Typically, engineers turn to direct acting proportional regulators to enable rapid system changes. A perfect fit for these is laser cutting machines where different gases must be controlled at both low and high pressures. During a laser cut, gas pressures and flows change depending on several factors and the machine must be able to react quickly or the quality of the cut will decrease.
An HMI displays the pressure settings of a connected Sentronic proportional regulator.
The most obvious place where proportional control is needed is the gas assist system. Without a stream of pressurized gas, laser cutters would only leave a line of glowing metal behind. The thickness and type of metal being cut dictates what assist gas is used but the process remains mostly the same. A powerful laser melts the metal which is blown out of the way by the assist gas. Thin metals can be cut with nonreactive gases such as Nitrogen, but thick sheets of steel require the addition of Oxygen. Oxygen causes a reaction with the laser-heated metal generating more heat and amplifying the laser’s cutting power.
Many times, when a part is being laser cut, it is the expectation that it won’t require finishing such as de-burring. In order to deliver parts with clean cuts and smooth finishes, tight gas regulation is key. This presents a problem for traditional on/off valves because they don’t allow for pressure changes on the fly. The amount of gas needed by the machine can change as the speed of the cut changes, which itself is a function of the geometry of the cut. If the pressure is too low, the cut won’t penetrate all the way and if the pressure is too high, the cut can come out jagged (especially when using Oxygen because that extra gas flow creates more heat on contact with the metal). Additionally, if the flow cannot be maintained consistently, the cut comes out with ridges.
The 614 Sentronic Plus offers complete pressure control with pressure ranges from as low as 1.5 PSI up to 725 PSI. Due to the direct acting mechanism inside the valve, it is responsive to the quick changes needed for clean cuts. Additionally, the 614 Sentronic Plus can be used in potentially explosive atmospheres according to ATEX 94/9/EC.
As advancements in electric linear drives and fiber optic lasers are made, high pressure valves will be critical to keeping up with the faster cutting allowed by these machines. Sometimes machines will still need to precisely control low-pressure, high-flow gases. In cases like these, a flow control valve such as the 607 Flowtronic D is a real problem solver. Low pressures, especially over wide orifices, can be tough to regulate and by closing the loop around flow instead of pressure it is possible to maintain the steady flow needed for good surface finishes.
Regardless of the product chosen, these regulators can be ordered for Oxygen service where necessary. Constructions for Oxygen service feature an NSF H-1 approved grease to ensure no additional hydrocarbons make it into the gas and foul the cut. Additionally, the onboard parameters of both the Sentronic and Flowtronic can be modified using software, as mentioned in the article on tuning proportional regulators. These parameters allow machine builders to get the exact performance they’re looking for and open the door to simplifying machine controls.
The post Gas Control for Laser Cutting appeared first on the Emerson Automation Experts blog.
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