Heatset Offset

Lithography

Heatset Web Offset

Heatset offset is very versatile printing method both from

product and paper point of view

• Products

• magazines, catalogues, direct mail, newspapers, inserts, brochures, illustrated books and manuals

• Papers

• WFC, MWC, LWC, MFC, SC, UWF, newsprint

• Grammages from 35 � ~150 gsm

Heatset printing has global market of ~80 billion €

Paper consumption over 8 million tons of paper in Western

Europe (2008)

Reality check

Global advertising is down ~10% and in magazines ~18%

Deliveries of coated mechanical reels were down ~20% in 2009

compared to 2008

Low operating rates are reflected on prices, which are also going down

Customers are shifting to lower qualities and lower grammages

• How to maintain printed quality?

Paper manufacturers are turning every stone to cut cost in paper

manufacturing

• Runnability issues will increase

Basic design of heatset press

Web widths: ~50 - 280 cm

Web speed: ~4 - 15 m/s

Web tension: ~600 - 800 N/m

Drying (web temp): ~110 - 140 °C

Folding: usually on-line

reelstand

infeed

printing unitsdryer

chill rolls

siliconization unit

folder

Press layouts

Majority of presses (>80%) are long grain

Benefits of long grain

• more variety in folding

• last fold in grain direction in A4 production

• important for perfect binding

Benefits of short grain

• ribbon folder � higher productivity

• page flexibility (height of page)

Heatset presses - different designs

Additional units

• extra colours

• varnishing

Twin webs

• productivity

• versatility

Sheet cutter

• for heavier grammages

• for off-line varnishing

On-line finishing

• direct mail

additional colour

varnishing unit (offset varnish)

Twin web

Heatset web offset printing unit

Blanket to blanket nip

Ink system

• high number of rollers to ensure thin and even ink layer

• 3-4 ink form rollers to ensure even ink transfer to plate

Fountain system

• 3-4 rollers

• water form roller in contact with ink rollers and plate• ensures fast emulsification

KBA Compacta

618

Courtesy of KBA

ink duct

Heatset dryer

Web delay in the dryer is ~1 s dryer length is determined by the press speed (10 m/s � 10 m)

Dryer has multiple modulesHot air from the nozzles carries the web through the dryer

Exhaust air is either circulated back or is let to atmosphere through treatment

(e.g. afterburner)

Together with solvent also moisture is evaporatedcoated grades: ~4-5% � 1-2%uncoated grades: ~5-8% � 2-3%

~240°C~200°C

~150°C

~120-140°C

Chill rolls and Siliconization

Chill rolls

• Thermoplastic ink binder is in

soft form after the dryer

• chill rolls cools down the web and solidifies the binder (better rub

resistance)

• Steel cylinders (3 - 6) with cold

water pumped through

• Web tension has to be high

enough to ensure good contact

Siliconization

• Usually one roller rotating

in pan

• to protect printed area from smearing

• also functions as a

remoistening device

Folders

Courtesy of KBA

Usually former folders

• former fold followed by 1-2 jaw folds

With high pagination the use of ribbon folding is increasing

• web is slitted into ribbons (typical in gravure)

• also choice for short-grain presses

Folding: 16-page, long-grain

Former

fold

Jaw foldChopper/

jaw fold

630 mm

880 mm