Simplified Optimization Design of Sheetfed Printing Press Delivery Chain

Release Date： 2024-05-28 19:40:22 View Count： 0

The paper collection mechanism, as a vital component of printing equipment, directly influences the overall performance of the printing press. Currently, mainstream printing presses employ chain-driven paper collection systems. Rapidly designing a chain transmission system that satisfies both the paper collection requirements of the printing press and maximizes transmission power holds significant implications for enhancing printer performance and reducing costs. A chain transmission system capable of bearing greater loads allows for relaxed constraints in the design and manufacturing of the paper gripper shafts and rows, thereby contributing to reduced design and production expenses. Consequently, there is a need for mechanical optimization of the paper collection chain's parameters.

Chain drive, involving the use of chains as flexible traction elements between two or more sprockets, is a common mode of mechanical power transmission. Traditional chain drive design involves initially estimating the number of teeth on sprockets, the chain pitch, and the number of chain strands based on experience, followed by calculating power and the speed of the smaller sprocket based on transmission conditions. The maximum transmittable power for a single-strand chain under specific conditions is then determined from a chain power capacity chart, guiding the selection of the chain pitch. However, this conventional method is empirical, time-consuming, and does not consistently yield optimal designs.

In the context of printing machines, where paper collection chains must conform to the specific demands of printing processes, the design often faces unique constraints. Taking the domestically prevalent J2108A sheet-fed offset printing machine as an example, we will outline the conditions that paper collection chain designs should adhere to and discuss how to optimize such designs.

Conditions and Principles Governing Paper Collection Chain Design

Proper Paper Handover Conditions

To ensure seamless transfer of the substrate (commonly paper) from the impression cylinder to the paper collection chain, two conditions must be met: (1) At the handover point, the linear velocity of the paper grippers equals the peripheral velocity of the impression cylinder; (2) For every working cycle of the machine, when the leading edge of the substrate on the impression cylinder reaches the handover point, the paper grippers should also be at that position.

To fulfill the first condition, typically, the driving sprocket of the paper collector is mounted on the same shaft as the transmission gear engaging with the impression cylinder gear (which usually has the same number of teeth). Positioning the gripper pads on the pitch circle of the transmission gear ensures the gripper speed matches the pitch circle speed of the gear. Given that the peripheral speed of the impression cylinder equals the gear pitch circle speed, it guarantees that the gripper speed matches the cylinder’s peripheral speed. To meet this requirement, the distance between two consecutive gripper rows on the chain (measured along the straight section) must be accurately calculated, known as the step distance (S) of the chain conveyor.

In a typical sheet-fed rotary press, each printed sheet corresponds to one full rotation of the impression cylinder. Therefore, within one rotation of the cylinder, the distance the chain moves (in the linear part) is defined. As the impression cylinder completes one revolution, so does the driving sprocket of the paper collection chain.

Through this optimization process, a paper collection chain mechanism is designed that not only meets the paper collection requirements of the printing press but also achieves maximum transmission power. This optimization design approach bypasses the intricacies and non-universally recognized optimality of traditional chain design procedures. While the chosen optimization method (the interior-point penalty function method) introduces a limitation where the optimized parameters are continuous values, which differ from the discrete values typically used in engineering applications for chain parameters, the overall outcome of the chain system designed through this optimization is superior to those designed traditionally, validating the effectiveness of the optimization approach.

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