Cleaning Applications in the Printing Industry

White Paper

Introduction

The term “printing” encompasses a wide range of processes used to produce tangible reproductions of text and/or images from a design template. These processes vary widely in complexity, and are used to produce anywhere from one to millions (or more) of copies of finished items, including documents, books, newspapers, magazines, finished goods, apparel, packaging, signs, banners, and other promotional items. In all cases, however, a printing process utilizes some method of transferring a medium, often a type of ink, onto a substrate surface, the most common being some type of paper.

In 2007, it was estimated that the annual worldwide print-on-paper volume was over 45 trillion pages. 1

As with most production activities, printing includes a need for maintenance and cleaning tasks in support of the process. This white paper discusses cleaning applications associated with the printing industry,  considerations in selecting a cleaning product for these applications, and and some of the health and safety concerns that go with them.

Printing Technologies

The principles behind printing technologies have been around for a long time. The technological advances come in not the printing concepts, but in the equipment, media, and methods used to implement them.

All printing processes accomplish the transfer a design from a master source to the production item. To accomplish this, the process must allow for the medium to be applied to certain areas, while preventing it from being applied to others, to create the finished image. The areas where the medium must be applied are called, simply enough, “image areas” or “printing areas”. The areas where the medium should not be applied are similarly called, “non-image” or “non-printing areas”. Printing technologies are the equipment, tools and procedures, used to automate the process of getting the media onto the image areas, while keeping it off of the non-image areas.

Conventional Printing Technologies

There are four primary printing technologies in use today. Conventional methods involve the use of a physical template of the image, usually called a plate, which makes the transfer of medium to surface.

Wikipedia offers an excellent overview and detailed discussion of these conventional printing technologies, but to summarize:

1. Planographics

Both image and non-image areas are transferred from the same level (plane), with the distinction between them being preserved chemically or physically. Printing areas are medium-receptive, non-printing areas are medium repellent. Examples include:
• Offset Lithography

2. Relief

Image areas are are on the plane, appearing raised, and non-image areas are below the surface of the plane, appearing flat. Examples include:
• Flexography
• Letterpress

3. Intaglio

Non-image areas are on the plane, and the images areas are etched or engraved on a level below the surface of the plane. Examples include:
•Gravure

4. Porous

Image areas are on mesh screens, which permit the medium to flow through via capillary action. Non-image areas are stenciled over the screen to block the medium from being applied to those areas. Examples include:
•Screen Printing

Digital Printing Technologies

Digital printing has become a major factor in the industry, making high quality printing available in virtually every home or business. While digital printing has become the standard for low-volume printing, conventional methods remain significantly less expensive at higher quantities.

Digital printing is characterized by the ability to transfer images directly from an electronic computer file to a finished product, without the need for physical plates.  While digital printing methods are technologically very different from conventional processes, the principles are largely the same, and all rely on specialized electronic equipment. Again, Wikipedia offers useful details on digital printing. To summarize:

1. Heat Transfer

Uses the precise application of heat to react with special paper and render an image. Heat Transfer can be thought of as being much like planographics.

2. Impact

Primarily used to print text documents, impact printers are essentially high-speed, automatic typewriters. Impact printers operate on the same principles as relief printing.

3. Electronic Transfer

Involves the use of a laser or other electronic means to attract toner to the substrate in the pattern(s) necessary to create the image. Conceptually akin to intaglio printing.

4. Inkjet

Inks are sprayed onto the surface in the pattern(s) necessary to create the image. Similar in concept to porous printing, with the “stencil” being defined by the ink spray pattern in the digital file.

Cleaning Applications

The cleaning applications associated with the printing processes are largely the same, regardless of the print method being used. These include:

On-Press (in-place) Cleaning

On-Press, or in-place, applications involve the removal of ink and other soils from substrate surfaces,  without any disassembly or parts breakdown. In some cases, this in-place cleaning is an intermediary process during the production run, or it may be a function of simple efficiency or necessity. Some examples of On-Press cleaning include blanket and roller washing and surface wipe down. In some cases, automated systems are used to accomplish the On-Press cleaning. The compatibility of the cleaning products with the substrate materials is often a significant concern in the applications.

On-Press Cleaning is generally mission-critical and time-sensitive, having a direct impact on the  quality of the finished product and overall efficiency of the production operation.

Tools & Off Press (maintenance / rebuild) Parts Cleaning

Tools and disassembled press parts are removed and cleaned Off Press, often in some form of parts cleaning equipment. Examples include squeegees and scrapers, ink trays, spray bars, anilox rollers, and hand tools. Except for the soil, Off Press cleaning in the printing industry is virtually identical to maintenance and rebuild cleaning in general industry applications.  The compatibility of the cleaning products with the substrate materials is often a significant concern in the applications.

Off-Press Cleaning is also generally essential to product quality and production efficiency, but is often an after-production task and not as time-sensitive as On-Press Cleaning.

Press Frames & Exteriors

Cleaning of press frames and press exteriors is largely a detail and appearance application. It usually involves hand wiping surfaces, either with a spray bottle of product or a cleaning bucket. Cost is generally the greatest factor in cleaning product selection.

These cleaning tasks are generally not critical to production operations, and have more to do with safety and the culture of the shop. They also serve a preventive maintenance function, allowing for easier access and better visual inspection.

Facility & Janitorial Cleaning
(floors, walls, and workspaces)

Facility and janitorial cleaning tasks are often overlooked as a component of cleaning in the printing industry. The inks and other soils used in a printing operation typically find their way onto most surfaces in the facility, and can be even more challenging to remove from floors and other building surfaces than they are from presses and parts.

Janitorial cleaners are typically selected based on price alone, and are often viewed as not being a part of the press / production cleanup process.

Product Considerations

Despite what product manufacturers may claim, there is no cut-and-dried criteria that will determine in advance how effective a particular product will be in a given application. There are a number of factors to consider – of which the product chemistry is only one –  in selecting a product for use in printing applications. And ultimately, only a practical qualification of the entire cleaning process will determine how effectively a product performs.

Things to consider and evaluate when selecting a products for use in printing applications include:

Soil

In most printing applications, the soil being removed is ink. There is, however, a wide variation in inks and how they are applied that significantly impacts how they are cleaned. In order to make an educated decision about what products should be evaluated for specific inks, it is helpful to know:

• The ink’s base material, technically referred to as a vehicle, such as soy oil, water, etc.
• Drying method, such as absorption, UV curing, precipitation, etc.
• The printing process (web litho, flexo, gravure, etc.)
• Substrate materials used in the process, both those of the print surface, and associated tools and equipment.

As with any industrial environment, it is also not unusual to have a need to remove common soils such as lubricants and grime in printing applications.

Information on Mirachem’s Printing & Ink Cleaners can be found online at b.mirachem.com/1MT6XvM.

Item / Material Compatibility

It is important to consider the impact that chemicals can have on substrate materials. This includes both the item being cleaned, often called the “widget”, and the tools, equipment, and surfaces used in the cleaning process. In general, it is not usually difficult to find cleaning chemistries that will perform in a given application. The challenge often comes in finding a product that both performs well and is compatible with the items and surfaces exposed to the chemical.

In printing applications, material compatibility concerns often center on:

• Corrosion of metals, like aluminum and carbon steel, used in tools and equipment
• Damage to plastics or fibers, often the substrate materials in items being cleaned
• Unwanted removal of certain substances, such as glues, finishes, or emulsions
• Damage to, or deformation of, equipment components, such as screens, rollers, blankets, or paper trains
• Compatibility with automated cleaning systems

Method / Equipment / Process

Product selection is greatly influenced by the workflow of the  application, including the cleaning method, parts cleaners or other equipment, and the steps in the process. Also important is to evaluate if the best option is to determine the product to use in an existing process, versus re-defining the process around a product.

It is a common error when evaluating product chemistries to simply compare individual features and benefits.  Cleaning products cannot be satisfactorily evaluated for a given application without taking the entire workflow into account.

Cost

The management of cost is an inescapable part of any product evaluation. Historically, cleaning products sold into the printing industry have been high cost items, with the price being driven by both direct engineering and product development costs, and a pervasive market perception that less expensive products would not perform in printing  applications.

When evaluating cost in cleaning product selection, it is important to evaluate not only the purchase cost of the product, but also the actual costs of use, including:

• Cost at actual use dilution
• Labor cost increase / decrease based on product efficiency
• Costs and/or savings from equipment automation
• Compliance costs associated with environmental risks, worker hazards, and waste disposal

Environmental, Health, & Safety Concerns

Printing industry cleaning applications must be viewed with an eye toward environmental, health, and safety considerations. In addition to the challenges posed in these areas by the print processes and the materials used in those processes, the chemicals used in cleanup must also be considered.

Worker Safety

Worker safety remains a fundamental concern in any workplace, and is growing in importance. Worldwide focus is being brought to the issue and employers are being held increasingly accountable for the safety of their employees. A good example of this trend is the US’s adoption of the HazCom2012 standard.

Historically, the printing industry has been considered an environment where exposure to fumes, corrosives, and toxic materials, was unavoidable. Consequently, little attention was given to the safety attributes of cleaning products in the facility. As this thinking evolves, it will be increasingly important to evaluate cleaning chemistries for factors such as:

• Corrosivity (usually a function of product pH)
• Toxicity (particular concern in the area of long-term organ damage)
• Exposure risks (such as skin irritation or breathing issues)

Fire & Explosion

Fire and explosion are a significant area of concern for printing operations. Volatile chemicals, like isopropyl alcohol and hydrocarbon solvents, are common in the industry, and otherwise minor mishaps can cause serious injury or damage.

Where possible, the workflow for cleaning applications should be designed such that selected cleaning products do not introduce additional fire or explosion risks into the production facility. Features to look for include:

• Non-Combustible
• Non-Flammable
• Non-Fuming

Air Quality

Another area of growing concern, environmental issues like air quality continue to be a priority for printing operations. Having enjoyed the benefit of many regulatory exemptions in the early days of air quality legislation, more recent years have seen printers feel the full force of more aggressive enforcement. These government mandates have brought increased compliance and oversight costs to the industry, and in many cases, impacted productivity as long-used cleaning chemistries were banned in many applications.

To combat this, printers must look for alternatives outside of the traditional product offering. Newer cleaning technologies, including those not specifically marketed to printers, must be evaluated to improve environmental compliance. Features to look for include:

• Low- or No-VOC (Volatile Organic Compounds)
• ODC-free (Ozone Depleting Compounds)
• No HAP (Hazardous Air Pollutant), or VOHAP (Volatile Organic HAP)