Flow rate calculation for laser cutting nozzles

[Adam Bryan]

TL;DR

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!

 

[Lnewqban]

Welcome, Adam!

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

Please, see:
https://thermalprocessing.com/optimizing-gas-supply-for-industrial-lasers/

 

[Adam Bryan]

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

 

[jrmichler]

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.