Volume 37, Issue 4, April 2002
X Marks the Spot
Considering the Use of Product Identification Marks
by Mark Stillman
These are just a few of the glass-marking systems available to the industry.
Almost all companies mark their products. In many cases, the marks are for decorative
or aesthetic reasons. But decorative marking is only half the story: marking is also used
for identification purposes. Glass is one of the oldest materials manufactured that is
identified with marks.
Glass trademarking dates back to the second century when glass vessel makers applied their signature to a piece. It is this application of trademarks that gave birth to a new industry known as identification marking. There are four basic reasons to mark a product: primary identification; traceability; compliance; and operations.
Primary identification is the most basic of communications. From the beginning, trademarks were used to identify the craftsman or manufacturer. Today, virtually all products show a company name or trademark. Other examples of primary identification are part numbers and sizes. In these cases, the quality of the mark is as important to the manufacturer as the mark itself. The mark is seen as a communication about the product, product quality and as a reflection of the company.
Traceability is used to identify differences in like products. This can be used for internal or external reasons. An example of an internal reason would be to determine which plant or machine made a product. An external reason might be for shelf-life reasons such as expiration codes. Batch codes and machine codes help to monitor quality control. This type of coding is most recognized in the food and pharmaceutical industries.
A mark that is applied as a condition to sell or distribute the product is known as compliance marking. This requirement usually originates externally such as government or vendor specifications. Sometimes these marks seem involuntary especially when marking requirements are very specific in regard to placement and technology. However, they are essential for maintaining industry or distribution
The last category of marking is operational marking: voluntary marking that streamlines and improves the manufacturing process. For example, orientation or location marks may assist workers in the assembly of the product. Inspection codes can help to track a product internally through the manufacturing process. Bar codes combined with readers assist in automation, as well as improved quality and efficiency. Color identification allows personnel to distinguish like parts, and color recognition systems can automate sorting and tracking processes as well.
How to Mark a Product
The advantages and disadvantages of marking technologies are determined by their effects on the material or substrate. Applying a mark on material requires changing the finish. This is done in one of three ways: molding/indenting or displacing the surface; removing or etching the surface; and adding ink to the surface.
Due to the fragility of glass, indenting is not a marking method usually associated with the glass industry. It is, however, one of the most commonly used methods outside the glass industry. In the case of molded products, most molds are indented or engraved with primary identification such as trademarks, part numbers and patent numbers. In the case of insulating glass, spacers are often indented because the mark can be stamped into the aluminum as part of a cut-off process, or roll-marked into the strips as they are extruded. Indented and molded marks are the most permanent marking methods because the marking cannot be altered without destroying the product. Indenting can be as simple as the methods described above or more sophisticated using a computer-controlled carbide stylus to indent marks one dot at a time. This type of indenting process is often used for traceability marking because it applies variable information easily.
ScriptMark, shown here, is another
option available for marking products.
Etching involves removing a small portion of the substrate's surface in a set pattern to make a permanent mark. Technologies used to accomplish etching include acid etching, airgrit or stencil blasting and laser. Acid is effective for decorating and marking large areas, but not practical for coding and production marking. Airgrit is a process which uses a rubber mask or stencil, through which an aluminum oxide grit is blasted under high air pressure. Airgrit differs from sandblasting in that the grit is controlled and re-circulated back into an enclosed hopper. This process is used widely in tempering plants, laminating operations and at window manufacturing plants. Machines can be a simple bench top style or fitted into a cutting table before washing. Used to put trademark, specifications and monthly date codes in a small area, the process is inexpensive, fast and easy-to-operate.
Laser is the newest etching technology being used. With the development of a scanning laser, applications have now expanded to trademarking as well as traceability codes. Laser's biggest advantage is that it is a non-contact method. A high-energy beam of light removes a shallow layer of substrate. Most lasers now on the market are computer-controlled. Initial costs of installation and training are much higher than other technologies but there are few consumable or operation costs.
When printing a mark, ink is being added to the substrate. With the application of ink, such printing introduces new considerations including color and adhesion. Color is used to emphasize or make a mark more visible to the end user. Conversely, some inks are made to appear invisible except when subjected to certain conditions such as ultraviolet light or moisture. Because a printed mark is being applied to the surface, adhesion is often an issue.
When mark permanence is desired, it is important to determine to what substances the end product will be exposed. If it is meant to be temporary, considerations should be made to when and how the mark will be removed. Many of these characteristics are controlled by the selection of ink. Inks are usually designed in conjunction for specific application technology.
Contact Printing vs. Ink-Jet Printing
The first distinction is whether the print will be contact or non-contact. Contact technologies include silk screen, offset, direct, pad transfer and reciprocating. Non-contact printing technologies (also known as ink-jet) include continuous ink-jet, impulse and drop on demand. In all cases, ink-jet characters are formed by generating a series of dots. There is also the advantage of being non-contact which allows the printing of uneven surfaces. The characters are composed of a dot matrix design created from a single head, so the printing requires the movement of the marking head or the substrate. Ink-jet is well suited for printing one or two lines of text on a moving product. Ink-jet technologies vary by print resolution, throw distance and line speed.
Common reasons to choose a contact method over ink jet are print resolution, wider selection of inks and colors and the ability to change colors in the same printer. Contact printing technologies are used for identification and decorating as they are both suited for multicolor printing. Offset, direct and reciprocating printing technologies are one-color processes and commonly used for identification. The offset and direct printers are designed to mark in-line on either the top or bottom of the product. These units are used commonly on continuous extrusion and web lines.
Offset and direct printers are commonly used on float lines. These printers will take a wide variety of inks including frit-type inks that will become permanent after tempering. The marking will consist normally of several lines of text that includes names, trademarks, sizes, specifications and monthly date codes.
Reciprocal printers were designed originally for package identification but now are being used heavily for traceability and operational codes. They can mark either a moving or stationary mark with either single- or multiple-line text and are well-suited for color code changes as most use a cartridge-type ink supply. Because of their size, simplicity and low cost they are integrated easily into most production facilities.
Mark Stillman serves as market director for Matthews International Corp., based in Pittsburgh.
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