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77. DESIGNING FOR MARKING

77.1. REASONS FOR MARKING

The widespread practice of marking products, parts, and materials has many

purposes. They include the following:

1.For production identification. Product and brand names and model names

and numbers are normally included on finished products.

2.For advertising. Trademarks, the manufacturer's name, and model

identification all have advertising value if attractively presented.

3.To indicate grade, size, or class of a material or component.

4.To indicate that an inspection or other manufacturing operation has

been carried out.

5.To indicate the part number in case product repair is later required.

6. For patent protection.

7.To indicate the date of manufacture or the product's serial number.

8.For decoration.

9.To indicate dimensions of components before selective assembly.

10.To provide graduations or other functional marks.

11.To provide instructions on the operation of the product.

12.To display product specifications such as horsepower, voltage, etc.

13.To provide automatic data collection through the use of bar codes or

other readable markings.

77.2. MARKING METHODS

DESIGNING FOR MARKING
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The designer has a wide range of marking methods to choose from. They

include the following.

77.2.1. Freehand Marking

This is a fundamental method of applying visible markings to many kinds of

surfaces, using brush, crayon, chalk, pencil, pen, or a similar hand-impelled

marking device. The marking action always involves the transfer of part of

the marking medium (e.g., ink, stain, paint, pencil graphite, etc.) to the

marked surface.

77.2.2. Printing

Printing, either directly to a workpiece or to a nameplate, label, or tag, is a

common marking method. In industrial marking, it most frequently involves

transferring an image from an inked printing die, usually rubber, onto the

surface being marked. This is calledlexographicor contact printing.

Noncontact printing uses paint or ink applied by means of a spray. This is

commonly referred to as ink-jet marking.

77.2.3. Stenciling

When ink, paint, dye, stain, or other fluid coloring is applied to any surface

through the openings of a marking device so that the shape of the aperture

controls the form of the mark, the method of application is known as

stenciling. The fluid coloring may be applied by brush, spray, roller, or a

similar implement, and the stencil may be prepared from paper, steel, copper,

rubber, plastic, etc. Also, abrasives can be sprayed through a rubber or

plastic stencil to mark materials such as marble, glass, and ceramics.

Silkscreen printing (described in Chap. 6.12) is another stencil method

particularly useful when decorative effects or attractive brand or model

names are marked on a finished product.

77.2.4. Etching and Engraving

These two kinds of marking produce marks on the surface of metal or other

material by removal of part of the material in such manner that the material

remaining forms the desired marking. In the case ofengraving, the material

removed is cut away by sharp or abrasive instruments; in etching, the
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for in this process the workpiece to be marked is struck or pressed against

the dies with such force that the metal or other material flows into conformity

with the dies shape.

Embossing is commonly used for marking metal tags. Individual tags or tags

in continuous coils may be embossed by manually activated or automatic

embossing machines.

77.2.9. Stamping

In this common method of marking, the lettering or other symbols are

impressed into the surface of the workpiece. A hardened die is forced into

the workpiece surface either by a steady press force or by impact. The latter

may be applied manually by a hammer blow, one letter or symbol at a time.Pneumatic, hydraulic, mechanical, or solenoid presses can stamp

combinations of characters in one stroke. Roll-marking devices are also

economical for many applications.

Programmable stampers that generate characters or graphics by indenting

multiple dots or impressions to form a recognizable shape are widely used.

Flexible software enables the stamper to imprint numbers, diagrams, or logos

on a wide variety of substrate materials.

77.2.10. Nameplates, Labels, and Tags

These are often used to provide the same kind of information that would

otherwise be marked directly on the product. All the marking methods noted

above are also applicable to nameplates, labels, and tags, provided the base

material is suitable. A variety of fastening methods are available fornameplates, but threaded fasteners, adhesives, and rivets are used most

commonly.


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Figure 8.6.1. Common methods for product marking. (a) Offset print

marking metal bar stock with rubber type. (Courtesy Pannier

Corporation.)

77.2.11. Decals

The transfer of printed material from plastic film or paper to the product's

surface provides a means for displaying brand names, trademarks, and

decorative material in an attractive manner.

77.2.12. Machine-Readable Identification

This includes markings of several types that can be read by computer-

connected optical scanners and high-resolution video devices. Bar codes or

characters designed specifically to be machine-readable can be used.

Radio-frequency identification (RFID) encompasses a wide range of

applications, notably railroad cars and highway toll plazas where informationcan be read at high vehicular speeds, despite fog, mist, dust, grease, oil,

snow, ice, darkness, walls, and other obstacles. RFID requires separate

tags that are applied to products by various methods.


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Figure 8.6.1 illustrates a number of these marking methods.

77.3. CHARACTERISTICS AND APPLICATIONS

Table 8.6.1 lists some dimensional characteristics and applications of the

common kinds of markings.

77.4. ECONOMICS

Table 8.6.2 summarizes the economic factors attendant on the common

marking methods.

77.5. SUITABLE MATERIALS

Table 8.6.3 summarizes commonly used or advantageous materials for each

listed marking method.

77.6. DESIGN RECOMMENDATIONS

Perhaps the most important question facing the design engineer with respect

to marking is its location on the product. Several considerations are

applicable:
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Figure 8.6.1. (Continued) Common methods for product marking. (b)

Embossing; material remains essentially uniform in thickness. (c)

Coining; material flows into die depressions.

1. The marking location should be accessible to the marking device.

Overhangs and deep and narrow recesses should be avoided.

2. The marking should be visible. Brand identification and trademarks must

be prominent; nameplates and other identifying material should not be

located in an obscure position.

3. When the final marked component or product is bulky, it is usually more

convenient and economical to mark an individual part before assembly.

Other considerations are the following:

1. The surface to be marked should be flat. Cylindrical surfaces are also

satisfactory for stamp indenting and some other methods, but spherical or

irregular surfaces always present a problem. Hand-finished surfaces may be

difficult because of poor flatness.


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Figure 8.6.1. (Continued) Common methods for product marking. (d)

Apparatus for noncontact ink-jet marking of components and

cartons. (Courtesy Pannier Corporation.)

2. When it is desirable to mark without displacing the metal of the workpiece,

the following methods can be employed: acid etching, grit blasting with

stencils, silk screening, and stencil and other printing methods.

3. Surfaces to be used for freehand or stenciled lettering should not be too

small.

4. Decorative designsetched, silk-screened, printed, embossed, or

otherwise applied to an open surfacecan serve to hide surface

imperfections such as nicks, scratches, etc.

5. When two or more areas of different color are incorporated in a silk-

screened, lithographed, or stenciled marking, the designer should allow for

possible mismatch of the colors. If one color is not completely opaque when

overprinting another, a dividing line of 1.2 mm (3/64 in) should be allowed

between the two areas if silk screening is used and 0.8 mm (1/32 in) if

lithography is used. (See Fig. 8.6.2.)

The following design recommendations apply to embossed markings:

1. To avoid an oilcan effect and to simplify tooling, limit the depth of

embossed lettering to one material thickness. The stroke (letter leg width)
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should be at least three times the material thickness. Figure 8.6.3 illustrates

these rules.

2. The angle of bevel of embossed lettering, as also illustrated in Fig. 8.6.3,

should normally be between 35 and 40. For sharpness and clarity of

lettering, the angle

Figure 8.6.1. (Continued) Common methods for product marking. (e)

Marking a casting with programmable stamper that generates a

series of depressed dots. (Courtesy Pannier Corporation.)
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Figure 8.6.1. (Continued) Common methods for product marking. (f)

Methods of stamp-indenting cylincrical parts.

can be held within 25 to 30, but the wider angle provides easier metal flow

and longer die life.

The following design recommendations apply to stamp-indented markings:

1. A number of character styles and faces are available in standard

commercial stamping dies. Figure 8.6.4 illustrates popular lettering styles.

Sharp-faced gothic characters are recommended for best clarity of

impression and easiest operation.

2. Round-faced and interrupted-dot marking dies are advisable if there is a

need to minimize induced stresses in the workpiece. (See Fig. 8.6.5.)

3. Generally speaking, the smallest lettering commensurate with good

legibility should be specified even when ample marking surface is available.

Small characters require less force and more easily produce a clear, well-

defined impression.

4. A series of high-legibility numbering dies has been developed by the Steel

Marking Tool Institute for hand stamping in situations in which part of any

character may not be distinct. This type of numbering is recommended for

miscellaneous handstamping applications. (See Fig. 8.6.6.)

77.7. RECOMMENDED TOLERANCES

Table 8.6.4 presents recommended tolerances for various marking elements

including nameplates. The values shown are for normal, noncritical

applications. When necessary, closer tolerances than those shown can beheld for product appearance or other reasons. If so, however, tooling and

processing costs usually will be increased.
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Table 8.6.1. Characteristics and Applications of Markings Made by

Various Methods

Marking

method

Minimum

recommended

letter height,

mm (in)

Permanent

or easily

removable

Remarks

Typical

applicatio

Freehand 2.5 (0.100) R Appearance

and legibility

poor; limited

information

Raw-materi

grade (colo

code),

various

identificati

tags

Contact

printing

1.5 (0.060) R Multicolors

feasible

Raw-materi

grade,

identificati

labels, tags

nameplates

Noncontact

printing

1.5 (0.060) R High print

quality

Raw

material,

shipping

containers

Stencil 6 (1/4) R Good for

largersized

lettering

Shipping

cartons; wi

abrasive

blasting,

glass, and

ceramics

component

Silk screening 1.5 (0.060) R Good

appearance;

can be

detailed anddecorative

Signs,

instrument

panels, cloc

faces

Etching 1.5 (0.060) P Normal Ruler and


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*1.5 mm recommended for legibility; smaller lettering possible.

depth of

etch, 0.07

0.3 mm

(0.0030.012

in); much

finer work

possible with

photographic

techniques

instrument

graduation

Engraving 2.5 (3/32) P Nameplate

plaques

Cast-in,

molded-in

Sand mold, 4

(0.160) Plastic

or diecast, 1.5

(0.060)*

P May be

raised or

depressed

Automotive

engine bloc

many plasti

and die-cas

products

Branding 1.5 (0.060) P Wooden to

handles

Hot stamping 1.5 (0.60) P Decorativewith metallic

and other

colors

Smallappliances,

cosmetic

containers,

golfballs

Embossing 4.8 (3/16) P Good

appearance

and legibility

Metal

identificati

tags

Programmable

stamper

1.0 (0.04) P Good

resolution

Part markin

of work in

process

Laser marking 1.0 (0.04) P Excellent

legibility on

small parts

Electronic

component


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Table 8.6.2. Economic Factors for Various Marking Methods

Table 8.6.2. Economic Factors for Various Marking Methods

(Continued)

*No additional direct cost if impression tooling is incorporated in a normal punch-press or

screw machine operation; otherwise moderate.

Equipment cost may be high but can be amortized over large quantities of units for a

number of different products.


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Table 8.6.3. Suitable Materials for Various Marking Methods

Tags can be purchased preprinted.

Marking

method

Coating

materials

Base materials

Freehand Ink, paint, dye,

pencil, chalk,

crayon

Any clean surface capable of

being marked with some marking

medium, but nonslippery

nonpolished surfaces best

Contact printing

and noncontact

printing

Inks of various

types

Paper, cardboard, wood,

fiberboard, and other resilient

materials best with metal-type

process; all clean, smooth

surfaces suitable with rubber

type

Rubber stamp Ink Paper, metals, wood, fiberboard,fabric, plastics

Stencil Ink, paint, dye Paper, wood, metal, painted

surfaces, fabric, plastics

Silk screen Ink, paint Painted surfaces, metal, wood,

glass, plastics, paper, fabric

Etching None Glass, ceramics, all metals

Engraving None All machinable materials

Cast-in None All castable materials

Molded-in None All plastics and rubber

Branding None Wood, leather, fiber, plastics,

fiberboard

Hot stamping Special leaf-

pigmented

coatings carried to

Plastics, paper, fiberboard,

leather, wood, hard rubber


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the work by a

plastic film

Embossing None Sheet steel, aluminum, brass,

other formable metals, coated-

vinyl sheet

Coining None Low-carbon steel, aluminum,

brass, other formable metals

Stamp indenting None Steel, brass, aluminum, cast iron

(machined surfaces), stainless

steel

Decals Special paints,

inks, and dies on a

plastic film or

paper carrier

Any smooth-surfaced material

Tags Various materials,

depending on

which process is

used

Paper, cardboard, plastic, sheet

metals

Labels Same as for tags Paper, plastic sheet

Nameplates Same as for tags Various sheet metals, plastics

Programmable

stamper

None All machinable metals

Laser Coating not

required but maybe used to obtain

desired

appearance

Plastics, metals, ceramics


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Figure 8.6.5. Low stress-inducing type for stamp-indented markings.

(Courtesy Pannier Corporation.)

Figure 8.6.6. High-legibility typeface enables each digit to be

identified even if there is only a partial impression. In the upper

piece, the top portion of each number is indistinct, and in the lower

piece, the bottom portion of each number is indistinct. In both cases,

however, all numbers are readable. (Courtesy Pannier Corporation.)

Table 8.6.4. Recommended Tolerances for Product Markings

Lettering height 10%

Lettering stroke 10%

Nameplate size (length and width) Normal tolerance, 0.4 mm (0.015

in)

Closest tolerance, 0.13 mm (0.005

in)


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