Choosing a marking laser

Many companies that invested heavily in lamp markers 8-10 years ago are now faced with the task of upgrading their aging markers

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Many companies that invested heavily in lamp markers 8-10 years ago are now faced with the task of upgrading their aging markers

Glenn Prentice

Not all lasers are created equal. For the majority of marking applications, the lamp-pumped lasers utilized produce higher power. Fiber lasers, while producing lower power, possess higher beam energy density, and diode lasers are a compromise between the two. Most marking applications can be accomplished using any of these technologies. However, some applications lend themselves to a particular technology. It is advisable to always run test samples before selecting a new laser. Check the mark’s contrast, cycle time, and linewidth to ensure you are satisfied with the results. Additionally, other factors are involved in the decision process. The following is a compilation of commonly asked questions and answers.

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FIGURE 1. The smaller line is from a 20-watt fiber laser and the heavier line is from an 80-watt lamp-pumped laser. Both lines were generated from a lens with a 12-inch marking field.
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Q: How long can I expect my new laser to operate between diode replacements?

A:Water-cooled diode lasers typically manage from 8000 to 10,000 hours on a diode pack(s), while air-cooled diode lasers routinely manage from 15,000 to 20,000 hours. Fiber lasers reportedly can operate for more than 100,000 hours before requiring replacement. Replacement costs vary for each technology, so you should factor these costs into your decision. Fiber lasers generally enjoy a significantly lower cost per hour than either lamp or diode pumped.

Q: What are the annual operating costs of a diode or fiber laser compared to a lamp-pumped laser?

A:Fiber lasers have a substantially lower annual operating cost than lamp or diode pumped. Based on national averages, expect to spend $720 annually to operate a fiber laser1 compared to $3200 for a lamp- and $4100 for a diode-pumped system.

Q: What are the maintenance requirements for a fiber or diode laser?

A: Water-cooled diode lasers require some of the same maintenance as a lamp-pumped laser (excluding the external chiller). However, they do not require the replacement of the lamp and lamp flow tube on a regular basis. Air-cooled lasers, such as the fiber, have a less complex design and are virtually maintenance-free. Periodic cleaning of the optics and thorough inspection of all connections is all that is required.

Q: Will the diode and fiber laser operate in the same environment as a lamp-pumped laser?

A: Lamp-pumped lasers tend to tolerate a greater range of environmental extremes and conditions than diode or fiber lasers. Air-cooled diode and fiber lasers are more sensitive to ambient temperature and airborne contaminants. Ambient temperatures exceeding 93º F require a cooler of some type. If there are airborne contaminants such as oily mist a filtration system must be employed, but this is a good recommendation for any laser system in a harsh environment.

Q: Regarding site preparations, what changes are necessary to switch from a lamp to a fiber or diode?

A: Minimal changes are required for a water-cooled diode laser. An external chiller is no longer required, saving floor space. Electrical consumption will also be reduced in most instances. An air-cooled laser like a fiber requires even less floor space. These lasers have the smallest footprint in the industry and are easily integrated into a production line. The galvo heads are usually mounted on a flexible cable allowing for placement virtually anywhere on the production line. The laser is powered by 115VAC/20A service, so supplying electrical connections is very simple.

Q: Regarding integration, can a diode or fiber laser be integrated into my current enclosure?

A: Diode lasers can often be integrated into an existing enclosure with minimal modifications, while fiber lasers require more extensive modifications to integrate the computer, driver unit, and galvo head into the enclosure. One of the biggest changes that must be taken into account is the probable difference in beam position and mark field size relative to the previous technology. These changes may require mechanical alterations to the workstation.

Q: Will my existing programs run on a diode or fiber laser?

A: Most newer software packages are able to run programs created on earlier software versions. However, there are a number of lasing parameters that must be “fine tuned” for the new laser. The critical lasing parameters affected are:

• Linewidth: Diode and fiber lasers have a smaller linewidth than lamp-pumped lasers (see Figure 1). In fact, fiber lasers typically have linewidths almost 70 percent narrower than lamp-pumped lasers. Multiple passes are required to fill in fonts with a fiber compared to a single pass with a lamp-pumped laser. Many software packages have specially created fonts to compensate for the narrower linewidths of fiber lasers.

•Current settings: Diode lasers operate at approximately the same or slightly higher current settings than lamp-pumped lasers. Fiber lasers are much more efficient and generally require current settings 20 percent lower than those used on lamp-pumped lasers. However, each laser will vary so experimentation is required to get the final settings for current.

• Marking field size: Many older lasers have a maximum of 8-inch round marking fields compared to 12-inch square marking field on newer lasers. This represents an increase of 186 percent in marking area that can be utilized (see Figure 2 ).

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FIGURE 2. Newer lasers offer a 12-inch square marking field, representing an increase of 186 percent in marking area that can be utilized.
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•Marking speed: Typically, diode lasers are slightly slower than lamp pumped while fiber lasers are generally faster. Marking speed is material dependant and experimentation is necessary. If the lamp-pumped laser being replaced is more than five years old the marking speed can normally be increased due to the enhanced speed of the newer galvos. Note, however: If identical linewidth results are required, the finer linewidth of the fiber and diode-pumped system may offset any marking speed gains obtained.

• GST settings: GST, or galvo settling time, is the delay programmed into a marking program to allow the galvo time to stabilize. Advances in galvo technology allow galvo motors to operate much faster. This is a benefit that is available with any technology chosen. Improvements in the galvos allow for faster marking speeds, much as improvements in brakes and tires on race cars allow them to go deeper into a turn without breaking and accelerate more quickly upon exiting the turn.

• Skip speed: Newer, faster galvos permit a higher skip speed than older models allowed. Skip speed is the ability of the laser system to rapidly accelerate across areas where no marking is occurring such as between letters or from one graphic to the next. Older marking programs should be modified to take advantage of the increased galvo speeds and skip speeds.

• Border/fill - line gap feature: Many newer software packages feature the ability to control the line spacing as well as the gap between the border and fill of a graphic or filled True Type font dynamically and from within the laser software. Early software packages relied on third-party programs to do this function before reaching the laser. This feature allows the programmer to control the positioning of the fill line against the border (see Figure 3) and prevents these fill lines from running over the border, which creates a “jagged” edge when looking at a precise graphic. The ability to control the line spacing is both useful and necessary for speed control, grayscale, and the ever increasing demands of today’s graphic requirements and the ability to make these changes within the laser software save considerable time and expense.

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FIGURE 3. Many newer software packages feature the ability to control the line spacing as well as the gap between the border and fill of a graphic, which allows the programmer to control the positioning of the fill line against the border.
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There are many advantages when implementing one of the new laser technologies. In many instances, the cost of a new laser system is only marginally higher than the cost of upgrading an old system. Upgrading an older laser is analogous to upgrading an older computer. Due to technology changes, you are not able to take advantage of the latest features in both hardware and software. Consequently, performance, while improved, is not what a new system would offer. The user is then left with upgrading the system again or replacing the system in a much shorter time than if he had purchased a new laser.

New laser technology, be it fiber, diode pumped, or a newly designed lamp-pumped laser marking system, is quite exciting to embrace for a customer who has used a lamp-pumped system for several years. The downsides of converting to the newest systems are few and the benefits of higher throughput, lower operating costs, and easier maintenance quickly pay for themselves. This conversion can be done into either a new workstation to utilize the technology advances made in tables, indexers, controllers, and so on, or, as seen here, an existing workstation can often incorporate the new laser technology without major changes and expense.

Footnote

1. Costs based on operating a typical laser eight hours per day, 254 days per year.

Glenn Prentice is product manager at Baublys Control Laser Corp., Orlando, FL. Contact him at GlennP@controllaser.com.

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