Glad the Neje was simple to hook up. 7 mm/s (420 mm/min) is pretty fast to be trying to cut 6mm – nearly 1/4" – plywood in reasonably few passes… also without air assist. Did it flare up on you as you cut?
Also what distance did you focus at? The A40640 module seems factory set up for about 22mm from the bottom of the housing… and all of mine have been close to that. I set up the nozzle to extend about 15mm below the housing IIRC so there should be 5mm to 7mm between nozzle and material when focused on the surface. I personally have my best results when focused on the surface… not halfway thru the material like so many suggest. If you focused to ~3mm below surface… your gap between nozzle and material was decreased by that amount. And if there was a lot of fire and smoke when you ran it, with the nozzle that close and no air flowing through it, I suspect a lot of smoke and soot entered the nozzle and possibly coated your lens… as well as any burning action on the surface being close enough to possibly melt the end of the nozzle. I’d recommend taking the nozzle off until you get air-assist set up. I always keep a tiny amount of positive pressure in the nozzle with the air assist to keep smoke and soot from entering the nozzle, to protect the lens when engraving. I recently had a laser module which seemed to be losing power… and a Q-tip and isopropyl alcohol applied to the lens did wonders to restore the power.
For reference, I usually run 100 - 180 mm/min and 100% power to cut 3.2mm (1/8") plywood in one pass, focused at the surface.
I have to second David’s sentiments about running without air flowing using the air assist nozzle and having the material flare up. I printing my nozzle in ASA. I was cutting some black poster board with air assist running, when the air line got tangled and pulled out of the nozzle assembly. The whole cut was only 6 minutes, but I turned around to see a burning nozzle. When I got everything clean up, I noticed the laser lens was cracked. It took a couple of weeks to receive a replacement lens out of China.
I know others on this forum have printed the air assist nozzle out of PLA, so I’m guessing your melting was due to a lack of air flowing, not the material.
I uses the little board with the LCD on it. I like to turn the laser on the lowest setting to line up on the part. The second setting on the board puts it in ttl mode for the controller to work.
LightBurn has a focus test under the Tools menu. David (dkj4linux) takes his laser off, sets it on a flat surface point at a wall, then moves it forward and back to obtain the best focus and reads the distance on a ruler. A third method is to place a piece of wood at an angle (like a ramp) and burn a line down the ramp. You need to record the starting and ending heights. You can then walk your way along the line from each end and interpolate the focus distance.
As for XY, this will depend on your authoring software. I setup LightBurn so that it works like by router jobs where the starting position is (0,0,0).
In regards to the x,y - I have my laser on my CNC and never start from the home position. So I am wondering does a person just turn the laser on at low power and then position it where you want and then zero it out? I guess I was not sure how “spot on” it would be if at low power. I have not tried it so not sure.
The laser at low power will be spot on. There are many ways to setup a job. Even though I have dual endstops, typically I just position my machine manually at the origin with the laser and MPCNC control board off. The air assist nozzle hangs down low enough that I have a good idea of where it will start cutting (within a few mm). Typically, there is enough stock that I can afford to waste a few mm, and move a few mm away from the edges.
If my stock is really tight and I need better precision, I have two g-code files on my SD card…blink.gcode and scan.gcode. Blink.gcode blinks the laser on and off 5 times at PWM power 1 (0.4%). I use this file to verify my origin position. Scan.gcode turns the laser on at PWM power 1, and then moves the laser 300mm along the X axis, and then returns to the origin. I use scan.gcode to verify that the stock is square with the machine. Someday I’ll move these g-code files to my pendant or alternately add them to the V1 custom menu.
Another approach that works well for repeated operations on “blanks” of the same size is to first use the laser to cut an outline in cardboard, then you can drop the blank into the hole in the cardboard and be assured that the origin and rotation is correct.
I always start my machine at y-0 (to keep things square) but x-wherever. I usually just manually jog to where I have the stock set up,dial in the z height manually with a metric ruler, and check the laser position at low power.
Hey I remember someone recently posted about their remix for the dkj4linux Neje nozzle that uses a 1/4 QD to connect the hose. You might be interested in that… think it’s on TV.
Right now the Neje shop has the laser available from the USA warehouse. The $30 coupon is still valid, but the lens is only from China. I just ordered mine… yeehaw!
What do you guys do for fume extraction? I have it set up in my garage but its single digit outside so not all that great for having the garage door open and too smoke laden to run it for a long time.
Curious to know of any DIY or low cost fume extractors.
I use that carbon filter with a reductor and a 150mm air extractor i had in stock for years:
I use it as output for air extraction where it should more commonly used as input but results are good enough, less fume and less fume smells.
I haven’t make a decent mount yet, i do my best to just place the extraction hose outside my primo frame the nearest i can to the stock i burn, most challenge is to keep it in place.
I have plans to make a mdf and plexiglass enclosure and fix it on top, need more time to do it.
My K-40 has a 4" outlet with an inline blower that tees into my whole-house air exchanger exhaust to get vented outside without wasting too much heat. It’s a short run, maybe 4 feet total. I’ve seen articles where folks use bouncy-house blowers to move the exhaust from their laser enclosure.
Be aware that lots of fans do a better job pulling air than pushing it through a long tube. It might make more sense to have the fan closer to the outlet than to the enclosure if the run distance is significant.
I still need to rig up an exhaust for my laser. I just open a window and the door on the opposite side of the shop and let the cross breeze blow it out.
I ended up ordering a grow fan blower, 4" flexible duct, a Powertec Gulp Dust Hood and an exterior wall vent. I am not sure about punching a hole through the side of my house for this. May try to vent it out the only window and a temp solution.
One question if any of you guys know… I am trying to looking up and find something that I can attach the hose/dust hood too that would be positionable - I thought there were things like like that for welding, etc but I have no idea where those things are called. Basically something that you mount and then attach the item you want to position and you can move it around to the position you want and then lock it in.
