Newsletter 129: Marking Square Rings, Cutting TPO, Marking Chrome-Plated Steel

SYNRAD, INC. - http://www.synrad.com
Thursday, January 19, 2006
Issue 129


Marking Square Rings	Cutting TPO	Marking Chrome-Plated Steel

SYNRAD's sealed CO₂ lasers are used in a variety of industrial processes including cutting, welding, drilling, and marking. This news brief showcases some of the interesting materials and products that are processed daily by Synrad's line of CO2 lasers and marking heads.

Marking Square Rings

Square rings and rectangular rings, derivatives of the common O-ring, are used primarily in static and radial sealing applications. Square ring seals are also used as high-pressure gaskets because they out perform circular cross-section gaskets. Although square rings are manufactured on precision grinders and lathes to achieve tight-tolerance I.D. and O.D. dimensions, they begin life as extruded cylinders and so offer a more cost effective solution than precision molded O-rings.

This application involves marking a 6 mm (0.236”) long contrasting band on the O.D. of the ring seal, which measures 1.9 mm (0.075”) wide. The test setup consisted of an FH Series marking head driven by our WinMark Pro laser marking software. The FH head was equipped with a 125 mm focusing lens that provides a 180-micron (0.007”) spot size and a 3 mm (0.118”) depth of focus.

The ring seal above provided a contrasting mark
using a Synrad laser and FH Series marking head.

In WinMark Pro, we created a 6 mm by 1.9 mm rectangle and set the Polyline Fill Type to Fill. On the Format tab, we set a mark Velocity of 45 inches per second, a Power value corresponding to 25 watts, and a Resolution of 400. The square ring, composed of a thermoplastic material, provided high-contrast marks in a cycle time of only 0.34 seconds per part.

Cutting TPO (Thermoplastic Olefin)

Thermoplastic Elastomer Polyolefin, TPO for short, is another plastics polymer that has recently taken hold in the automotive industry as both plastics manufacturers and end-users fine tune formulation and molding processes. TPO is easily thermoformed (which lowers unit cost) and is designed to be readily recycled at the end of its product life. Another advantage is that TPO does not contain plasticizers (unlike many other thermoplastics), which means that parts retain the same degree of flexibility regardless of temperature. In addition to the automotive industry where TPO is used to create fenders, bumpers, running boards, splashguards, and instrument panel skins; TPO also shows up in applications as diverse as imitation-slate roofing tiles, ATV body parts, and shells for ski boots.

This automotive part exhibits cleanly cut edges
after trimming operations using 400 watts of power
at a cut velocity of 150 inches per minute.

For this TPO automotive component, the task was to trim edges and openings in the part at a minimum rate of 2.2 meters per minute (86 inches/minute). The laser setup for our applications test consisted of a Firestar f400 laser with beam delivery through a set of XY flying optics into a cutting head. The cutting head holds a 101.6 mm (4”) focusing lens with a 150 micron (0.006”) focused spot and a 4.3 mm (0.17”) depth of focus. Nitrogen assist gas at 2.4 bar (35 PSI) is delivered coaxially with the beam, which serves to protect the lens and blow vaporized debris through the cut kerf. The thermoformed TPO, having a consistent thickness of 3.2 mm (0.125”), was cut using 400 watts of power at a cut speed of 3.8 meters per minute (150 inches/minute)—a speed increase of 56% over the original requirement.

Marking Chrome-Plated Steel

In previous editions, we have demonstrated the use of specialized coatings to enhance CO2 laser marking of certain materials. These products provide the ability to obtain low power (25–40 watt), high-contrast, permanent marks on materials that are normally reflective to the CO₂ wavelength including copper, brass, chrome, and silver. In addition to brushed or sprayed coatings, several manufacturers have incorporated their coatings into label tape technology. For each part, a labeler advances the tape, holds it in contact with the part surface during laser marking, and then peels up the tape on a rewind spool leaving only a permanently bonded laser mark on the part.

The accompanying photo provides an example of this type of mark. The part, a chrome plated 7/8” deep socket, exhibits a high contrast mark that indicates the size of the socket. For this application we selected a Firestar v40 laser along with an FH Series Index marking head.

Using specialized coatings laser marks can
be obtained on a wide variety of materials that
are traditional reflective to the CO₂ wavelength.

Using WinMark Pro to develop the mark file, we first created a text object and gave it the Text Caption “7/8”. On the Format tab, we selected “TrueType” for Font Type and chose a TrueType font installed in the marking computer’s Fonts folder. We set Text Height to 0.2” and Text Curve Detail to 600. On the Marking tab, we set Velocity to 10 inches per second (IPS), Power to a duty cycle percentage corresponding to 40 watts, and Resolution to 600. The three-character mark was completed in 1.81 seconds and is permanently bonded to the plated socket.

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