flexo Ink Consumption: Calculator vs reality

Last week, I corresponded with a fellow flexographer about the complexities of calculating ink consumption. He noted that different calculators produced varying results, which led me to explain that accurately predicting ink consumption for a given image and anilox volume is difficult. In fact, it’s more like “voodoo”. That’s why my approach combines using a calculator with tracking and analyzing actual consumption data over time. Let me expand on that here.

The Variables:  Where Ink Consumption Gets Tricky
In theory, the key variables are straightforward: anilox volume, ink transfer percentage, image area, and the number of impressions. But let’s take a closer look at the real-world complications.

Anilox Volume:
Dan Reilly’s research, published by the Flexo Quality Consortium in the December 2011 issue of FLEXO magazine, illustrates how tricky volume measurement can be. If I recall correctly, the study found six different ways to measure anilox volume, with varying degrees of accuracy—and different results. Even for the same roller, manufacturers may report different volumes due to differences in measurement techniques.

Metering with Doctor Blades:
We’d like to believe that doctor blades precisely meter ink at the surface of an anilox roller. But anilox surfaces are rough at a microscopic level, with channels between cells and inevitable wear over time. Blades rarely meter perfectly, and operators often over-press them against the roller, causing ink to hydroplane under the blade. This can result in more ink getting past the blade than expected.

Ink Properties:
Viscosity, temperature, base type (water, UV, solvent), and surface tension.

Anilox Surface:
Roughness, condition, and surface energy.

Operational Factors
Ink spills, run length, residual ink losses (pans, hoses, and chambers), and shelf life—all of which affect costs.

In short, we are trying to control fine parameters within a complex, unpredictable environment. It doesn’t take much for actual consumption to deviate significantly—sometimes double or half the predicted amount.

A Practical Approach to Ink Prediction
So, what can we do? Start with the output from a calculator that aligns with your process, but don’t stop there. Track the actual ink consumed for each job’s plate over time. Use this historical data to develop a correction factor that you can apply to your calculator’s predictions for future jobs. This process isn’t easy—but it’s the best way to achieve more reliable estimates.

After all, as I often say, "Flexo. It's not rocket science... it's harder!"

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