Newsletter 114: Cutting Polycarbonate, Marking Electronics, Cutting Sandpaper

SYNRAD, INC. - http://www.synrad.com
Thursday, June 9, 2005
Issue 114


Cutting Polycarbonate Filter Media	Marking PBT Electrical Connectors	Cutting Silicon Carbide Sandpaper

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 Polycarbonate Filter Media

Polycarbonate membrane filters are used to trap extremely small particulates for further analysis by scientists or medical researchers using light microscopy (LM), or more typically, electron microscopy (EM) or scanning electron microscopy (SEM). Polycarbonate filters, specifically, polycarbonate track-etch (PCTE) membrane filters are precision micro-porous screens. These filters contain uniform, cylindrical pores that are etched into the membrane material, providing an even distribution of trapped samples on the flat, smooth surface. The polycarbonate substrate is strong, biologically inert, resistant to chemicals, and thermally stable.

The 31 mm x 21 mm samples were cut using
10 watts of power at a cut velocity of 50 inches per second. Cycle time to cut each individual piece was 0.15 seconds. The cut edges are clean with no discoloration.

For this application, sheets of 2-mil polycarbonate media were cut into smaller rectangular shapes to fit the filtering device. Because the material is so thin, gas assist is not necessary and the material is easily laser cut on an XY table or with a marking head. We choose a 10-watt sealed CO₂ laser mated to an FH Series marking head and fitted with a 125 mm focusing lens. Using WinMark Pro’s intuitive interface, we quickly created and sized the desired shape with four-digit accuracy.

Marking PBT Electrical Connectors

Polybutylene Terephthalate (PBT) is one of the most significant thermoplastic polyesters engineered in the past 35 years. PBT exhibits a great surface finish, is dimensional stable, and has excellent electrical insulation characteristics. When reinforcement is required, materials such as fiberglass, mica, stainless steel or carbon fibers, or other non-orienting fillers are added to the formulation. Today, PBT-based products are used in virtually every type of industrial, medical, and consumer application imaginable.

A slightly engraved contrasting mark was created
using an FH marking head and 25 watts of power.

This electrical connector is manufactured from PBT with 30% glass fiber reinforcement. In addition to the engraved mark (typical of CO₂ lasers), the glass fiber adds an easily readable dark contrast to the mark due to the reaction of the glass fiber to the beam. It is interesting to note that when reinforcing filler materials are added to plastic formulations, CO₂ lasers can often create contrasting marks in a less expensive and much safer manner than shorter wavelength YAG lasers.

To achieve the cycle time required for this application, we selected an FH Series marking head with a 125 mm focusing lens (180 micron spot with a 3 mm depth of focus) to steer the beam from our sealed CO₂ laser. We setup the eight-character string in WinMark Pro using one of WinMark’s twelve built-in fast marking Stroke fonts. At a power of 25 watts and a marking velocity of 25 inches per second, we created the mark in a cycle time of only 0.14 seconds per connector.

Cutting Silicon Carbide Sandpaper

Sandpaper is a generic term for very different types of abrasives including garnet, a naturally abrasive silica mineral, iron oxide, and synthetic materials such as aluminum oxide, silicon carbide and zirconia alumina. Depending on whether these materials are intended for use by hand on a pad or sanding stick or destined for a mechanical drum, belt, or disc sander, the abrasive may be bonded to a paper, foam, cloth, or fiber backing.

What these very different combinations of abrasives and backings have in common is that they are all easily cut using a CO₂ laser. The laser’s obvious advantage is that its non-contact cut method is far superior to the mechanical cutting of abrasive materials. The less obvious advantage is that more and more abrasives are being pre-cut for ease of installation and use. From specialty pre-cut fan shapes for sanding sticks to the more common circular and rectangular shapes for disc, belt, and pad sanders, manufacturers are responding to the need for custom-cut abrasives to fit their products.

220 grit silicon carbide cut using 100 watts of power produced clean cut edges.

This photo illustrates the laser’s versatility for cutting shapes. After importing a CAD drawing of the required shape, we cut this sample of 0.040” aluminum oxide paper at a speed of 125 IPM using 125 watts of power.

Using an XY table, we cut paper-backed 220 grit silicon carbide (0.015” thick) using 100 watts of power at speeds of 1400 inches per minute (IPM). A thicker (0.0295”) sheet of silicon carbide with a paper/cotton backing was cut at line speeds of 850 IPM with 100 W and speeds of 1750 IPM using 200 watts of CO₂ power.

To process these samples, our XY beam delivery setup consisted of a 2.5” positive meniscus focusing lens that provides a 100-micron (0.004”) spot with a 1.8 mm (0.07”) depth of focus. For assist gas, we used clean, dry air at 20 PSI.

Browse Synrad's Applications Database

Search our online library for more applications of Synrad's sealed CO₂ laser technology. Sort by material, process, or industry.
http://www.synrad.com/search_apps/Default.htm

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Synrad, Inc.

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Tel: 1-425-349-3500

Fax: 1-425-349-3667

E-mail: synrad@synrad.com

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