Discussion on practical experience of ink dosage calculation

The author for many years for the major printing plants to install and design ink color system, in the field of ink color, although they dare not identify experts, but dare to admit that the ink color matching system is very professional. However, during the first nine months, when the author installed and designed the ink color matching system for the customer as usual, the customer suddenly asked a confusing question: “How do we calculate the amount of ink to be prepared for actual production? If you use too much, there will often be a large amount of waste ink left after the production, which will both waste the cost and increase the waste ink inventory. If the budget is too small, the employees will have to re-formulate or even stop waiting, which will affect the production schedule."

After listening to the question, the author did not understand the answer. However, after many discussions and trials with customers, we found a calculation method that was fairly accurate and is now discussed with other industry peers.

First of all, we need to know what important factors affect ink usage. Basically, ink usage will be affected by the following factors:

The minimum amount of ink on the printing press

When the ink is put into the printer, not all of it will be transferred to the paper. The ink passes through many different rollers and is dispersed and transferred onto it, and finally printed on paper. So, some of them are not used for printing and they are lost on the press and cover the rollers. In addition, the ink fountain must reserve a certain amount of ink to stabilize the ink supply. Therefore, the ink on the roller and the ink fountain should be calculated within the usage. This amount can be understood as the minimum amount of ink on the press. Pay special attention to different brands and models of presses, the minimum amount of ink will be different. Of course, the greater the number of prints, the least amount of ink on the press will become irrelevant.

Printing area

The spot color area of ​​the print is proportional to the amount of ink. The larger the spot color area, the more ink is used. Therefore, the area of ​​printed spot color will be used to calculate the amount of ink. If the pattern of the printing area is relatively regular, it is of course easy to calculate the area using different mathematical formulae of the mathematics. Otherwise, the following method can be used to calculate:

1) First copy the pattern on copy paper;

2) Then cut out the pattern from copy paper;

3) Put the cut out pattern on the scale to calculate the weight;

4) Cut the blank copy paper into 10cm x 10cm squares;

5) Place a 10cm x 10cm (100cm2) square on the scale to calculate the weight;

6) The pattern area can be calculated by the following formula:

Pattern area cm2=(100x pattern weight)/square weight

Print volume

The number of prints is most directly related to the amount of ink used. The greater the number of prints, the greater the amount of ink used.

Ink loss rate

In the general printing process, some of the ink will be lost on the roller, and some will be lost when the head is used for test printing. In addition, since the ink loss rate can also be used as an error to adjust the ink amount calculation, the operator can also decide whether or not to evaluate it.

Printing ink thickness

The thickness of the printed spot ink does not directly represent the printing density, so it cannot be calculated using a Densitometer. Since the thickness of the ink is relatively thin, it can be calculated by means of an ink qualitative analyzer or an ink-dispensing machine using an indirect method when the thickness cannot be measured with a density meter or a ruler. Using these devices to calculate the thickness of spot color inks, I will discuss with readers in the future.

The thicker the spot color ink, the more ink will be used. Therefore, the printing thickness of the ink must be determined before printing in order to calculate the amount of ink. I also advise the readers here that you should not reduce the thickness of the ink in order to save the amount of ink, because some colors must be printed at a certain thickness, and if the ink is too thick, there will be other printing problems.

Specific gravity

The proportion of ink is the weight of ink per cubic centimeter. This parameter can also be calculated using an ink meter or ink distributor.

Now we can begin to discuss how to calculate the amount of ink. The first thing to know is the basic amount of ink used for each print. Using the print area of ​​the spot color pattern and the thickness of the ink, the amount of ink used in a print can be known, and then the amount of ink used in a print can be calculated by using the specific gravity of the ink and converting the volume to the weight. The reader can also refer to the following formula:

A piece of print ink usage (g) = print area x ink thickness x ink specific gravity

After calculating the amount of ink for a print, you can calculate the amount of ink for the entire print order, and then add the ink loss rate and the minimum amount of ink on the press to calculate the amount of ink used during production.

Production ink usage = one printing ink usage x loss rate x printing quantity + minimum ink usage

The reader can use the above formula to try to calculate the amount of ink used in the printing process and verify that the theory is helpful for production.