The art of Process Control pt 3- Day to Day Operation
Once the verification process is complete and all of your profile and curves are in use, you need to keep track of your press and printing conditions on a day to day basis. No printer can afford to run fingerprint runs constantly. Most printers will only fingerprint once or twice per year.
Keeping track of conditions on each press run is important and can be accomplished with a simple target- a color bar.
There are many different types of targets that can be used in a color bar, below is a list of the most common, and what they are used for.
- Solids and Screens- The solid ink blocks are used for measuring overall ink density. The screened patches are for measuring dot gain. Density and gain should not change much from press run to press run- provided they are on the same papers. You must adjust density and gain targets for different papers.
- Gray Patches- these patches are made up of Cyan Magenta and Yellow, and are used for checking the 3c gray balance.
- Trap/Overprint Patches- these patches measure the solid overprints needed to make red green and blue.
- Slur/Impression Targets- these targets are used to measure dot slur (also called coubling). They can also be used to check impression pressure. The more filled in the center of the target is, the more doubling or impression pressure there is. These can be helpful in diagnosing mechanical problems on a press.
Below is what each type of target looks like: