Quality control during final print run

• visual checks form an improtant part of quality control process
• but accurate testing can be carried ou only with use of sensors & electronic equiptment
• carrie dout on printed control ***** incorporated on the waste areas of the printed sheet

• paper reacts to changes in the environment eg (temp & humidity) which may cause problems during a print runs
• paper is kept in relative huidity of the print room for it to adapt
• during print regular checks are done to ensure quality

1) set off - ink from one sheet smudges on to underside of other

QUALITY CONTROL - use of sufficient anti-set spray or qucik drying inks or better quality paper stock

2) colour variation - where printer doesnt maintain consitent colour throughout the run

QUALITY CONTROL - use of colour bars & regular densitometer readings

3) hickies - small areas of unwanted solid colour surrounded by an unprinted 'halo' area caused by specks of dirt/paper/debris/ink skin on printing plate or blanket cylinder

QUALITY CONTROL - useregular washing of the clanket cylinder

4) bad register - where colours protude beyond the edge of the four colour separations making the image look out of focus

QUALITY CONTROL - use regular inspection of registration marks to line up the four colour separations exactly