CO2 Laser Cutter 40W With Arduino

This instructable is more or less a guide or inspiration to make a CO2 laser cutter out of materials you could have in your possesion allready.

I came up with the idea to make this laser cutter/engraver after I bought a new 3D printer, an Ender 3 pro, and had a Davinci pro on the shelf doing nothing because that was something he did the best. I spend more time to repair the thing then actually print with it, so I did'nt use him any more!

I realised that I have a bunch of parts and materials with this Davinci that I can use for something else. Here was the idea born to make a CO2 laser cutter/engraver.

In this instructable I will show you the problems I encountered and solutions for them.

Curious? See my video on Youtube!

Video of working cutter on Youtube

If you deside to build a laser cutter in general and a CO2 laser cutter in special you have to consider that you must take precautions to not hurt yourself or others with direct or reflected laser light. Where the light of a diode laser is mostly visible, that of a CO2 laser isn't! Furthermore the power of a CO2 laser is much higher. After this build you come in the adjusting period, then you have to work with an unshielded laser beam in order to line up and direct the beam to the right spot.

NEVER, EVER DO THIS WITHOUT SAFETY GOGGLES! USE GOGGLES WHO ARE DESIGNED TO BLOCK THIS TYPE LASER LIGHT, 10.6 µm!

Where laser light, direct or even reflected, in the visible spectrum can destroy your retina, the laser light of a CO2 laser can destroy your cornea. That is not very pleasant!

So please be very very carefull and allway be aware of what you are doing!

One other thing to be aware of is the power supply needed to drive a CO2 laser tube. These power supplies can kill you! The one for this build wich can drive a 40W tube, has an output voltage between 15 and 25kV! Even if the machine is switched off, you have to wait a while before handling the HV-cables, because it takes some time fort the power supply to fully discharge! Wait at least an hour and then test it with an isolated srewdriver with the metal part connected to earth!

The power supply and the HV cable going to the laser tube must be shielded with grounded shielding. Further on in this instructable you can see how I did this!

The toxic fumes coming from the lasered materials has to be discharged to outside your home or building. You can do that with a motorised air vent and hose, trough a window or wall, or, as I did, with a hose connected to a central mechanical air exhaust system of my home.

And to make all the misery complete: DON'T LET THIS MACHINE WORK UNATTENDED! I mean really don't! Do not leave the room while the cutter is cutting or engaving! It can catch fire! And allways keep something at hand to distinguish a starting fire instantly!

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In this build I have as safety precautions: a 5mm thick polycarbonate window to safely look trough at the working laser, a emergengy kill switch wich totally disconect all the mains power lines, a normal and a key switch to switch the HV on or off and microswitches on doors to switch off HV when opening, thus the normal and key switch has to be in the on position and all doors has to be closed to let the laser work!

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If you are new with laser cutters/engravers it is advisable to read more of this topics on the internet, specially the CO2 types where you can familiarise yourself with the do's and dont's!

Well if this all isn't discouraging you and you build a thing like this, you will be rewarded with a great tool to make beautifull things!

But first of all: BE SAFE!

Besides the old 3D printer I had, wat was good for: two steppers, a power supply, axels, a led strip, wire, switches and a load of torx screws, I needed a laser tube, a laser power supply, mirror/lens set, an air pump, a water pump, a water container, silicon tubing, enough mdf material to make the cabinet, a sheet of polycarbonate and thin aluminium plate. And off course an Arduino with a CNC shield! I already owned most of it

Tools:

You need a 3D printer, a saw, screw drivers, a caliper etc. And to make things a lot easier: a Dupont connector set, to make your own cables.

At first I demolished the old 3D printer and on the 1st picture you see the flipped over x,y- running gear. From this part I have taken away the original guiding parts for the axles (black) and print my own (orange). The new parts I printed are tailor made to house the mirror/lens set (gold colored) I have bought.

On pic 2 you see the whole test contraption with in the back the laser tube and water cooling. On the right the controls for the whole thing. Most of the things were nano-taped to the table. It looks messy but it works!

After knowing that it works I began to design corner stands to make the cutting area bigger then the print area of the davinci frame (grey metal thing).

Pic 1: the whole ground plate (85x60 cm) where I drawn where the side plates and laser compartment will come. You also see some printed parts (white and orange).

Pic 2: looking if things fit!

Pic 3 and 4: Laser compartment with high voltage safety shielding

Pic 5: here on the aluminium shielding shall the LPS (laser Power Supply) will be mounted

Pic 6: every aluminium HV shielding plate has to be connected to each other

******************** PLEASE PAY ATTENTION**************************

The grounded shielding on the HV side is very important to be save in case there is something going wrong with the laser tube, the LPS or a loose HV cable!

On this pic you see the cabinet with some round holes and square holes. The most left round hole is the exhaust air hole, the round hole in the back plate is the hole were the laser beam comes trough, the round hole on the right and the narrow square hole on the right in the back are air intake holes. The air comes in via the narrow square hole, goes through the electronics compartment, cooles the electronics and comes via the right round hole in the cutting area where it takes the smoke and warm air trough the left round hole to te outside.

The other square hole is were the mains lead and switch are connected as well as e 5V outlet for the cooling water thermometer and the air assist tube is coming in.

You can see here also the extended x-axle distance: I sawed the axles in half and connected them with long printed bushes. It works but they were to wobly and further on I have replaced them with steel ones.

This is the power supply extracted from the Davinci. I have placed some terminals to make the power connections to all the electronics and motors.

pic 1: electronics. On the left of the Arduino with CNC shield, you see a green board. This is an adaptor board I made for the end-switches and the logic invertor. The adaptor is needed because I use end-switches with a status led wich uses three leads in stead of two (one extra 5V for the led), the CNC-shield uses two-lead connections.

Pic 2: An overview of the whole in this stage. Mechanics and electronics are working. The little red plastic squares are printed cable mounts for use with tie-wraps, nano-taped to the cabinet.

Pic 3: electronics compartment closed, the square hole is for the control panel, the kill switch is mounted.

Pic 1: A temporary control panel

Pic 2: Control panel wired

Checking of the laser tube lines up right. Here you also see the shielding that will be connected to ground via the mains plug.

In my other instructable: "DIY 3D Printed Laser Engraver With Approx. 38x29cm Engraving Area", you can find a way to setup your Arduino with GRBL! Look for step 12, Software!

The programs I did use then are not entirely the ones I use now. I don't use the JTP laser tool anymore.

LaserGRBL I use sometimes now, but mainly I use Lightburn! Lightburn is the program you want. You can try out this great program for free!

I have added the config.h file, were I have made all nesessery changes, to download. You can exchange the existing one (in the GRBL directory) for this one. Don't forget to make back ups of your files first!

One problem I encountered during the investigation for this build on how to let the CO2 laser fire at wil. Because the Arduino has a positive TTL output signal, and the LPU needs a negative TTL signal to fire the laser. The solution I found was a logic inverter! This does the trick!

Pic 1: the logic inverter circuit.

• The left yelow and black wires are TTL output wires coming from the CNC shield
• The rigth yelow and black wires are the inverted signal wires going to the LPU (JP3 on pic 3)
• The LED with the ballast resistance, R5, are not necessary. I add them because I like to see what is going on.

Pic 2: Two different transistors you can use for the circuit. Watch the difference in pin lay-out

Pic 3: The LPU I use is the one with the 4,6,4 connector config. On JP3 you see the inverted signal lines going in.

When the laser fires it disturbs the end switches and the machine stops in an error state, probably due to a high voltage puls. I did not manage to shield the leads to the end switches. I did, however, made a work around:

• on pic 1 the G-code settings I use, where homing is disabled
• on pic 2 a homing macro

What it does is, when starting up Lightburn the homing function does not work because $21 and $22 are both 0!

I use the macro to home the machine. What the macro does is:

1. switch on the homing cycle: values of $21 and $22 to 1 (now the machine is sensitive for HV pulses, but that's ok because the laser will not fire during the folowing homing cycle)
2. homing the machine: $H
3. switch off the homing cycle: values of $21 and $22 back to 0 (now HV pulses have no effect)

This works great. You can only use the homing macro for homing. You have to do this whenever it is not clear if the machine knows how the axis are situated, for instance if you move the axis by hand. You can move the axis by hand because in the G-code settings I have turn the motor power off ($1) when idle to get rid of an anoying high pitch sound!

So, if you turn on the machine and Lightburn (or an other cutting program), first of all use the homing macro! After that you can use the other "back to origin" button to go back to the home position provided that, in the mean time, the cradle is'nt moved by other means than the motors! In that case use the macro!

This is the complete block diagram.

The Fritzing file is added to download to see more detail!

Where the line up of a diode laser is literally straight foreward, for a CO2 laser it is'nt. It is really important that the laser beam goes through the middle of the focussing lens and then straight through the air assist hole. If not, you end up with skewed results. Therefore it is evident to line up the laser as good as possible in the center of all mirrors. When desinging your contraption make shure you can shift the mirror holders, vertically or horizontally, or both, depending on the situation!

On different photo's in this instructable you see the mirror/lens set (gold colored) I have used.

On the internet you can find plenty of tutorials to line up your laser!

On the picture you see a dummy CO2 laser I printed. It is a red diode laser in a printed housing with the same diameter of the actual laser tube. If you put this dummy in the aft laser holder and make sure the beam goes to the middle of the second laser holder you can align the mirrors and lens at forehand.

This adjustment shall not be accurate enough, due to internal differences, after swapping the tube with the dummy, but it makes a lot of difference allready!

A laser tube has to be cooled! Period!

You must cool the tube oherwise the lifespan shortens dramaticly! And when the tube temperature goes up the output power goes down.

I use a container of approx. 6 litres and an Amzdeal model HY-304 water pump. In this container, besides the water, I put one of the two water bottles I keep in the freezer until I need one of them, to chill the water.

Use only demineralised water.

Make shure you know the water is running, by sight (what I do) or use a flow sensor.

On the photo you see the container with on the bottom the pump and the ice bottle floating on top of it. On the left you see the thermometer to check the cooling water temperature.

The fumes coming from the burned material could be toxic or at least bad for your health. So you must make sure the fumes are disposed to outside the building or home you are at. Fumes also blocks the laser beam and makes it less efficient.

You can do this with a motorised air vent or, as I did, using the mechanical air extraction of my home.

These are pics of the machine in final stage. Notice the front panels are mounted in this case with loose hinges and magnets. You can, of course, use normal hinges.

Pic 1: One of the first things I made was a new panel. This combination of engraving and cutting turns out very nice!

Pic 2 and 3: A little notes holder

Pic 4 and 5: some drawers

Pic 6: Cutting and engraving acrillic with nice results.

Pic 7: Anodised aluminium test, the bright colored ones are done with the CO2 laser, the brownish ones with a diode laser engraver! With the CO2 the anodising faporise totally!

Google "boxes.py" and you can enter a website where you can make online a cutting plan for several box type's.

With "jigsaw draradech" (github) you have a nice online jigsaw generator