Standardizing Workflows

In this article, we will delve into the world of PRX and PQX and explore how they contribute to shaping the modern flexographic printing process. We’ll start with a description of the standards themselves, discuss why they were created, and show how they can help streamline communication between print buyers and printers.

 

 

 

 

 

 

 

 

 

Figure 1: Lack of standardization creates a complex situation for brand owners and printers. 
All illustrations courtesy of ColorConsulting USA INC

This article is not intended to make the reader an expert in PRX and PQX. The information provided here is a condensed version of the entire specification intended to identify the information that can be included in PRX and PQX documents. The true intention of this article is to promote knowledge of these protocols, with the expectation that this will help expand their use across all phases of the print production process.

Let’s start with a breakdown of what makes up these specifications.

With a PRX and PQX capable workflow, each printer only needs to support one format for quality specifications, and one format for quality reporting. This greatly reduces the amount of manual communication and reduces the opportunities for human error in both directions.

PRX

PRX is an Extensible Markup Language (XML)-based protocol that provides a standardized mechanism for the one-way transmission of print quality requirements from the brand owner to the printer and other key stakeholders in the production process. The use of a standard protocol significantly improves both efficiency and accuracy.

PRX is not designed for ordering print jobs, but rather to establish a buyer’s policy for expected quality.

 

What's in PRX?

The PRX specification defines several sections to be included in a PRX document. The use of the word document here does not imply that PRX must be contained within a file. In XML parlance, any complete instance of an XML schema is often referred to as a document, regardless of the form the instance takes.
There is a plethora of information contained in a PRX document, and outlining all of it is beyond the scope of this article.

The most relevant sections of the PRX document include: 

• QualitySpecification—this section contains the meat of the PRX. It includes the detailed requirements, broken down into four areas:
  - Color Measurement   
  - Color-to-Color Registration 
  - Inspection (Defect Detection) 
  - Barcode Quality 

• This section will contain links into the CxFReferenceData and SampliingPositionImageData described below. 

• This section also contains the ink specification for the product, identifying any coatings required, minimum values for colorfastness and resistance to specific materials, and any materials that are prohibited in the printing process.

• EvaluationInfo – this section describes the grading policy to be used to judge the acceptability of the printed material. It allows some complex grading systems to be encoded in a standard format. It also allows the definition of a minimum acceptable grade.

• CxFReferenceData – this section consists of a complete CxF document containing the color targets for any colors (process or spot) to be measured within the product. The CxF document is embedded in the PRX document in its entirety.

• SamplingPositionImageData – this optional section can be used to provide links to images to be included in the specification. These images can be used to identify measurement positions on the sample, or areas of the sample requiring special inspection or measurement. Refer to the quality goals discussion below for more details.

While PRX, PQX, and CxF each address different aspects of the printing process—streamlining print requirements exchange, print quality assurance, and color management, respectively—they can be seamlessly integrated to create a holistic and highly efficient flexographic print workflow.

PQX

Like PRX, PQX is an XML-based protocol, but it provides a standardized mechanism for the one-way transmission of print quality results from the printer to the brand owner. As is the case with PRX, standardization improves both efficiency and accuracy.

PQX is designed to provide raw quality data, with no judgment as to acceptability. As we’ll see later, acceptability can only be determined by combining the requirements outlined in PRX with the quality data provided in PQX.

 

 

 

 

 

Figure 2: Use of PRX and PQX greatly simplifies communication for brand owners and printers.

 

What’s in PQX?

The PQX specification defines several sections to be included in a PQX document.
The most relevant sections of the PQX document include:

• CustomerItemCollection – information regarding the item or items printed in the associated job. This data must map to the item descriptions provided in the PRX document if this data is to be evaluated against the corresponding PRX.

• SampleCollection – entries for each sample that was taken during the printrun. If there are many samples taken during the run, samples can be averaged over time, and the averaging method can be specified for each sample. The information in the sample collection is broken down into the same four categories described in the PRX QualitySpecification element.

• Color measurements will contain a link to the CxF object in the CxFSampleData section corresponding to the measurement and may contain links into the CxFReferenceData described below.

• Each attribute of reported quality may contain information regarding the position of the measurement or defect on the printed form. Inspection, barcode, and register reports may also include links to images associated with the given measurement or evaluation.

• CxFReferenceData – optional and would most likely be used if the color target information was not supplied by a PRX document. Including the reference information allows analysis of the color results even if the PRX document is not available.

• CxFSampleData – a complete CxF document containing the color measurements taken during the print run.

• InkCollection – this optional section can be used to provide information about the specific inks used to print the job. Note that the specifics related to the ink requirements in the PRX are not included here. Unlike the quality specifications, which have targets and tolerances, the ink requirements are hard and fast rules that must be adhered to. In that sense, there is no “pass/fail” associated with the inks.

 

Problems solved?

In the past, print quality requirements were supplied in various ways by each brand owner, often using nothing more formal than a specifically formatted requirements document. This presents a few challenges for the printer.

Brand owners would each have their own requirements format, and the printer would have to keep track of these documents (and any associated changes) throughout the printing process. If the printer attempted to automate quality control, it would need to translate these requirements documents into a format that can be interpreted by quality control systems. Automating this translation process is almost impossible.

Just as each brand owner might have its own format for specifying requirements, they can also each have their own format for the reporting of quality metrics. One brand owner may expect a specifically formatted quality report, while another requires raw data, again in a proprietary format, so that they can generate their own internal reports. Yet another brand owner may partner with a specific vendor to collect data and generate the necessary reports. This can mean that the printer needs to support a specific reporting format for each of its customers. (See Figure 1).

Although it may seem that this problem affects mainly printers, the complications caused by this situation lead to added work and potential human error, the cost of which is inevitably passed back to the brand owners in the form of higher production costs.

 

The solution

Problems described previously were first highlighted during meetings with the Brand Owner Council (BOC) in 2014. The BOC is a membership of brand owners who meet to discuss best practices and identify areas in need of standardization or process improvement. The BOC requested the creation of standard protocols for specifying print requirements and the reporting of print quality.

To address these concerns, IDEAlliance formed the PQX Working Group in 2015, and development of the standards began. In 2017 the decision was made to make these international standards, and the Working Group became part of ISO TC130 WG2. After numerous revisions, the PQX standard was published as ISO 20616-2 in 2019, and a minor revision was published in 2020. The PRX standard was published as ISO 20616-1 in 2021.

With a PRX and PQX capable workflow, each printer only needs to support one format for quality specifications, and one format for quality reporting. This greatly reduces the amount of manual communication and reduces the opportunities for human error in both directions. (See Figure 2).

It should be noted that while the two standards are very closely related, they are completely independent. It is possible to use PRX to publish print quality requirements even if PQX is not being used to report print quality results, and vice versa. However, the greatest efficiency gains can be achieved when the protocols are used in tandem.

While PRX, PQX, and CxF each address different aspects of the printing process—streamlining print requirements exchange, print quality assurance, and color management, respectively—they can be seamlessly integrated to create a holistic and highly efficient flexographic print workflow.

 

PRX, PQX & CXF

While PRX, PQX, and CxF each address different aspects of the printing process—streamlining print requirements exchange, print quality assurance, and color management, respectively—they can be seamlessly integrated to create a holistic and highly efficient flexographic print workflow.
Here’s how these technologies can work together:

1. PRX-Assisted Setup: PRX technology streamlines the exchange of print requirements, reducing manual communication and ensuring accurate and up-to-date job specifications. During the setup phase, information from the PRX document can be used to populate the printer’s quality management systems, reducing setup times and costly mistakes.

2. Real-Time Quality Management: As the press runs, PQX allows the monitoring of print quality and color consistency in real-time. Any deviations from the established standards can trigger adjustments to press settings, guided by PQX data.

3. Data Exchange for Quality Control: PQX facilitates the exchange of print quality data between different stakeholders, including brand owners, printers, and prepress operations. This data can include CxF color data, allowing all parties to ensure that the desired colors are maintained.

4. Cost and Waste Reduction: The combined use of PRX, PQX, and CxF results in efficient print requirements exchange, reduced setup times, and fewer rejected prints. This leads to significant cost savings and a reduction in material waste. These savings benefit the printer and brand owner alike.

5. Brand Consistency: The integration of these technologies helps maintain brand consistency across various printing jobs, substrates, and printing devices, ensuring that the final products accurately represent the brand’s image.

By integrating PRX, PQX, and CxF into the flexographic print workflow, printers can streamline their operations, reduce costs, and provide consistent, high-quality prints that meet the exacting standards of today’s market.

 

Adopt & refine

The printing community continues to adopt new standards for the efficient and accurate sharing of data up and down the workflow. As we have seen with other standards like PDF and CxF, the PRX and PQX standards are likely to undergo iterative refinement as they are adopted in more and more workflows. 

Hopefully, this article has armed the reader with enough knowledge about these standards to investigate how they can be used to the benefit of all stakeholders involved.

Whether you are a brand owner, a print supplier, or a workflow or quality management tool supplier, discuss these standards with your partners and learn how they intend to help you adopt them moving forward.

ABOUT THE AUTHOR: Michael Sisco is a software engineer and color scientist with nearly 30 years of experience in the printing industry. He is a graduate of the University of Wisconsin–Madison with a Bachelor of Science in Electrical and Computer Engineering. Michael has participated in several industry standards organizations, most recently the working group that developed the PQX and PRX quality specification and reporting standards.

He is currently the director of software development and technical sales manager for ColorConsulting USA, a consulting service which works with stakeholders at all levels of the print supply chain to drive efficiencies and ensure the highest levels of print quality.

Additional information regarding PRX and PQX can be found here.