Just as marking is important in life, it is also an essential element in the manufacturing process of many products. Product markings can take many forms, including logos, QR codes, and serial numbers. In some industries, putting a unique mark on each component is essential for traceability.

However, the problem is that common static marking techniques are not suitable for modern automated manufacturing processes that focus on minimizing cycle time. But if their budget allows, the factory has another option: a fully automatic laser marking system designed for integration into the production line. As the parts move along the production line, these systems can complete their work without slowing down the production speed, thereby marking "on the fly."

You can also use ink for dynamic marking, but companies that sell laser systems say their technology is a better choice. On the one hand, they pointed out that lasers can leave more durable marks on parts.

The laser will leave indelible marks on the parts. Image courtesy of TRUMPF

"Compared with inkjet printers, the use of lasers can change the material and obtain more scratch-resistant markings, where the markings are only on the surface and not on the surface," said Albert Jung, a marking technology expert at Trumpf Inc.. Farmington, Connecticut. "You can scrape off the ink, but the (laser) mark needs to be rubbed off the steel part."

In addition, the laser marking company stated that their system is more reliable than the inkjet system, whose nozzles may become clogged and difficult to mark.

Therefore, “they constantly need maintenance,” said Jerome Landry, an application specialist at Laserax Inc. in Quebec City.

In contrast, he said that the laser system does not require maintenance.

"You install it," Landry said, "basically you have something that works."

Then there is a comparison of consumables.

Rick Jones, chief support engineer at Pryor Technology Inc. in Ashland, Virginia, said that sellers of ink-based systems “really make money from consumables—inks, solvents, and other things used in the process.” But in the laser marking process, "the consumables are almost zero."

Laser marking is a fully automatic process that can mark parts in a fraction of a second. Trumpf's system uses software to calculate the speed of the conveyor belt carrying the parts and align it with the speed of the laser mirror moved by a pair of motors. Jung explained that this allows the system to mark the part while it is in the laser scanning field.

Although users do not have to pay for ink and other consumables, lasers are a large item. According to Landry, the cost of the laser instant marking system is approximately US$60,000 to US$120,000, while the cost of the ink system is approximately US$10,000 to US$30,000. However, he added that over time, the laser system will eventually make up for this cost difference by saving ink and other consumables. He said that in a high-volume manufacturing business, this may take a year, and in a slower production environment, it may take "two to three years."

Slowing down the marking line also means slowing down the production speed.

Therefore, “when integrating the laser for marking into an automation cell, you need to ensure that the extra steps do not reduce the capacity of the process,” Landry said.

One way to speed up laser marking to meet production requirements is to choose higher power lasers.

"In a way, this is scalable," Jung said. "So if your mark takes a second on a 10 W system, you can expand to a 20 W system and reduce the time to half a second."

This customized dynamic laser marking system is designed to meet the requirements of a specific production process. Image courtesy of Pryor Technology

Jones stated that the 20 W system is "very standard" for industrial marking applications, but he believes that Pryor Technology has provided customers with up to 300 W laser power.

Of course, the disadvantage of increasing the laser power is that it will also make the laser more expensive.

"When you increase the power to meet the target cycle time, the cost increases significantly," Jones said.

For those who want to mark faster but already use the highest available laser power, other options can help align the marking process with production goals. One option is to purchase a second laser marking system. Jung said the two systems can be deployed in several different ways. One method is to use these two systems on the same production line, with the first laser marking every part encountered by the assembly, and the second laser marking the remaining parts further downstream. Or the manufacturer can use two conveyor belts and a laser marking system.

Another consideration when time is of the essence is the trademark itself.

When the part crosses the marking area, Jones said, "The time you can effectively mark it is limited, which is driven by the application. Some people have 15 to 30 seconds; some have half a second. When you only have half a second Over time, sometimes you have to compromise on your mark."

This means that users of dynamic markup systems may have to reduce the size of individual characters in the logo or mark and/or reduce the amount of content in the mark. So, for example, instead of 12 characters each 4 mm (0.16 inch) high, a mark may have to be reduced to five characters each 3 mm (0.12 inch) high to meet application requirements. Or, time-conscious manufacturers may have to choose dark gray markings instead of bold black markings.

Adjusting the process to meet application requirements is not the only task for manufacturers to choose instant laser marking. Another aspect is to figure out how to deal with the potential dangers brought by lasers in the production environment.

"For fiber lasers, a unique challenge is that the human eye cannot see light," Jones said. "It can detach your retina in a very short time, and you will even know that you blinked-and you will be blind forever. Therefore, you often need to shield the system or close the entire room away from human eyes."

Landry said that when the Laserax system is installed, the marked area will be partially enclosed to ensure that it is "Laser Safety Level 1".

This means that the machine area is safe for people who are not wearing protective equipment.

In addition to being harmful to humans, laser marking can also have unacceptable effects on certain components.

The LXQ fiber laser marking system is designed for rapid integration into the production line. Image courtesy of Laserax

Regarding the effect of laser marking on the quality of parts, “it is suitable for most industrial applications because it only produces a surface roughness of about 30 microns (0.001 inches),” Landry said. "If you put your finger on the marking, you will feel "it's a bit rough." But it did not dig in the material, nor did it really change anything in the structure. "

Nevertheless, he said, Laserax's instant marking system has not been used by medical manufacturers due to the strict requirements of medical manufacturers for surface finish.

Manufacturers of thin-walled parts in any industry should worry about laser marking. These manufacturers can mark on the fly, but they may have to accept a mark that is very different from the mark they put on a stronger part.

"If you have a thin metal sheet and want a very dark mark, you can engrave 5 to 10 µm (0.0002" to 0.0004") black on the top of the part, but you will introduce a lot of heat," Jung said . "If this warps the part, you need to change the process."

For example, manufacturers can switch to exquisite white engraving, which only affects the top 2 µm (0.00008") to 5 µm of the part surface.

"You are introducing less heat now, but you will still leave visible marks on the parts," Jung said.

Although most suitable for high-speed production lines, dynamic laser marking can play an important role in many manufacturing environments.

"Anywhere you have let the product move in an automated fashion and don't want to take it out of the process for additional operations, it allows you to mark it correctly," Jones said.

This is crucial, because marking time can accomplish or destroy certain facilities. He said that a factory that produces one jet engine component per month may have enough time to mark the product.

However, in other cases, if the cycle time "exceeds the target tenth of a second, it can shut down the plant," Jones said. "With dynamic marking, your impact on the system cycle time is almost zero."    

William Leventon is a contributing editor of "Cutting Tool Engineering" magazine. Contact him by phone 609-920-3335 or email wleventon@gmail.com.

Laserax Inc. 844-471-0144 www.laserax.com

Pryor Technology Inc. 804-496-6669 www.pryortechnology.com

Trumpf Inc. 860-255-6000 www.trumpf.com

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