Introduction: DIY 40W CO2 CNC Laser

About: Just do things, electronics, woodwork, etc.

Hello! How do you do? This is project How To Do, and my name is Konstantin. Some time ago I was siting, counting my millions from YouTube, listening to cnc router noise, and decided to move on. I realized that I need a cnc Laser, but not a simple one, I need a powerful CO2 laser!

Step 1: Why CO2 CNC Are So Expansive?

I started to look on aliexpress, cheapest I found is about 400 dollars, for that price you'll get working aria of 300 by 200mm, and it looks funny, my 3d printer has larger table. Than I notice something interesting, for all additional 10cm of working aria, you will pay about 100 dollars. Just to make it clear let me explain how this type of CNC machines works, we have an rectangle aluminum frame, guides are installed on both sides parallel to each other, and a crossbar with a guide. laser tube is attached somewhere here on the machine body, beam shoots from this side, reflected from first mirror , shoots to a second mirror, then to third one, from the last one it go to focusing lens and burn the material, pretty simple, right? I think so, especially considering that the design does not require such special rigidity as let's say milling cnc, there are a small mirror and a lens are wound from side to side and not a 20kg piece of steel. And now I have a question for you, why the cost of the machine will differ significantly depending on the working aria? It's because the demand for a bigger working aria is much higher. The cost of components changes slightly, aluminum profile cost about 10 dollars per meter, even if you take the rail guides, it will cost about 40 dollars per meter, and if you assemble it with the rubber rollers, there will be no increase in the cost of construction, all other components remain the same, the same mirrors, the same motors, the same laser. All this leads to the idea that if you have a minimum skill working with hands.. sounds weird.. then it makes sense to assemble the machine by yourself, and not to overpay couple thousands.

Step 2: Foreword

So what is needed for this entertainment? Most of the items were bought in China and there is a complete list with links , for example were purchased, guides, nuts, motors, lenses, mirrors, power supplies, a laser, a cooling pump. It makes sense to buy an aluminum profile at the local store. It is pretty heavy and shipping will be expensive. And also you can buy some little things in the nearest home depot. I printed all fasteners for motors, electronics, belts, lenses and other things on a 3D printer with a PETG filament, there were doubts that all this could work fine and provide good accuracy, but after a couple of months the work it's ok, even such a thing as a nozzle through which the laser passes the beam work fine. Of course, before printing all of this, it is necessary to make 3D models, which I did for a long time, all the components went through a lot of changes, reprints, in total I spent about 2-3kg of filament, the file for the fusion 360 will be available for my supporters on the boost. It’s clear that probably noone will repeat an exact copy of my creation, but at least you can look at and kind of touch all the components, you can modify something. It’s impossible to make a guide for assembling a cnc machine for the specific tasks of each, so I’ll tell you how I assembled my own with a description of the pros and cons of the selected solutions.

Step 3: Mechanics

I estimated the working aria that I needed, stopped at a size of 800 by 700 mm, took an aluminum profile of 20 by 40mm as a frame, its rigidity is enough, but for larger devices it will be necessary to choose a more solid profile. I highly do not recommend inventing something of your own, you can certainly make a frame of some metal from the garbage dump, or with plywood, but come on, aluminum profile costs 10$ per meter. In my case, it took 2 sticks of 840 mm, 2 of 700 mm and one of 800 mm, to connect the profile using special angles and nuts. Next, we determine what type of guides we will use, I took the rails, this is the most expensive option, the pros: are practically unbreakable, there are no backlashes, the most smooth movement. The cons: respectively, the price and a great chance that the Chinese will send you garbage that will work very badly and you just throw them away, in the list of all components you will find a link to the guides that I took, despite the low price they are very good and I have no complaints, although I do not exclude the option that I could just get lucky. Still not a bad option for this type of machine is ordinary rubberized rollers, as is often used on 3D printers, it is very cheap, easy to maintain and replace, and nevertheless gives sufficient quality. As already mentioned 90% of the mechanics were printed on a 3D printer, the filling is 100%, I recommend to buy if you don't have 0.8mm nozzle so that printing goes faster. To answer to classic comments about the fact that not everyone has a 3d printer, I want to say it is quite possible to make all components without a printer just with a hand tool, I just don’t see the point of doing so, printers are very cheap now, for example, you can look at the review of my review of the CR-10, which printed all the components. 3D printer is a great tool that everyone should have, and do not forget about the various services that provide 3D printing on order. Here, the Y-axis stepper motor is mounted on the rear of the frame, in order to push the axis at the same time from two sides, I put the regular 8mm threaded rod on the bearings, I put pulleys to rod's ends that pull the belt and the Y axis itself, on the front there is a mount for the pulley with a bearing. In this situation, the axis skew is impossible. The X axis doesn’t seem to cause difficulties, the motor on the one hand, a pulley with a bearing on the other, in the middle a laser head with a belt clip. All mounts for mirrors are made for 20mm and have adjustment, between their base and mount itself I put cropped springs from gel pens, for ease of adjustment.

Step 4: Laser Head

Let’s stop on the head a bit, I've been thinking for a long time how to do it correctly and stopped on this design, it consists of 5 parts, the top is attached to the bearing and has a through hole for the passage of the laser beam inside, a mirror is installed at an angle of 45 degrees, there is a tube it screwed with 4 screws, another tube is a little bit bigger and it squeezed on the previous one, there are holes for fixing bolts, but in practice the tubes are rubbed tightly against each other and it works without bolts. The very last part is the nozzle, on top of it we put the o-ring and the focusing lens is also 20 mm in diameter, the tube from air pump comes in the side, this whole structure is attached to the base with 2 rubber bands, its bottom is solid, this is done specially so that when you turn on the laser for the first time it burned its way out and formed a minimum hole through which the compressor air would exit. It seems like everything of mechanics, lets move on to electronics.

Step 5: Electronics

The brain of this machine is a controller that will send commands to stepper motors, move the axis and turn on the laser at the right time, I would recommend buying controller from China, spend 200 bucks on a real thing, very fast, with display, and a slot for a memory card. But as always there is an alternative way, GRBL, in fact it is a great platform and it works just fine, but with some reservations, we are not using a weak laser diode, but a freaking 40W CO2 tube that you can cut off your finger, so if we engraving on wood or acrylic we will find out such a thing that when you try to increase the speed more than about 5000 mm per minute, the laser does not go faster, at the beginning of the work it seemed to me good enough. Of course, after engraving with a 3D printer with a maximum speed of 400mm per minute. But now this is a real limitation, engraving takes the longest time and you can reduce it by slightly increasing power and significantly increasing speed. That happens because the arduino nano on which my controller is assembled is simply not able to process more data, this is its physical limit. However, there seems to be a solution, there are grbl options for Arduino Mega2560 boards, for ESP32 and STM32f103, in the future I’ll do a separate video about controllers, just know that arduino nano is 8bit controller but on 32-bit systems you can increase the speed up to 4 times, which is comparable to industrial boards, there are also options with displays and memory cards. In any case, in addition to the brain, you will need drivers for stepper motors, I used TMC2208, I thought that I would use 256 microsteps and I would make 10000 lines per 1 mm, but as you can see the controller just can't handle it and I recommend you to do not overpay and buy the classics A4988 and everything will be fine. Stepper motors are simple nema17 with a 5mm shaft. I feed motors with a voltage of 24v with such an power supply, it also feeds a water pump. My system has a separate 12v 400w power supply, it was supposed to be for the cooling system on the Peltier modules, but it didn't work well, maybe I will continue experiments later, at the moment this unit powers the air pump to blow the working surface. I will also leave a link to a similar compressor for 110 or 220v. If you chose to assemble controller on grbl, like me, then everything is as simple as possible, google Arduino nano grbl and solder everything according to the circuit, there are literally ten wires, connection to the laser power supply looks like this. It is important to install grounding on the machine, it does not matter which board you choose, it is extremely important, otherwise various artifacts will creep out in the form of missing steps, freezes and other things.

Step 6: Laser

Then we move to the laser, here I chose a 40-watt tube, I ordered it from aliexpress, delivered pretty fast and everything was fine, so do not be afraid to order, after some time, I would probably take a more powerful tube, probably 80w, this will allow you to cut plywood up to 10mm, and maybe thicker, with a 40W laser you can cut materials in the about of 4mm, then you have to lower the speed and increase the power, which will negatively affect the life of the tube. But of course it depends on your goals. A very important point, the laser tube needs to be cooled at its operating temperature in about of 17 degrees Celsius, less is good - even power will increase, but if temperature rise above 17 degrees Celsius it will damage your laser or shorten the life time of it. I use a 800 l per min Chinese water pump for cooling, which I certainly don’t believe, but a fact that it works fine and it's silent. It is recommended to use distilled water as a coolant, I use an anti-freeze, the option is so-so, many people criticize it, but in the garage in the winter the temperatures drop far below 0 and the laser would just burst with ice. In the winter, everything was simple with cooling, but summer is coming, and I’ll have to figure something out, I recommend buying chiller system CW3000 will be enough for 80w laser, there are also few options, chiller for a beer, used one cost starts from 100$, the second option is reassembled air conditioner. I will make another video about it. The laser is powered by a high voltage of thousands of volts, you have to be very careful when working with. I advise you to simply buy a power supply for your laser from China, its cost around 40 bucks. Also, additional, I bought a 30 mA ammeter and connected it between of the high-voltage power supply and laser tube to see what was happening on it.

Step 7: Assembly

Next is the assembly, I started it with an aluminum frame, made sure that the angles are 90 degrees, hung the rails, and all the printed parts according to the 3D model. The x-axis is fastened with 30 mm m6 bolts, I made the thread in the profile. I made a box of 10mm plywood, not the best option, but I tried as chip as possible, the most important task is to place the laser tube and all the mirrors on one line, go to this stage carefully, as you later get stuck with the setup. I carefully mount the aluminum frame on the printed brackets. On the top I put a polycarbonate sheet, laser ray can't pass this material, so you shouldn't be afraid to stare at it through the lid. I install the electronics, stretch the wires, connect.

Step 8: Adjustments

And now the most entertaining process, in quotes, turn off the block with the wire going to the low-voltage part of the high-voltage power supply, apply voltage to it and to the water pump for cooling, hook a piece of masking tape to the place where the first mirror should be installed, and push the test button on the laser power supply board, now moving the tube, try to get the moment that the beam hits exactly in the center, when this happens, set the mirror in its place using double-sided tape, move to the second mirror, this time you should hit in the mirror's center in full range of axis movement, if this does not work, it's because the mirrors and the laser tube are not at the same high, you should fix it and than continue. Fix the second mirror, now get hit in the center of head, in the four corners of the machine and in the center of the working aria, the last mirror shoots down, I put the regular mirror below so that the tape can be seen and on the maximum extended nozzle I get hit in the center, it sounds like a pain in a butt, but in fact, I dealt with this in a couple of hours, you have to do it only once. The last element of the optical system is the lens, it come in different focal lengths from 38.1mm to 101.6mm, if you imagine how the beam goes, than you can understand the difference of usage, lenses with a short focus are mainly used for engraving, and long focus for cutting because the area of the beam with a high concentration will be larger and the material can be burned deeper. To begin with, I recommend taking 50.8mm you can engrave and cut with it. The lens needs to be cooled, for this purpose air is supplied from the air pump to the nozzle, at the same time it blows to the working surface and cooling the lens. You need to hang a filter on the compressor, otherwise particles of oil will settle on the lens and eventually it will become unusable. By the way, all the actions that I just described must necessarily occur in safety goggles for 10600 nm, this is the wavelength of this laser, also remember the fact that the laser is invisible to the human eye.

Step 9: Final

After adjustment, I reconnect the high-voltage board, adjust the steps per millimeter in grbl for each axis, set the gap from the nozzle to the cutting surface and you can run the program! I also want to go through the points that can be improved, as I said about controller, I ordered several different boards, I will test them and show everything on this topic. lens mounts, I certainly did an excellent job, but the mounts that you can buy will be better, so if you can spend extra 50$, buy good ones. The machine requires ventilation of the working surface, I bought such a 20-watt fan and, as it were, it pulls absolutely nothing, you need a powerful turbine. Another point, you'll probably need a honeycomb table , putting materials on some garbage lain around isn't the best idea. Let's summarize, 342$ were spent on parts from Ali at the, lets add a 100$ for stuff I bought locally, a plywood sheet, a fan, an aluminum profile, bolts, nuts and all this, a total of 450$ for assembling a machine with a working aria of 700 by 800mm, let's see what the Chinese industry will offer, let's say such a model with a field of 1000mm by 600mm, but there’s a 100W tube, well, let's subtract 400 bucks, the cw3000 is extra 200, any way 2000$ against 450$ on my build. I hope you can understand my explanation, and someone wants to repeat this project. Thanks for watching/reading, see you very soon!

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