System

This is a CO2 laser system that cuts sheet metal. The laser and all optics are stationary. The beam is directed downwards on to the part that sits on a computer controlled platform which moves the piece in the x and y directions. Cutting is achived by passing the beam through a focusing lens inside of a cutting head nozzle. Oxygen is fed into the side of the chamber below the focusing lens. This gas exits the nozzle along with the beam and the laser beam/oxygen combination serves to vaporize the steel.

Many other systems are required in order to operate the laser. This block diagram [pdf|svg] gives a general idea of all the systems needed.

Front view of the laser cutter.

Construction

The electrical, mechanical and physical components of the DIY CO2 CNC laser include:

• Laser head and power supply
• Optics
• Computer, plus control system
• CNC table and power supply.
• Cooling

In addition to these systems, many of the components need to be physically supported. The area underneath the laser was non-flat and was originally composed of a concrete pad and brick. The brick was dug out, 2-by-4 form was built, and lot of rebar was welded into place. About 800 lbs of concrete was poured into the form.

The laser itself is supported with a angle iron frame, which was first designed in CAD and then fabricated.

The frame has outriggers that reduce swing from left to right of the support arm. Bolts extend off the outriggers and push against the wall creating a very rigid system.

At this stage a hole for ventilation was knocked into the wall. An angle iron platform was constructed and mounted to the floor to support the CNC table. Around this time a big plasma screen tv was installed on the back wall. The platform plus table was wired up.

Electrical

A total of 200 amps of power come into the house. The laser uses something like 80 amps of power, so to accomodate shop equipment, lighting and heating a 100amp subpanel was installed in the laser studio. It was useful to make a CAD drawing of all the conduit and boxes, and a subpanel was installed. Since there are a number of appliances that run on household current in order for the laser to run its crucial to have all of these systems run under computer control.

A 3 inch conduit was used to join to an appliance control box. The appliance control box housing is made from a recycled electrical panel that has been populated with six home made relay boxes; each relay box can handle switching 220v @ 20 amps output and are driven by 12vdc input. A three way switch on each box allows you to select On-Off-DC_control. Each relay box was made from steel cut by the laser. The 12vdc input is derived from another relay box - which connects to the parallel port of the computer. Again, it may be useful to refer to the block diagram to track how these components work together.

Ventilation

The laser produces fumes, vaporized metal and oxygen when it cuts so its important to have a good ventilation system to remove this material. A six inch hose runs underneath the CNC table, and another four inch hose connects to a plexiglas hood from above. Both hoses travel through the wall and lead to a y-section that join into a 10 inch hose, this 10 inch hose travels to a 2,500 CFM fan that exhausts through the ceiling in the roof. The fan has a speed regulator which I used to control sound level, but it turns out the fan can pretty much run at max speed without any problems.

Oxygen and air

Oxygen must be supplied to the cutting head at around 60 PSI to achieve cutting. Its also useful to have a small air pump run into the system - this is useful when you want to put positive pressure into the cutting head but you dont want to use oxygen. The air pump is controlled by the appliance control system and the air is run into a gang valve to manually choose between oxygen or air. The output of the gang valve is controlled by a solenoid mounted on the angle-iron support arm for the laser. The solenoid is controlled using the appliance control center. The solenoid dumps gas into a thin plastic tube that feeds into the laser cutting head.

Chiller

Cooling is provided by an old Neslab HX-100. The chiller lives in the basement and the water lines are transferred using pvc pipe the run across a disgusting wall, then up through to the laser area. The water is channeled through a water flow indicator and run into the back of the laser head.