Laser system marks tube, pipe, profile on the fly, complements mill operations

Product identification and traceability are required for many applications, whether by code or by contract, and the requirements are bound to grow as time goes on. Common examples are tubing used for an aerospace application, a hollow structural section used for a construction project, or pipe used for transporting oil. Easy-to-read, permanent markings can provide critical assistance in identifying material in manufacturing plants, constructions sites, or oilfields, helping to ensure that the assembly or construction process goes smoothly. For many applications, traceability from the mill to the finished product is a must and helps to account for every step that was used to process the workpiece.

Marking tube and pipe often is a tradeoff between durability and speed—the longest-lasting markings can take the most time to make. However, Cajo Technologies, New Orleans, has spent no small amount of time and energy optimizing laser marking on the fly and has come up with a system that makes durable markings and runs fast enough to keep up with many of today's fastest tube and pipe mills.

"These are not high-powered lasers," said President Ismo Rantala. "They use much less power than the lasers used for cutting or welding." The company's systems run from 20 to 300 watts, substantially less than the 2,000 to 4,000 W commonly used to cut steel. For marking carbon steel tube or pipe at common mill speeds, 100 W is typical.

Still, they have some commonalities with laser cutting machines. Just as their big brothers work without hard tooling, laser marking systems don't use ink, additives, or other consumables, and like laser cutting, the process is fast, requiring no curing time. Because they have no moving parts, they have long service lives, in some cases exceeding 100,000 hours (that's 24 hours a day, 356 days a year, for more than 11 years).

Today's laser marking systems are versatile, as well. While CO2 lasers work well on carbon steels, stainless steels, and aluminum alloys, the company's marking lasers are more akin to fiber lasers in their ability to work on nearly any alloy.

"In the old days, we had to consider the material carefully," Rantala said. "These days, we can mark about 90 percent of all materials," referring to metals and polymers used as cable jacketing, another big sector in the fast-growing laser market.

Just as they can handle a big variety of materials, they also work in a wide temperature range.

"Nothing we have seen so far is too hot for this process," Rantala said. "We have one application that marks nickel bars right after they are removed from an oven, and the heat actually helps with marking clarity."

One critical element is stability. Every welding mill has a vast number of moving parts, many of which contribute to continuous motions up and down the line as the tube or pipe is formed, welded, and cut off. Two methods are available to provide a steady working surface for the laser. One is matter of mounting the laser to the mill. As long as the laser is mounted rigidly to the mill, it will vibrate along with the mill, so the relative motion between the workpiece and the laser is negligible and results in clear, readable markings. The other method relies on homemade jigs, fixtures, or wheels to prevent vibrations as the tube travels along. "We need about 4 inches of very stable travel," Rantala said.

Clean Surfaces. Making tube and pipe can be a bit messy. The raw material and the roll tooling need a barrier, a film of lubrication, to prevent direct contact between them. Also, on welding mills, the seam is cooled immediately after welding by a flood of coolant, adding another compound to the material's surface. Can a laser marking system—which uses nothing more than a highly focused light beam—successfully mark such a surface? Indeed, it can. Depending on the line speed, a single laser can burn off coolants and lubricants and make the necessary markings. If the line speed is too fast for a single laser, Cajo supplies a system with two lasers. The first does the cleaning and the second does the marking.

Outdoor Storage. Doesn't quite a bit of tube and pipe inventory get stored outdoors? Yes, it does. The larger the diameter, the less efficient indoor storage becomes—nobody wants to waste valuable warehouse space storing hundreds of thousands of cubic feet of air—so quite a bit of it gets exposed to the elements, and oxidation is bound to happen. Even after weeks of exposure, the marking must be readable. The markings are durable in such conditions—Cajo has marked cables and pipes for ocean use—but even so, the company knows that each customer needs to see some proof. Standard salt spray testing, such as defined by ASTM B117, ASTM G85, ISO 9227, and JIS Z 2371, is a possibility, but for a customer who doesn't need a formal test, Cajo can provide a less-structured evaluation.

In one instance, Rantala tested a length of pipe the common-sense way. No fancy testing apparatus, no spray booth, no closely controlled (yet abusive) environmental conditions of any sort. He replicated outdoor storage by storing some pipe outdoors.

"One of our customers, the world's largest manufacturer of pipe for oil, gas, and chemical applications, wanted me to test our markings," Rantala said. "I marked a length of pipe, took it home, and left it in my back yard to rust for three weeks. I used a damp, salty towel, and wetted the towel every few days." In the end, the markings were still readable.

For many years, industrial marking systems imparted letters and numerals, meant to be read by people, but the introduction of bar coding—popularized by use in the grocery industry in the 1980s—led to big changes in how information is recorded, read, and used. No longer would retailers have to mark products with price stickers and rely on cashiers to read them and enter prices correctly at the cash register. Prices could be changed instantaneously, and if the new price was just a temporary markdown, it could be changed back to the original just as quickly. This was a boon to efficiency, accuracy, and inventory control, but it's nothing compared to what industrial marking does for commercial activities today. Modern systems are extremely versatile, allowing system developers like Cajo quite a bit of latitude in how marking systems are built and programmed.

"This process has been around for 40 years or so, but in the last two or three years, we have seen big changes in the industry—cheaper lasers, more capabilities, and so on," Rantala said.

How fast do they run? It depends on the marking. A big contributor to modern marking speed and accuracy is the quick-reaction (QR) code, the common two-dimensional code that is used for nearly everything these days. The data storage capacity of the QR format is so large that, for a given amount of information, a QR code needs just 10 percent of the space as a bar code.

A QR code isn't the only alternative to a conventional bar code. Data matrix is another 2-D code, but it's smaller, easy to read, and, according to Rantala, one of the fastest-growing standards for industrial traceability.

Cajo expands on these codes’ capacities by sourcing lasers that have the smallest available beam diameter: 16 microns. This means the company's systems can make extremely small markings.

"The smallest marking we have made measured 0.75 by 0.75 millimeters," he said. "Such markings require a microscope reader." This isn't the limit, Rantala added; the markings can be smaller still.

Most manufacturers don't use a marking that is that small, but indeed Cajo can reduce the marking size so the system needs less time to make each mark. The manufacturer has other ways to speed up the marking process, if necessary. Because QR isn't the only format available these days, Cajo might use one of the other formats.

"When the customer needs a very fast system, we go to single-line data matrix," Rantala said.

So, how fast do they run? It depends on the application. Every application has unique parameters, so without some detailed knowledge about the product, the material, the process by which the product is made, and the environment in which it's made, determining the line speed is impossible. However, the company can come up with a good estimate so a tube or pipe producer doesn't have to invest in a system and do his own testing to find out.

"Nobody wants to buy a system unless he knows it's going to work," Rantala said. "We have a few run tables, so we begin testing at Cajo using actual product samples, then finish the testing at the customer's facility."

The company also can use a higher-power laser to get a little more speed from the system.

So, how fast do they run? Manufacturers have two more options to consider. One is error correction. Data matrix codes can incorporate error correction—QR has four levels—so that a damaged code might still provide 100 percent of the original information. For a manufacturer that doesn't need the highest level of error correction, stepping down a level or two might speed things up a bit.

Also, for stainless steel products, Cajo has developed a process that brings out the colors inherent in these alloys, but more manipulation takes more time.

So, how fast do they run? One of the fastest systems Cajo has built—for a customer with a wire application—runs at a dazzling 2,350 feet per minute.

One of the company's success stories concerns a conveyor systems manufacturer. In this case, it's not so much speed as it is versatility, illustrating how the system can benefit Cajo's customers’ customer.

"The company is in the process of marking all of it products with QR codes and connecting all of these codes to its customer service department," Rantala said. "For example, when a customer scans the QR code with a smartphone, he can get immediate access to documentation for using or repairing the product, and he can even use his phone to order a part."

This is a boon to customer service, making everything easier for both Cajo's customer and the customer's customer.

Cajo Technologies Inc., 1521 Washington Ave., New Orleans, LA 70130, 800-796-3080, www.cajotechnologies.com, [email protected]