The most important factor in any inverter's evaluation of a High Speed Two Color Flexo Printing Machine is not the speed shown in the brochure. Only with real speed can the machine produce products that meet quality standards without causing too much waste.
For example, when printing on 60g/m² paper, a machine rated 200m/min runs well at 180m/min. However, on BOPP films of 80 microns using the same ink system, the stability rate can be reduced to 120 m/min.
The reason for this difference is that different materials and working conditions change the way the printing process operates at high speed. Because of this, it is very important to understand the physical limits of flexographic printing in the actual production process beyond the rated motor speed.
Correct definition of "maximum speed"
The most important number for any converter evaluating a High Speed Two Color Flexo Printing Machine is not the speed shown in the brochure. Only with real speed of production can the machine produce products that meet quality requirements without causing too much waste.
This actual speed is always below maximum mechanical speed. The maximum speed in technical documentation can only show the mechanical speed of the machine. It is based on the motor's torque bearing load and vibration limits. It does not represent a steady rate of production.
Actual production speed depends on the substrate, ink system and drying method. These factors alter how the machine behaves in printing.
For example, when printing on 60g/m² paper, a press rated 200m/min can operate at 180m/min. However, when printing on a BOPP film of 80 microns using the same ink system, the stability rate can drop to 120 m/min.
As a result of this difference, the gap between rated and actual production rates is not fixed. It varies according to working conditions.
As a result, machine purchasing decisions based only on the highest speed ratings may lead to incorrect expectations of production output.
Limit 1: Drying time between stations
The most common speed limiter in flexographic printing is dryness. Ink must be changed from liquid to solid before the printing net touches the next stop or rolls. Offsetting occurs if dryness is incomplete. Wet ink moves from one layer of the drum to the next, making it a rejected defect.
For a wide range of paper and paperboard printing water-based ink systems, evaporation rate depends on temperature, surface airflow speed and ink formulation. According to the size of the drum, the two-color central imprint drum press stations between the spacing of 300 mm -800 mm. At 150m/min line speed, the 500mm interstation stay time is about 0.2 seconds. This time, even with the assist of hot air, the water evaporates for a short time.
The results show that evaporation rate shows a square root relationship with time under diffusion control. This is common in flexographic printing. Because of this, the length of the double dryer does not double. It increases allowable speed by about 41%. This explains why longer drying systems yield less at higher speeds.
UV ink system does not depend on evaporation. They are cured by radical polymerization rather than solvent loss. UV lamp system can cure ink in 0.05–0.10 seconds. This eliminates the limitation of dryness and reaches the pressure of mechanical limits. UV systems still have their limitations. The energy of the lamp must be uniformly across the width of the net and measured using the ISO 21377-1:2020 radiometry methods. Some substrates cannot handle UV heat or UV exposure. When energy levels are too high, they can turn yellow or degrade.
Constraint 2: Velocity registration dynamics
With the increase of speed, the registration accuracy between color stations is also getting worse. The control system of closed-loop registers has less time for error detection, calculation correction and application adjustment. This effect is most noticeable on a High Speed Two Color Flexo Printing Machine presses when startup acceleration. It also occurs when web tension is interfering with the unfolding or rewinding of the process.
The main factor of this system is the relationship between servo loop speed and disturbance frequency. The change in the tension of the reel is caused by the uneven expansion of the reel, the speed of the reel and the reel itself. At lower machine speeds, the interference is slow. The servo system can detect and correct it adequately.
At higher speeds, the disturbance frequency increases. When it approaches the servo system limit, usually 3-5 hertz in a standard flexo systems, the control system reacts late. This delay produces a small number of residual errors. The errors were repeated throughout the print site.
ISO 12647-6:2012 sets a limit of ±0.10 mm for registration of high-quality flexographic printing. Keeping the accuracy at 150-200m/min requires either faster servo systems or better control of web tension in the release phase. Either option increases costs or requires equipment upgrades. These changes do not increase the rated machine speed, but they do affect the actual stable production speed of registered printing work.
Constraint 3: Coupling of Substrate Properties and velocity
Even with machines, different substrates can limit printing speed. The main material factor is size stability. This means how much the material is stretched under tension in the print and how it returns when the tension is removed.
Paper materials have viscoelastic behavior properties. When pressed, they stretch and partially recover over time. Heavy paperboard (350+ g/m²) has a lower elongation than light paper and is therefore more stable at higher speeds. However, heavier paper will also increase the burden of impression cylinders. Ink transfer requires high pressure. This may increase the wear and tear of the plate and lead to changes in dot size during long-term operation.
The properties of PE, BOPP and PET are different. They stretch more easily in stressful situations. But they will recover quickly, if not overextended. This means that if tension is controlled to a small extent, the BOPP film can operate at high speed. If tension is too low, the network is unstable. If tension is too high, the film can be stretched permanently. This range becomes harder to control at higher speeds as vibrations from machine parts affect more web pages.
TAPPI T 494 om-92 and ASTM D882 are standard test methods for measuring tensile strength and elongation. These values show whether the substrate can handle the target printing speed without damage. This data should be used prior to production to determine safe operation speed.
Constraint 4: Anilox Roll Transfer Physics
The anilox roll is a ceramic cylinder with a unit for controlling the volume of printing plate ink. It moves at the same surface speed as a spider web only when the impression point does not slide. In real production, there are always mistakes. The photopolymer plate bends slightly under pressure. This creates a small speed difference between the surface of aniline oxidase and the surface of the plate surface. This difference changes the transfer of ink. It depends on pressure, plate hardness and line speed.
At higher speeds, two main problems emerged.
First came the inkjet. The ink bridge between the battery and the plate becomes unstable when the phenytoin battery leaves the contact area at high speed. This can be broken down into droplets. The droplets land outside the image area. The risk increases rapidly with speed. This has a lot to do with the surface velocity of the cube. This makes speed an important factor in splash formation. Viscosity of high ink can reduce splashing, but also reduce ink through the transfer fine anilox cells. This creates a trade-off between speed and image detail.
The second problem is cavity emptying. Each anilox cell must release all ink in contact with the plate in a short time. At higher speeds, this contact time becomes shorter. The ink flows out of the battery in less time. Some ink remained inside the cavity.
Research progress in Organic Coatings has shown that incomplete emptying can reduce ink transfer by 5% to 15% at speeds of more than 150 m/min. Specific values depend on battery shape, depth and ink properties. This means that the same ink and anilox setup can print lighter solids at 180m/min than at 100m/min on a High Speed Two Color Flexo Printing Machine. Must adjust pressure or ink viscosity to correct this change.
What speed figures actually mean
Taking into account the limitations of these interactions, in common production scenarios, the actual speed expectation of a two-color flexible printing press are as follows:
| Matrix | Ink system | Typical Mass-Speed Limit | Key Limiting Factor |
|---|---|---|---|
| 60–80 g/m² kraft paper | Water-based | 100–130 m/min | Station drying |
| 120–200 g/m² coated paper | Water-based | 140–170 m/min | Registration dynamics / dryness |
| 250–400 g/m² foldable cardboard boxes | UV Cure | 160–200 m/min | Plate wear and tear under high nip force |
| 40-80 μm PE film | Solvent/UV | 150–190 m/min | Web tension stability |
| BOPP 20–30 μm | UV Cure | 180–220 m/min | Ink transfer / cavity emptying |
The figures come from ordinary industry ranges. They are based on data sheets from equipment maker and independent process engineering research. They're not as many as they can be.
The low end of each interval matches hard job. These jobs require large printed area, tight alignment, and precise brand colors. High-end matches for each range job easily. These jobs require small print areas and loose tolerances.
Measuring and monitoring Speed-Dependent Quality
The best way to find a real speed limit for a job is to run a step ramp during installation. Start slow. It then rises at a rate of 10-20 metres per minute. At each step, check registration errors, solid ink density and drying quality using inline tools. Any point above its allowable limit is the maximum speed at which the job can be done. This speed can be different from the maximum rated speed of the machine, or the operator can think based on past performance.
Inline scanning densitometers (based on ISO 2846-1 solid density rules), automatic visual systems for registration checks and pinhole detection cameras provide real-time feedback. In this way, operators can get closer to the quality cap more easily. Without these tools, operators usually keep the safety margin between 15 and 25 percent below the actual limit. They do this to avoid creating hidden flaws. This safety margin translates directly into lost production.
Conclusion
The maximum speed of a High Speed Two Color Flexo Printing Machine is not a fixed number on a nameplate. It is a meeting point of dryness, registration movement, substrate steadiness and anilox ink transfer. All of this is tested against clear quality standards. The rating shows the theoretical capability of the machine. The actual speed you can get depends on how these restrictions relate to your specific material and job needs. Knowing which restrictions are most important for each job allows machine operators to make informed choices about buying equipment, planning job and improving processes. That's how you get the truest output. They do not waste time pursuing the highest speeds that physical processes cannot support, rather than theoretical speeds that physical processes cannot support.
Reference
- ISO 12647-6:2012. Printing Techniques-Manufacturing process control for Half-Tone Colour Separations, proofreading, and printing processes-Part 6: Flexographic Printing. International Organization for Standardization, 2012. (Registration tolerance ±0.10 mm specification, tone value increase control framework, mass class classification)
- ISO 2846-1:2017. Color and transparency of Graphic Arts Inks-Part 1: Sheet-Fed and web offset printing inks. International Organization for Standardization, 2017. (Solid optical density uniformity specification, threshold for acceptable deviation, reference standard for inline densitometers)
- ISO 21377-1:2020. Graphic technology-Radiometric Measurement of solidified Curing Radiation Intensity-Part 1: general principles. International Organization for Standardization, 2020. (UV curing intensity uniformity measurement methodology, distribution of light in web width)
- TAPPI T 494-om-92. Tensile Breaking Properties of paper and cardboard. Technical Association of the Pulp and Paper Industry, 1992. (Paper tensile strength, fracture elongation, velocity coupling analysis modulus calculation)
- ASTM D882-18(2022). Standard test method for Tensile Properties of thin plastic films. ASTM International, 2022. (Thin film substrate tensile testing, elasticity vs. plastic deformation behavior, modulus and elongation data for web shutters)
