A Complete Guide To CI Flexo Printing Machines And Their Working Process

The CI flexo printing press (Centre Impression Flexo Printing Press), also known as a center-impression cylinder flexo printing press, is a high-end model in the flexographic printing industry. Its core features a shared, large-diameter central impression cylinder surrounded by multiple printing groups. It has the advantages of strong structural rigidity, high precision, and stable tension, and is widely used in the field of carton preprinting, soft packaging, building materials printing and so on. It can be printed on a variety of substrates, including paper, plastic, aluminum foil and non-woven fabrics. The following is a comprehensive analysis of the equipment's core components, workflows, key parameter settings, operational security and maintenance:
1.CI Flexo Press Core Components
The stable operation of a CI flexo printing press depends on the coordinated operation of various systems, including eight core components:
Transmission mode: There are two kinds of mechanical gear transmission and electronic shaft gearless transmission. The latter provides higher accuracy, making each printing unit independently and synchronously controlled, suitable for high-speed printing.
The unwinding device supports single, double or flip doublestation designs. It is equipped with a tension control system that uses a floating swing arm to detect changes in web tension, ensure smooth unwinding of printing materials and prevent stretching and deformation.
The printing device's core is a large diameter central impression cylinder (with a double-walled structure for temperature control). Multiple printing groups were evenly distributed around it. Each group includes a plate cylinder, anilox roller, doctor blade and pressure adjustment mechanism. The anilox roller is responsible for measuring metered ink transfer, pressure adjustment mechanism precisely control of the printing plate and the anilox roller, printing plate and impression cylinder contact pressure.
Ink system consists of ink fountain, ink pump, ink circulation piping and ink knife. Water, UV curing or solvent inks can be delivered according to printing requirements. doctor blade removes excess ink from the surface of the aniline oxidase roller to ensure a uniform ink layer thickness. Drying System: includes an interstitial drying device (used to prevent colour mixing immediately after each colour is printed) and a final drying unit (mainly a bridge dryer). It adopts a combination of hot air drying and UV curing, which can be adapted to different ink types while taking into account drying efficiency and environmental protection.
Cooling System: Hollow drum water cooling system cooling central impression cylinder and winder assembly, prevent material deformation due to high temperature, ensure printing accuracy.
Reel device: symmetric with the reel device, support double position reel, automatically switch between reels, maintain the reel tension uniform, ensure a flat and tight finished reel.
Control System: based on touch screen, set tension control, register adjustment, speed control, fault warning and other functions in one. High-end model supports IoT connectivity for remote monitoring and data traceability. ii. Complete Workflow (from preparation to completion)
(I) Pre-Printing Preparation (laying the foundation for Printing Quality)
Material Preparation and Inspection
Substrates: Specification (thickness and width) according to printing process sheet. Check that the surface is smooth, wrinkle-free and undamaged. Subscribers are allowed to sit in the workshop at least 24 hours in advance to acclimate temperature and humidity conditions (20 -25°C for paper printing, 50% -65% per cent humidity; 50 per cent humidity for film printing).
Inks and Auxiliary Materials: Choose inks that match the substrate (e.g., water-based/UV ink are preferred for food packaging). Check the color and viscosity of the ink (20 to30 seconds per 4 cups is recommended for flexographic inks). Add the appropriate proportion of diluent or desiccant and stir thoroughly. Prepare auxiliary materials such as anilox roller cleaner and lint-free cloth. Print & Anilox Roller: Verify that printing plate image is intact and the the anilox roller cell is ≥ ≥ 95% smooth. the anilox roller line count is selected according to the count of printing nets (recommended ratio: 1: 4). Ceramic anilox rollers abrasion resistance and stable ink transfer is the first choice.
Equipment Inspection and commissioning
Cleaning and maintenance: cleaning of surfaces of all equipment cylinders (central impression cylinder, plate cylinder and anilox roller), removal of residual ink and dust, and ensuring no scratches (scratch depth ≤ 0.01mm). Clean inkjet and ink supply lines to prevent cross-contamination of different colors of ink.
Component Installation: When installing printing plate, make sure the surface is smooth, free of bubbles and wrinkles, with seam line facing up to the middle. Tighten the bolt to the specified torque (to prevent radial runout). Install and lock the anilox roller. Adjust the angle of the doctor's blade (25°-35°, tangent with anilox roller) and pressure to ensure even trim. Safety checks: Verify that the emergency stop button is sensitive and effective (braking time ≤ 2 seconds), that the guardrail is intact (height ≥ 1.2 meters), that the ventilation system and flammable gas detector are functioning properly, and that the firefighting equipment is valid. Operators must wear protective gear (solvent resistant gloves, safety glasses, masks, etc.).
Parameter Preset
Basic Parameters: Print speed (300-120m/min, rated 50% for test printing) and drying temperature (70-120°C, UV curing capacity adapted to ink requirements) according to flow sheet.
Pressure and tension: Initially adjust the contact pressure between the plate and the anilox roller (to ensure uniform printing ink) and between the plate and the central impression cylinder (to ensure clear image transmission, pressure deviation ≤ 0.01 MPa). Set tension residuals for the reel, print, and reel sections to ensure that the reel runs smoothly without stretching. (II) Printing Processes (Core Processes, Real-Time Monitoring and Adjustment)
Start and test run
Start the machine and run on empty for 3-5 minutes. Check that the components are operating smoothly, there is no abnormal noise and the transmission system is lubricated well. Start the ink system and let the ink cycle for 10-15 minutes to ensure that the ink is evenly distributed on the surface of the anilox roller surface.
Pre-registration: the control system activates the pre-registration function of the plate roller, automatically adjusts the position of the plate roller. Manually adjust the deviation to ensure baseline alignment for each color group.
Test Printing and Calibration
Slow Test run: 5-10 runs at around 30m/min. Key indicators were then sampled and examined: image clarity, ink color uniformity (density deviation ≤ 0.05), registration accuracy (horizontal/vertical deviation ≤ 0.1mm).
Parameter Adjustment: If registration is inaccurate, the cylinder position is fine-tuned through control system system (≤ 0.05mm per adjustment). If the ink color is not uniform, can adjust the anilox roller pressure or ink viscosity. If there is a stain on the plate, please reduce the printing speed or pressure.
Official Printing
Accelerate: After calibration, gradually increase the printing speed to rated. Full monitoring the equipment's operating status: check whether web tension is stable, drying temperature is within the prescribed range, no ink leakage, neatly winding.
Quality Inspection: Sample every 10-15 minutes, check registration accuracy with magnifying glass, measure ink density with densitometer. Observe equipment alarm signals, timely processing of input paper, ink level fluctuation and other anomalies.
Real-time Registration Correction: Watch device monitors for tracking color spots, use electronic eye recognition to automatically track registration deviations, and constantly fine-tune to ensure accurate multicolor overlays.
(III) post-printing finishing (to ensure the quality of the finished product and the useful life of the equipment)
Shut down: When printing is complete, reduce the printing speed to 50% of the rated value and stop feeding. When the final print enters the winding table, close the the inking and drying systems. Turn off the main power supply when the equipment is completely out of service. Cleaning and Maintenance
Ink cleaning: Wash ink ink fountain benzene ether rollers, doctor doctor blade plates printing plate a special cleaning agent to remove any residual ink (especially UV ink, which should be cleaned promptly to prevent solidification and blockage). Remove printing plate and store them securely (out of direct sunlight and heat sources).
Equipment Cleaning: cleaning the surface of central impression cylinder and cooling roller, wiping the exterior and operation panel of the equipment. Check the lubrication of transmission system (such as gears and chains) and replenish lubrication oil.
Classification and inspection of Finished Product Sorting: marking of drum according to batch number and specification, inspection of drum smoothness, stain and adhesion. Samples are collected for final quality inspection (register accuracy, ink color consistency and dryness). Acceptable samples are stored in warehouses. Rejected products are individually labeled and analyzed for reasons.
Recording and archiving: Fill out a production log form recording printing parameters (speed, pressure, temperature), material consumption, quality inspection results and equipment performance for future reference. III. Key Parameter Settings and Optimization Techniques
Tension control: Unwind tension should be slightly greater than withdrawal tension. Low tension applies to easily stretched materials, such as film, to prevent web deformation. Feedback from the floating swing arm can adjust the motor speed in real-time to ensure ≤ ± 5% tension fluctuations.
Register Accuracy Optimization: this depends on constant temperature control of the central impression cylinder (temperature fluctuation ≤±2°C). Preheat the device for 30 minutes before printing. Enable the "Acceleration/Deceleration Register Compensation" function high-speed printing to avoid bias due to speed fluctuations.
Ink Volume control: The number of lines of the roller determines the volume of the underlying ink (high line = thin ink layer = fine print; low line = thick ink layer = solid print). The more pressure on the blade, the less ink volume. Balance pressure with image clarity to avoid scratching the anilox roller. Matching Drying Parameters: Hydrating ink requires a longer drying time, which can be adjusted by increasing the speed of hot air. UV inks requires sufficient curing power (can be adjusted according to printing speed to avoid uncured ink and stain). drying temperature between colors should be 10-15°C below the final drying temperature to minimize substrate deformation.
IV. INTRODUCTION Operation Safety and Common Troubleshooting
(I) Safety Operating Guidelines
Operators must have professional training and pass the examination before they can take up their duties. When printing machine or using solvent type ink, must hold special operation license.
Do not open the guardrail while the device is operating. Do not touch rotating parts (rollers, chains) by hand. Long hair should be tied back with a work cap, not jewelry.
Work areas with solvent-based inks must be ventilated (exhaust speed ≥ 0.5 m/s). No open fires. Periodic inspection of flammable gas detector (alarm concentration ≤ 25% minimum explosive limit).
In the event of an emergency (such as ink leak or equipment jam), press the emergency stop button immediately and cut off the power supply before operating. (II) Common Faults and Solutions
Fault Type Common Causes
Mismatch: Tension fluctuation, plate loosening, abnormal center platen temperature. Adjust tension controller, tighten plate bolts, check cooling system to ensure constant temperature.
Uneven ink color: Unstable ink viscosity, clogged anilox roller, doctor blade angle is not suitable. the ink viscosity, clean the anilox roller, and adjust the doctor blade angle (25°-35°).
Blurred images/text: printing pressure, speed, or ink drying delay. Reduce the platen pressure, slow printing speed, increase drying temperature, or extend drying time.
Substrate deformation: excessive temperature and tension. Reduce drying temperature, adjust water cooling system, reduce release/release tension.
Poor ink adhesion: Ink and substrate incompatibility, surface untreated. Replace appropriate ink and corona treatment of substrate (film).
V. Equipment Maintenance and Care Recommendations
Daily maintenance (after daily operations): cleaning all rollers and cartridges, checking for wear and tear on the doctor blade (replacing it if it is badly worn), recording equipment operating parameters and anomalies.
Periodic maintenance (weeks/months): check the lubrication of the drive system, replenish lubricating oil weekly; calibrate the register control system, tension sensor and temperature meter monthly, check the anilox roller for wear and tear (replace if wear is excessive).
Long-term maintenance (annual inspection): carry out precision inspection and repair of central impression cylinder, check whether electrical system wiring is aging, replace seals, bearings and other vulnerable parts, and calibrate the accuracy of the whole machine.
Environmental maintenance: Regular cleaning exhaust gas recovery systems (RTO/RCO equipment), replacement of adsorbent materials, ensuring that VOC emissions meet standards (TVOC ≤ 80 mg/m3) and meet the latest 2025 environmental standards.