What is a laser cutting machine? How does laser cutting work?

As the name implies, laser cutters create patterns and designs by cutting through materials. A powerful laser beam is the source that melts, burns, or vaporizes the material.

Essentially, laser cutting is a manufacturing process that uses a thin, focused laser beam to cut and etch materials into custom designs, patterns, and shapes specified by the designer. This non-contact, heat-based manufacturing process is well suited for a wide range of materials, including wood, glass, paper, metal, plastic, and gemstones. It is also capable of producing complex parts without the need for custom-designed tooling.

Background

The invention of the laser cutter is attributed to Kumar Patel, who began his research into the action of lasers when he joined Bell Labs in 1961. In 1963, he developed the first CO2 laser, a variant that has more modern applications than any other type. CO2 lasers are used to engrave materials from acrylic and plywood to cardboard and MDF.

Applications

Today, laser cutting has found a foothold in industries such as electronics, medicine, aerospace, automotive and semiconductors. One of the most common applications is cutting metals 鈥?whether tungsten, steel, aluminum, brass or nickel 鈥?because lasers provide clean cuts and smooth surfaces. Lasers are also used to cut ceramics, silicon and other non-metals.

Perhaps one of the most interesting uses of laser cutting technology is in surgery, where laser beams are now replacing scalpels and are being used to vaporize human tissue. This is particularly useful in high-precision surgical procedures such as eye surgery.

We will discuss more applications in later sections, but for now, let's see how the laser cutting process works.

What is a laser cutting machine?

How Laser Cutting Works

Laser cutting machines typically have a beam diameter between 0.1 and 0.3 mm and a power between 1 and 3 kW. This power needs to be adjusted depending on the material being cut and its thickness. For example, to cut reflective materials such as aluminum, you might need up to 6 kW of laser power.

Laser cutting is not suitable for metals such as aluminum and copper alloys because they have excellent heat conduction and light reflection properties, which means they require powerful lasers.

Here are some of the core components of a laser cutting machine:

Laser resonator: The laser beam is emitted from the laser resonator, which is a sealed glass tube with two mirrors facing each other. The tube is filled with CO 2 and other gases such as hydrogen, nitrogen and helium. The mixture of these gases is activated by a diode or an electric discharge that emits energy in the form of light.

Cutting head: The light is reflected in all directions with the help of multiple mirrors that are carefully arranged to ensure that it reaches the laser cutting head. Once the beam reaches the cutting head, it passes through a curved lens and is magnified and focused to a point. It is within this cutting head that the laser is turned into a thin, focused beam that does the cutting or rastering. The focused laser beam passes through a nozzle before hitting the plate, through which compressed gas such as nitrogen or oxygen also flows. If you are cutting aluminum or stainless steel, for example, the laser beam will melt the material before the high-pressure nitrogen blows the molten metal out of the cut. Typically, the cutting head is connected to a mechanical system driven by a chain or belt, which enables it to make precise movements over a limited area. The focal point of the lens needs to be on the surface of the material being cut for the laser to actually make the cut.

Nozzle Distance: At all times, an exact distance is maintained between the plate and the nozzle. This space is critical because it determines the focus. Typically, changing the focus will affect the quality of the clip. Several other variables can affect the quality of the cut, including beam intensity and speed.

Three major varieties of laser cutting

Flame/Reaction Rutting: The assist gas is oxygen, which is blown into the cut at high pressure (up to 6 bar). The heated material (in this case, metal) reacts with the oxygen and begins to burn and oxidize. This reaction expels more energy and assists the laser beam.

Fusion Cutting/Melt and Blow: An inert gas (usually nitrogen) blows the molten material out of the cut, significantly reducing the power required. The material is first heated until it reaches its melting point, then the gas blows it out

Remote Cutting: A high-intensity laser beam partially vaporizes (ablates) the material, allowing thin sheets to be cut without assist gas.

Cutting vs Engraving vs Marking

 Generally speaking, a laser cutter should also be able to engrave and mark. In fact, the only difference between cutting, engraving, and marking is the depth of the laser and how it changes the overall appearance of the material. In laser cutting, the heat from the laser cuts the material all the way through. This is not the case with laser marking and laser engraving.

Laser marking discolors the surface of the material being lasered, while laser engraving and etching remove portions of the material. The main difference between engraving and etching is how deep the laser penetrates.

The differences between marking and engraving are as follows:

Laser marking: In laser marking, the laser does not completely penetrate the material, but only changes the material's properties or appearance. Lasers create high-contrast marks because the heat of the laser redistributes the carbon in the material in question.

Laser engraving: In laser engraving, the beam physically removes the surface of the material, leaving behind a cavity that reveals your design. The laser heats the material to very high temperatures, causing it to vaporize and forming the cavity.

The differences in laser cutting machines come from the type of laser in the machine, which determines the type of material thickness the laser may be able to cut. Generally, high-powered lasers are well suited for specialized applications that require cutting large pieces of plastic or metal. On the other hand, low-power lasers are effective for thinner materials such as plastics, cardstock, paper, and wood.

The three main types of lasers are:

1. Gas Lasers/CO 2 Laser Cutters

Cutting is done using electrically stimulated CO 2. CO 2 lasers are produced in a mixture consisting of other gases such as nitrogen and helium.

CO 2 lasers emit at a wavelength of 10.6 mm, which has enough energy to penetrate thicker materials compared to fiber lasers of the same power. These lasers can also provide smoother surfaces when used to cut thicker materials. CO 2 lasers are the most common type of laser cutter because they are efficient, cheap, and can cut and raster a wide range of materials.

Materials: Glass, some plastics, some foams, leather, paper products, wood, acrylic

2. Crystal Laser Cutters

Crystal laser cutters produce beams from nd:YVO (neodymium-doped yttrium orthovanadate) and nd:YAG (neodymium-doped yttrium aluminum garnet). They can cut thicker and stronger materials because they have a smaller wavelength than CO 2 lasers, which means they have higher intensity. But because they are so powerful, their parts wear out quickly.

Materials: Plastics, metals, and some types of ceramics

3. Fiber Laser Cutting Machines

Here, cutting is done using glass fibers. The laser light originates from a "seed laser" which is then amplified by a special optical fiber. Fiber lasers belong to the same category as disk lasers and nd:YAG, belonging to the family of "solid-state lasers." Compared to gas lasers, fiber lasers have no moving parts, are two to three times more energy efficient, and are able to cut reflective materials without worrying about back reflections. These lasers can work with both metallic and non-metallic materials.

Although somewhat similar to neodymium lasers, fiber lasers require less maintenance. As such, they offer a cheaper, longer-lasting alternative to crystal lasers. Materials: Plastics and Metals Of the three lasers, CO2 lasers are most commonly used by manufacturers and professionals. They are primarily used for cutting non-metallic materials, and although they have evolved to cut metals, they are still better suited for non-metallic and organic materials (wood, leather, rubber) and for engraving hard materials.

Pros and Cons 

Advantages

1. The following are some comparisons with other cutting technologies such as CNC Reasons to prefer laser cutting over milling:

2. High precision and accuracy

3. High production speed

4. More affordable than CNC machines of the same caliber

5. Wide range of material compatibility

6. No risk of contamination (as it is a non-contact process)

7. Narrower kerf width

Disadvantages

1. High energy consumption

2. Risk of toxic emission release (from plastics)

3. Thicker materials may be difficult to cut

4. Risk of burnt edges on cuts

5. Laser cut designs

A laser cutter works just like your normal inkjet printer. These machines have certain drivers that enable them to pick designs from the computer and convert those designs into a readable format.

Several software packages can support drivers for laser cutting machines:

2D Design

AutoCAD

Mojing

Adobe Illustrator

CorelDRAW

While in theory the designer's imagination is the only limit to what can be created, here are some general guidelines when designing for laser cutting:

The design must meet your tool specifications. The finished file must meet the technical requirements of your machine. Otherwise, attempting to convert the file may result in lost detail or defects.

Know the maximum and minimum laser cut sizes and set them correctly. The size of your design is limited by the size of your cutting table. If the table is 1100 x 1100 mm, you cannot design anything outside of this. Likewise, you should also adhere to the minimum sizes.

Details cannot be smaller than the material thickness. Avoid details that are smaller than the material thickness. For example, if you are making a hole, its diameter should be greater than the thickness of the material.

Maintain a minimum distance between lines. For a given material thickness, there must be a minimum distance between lines. As a rule, keep the distance between parts 2 times the material thickness

The laws of physics always apply. When you cut a piece of metal, it will fall off unless there are connectors in your design.

Show restraint.  When multiple lines intersect at the same point, your design will fall apart or become brittle.

Check the details carefully. Zoom in on the details and make sure the intersections intersect where they need to.

Pay attention to bend relief. Improper bend relief will not give you a nice straight cut with the laser.

Once the design is ready and loaded onto the machine, the laser cutting head will move across the metal sheet in the direction of the design to cut the part as needed. The laser beam cuts through the material along the vector file that holds the design until the shape/pattern is complete.

Laser Cutter Applications

Laser cutting machines have become a handy tool for prototyping and manufacturing. They are being used:

In rapid prototyping, as they allow designers to iterate on their designs quickly and cheaply before mass production.

In machine shops as well as in industrial manufacturing to cut large pieces of material.

In hardware companies to create prototypes.

In education for prototyping/small projects.

By artists and makers who want to bring their digital designs to life.