Laser Air Assist Upgrade

The cuts with the laser can be greatly enhanced with air assist. This consists of basically blowing a compressed air stream out the nozzle below the lens. The laser comes with an air pump (glorified aquarium pump) but this is not enough. You need 30PSI for cutting and deeper engraving plus 5PSI for plastic engraving, metal marking and other cases where you don’t want the added cooling. With enough air pressure the quality of the engraving (lack of smoke condensate on the surface) and quality and depth of cut are greatly improved.

There are a number of plans / kits available for doing the upgrade. However, there is a common flaw: the air is always on. They all seem to be oriented to nearly continuous laser operation for production work as the low pressure air is left on all of the time. My work is not like that, with small numbers of pieces being made at a given time, more design, modifications, more cutting, etc. So, I wanted to have it set up so that the air would be switched on when the laser is cutting / moving, and the high / low pressure is controlled from the cutting parameters as set in Lightburn (the CAD/CAM program for the laser). I also do not like having a needle valve for the low pressure setting and prefer an air regulator. So with the new design, I have 2 low cost air regulators in series, with one for “high” and one for “low” and 2 air solenoids. One solenoid switches between high and low air pressure and the second one turns the air on and off with the laser motion / running status.

The laser controller for my OMtech AF3555 130 W laser is a Ruida 6442 and it has output connections for both Wind (high air), and Status (laser actively running). Per the Ruida manual, these are open collector (low active) outputs and are capable of 500 mA. So this should be enough to drive the solenoids (which are basically relays for air).

The air connections are made using 6mm polyurethane tubing and press in connectors. I wish I had found this stuff years ago. It is SO INCREDIBLY EASY to work with! An Upgrade for the Cool Mist on the Milling Machine was also made using the same parts. I ran out of tubing or the metal lathe and CNC router would have it too (future projects).

For some odd reason, the Ruida controller “Wind” output is disabled by default and must be enabled prior to use. To do this you need to go into: Lightburn -> Edit-> Machine Settings-> Factory settings and turn it on. At this point prior to making the change, it is also a good idea to backup the Ruida machine configuration via Lightburn if you have not already done so. The Status output is already enabled.

These 2 outputs are used to drive the solenoids. The “Status” output, which is active when a laser job is running is used with the second solenoid to turn the air on and off. This way the air is only flowing (and compressor running) when the laser is actively running. The “Wind” output drives the first solenoid and provides the selection between “high” pressure and “low pressure”. High is enabled by checking the Air Assist selection in LightBurn. The power for the solenoids comes from the +24V connection on the Ruida controller or directly from the 24V power supply. A diode is placed across each relay coil to snub the voltage spikes that are generated when the solenoid is turned off. The cathode (banded) end is connected to the +24v side of the coil. Make sure you get the orientation right or the output of the Ruida controller could be damaged. The solenoids draw approximately 200mA each, which is well within the 500mA rating of the outputs of this Ruida controller.

Air assist connections at the Ruida controller

A regulator is needed to drop the pressure from the compressor output (125-145PSI) down to the recommended 30 PSI for the high air assist setting. Rather than using a needle valve to set the “low pressure” flow, I added a second regulator that is set for ~5 PSI. Now I have good control for both air supply levels. The regulators are mounted on the wall near the laser. The fan control is also nearby as well.

High and low pressure regulators

The air lines lead down to push in compression bulkhead fittings on the back panel of the laser. I mounted these next to the water chiller connections.

Bulkhead air fittings on back of laser
Air Assist schematic
Sketch of the solenoid mounting board

The solenoids are mounted to a piece of acrylic (yes have the laser make its own parts). The wires are run through the wire chase in the cabinet to the controller and connected there to connector CN1. I chose red for +24v, green for Status and white for Wind. I had shielded cable on hand (left over from the CNC router) but the shielding is not necessary. The acrylic panel is mounted to the laser chassis with sheet metal screws. Sheet metal screws were used as there is no direct access behind that panel (2 layers of metal in that area).

The lightburn file for the solenoid mounting plate is:

Air assist solenoids
close up of the solenoids
Wiring the solenoid connector with diode across the terminals.
Keep the cathode (band) to the +24v

Parts:

Air regulators -1/4″ port – Tailonz https://amzn.to/3E1QYJM

24 v Solenoids – Tailonz https://amzn.to/3GMJts1

1/4″ pipe thread T connection (hardware store)

1/4″ short nipples (2x) (hardware store)

6mm air line kit – Tailonz https://amzn.to/3oXbIhx

6mm to 1/4″ straight fittings – Tailonz https://amzn.to/3oZgEmi

6mm to 1/4″ right angle fittings — Tailonz https://amzn.to/3oVVEwp

Diodes (1N4004, 1N4007 or equiv) (2x) – https://amzn.to/3yrV8te

6mm Bulkhead fittings – https://amzn.to/325hlkG

Note – Amazon links are referral fee paid