Flow rate calculation for laser cutting nozzles

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Adam Bryan
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Trying to calculate required gas flow through a given nozzle....
I am in need to calculate the required gas flow for a given nozzle orifice. In laser cutting we use various "nozzle orifice sizes" to cut different materials. For example, when cutting 1/4" mild steel we would use a 5mm orifice nozzle using 20 bar. I would like to make a calculator in excel that you just plug in the nozzle orifice size and pressure required. The calculator would then tell you the flow rate in SCFM or SCFH and the minimum pressure that is required to maintain this flow and pressure.

Any help would be awesome! thank you!
 
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  • #3
Lnewqban said:
Welcome, Adam!

Shouldn't that information come from the manufacturer of the nozzle?

Please, see:
https://thermalprocessing.com/optimizing-gas-supply-for-industrial-lasers/
Unfortunately the sales process gets involved and the end users are given numbers that are not real. I happen to work at one of the Mfg's and our calculations all come up incorrect. We recently purchased a flow meter and are going to run real time tests as to what the flow rates really are per nozzle type and orifice diameter. I am searching for someone who has the equations to calculate flow rate through a given nozzle.

Adam
 
  • #4
If the air flow path is "large" compared to the nozzle orifice diameter, and there are minimal obstructions to air flow in that supply path, then you should be able to use an online orifice flow calculator. Unfortunately, to fully explain the previous sentence takes a full course in fluid dynamics.

The problem is that orifice flow calculators take as input the air pressure at the orifice, and that pressure is always lower than the pressure from the pressure regulator. How much lower can be calculated for simple flow paths, but you really need that course in fluid dynamics to be able to do it right.

Your flow meter should be able to give you the flow rates that you are looking for. Just be advised that you need to measure the flow using the exact air supply system from a real machine. The flow through a particular nozzle is a function of the nozzle diameter, nozzle internal shape, and the tubing and any valves from the pressure regulator to the nozzle.
 

FAQ: Flow rate calculation for laser cutting nozzles

What is flow rate in the context of laser cutting nozzles?

Flow rate in the context of laser cutting nozzles refers to the volume of assist gas that passes through the nozzle per unit of time. It is typically measured in liters per minute (L/min) or cubic feet per minute (CFM). The flow rate is crucial for ensuring efficient cutting, as it helps to remove molten material and prevent oxidation.

How do I calculate the required flow rate for a specific material and thickness?

To calculate the required flow rate for a specific material and thickness, you need to consider several factors, including the type of assist gas (oxygen, nitrogen, or air), the material being cut, and its thickness. Manufacturers often provide charts or tables with recommended flow rates for different materials and thicknesses. Alternatively, you can use empirical formulas or consult with the laser cutting equipment's manual for precise calculations.

What factors influence the flow rate in laser cutting?

Several factors influence the flow rate in laser cutting, including the type of assist gas, the nozzle design, the material being cut, the thickness of the material, the laser power, and the cutting speed. The nozzle diameter and pressure settings also play a significant role in determining the optimal flow rate.

Why is it important to have the correct flow rate in laser cutting?

Having the correct flow rate is essential for achieving high-quality cuts and efficient operation. An incorrect flow rate can lead to poor cut quality, increased dross formation, excessive oxidation, and even damage to the material or the laser cutting equipment. Proper flow rate ensures clean cuts, minimizes waste, and extends the lifespan of the nozzle and other components.

How can I adjust the flow rate on my laser cutting machine?

To adjust the flow rate on your laser cutting machine, you typically need to modify the gas pressure settings and possibly change the nozzle size. Most laser cutting machines have a control panel or software interface where you can set the desired gas pressure. Consult the machine's manual for specific instructions on adjusting the flow rate, and always perform test cuts to verify the settings before proceeding with production runs.

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