Devil buzzing of the dampening rollers and ink piling? Just find the root of the temperature difference.
In an indoor printing environment with a temperature of 20℃, when the Heidelberg press speed was increased to over 12,000 sheets per hour, the operators noticed a distinct 'buzzing' sound from the dampening rollers, along with wave patterns and localized ink piling on the roller surface. Initial inspections did not find mechanical wear or loose drive components, and it was determined that the issue was caused by imbalanced printing system operating parameters.
Problem Analysis and Troubleshooting Process
01/ Initial Response Measures
To improve the fluidity of the ink, the water temperature of the centralized supply system was first adjusted from 8℃ to 12℃. In theory, moderately raising the fountain solution temperature can improve ink transfer performance, but in practice it only slightly improved ink fluidity, with the piling of ink near the water roller and the rippling pattern only slightly relieved.
02/ In-Depth Cause Analysis
Through shutdown inspections and multiple rounds of observation, the root causes of the problem were identified as follows:
(1) Fountain solution temperature too low: The ink rollers (especially the form rollers) are in direct contact with low-temperature fountain solution, causing their surface temperature to drop significantly, the rubber layer to harden, and elasticity to decrease, resulting in uneven ink transfer. When ink rollers contact the plate, "slipping" or "insufficient shearing" occurs, preventing effective ink stripping and causing ink retention and accumulation.
(2) Blanket temperature too high: Due to prolonged high-speed operation of the printing press, the blanket generates heat from friction, increasing its temperature and creating a significant temperature difference with the low-temperature ink rollers, leading to a viscosity imbalance during ink transfer. The ink cannot fully transfer from the plate to the blanket, causing partial ink backflow or accumulation near the fountain roller area.
(3) Thermal stress imbalance causing abnormal water roller behavior: The water roller repeatedly contacts the cold ink roller and hot blanket, causing uneven thermal expansion and contraction, which triggers vibration and a humming noise, while also forming rippled ink marks on the surface.
Solutions and Implementation
The core idea of the solution is to balance system temperature differences and optimize heat transfer, shifting the adjustment focus from "simply raising water temperature" to "controlling blanket temperature and achieving system thermal balance." The specific measures are as follows:
(1) Adjust air volume: In the original setup, to maintain printing stability, the blanket area paper-pressure air was in a fully sealed state. Now, the blanket cooling air channel is opened 30%~50% to use air convection for gradual cooling, aiming to reduce the surface temperature of the blanket from the overheated state above 45℃ to an ideal working range of 38~42℃.
(2) Monitor ink roller temperature: Use an infrared thermometer to monitor the surface temperature of the form rollers in real time, ensuring it does not fall below 28℃. If necessary, the ink roller heating system can be activated or environmental temperature and humidity adjusted. The fountain solution temperature is restored to 10℃ (optimal balance point) to avoid excessive water temperature worsening ink emulsification.
Finally, thoroughly clean the form fountain roller and ink roller, remove accumulated ink and crusting, and recalibrate the pressures of the water and ink rollers to ensure even contact. Run the press at low speed for 10 minutes to confirm no abnormal sounds or rippling, then gradually increase speed to 15,000 sheets/hour.
Implementation Effect
The implementation effects are shown in the table below:
Technical Principles and Experience Summary
Thermal equilibrium is key to high-speed printing. In high-speed printing, ink transfer depends not only on pressure and wetting but is also greatly affected by temperature field distribution. If the ink roller is too cold, it will cause elasticity to drop and ink transfer to be poor; if the blanket is too hot, the ink viscosity will decrease, and transfer will be incomplete. Only by achieving a balance between hot and cold and avoiding excessive local temperature differences can production stability be ensured.
In addition, systematic thinking is superior to adjusting single parameters. Simply raising the water temperature cannot fundamentally solve the problem; on the contrary, it may exacerbate system imbalance. Coordination must be carried out across multiple dimensions, including the dampening system, ink path system, blanket, and environment.
This troubleshooting case indicates that under high-speed operation (15,000 sheets/hour) of a Heidelberg printing press, abnormal noises from the plate dampening roller and ink piling were not merely mechanical or lubrication issues. They were caused by systemic thermodynamic imbalance due to low temperature of the ink roller and high temperature of the blanket. By opening the blanket's paper pressure air duct to achieve moderate cooling, normal ink transfer was effectively restored, completely eliminating the abnormal phenomenon.
In high-speed printing, it is necessary not only to 'adjust water and ink' but also to 'adjust temperature and balance.' Temperature balance is the invisible guarantee of stable printing.