The ink preset compensation curve, is the compensation for the ink key value (position) for a kind of ink with a kind of paper according to the ink coverage of ink zone.
Pre-inking curve - in the job change, if ink rollers of printing units did not wash. The ink film thickness on the roller is correct for the last job. If the next job having a large different of ink coverage when compare with the last job. The ink key preset value would not have an instant effect on the change of ink film thickness. This will affect the no of sheet need to print to make the new ink setting become stable, this effect would be more obvious in Heidelberg press, this due to the ink path design of Heidelberg is longer than the other vendors. The goal of this pre-inking is try to correct this and make sure the ink key preset can be done within 150 sheets impression.
Almost all Japan presses having a feature (forgot the name) that operator would input the CIP/3 data of next job during the production of current job. The console would counter the no. of sheet need to be printed, which enter by the operator. For example, a job need to print 5500 sheets. During the production of this job, if the operator already enter the next job CIP/3 data, at the last 50 sheets of printing of current job. The console would change the ink key value for next job already. Remember that the change of ink key value would not affect the printing immediately, if will effect on the sheet may be 100 sheets later (the no. of sheets is depends on the ink path distance of the press). After change a new set of plate for next job, the new ink key setting would take a short time to reach stable.