At the recent Fespa Expo in Munich, process control was part of the Fespa Colour LAB and was included in the tour of feature. This seemed to be a new concept to many visitors. This blog with give a little more detail as to where it fits into a colour managed system and workflows.
In this instance, process control as term is used to refer to the printed product validation and verification, rather than the wider meaning within the quality assurance area, when using standards such as ISO 9001.
Image Credit: FESPA
See the blogs on Club Fespa from Paul Lindström……….
So, your colour managed workflow is complete:
So now how do you know if your digital presses are producing to the specified standard? This is where process control is used. It validates printed sheets to the chosen standard or colour specification using a custom colour bar/control strip and a spectrophotometer with process control software.
There are many software solutions available including PressSIGN from Bodoni (now owned by Agfa, their version is called PressTune and there is also a version for digital print called PrintTune). ColorCert from X-Rite, PrintSpec from MellowColor, PressView from MeasureColor, EFI Fiery Color Verifier, Techkon’s SpectroConnect and on-press/in-line systems for digital and offset litho presses.
These solutions can use small colour bars which suit work where there is little room for a large colour bar.
So, what is needed in the digital wide format printing sector to enable process control?
For large format work, often a Fogra Media Wedge, see above, can be used and measured using the same process as used for validating proofs.
However often there is a need for smaller colour bars, such as the small PressSIGN bar or one of the Fogra bars shown below.
The objective of process control is to validate and prove that the printed product is accurate and consistence to the intended printing condition/specification throughout the print run.
The number of sheets/products sampled and measured will be based on the run length, clients may set this figure, some print certification schemes, such as the UK’s BPIF Colour Quality Scheme mandate the number of sheets measured in relation to the run length.
Often for very short runs, say up to 10 copies, only one measurement of one copy may be needed. For longer runs a sampled will need to be assessed in relation the stability of the process and client needs.
The sheets with be measured either by inline spectrophotometers which are on some wide format inkjet devices, or off-line using a handheld spectrophotometer and process control software.
Even this more manual approach only takes a minute or two.
These systems take the intended printing condition, which can be an ISO standard or the chosen simulation ICC profile. They measure the colour bar and report the accuracy in De.
The measurements usually cover: