Capama Events

2026-07-05 | CAPAMA Machinery Technical Team | Reading time: approx. 8 min

Foreword

With 20 years in automatic screen printing, CAPAMA Machinery's technical team has served over 500 customers across electronic labels, nameplates, appliance control panels, 3C electronics, garment and footwear heat transfer, and automotive printed materials. Today we share the most practical techniques from daily production across 6 topics, to help every operator get the most out of their roll-to-roll automatic screen printing machine.

1. Squeegee Angle and Pressure — The First Gate to Print Quality

The print quality of an automatic screen printing machine depends largely on squeegee system adjustment. This is the most experience-intensive area and the most commonly overlooked by beginners.

1.1 Choosing the Right Squeegee Angle

The squeegee angle (the angle between the squeegee blade and the screen) directly affects ink transfer volume and print clarity:

• • 65-75° (Steeper): Best for fine lines and dot printing. A steeper angle concentrates pressure through the mesh openings for sharper edges, but produces a thinner ink layer.
  Recommended for: Fine circuit printing on electronics, high-precision barcodes.
• • 45-55° (Flatter): Best for large solid areas and thick ink deposits. A shallower angle allows more ink through for thicker, more opaque coverage.
  Recommended for: White ink underlay, color printing on dark substrates.
• • 55-65° (General purpose): Suitable for 90% of daily orders, balancing clarity and ink thickness.

1.2 Squeegee Pressure Guidelines

Squeegee pressure follows a "lighter is better" principle:

• Excessive pressure causes sawtooth edges (ink bleeding from mesh edges), premature screen wear
• Insufficient pressure results in incomplete ink transfer, producing white spots or faint prints

As a rule of thumb: set the pressure just enough to completely push ink through the mesh, then add a small margin. Each machine has its optimal value. We recommend a "pressure gradient test" during the break-in period — print at increasing pressures on the same screen to find the sweet spot between clarity and screen life.

Practical tip: Use a protractor gauge when setting the squeegee holder angle. CAPAMA machines feature a pivoting squeegee angle adjustment mechanism for precise setting, with independently adjustable squeegee and flood bar pressure.

2. Proper Flood Bar Setup — Key to Production Efficiency

The flood bar pushes ink back across the screen surface after the squeegee stroke, preparing for the next print. The coordination between flood bar and squeegee directly affects print consistency across the entire batch.

Tip: CAPAMA's fully servo-driven print head allows operators to set flood and squeegee speeds independently via the touchscreen — useful for high-precision jobs.

3. Unwind/Rewind Tension Control — The Hidden Challenge of Web Printing

In roll-to-roll screen printing, tension control is one of the most critical yet most underestimated factors affecting register accuracy and product quality. Tension fluctuations during printing directly cause misregistration and material deformation.

3.1 Basic Tension Settings

• Low tension for thin materials: PET film, BOPP (0.02-0.1mm) — keep tension low to avoid stretching and accumulated registration errors.
• Higher tension for thick materials: PVC sheet, synthetic paper (0.2-15mm) — increase tension for smooth web feeding.
• Special care for composite materials: Pressure-sensitive label stock, heat transfer film and other multi-layer materials require precise tension balance to avoid curl caused by differential elongation between layers.

3.2 Matching Unwind and Rewind Tension

On a roll-to-roll screen printer, tension is primarily controlled at the unwind and rewind stations. Unwind tension governs how material enters the print section; rewind tension determines roll tightness. Getting them right is critical:

• Excessive unwind tension stretches the material before it reaches the print head, causing misregistration
• Excessive rewind tension can crush freshly printed patterns or cause edge curl
• Insufficient rewind tension produces loose rolls that are hard to process downstream

After changing material batches, run a short test to find the optimal unwind/rewind tension balance before starting full production.

CAPAMA roll-to-roll automatic screen printers come standard with a feeding tension system (continuous unwind), paired with Yaskawa servo drives for precise tension control throughout production.

4. Ink Layer Uniformity Control

Screen printing produces ink layers 3-5 times thicker than letterpress — an advantage and a challenge. Uneven ink layers cause color variation, insufficient opacity, and inconsistent curing.

4 key factors affecting ink layer uniformity:

1. Screen tension: Insufficient or uneven screen tension directly causes ink layer thickness variation. Check regularly with a screen tensiometer.
2. Ink viscosity: Viscosity can vary 30-50% between summer and winter. Add thinners in winter; prevent excessive evaporation in summer.
3. Print speed consistency: Ink thickness changes during acceleration and deceleration. CAPAMA's fully servo-driven print head maintains constant speed throughout the stroke — one of its key advantages.
4. Snap-off distance: The gap between screen and substrate (typically 3-6mm). Too small or too large leads to poor ink shear and mottled appearance.

5. Transparent Material Printing — Material Selection to Parameter Tuning

Printing on transparent materials (PET, clear BOPP) is one of the more challenging tasks on an automatic screen printer. The difficulties lie in reduced sensor detection reliability and backing reflection interfering with registration.

CAPAMA's technical team shares these practical tips:

• Use dedicated photoelectric sensors: CAPAMA's transparent-material sensors can detect registration marks through clear film — something standard sensors cannot do
• Add white ink undercoat: Print a white layer first as an opaque base, then print colors on top for dramatically improved saturation and opacity
• Control UV curing power: Transparent materials transmit UV light readily. Use CAPAMA's multi-level UV power adjustment to find the optimal curing level
• Pay attention to the feeding system: CAPAMA's continuous unwind tension system with accumulator effectively reduces web handling defects on transparent materials

6. Daily Maintenance Checklist — Key to Extending Equipment Life

A well-maintained automatic screen printing machine can last 10-15 years, while neglected machines start having frequent issues after 3-5 years. Here is CAPAMA's recommended three-level maintenance system:

Daily (10 minutes before shift)

• Wipe squeegee and flood bar rubber with soft cloth and dedicated cleaner
• Check tension sensors for cleanliness and sensitivity
• Inspect UV lamp surface (ink mist buildup reduces UV efficiency by up to 50%)
• Verify all emergency stop buttons function properly

Weekly (approx. 30 minutes)

• Lubricate THK linear guides and moving parts (CAPAMA uses THK guides as standard)
• Check drive belt tension, adjust if necessary
• Clean pneumatic splicing table cylinders and solenoid valves
• Check unwind/rewind air shaft air-tightness

Monthly (1-2 hours)

• Thoroughly check electrical cabinet terminal connections
• Clean UV system reflectors and quartz glass plates
• Inspect vacuum printing table air-tightness and flatness
• Replace wear parts (squeegee blades, vacuum belts, air filters, etc.)

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