Paper Slitting Rewinding Machine

The 2023 labelexpo Asia show we participated in in December was a complete success.

I am very happy that many customers from Russia, the Middle East, and Southeast Asia are very interested in our printing machines, slitting machines, and die cutting machines.

There are also customers who place orders directly after discuss with us about machine details in exhibition. Thank you for all the customer trust and support. We will continue to update, bring better machines and services to our customers.

Achieving consistently close tolerances in slitting operations – whether for metal foils, plastic films, paper, or nonwovens – is critical for product quality, downstream processing, and customer satisfaction. Minute variations in slit width, edge quality, or camber become major defects when specifications are tight. Success hinges on meticulous attention to five core operational pillars: Setup, Tension, Knives, Handling, and Maintenance.

1. Proper Setup:

Machine Alignment: Before any material runs, verify critical alignments. This includes the arbor (ensuring cores run true), the slitter shaft (parallelism to the unwind/rewind), and the entire sliitting machine base. Laser alignment tools are invaluable for precision.

Core Selection & Mounting: Use cores that are perfectly round, straight, and of the correct inner diameter for the shaft. Ensure cores are mounted securely without slippage or distortion. Concentricity errors here propagate through the entire slit.

Knife Positioning (Slitting Head Setup): Precisely set the slit width according to the work order. Use calibrated gauges or the machine's digital readout (if available and verified). Double-check settings before starting. Ensure all knives are locked securely in their positions.

Web Guiding: Set initial guide positions to center the web accurately before it enters the slitting zone. This prevents uneven tension and biased cutting.

Program Verification: If using programmable settings (tension profiles, speeds), ensure the correct program is loaded and parameters match the job requirements.

2. Tension Control:

Consistency is King: Fluctuating tension is the enemy of tolerance. Maintain uniform tension from unwind, through the slitting zone, to rewind. Even small variations cause width changes, telescoping, edge waves, and camber.

Zone Control: Modern slitters have independent tension zones (unwind, slitting, rewind). Calibrate load cells and dancers regularly. Set appropriate tension levels for the material – too low causes slippage and poor tracking; too high stretches the material and distorts edges.

Taper Tension (Rewind): Essential for building a stable, telescopefree roll, especially with compressible materials. Apply higher tension at the core, gradually reducing it as the roll diameter increases. Improper taper causes edge damage, starring, or loose wraps affecting slit width consistency.

Material Awareness: Different materials (thin film vs. thick steel) require vastly different tension strategies. Understand your material's modulus of elasticity and yield strength.

3. Knife Angles & Configuration:

Sharpness: Dull knives crush, tear, or burr material instead of cleanly shearing or scoring it, instantly ruining edge quality and dimensional tolerance. Implement a strict sharpening/replacement schedule based on material abrasiveness and run lengths.

Correct Knife Type: Select the right knife for the material and slit type:

• Razor Slitting: Ideal for films, papers. Angle affects cut initiation and debris generation.

• Shear (Rotary) Slitting: Mandatory for thicker/fibrous materials. Involves precise clearance and overlap between upper and lower knives.

• Crush Cut: Less precise, generally not for close tolerances.

Angle Optimization:

• Razor: Adjust the blade angle relative to the web. A steeper angle often provides a cleaner cut on films but may wear faster. Find the optimal balance.

• Shear: Clearance (gap between upper and lower knife edges) and Overlap (radial depth of cut engagement) are critical. Refer to manufacturer charts but fine-tune for specific material. Too little clearance causes excessive force and burrs; too much causes ragged edges. Incorrect overlap affects cut quality and knife life.

Parallelism & Runout: Knife holders and arbors must be true. Minimal radial runout on rotary knives is essential to prevent "chatter" marks and inconsistent edge quality.

4. Material Handling:

Controlled Environment: Minimize drafts, temperature swings, and humidity fluctuations, especially for hygroscopic materials (paper, some films) which can dimensionally change.

Splice Integrity: Use strong, low-profile splices. A failing splice or a thick splice can jam, cause tension spikes, and ruin slit edges as it passes through knives.

Edge Guidance: Maintain the web perfectly centered through the slitting zone using active web guides. Off-center webs lead to uneven slit widths and poor edge quality on the outer strips.

Roll Handling: Use proper equipment (cranes, shaft lifters) to load/unload rolls. Avoid impacts or dropping cores/rolls, which can damage cores and affect mounting concentricity. Handle slit rolls carefully to prevent edge damage or deformation.

Debris Management: Keep the slitting zone clean. Accumulated debris (especially with shear slitting) can deflect the web, interfere with knives, or get embedded in rolls.

5. Machine Maintenance: 

Preventive Schedule: Adhere rigorously to the manufacturer's PM schedule. This isn't just lubrication; it includes checking alignments, bearing conditions, belt tensions, gear wear, and pneumatic/hydraulic systems.

Lubrication: Use the correct lubricants in the specified amounts at the required intervals. Over- or under-lubrication causes wear and vibration.

Component Wear Inspection: Regularly inspect critical components: bearings, shafts, gears, couplings, brakes, clutches, dancers, and guide sensors. Worn components introduce vibration, slippage, and misalignment – all tolerance killers.

Calibration: Periodically calibrate tension sensors, load cells, pressure gauges, and any digital positioning systems. Relying on uncalibrated instruments guarantees drift.

Cleanliness: A clean machine runs better and allows for easier inspection. Remove dust, grease, and debris buildup, especially near bearings, guides, and sensors.

Conclusion

Attaining and holding close tolerances on a slitter isn’t a single magic setting but a holistic discipline. It requires focus on Proper Setup, Tension Control, precise Knife Angles, careful Material Handling, and consistent Maintenance—turning it from a simple cutter to a precision tool for strict-spec, high-quality slits. It’s a continuous cycle of monitoring, adjustment and refinement.

FAQ

Q: What if slitting tolerances are outside the specified range?​

A: Check machine setup (knife/roller alignment, tension), material feeding/quality. Inspect knives for dullness/damage; recalibrate or adjust angles if needed.​

Q: How to determine appropriate tension for different materials?​

A: Refer to material specs and machine manual for ranges. Test different settings to find optimal tension (clean cuts without stretching/deformation).​

Q: How often to sharpen slitting knives?​

A: Depends on material, machine speed, and knife hardness. Sharpen when cut quality drops (burrs, unevenness). High-volume production may require daily/weekly sharpening; track cut counts for scheduling.​

Q: What causes material wrinkling during slitting?​

A: Uneven tension, misaligned guide rollers, or pre-existing material defects. Check tension consistency, adjust rollers, or flatten material before feeding (use straightening devices if needed).​

Q: How to maintain machine calibration?​

A: Follow manual procedures (use reference materials, adjust instruments/systems). Calibrate at least annually; more frequently for heavy use or environmental changes.

That triumphant feeling of peeling off a price tag or product label is often short-lived. Left behind is the dreaded sticky residue – a gummy, stubborn mess that seems impossible to remove. Don't despair! Whether it's on glass, plastic, ceramic, or metal, conquering sticky labels is possible with the right approach. Here’s your battle plan:

Essential Principles:

1. Patience is Key: Rushing usually leads to scratches or spreading the glue.

2. Test First: Always test your chosen method on a small, inconspicuous area first to ensure it doesn't damage the surface (paint, finish, etc.).

3. Start Gentle: Begin with the mildest method and escalate only if needed.

4. Work the Edges: Lift a corner and work slowly, ideally peeling the label and residue off together.

Your Arsenal of Removal Methods:

1. The Gentle Peel (Best for Fresh Labels):

How-To: If the label is relatively new, try slowly peeling it back at a very low angle (almost parallel to the surface), applying gentle, steady pressure. Heat from your fingers can sometimes help soften the glue slightly.

Best For: Easily accessible, not overly stubborn labels on smooth surfaces.

2. Heat Power (Hair Dryer or Heat Gun):

How-To: Set your hair dryer to medium heat or a heat gun to low (keep it moving constantly!). Warm the label for 30-60 seconds, focusing on the edges. The heat softens the adhesive. Carefully lift a corner with a fingernail or plastic scraper and peel slowly while warm.

Best For: Plastic containers, glass jars, metal. Avoid on thin plastic (can warp), painted surfaces (can damage paint), or sensitive electronics. Keep heat away from flammable materials!

3. Oil Power:

How-To: Apply a generous amount of oil (or oil-based food) directly onto the sticky residue. Let it soak for 15 minutes to several hours. The oil breaks down the adhesive bond. Wipe away the residue with a cloth or paper towel. Clean the surface thoroughly with soapy water afterward to remove oily film.

Best For: Glass, ceramic, metal, some plastics. Test on plastics first, as oil can sometimes stain or cloud certain types. Avoid porous surfaces like untreated wood.

4. Rubbing Alcohol:

How-To: Dampen a cloth or cotton ball with rubbing alcohol. Rub firmly over the sticky residue. The alcohol dissolves many types of adhesive. Wipe clean with a damp cloth. May require a few applications.

Best For: Glass, metal, most hard plastics, countertops. Test first! Can damage some plastics (causing cloudiness or crazing), varnished wood, painted surfaces, or certain finishes. Use in a well-ventilated area.

5. Commercial Adhesive Removers:

How-To: Follow the product instructions carefully. Apply a small amount to the residue, let it sit for the recommended time, then wipe away with a cloth. Often very effective.

Best For: Tough residue on glass, metal, many plastics. ALWAYS test on an inconspicuous spot first! Can be harsh on some surfaces. Use in a well-ventilated area. Clean the surface thoroughly with soapy water afterward.

6. White Vinegar:

How-To: Soak a cloth in undiluted white vinegar and lay it over the residue for 10-15 minutes. Rub the area. Vinegar's acidity can help break down some adhesives. Rinse well.

Best For: Glass, some plastics. Less potent than other methods but gentler.

7. Baking Soda Paste (For Stubborn Residue):

How-To: Make a paste with baking soda and a little water or cooking oil. Apply to the residue, let it sit for 5-10 minutes, then gently scrub with an old toothbrush or cloth. Wipe clean.

Best For: Surfaces where gentle abrasion is acceptable (glass, ceramic, some metals). Helps lift residue dissolved by oil.

Prevention is Easier Than Cure: The Role of Quality Labels

While removal techniques are valuable, the best experience starts with the label itself. High-quality labels applied correctly leave minimal residue. This is where manufacturing precision makes a huge difference.

A Label Die Cutting Machine plays a crucial role. This specialized machine doesn't just cut the label shape; it precisely controls the depth of the cut. Optimal die cutting ensures the label's adhesive layer is cleanly cut through without cutting into the backing paper too deeply. Why does this matter?

Cleaner Release: Precise cutting allows the label to peel cleanly off its backing.

Less "Ooze": Prevents adhesive from bleeding excessively around the edges of the label during application.

Easier Application: Labels come off the backing smoothly.

Easier Removal: Labels designed and cut with removal in mind, combined with adhesives formulated for clean release (like removable adhesives), significantly reduce the sticky residue left behind.

A stack flexo printing machine is a type of flexible packaging and label printing equipment characterized by vertically stacked printing units, each positioned independently on a central frame or "stack." This design allows each color station (typically 4–10 units) to be mounted on either side of a main frame or along a vertical column, enabling versatile configuration for multi-color printing on flexible substrates like paper, plastic films, foil, or corrugated board.

Key Components & Working Principle

The machine consists of core components:

• Printing Units: Each unit holds a flexible relief printing plate (flexographic plate) mounted on a plate cylinder, paired with an anilox roller for precise ink metering.
• Unwinding & Rewinding Systems: Feed the substrate through the machine and collect the printed material.
• Drying Systems: Infrared or air-drying tunnels cure solvent-based or water-based inks between color layers.

Operation follows a stepwise process: the substrate passes through each printing unit sequentially, with each unit adding a different color. The stack configuration allows easy access to individual units for quick plate changes, making it ideal for short-to-medium print runs.

Applications & Advantages

Stack flexo machines excel in packaging production (e.g., food wrappers, beverage labels, shopping bags) and corrugated box printing. Their key benefits include:

• Flexibility: Adaptable to various substrate thicknesses and widths, with quick setup for job changes.
• Cost Efficiency: Lower initial investment compared to satellite-style flexo presses, suitable for small businesses or frequent design updates.
• Space Savings: Vertical stacking minimizes floor space usage, though alignment precision relies on operator expertise.

Equipment Selection & Maintenance Tips

1. Choosing the Right Stack Flexo Press

When selecting a machine, prioritize:

• Substrate Compatibility: Ensure the press handles your target materials (e.g., PVC, polyethylene, or paperboard).
• Color Capacity: Match the number of printing units to your typical color requirements (e.g., 6 units for full-color CMYK + spot colors).
• Drying Technology: Solvent-based inks need robust drying systems, while water-based inks may require gentler air-flow setups.
• Automation Level: Semi-automated models reduce manual adjustments, but fully automated presses improve consistency for high-volume runs.

2. Maximizing Performance Through Maintenance

Regular upkeep ensures optimal print quality and longevity:

• Clean Anilox Rollers: Use specialized brushes or ultrasonic cleaners to remove dried ink buildup, which causes streaking or uneven ink transfer.
• Inspect Print Plates: Replace worn or damaged flexo plates to avoid blurry edges or missed details.
• Lubricate Moving Parts: Grease gear trains, bearings, and guides to prevent friction-related downtime.
• Calibrate Tension Systems: Uneven substrate tension leads to registration errors—verify sensor accuracy monthly.

Stack flexo printing machines offer a balance of versatility and affordability for packaging and label production. Proper selection based on production needs, combined with proactive maintenance, ensures consistent output and cost-effective operation in dynamic printing environments.

1. Overview

A flexo printing machine uses fluid ink and a roller system to transfer images onto substrates. Ink flows from the ink pan via an ink fountain roller to an anilox roller, which distributes precise ink volumes to the raised image areas of flexible relief plates. An impression cylinder applies pressure to transfer ink to substrates like paper, plastic, or corrugated board, followed by drying—using hot air or UV light. Its simple design enables easy operation and high-speed production, making it ideal for packaging and label printing.

2. Naming Origin

The term "flexographic" stems from early corrugated cardboard printing needs. Rigid plates failed on its uneven surface, so flexible plates were developed to conform to ridges and valleys. To prevent ink smudging on unprinted "high points," non-image areas of the plate were deeply recessed. "Flexo" highlights the plates' adaptability, while "graphic" refers to image transfer—capturing the technology's core: flexible, deeply etched plates for rough substrates.

3. Key Features

4. Applications

Flexo machines excel in:

• Packaging: Corrugated boxes, food pouches, and pharmaceutical cartons.
• Labels: Self-adhesive retail labels, shrink sleeves, and industrial tags.
• Specialty: Textile banners, metallic packaging, and embossed surfaces.

5. Technology Comparison

Conclusion

Flexo printing balances simplicity, cost-effectiveness, and versatility, making it a key technology in modern industrial printing. While offering moderate resolution, advancements in plates and automation enhance precision and sustainability, ensuring its relevance in diverse applications from packaging to specialized labeling.