Laser cutting is a technology that uses a high-powered laser to cut through material. Unlike older machines, which use drills to cut, the laser cutter uses a continuous beam to slice through material.
It also uses a lens to focus the laser beam into a very small spot, called the kerf. This kerf is a fraction of an inch wide for most materials, and varies based on the material thickness.
Sublimation, a process that transforms materials from their solid to gaseous state without changing them into liquid, has been used as a method of sample purification in analytical testing. This is useful for removing unwanted components from samples before analysis, such as ammonium halides and arsenic(III) oxide, for example.
The sublimation process involves the application of heat and pressure to a dye solid that has embedded in a transfer medium and been printed on with a special printer. This dye is then transferred to an object or garment, typically polyester, and the image will be absorbed into the fabric.
As a result, the printed images on the sublimation print transfer are fully integrated into the fabric and cannot be removed or destroyed by washing. This makes it a very flexible and low-cost printing technique.
When a laser beam is focused into a small spot of high intensity, it begins to melt the material. This occurs with wood, carbon and thermoset plastics.
In some laser cutting systems, a stream of gas is released from the coaxial nozzle in order to accelerate the melting process. The gas can be inert nitrogen or argon for thermoplastics and inert oxygen for metals.
The resulting gas pressure blows the molten material away from the cut surface, allowing it to be ejected as droplets. This method of cutting is used to reduce heat affected zones (HAZs) and minimize material distortion.
Laser cutting is a powerful tool in many applications, but some materials are difficult or impossible to cut. For these materials, the use of alternative technologies such as flame cutters may be recommended instead of laser cutting.
Thermal Stress Fractures
Laser cutting involves the removal of small bits of material to create a hole or cut. There are four main methods used in this process: sublimating, melting, reacting, and thermal stress fracturing.
Fracture-controlled laser cutting is a special type of laser cutting that utilizes thermal stress fracture to separate materials without using vaporization or melting. This technique was developed to specifically cut brittle materials such as glass and ceramics.
The cutting process is performed with a CO2 laser that heats the surface of the material, causing it to fracture. This allows for the separation of hard brittle materials like ceramics and glass at a much lower energy cost than other methods.
Assist gases are used to remove molten material from a workpiece during laser cutting. They can be nonreactive or reactive depending on the type of metal being cut.
The gas flows into the kerf in the form of jets. This is done to transfer momentum from the assist gas to the molten material. When the gas is flowing into a kerf, a boundary layer is formed to keep the flow laminar.
In most cases, the boundary layer will detach from the kerf when the pressure of the assist gas exceeds a critical value (Reg > Reg,crit). This is the point at which the flow becomes turbulent and produces the formation of dross on the bottom of the cutting edge.
A variety of studies have been conducted to improve the cut quality during laser cutting of molten aluminum and copper alloys by modifying the behavior of assist gas jets in the kerf. One of these studies showed that the nozzle diameter was a crucial parameter during laser cutting.