Printer Scheduler Using Digital Window Mover for Duplex Sheet Flow
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Existing printing systems face challenges in efficiently scheduling large volumes of sheets for continuous duplex printing, particularly in maintaining regular output intervals as new print jobs arrive, which can lead to prolonged scheduling times and reduced productivity.
Innovation Solution
The implementation of a digital window mover algorithm within the scheduler, utilizing a directed graph representation, allows for optimized scheduling by providing subsequent windows over the graph to repeatedly find the shortest path between vertices, enabling faster computation and focusing on scheduling only the sheets currently in the printer, thereby enhancing productivity.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a scheduler computes schedules for all sheets in the print queue at full speed, then scheduling completeness is improved, but computation time increases and productivity decreases
Solution Approach 1:
The patent divides the scheduling problem into segments by introducing a window size parameter that limits scheduling computation to only those sheets currently in the printer or expected to enter within the window period. This segmentation allows the scheduler to process a manageable subset of sheets at each interval rather than attempting to schedule the entire print queue, thus maintaining productivity while ensuring reliable scheduling for active sheets.
Solution Approach 2:
The scheduler performs preliminary scheduling actions at regular intervals based on the window size before sheets actually need to be printed. By computing schedules proactively for sheets within the window period in advance, the system prepares scheduling decisions ahead of time, avoiding last-minute computation delays and ensuring smooth continuous printing operations.
2Adaptability or versatility
If the scheduler considers new print jobs joining the queue dynamically, then adaptability is improved, but scheduling complexity and computation time increase
Solution Approach 1:
The patent implements a dynamic scheduling approach where the window size and scheduling intervals can be adjusted based on printer speed, queue conditions, and incoming jobs. The scheduler continuously monitors the print queue and adapts its computation scope to include newly arrived jobs within the current or next window period, allowing the system to handle dynamic job arrivals without requiring complete re-scheduling of the entire queue.
Solution Approach 2:
The scheduler operates periodically at predetermined intervals rather than continuously, checking for new jobs and recomputing schedules only at these intervals based on the current window size. This periodic operation reduces computational complexity by avoiding constant re-evaluation while still maintaining adaptability to new jobs that arrive between intervals.
3Productivity
If the print speed is increased to 300 A4 images per minute, then productivity is improved, but scheduling computation must be extremely fast to maintain regular output intervals
Solution Approach 1:
To support high print speeds of 300 A4 images per minute, the scheduler performs preliminary computations for sheets within the window size before they reach the printer. By pre-computing schedules for sheets that are about to enter or are currently in the printer, the system avoids real-time computation delays that would disrupt the regular output intervals required for high-speed printing.
Solution Approach 2:
The scheduling computation is segmented into smaller intervals corresponding to the window size, which limits the number of sheets processed at each scheduling interval. This segmentation reduces the computational burden per interval, enabling the scheduler to keep up with high print speeds without requiring excessively fast overall computation while maintaining regular output intervals.
Data Source
Figure 1
Figure 2~3
Figure 4
AI summary
The present invention relates to a printing system (1) for cut sheets. The printing system (1) comprises a paper path comprising a loop (32, 33, 34, 35) in order to enable duplex printing on the sheets in a continuous flow of sheets in a first and second interweaving pass in the loop (32, 33, 34, 35). A controller (37) controls simplex and/or duplex printing of image data on the continuous flow of sheets. A print engine is positioned in the loop (32, 33, 34, 35) configured to dispose marking material on the sheets according to the image data. A scheduler (373) time schedules the continuous flow of sheets in an order of a plurality of actions comprising loading a sheet, printing the sheet in a first pass in the loop (32, 33, 34, 35), printing the sheet in a second pass in the loop (32, 33, 34, 35), and unloading the sheet. The scheduler (373) is configured to use a digital representation of a directed graph of vertices and edges, each vertex representing an action of the plurality of actions on a sheet of the continuous flow of sheets and each edge representing an amount of time needed for a sheet to go from a starting vertex of the edge to an ending vertex of the edge. The directed graph also represents interweaving of sheets from a first pass and a second pass. The scheduler (373) comprises a digital window mover for providing subsequent windows over the directed graph. Each window of the subsequent windows covers a finite subset of the vertices of the directed graph which correspond to actions on a number of subsequently sheets to be processed in the continuous flow of sheets, as to allow repetitive executions of an algorithm for finding a shortest path between vertices covered by the window. A window size determines for each window of the subsequent windows the amount of vertices in the window and a window step size determines which vertices are covered by the subsequent windows respectively.