Laser Cutter Exhaust Redesign

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This page is intended to address concerns about the current state of exhaust plumbing attached the 3 functioning laser cutters, establish a road map to solve the existing problems, provide a reference for others working on this project, and once the project is complete, document the capabilities of the system. If you see any information that needs correcting or should be here but isn't, please fix it.

begin brain dump


Bumblebee and Wolverine have been in service for about a year with exhaust piping that has been generally accepted as "good enough once we get the leaks covered up with duct tape." The actual flow rates have not been characterized, however.

Measurements and Models

Exhaust pressures have been measured at various locations with some makeshift tools: a Magnehelic with a range of 0 to 2 in. water and a Honeywell electronic differential gauge with a range of -4 to 4 in. water (calibrated against the Magnehelic).

Pressure measurements in inches water -- shutter valves to both lasers open
Ambient 0
Y fitting between lasers 0.62
Blower intake 2.4

Using these numbers to converge the Darcy-Weisbach equation, it is estimated that the 60' of flexible duct in place is capable of removing 12 CFM of air from the laser cutter area. Considering that the recommended rating for lasers that side is about 500 CFM, I consider this unacceptable. Replacing the entire system with 6" smooth galvanized pipe should, in theory, remove at least double this amount, 8" pipe should increase the flow to 36 CFM, and 10" pipe should get us around 58 CFM using the existing blower. It seems clear that a more powerful blower will be required to draw the recommended amount of air through this length of pipe. Bounce house blowers look like an affordable route since for about $150, a sufficiently powerful blower is available which also happens to be weather-sealed, enabling the motor to be mounted outdoors (except maybe winter) and considerably reducing the noise level in the shop area.

2014: System in place with 12" ductwork (6" T and adapter with flex hose to each machine, may need investigation) and McMaster-Carr blower rated for 1900CFM. Measurements not taken, but smoke bombs cannot keep up with ventilation system.

Full Spectrum Laser

Flow models have not yet been run, but there is a design awaiting budget approval.

2014: Said system of 6" galvanised spiral steel ductwork in place, with McMaster-Carr inline blower. Theoretical airflow for machine is ~250CFM, Magnehelic gauge reports approximately 0.75" water column with machine closed.