Air assist GBRL

Hardware
#1

Hi, I need some advice here. I have a NANO based GBRL controller on my home built and want to hook up a relay for air assist. I believe it uses the M8 command, but what pin does that output to? Is it pulled down to ground on activation or up to 5V. I have a solid state relay that takes 3 - 32 volts on the input, so I should be able to connect directly to the pin. Any info greatly appreciated.
https://www.amazon.co.uk/gp/product/B07HT2BCKN/ref=ppx_yo_dt_b_asin_title_o00_s00?ie=UTF8&psc=1
Relay I have.

Cheers

David

#2

After more searching I found this thread that seems to have the answer I need. And the relay Oz recommends is the one I have so hopefully all will be fine.
I have read that the A3 output is active high with M8, is that correct?

Cheers

David

#3

Use the Console tab and just type in M8 or M9 to turn On/Off the output. This will tell you which polarity is correct.

#4

Hi, just wanted to say that my auto switching air assist works like a charm. A3 output is High on activation for anybody that needs to know. If using Start from current position, then the assist comes on exactly as the laser starts to cut and if there is any lag in the pump it may be a problem. A pity there isn’t a small delay?? Using absolute coords it comes on before it gets to the start of the cut so is fine.

Cheers

David

1 Like
#5

Just a thought…have you considered turning on the air, and putting a short delay in your start gcode?

#6

I hadn’t thought of that, but if it could be done on a global / default basis it would be worth doing. Not sure if that is possible or not. I wouldn’t want to have to edit each program before sending.

Cheers

David

#7

Edit>Device Settings - then under the Gcode tab. You can enter start and end Gcode to add to every file there.

#8

But how would I add the delay after the M8 command? This option says it will add it to the beginning?
I guess I need:
G4 P5 or such to add a 5 sec delay. But it needs to be after the existing header and the M8 line:
; LightBurn 0.9.20
; GRBL device profile, current position
; Bounds: X-156.11 Y-62.71 to X156.11 Y62.71
G00 G17 G40 G21 G54
G91
M4
; Cut @ 500 mm/min, 100% power
M8
G0X-17.71Z34
…
Cheers

David

#9

It will add it at the beginning, I was just thinking you could just set the M8 and a pause to get your pump started, then just run the file as normal. Your file would call for the M8 again, but your pump should already be on, so no harm done. or your file could call an M9 to turn air off

Not saying this is the optimal way to do it, but it was just a thought for a workaround.

#10

That makes sense and I can’t see any reason it wouldn’t work. I’ll give that a go tomorrow. Thanks for the tip.

Cheers

David

#11

That worked just fine thanks. In fact I switched off the air assist option in layer control and added Gcode to the start and end so that I can not only delay the job starting, but hold the extraction/air assist on for 20 seconds after the job finishes. Works great.

Cheers

David

#12

Slight update to this. It didn’t actually work with the air assist turned off in the layer. I thought I had turned it off but it wasn’t. With air assist turned off the Gcode has a few M9 scattered around and these turned off the pump just after the start of the job. So it was on for the 5sec delay then it went off. I now have turned on in layers, but added another M8 in the ending statement that gives me a 10 second delay before turning off. There is an M9 in the original gcode just before I turn it on again, but the pump doesn’t have time to react. Not sure why these extra M9s are in the code, but maybe Oz can answer that?
So my start code is:
M08
G4 P5
And the end code is now:
M08
G4 P10
M09

now it does what I want.

Cheers

David

#13

Maybe not pretty, but it works and I’m glad you got what you want in the end. Thanks for reporting your findings.

#14

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