"Green" laser marking

July 17, 2009
Increased efficiency of diode-pumped laser markers means an easier cost justification than ever before

Owen Jones

Today the buzzword is "green." When we investigate laser markers from both an energy consumption and monetary viewpoint we can think "green"...even when we are in the 1064 nm range.

Depending on who one listens to, there are either two or three technologies currently employed to produce the 1060-1070 nm wavelength of laser light that is commonly used for most metal and quite a bit of non-metallic marking. This is often referred to generically as a "YAG" laser marker. The lamp-pumped marking system was the first system to enter the marketplace where it dominated the market for more than 20 years. The last decade has brought major changes in the laser marking sector and the product offerings. We've seen the early proliferation of lamp-pumped systems being followed by the introduction of diode-pumped and then fiber based laser markers. It is quite interesting to look at what technological changes within the respective laser pumping methods have done to the operational cost comparison (and subsequent cost justification) of the various types of laser marking systems. This article is based on those many applications where any of the technologies will provide an acceptable result from both a time and quality standpoint and not focus on those applications that are possibly better served by one specific laser system over another.

When the lamp-pumped system ruled the marketplace and the diode-pumped system was just making an introduction, the cost of the lamp-pumped system was said to be about $1.00/hour to operate. This cost made it more economical than the early diode-pumped systems (see Table 1).

From an operational cost standpoint the diode-pumped laser marker was entering the marketplace with a higher cost. Primarily responsible for this conclusion was the relatively inexpensive cost of electricity coupled with the life expectancy and replacement cost of the diode packs that were used to pump the lasing medium. These "newly invented" diode markers initially offered only up to 5000 hour life from their diode packs and the replacement costs were quite expensive. Also, the pumping configuration of the diodes was much less sophisticated and less efficient than is currently available. This factor meant that they often used a considerable amount of electricity (much wasted as heat) and often required water cooling to maintain beam stability and remove the excess heat from the environment.

For the lamp-pumped laser marking system, recent years have seen limited improvements in lamp pumping efficiencies and the cost and useful life of replacement lamps has remained fairly constant. Meanwhile, electricity costs have continued to climb. The big change has occurred within the realm of the diode-pumped laser system. For the balance of comparisons used here I will compare a new diode-pumped laser system with a lamp-pumped system. On a side note: Arguments can be made that a fiber laser is even more cost effective to operate and, that being said, it is important to note that a fiber laser is in reality a version of a diode-pumped laser system. Hence the cost comparison of a lamp-pumped versus a fiber laser system should be at least as valid as is the comparison between a lamp-pumped system and a modern diode-pumped laser marker. Also within my cost comparison, I will look only at the major consumable operational costs of the laser marking system (electricity and the pumping medium replacement) and will not focus on the day-to-day and routine maintenance items such as lens cleaning, filter changing, if required, etc. These typically represent quite a small component of the operational cost of a laser system and are often similar in both cost and frequency of attention required in any of the systems looked at.

Today's diode laser systems offer extremely efficient laser pumping, which translates into very high wall plug efficiencies and the associated low electrical costs. This high efficiency also means that air cooling is often the norm and excess heat generation does not have to be removed from the environment by an external chiller. Also, the latest developments in diode production have given rise to a much greater life expectancy within the laser system before a replacement diode pack may be necessary. At the same time, improvements in production techniques have made these replacement diode packs considerably less expensive on a cost/watt basis. Field replacement is now very easy to do and in short order when required. With modern diode laser systems offering diode pack life in excess of 35,000 hours before replacement is required and a much more energy efficient operation of the laser, their operation cost has now decidedly swung the pendulum to the point of their being much more cost effective to operate than their lamp-pumped counter part. This efficiency also has other benefits such as reduced size of the entire system and the ability to easily manipulate the laser head with robotics or other motion systems. Table 2 shows the relative operational costs of two currently available diode-pumped laser systems.

For this comparison the TRUMPF TruMark Model 3020 and 6020 lasers were used. The TruMark Model 6020 offers more than 3x the peak and average power of the Model 3020. Both have exceptional stability and very low order mode beam quality and offer process times and quality comparable to or better than lamp-pumped systems for many applications.

As Tables 2 and 3 illustrate, both diode-pumped laser marking systems more than demonstrate a much less expensive operating cost than a lamp-pumped laser marking system. Over a 70,000 hour operating life as shown in the examples above, the cost savings for a single-shift operation is more than $2,275/year with either diode-pumped laser marker. These savings increase if your laser utilization increases.

In conclusion, when you investigate a laser marking system, if either the lamp-pumped or diode-pumped technology offers you the results you desire in the cycle time you require, it makes very good sense to consider the operating costs of the laser. Your justification of a laser system may be easier than you think when you look at the operating costs of today's modern diode-pumped laser marking system. The "green" solution you are seeking will put "green" in your pocket as well.

Owen Jones has been in the laser marking industry for more than 28 years and is currently a partner in Precision Technical Sales (PTS), LLC. PTS offers lasers and other marking solutions throughout the Mid-Atlantic region. It also provides consulting services for companies looking for other laser solutions such as micro-welding and cutting and can be contacted via its web site: www.precisiontechsales.com.

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