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Reasonable and scientific production scheduling can shorten the production cycle, ensure the continuity of production, reduce material consumption, and increase equipment utilization. Production scheduling optimization is based on the overall optimization theory. To optimize production scheduling, we must first find the bottleneck process in the process. The bottleneck process is the process with the lowest production capacity. It determines the overall production capacity and is the biggest limiting factor of the entire process.
Due to the large number of plate-making equipment and high speed, it can meet the printing needs. The postpress processing of newspaper printing is only tied, and general newspaper printers are equipped with receiving and bundling units that are integrated with printing and have no impact on the printing speed. Therefore, the bottleneck process in newspaper printing is printing, which determines the printing capacity of the entire newspaper. Here, printing is selected as a breakthrough for scheduling to study the optimization of scheduling in the printing process.
When printing production scheduling, we must first arrange the print production operation plan, determine the production equipment and production time of the job, and then real-time scheduling according to the job plan. When planning a print job, it is necessary to assign the live job to the printing equipment according to the equipment's production ability, and then arrange the job's printing order according to the characteristics of the job. The specific method and steps are:
1. Group jobs and equipment
In the study of the production scheduling problem of the parallel processing equipment group, the smaller the number of processing equipment and the number of production tasks, the simpler the production scheduling model is established, and the easier it is to obtain the optimal solution. In the printing production of newspapers, there are many newspapers and printing equipment and printing equipment, which make the production scheduling problem very complicated. In order to simplify the problem, a grouping method can be adopted to group similar newspaper jobs into a group, and as a task, printing equipment with the same performance can be grouped together.
First group newspapers and put similar newspapers in one group. The main considerations are the number of prints, the time of receipt, the version, color, paper path, and paper type.
The grouping of the printing equipment depends on the type of equipment, and the same unit should be able to use a common printing plate with physical locations nearby. There should not be too many devices in each group, and it is better not to exceed 3 units. Otherwise, there are secondary scheduling problems.
2. Optimize the combination between job groups and device groups
When scheduling work, estimate the time required for the job group to print properly in different units. First of all, the arrangement of the job group should be suitable for the requirements of the model. Each press's printing, paper path, ink, and folding methods have been set up. Changing settings is a waste of time. For example, when a single paper path double-sided color printing is replaced with two-paper double-sided two-tone printing, it only takes half an hour to change the ink. Therefore, it is necessary to arrange jobs according to the settings of the printing machine. At the same time, in order to ensure that the time span for printing production is the smallest, the principle of production load averaging should be adopted in the job arrangement, and the large-volume job group and the equipment group with large operating capacity should be combined.
3. Arrange job production time
There are multiple jobs in each job group and the print production time of each job needs to be arranged. The general principle is: first to receive the original plate-making printing of the manuscript, the first to be published in the newspaper to be printed first, and the newspaper in the large-volume newspaper to be printed first.
The time taken for a printer to receive a clear draft of a newspaper is basically fixed. The time for sending news in a news newspaper is late, and the time for printing is short. After the printing factory receives the draft, it must be immediately printed and printed; the supplements, special issues, and weekly newspapers are sent. The time for the manuscript was earlier and the time reserved for printing was relatively long. Such newspapers should be pre-arranged for printing, and strive to complete the printing task before the first type of newspaper is opened.
At the same time, when the job is arranged in the printing sequence, the similar jobs are arranged as much as possible, which can reduce the change of the printing settings and save preparation time. For example, if the paper and ink used by the two newspapers printed by the same printing press are the same, they can be replaced together, eliminating the need for ink exchange and paper change operations and reducing the time and cost of preparation for work.
In addition, due to the fact that when the job is grouped, the printing time of the job is not fully taken into consideration, it may cause a conflict in printing time. In this case, you can make appropriate adjustments between groups and groups. The job scheduling is also a check on the rationality of the combination of the job group and the printing unit.
4. Implement dynamic scheduling
During print production, scheduling is performed according to the operation plan, and the production job sheet for each job is delivered to the plate making and printing shop, and each shop is produced according to the job ticket.
However, some accidents may occur in the print production process of the newspapers, disrupting the operation plan, such as mechanical failure, expansion of newspapers, and temporary increase in print volume. In order to ensure the stability of production, dynamic scheduling needs to be implemented. For example, when a printing press malfunctions and cannot be produced, it is necessary to transfer the job to other printing presses, rearrange the production, complete the printing production through the extension, and minimize the loss.
V. Evaluation and Improvement of Dispatch Plan
The quality of production scheduling needs to be evaluated. At present, there is no reasonable evaluation program. In general, performance indicators such as equipment utilization, on-time delivery rate, and total delay time should be evaluated. When scheduling production according to a job plan, it is necessary to continuously improve the job plan. On the one hand, there are unreasonable factors in the production operation plan; on the other hand, the type, edition, color, and number of prints of the newspapers are changed every day, and the printing production also changes. In the actual printing production process, the production scheduling plan should be optimized in light of production conditions.
Sixth, expectation
Whether it is a traditional dispatching method or an electronic dispatching method, it is all based on the dispatcher to make a job plan and carry out production scheduling. Its scheduling is based on experience and there is no scientific method. Although the application of ERP software advances the development of print production scheduling, it only provides a tool that cannot automatically schedule job scheduling and is less likely to optimize scheduling. Therefore, it is necessary to further study the scheduling problem of newspaper printing and establish a more scientific, reasonable and effective newspaper printing production scheduling system.
Source: "Printing Magazine"
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