43.4 MARKING

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43.4.1 Laser Marking

General problems with other methods are,

- mark permanence

- poor quality

By contrast, contact ink printing,

- is efficient, inexpensive, and quality is high when ink adheres

- not well suited to many new plastics because of ink bonding problems

Laser marking is generally,

- permanent

- high contrast

- user friendly

- fast

A laser is used to melt or evaporate surface material to create visible difference on the marked surface.

Two methods are commonly used,

scan - much like a television, the laser is vectored about the workpiece to create a complicated pattern.

micromachining - has a beam that is passed through a mask, then through a lens to focus, and finally to the work surface where the mark is burned.

Typical laser types used are,

Nd:YAG

TEA

CO2

Marked areas with micromachining can be up to 1 cm2, or more with the scan method.

Good applications,

- date coders/part numbers/customer info

- frequent setups

- mark permanency

In volume the laser system cost become lower per unit than ink.

Advantages over ink are,

- no downtime to change inks

- elimination of many quality problems found in inks (e.g., ink permanency)

- elimination of special printing plates, etc.

Typical setup time is 5-15 minutes for ink, but 1 minute for laser.