Flow rate calculation for laser cutting nozzles

  • Context: Undergrad 
  • Thread starter Thread starter Adam Bryan
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    Gas flow
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Discussion Overview

The discussion revolves around calculating the required gas flow for laser cutting nozzles, focusing on how different nozzle orifice sizes affect flow rates and the necessary pressure to maintain those rates. Participants explore the feasibility of creating a calculator to determine flow rates in SCFM or SCFH based on nozzle size and pressure.

Discussion Character

  • Technical explanation
  • Debate/contested
  • Experimental/applied

Main Points Raised

  • One participant seeks assistance in developing an Excel calculator for gas flow rates based on nozzle orifice size and pressure.
  • Another participant suggests that flow rate information should ideally come from the nozzle manufacturer, but expresses skepticism about the accuracy of the data provided to end users.
  • A participant mentions that their company is conducting real-time tests with a flow meter to determine actual flow rates for different nozzle types and orifice diameters.
  • It is noted that orifice flow calculators require the air pressure at the orifice, which is typically lower than the pressure from the regulator, and that understanding this requires knowledge of fluid dynamics.
  • Participants emphasize the importance of measuring flow rates using the actual air supply system from a real machine, as flow is influenced by various factors including nozzle diameter and internal shape.

Areas of Agreement / Disagreement

Participants express differing views on the reliability of manufacturer data and the necessity of fluid dynamics knowledge for accurate calculations. There is no consensus on a single method for calculating flow rates or the best source of information.

Contextual Notes

Limitations include potential inaccuracies in manufacturer-provided data, the need for specific conditions in flow calculations, and the dependency on the actual setup used for measurements.

Adam Bryan
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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!
 
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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
 
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.
 

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