Achieving Greater Productivity with Modern Laser Cutting Systems

THICK PLATE PROCESSING TECHNOLOGIES
The latest innovations in plate processing reduce piercing times and heat input, and eliminate the accumulated material slag from the top surface. These new technologies pierce materials as much as 80 percent faster than conventional pulse piercing while still maintaining the small pierce through and minimal heat input from pulse piercing.

One new technology is multi-step pulse piercing, where the initial pulse pierce is designed to break through the surface and then ramp to a second, more intense, pulse parameter. During the second step, optical sensors monitor the piercing and dynamically change the intensity of the parameter in order to achieve the fastest pierce through. Once the pierce through is detected, the machine can begin to cut immediately thereafter, without waiting for a pierce time to expire.

Minimizing the heat input helps keep the plate cooling more effective, which is critical to maintaining the integrity of the features. Eliminating the material slag accumulation that is generated from continuous wave piercing is another advantage of this high-speed pulse piercing technique. Accumulated slag on the surface of the plate can interfere with the cutting process due to incorrect height sensing caused by the accumulated material.

Overall processing times shorten because the optical sensors used to monitor when the pierce through has actually occurred also initiate the cutting process. Other piercing techniques typically wait until a period of time expires before the machine can start the cutting process, which leads to non-value added time. Plate processing in “lights-out” mode is greatly enhanced with this type of piercing method because of the low heat input and cleanliness of the plate during cutting.

BENEFITS OF AUTOMATION
Automation is the single largest contributor to the throughput efficiency of a laser cutting system. It creates consistency during the load/unload cycles, does not fatigue, does not take breaks and works during shift changes and unmanned shifts. When material storage towers are integrated through automation, laser cutting systems benefit further by having the specified material ready for cutting without waiting for a fork truck to load new skids of material. The only time these advanced systems are idle is during the short 30 seconds or so needed to change tables and begin cutting the next sheet. These systems can typically operate unmanned or, at the very least, one technician operates several laser cells.

Inefficiencies really add up without automation. A stand-alone machine with one table requires the manual unloading of finished parts from the table, then manual loading of a new sheet onto the table before the system is cutting again. From the end of one sheet until the beginning cut of the next sheet could waste 10 to 15 minutes! Because these manual systems run at about 40 percent operating efficiency, they are actually not working most of the time.

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Adding a secondary table for unloading and preparing the next sheet while the first table is cutting can increase that operating efficiency by 30 percent, to a total of 70 percent. This eliminates a major portion of the down time associated with single-table systems. Automating the load/unload process eliminates the fatigue variable, along with the break and shift change variables. Usually another 10 percent increase in efficiency (to a total of 80 percent) is gained here just through consistency from shift to shift and day to day operations. Increased labor efficiency is also realized as operators are able to operate multiple machines.

The most efficient throughput comes from adding a material storage tower directly to a load/unload cell to eliminate the material waiting variable that occurs with standard load/unload systems. The materials are made ready in the tower with no lag times in changing over from one material type to the next. These advanced systems can also run unattended on off-shifts or on weekends without interruption to further increase the overall throughput.

Advanced systems usually operate within a 90 percent efficiency range and are typically interrupted only for a short 30 seconds or so for material table changes. If we consider one 8-hour shift with a sheet cut time of 9.5 min, we can process 48 sheets during this time period by taking shuttle times into consideration with a full load/unload and material storage system. Without the automated material storage, a 10 percent reduction in efficiency will process only 43.2 sheets. Without the material storage and automated load/unload, a 20 percent reduction in efficiency will process only 38.4 sheets. Without any material automation and without a secondary table, a 50 percent reduction in efficiency will process only 24 sheets in that same 8-hour period.

Recent machine improvements also eliminate the need for an operator to change nozzles, center the nozzles or change lenses. All of these tasks can now be automated by the machine, which chooses the correct nozzle and lens to use depending on the material being cut. This greatly increases the quality and the speed of cut for each material because the optimum nozzle and lens combination reduces consumable cost and speed inefficiencies.

Adding automation not only increases throughput efficiency but also adds laser time capacity that did not exist before. Rather than adding a second stand-alone single table machine (which would only bring the throughput efficiency to 80 percent capacity), adding the full automation to the single machine with dual tables elevates the throughput efficiency up to 90 percent. Further savings can be realized by storing the material vertically rather than taking up valuable production floor space laterally as we see in some shops.

Modern laser cutting systems address the inefficiencies of older laser cutting systems and offer much higher competitive value and throughput than older systems on the market today: the same 4 kW laser cutting machine of five years ago cannot compare to a new full-featured 4 kW laser cutting system offered today. Faster automation is available to keep pace with the higher throughput of the modern laser cutting machine. Adding full automation enables manufacturers to take advantage of off shifts and weekend operations to meet the demands of their customers.