Increase delay between end of graving and stop of the air assist to protect the lens?

My laser is locked in a box with smoke evacuation. When the engraving is finished, the laser and therefore the air assistance, cuts off after a few seconds. The time is not enough for all the smoke to be evacuated. In order to protect the lens, I would like the delay between the end of the engraving and the stop of the laser to be longer. Is it possible to add a gcode to extend the operating time of the laser? (my laser is a grbl one)

I think it would be much easier to use a time delay relay. Then you don’t have to mess with the setup.
In general, air assistance is not meant for fume extraction, did you misuse the function for this case?

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You could creat a new device with Custom GCode and input your delay before the M9, also.( no need to delete current device)

Hello air assistance have several advantages. One of them is to prevent the fumes to touch the lens.
So it’s for me a good idea to have air assist on until all fumes are evacuated from the enclosure.

Thank you. I’ll try

I actually do this for the exact reason cited by @Zifnab69 , to let the fumes/smoke clear for 30 seconds after a job. However, I’m using GRBL device, not Custom GCode. I suspect other devices have the same ability as GRBL, which is to have some custom gcode run at Start and End of job.
In device settings, see the Gcode tab, and in the End Gcode list add
M8 – or your air on code
G04 P30 – the delay time, 30 seconds in this case
M9 – or your air off code

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As far as I am aware, but I can be corrected, Creality firmware does not allow access to Fans and or Air Assist by Gcode Commands.

So the M7/M8 and M9 are not really doing the job is all based on a ON/OFF state in the controller(Motherboard)


Ah, then I misunderstood, maybe. The air assist protects the lens while lasering. But I don’t see any sense in letting the air assist itself running after the job has ended (in contrast to letting the fume extraction running, I thought you were talking about that). Though I don’t know how your setup looks like. My lasers have a nozzle with a very minimal opening and since it’s kind of a closed chamber, the chances are more or less zero that any dirt might enter after the job has entered. Additionally, I don’t have many fumes in my housing anyhow since I have a strong extraction fan on one side and inlet fans on the other side that create a strong airflow along the workspace to clear any fumes as soon as they emerge. Maybe you can enhance airflow there as well.

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