Print inspection: How to check quality and content of digital print ?

02.06.2022

Why is it crucial to perform a Print inspection of printed material? Simple answer: It provides peace of mind on the content and quality of the printed product. Furthermore, it catches defects early and avoids waste of paper, ink and time. Digital print inspection can be a daunting and complex task. Let’s have a look at some fundamentals:

What is a Digital Print Inspection?

Print inspection can mean different things to different people, and the primary focus of the inspection can be highly application dependent. The inspection needs of a PoD book printer are probably different from a printer of transactional documents.

However, there are some common basic controls that are relevant in many inspection applications:

  • Registration errors
  • Colour inconsistencies
  • Accuracy and definition (regarding images)
  • Ink coverage

Performing these checks inline during production can save a lot of pain and materials.

Traditional Approaches to Inspection

There are several ways in which print inspection can be carried out. The most common one involves using what is known as a “golden template”. An inspection template is set up from a Golden Image taken with the inspection system. Numerous features can be highlighted within this template. This template is then used for comparison with running production.

The inspection system detects differences between image-elements of the original template and the currently running production. Any difference indicates an error.

The WI8 Web Inspection System

With our WI8 inspection system, we aim to provide users with an all-in-one approach. Various metrics will be examined utilizing a master template. These include for example the printed content, Data Matrix codes, and the condition of the printing nozzles or jets.

Users can also customize settings in order to analyse other variables. These include (but are not limited to):

  • Contours
  • Colours
  • Smearing
  • Positional elements (such as borders)

Customized settings will provide a greater degree of automation. Furthermore, all information can be used in synergy with the Hunkeler Control Platform (HCP). Production throughput is monitored across multiple checkpoints, streamlining communications between different interfaces.

Note that this web inspection system offers a host of supplemental features when required. These options include:

  • Record and replay capabilities
  • The verification of postal codes
  • Printer-oriented graphic controls
  • Full-page image verification
  • User-oriented graphic controls (these are discussed a little later)

To learn more about these options, please get in touch with a Hunkeler representative.

The Use of a Contact Image Sensor

The system offered by Hunkeler utilizes what is known as a Contact Image Sensor (CIS). These sensors are close relatives to the type commonly found within flatbed printers and scanners, and they provide real-time monitoring capabilities.

The key advantage of the CIS is its very compact packaging size. This allows a very tight and elegant integration into existing equipment like printers or finishing modules.

A Look at Intelligent Print Inspection

This recent advancement has already begun to take the printing community by storm. Intelligent Print Inspection (IPI) offers numerous advantages that would not have been possible with more traditional methods (like “golden sample”).

Intelligent Print Inspection provides a more comprehensive approach. Primarily, the template is no longer fixed to a golden sample. Instead, it comprises raw print data (sent from the printer’s controller) to generate an inspection template on-the-fly. What is the main benefit of this technique?

Since no predefined golden sample is required, IPI is able to inspect every unique page in, for example, transactional- or publishing print.

It is also worth mentioning that IPI offers several additional possibilities:

  • In transactional print, it can detect defects without prior knowledge of the printed text
  • It is possible to discover a single defect within a large project. Examples can include a photo book or a series of complex images.
  • A reduction in operator interaction, increasing overall efficiency.

IPI is part of the WI8 set of inspection tools. Currently, the Canon ColorStream series of printers is supported, and other printers will follow shortly.

Advanced Web Inspection for Digital Printing Needs: Cutting-Edge Solutions

These are just some ways in which operators can guarantee continuous quality improvement and increase the productivity of their production lines. The WI8 system is scalable, modular, and capable of working in conjunction with the Hunkeler Control Platform. Therefore, throughput and accuracy are ensured.

Ensuring the production of high-quality printed content is essential in this day and age. This is the motivation behind the development of the proprietary approaches mentioned above. From advanced print inspection to real-time tracking and error reporting, little is left to chance.

Of course, you might have additional questions about Web inspection for digital print. If you wish to learn more, please take a moment to contact one of our sales representatives. As always, the team at Hunkeler will be more than happy to help.