Finishing

Finishing refers to all the activities that are performed on printed material after printing. This includes binding, the fastening of individual sheets together, anddecorative processes such as die-stamping, embossing or laminating.

Finishing can be:

• an in-line process – which means that units attached to the end of the printing press perform the finishing operations. This is typically the case with web presses as well as many digital presses.
• an off-line process – which means that printing and finishing are completely separate processes.

The overview below list major finishing processes.

Bindery processes

Cutting and trimming

Paper stock may be need to be cut or trimmed more than once during the production of a job:

• Sometimes the paper that is in stock is too big and needs to be trimmed prior to printing a job.
• When multiple signatures are combined on one press sheet, those sheets need to be cut after printing.
• Sheets may need to be trimmed to fit folding machines or other bindery equipment.
• After folding and binding the unbound sides need to be trimmed. For books this is often done with a three-knife cutter, which has three blades to simultaneously trim three sides.

Cutting and trimming is usually done using a guillotine cutter. A stack of sheets is placed on the bed of the cutter and the angled stainless steel blade cuts through it at the desired position. All the stacks are subsequently often placed in a jogger, a vibrating table that squares the stacks of sheets.

Folding

For magazines, books,… large press sheets need to be folded into signatures. This involves a series of  right-angle folds in which the sheet is folded multiple times. Folding a sheet once makes four pages, two right-angle folds make eight pages,…

Other types of work require parallel folds in which two or more folds which are oriented in the same direction are made  in a sheet. This is typically done for leaflets or brochures. Some common types of folds are:

• the half fold
• the accordion fold
• the gatefold
• the French fold
• the letter fold

There are two common types of folding machines: the knife folder, also known as a right-angle folder, and the buckle folder. In general knife folders are used for heavier stocks, while buckle folders are used for lighter paper types.

Collating and gathering

These processes involve placing (folded) sheets in the correct sequence. Collating refers to sorting individual sheets into sets. Many laser printers and copiers have a collating function. Gathering is a similar process but it involves folded signatures. Gathering machines have up to thirty slots or pockets in which signatures are fed manually or automatically. The machine then gathers the signatures into what is known as a book block. Such machines can also have a binding function, such as for instance a stitcher.

Binding

There are different ways of binding sheets together. Below are the most commonly used techniques:

• Perfect binding: Pages are fixed to a cover or spine using glue. This process is used for paperback books, magazines, telephone guides,…
• Saddle-stitching: Pages are bound by driving staples through the center of the spine of folded sheets. This wire binding technique is commonly used for magazines, newsletters, small catalogs,… but is limited in the number of pages that can be bound.
• Side-stitching: This type of wire binding is less common than saddle-stitching. The staples are driven through the pages, usually parallel to the bind margin. Reports are often bound this way.
• Thread sewing: A thread or cord is used to stitch a book block together. This is often done in conjunction with using an adhesive. Thread sewing is used for hardcover books. Afterwards the book cover is attached using a technique called case binding. As with wire binding, there are two types of thread sewing: saddle-sewing and side-sewing.
• Comb binding: The teeth of a plastic ‘comb’ are inserted into a series of slits drilled or punched into a stack of sheets. This process is often used for reports and presentations.
• Spiral binding: A continuous wire or plastic coil is threaded through holes drilled or punched into a stack of sheets. Spiral binding is typically used for notebooks.
• Loose-leaf binding: A set of holes is drilled in a stack of sheets which are then inserted into standard or customized ring binders or post binders. This binding technique is used for notebooks, presentations, financial reports, manuals or any other type of publication that require frequent updating.
• Padding: the binding of a stack of sheets are bound using a flexible adhesive so that the sheets can easily be removed. Notepad are a typical example of padding.

Decorative processes

Embossing and debossing

Embossing is the process of adding a relief image to a book cover or other printed material. Sometimes an ink or foil is used to accent the relief image. When the stamped image is left as is, this is called blind embossing. Debossing is the opposite, creating a sunken image on the substrate.

Foil stamping

Foils can be a real eyecatcher when applied to book or magazines covers. This is especially true for metalic foils which reflect light and add a silvery or golden glow. Such foils are applied using a pattern on a heated die that presses a roll of foil against the substrate. Adding the foil can be combined with embossing in a process called foil embossing.

Coating

There are different types of coatings that can be applied to printed matter. Some are water-based and take time to dry, others such as ultraviolet coatings dry when exposed to light or heat. The different types of coatings include:

• Varnishes protect and also have a decorative purpose. Depending on the effect that needs to be achieved these can be high-gloss or matte coatings. Sometimes a varnish isn’t applied to the entire surface but only used to make certain pictures, logos or text columns stand out. This is called a spot varnish.
• Primers are used to improve the ink reception or to facilitate the application of another type of coating.
• For packaging barrier coatings improve the resistance to oxygen, water or chemicals.

Laminating

Laminating refers to bonding a separate material or layer of material to the printed matter. The most common type of laminating is sealing the print between two layers of a plastic material. A typical example of this are menu cards for restaurants which often need to be both sturdy and water-proof.

Edge staining

The edges of the pages of a book or catalog are sometimes colored to mark different sections. This is called edge staining. Gilding is a special case of edge staining in which gold leaf is applied to the edges of a book.

Converting

Converting refers to all of the finishing operations which transform a printed piece into another physical form. This includes bagmaking and boxmaking but more general processes such as bookbinding, waxing, coating, laminating, folding, gluing or die-cutting are also considered converting operations.

Other finishing operations

Die cutting

Irregularly shaped printed matter such as coasters or labels are cut out of the substrate in a process called diecutting. The die contains knives or creasing rules that have been prepared specifically for a certain shape.

Glueing

Products like envelopes, stamps or labels need to have a moistenable adhesive applied.

IndexingIndexing refers to adding plastic index tabs or index thumb cuts to the edges of printed sheets.

Source: http://www.prepressure.com/finishing