CASE STUDIES & TUTORIALS
Case Studies
Author: Krzysztof Kućma | 2017-03-28

Evaluation of the press before purchase

ChromaChecker offers unique auditing process, one that allows expert level evaluation of any output device. The entire process including the print run will take about an hour.  

Modern printing presses are very complex technical machines. The combination of mechanics and electronics results in the development of a technical device which seems to be very easy to use and on the other hand does not always guarantee the required performance. New, multi-unit machines can easily cost one or even several million dollars. Providers with excellent marketing tools easily convince potential investors that it is worth buying their latest product.


Buying a machine should be based on rational assumptions, but sometimes sales are based more on emotion than a studious assessment of the technical capabilities.

Three schemes to buy a new machine:

  1. Based on the portfolio of capabilities currently available, the new machine allows the company to add an additional customers and job volumes that will increase the production capacity of the current plant. If we are sure that this addition will increase customers and volumes, then the company can focus on getting the best possible financial conditions.
  2. Or, the new machine is so much more automated and efficient, that it can produce the same volume of work as two or three existing presses at one third the cost, it may be easily justified to upgrade to a new machine. Personnal salaries make up 90% of the costs for any employer, if it is possible to run the same amount of work with 60% less personnel, this can easily justify the cost for a newer machine.
  3. The new output device will add new capabilities to complement the plants existing offering. Providing new solutions that have not been offered before. New devices which utilize new technologies and new consumables can result in hundreds of hours of research and development in order to get desired results. The more this can be vetted ahead of time, the less time to enter the device into manufacturing. ChromaChecker can be used to accelerate this process to finalize what variables in the new output device will result in sellable manufacturing.

Assuming new technology is always better is wrong - many technologies are created not to improve performance or durability but to make the production of machines more profitable. Legal regulations such as those related to ecology force changes in chemical substances used in the process - which can dramatically change color precision and accuracy results.

Among the many features of output devices - irrespective of technology, very important features are related to color reproduction capabilities including: productivity, resolution/contrast, color precision, and color gamut size.

  1. The ability to achieve the desired gamut - such as the ISO standard or GRACoL - at a given speed per hour/page, at an acceptable resolution which provides profitable productivity. Speed, gamut size and resolution can all be traded up and down sacraficing one for the other. Ideally, you need to understand the trade offs, before you purchase the output device.
  2. Repeatability / Uniformity / Stability of printing within a single sheet - we have the right to expect that the field of 100% cyan on the whole sheet will print similarly - the differences that arise between the top, middle and bottom or left and right will not exceed the permissible values based on your expectations (E-Factor). The audit provides for comparing within page, between page and between job comparisons which will quantify the results to compare to your E-Factor to understand if the device can meet your expectations.

 Gamut analysis and reproducibility are keys to deciding whether a particular machine is worth buying.

 

How to make an assessment?

Everything starts with the buyers expectations - defining the expectations are the first step, and ChromaChecker's E-Factor exercise allows you to quantify your color expectations related to within page uniformity and repeatability, and as long as the audited devices E-Factor is less than or equal to the buyers expectations, expectations will be met, and buyer will be happy.


Dedicated print - test form

Depending on the type of machine, the printing technology, the size of the test form will be different. However, the construction of such a test form will have common characteristics such as the same patch builds (eg 100Y, 50% C or 10% K) appearing multiple times on the printing page. Based on the available space on the page it is possible to have multiple control strips in an extended schema (eg 3x4, 4x4) to gather corresponding information from many locations on the sheet. 

 

Measurement

When working with contemporary printing technology, ISO standards require spectral measurement under controlled conditions of the UV component - the M1 method. Many modern measuring devices offer this method (though not all).

 

Analysis

In the printing industry expecting that 100% of the production will be perfect is unrealistic, so we need to be able to quantify what percent of production can be accepted. The TR016 Tolerance Schema uses Cummulative Relative Frequency (CRF) at the 95% percentile delta E (00). This method treats delta E as a statistical distribution using a method that discards 5% of the worst results and evaluates what error has the remaining 95% of the measurements (ΔE 2000 for the 95th percentile of the samples) This is what we call E-Factor. Thanks to this methodology, no one can blame the method for evaluating random errors, and it is not as deceptive as the classical mathematical average.

Analyzing the precision (repeatability, uniformity) assesses how the device prints to itself, both within page and between pages and between jobs. The analysis calculates all possible combinations of like color builds and reports the precison usng CRF at the 95% delta E (E-Factor).

Accuracy analysis - ability to color match to the standard ICC profile / or characterization such as FOGRA 51 or GRACoL. Here all the measurements refer to how our printing refers to our reference.

In practice it is necessary to stabilize the output by the operator, eg print 1000 sheets, selecting to evaluate randomized sheets. If we place a simple target on each sheet, for example, 9 locations (up-center-down / left-right), we can calculate the CRF at the 95% (E-Factor). We will know how uniformly the output prints within each sheet but also between sheets. The use of a hand-held measurement device (ie. X-Rite eXact Scan, Techkon SpectroDens or Konica Minolta FD-9, and even i1Pro2) allows us to measure the values. 

 

Reporting/Interpreting

The ChromaChecker ™ software allows you to process measurements loaded on the Cloud in seconds. All important stages of audit analysis are done immediately - the only thing left is correctly interpreting the results. The rule is simple - we expect the error calculated for any parameter (E-Factor) to be below the tolerance threshold (E-Factor) we set. Because reporting is instantaneous - once the measurements of the first page have been loaded, the operator is direted to correct.

The method used in ChromaChecker ™ software has been recognized by two leading American organizations involved in printing: Idealliance and PIA (Printing Industries of America). Also, the scientists of the School of Media Sciences (the College of Imaging Arts and Sciences, Rochester Institute of Technology) and many of the world's most eminent industry experts have provided input in the development of ChromaChecker Color cloud solution.


The first time this process is used can produce an array of results, but the information from the analysis can greatly improve communication with the output device supplier. As a rule, the next attempt will either show a significant improvement in the outcome, or a clear statement that the device will not meet the color expectations. Sometimes it may help to change the configuration of the output device, retrofitting with additional capabilities not included in the original output device. It is worth to take such a test in order to be convinced that the decision is supported by technical analysis, and not by the impression that the print looks nice. Analysis of this type can also be conducted during production allowing a company to continually assess the output device over time. This provides an incredibly precise analysis of the quality of production.

  

Practical example (case study)

Expectations:

  1. Customer wants to buy a two million dollar UV LED offset press for printing premium packaging 
  2. Press will be dedicated to print on cardboard metalized cardboard, PVC films: opaque and translucent
  3. Customers defined desired E-Factor to 3. For this evaluation, we had used hard copy and on line version E-Factor exercise, and Spot Color Exercise 

Test conditions:

  1. Test form:




    For this purpose 6 TVI-6 control strips were measured:



    TVI- 6 control strip contains substrate, solid primaries and secondaries, 10, 20, 40, 60, 80 and 90% tints of primaries.

  2. Instrumentation: for measurements X-Rite eXact Scan + Alwan Print Verifier has been used.
    Page was printed and 6 sheets were measured x 6 control strips = 26 measurements files 
  3. First  printed substrate: cardboard (no OBAs)
  4. Aims: ISO Coated v.2 (SCCA on)

Results:

 

Part 1: Accuracy to Target (ISO Coated v.2):

and Gamut:

 

The customer refused Press due to poor results - this combination of substate and UV LED Ink doesn't bring expected gamut! Print run assessment failed to meet customers expectations!

Densities were not optimal - but even with the optimal results, the end result is not acceptable.

 

Part 2 - Variation analysis - press precision.

 

The results were very poor! The 630 pairs were analyzed and values have a very high E-Factor - up to 6 ∆E00 for 95% percentile (75% black). For solid Cyan= 3.42 for 100 CMY overprint = 5.36

The customer refused to purchase this press, and committed to use this process to assess the next press that they are interested in.