Distributed veto algorithm in Production Digital Printing 7/7/2005 1

Transcription

1 Distributed veto algorithm in Production Digital Printing 7/7/2005 1

2 Traditional Print workflow /7/2005 2

3 Offset Printing Basics High Quality. High setup time. Fast print time. Fixed setup cost. Low cost per page (long runs). Process Prepress. Make plates. Mount plates. Adjust. Print. Offline finishing. 7/7/2005 3

4 Manual Finishing Operations In the traditional workflow with run-length of 10K and more, manual operations between printing and finishing are reasonable. At jobs of 10K this will happen a few times a day. 7/7/2005 4

5 Production Digital Printing Provide Offset print quality,, at any job run-length and competitive prices. The key to competitive prices at small quantities No setup charge and no setup time. Automation, automation, automation When printing 100+ jobs per day manual operations are impossible. 7/7/2005 5

6 Modules A high volume digital printing equipment is a modular system with all or some of the following modules: Digital Front End. Print Engines. Paper Feed units. Stacker units. Binders, booklet makers, etc. 7/7/2005 6

7 Examples Two examples of Xerox machines: DocuPrint TM 1050 Continuous printing. Two engines. Transactional. Igen3 Digital Press, cut-sheets. 110ppm. 7/7/2005 7

8 Module description Digital Front End print server Responsible for job management, image processing, color fidelity, etc. Delivers ready to print image separations to laser heads. A customer may have the choice of several vendors. CREO AGFA EFI 7/7/2005 8

9 The print engine Print Engine The actual transfer of image to paper. A machine may have more then one engine. 7/7/2005 9

10 Print Operation Print engine stations: Alignment Transfer Fuser Duplex 7/7/

11 Paper units - Feeder Paper Feed Stores blank paper to be printed. May be in cut-sheets drawers or continues paper rolls. A machine may have multiple units supporting various paper sizes. 7/7/

12 Paper Units - Stacker Holds stacks of printed jobs. 7/7/

13 Paper Units Booklet Maker Trims and stitches individual printed papers into a booklet. 7/7/

14 Paper Units - Binder Binds documents into a booklet with cover. 7/7/

15 The General Case In the general case we may have a printing solution with the following structure: 7/7/

16 Business environment Each module may be manufactured by a different vendor. We may have various vendor options for some of the modules. Technology Intellectual Property is protected can t t do it alone. A module may be adopted from a previous product line and may be of different technology generation. 7/7/

17 Evolutionary process The huge investment needed to develop digital printing equipment dictates evolutionary process. First models sales finance new models. Small incremental improvements from one model to the next in a single product line. Same basic modules in a product line. 7/7/

18 $$$ The Problem $$$ Create a modular system that is produced by multiple companies and multiple design teams which are distributed geographically, with minimum integration effort and only small changes between following models...and make it cheap enough!!! 7/7/

19 Solution Distributed control. Independent modules. Operation of each of the modules is controlled by a local controller with software developed by the local manufacturer. Module controllers communicate by messages. Fixed interface protocols. Modules are connected by low-latency latency industrial grade network (CAN). Print operation and order is controlled by the server. 7/7/

20 The next problem The system is composed of different modules, which may operate at different speeds, and may have been done for a different print equipment. Ex. It is possible to use a feeder of Xerox DocuColor7000 which prints at 70 pages/minute, with the DocuColor6060 which prints at 60pages/minute. The print operation needs to synchronize multiple modules at different nominal speeds with minimal software changes. When we start a print operation of a page, we need to be sure that every one of the modules along the paper path is ready for this operation since once it started it cannot be stopped. 7/7/

21 The Solution Distributed Veto Algorithm Premises Reliable communication. Low latency communication between all modules. Nodes are aware of system configuration: Number of modules. Length of paper path in terms of frames. Location in paper path. Well defined time frame for each paper at each module. We may delay the operation by a full number of frames when impossible to print. 7/7/

22 The algorithm A Scheduler receives the job description and calculates the optimal print sequence and order. For this print configuration, he broadcasts a commitment request to all the modules along the paper path for execution of the next page at frame n. Xerox Corporation US patent /7/

23 Veto Algorithm Modules needs to commit a number of frames in advance, according to their distance from the beginning of the paper path. The REQUEST message is broadcasted with the frame index. Each module commits or rejects the commitment for the requested frame. The broadcast of the reply carries the frame index. If any of the modules did not commit for frame n,, the requested frame is considered skipped and the Scheduler will re-request request it at frame n+1. Once all modules committed, the requested frame is considered active, and is scheduled to be serviced by each of the modules. 7/7/

24 Achievements: Veto Algorithm Simple algorithm. Fast adaptation of modules into a system with minimum software changes. Fast reconfiguration of a system. System prints at maximum rate permitted by all modules. $$$ $$$ Production of short-run run jobs made possible $$$ 7/7/

25 Bibliography Method and apparatus for improved job stream printing in an electronic printer with various finishing function United States Patent ,, Xerox Corporation (Stamford, CT), Inventors: Ortiz; Pedro R. (Webster, NY);Farrell; Michael E. (Fairport, NY);Rasmussen; David L. (Fairport, NY);Austin; John C. (Rochester, NY) Distributed job scheduling with modular components United States Patent , Xerox Corporation (Stamford, CT), Inventors: Matysek; James F. (Fairport, NY) Handbook of Print Media, Helmut Kipphan. 7/7/