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Certification in offset printing (PSO)

Certification and standardization in offset printing
in accordance with ISO 12647-2:2013

1. Certification in offset printing (PSO)

The Process Standard Offset Printing (PSO) describes a standardized procedure for the production of printed products. From the prepress stage to the end product. This allows the quality of the production process to be assured from the recording of the print data to the finished end product.

All manufacturing processes are controlled, checked and monitored by suitable test equipment and control methods described by the PSO. This includes measuring instruments with densitometric and spectrophotometric properties, as well as the appropriate test elements, such as a print control strip or a media wedge. In addition, the process standard offset printing (according to ISO 12647-2) specifies reasonable and practicable target values and tolerances for print production in the form of colour coordinates, colour spacing, dot gain and dot gain spread, which must be adhered to in order to pass certification according to ISO 12647-2.

Computer to Plate Check and linear exposure of the process parameter test printing form.

First of all, the measuring instruments available in your company are checked, calibrated if necessary and coordinated with each other. Then the linear exposure of the test print form takes place, i.e. without using a compensation or gradation curve. This is then evaluated using measurement technology.

2. First proof with the
IPM process parameter test printing form on two substrates.

Using the IPM process parameter test printing form, we then determine all spectrophotometric and densitometric variables in the printing process for each printing condition (taking into account the specifications defined in ISO 12647-2:2013), such as

  • Inking series/CIELab solid ink densities
  • Ink fade (oscillator use)
  • Standardize target densities
  • Ink acceptance behaviour
  • Colouring: Density spread
  • Secondary color coordinates (100%RGB)/Tertiary color coordinates (100%CMY)
  • Sliding/duplicating control
  • Tone value increase and tone value increase spread
  • Characterization of the individual printing units
  • Print contrast
  • Screening: Moiré, dot closure, tonal value gradient radial and linear

3. Evaluation (1) of the measurement results
and documentation of the print result.

PrintProcessControl supports us in the evaluation of the measured values and their nominal and visual preparation for process adaptation. With the help of our optionally available process analysis tool the control, monitoring and documentation of all production parameters is almost “child’s play”:

4. Correction of the RIP-LUT’s for both printing substrates and exposure of the printing plates.

The creation of process plans and the procedure for process adaptation are discussed and agreed with the responsible prepress employees.

The process plans and exposure characteristics are created according to the printing process analysis for the respective printing condition. The “brand” of the RIP does not play a role here – you can count on our manufacturer-independent know-how. The prepress employee will of course be integrated into the processes by us and, if necessary, specifically trained on the RIP, so that it will be possible for him to create his own characteristic curves or make corrections to exposure curves!

Subsequently, printing plates with the IPM visual test printing form are output using the new exposure curves. The metrological control should verify the application of the new exposure characteristics.

5. Second press proof with the visual
Test print form to verify the changes from step 4.

The second proof is printed using the IPM Visual test form. This contains both metrological and visual control elements. The expressive images allow an assessment of the screening quality, the printing process quality for various motif types (skin tones, detail, structure, colour assignment high/low, highlights, depths, metal, etc.) and a first visual comparison of the print with a proof or reference print (if available!).

6. Evaluation (2) of the measurement results,
Fine adjustment of the RIPLUT’s, new CTP exposure.

The dry test prints are measured, the measurement results evaluated and evaluated. All metrologically determined parameters are compared with the visual impression under normal light.

The ECI-GrayKeil with its grey balance fields and/or a customer proof or reference print is used for visual evaluation. Deviations and/or similarities between measurement technology and visual impression are discussed. The metrological evaluation is compared with the corresponding exposure curves, taking into account the visual assessment. The resulting RIP corrections are carried out again.

7. Final proof, final discussion, detailed IPM documentation

With the IPM visual test printing form, all parameters relevant for the printing process are measured and compared with the specifications of the process standard offset printing according to ISO-12647. The “final press proof” with the IPM-ECI visual test printing form enables the generation of characterization data and the optional generation of ICC profiles, for example to reliably integrate specific printing conditions (FM, hybrid) into prepress processes (data conversion, image processing, proofing line).

The content used within the module can be created here.

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