In screen printing, tension control is a key link to ensure printing quality. Insufficient tension can cause screen deformation and blurred graphics, while excessive tension may cause screen breakage or abnormal printing pressure. The following is a comprehensive analysis and optimization suggestions on tension control:
1. Core elements of tension control
Initial tension setting
Standard range: usually 25-35 N/cm² (specific adjustment needs to be made according to the screen material, mesh count, and substrate).
Material differences:
Polyester screen: The tension can be slightly higher (30-35 N/cm²) because of its high tensile strength.
Nylon screen: The tension needs to be slightly lower (25-30 N/cm²) to avoid excessive loss of elasticity.
Mesh count effect: High mesh screens (such as 300 mesh or above) require higher tension to maintain flatness, but it is necessary to avoid exceeding the material limit.
Tension uniformity
Screen frame selection:
Aluminum screen frame: High rigidity, suitable for high tension printing.
Wooden screen frame: Easily deformed by humidity, only suitable for low tension or temporary printing.
Mesh stretching process:
Mechanical mesh stretching: Uniform stretching through pneumatic or electric equipment, the error can be controlled within ±2 N/cm².
Manual mesh stretching: requires experienced operators, large errors, only suitable for low-precision requirements.
2. Tension monitoring and adjustment method
Tool selection
Tension meter:
Digital tension meter: high accuracy (±0.5 N/cm²), suitable for mass production.
Pointer tension meter: portable but low accuracy, suitable for rapid on-site detection.
Measuring position:
Measure every 10cm from the edge to the center of the mesh frame to ensure uniformity.
Environmental impact and compensation
Humidity control:
For every 10% increase in humidity, the mesh tension may decrease by 5-10%. It is recommended that the workshop humidity be maintained at 40-60% RH.
Temperature compensation:
For every 10℃ increase in temperature, the tension may increase by 3-5%. The initial tension needs to be appropriately reduced in high temperature environments.
Real-time monitoring:
Use intelligent mesh stretching equipment with sensors to automatically record tension changes and compensate.
3. Common problems and solutions for abnormal tension
Problem manifestation Possible cause Solution
Rapid decrease in tension Screen aging, screen frame deformation Replace screen or reinforce screen frame
Uneven local tension Uneven force during screen stretching Re-stretch the screen and use mechanical screen stretching equipment
Tension fluctuations during printing Excessive scraper pressure, screen fatigue Adjust scraper angle (70-80°) and pressure to shorten printing time
Blurred edges of graphics Insufficient tension causes delayed screen rebound Increase initial tension to the upper limit of the standard
4. Optimization suggestions for tension control
Stage-by-stage screen stretching
Coarse stretching: Quickly stretch to 70% of the target tension to eliminate screen relaxation.
Fine stretching: Slowly increase to the target value, keep stable for 10-15 minutes and then fix.
Regular maintenance
Screen life: Polyester screen can be reused 50-100 times, nylon screen 30-50 times, and needs to be replaced after exceeding the life.
Screen frame inspection: Check the flatness of the screen frame every month, and calibrate or replace it if the error exceeds 0.5mm.
Process adaptation
Curved surface printing: reduce tension to 20-25 N/cm² to enhance screen elasticity.
Thick ink layer printing: appropriately increase tension to 30-35 N/cm² to avoid ink accumulation.
5. Case analysis
Case 1: High-precision circuit board printing
Problem: Graphic offset and line breakage.
Cause: Insufficient tension (18 N/cm²) causes delayed screen rebound.
Solution: Replace high-mesh (350 mesh) polyester screen, increase tension to 32 N/cm², and the problem is solved.
Case 2: Glass bottle curved surface printing
Problem: Uneven ink and blurred edges.
Cause: Excessive tension (38 N/cm²) causes screen elasticity loss.
Solution: Use nylon screen instead, reduce tension to 22 N/cm², and the printing effect is significantly improved.
Summary
Tension control needs to be adjusted in combination with screen material, mesh, substrate and environmental factors. Through standardized screen stretching process, real-time monitoring and dynamic compensation, printing accuracy and stability can be significantly improved. It is recommended to establish a tension management file to record the parameters and printing effects of each stretching, so as to provide data support for subsequent optimization.