The prepress area in digital printing
Digital printing requires a dedicated prepress workflow. This means that the most suitable solutions for data handling and colour management have to be chosen in order to achieve maximum operating efficiency.
Currently, a considerable amount of packaging is already produced using the process. Print shops that have not invested in this technology should do so because of the decreasing print runs and personalised print products demanded. However, when deciding to invest in digital printing, they have to choose processes which are most suitable for their production department.
Consideration must be given to the order structure of packaging and labels which narrows down the choices for production equipment that should integrate as seamlessly as possible into the workflow system and provide the highest print quality. Today, there are electrophotographic digital printing systems, such as those manufactured by HP Indigo and Xeikon; and various inkjet solutions from which to choose.
In general, the expectations of new technology are very high. As packaging has so far been conventionally printed with very good results, the successful integration of new printing technologies depends on providing the users with the same high level of quality. For this reason, additional software and technology is usually required when purchasing a digital printing press. One example is the HP SmartStream concept, which controls the areas of communication for administration and work procedures.
Although printing plates are not necessary in the digital printing process, a prepress department is still essential. However, there are other prepress requirements as is the case with conventional printing like data preparation, proofing and raster image processing (RIP). Instead, tools are required which support the digital printing process, ensure high print quality and fast throughput. Only operating printing units provided with the state-of-the-art technology and offering high resolution is yet not sufficient.
Nevertheless, manual input must be avoided as far as possible by using a high level of automation. For this reason, all printing press manufacturers have, for a long time, been working with relevant partners to offer overall concepts covering all the necessary stages in the workflow. Of course, this also means that software is used for interplay with the printing press to automate the retrieval and checking of data in order to process it into printable output data. A special print server solution for labels and packaging, for example, consists of Color Engine, a PDF-RIP, editing tools and a Step & Repeat tool from Esko.
Graphic data can be uploaded through online portals for customer communication in order to create offers and carry out print planning. The print data must be approved and the production planning must be coordinated through to delivery. However, despite all the many advantages and special requirements of the digital printing market segment, one thing is lacking: time!
Tools for individual requirements
In addition to efficient basic software packages and suites for label or folding boxes, special tools for individual work steps or requirements are also available. In order to use the system effectively it is important to know the exact details of parameters such as: How is production currently being carried out? What additional technology is necessary for this? How is the prepress area equipped and which tools are needed specifically for digital printing?
As suppliers of digital printing solutions provide compilations of tools in suites or product packages, it is not always easy to know which basic tools are included. Therefore, the requirements of print shops should be identified and compiled in clear categories, so that the tools can be assessed and combined in an optimum way.
The most important difference between digital and analogue printing is the fact, that the colour separation for digital printing presses is carried out using RIP’s and colour tables.
The raster image processor
The RIP is the central unit for controlling the digital press as this is where the data for printing is prepared. As digital printing is a direct process, no auxiliary tools, such as films or printing plates, are needed. Nevertheless, very good print results can be achieved, which are close to the ISO and Fogra standards.
With the RIP, it is important to cleanly implement the PDF data and, in particular, correctly convert the colours. All data for special colours is converted into a definitive colour system (usually seven or eight colours) and attention should be paid to which data components are being colour-optimised to enable brilliant reproduction. Is it solids, colour gradients, or half-tone images? For this reason, the RIP unit supplied by the press manufacturer is an essential component of the printing press and the software should be kept strictly up-to-date.
In addition, the colour rendering should be constantly checked and certified if necessary. In addition, there are instruments, such as ColorControl and Color Engine or ink formulations for designer colours which can be used via the Cloud service.
Colour and consistency are important aspects of digital printing processes, particularly because customers will not accept any product quality issues. It should be noted that special colours can only be printed with restrictions (cost-benefit equation) which must be communicated to the customer. In this context it is useful to sidestep conventional printing with the exact colour requirements of the customer. Although special colours in digital printing can be reproduced with a precision of up to 95%, even such slight deviations are not accepted by some European brand manufacturers.
Conventional printing is already established with many customers, which is a main difference to digital printing. This means that the advantages of digital printing must be communicated accordingly. The most effective way of presenting digital printing to customers is to do a job in practice. For this reason, it makes sense to produce proofs on the digital printing press during the initial phase, as only a few proofing systems can be calibrated to digital printed colours in order to output colour-consistent proofs.
Avoid manual adjustments of the print data!
In general, manual adjustments and reworking of data on digital printing jobs should be avoided in order to be able to process the job as quickly as possible with the highest degree of automation. However, to achieve this the relevant tools are necessary which can include standard tools, such as Pit-Stop, Switch or Connect and special portals for data delivery, with these tools already integrated. It is important that they are adjusted to the intended workflow. The aim should be to carry out a simple inspection of the data as well as having the option to convert this automatically to the specific requirements.
If manual reprocessing is necessary for certain orders or certain customers, graphic designers or agencies, it is questionable whether this will fit into the actual digital printing concept. A special solution should be found for this group of customers, as manual work is not really cost effective within this special overall process.
There are tools available which are used for the personalisation and individualisation of print jobs and also for vectorisation, for the simple use of barcodes and for the imposition of flatwork. This extends through to the complete prepress suite. There are now enough editors to process PDF data natively. The use and necessity of these modules should be checked thoroughly and they should only be implemented if necessary.
Automation of the workflow
Small batch sizes, diversity and the personalisation of packaging and labels require tools which contribute to the automation of the job processing and also the fields of approval and communication as far as possible. Using the relevant tools to automate as many of these activities as possible and let the jobs literally flow through the production, is one of the key elements for the successful use of digital printing. However, if the digital printing concept works out, the sheer volume of jobs allows no time for individual preparation.
As a general rule, workflows for conventional printing are not suitable for digital printing. For this reason, an acceptable solution should be planned during the investment phase of a digital press. For example, direct online connections are already common with commercial printing and online print shops. However, to introduce this into the label and package printing field, requires adequate adaptations. Already existing integration into the in-house MIS system or the standard SAP solutions saves the development of additional interfaces in the long term, as well as cost and time.
Integration process for digital printing
Some projects have shown that digital printing is one of the most effective and innovative tools in order to meet today’s market requirements and the short and multi-variant production cycles. Integration should begin on a solid basis, consisting of the press, suitable processing options, a RIP optimised for digital printing, an effective job management system and high-quality automation tools.
In a second step, when producing with the new technology, it can be checked to what extent existing tools can be used or if special solutions must be purchased.
As a general rule, the integration process of new printing processes always requires characterized optimization and adjustment. This is the only way to positively affect the time factor in subsequent production steps in order to adapt to the short production cycles of packaging and label jobs.
This will intensify further due to the shorter print runs, but with digital technology print shops are very well prepared for this. Integrating digital printing into the production workflow should be supported by a project management team. If the future user of the press cannot provide enough experience from the required employees, an external project support team should be used to keep costs and implementation times down and ensure smooth integration and rapid production start-up.
Entering the world of digital printing does not just mean buying a press. It also demands the optimisation of production structures which also includes intelligent adjustment of the prepress tools and the automation of process steps. All this is necessary in order to process digital jobs as efficiently as possible. After implementation, digital printing can complement conventional presses very well.
As well as searching for the most suitable digital press, it is also importantto incorporate the fields of job processing, converting, substrates, colour management and web-based communication with very high levels of automation into the planning phase. These factors essentially support the clean and effective integration of digital printing. In addition, the planning phase should be preceded by an analysis of existing tools. This is the only way to find suitable additional tools and use them cost-effectively.
If this is performed properly, digital printing may very quickly become an important key factor for the success of the company’s success.
This article was first published in Flexo & Gravure Global 4-2015.