SYNRAD, INC. - http://www.synrad.com  
Thursday, August 7, 2008
Issue 193

Direct Part Marking
on Stainless Steel

Marking Polyetherimide
(Ultem) Connectors

Cutting Polycarbonate
Filter Media

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.


Direct Part Marking on Stainless Steel

Many large industrial manufacturers as well as the Department of Defense now specify direct part marking (DPM) of components and sub-components so that each piece has a unique identity that is a permanent part of the assembly. Although there are many methods for marking parts, the best solution for high-throughput manufacturing is laser marking. Laser marking is the most versatile DPM method when it comes to creating permanent marks (marks not affected by normal wear and tear or harsh chemical solvents) that contain data unique to each individual piece speeding by on a conveyor. Despite misconceptions that CO2 lasers are only effective at marking organic or plastic materials, past Applications Newsletters have highlighted many successful marking applications on mild and stainless steel, tool steel, and even titanium. This article highlights one method of using a CO2 laser to directly mark machined stainless steel housings.

Our marking setup consisted of a Firestar t100 laser, FH Flyer marking head, and a copy of our WinMark Pro laser marking software. The Flyer head was fitted with a 125 mm high-power lens that provides a 180-micron (0.007”) spot with a 3 mm (0.118”) depth of focus.



This permanent, high-contrast text on a
machined stainless steel component was
directly marked with a Synrad sealed CO2
laser using 87 watts of power at a speed of
1 inch per second.

The mark consists of three lines of text with a total of 24 characters. We used a filled TrueType® font, Times New Roman, at a Text Height of 3 mm (0.12”) and also set the Text Outline Filled property to Yes.

To produce this mark, we set a Power, duty cycle percentage, corresponding to 87 watts, set a mark Velocity of 25.4 millimeters per second (1.0 inches/sec), and a PWM Frequency of 5 kHz. Overall cycle time to complete the raster-scanned 24-character mark was 27.2 seconds. The accompanying photo shows the result of laser marking the machined stainless surface. The dark, high-contrast mark is a result of carbon migration caused by localized heating of the stainless steel substrate.

In cases where the end user does not require a specific font (such as the Times New Roman font shown), you could reduce the cycle time in this application down to 8 seconds or less by changing from a filled TrueType font to a multi-line WinMark stroke font like “Complex”, “Trip”, or “LiteCom”.


Marking Polyetherimide (Ultem®) Connectors

Polyetherimide, also trademarked as Ultem®, is a high-temperature thermoplastic (rated for continuous use in temperatures up to 356 °F) that features high tensile strength along with good flame and chemical resistance. Polyetherimide is commonly specified for aerospace, automotive, medical, and packaging applications. Its flame resistance combined with low smoke emission also means it is an important material for molded portions of aircraft interiors.

In this application, we were asked to demonstrate the feasibility of laser marking electrical connector housings molded from a polyetherimide formulation that includes a 10% glass fill reinforcement.

Our marking setup consisted of a 25 W sealed CO2 laser, an FH Series marking head (equipped with a 125 mm lens), and our WinMark Pro laser marking software. The 125 mm focusing lens provides a 180-micron (0.007”) diameter spot at the point of focus over a mark field measuring 85.7 mm by 105.6 mm (3.4” x 4.2”).








This high-contrast mark on a glass-filled poly-
etherimide (Ultem) connector was achieved in
0.51 seconds using 25 watts of power at a speed
of 10 inches per second.


In WinMark Pro’s Drawing Editor, we created a two-line, 10-character text object using the European stroke font and set a Text Height of 6.35 mm (0.25”). On the Marking tab, we set a Power, duty cycle percentage, corresponding to 25 watts and a Velocity of 254 mm per second (10”/sec). Because of the radius of the connector housing, we set our focus point midway between the upper and lower extents of the text to ensure a consistent power density across the mark.

Using these settings, we achieved cycle times of 0.51 seconds per part when marking the 10-digit part code. The resulting engraved mark exhibits high contrast, due in part to the 10% glass reinforcement material.


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.

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 with either an XY table or a marking head.







The 31 mm x 21 mm PCTE membrane filters
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. Cut edges
are clean with no discoloration.

Our cutting setup consisted of a 10-watt sealed CO2 laser, an FH Series marking head, and our WinMark Pro laser marking software. The FH marking head was equipped with a 125 mm focusing lens that provides a 180-micron (0,007”) spot with a 3 mm (0.118”) depth of focus over the extents of a 85.7 mm by 105.6 mm (3.4” x 4.2”) mark field.

Using WinMark Pro’s intuitive interface, we quickly created and sized the desired 31 mm by 21 mm (1.2205” x 0.8268”) rectangular shape with four-digit accuracy. On WinMark’s Marking tab, we set a Power, duty cycle percentage, equivalent to 10 watts and entered a cut rate (Velocity) of 1270 millimeters per second (50 inches/second). At these settings, we cut out individual membrane filters in a cycle time of 0.15 seconds per piece. The edges of the polycarbonate filter media are cleanly cut with no discoloration or residue.


Browse Synrad's Applications Database

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

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