COST ANALYSIS IN LASER CUTTING
Take Time to Crunch the Numbers: The initial investment, cost of overhead, electrical and assist gas, and the total time required to manufacture the product are all influential factors in determining which laser source is right for you and your business. Here’s why.
When determining the cost of producing a part on a laser machine, there are many variables to consider. The most obvious factor is the machine itself. Of all the options available to users of laser cutting systems, it basically comes down to two unique and distinct resonator technologies: CO2 and solid-state.
In a CO2 laser, the gain medium (the substance in which laser light is produced and amplified) is carbon dioxide. When this gas is consumed, it must be replenished. Solid-state lasers are considerably more diverse with regards to the gain medium. These lasers always use a crystalline base, doped with a rare earth element as the active material.
For laser cutting, the gain mediums are generally Nd:YAG (neodymium:yttrium aluminum garnite) or Yb:YAG (ytterbium: yttrium aluminum garnite). These materials are not consumed by the laser during operation, which is one reason a solid-state laser system could potentially cost less to operate. Considering these technologies at the surface level, there are really two very tangible advantages that operating a solid-state system has over CO2:
(1) speed in thin gauge applications, and (2) lower cost of operation.
Both of these results are easily and attractively put to paper, but when the sleeves are rolled up and the shovel meets the sod, the true cost shows itself. Since solid-state lasers cut faster in thinner materials and are less expensive to operate, it’s easy to assume that the actual part cost will be less than with a CO2 laser – but that’s not always the case.
When determining the real cost to produce a part, it’s important to look beyond simple productivity. In fact, there are five factors that should be taken into consideration when determining the actual cost associated with cutting a part or product on a laser machine.
The first two are the investment cost and the total cost of overhead. The investment cost refers to the total amount spent on the equipment being used to produce a part: the total cost of the laser cutting system, including nominal uptime, hours of operation per year and the expected duration for ROI (return on investment). Basic maintenance requirements, including normal consumable items (e.g., nozzles, lenses and mirrors, if applicable) are also factored in.
In this alone, the solid-state system has a considerable advantage. The resonator is comprised of components that typically do not have to be replaced, but if they do it is generally less frequent (e.g., pump source diodes). Although you may save money here, it should be noted that solid-state laser systems also generally come with a higher price tag.
The second factor, the total overhead cost, is the amount of money required to keep the company open and the lights glowing. The biggest factor here is labor cost, which tends to be a constant regardless of the resonator technology. Since these values typically do not to fluctuate, we must look to the final three considerations for more tangible cost differentials: cost of electrical, cost of assist gas, and the total time required to manufacture the product.
Solid-state lasers are more energy efficient than their CO2 counterparts. With wall plug efficiencies upwards of 30 percent, solid-state lasers require less energy to generate the same amount of power at the cutting head. Though these systems are undoubtedly more efficient, this statistic can be somewhat misleading because electrical consumption makes up a relatively small portion of the overall cost, especially in locations where energy is relatively cheap.
Depending upon the application, the assist gas may account for a large portion of the overall laser cutting expense. When cutting with oxygen as an assist gas, the consumption rates of both the solid-state and CO2 technologies are comparable, but so is the performance.
With a solid-state laser, appreciable increases in speed are only seen with nitrogen cutting. Because of this, it does not always make sense to pay a premium for solid-state laser technology when oxygen will be used as the assist gas for the majority of work in the shop.
When cutting thin material, the solid-state laser can achieve higher speeds thanks to the excellent surface coupling potential of the one-micron beam. However, the kerf width is generally smaller, and when combined with the increased cutting speed in thin materials, a greater amount of nitrogen is needed to eject the molten metal from the kerf during nitrogen cutting operations. Given the price of nitrogen, this can be a costly consideration.
As the run time disparity between the CO2 and solid-state laser begins to diminish, nitrogen consumption can push the seemingly less expensive solid-state laser past the CO2 as the more expensive machine to operate, even though the solid-state laser is still a bit faster. This is one example where convention is defied, but it is not an isolated case and is often repeated.
Also worth noting is that the overall edge quality suffers when cutting with solid-state laser sources. Also, considering that the solid-state laser speed advantage is lost as the material thickness increases (relative to laser power), the appropriateness of either technology is wholly dependent upon the application.
When deciding on a laser source, there is no obvious answer. The initial investment, cost of overhead, electrical and assist gas, and the total time required to manufacture the product are all influential factors. It is important and worthwhile to be diligent in cost analysis when determining which laser source is right for you and your business.
Take some time. Crutch the numbers. You’ll be happy you did!
About the Author: Brett Thompson is a sales engineer in the Laser Product Group of TRUMPF Inc., Farmington Industrial Park, Farmington, CT 06032, 860-255-6112, Fax: 860-255-6424, email@example.com, www.us.trumpf.com.