Lithographic Printing Process

The printing process is typically divided into three work steps: prepress, press, and postpress. Each is described below:

Prepress

Prepress includes all the operations necessary to prepare a job for the printing process. This step has undergone tremendous change in the past 20 years. Up to the 1980’s (i.e., before the personal computers), prepress relied on film and photosensitive materials to create the image on a plate. This is referred to as analog workflow. Today prepress workflow largely relies on electronic processes (digital workflow) that eliminate the need for film altogether – along with all the chemicals needed to process the photographic images.

The process focus here is on preflighting, trapping and imposition to start the workflow. In digital workflow, the image is transferred directly from computer to plate. In analog workflow, there are imagesetting, film assembly, analog proofing and analog platemaking work steps.

Any phase of print production must be mindful of the work steps that follow (i.e., system approach to management). For this reason, it is critical that prepress personnel communicate with pressroom personnel on a number of issues. For example, which press will this job be printed on? Each of the major printing processes uses different image carriers, inks and press configurations. As a result, some of the prepress steps vary from process to process. Specific considerations must be taken into account when preparing copy and art for printing. The job is now ready for the press.

Press

Even though there have been many advances in the press process, the underlying principles remain basically the same. A press operator must have a working knowledge of the basic operations of a pres, such as dampening, inking feeding, as well as the characteristics of paper or other substrates being printed.

Today, many aspects of press operation are computer-controlled. The basic processes of presswork are as follows: pre-makeready, make-ready, pressrun and clean-up. Pre-makeready involves examining a job’s specifications and gathering, inspecting and delivering all necessary materials to the press area to run the job. This is considered to be a supporting process to the pressrun. Make-ready is precisely what the name implies – making the press ready to print. It involves a number of steps including inking the press, mounting printing plates, loading paper, registering the images, and achieving proper ink levels. A goal for most print businesses is the minimization of make-ready since it is time-consuming and quite wasteful. Make-ready supports the pressrun as well. Once make-ready is complete, the print job goes through the pressrun. This is where the customer’s job is actually printed. The total number of good, usable copies from a single printing is also referred to as a pressrun. The final stage is clean-up. Ink must be cleaned from printing plates, rollers, and cylinders. The work area needs to be cleaned to be ready for the next press round. This stage is a supporting process of the pressrun.

Postpress

The final phase of print production is called postpress and included finishing and binding operations as well as packaging and distribution. Postpress operations can account for 25 to 50 percent of a job’s value.

A bindery is the area where binding and finishing operations are performed. Some local printers outsource their bindery operations to businesses better suited for this work. Binding operations are those that secure together multiple-page products. Finishing encompasses a number of processes that complete graphic arts production, such as cutting, folding, and the addition of special graphic enhancements.

 

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