Those air nozzles work, you just have to work out which length you need. I printed all 4 and after the Neje arrived and I had worked out the focus needed, put in the appropriate one. The nozzle runs about 5 - 8mm off the material for my first cut with the trusty Fishtank pump rattling around on the bench. I saw someone suspend theirs with some surgical tubing, so going to try and find some to try that to cut the noise down a bit.
I am only really interested at this stage in using the Neje to cut wood, not too worried about etching just yet.
For what it is worth, I have managed to fumble my way around and come up with the following nuggets by a process of trial and error.
When my Neje 40W arrived, the first thing I did (after putting on the laser glasses) was to take a 2" (50mm) block of wood and a slat of wood then ran a 100mm straight line down the Y axis while holding the test button on the laser. Once finished I looked at where the best line quality was and measured it from the base of the laser to that point on the slat. The best distance for me was in the range of 47.5 - 49mm. so I now have a block cut to exactly 48.5mm which I use to set up the height before a cut. I cut a test box of 3mm masonite/hardboard and it cut through at 120mm/min at 80%, well chuffed with that result. My 5.5watt I never managed to get it to cut anything except old records.
I am using a fish tank pump for air assist and printed the nozzle in PETG and so far it has performed perfectly.
One problem that a lot of new users miss, myself included, it is ESSENTIAL that the material being cut is NOT flat on the bed. You HAVE to suspend it on something for the laser to be able to cut right through. I use a piece of flat mesh grill which I picked up as an off cut at my steel supplier. I see other users (David) using heat sinks, and others even metal spikes and other methods. It must be metal though else it is one use.
I did however find that the Gcode from Lightburn does not seem to run at 100% efficiency when converted to gcode and taken to the MPCNC via SD Card. The test button cuts a lot better than gcode at 100% so i am assuming there is a setting somewhere in Marlin that is not set up to suit the software. I am using Ramps set up with M105/6 from the fan pin with the Primo software. I am thinking I may explore GRBL as part of my journey with a proper GRBL control card that is set up exclusively for laser.
Hope something in that helps others in working out how to get this amazing laser to work properly.
Another laser question for you all – I bought a honeycomb grid to cut my lite ply on and that all works great but it’s only .5 inch thick and I have it sitting on top of mdf. When I cut I get large amounts of smoke and when all said and done the mdf is burnt up quite a bit. I am curious to know if rather than sitting the grid on MDF what if I sat it on a piece of metal …I.e. and aluminum tray or something like that to help reduce the burnt wood to only the wood I am cutting. I am not sure if a reflective material would then cause issues with the underside of the wood being cut. I can certainly put the grid on some stand offs to move the grid an inch or two above the tray. Just curious what others think… maybe a stupid dangerous idea.
I missed your post a month ago. You might consider enabling laser support in the Marlin firmware. Internally, Marlin does some compensation that would not be done using fan pins. I outline the 7 lines in configuration_adv.h that need to be changed in this post. Then change Lightburn to use inline commands when generating g-code.
In the lower left corner of the picture is an extension with a 1.5 inch hose connection I intend to get a fan to extract the air from the plenum. You can faintly see the support blocks under the HC. I will cover the top of the blocks with some foil to prevent the laser from scorching them.
I must be blind… I am not seeing a tube in lower left. I do see the support block in the middle. Would be curious to know what CFM blower would be needed to evacuate. How much smoke do you get?
I have to open my garage door and I have a 30" industrial fan and run that next to my CNC and yet my garage still smells of burnt wood which is most likely all coming from the MDF. if I get rid of that it will only be from the lite ply .
These lasers are the wrong wavelength to cut most semi clear plastics. I’m using florescent light grid under my parts I’m cutting. The laser will sometimes sear the top of the plastic, but it never cuts more than a mm.
Most of the energy is being lost in the material you’re cutting. By the time the laser exits the other side, there’s not enough energy to cut much.
I disagree David - How are you clearing the smoke etc? A Metal grid is almost essential for a through cut. Having the surface you are cutting flat on another surface must be affecting the efficiency of the cut.
My experience with cutting through has never worked properly until I started suspending the material off the bed.
I have just brought 4 large aluminium heatsinks and used with the fins up supporting the material being cut. Cutting 3mm board, and a fan to clear the smoke from underneath.
There is still loads of laser power to cut into the waste board underneath even after cutting through the 3mm board. I agree with you that clear & light coloured plastic does not cut, or even mark much so you have given me an idea of what to put the heatsinks on to protect the waste board from burning which has been a problem. I have some white perspex left over from the jukebox build which will be perfect for that.
I missed your post a month ago. You might consider enabling laser support in the Marlin firmware. Internally, Marlin does some compensation that would not be done using fan pins. I outline the 7 lines in configuration_adv.h that need to be changed in this post. Then change Lightburn to use inline commands when generating g-code.
Thanks for the tip Robert, I will certainly give it a try.
Another laser question for you all – I bought a honeycomb grid to cut my lite ply on and that all works great but it’s only .5 inch thick and I have it sitting on top of mdf. When I cut I get large amounts of smoke and when all said and done the mdf is burnt up quite a bit. I am curious to know if rather than sitting the grid on MDF what if I sat it on a piece of metal …I.e. and aluminum tray or something like that to help reduce the burnt wood to only the wood I am cutting. I am not sure if a reflective material would then cause issues with the underside of the wood being cut. I can certainly put the grid on some stand offs to move the grid an inch or two above the tray. Just curious what others think… maybe a stupid dangerous idea.
The use of translucent perspex appeals to me as a solution for this Chris, and David gave me the idea from his post, as the laser does not cut through translucent or light coloured perspex. Place a piece under your grid to absorb the remaining laser after it has cut through.
I am going to try this weekend by standing my aluminium heatsink ribs on top of the translucent sheet so the smoke etc can still get through but the residual laser does not burn the waste board.
I wonder how thick of material and given in my case I would only have access to some plexi I am not sure if that would work or not. At best I think I can get 1/4" but it will be expensive.
I wonder how thick of material and given in my case I would only have access to some plexi I am not sure if that would work or not. At best I think I can get 1/4" but it will be expensive.
I tried to cut some 3mm translucent. It barely made a mark. A really subtle image can be seem if you look carefully but it is almost invisible, so 1/4’ should be more than enough.
Even some scrap or off cut will work, most cutting using the laser is fairly small so you probably don’t even need a whole square meter. - I looked at our local builders supply and I can buy a square meter for about R110 ($5)
I have the air assist nozzle pointing down. But I also have a small desk fan that blows over the top of my laser. Most of the time when I’m using the laser I have shop doors open, so the fan blows any smoke out to the middle of the shop where the breeze flowing through it carries it out the door.
I did recently buy a 12" industrial exhaust fan for a paint booth I’m setting up. It has a flexible exhaust that you can run up to 20’ away. I’m thinking I can also use this fan in the winter to pull air past the laser and send it out a window. Probably overkill, but I’m a ‘use what you have’ kinda guy.
The exhaust fan is here. It’s expensive, but I bought it for other reasons and only recently realized it would work for the laser as well
