Industrial AutomationAutomation IndustrielleIndustrielle Automation Automation of newspaper printing machines: visit at CIEL 2013 April
Offset printing The most common form of printing low and high-volume jobs used today is "offset" - used for everything from flyers to magazines and newspapers. • Intermediate medium between the printing plate and the paper:rubber-coated "blanket" • The blanket is inked by plate roller under low pressure (prevent image from deforming) • Half a revolution later image is printed on sheet or continuous (web) paper under much higher pressure http://www.umax.co.uk/support/binuscan/technotes/nbi03.htm
Offset plates Initially: printing plate coated with a light-sensitive material that protects water-repellent Teflon layer below - this top layer retains water, preventing ink from building up and being printed on the blanket. In areas where the Teflon has been revealed water will not stay on the surface of the plate, but ink will - hence the exposed areas are those that 'print'. The coating of the plate is removed using a photographic process and (typically) a negative copy of the image-setter films. To produce the plate, films are held in place over the coating (usually via a vacuum frame to ensure perfect contact) while areas of the plate are exposed by a high-intensity UV light source. The plate is then chemically processed to expose the Teflon and fix the coating.
Halftones - Dot Shape, Screen Ruling and Screen Angles To give the illusion of a continuous tone image when printed, all images have to be recreated using "halftone" patterns of regularly spaced ink dots, of varying sizes. The size of these dots, measured in a percentage tint, represents the lightness/darkness of each small area of the image. The spacing of the dots is the "screen ruling", normally measured in Lines per Inch (lpi). To "fool" the eye into seeing a continuous tone image, the lines of dots are very close together: typical line screen rulings are 133 lpi for mono (sometimes 120 lpi) or 150 lpi for colour (or higher). Although these general values are valid for "conventional" printing, uncoated stocks and especially newsprint dramatically reduce the line screens used (e.g. 100 lpi mono / 120 lpi colour).
Colour printing bande de papier Papierband web lead Colours are reproduced by combining four inks: (CMYK)Cyan, Magenta, Yellow, blacK A page printed in full colour must therefore pass through four cylinders, in the order CMYK. printing cylinder plate cylinder
Moiré and rastering Overlaying several halftones produces interference patterns, called "moiré". The most effective dot shape in 4-colour printing is elliptical - this allows overlaid colours to be "angled" to minimise interference. The angle between Cyan and Magenta is critical as interference is obvious; Yellow is far less critical as the colour is so light against white paper; Black will give interference effects but is usually only reinforcing dark areas of an image where moiré is obscured. The screen ruling (measured in lines per inch) varies between colours to reduce “rosette” patterns - the four "irrational screening" angles will usually average the output LPI, with black typically the highest ruling, angled at 45º.
Computer-to-Plate In Computer-To-Plate (CTP), there are no films anymore: the plates are directly etched by a powerful laser and treated chemically. The plate precision is in the order of 0.05 mm, so that the different colours blend without visible shadows. The next step will be Computer-to-Cylinder: there will be no more plates, the cylinders will be directly written by a laser (and erased for the next production). However, this technology is not yet mature and the number of copies produced in one run (before rewriting the cylinder) is insufficient for a newspaper production.
Around a cylinder plate rubber cylinder (blanket) ink water homogenizer water faucets ink supply
Two cylinders plate rubber blanket rubber blanket plate
Cylinder arrangements each manufacturer has its preferred cylinder arrangement
Tower and Folder bande draw roller tensionvalue web 25 dN/m turner bar barres de retournement upper H entonnoir tour d'impression folder cylindres lower H 20 dN/m folder roller infed débiteur 12 dN/m plieuse dancer roller trotteuse reelstand bobines
The folder The folder folds one or several webs into bundles ("cahiers"). (picture taken while introducing the paper in the machine)
8 8 16 16 1 1 1 1 12 12 6 6 3 5 3 5 8 8 1 1 Simple and Double production simple production one newspaper per rotation of the cylinder – all plates of a cylinder are different • double production • two newspapers per rotation of the cylinder – the same plates are mounted twice on the cylinder. 14 3 cylinder (flattened) 10 7 14 3 10 7 5 6 5 6 16 1 14 3 12 5 10 7 1 1 1 1 1 1
Web path web colours couleurs des bandes turner bar barres de retournement bars web folder plieuse web width largeur de la bande reelstands, changeurs de bobines
Paper colour and cylinder arrangement Every newspaper is different. The web path is switched after each productionand the paper is thread in by a carrier system.
Web tracks (Chemins de papier) Nearly every production requires a different threading
The transporter The transporter carries the printed newspapers to the expedition. En route, insets (advertising, prefabricated parts) can be inserted.
Drives The cylinders were formerly connected by a shaft (Axe, Welle). Today, the shaft is replaced by an electronic synchronization based on a hard real-time bus, SERCOS. The precision of the drives position is about 0.05 mm, i.e. 2.5 microseconds at 20 m/s web speed.
Section control A section is a number of towers producing into exactly one folder (towers can be assigned to different folders depending on the number of pages).
THE DALLAS MORNING NEWS Key of Symbols L Lower H-Unit Control (AC110) Mounted in Bridge U Upper H-Unit Control (AC110) Mounted in Bridge T Turner Bar Unit Control (AC110) Mounted on Press Section Unit Control (AC110) S Mounted in Cubicle SK Folder (Double) Unit Control (AC110) F Mounted on Press G General Fct Unit Control (AC110) T2 T1 T3 T4 T6 T8 T9 T10 T5 T7 F1 Mounted in Cubicle NK L L L T L U L L T L U S S F L U L U L U G U U U RC Reelstand Coupler (CS31) Sectionbus AF100/1 Sectionbus AF100/2 RS RS RS RS RS RS RS RS RS RS RS R4 R3 R5 R1 R2 R8 R9 R10 R11 R6 R7 ArcNet RC RC Linebus AF100 PM PM Backup PM PM CC CC CC CC CC EP Ethernet Bridge Ethernet Terminal Server DEC Personal Workstation PC Modem Report Report DB Server and Backup DB Server and Printer Printer Workplace Workplace MPS Production Computer 760 Remote RIP Interface to Parascan MPS Inform 710 Diagnosis (Option) Example WIFAG machine U U 1 2 Mounted in Cubicle SK RS Reelstand Control System (WPOS) Mounted on Reelstand PM PressMaster System Mounted in Cubicle PMR CC MPS Control Console (LS) EP Event & Fault Printer PD MPS Prod. Computer Distribution Integrated in Cubicle MRV PD
The console The console allows to: load the machine configuration save the settings adjust the ink and water for each page display the state of the machine display alarms and events support diagnostics save the settings Console = Leitstand, pupitre
Console: adjusting the colour for each lane (screw) a page is divided into lanes, each each controlled by a "screw“ that adjusts the ink and water ("vis d'encrage“Farbschraube) in the console at right, 11 lanes are visible
Console: adjusting the web tension the web tension defines the print quality, it varies as the machine warms up and humidity changes, but shall not lead to paper tear.
Console: Alarms there are some 1000 different alarms, categorized by severity. Alarms must be acknowledged.
Console: On-line help By clicking on ? a help text corresponding to the actual windows is displayed with Acrobat
Control Structure of an H IBS long-distance bus Work controller SERCOS -drive IBS-M Display Local bus BA DIO MCU LBA check controller loop IO IO IO IO IBS-M BA AIO MCU LBA loop IO IO IO IO IBS safety bus functions: local display, local command buttons, supervision of paper tear, color screws, water Turmbus
Networking a printing machine section to production preparation (Ethernet) standby standby bridge LS LS LS PM PM GW GW Pressmasterbus (Ethernet) Section bus C (AF100) V-Sercos V-Sercos V-Sercos Towers IBG IBG IBG V-Sercos Interbus-S 4G IBG IBG IBG IBG Interbus Interbus Interbus H-Sercos KT94 KT94 KT94 KT94 KT94 KT94 H -PLCs KT94 KT94 KT94 KT94 KT94 KT94 KT94 KT94 Service-ARCnet Falz- und AC160 AC160 AC160 Wendeturm- AC160 Tower-ARCnet Turmsteuerung Turmsteuerung Turmsteuerung steuerung Section bus D Section bus B Section bus C Line bus - AF100 Rollen- Sektions- Rollenwechsler- Sektions- KT94 MR93 wechslerkoppler I AC160 koppler A steuerung steuerung Oxydry-Arcnet Interbus-S KT94 Reelstands ODC Auro Oxydry PECOM-ARCnet
Multiple sections MPS MPS Production MPS Control Console LS LS LS PM LS LS LS PM LS LS LS PM LS LS LS PM tower and folder control B E C D Section Control SS2 SS3 SS4 SS5 OP1 Oxydry (washing) reelstand control Reelstands
Speed and hierarchy response time MPS production Messages Ethernet consoles Arcnet section control section control AF100 tower/foldercontrol tower/foldercontrol tower/foldercontrol Interbus-S cylindres SERCOS motors Process variables
WIFAG Based in Bern, worldwide number 3 WIFAG and ABB pioneered the shaftless press, which is standard today.