Cardboard printing color variation is a common issue in the industry, especially when manufacturing orders for large clients, who often have strict color requirements. Many cardboard factories fail to secure large orders due to this color variation issue. This article introduces several methods to control printing color variation.

1. Quality control from color swatches and color cards

The source of printing colors comes from the customer's color samples. If the samples are not accurately taken, the production unit cannot guarantee that the printed colors match the customer's expectations. After collecting the color samples from the customer, the production unit should compare the printed proofs with the samples, confirm the printing colors with the customer, and establish the upper and lower limits of the printing colors. After creating the color samples, the manufacturer must strictly ensure that they are kept in the care of designated personnel. It is recommended to replace the color samples and color cards every three months to maintain consistent hue, brightness, and saturation.

This ensures consistency in color between customers and manufacturers, allowing producers to receive accurate printing color specifications and exercise reasonable control within the color range.

2. Controlling from the ink wash

During the actual printing process, it is crucial to control the viscosity and pH value of the inks. When making proofs, confirm the ink's viscosity and pH value. After the customer confirms, re-produce and install the proof inks, then inspect and execute the viscosity, pH value, and ink fineness.

Before operation, mix the ink thoroughly and install the ink agitator pump in the ink supply system; if the ink is not stirred for a long time, the resins in the ink will settle, causing the ink color to darken. Therefore, adding an ink agitator pump is beneficial for controlling ink viscosity.

The key control of ink lies in data recording, using data values to control ink color, while employing an ink pump to regulate ink viscosity, allowing the resin within the ink to flow, thereby enhancing ink fluidity. This is one of the necessary conditions for maintaining consistent color.

3. Controlling speed from the machine side

The speed of the printing machine is a very critical factor; there's a significant difference in color quality between 70 sheets per minute and 180 sheets per minute. This is because the printing machine's rubber rollers have varying heights, and the vibration of the equipment differs with the speed; the vibration also brings about the ink amount between the rollers, and when the ink amount is increased, the color becomes darker. Therefore, it's important to maintain a consistent speed during both the printing setup and normal production to ensure uniformity in the printing process.

Ink application speed inconsistency can result in a batch of orders featuring varying shades of depth. Such occurrences are relatively common in factories, hence renowned companies often establish specific printing trial and production speed requirements based on the equipment's characteristics.

4. Control print pressure

To achieve consistent color across the same batch of orders, controlling the printing pressure is a crucial factor. Both excessive and insufficient printing pressure directly affect the color variation. The printing pressure of this machine encompasses two aspects: the contact pressure between the anilox roller and the plate, and the printing pressure between the plate and the paperboard. Therefore, to maintain consistent printing color, it is essential to keep the various printing pressures stable and even throughout the printing process.

The main influence on color from printing pressure is not significant; printing pressure has an indirect effect on the color characteristics of the printing. It is advisable to be slightly gentler in controlling the printing pressure.

Ensure the engraved roller is spotlessly clean.

In addition to the above four points, ensure that each printing unit's anilox roll is thoroughly cleaned before printing. Because if there's a clogging in the anilox roll's grooves, it will affect the evenness of ink transfer, resulting in uneven colors in the printed images.

The cleanliness of the anilox roller is crucial; a blocked mesh directly reduces the ink laydown, resulting in pale colors and insufficient color saturation. Therefore, regular cleaning and inspection of the printing press's anilox roller are necessary.