angle to 18°
Insufficient printing thickness. The viscosity of the silicone is too high or the printing speed is too fast. Add a leveling agent to reduce the viscosity and reduce the printing speed to 18cm/s
V. Technical cases and data comparison
1. Case comparison
Traditional process: single printing thickness 0.2mm, edge blur 0.3mm, production efficiency 500 pieces/hour.
Optimized process: layered printing (0.15mm×3 layers), edge blur 0.08mm, production efficiency 300 pieces/hour (due to increased curing time).
2. Cost and efficiency
Material cost: After optimizing the process, the amount of silicone increased by 15%, but the overall cost decreased by 5% due to the reduction in scrap rate (from 8% to 2%).
Equipment investment: It is necessary to add vacuum degassing machines and infrared leveling machines. The initial investment increased by about 20%, but the long-term production efficiency increased by 30%.
Sixth, summary
The key to achieving the effect of silk-screen silicone thick plate lies in layered printing, precise parameter control and strict quality inspection. The following steps can systematically improve the quality:
Material pretreatment: vacuum degassing, batch glue adjustment.
Equipment optimization: high tension screen, oblique off-grid.
Process improvement: multi-layer thin printing, infrared leveling.
Quality inspection guarantee: laser thickness measurement, microscope edge detection.
In actual production, it is necessary to flexibly adjust parameters in combination with equipment accuracy, silicone model and label design, and verify the process stability through small batch trial production.