Flexible press systems offer the most cost-effective production method when total cost of print is considered 

Dieter Finna

In the daily routine business of label printing, unforeseen circumstances frequently disrupt the planned process steps. Often deadline variations or short-term changes mess-up the order sequence or delay the process. A perfectly designed process should be able to adapt quickly to new demands and the prerequisites for such flexibility are created in process management.

One of the central tasks in process management is to analyse the causes of disruptive factors and to find solutions that keep the effects on the planned work procedures to a minimum. Thus the aim is to avoid or minimise time loss or additional effort.

As well as analysing short-term disruptive factors, process management also pursues medium- to longer-term goals. This involves examining market trends and their impact on the product portfolio. To ensure that equipment can be used universally even when market trends change, great importance is attached to high flexibility of press systems in terms of their configurability and retrofitting. This flexibility, as we will see, spawns useful advantages for day-to-day business.

Process analysis reveals differences in efficiency

Today’s narrow web presses offer great operational convenience due to their modular design and high degree of automation. However, a more detailed analysis of the time required for individual workflow steps reveals significant differences in the set-up and changeover times of the various press systems on offer. In routine business, this leads to significant differences in efficiency. These become particularly noticeable when external influencing factors come into play and not everything goes according to plan. Which is why larger label and packaging printers carefully examine the process times of individual workflow steps of the press systems they use and apply their findings to optimise the process sequences.

Practical reference values

Performance data for current press systems in practical operation serve as reference values for the following examples. As basic equipment they have either UV offset or UV flexo printing units which may be supplemented by additional configurations with all other common printing processes. The options for expansion include rotary screen printing, partial solvent gravure printing, hot-foil embossing and cold-foil application, coating and lamination.

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Procedures that process management examines to control external factors, among others:

•             Process changeover times

•             Set-up times for job changes

•             Reproducibility of orders

•             Web transport

•             Web paths

•             Substrate diversity

•             Multi-Web

•             Flying Inprint

•             Digital Hybrid Solutions

Entry into the process analysis

If a company does not have any experience in process management, a pilot project is a good way to get started, in which processes with set-up times are in the foreground; for example the analysis of planned or last-minute order changes. Since their number varies from print shop to print shop, process management determines how often disruptive factors occur and how influential they are. It then identifies ways in which the disruptive factors can be eliminated. Here are a few examples:

Influence of process change times

In the analysis, the structure of a label printing company shows an average of four job changes per shift where a process adjustment is necessary. The pre-determined changeover time for the exchange of a printing unit is 30 minutes. In concrete terms, this means that each unscheduled process change delays subsequent jobs accordingly and deadlines have to be rescheduled in some cases. If process management compares the process change times of equivalent press systems, it will show that a machine system with optimised web run requires only 5 minutes for a process change instead of 30 minutes.

With an average of four process changes per shift, this leads to a time saving of 100 minutes, or allows 20 % more production time per shift. The difference results from the fact that with the second machine system, the web does not have to be separated during the process change. 

If process changes become necessary at short notice in daily routine business, they have virtually no effect on scheduling and machine availability with this press system. The system is therefore much less susceptible to external influences and production is more cost-effective.

Influence of ink or coatings changes

Ink and coatings changes are among the routine activities when changing over to a new job and occur relatively frequently in daily business. When changing from matt to gloss coating, for example, all parts of the inking unit such as the ink chamber, ink pump with hoses and ink reservoir must be replaced or cleaned. Alternatively, and relatively simply, the changeover time of the press could be shortened by changing the entire printing unit. The prerequisite is that the press system allows this without the need to break the web.

To do this, a printing unit is prepared with the new coating outside the running press and swapped in at the end of the job. This takes around 5 minutes, compared to around 15 minutes for cleaning the inking/coating unit during changeover. With the possibility of changing printing units without breaking the web, unscheduled ink/coating changes have hardly any impact on the scheduling of daily business.

In addition, there is the possibility of producing "Flying Inprint". As in the example above, this production method is based on preparing a new printing unit while the press is running and then switching the printing units. This means ...

Selengkapnya terdapat pada Indonesia Print Media Edisi 103 November - Desember 2021