Laser Hardware

The laser cutter is a cart-mounted appliance. While the laser cutter is cart-mounted, it should not be considered mobile. It has power and exhaust connections that do provide some mobility, but are not designed for continuous movement. The wooden cart holds the necessary auxiliary equipment, as well as supports the laser cutter. For parts information, see Laser Parts.

Auxiliary Equipment

The important auxiliary equipment is identified in the following image.

Monitor and Computer

This hardware runs LinuxCNC and provides direct control of the laser cutter, as detailed in other parts of the class. The wireless mouse and keyboard are associated with the LinuxCNC computer. This computer is the main interface to be used when running the laser cutter.

Water Pump

The laser tube itself generates enough heat that it can overheat and crack, which would cause a total failure of the laser. It is water cooled to prevent overheating. The cooling works by using an immersion pump contained in the 5 gallon bucket beneath the cart. The bucket holds a reservoir of water that will work as a heat sink during laser operation. There are limits to the amount of cooling the reservoir can provide, and it is currently not known what sort of duty cycle the laser is capable of without causing issues of over heating.

To prevent failure of the laser tube due to loss of cooling water, a flow switch is installed in the cooling water lines. The laser is incapable of firing when the flow sensor does not detect flow through the cooling lines. If it has been some time since the laser has last been used, it can take approximately 10 seconds of the pump operating before the flow switch will register flow. The flow switch is part of the arming system, which is described below. If at any time a water leak is detected, shut down the laser cutter immediately, provide signage to warn of the danger, and notify the Laser Cutting SME ASAP. The laser power supply reaches voltages of up to 25,000 Volts. It is extremely dangerous, and any amount of water is grounds for immediately stopping and powering down the laser.

The water pump is enabled by the main laser power switch located on the rear panel of the laser cutter.

Air Pump

The air pump is mounted to the bottom shelf of the cart. The air pump provides a constant stream of clean compressed air to the nozzle of the laser cutter. The compressed air is important for two reasons. First, the constant stream of compressed air blows out of the nozzle, which helps prevent smoke from the material being cut (burned) by the laser from depositing on the lens that focuses the laser. Because all of the laser power goes through that lens, anything that collects on the lens can cause it to quickly overheat and shatter. Second, the compressed air provides a constant stream of air that provides a significant amount of fire suppression while cutting. The air stream blows out most material fires before they get larger.

The air pump should run at all times when the laser cutter is running. The air pump is not tied to the arming loop, but the compressor makes enough noise that it is obvious that it is running.

The air pump is enabled by the main laser power switch located on the rear panel of the laser cutter.

Exhaust System

Any time the laser cutter is running, the exhaust system should be enabled. Cutting with a laser cutter makes smoke and other fumes that are at best unpleasant, and at worst hazardous to your health. The exhaust fan controls are currently located on the wall next to the white board. Turn the exhaust fan on high when operating the laser cutter. If you notice a strong smell of burning when operating the laser cutter, check to ensure that the exhaust vent is securely attached to the rear panel of the laser cutter.

Fire Suppression

In the event of a fire in the laser cutter, the first step is to hit the E-Stop button to shut off the laser and prevent any further fires. There are two forms of fire suppression located on the laser cutter cart. The first is a squirt bottle filled with water. It can be used to extinguish small fires that catch on materials. It can also be used to dampen materials before cutting to help minimize chances of a fire. The fire extinguisher can be used to extinguish larger fires. The extinguisher is rated for use with electronics, and should not damage the laser. The fire extinguisher must be replaced or recharged after every use. If the fire extinguisher is necessary, you should completely discharge the contents to ensure than any fire is put out.

Back Panel

The back panel on the laser cutter itself is located on the right side near the bottom (beneath the monitor). The panel contains a power switch. The switch provides power to the laser cutter itself, as well as the air pump and water pump. All three are energized when the switch is on. The LinuxCNC computer and monitor are always powered, so that the files are always accessible.

Front Panel

The front panel has several important controls that change the operation of the laser, as well as status indicators that indicate appropriate operation.

Power Indicator

The green LED labled "POWER" illuminates any time the power switch on the rear of the laser cutter is enabled.

Arming Switch

The arming switch is used as a tool to allow the user to ensure that the laser cutter will or will not fire. At all times when the laser is not actively cutting, you should keep the arming switch closed so that the laser is not armed. It is a covered switch. To arm the laser, you need to open the cover, then lift the switch. Closing the cover will push the switch to the disarm position. This switch has a safety purpose, as well as functional utility. In the Great Experiment, Jondale discovered that if the laser is armed and the LinuxCNC computer reboots, the laser can fire due to the boot process powering the computer. The arming switch was added to prevent this from happening by providing at least one item that enables the laser that is off by default.

The functional use of the arming laser is that it enables testing G-Code without firing the laser. By running a program on the laser cutter with the laser disarmed, all of the movements will be executed, but the laser will not fire. This can be used to ensure that the program will work with your material to be cut.

Emergency Stop

The emergency stop switch disables the laser. It is a normally closed switch meaning that by default it enables arming the laser. In the event of a fire or other emergency, press the emergency stop button to stop the laser from firing. Once the emergency stop switch has been pressed, it remains open until reset. To reset the E-stop button, twist the knob in the direction indicated by the arrows. That will close the switch, and will arm the laser once again.

Armed Indicator

The arming system includes the emergency stop, and arming switch as listed above. Additionally, there is a safety switch on the lid that prevents the laser from firing any time the lid on the laser is open. This is intended to reduce the chances of anyone being exposed to the laser beam. The flow switch on the cooling water is also connected to the arming system. If the switch does not detect flow of cooling water, the laser will not arm.

Only once all the safeties are in the correct position will the laser be able to fire. When that is the case, the red LED will illuminate, indicated that the laser is armed and will fire.

Manual/Auto Toggle

LinuxCNC has the ability to automatically control the laser power. It can be used to vary the power from full power, which can cut through wood and plastic, down to a beam so weak that it will not mark paper. When the Manual/Auto toggle switch is in the automatic position, the LinuxCNC will take laser power information directly from the G-Code. In almost all cases, this will be the recommended setting. However, the laser power can be manually adjusted by moving the switch to the manual position.

It is strongly encouraged to ensure that the laser is in automatic mode every time you use it. If the laser cutter is in manual mode, it will not respond to G-Code commands to vary the laser power, which can result in poor performance, or damage to your material. If at any time you operate the laser cutter in manual mode, please return it to automatic mode when finished to help prevent issues when the next operator tries to use the laser cutter.

Manual Current Control

When the toggle switch is in the manual position, the manual current control will vary the laser power. The control has been internally limited to prevent an over-current condition of the laser.

Current Indicator

The ammeter indicates the current passing through the laser. The maximum laser current is 15mA. Both the manual controls, as well as the automatic controls have been internally limited to prevent laser over-current. The current meter provide definite indication that the laser is firing.

Test Fire Button

The test fire button can be used to manually fire the laser. In manual mode, the laser will use the setting for laser current based on the current control knob. In automatic mode, it will use the last value of laser power from the previous G-Code program, meaning that it is unpredictable if are not aware of exactly what laser power was used most recently. This button is mostly for diagnostics, and is not useful during normal operation of the laser.