K40 Laser Cutter Modifications: Air Assist, Laser Pointer, Laser Tube Thermal Protection

This is the Instructable for the video I put on YouTube and is to give more detail around the Arduino units within the project. I have assumed a base level of knowledge about Arduinos, but I'm happy to answer further questions regarding the project. Hopefully in combination with the video, this should be doable by most people.

There are two Arduino circuits within this project; one that allows the user to turn on/off a laser pointer and air assist, and another circuit that protects the laser tube from overheating and monitors flow in the cooling pipes.

Laser Aim and Air Assist

1. Arduino Nano
2. Relay Module (KY-019)
3. 5V 650nm 5mW Red Dot Diode Laser Head, 2 of these
4. Momentary Switches, 2 of these
5. 1k Resistors, 2 of these
6. Various colours of wire (optional) one colour is fine too

Laser Tube Thermal Protection

1. Arduino Nano
2. Relay Module (KY-019), 2 of these
3. Temperature sensor (DS18B20)
4. Hall Effect flowmeter
5. I2C LCD 16 x 2
6. 4.7K Resistor
7. Speaker (optional)

Here is the diagram and code for the air assist and laser pointer. The air assist blows air across the laser's cutting path, helping clear smoke which would interfere with the laser, helping you get a neater finish. This supplements the general exhaust fan. The laser pointers enable you to trace the working area before cutting and when the two lasers are lined up with each other, you know that the work piece is at the correct height.

Once you have wired up this diagram and uploaded the code, you then need to power the board. I did this by using the 5v supply found on my PSU for the laser cutter. This means the board turns on when the laser cutter is turned on.

The attached svg file is the bracket for the laser diodes and the air assist lines. The reason for the three size is that I didn't know what would fit my laser head and so they are scaled to 100%, 103% and 105%. I ended up using the 105% scaled version.

Although the diagram uses laser diode modules, I only had the diode but I need a place holder for the diagram and this was as close as I could get.

The mains supply of the air assist pump is connected to the relay and must be unplugged when doing this, as there is a risk of electrocution.

Here is the diagram and code for the thermal protection for the laser tube. This ensures that there is sufficient coolant flow and that the coolant is cold enough. If these requirements are not met, then the laser will not be able to fire. The detailed version to fit this to the machine is in the video but the abridged version is to hot glue it in and to cut a hole for the screen, also held in with hot glue.

As with the previous module, it is also wired into the 5v supply on the laser cutter's PSU.

The wire running through the relays must be wired in series otherwise only one requirement would need to be met to allow the laser to turn on. I used the wire from the micro switch on the door but any other cable that controls the tube coming on could be used.

There is a speaker in the diagram and code, however this does not need to be connected. I was planning on using this as an alarm if either of the relays were off. However, it is surprisingly irritating - which is the point - but I only run the laser under full supervision and actually decided that I don't need it at this time.