Newsletter 158: Cutting Polyester, Welding Electrical Contacts, Marking Rulon

SYNRAD, INC. - http://www.synrad.com
Thursday, March 22, 2007
Issue 158


Cutting Polyester Fabric	Welding Electrical Contacts	Marking Machined Rulon Parts

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.

Cutting Polyester Fabric

Polyester fabric is used extensively in the manufacture of clothing. Many garments, both innerwear and outerwear, are made from 100% polyester or from a blend of other materials, such as cotton. In addition, gloves, jackets, and other cold weather gear often feature a polyester shell or liner that retains heat while wicking moisture away from the body.

This application demonstrates the ease with which complex shapes are cut using a Synrad CO2 laser in conjunction with the appropriate motion control system. For this example, an FH Series marking head was used; however, depending on the size of the finished piece, an XY flatbed cutting table or robot would provide the necessary motion for cutting garment-sized pieces.

The intricate shape of this 37-square inch polyester fabric was cut using 60 watts of power at a speed of 10 in/sec in a cycle time of 9.48 seconds.

Our cutting setup consisted of a Synrad 60 watt laser, FH Series marking head, and our WinMark Pro laser marking software. The marking head was equipped with a 370 mm lens that provides a 540-micron (0.021”) focused spot with a 20 mm (0.788”) depth of focus. The piece in the photo, measuring 155 millimeters (6.1”) square, was created in a CAD program and then imported into WinMark Pro. We set a Power, duty cycle percentage, corresponding to 60 watts and a cut Velocity of 254 millimeters per second (10 inches/second). Using the settings described, we cut out this intricate shape in a cycle time of 9.48 seconds. The cut edges are clean with a very slight amount of melt due to the high polyester content.

Welding Electrical Contacts

Laser welding has several advantages over conventional welding processes including reduced thermal distortion due to very small heat affected zones (HAZ), accurate control of heat input that allows welding close to heat-sensitive parts, and the ability to repeatedly direct the beam precisely to the weld point. In part, these laser welding applications are successful because the typical focused beam diameter of 100 microns (0.004”) localizes HAZ around the weld area to fractions of an inch.

Unlike conventional welding techniques, laser welding is typically performed without adding filler material to the weld. This creates a homogenous junction between the two pieces without introducing foreign material in the form of filler alloys. The downside is that part fit up at the weld interface must ideally be zero to prevent undercutting of the weld joint. In actual practice, a slight gap not exceeding 10% of the thinnest piece or the actual weld depth, whichever is less, is acceptable. In addition, the conventional welding technique of creating initial spot welds at intervals along the joint helps to prevent material separation during the actual weld pass.

A thin steel cover was welded to this electrical contact with 200 watts of power at a speed of
15 inches per minute using 3.9 CFM of argon
shield gas.

For this welding trial, we were asked to fillet weld a 0.15-mm (0.006”) thick steel cover to a much thicker steel substrate to create an electrical contact. Our beam delivery setup consisted of a 63.5 mm (2.5”) positive meniscus lens, which provides a 100-micron (0.004”) spot size with a 1.8 mm (0.07”) depth of focus. Argon shield gas, at a flow rate of 3.9 cubic feet per minute (CFM), was adjusted to flow over the processing area to prevent the molten weld pool from reacting with the surrounding atmosphere. Each weld bead measures 8.25 mm (0.325”) in length and was completed in approximately 1.3 seconds using 200 watts of power at a velocity of 15 inches per minute.

Marking Machined Rulon Parts

Introduced back in 1952, Rulon® is a specially-compounded form of polytetrafluoroethylene (PTFE) that has found widespread use as the wear-resistant material of choice for bearings, bushings, thrust washers, O-rings, and many other molded and machined components. Parts manufactured from Rulon require zero lubrication and can withstand severe temperatures and corrosive chemicals. In fact, the ‘J’ formulation of Rulon offers the lowest coefficient of friction of any reinforced PTFE material.

The goal of this project was to create readable part numbers on machined J-type Rulon piston assemblies using a Synrad sealed CO2 laser and an FH Series marking head. The FH head was fitted with a 125 mm focusing lens that provides a 180-micron (0.007”) spot size with a 3-mm (0.118”) depth of focus across the entire mark field.

This machined Rulon assembly exhibits a
high-contrast engraved mark using 25 watts
of power. Total cycle time for the 18-character
mark is 0.22 seconds.

In WinMark Pro’s Drawing Editor, we created an 18-character, 2-line manufacturing code using the ‘Simple’ stroke font. We set a Text Height of 1.6 mm (0.062”) and added 0.13 mm (0.005”) of Extra Character Spacing. To mark the piston assemblies, we set a Power (duty cycle percentage) corresponding to 25 watts, a Resolution of 600, and a mark Velocity of 254 mm per second (10”/s). At these settings, we created high-contrast engraved marks on the Rulon material at cycle times of 0.22 seconds per part.

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Synrad, Inc.

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Mukilteo, WA 98275

Tel: 1-425-349-3500

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