Laser Cutting Basics : 15 Steps (with Pictures) - Instructables

A laser cutter is a prototyping and manufacturing tool used primarily by engineers, designers, and artists to cut and etch into flat material. Laser cutters use a thin, focused laser beam to pierce and cut through materials to cut out patterns and geometries specified by designers. Apart from cutting, laser cutters can also raster or etch designs onto work pieces by heating up the surface of the workpiece, thus burning off the top layer of the material to change its appearance where the raster operation was performed.

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Laser cutters are really handy tools when it comes to prototyping and manufacturing; they are used in machine shops on the industrial scale to cut large pieces of material, they are used by hardware companies to create cheap, quick prototypes, and they are tools used by makers and artists as a DIY fabrication tool to bring their digital designs into the physical world. In this guide I'll explain what laser cutters are, what they can do, and how you can use them, and I'll also provide some resources if you want to learn and do more with laser cutters.

A laser cutter is a type of CNC (Computer Numerical Controlled) machine, meaning that it is controlled via a computer. A designer can design something in some sort of design software, and then send it to a laser cutter to have it cut out automatically, with just the push of a button. Once a design is sent to a laser cutter, the machine uses a laser beam to cut into or etch into the material on the cutting bed. Laser cutters are a great all around tool because they can be used to make so many different styles of design; laser cutters are used for anything from cardbaord prototypes to rastered artwork. Common laser cutters are primarily used to cut materials like wood, some plastics, and paper and cardboard, although there are more powerful laser cutters that can cut through metals and much thicker materials.

Laser cutters can be very quick, and can churn out designed parts in just a few minutes. Like 3D printers, laser cutters are rapid prototyping machines; they allow designers to quickly and cheaply iterate on their designs before they produce products on a larger scale.

There are a few different types of laser cutters, but they all essentially use the same process of using a laser to cut material. The laser originates from a laser resonator, which sends out a beam of intense light through reflects through a system of mirrors to the cutting head. Within the cutting head, the laser is focused through a lens and narrowed down to an extremely thin, concentrated beam. This beam is projected down at the material and can cut or raster the raw stock, which I'll cover in more detail later. The cutting head is usually mounted on what is called an XY gantry, which is a mechanical system driven usually by belt or chain that allows for the precise movement of cutting head within a given rectangular area, which is the size of the work bed. The gantry allows the laser head to move back and forth and forward and back over the work piece so that it can make precise cuts anywhere on the bed. In order for the laser to actually cut, the focal point of the lens, where the laser would be at its finest, needs to be on the surface of the material it is cutting through. All laser cutters require a focusing procedure before making their cuts to ensure that the laser cuts well.

The difference between different types of laser cutters comes from what types of lasers the machines have. The type of laser defines what type and thickness of material it can cut through, because different laser types have different power ranges. Usually, higher power lasers are used on the industrial scale to cut out large sections of sheet metal or plastics, while lower power lasers are used for a wide range of thinner, more potentially flammable materials like paper and card stock, wood, and some plastics. I'll cover the main types of laser cutters as well as the important settings laser on.

There are three main types of lasers used in laser cutters; CO2 lasers, fiber lasers, and neodymium lasers. Although the laser cutters are all built very similarly, they are distinct in that each type of laser has a specific power range, thus each can be used to cut through different material types and thicknesses.

CO2 Lasers: The laser is generated from electrically stimulated gas mixtures (mostly comprising of carbon dioxide). CO2 lasers are the most common types of laser cutters because they are low power, relatively inexpensive, efficient, and can both cut through and raster a wide variety of materials.

Materials: wood, paper based products (cardboard, etc), leather, acrylic, glass, some plastics, and some foams (can raster on anodized metals)

Neodymium Lasers: The laser is formed from neodymium doped crystals. These lasers have a much smaller wavelength than CO2 lasers, meaning they have a much higher intensity, and can thus cut through much thicker, stronger materials. However, because they are so high power, parts of the machine wear and tend to need replacing.

Materials: metals, plastics, and some ceramics

Fiber Lasers: These lasers are made from a "seed laser", and then amplified via special glass fibers. The lasers have an intensity and wavelength similar to that of the neodymium lasers, but because of the way they are built, they require less maintenance. These are mostly used for laser marking processes.

Materials: metals and plastics

During a cutting operation, the cutting head fires a continuous laser at the material to slice through it. In order to know where to cut, the laser cutter driver reads all of the vector paths in the designed piece. Once you send your file to a laser cutter, only lines that register as only hairline or vector graphics with the smallest possible line thickness will be cut by the laser. All other graphics, like any images or thicker lines, will be rastered, which I'll explain in a bit. The laser, when supplied with the right settings, will cut all the way through your material, so vector cutting is normally used for cutting out the outline of the part as well as any features or holes that you want to cut out of the material.

Rastering is a lot different than vector cutting; instead of cutting all the way through the workpiece, the laser will burn off the top layer of the material you are cutting to create two color (and sometimes grayscale) images using the raster effect. In order to raster materials, the laser will usually be set to a lower power than it would when vector cutting material, and instead of shooting down a pulsing beam, it creates fine dots at a selected DPI (dots per inch) so that the laser doesn't really cut all the way through. The DPI directly correlates to the image resolution and affects how fine an image appears, exactly like image resolution on a computer. By adjusting the DPI you can control the laser's effect on the material. Rastering on some materials comes out really clearly, while you may not get exactly what you expected on other materials. Before you raster for the first time, make sure you experiment with the settings until you get the desired effect!

Before I start going into the processes of vector cutting and rastering, I want to quickly cover the settings you will encounter. A laser cutter has four primary settings, as listed and described below. While power and speed apply to both vector cutting and rastering, frequency only applies to vector cutting and resolution only applies to rastering. The settings need to be changed based on your material in the laser cutter "Print Properties" dialogue box before you "print" your job (remember, laser cutters connect to computers like normal printers). based on the material you are cutting through or rastering on: for example, harder, thicker materials require higher power and lower speed so that the laser can actually be strong enough and move slow enough to successfully cut all the way through the material, while thinner, weaker materials can be cut with lower power and higher speed.

Power: How strongly the laser fires. A high power will cut through stronger, thicker material, but may end up burning thinner, more flammable stock. A low power may not be strong enough to get all the way through the material. During rastering, higher power will burn more layers off of the material, creating a darker image.

Speed: How fast the head of the laser cutter moves along its gantry. A high speed will cut faster, but may not cut all the way through if you have thicker or stronger materials. A low speed will definitely cut through, but has the potential to burn or melt the edges of the material as it slowly cuts. During raster operations, the laser moves back and forth very quickly, so a high speed on a large piece may wear out the gantry.

Frequency (only for cutting): Determines how fast the laser pulses during a cutting operation. The laser turns on and off rapidly when it makes cuts, so a higher frequency will create a cleaner cut, but if the material is flammable it may end up catching fire, so a lower frequency would be preferable.

Resolution (only for rastering): Determines the resolution and quality of the raster operation. A higher resolution will produce a better, darker image, but if there is too much heat concentrated in one area, it may severely melt, burn, or damage the work piece.

As I've already mentioned, laser cutters have defined material ranges and limitations. While some of this is due to the power it takes to cut through certain materials, some of the material limitations come from the gases that certain materials make when burned or cut with a laser. Other materials can be cut, but respond poorly to heat and may shrivel or melt. Like any other machining technology, there are definitely things that you can and can't do on a laser cutter. Laser cutters may seem pretty limiting because they can only cut out flat objects, but there are a surprising amount of things that you can do with laser cutters that you may not have expected. I'll cover a couple design techniques, cool ideas, and design limitations so that you can get familiar with the technology and start designing!

As I explained earlier, the focal point of the lens of the laser cutter focuses the laser on the surface of the material it is cutting. This means that on the other side of the material, the laser isn't as focused, and its beam is actually slightly larger than the beam at the focal point. The gap that the laser makes when it cuts through material is called its kerf. All cutting machines have kerf because the cutting tool has thickness. For example, the kerf on a saw blade is usually a rectangle the width of the blade. The kerf of a laser cutter is slightly trapezoidal. Because the laser beam gets wider after its focal point, the width at the bottom of the material is wider than at the top. The kerf of a given laser cutter determines the maximum thickness of material that it can cut, because on thicker materials the beam will either get too unfocused to cut well, or it will have an angled kerf, which may be unsatisfactory for the designer. Most smaller scale laser cutters can only cut material up to about a quarter of an inch, because after that point the kerf width gets too large.

Because the laser beam itself is very small when cutting, laser cutters can usually create very fine, small details, even when rastering. The kerf of a laser cutter is much thinner in general than the kerf of a sawblade or a milling bit, for example, so laser cutters can do some really nice detail work. However, there is a limit to how small features can be made. Just because the laser cutters can do small features, doesn't mean the material will handle it well.

Small features and details concentrated in a specific place means that the heat from the laser will dwell in that area for a long time. This creates a lot of concentrated heat, which may cause the part to catch on fire or melt, especially if the material is flammable. Usually a good rule of thumb is to leave at least an eighth of an inch between two approximately parallel lines you will be laser cutting to prevent the laser from damaging the part.

Additionally, be careful about creating very thin features in your designs. Thinner features have a much higher tendency to break, just because they have very small cross sectional areas, and most parts cut out on a laser cutter, like wood, acrylic, and plastic, tend to be very brittle, so they will snap very easily if designed features are too thin.

There are a lot of different ways to make joints from flat pieces, and not all are limited to laser cutters, but a lot of the techniques carry over from fields like woodworking and metalworking. Here are a few simple joining techniques for two pieces of flat stock. There are much more if you're willing to explore and experiment, but lets start with the basics!

Finger Joints

Finger joints are the basic joint for putting two flat plates together at a perpendicular angle to make a corner. It basically consists of tabs on the mated sides that interlock. The tabs are usually as long as the material is thick to make a nice, clean seam.

Mortise and Tenon Joints

Mortise and tenon joints are very similar to finger joints, except the "fingers" on one piece of material stick through holes in the other piece of material. These are useful for creating "T" like structures and easily mounting internal support beams for more complicated laser cut structures.

Slotted Joints

Slot joints are another pretty common type of simple laser cut joint. The two connecting pieces each have slots cut halfway through them, which can slide into each other to form "X" like structures out of the laser cut material.

Dovetail and Jigsaw Joints
Dovetail joints and jigsaw joints are usually used in laser cutting to mount two materials flush to one another, with even top and bottom surfaces. Although these are more widely used in woodworking, they can come in handy if you're looking for a certain effect.

Using Bolts

The above joints will work just fine with some glue around the edges, but you may not want to make such a permanent seal on your parts. By creating a hole for a bolt to slide through and a slot for a nut to be press fit into, you can secure the joints of laser cut parts easily.

Most materials that you can cut on the laser cutter will be pretty brittle. However, by cutting out sections and patterns from the material, you can actually make them quite flexible! These flexes are called kerf bends or living hinges. They usually utilize the kerf of the laser cutter to create notches in the material, which relieves tension in the material and allows it to bend. The notches are patterned along the area where you want your material to bend, and this loosens up the material enough to allow it to flex pretty nicely. Other design techniques can be used to take advantage of the flexibility as well, to create snap fit hinges that keep the parts locked together.

If you're interested in learning more about kerf lattices, there is a great Instructable on it here.

When cutting carbon steel with a fiber laser, precision in perforation is essential for ensuring smooth and efficient cutting. Below are some expert suggestions for optimizing perforation and overall cutting performance.

Perforation Optimization Tips:

1. Increase Peak Power: Use 70%-100% of peak power to improve perforation efficiency. This helps in rapidly breaking through the surface of carbon steel.

2. Ensure Laser Centering: Proper laser alignment is crucial. Adjust the perforation focus to about -6 to achieve better results.

3. Air Pressure Settings: Keep oxygen pressure consistent between perforation and cutting, typically around 1 bar for carbon steel.

4. Multi-Level Perforation: Between perforation stages, stop the light and use a burst of air. This technique helps prevent hole bursting.

5. Adjust Perforation Frequency: At the third stage of perforation (high position), match frequency and dwell time for smooth slag removal and improved cutting stability. Use frequencies around 500-800Hz, with a dwell time of about 100ms. The focus should be between 0 and +2.

6. Duty Cycle Management: Gradually increase the duty cycle from 35% to 75%, stepping up from level 3 to level 1 to ensure a smooth transition through the perforation stages.

7. Cutting Height Adjustments: Adjust the cutting height for each perforation level: 20mm for level 3, 15mm for level 2, and 10mm for level 1.

8. Frequency Settings: Use frequencies of 100-300Hz for levels 1 and 2 perforation to maintain consistent cutting performance.

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9. Focus Settings by Level: Set the focus between -6 and -2 for levels 1 and 2, and between 0 and +2 for level 3. Positive focus at level 3, combined with high power and frequency, creates a small groove, easing the subsequent cutting process by thinning the plate and helping slag removal.

10. Pulse Perforation Technique: Most perforation methods for carbon steel involve pulse lasers. High peak power in each pulse melts a small amount of material, aided by oxygen, allowing for stable cutting with minimal slag formation.

Specific commissioning results will be determined based on on-site conditions; the content of this article is for reference only.

For thin carbon steel, air perforation with low power, low duty cycle, and high frequency can minimize slag and create a cleaner starting point for the cut.

Fine-Tuning Your Carbon Steel Cutting Process

Once you have mastered the basics of perforation, you can begin to fine-tune the cutting process to enhance both precision and efficiency. Below are some advanced debugging techniques to help ensure optimal results.

Debugging Tips for Improved Cutting Performance

Maximizing the Bisection Method:

· The bisection method is ideal for finding the optimal focus point. Start by selecting the midpoint of the focus range, then gradually narrow it down by halving the range with each adjustment. This method allows for precise fine-tuning of focus, pressure, and speed.

Bright Surface Cutting:

· For bright surface cutting, use a larger focus and a smaller nozzle. This combination increases the spot diameter, ideal for cutting thick carbon steel, and improves the molten steel flow by reducing the slope of the cutting seam.

Choosing the Right Nozzle: Single vs. Double Nozzles

For Beginners:

· Single nozzles are generally suitable for air or nitrogen cutting, while double nozzles are better for oxygen cutting.

During High-Power Tuning:

· Break traditional assumptions. In some cases, using a single nozzle for oxygen cutting in high-power scenarios may yield better stability and surface finish than a double nozzle.

Managing Nozzle Overheating:

· When cutting thick carbon steel with high-power lasers, overheating can affect the capacitance of the ceramic ring and destabilize the cutting head. Test the nozzle temperature under full power and use additional cooling methods, such as air or water-cooling systems, to prevent overheating.

Solving Common Issues in Carbon Steel Cutting

When cutting thick carbon steel with oxygen, nitrogen, or air, issues like slag formation, spatter, or sectional patterns can arise. Below are common problems and solutions.

Problem 1:  Large Sectional Patterns on Thick Carbon Steel (40mm+) with Oxygen

Increase the Cutting Focus

For carbon steel thicker than 40mm, raise the cutting focus to +15 or higher. A higher focus improves the cut quality, resulting in smaller sectional patterns.

Increase the Nozzle Height

Raise the nozzle height to around 1.4mm. Compared to a height of 0.3mm, this reduces the size of the patterns on the cut surface, but it may increase the taper of the cut.

Key Insight: The higher the focus, the smoother the cut. Increasing the height of the nozzle mimics increasing the focus, which improves the surface quality.

Nozzle height 0.3 vs Nozzle height 1.4

Problem 2: Problem 2: Slag Hanging at the Bottom (45mm Carbon Steel)

Further Reduce Cutting Speed

Slowing down the cutting speed allows the laser to penetrate better, reducing the amount of slag.

Lower the Cutting Focus and Increase Air Pressure

Reducing the focus and increasing the air pressure improves cutting performance, especially at the bottom of the material.

Problem 3: Surface Spatter with Nitrogen or Air

Raise the Focus

Increasing the focus helps reduce surface spatter during cutting.

Reduce the Air Pressure

Lowering the air pressure can also minimize the amount of spatter that sticks to the surface.

Problem 4: Hard Slag Formation with Nitrogen or Air

Lower the Focus

Decreasing the focus helps reduce the formation of hard slag.

Increase the Cutting Speed

Faster cutting speeds help prevent the material from overheating, which reduces slag formation.

Use a Smaller Nozzle Diameter

A smaller nozzle concentrates the gas flow and improves cutting precision, reducing slag buildup.

More cutting questions and answers：Efficiency first - 10 common laser metal cutting quality defects and how to avoid them

Example Cutting Parameters for Carbon Steel with 6kW Lasers

Finally, understanding the recommended parameters for specific cutting scenarios can help further ensure successful results. Whether you’re cutting carbon steel with 6kW lasers or optimizing nozzle heating, these parameter adjustments can guide you to achieve the best possible cuts. 

Specific commissioning results will be determined based on on-site conditions; the content of this article is for reference only.

20mm Carbon Steel Plate (Oxygen Cutting): Start with nozzle sizes 1.6/1.5/1.4, adjusting based on plate size.

25mm Carbon Steel Plate (Oxygen Cutting): Nozzle sizes 1.6/1.8/2.0. Activate cooling gas before starting the cut, and use a vortex tube to maintain nozzle temperature.

Remember, the larger the focus, the better the cutting effect, but this also increases nozzle heating. Always monitor and control nozzle temperature for the best cutting results.

Conclusion

Perforating and cutting carbon steel with fiber laser machines involves a fine balance of power, precision, and parameters. By implementing these advanced techniques, professionals can enhance their cutting efficiency, reduce defects, and improve overall cutting quality. As always, continuous adjustments to focus, nozzle size, and cutting speed are key to mastering carbon steel cutting.

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