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Engraving Plastic with a Fiber Laser

Most people who have been in the industry for a while know that a fiber laser can mark bare metal, which is something that a CO2 laser can’t do. But did you know that a fiber laser can mark plastic too? Well, certain kinds of plastic that is.

Rowmark LLC, Findlay, OH, has introduced a new plastic material that is designed specifically for fiber lasering. I’ll take a look at this new material in this article, and also talk about other plastics that can be marked with a fiber laser.

Before I review Rowmark’s new material, we need a quick physics lesson about why a fiber laser, more specifically a “solid state pulsed ytterbium fiber laser,” will mark metal and some plastics while a CO2 laser will mark most plastics but not metal that doesn’t have some kind of coating on it. Fiber lasers and YAG lasers are often thought to be the same. They are not, but the frequency produced by these two types of lasers is close enough that they can mark many of the same materials.

FiberGrave allows lasering a respectable image even with a poor quality photo. This image is a photograph of a newspaper photograph that was photocopied and then engraved on FiberGrave.

FiberGrave allows lasering a respectable image even with a poor quality photo. This image is a photograph of a newspaper photograph that was photocopied and then engraved on FiberGrave.

To keep it in terms I can understand, the difference between a fiber laser and a CO2 laser is in the frequency of the laser beam being generated. Granted, the two laser beams are generated in totally different ways (one is done with a CO2 gas-filled tube while the other is done totally with solid state electronics) but the end result is a difference in light frequency, or wavelength.

As you know, all light (visible and invisible) can be measured in frequency. Ultraviolet light, for instance, is so high on the spectrum the human eye can’t see it while sunlight and a variety of artificial types of light are in a very narrow range of frequencies that we can see.

What this boils down to is the frequency of a fiber laser won’t have much effect on the engraving plastics we are familiar with.

Rowmark recently introduced their first material intended exclusively for the fiber laser. It comes in two colors, black and white, and is a single-color material. That is, it is the same color throughout the plastic. This is quite different from the two-color plastics consisting of a cap and a core that are commonly used with CO2 lasers.

Rowmark’s new material is called “FiberGrave.” In the realm of laser engraving in our industry, this material fits in nicely for those who have applications for using a fiber or YAG laser (as opposed to a CO2 laser) to make highly detailed markings on a durable material other than substrates like traditional injection molded plastics, aluminum or stainless steel. The material is easy to handle and fabricate, and can produce durable markings such as photographs and barcodes. It is also UV stable for applications such as industrial tags, labels and ID plates.

FiberGrave is available in two thicknesses, .020” and .040” or a little less than 1/32” and approximately 3/64” thick. FiberGrave is sold in full sheets (24” x 48”), half sheets (24” x 24”) and quarter sheets (12” x 24”) just like most of the other Rowmark products. Both colors have a matte finish on both sides and both sides can be marked. Only one side has a protective film on it to protect it from scratches, but the material is highly resistant to scratching so more often than not, both sides can be used.

Rowmark provides two free samples (one white, one black) of FiberGrave that you can test. This is the result of engraving a grayscale from a CorelDRAW file.

Rowmark provides two free samples (one white, one black) of FiberGrave that you can test. This is the result of engraving a grayscale from a CorelDRAW file.

When marking plastics using a fiber laser, the term “engraving” is really not accurate since the laser doesn’t remove any material. It only changes the color of it. Thus, a more accurate term would be to “mark” the material.

FiberGrave is a modified acrylic material. You see that term a lot on the specifications list for various engraving plastics and it means the base product is acrylic but it has other chemicals added in to make it perform as desired.

As you might expect, the black FiberGrave material turns white when exposed to a fiber laser. This effect is sometimes called “bleaching.” That is the same term used when marking anodized aluminum as the heat of the laser literally bleaches out the color of the anodized coating. In the case of the white FiberGrave, the term “bleaching” doesn’t really work since the laser turns it silver. Perhaps there is a term for it, but I don’t know what it is.

This I do know: The mark created by a fiber laser is incredibly precise. Partly because the spot generated by a fiber laser is extremely tiny (.0001”-.0005”), but partly because the materials it marks are capable of holding such a tiny mark. Should the material tend to melt or deform, the size of the mark would be greatly exaggerated and one of the most valuable assets of the fiber laser would be lost—its ability to create extremely tiny text, barcodes, etc.

Some plastic-like materials that respond to a fiber laser, including FiberGrave, will not only change color when marked, they will also accept grayscale gradients. If you are not familiar with grayscales, they are commonly used in photography or lithography to determine the proper exposure of film, printing plates, etc. There are special charts, or scales, that can be purchased or created to replicate the various shades of gray.

This is important for at least two reasons. First, it means we can create a mark in these materials in silver (or white) but we can also mark them in an almost infinite number of shades of black or silver. This can create the illusion of shadows and depth, which is vital when engraving something like a photograph. Secondly, it gives us the ability to mark relatively precise gradients for use on things like medical equipment, knobs, control panels, test instruments and scales of all kinds.

FiberGrave is UV stable so it can be used as an exterior product which broadens the applications for the material. Plus, if it is used for a job requiring extremely high precision, such as a medical scale, there should be little concern about the markings shifting over time. The material is also flexible and easy to work with. It drills and cuts like most flexible engraving plastics, can be sanded and bent using a strip heater, and will accept both 2D and 3D barcodes that are easily scanned. The material is also relatively inexpensive. A quarter sheet of .020” costs about $15.50 and .040” about $19.00.

Although a fiber laser can’t cut this material, it can be cut with a shear or scored and snapped. For non-square shapes, it can be cut using a CO2 laser—a process made much simpler if you have a laser with a camera system—but it can also be done if both lasers are aligned properly (a simple task of trial and error). Double-faced tape can also be applied to the material for making control panels, signage and many other products.

There are a great many other plastic-like materials that can be marked with a fiber laser. Epilog Laser provides a list of many of them, many of which you will probably never come in contact with but it’s a good list to keep next to your laser should the opportunity arise. Here’s the list from Epilog:

·                     ABS (white/black)

·                     Bayer 2807 Makrolon Polycarbonate

·                     Bayers Bayblend FR110

·                     Carbon Nanotube

·                     DAP - Diallyl Phthalate

·                     Delrin, Colored (white/black)

·                     GE Plastics Polycarbonate Resin 121-R

·                     Molybdenum

·                     Nylon

·                     PEEK, Glass Filled

·                     PEEK, White

·                     Polybutylene Terephthalate

·                     Polycarbonate (black/white)

·                     Polysulphone

·                     Rynite PET

·                     Santoprene

·                     Teflon, Glass Filled

 

Let’s consider a few of these, especially the polycarbonates. Polycarbonates are everywhere. We use them in everything from roofing panels to medical devices. They are constructed of polymers and carbons that are easily molded or fabricated as thermal plastics. One of their great advantages is they can be heated to their melting point (311˚ F), cooled and reheated again. This is unlike thermoset plastics that can only be heated once. These are usually clear but don’t have to be. You will find a variety of colors available and they are sold under common trade names, Lexan and Makrolon. Many have other materials blended in with them such as acrylic or even ABS.

Cast acrylic marks very well with a fiber laser, but extruded does not as shown here.

Cast acrylic marks very well with a fiber laser, but extruded does not as shown here.

Polycarbonates mark easily provided they are opaque. A fiber laser’s light beam passes through clear materials without creating a mark so clear polycarbonates are in the realm of the CO2 laser which can surface mark clear materials. Translucent polycarbonates typically allow the laser beam to pass through the material and therefore don’t mark with a fiber laser. They can, however, be marked with a CO2 laser.

The acrylic you buy from the various distributors comes in two forms: cast and extruded. Typically, we say that extruded acrylic can’t be lasered (more about that in a moment). Therefore, cast is always used when being marked with a laser. Both CO2 and fiber lasers will mark cast acrylic, but their end result is quite different. With a fiber laser, clear acrylic won’t mark but the results on black acrylic can be stunning as it marks with an almost pure white image. This is great for creating plaques, signs and a host of other products. White acrylic (opaque) marks silver much like FiberGrave or ABS.

Although extruded acrylic is usually crossed off the list of what either type of laser can mark, the fiber laser does an interesting job on extruded black acrylic that you might find an application for. This served me well in doing a job for a new foundation and saved considerable money in the process since extruded acrylic is considerably less expensive than cast.

What I found was that extruded acrylic would bubble up and turn white when hit with a fiber laser. The quality of the mark isn’t such you would want to make plaques with this method but for my application, it worked great. The biggest negative of this method was the white image wasn’t consistent. Grab a piece of extruded black acrylic and try it for yourself. It is a good thing to know, even if you never actually use the technique.

Another material you are likely to come across is ABS or acrylonitrile butadiene styrene, which is a common thermoplastic polymer. As you know, ABS can be cut on a CO2 laser, but it doesn’t engrave very well. This is because it wants to melt before the material is vaporized and that usually leaves a discolored mess. I have been able to engrave some ABS on my CO2 laser however, especially if the core is black. Gold metallic with a black core, for example, usually does okay in a CO2, especially for something small like a name badge.

In a fiber laser, however, ABS marks pretty well. To get ABS to mark as well as the FiberGrave material usually takes more power than the FiberGrave, but the results are pretty good. Many of the older lines of Rowmark engraving material such as the Mattes are made with ABS plastic, so they mark pretty well with a fiber laser. Johnson Plastics Plus, Burnsville, MN, also sells a black ABS “utility” sheet in both 1/16” and 1/8” thicknesses that can be fiber lasered.

PEEK plastic (poly ether ketone) is a high performance, high temperature plastic that can withstand temperatures up to 500˚ F which makes it suitable for use in autoclaves (a high pressure, high temperature chamber used for industrial and scientific processes). They can be further reinforced by adding up to 30% of their volume with glass or carbon fiber. These materials are commonly used to make molds or used in 3D printers.

Teflon is another great product to mark with a fiber laser. Teflon is the material that is made into very thin sheets and referred to as “Baker’s Sheet” or PTFE. This is the same material used in heat presses for sublimation and heat transfer material. For laser engraving, the material (usually a cream color) comes in thicker sheets which can be pretty costly. A 1/8” thick sheet that is 12” x 24” costs about $75. The advantage of this material is that it is extremely tough, very durable and it handles high heat.

Nylon is another markable product. Available in both thin and thick sheet stock, it generally comes in black, white and a cream color called “opaque white.” It has excellent chemical resistance and it remains solid up to about 220˚ F. It is easy to work with but fairly expensive. Nylon is commonly used to make gears, moving parts, bearings, rollers and other high abrasion parts.

Delrin is actually a brand name used by DuPont for polyoxymethylene (POM) which is also known as acetal, polyacetal and polyformaldehyde. It is a thermoplastic used to make precision parts—often ones formerly made of brass or copper. It is sold under a host of brand names including Delrin, Ultraform, Celcon, Ramtal, Duracon, Kepital, Polypenco and Hostaform.

It is unlikely anyone will ever come into your shop and ask if you can get a sheet of Hostaform and mark it, but it isn’t unlikely someone will come into to your shop someday with a piece of plastic and either not know what it is or even if they do know the name, you won’t have a clue what it is even after you hear the name. When that happens, you can come back to this article (stored next to your fiber laser) and at least have some idea of what it will do when exposed to a fiber (or YAG) laser.

A comparison of grayscales engraved on black and white ABS and FiberGrave. Black FiberGrave marks much whiter than ABS. The white ABS requires considerably more power.

A comparison of grayscales engraved on black and white ABS and FiberGrave. Black FiberGrave marks much whiter than ABS. The white ABS requires considerably more power.

Can you mark these materials with your CO2 laser? Probably not. Just as the plastics that don’t engrave well in your fiber laser, these won’t do well in your CO2. CO2 lasers are pretty much limited to working with acrylics (most laser engravable sheet stock is actually made from acrylic).

Like to see for yourself how these various materials perform in your fiber laser? Many are available from Amazon in forms that are affordable (6” x 6” for example). Those not on Amazon can always be ordered from companies like E-Plastics (www.eplastics.com), A & C Plastics (https://www.acplasticsinc.com), Interstate Plastics (www.interstateplastics.com) or Advanced Industrial (www.cncplastics.com).

One of the advantages of Rowmark’s FiberGrave over all these materials is that it is consistent. You can know what the end result is going to be when marked with a fiber (or YAG) laser. You can control the image easily by comparing what you want with the grayscale and you can even engrave photographs if you want to.

One word of caution about the .020” sheet of FiberGrave. When engraving solid images such as photographs or very large text, you may find it wants to “bubble up” or warp while being engraved. Although this issue might be permissible in a CO2 laser, it is never permissible in a fiber laser. Because the focal length with a fiber laser is so critical, even a few thousandths of an inch will take it out of focus and cause distortion or keep it from making a mark at all. For this reason, all of my samples were done on the thicker .040” thick material which handled the heat with no problem and remained flat even when engraving a photograph.

Rowmark will be happy to send you a couple of samples of FiberGrave that you can play with yourself. If you request free samples of the material, they will send you two pieces (one white, one black) of the material that measure approximately 2.125” square. Give it a try!

Engraving Plastic with a Fiber Laser
J. Stephen Spence

Copyright © 2020
As Printed in April 2020, Volume 45, Number 10, The Engravers Journal

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