The Critical Role of Blankets in Offset Printing and User’s Guide

1. The Importance of Blankets in Printing

　　The blanket, a critical component of offset printing presses, is wrapped around the transfer cylinder and serves as the key element of the impression assembly. It is a composite material consisting of a rubber coating bonded to a substrate—typically fabric—and plays an essential role in indirect planographic printing by efficiently transferring ink from the printing plate to the substrate.

　　◆The Function of the Blanket

　　During offset printing, the blanket transfers ink from the printing plate to the substrate, boasting excellent compressive resistance, high tack, and a smooth surface that enhances print quality. The textile layers of the printing blanket exhibit unique properties: each layer is meticulously composed of both synthetic and natural fibers, imparting varying degrees of strength and durability. This sophisticated construction enables the blanket to deliver outstanding ink-transfer performance in indirect planographic printing. As an indispensable transfer element in the printing process, the blanket plays a critical role: it efficiently transfers ink from the plate to the paper, while offering superior compressive resilience, rapid recovery, strong adhesion, and the ability to leave no residual tack. Its smooth surface and carefully engineered fabric structure ensure stable ink delivery, making it equally well suited for halftone reproduction and solid-area printing.

　　◆Manufacturing Process Characteristics

　　By combining multi-layer textile fabrics with synthetic rubber compounds and subjecting the assembly to controlled thermal and chemical treatments, printing blankets are endowed with outstanding performance. The manufacturing process for printing blankets is highly precise, involving the use of specialized multi-layer textiles and synthetic rubber compounds that undergo meticulously controlled thermal and chemical treatments to form unique compounds and structures, thereby delivering exceptional performance on printing presses.

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　　2. Selection and Installation of Blankets

　　◆Precautions for Purchase

　　Select appropriate specifications and materials—typically focusing on Japanese and European products—to ensure that you purchase rubber blankets that meet the requirements of your printing press. In China’s printing industry, a wide variety of printing presses are available, with Japanese and European models dominating the market, alongside machines sourced from Taiwan, the United States, Eastern Europe, and other countries. All of these offset printing presses rely on the precise transfer of printed images by rubber blankets. The quality of the rubber blanket directly affects the quality of the print; therefore, during the printing process, the rubber blanket plays a crucial and pivotal role.

　　◆Installation Steps

　　Install the blanket in the safe standby mode, ensuring it is securely fastened, and then slowly rotate the press to unwind and install the trailing end. Next, let’s review the blanket installation procedure and the required storage conditions. During installation, first confirm that the press is in safe standby mode and that the printing plate has been installed. Then insert the blanket’s leading end or clamp end into the winding shaft or locking mechanism shaft and secure it in place. If necessary, insert a spacer at the leading or clamp end and secure it firmly. Finally, shut down the press, depress the inching switch to gently rotate the cylinder, unwind the blanket and the spacer, return the press to safe standby mode, and insert the blanket’s trailing end into the winding shaft or locking mechanism shaft.

　　3. Storage Requirements for Blankets

　　◆Basic Storage Conditions

　　The storage environment should be dry, well-ventilated, protected from direct sunlight, and maintained at appropriate temperature and humidity levels, while keeping the material away from chemicals. Special attention must also be paid to the storage conditions for rubber blankets, as an optimal environment helps ensure stable performance and extended service life. Therefore, when selecting a storage location, it is essential to choose a dry, well-ventilated space that is shielded from direct sunlight and free from chemical exposure. In addition, regular inspection and maintenance are indispensable to keep the rubber blanket in optimal condition at all times.

　　◆ Packaging Inspection and Storage Precautions

　　Inspect the blanket for any damage, and stack and store it properly to prevent deformation and further damage. The blanket should be kept in a cool, dry environment away from heat sources to avoid direct sunlight, which can accelerate aging and desulfurization. To ensure adequate air circulation, it is recommended to hang each blanket on a support rod. If warehouse space is limited, blankets may be laid flat, but care must be taken to ensure that no heavy objects are placed on top of them; rolling the blanket into a cylinder is not the preferred storage method. After opening the blanket packaging and removing the protective cover, carefully inspect it for any signs of damage. New blankets may be bent due to their rolled packaging; allow them to lie flat for a period of time until they regain their original shape before mounting them on the press. When stacking multiple blankets, arrange them face-to-face or back-to-back to ensure that the fiber grain on the back of one blanket does not compromise the smoothness of the other. Blankets should be protected from compression to prevent tearing or loss of elasticity. At the same time, keep them away from light, heat, and humid air to avoid surface issues such as stickiness, skin formation, cracking, or hardening. The storage facility for blankets should be well-ventilated and dry, with a relative humidity of about 70% and a temperature of approximately 24°C. In addition, ensure that the blankets do not come into contact with chemicals such as acids, bases, oxidizing agents, and petrochemical products to prevent corrosion.