Get to know laser processing
1. Laser processing principles
- Laser beam generation: Laser beams are generated by a laser module and are focused onto a small spot through an optical system.The energy intensity of the laser beams is so high that they induce a significant thermal effect on the material surface.
- Laser energy absorption: When laser beams strike a material surface, the material absorbs laser energy and transfers it to heat energy. Laser energy absorption is the key to processing results and it varies with material colors. For example, black materials absorb more laser energy in most wavelengths. Therefore, laser energy can be transferred to heat more efficiently on black materials, and such materials can be heated, melted, or vaporized more easily, improving processing efficiency and precision. On the contrary, white materials reflect, rather than absorb, more laser energy than materials of other colors. Therefore, processing white materials requires higher laser power and lower processing speed. However, no matter how high the laser power and how low the processing speed, processing results on white materials are not as detailed and precise as those on black materials.
- Laser processing: The laser beam moves along a preset processing path. During the processing, the laser beam heats the material till the material surface temperature rises to the melting or vaporization point, and thus engraving and cutting the material.
- Laser engraving: engrages images or text on materials such as wood, acrylic, and metal.
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- Laser cutting: precisely cuts materials such as wood, acrylic, and paper.
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2. Impact factors on laser processing
2.1 Key factors of laser machines
- Laser source
Laser source indicates laser wavelength, which decides what materials a laser machine can process. In other words, only when materials absorb enough laser energy of certain wavelength can they be processed. When a laser beam strikes a material surface, the laser energy can be partially reflected, absorbed, or transmitted based on the material type and the laser wavelength. According to the law of energy conservation,
("E" refers to "energy".)
A decent number of metal materials absorb the energy of 1064 nm infrared fiber laser efficiently. In contrast, transparent acrylic materials transmit lasers within visible wavelength range and therefore cannot be processed. To produce better results, lasers within infrared wavelength range produce better results on acrylic materials.
The following provides detailed descriptions of the three laser types.- 455 nm blue-light laser
Blue-light laser is within the visible wavelength range. Materials like wood, stainless steel, and ceramics can effectively absorb blue-light laser energy. However, lasers within the visible wavelange range have limited wavelengths, and certain materials cannot absorb the laser energy effectively. For example, semi- or all-transparent materials may transmit visible lasers but cannot absorb their laser energy. Besides, materials of certain colors absorb little blue-light laser energy. Therefore, blue-light laser processes limited range of materials. - 1064 nm infrared-fiber laser
1064 nm infrared-fiber laser is widely used, especially on metal materials. Compared with visible light, near-infrared light can be better absorbed by most metal materials. In this case, laser energy can be effectively transferred onto material surface to achieve efficient cutting, engraving, and even welding. 1064 nm infrared-fiber laser, also known as the pulsed laser, boasts low instantaneous energy intensity, and therefore has lighter thermal effect on materials and is suitable for fine processing. - 10.6 μm CO2 laser
10.6 μm CO2 laser is commonly used for processing non-metal materials such as wood, plastic, and ceramics. That is because most non-metal materials can absorb more laser energy emitted by 10.6 μm CO2 lasers and transfer laser energy into heat energy for cutting or engraving.
- 455 nm blue-light laser
- Laser power
Laser power decides how deep a laser machine can cut a material. To be more specific, laser power refers to the amount of laser energy produced per unit of time, in W. For example, when processing a material that can well absorb the energy of a certain laser, low laser power may lead to poor processing results if the material is thick and hard. - Spot size
Laser spot on the material surface is the diameter of the concentrated laser beam. The smaller the spot, the higher the laser energy and the processing precision. Spot size depends on focal length.- Focus
Focus concentrates the most laser energy and plays a key role in laser processing. The focus position determines both the minimum diameter of spot and the concentrated energy position on the material surface. Laser processing can be categorized into the following three types according to the focus position on the material.- On the material surface: suitable for engraving or cutting materials of moderate thickness. When the focus is on the material surface, the laser machine can concentrate the maximum energy to cut with the minimum width of cutting line.
- Inside or below the material: suitable for engraving or cutting materials of greater thickness. When the focus is inside or below the material, the spot size will slightly expand and ensure that the laser energy is strong enough to penetrate inside the material. This processing type helps to cut deeper for 3D engraving or thick material cutting.
- Above the material surface: suitable for scoring or slightly engraving materials. The spot size is comparatively larger than the other two types.
- Focal length
Focal length is the distance between the laser lens and the focus. This parameter decides the spot size and the depth of focus. - Depth of focus
The depth of focus is a distance range up and down the optical axis from the focus of a laser beam, within which the laser can produce a good engraving or cutting effect.- Short depth of focus: generated by short focal length and suitable for precise engraving. When the depth of focus is short, it means the focus is within a limited range of focal length. In this case, even slight deviation of the focal length can result in poor processing results. Therefore, short depth of focus requires a more precise position of the focus.
- Long depth of focus: generated by long focal length and suitable for cutting thick materials. If the depth of focus is long, the range over which laser energy is concentrated is greater. In this case, the laser can still give a good cut even if the material surface is uneven or the focus deviates slightly. In other words, long depth of focus can evenly cut thick materials but does not guarantee the precision of cutting and engraving results.
- Focus
- Motion resolution
Motion resolution is the shortest distance that a laser beam can move. The higher the motion resolution, the more detailed the engraving or cutting results. For instance, when engraving hairs on materials, low motion resolution leads to only the overall outline, while high motion resolution results in hair strands with distinct and visible details. - Processing range
Processing range is the area where laser moves to process. Set this parameter properly if the object to be processed covers a large area. - Processing speed
Processing speed is the moving speed (mm/s) of a laser beam. The maximum working speed is theoretically established and not necessarily the highest speed during material processing. The maximum processing speed depends on the laser machine structure, processing power, and processing materials.- Flatbed laser machine: Also known as XY-axis laser machines. The structure of flatbed laser machines may result in vibration, step loss, or other problems during high-speed processing. Therefore, to balance processing efficiency and quality, make sure that the machine is steady before choosing proper processing speed.
- Galvo laser machine: The simple structure and flexible movement of the galvometer lens help ensure steady machine status and reduce vibration and step loss during high-speed processing. When using a galvo laser machine, you can set a high processing speed for greater efficiency.
- Cooling system: Prevents the laser module from being overheated by the large amount of heat generated during laser processing. To ensure processing stability, the water-cooled or air-cooled system plays a key role in preventing overheat of the laser module.
- Air assist: Compressed air is used to clear smoke, dust, and slag. Besides, it helps to get materials burned, vaporized, or melt to enhance cutting efficiency and results.
- Others: The preceding are core parameters of a laser machine, Other parameters, including focusing methods, positioning methods, and machine sizes, mainly affect the convenience of laser processing operations.
2.2 Software factors
- Lines per inch (LPI): LPI affects the resolution of the processing result.
- High LPI: produces detailed results but requires longer processing time.
- Low LPI: requires less processing time but produces less detailed results.
- Dots per inch (DPI): DPI affects the image details and clarity.
- High DPI: produces high-resolution images, suitable for fine engraving.
- Low DPI: suitable for engraving designs that cover a large area and require less resolution.
- Image algorithm
- Grayscale algorithm: The grayscale algorithm helps to produce images of different grayscale levels on the material surface. The detailed steps are as follows:
- Image conversion: converts an image into a grayscale image. That is, the algorithm converts the RGB values of each pixel into corresponding grayscale values calculating the weighted averages.
- Grayscale level mapping: maps the image grayscale levels to the laser energy output range. This step depends on the laser machine characteristics and how much laser energy the material can absorb.
- Laser power adjustment: adjusts laser power based on each pixel grayscale to produce corresponding gray level on the material.
The grayscale algorithm helps to reproduce images on materials with richer grayscales to make the processing results more detailed and realistic. This algorithm is suitable for tasks that require grayscale gradients or image engraving with rich details on material surfaces.
- Dithering algorithm: The dithering algorithm converts an image into a black-and-white one. The detailed steps are as follows:
- Image binarization: converts a grayscale image into a black-and-white image. That is, the dithering algorithm sets pixels with grayscale values higher than a predetermined threshold to white and those lower than the threshold to black.
- Error diffusion: diffusses the errors between white and black pixels in the image to neighboring pixels. This allows for the adjustment of grayscale values of certain pixels to better approximate the grayscale distribution of the original image.
- Dithering processing: introduces periodic dithering into the image to simulate the effects of different binary grayscale levels. This involves periodic switching between black and white of surrounding pixels, so as to better control laser power.
The dithering algorithm helps to achieve higher resolution and better control the image grayscale levels. Besides, it simplifies requirements for laser power compared with the grayscale algorithm. The dithering algorithm is suitable for engraving tasks that include less colorful images and require precise image details.
- Grayscale algorithm: The grayscale algorithm helps to produce images of different grayscale levels on the material surface. The detailed steps are as follows:
Wood processing guide
1. Laser processing
1.1 Principles
- Processing principles:
Laser processing focuses high-intensity beams on the surface of a wood material, causing the material to heat up and either vaporize or burn. This process enables the laser machine to engrave or cut the wood material.
Among various types of lasers, the 10.6 μm CO2 laser and the 455 nm blue-light laser are particularly adept at processing wood materials. Wood absorbs laser energy effectively and boasts low thermal conductivity. Therefore, heat can be concentrated in the processing area, which makes wood materials well-suited for precise processing. However, low thermal conductivity makes it difficult to heat up other parts of a material. The material can get burned if laser beams stay on it for a long time and causes heat accumulation in certain spots. As a result, the heat-affected zone expands, cutting slits become wider, leaving severe carbonization around the cutting line. As for engraving, severe carbonization results in blurred engraving results. Note that when laser processing wood materials, try to avoid burning the materials.
Compared with 10.6 μm CO2 laser and 455 nm blue-light laser, 1064 nm infrared-fiber laser may not give good engraving results, and is not recommended for processing wood materials, unless the materials are coated. - Material features:
Laser cutting efficiency in wood is affected by such factors as wood density, moisture content, surface smoothness, grain, and knots.- Density: influences the laser penetration ability. Denser wood materials require higher laser power for effective cutting. When laser power is insufficient, a long processing time is needed for the beam to process the material. This necessitates lower processing speeds and multiple passes for effective cutting. However, prolonged exposure can lead to material burning, an expanded heat-affected zone, carbonization around the cut lines, and ultimately, less satisfactory results.
- Moisture content: influences laser processing performance. Higher moisture content in wood leads to better thermal conductivity, reducing the carbonization around cut lines. Wood with higher moisture content necessitates slower processing speeds, resulting in a greater loss of laser energy throughout the process. Excessively dry wood tends to be brittle, burns easily, and carbonizes heavily, while overly wet wood generates excessive smoke and hampers cutting efficiency.
- Surface smoothness: essential for engraving quality as burrs and roughness on wood surfaces can negatively impact the results. To ensure satisfactory processing outcomes, it is advisable to sand wood materials before laser processing. Wood materials available on xtool.com are pre-sanded to ensure a smooth surface, facilitating high-quality processing results.
- Grain and knots: Natural grain and knots of wood materials may lead to variations in cutting or engraving results during processing. These characteristics of wood materials can negatively affect the processing results.
1.2 Cautions
- Ventilation and smoke extraction: Proper ventilation and smoke extraction are crucial when processing wood materials that produce smoke and odors. To achieve good processing results while maintaining a safe working environment, it's important to have good ventilation and effective smoke extraction systems. During processing, xTool SafetyPro™ IF2 and xTool SafetyPro™ AP2 can be used together to efficiently extract smoke and gases, ensuring both processing safety and good ventilation.
- Anti-fire measures: Wood materials are flammable and need close attention during processing. You can use xTool Fire Safety Set to effectively enhance safety and reduce fire risks.
1.3 Processing techniques
How to avoid scorching or charring marks on wood materials
- Why there are scorching or charring marks on wood materials during laser engraving and cutting
The power exerted from the laser module is strong enough to easily engrave and cut wood materials or other tough materials. The laser beam can elevate the surface temperature of materials, enabling engraving or cutting processes to take place.
Therefore, many assume that scorching marks on wood materials stem from high laser power, but this is hardly the truth. While excessive power can indeed burn wood materials, utilizing the appropriate laser power and processing speed can prevent the occurrence of scorching marks on the materials.
In fact, when wood materials are being burnt, dark-colored particles from the smoke adhere to wood material surface, resulting in scorching marks. When the temperature of the smoke is excessively high, it can cause the colors of wood materials to change to a yellow hue.
Hence, to prevent scorching marks, it is essential to monitor and manage the smoke produced during laser engraving and cutting processes carefully. - How do I avoid scorching marks on wood materials
In this session, effective measures such as adjusting accessories and parameters will be introduced to prevent scorching marks during laser engraving and cutting processes. You can apply one or more measures during processing.
a. Use masking tapes
Using masking tapes is the best way to avoid surface scorching marks. By applying masking tapes to wood materials before laser engraving or cutting, scorching marks will be left on the tapes rather than on the material surface.
b. Use honeycomb panels
During laser processing, smoke can flow between the material and the machine baseplate, potentially causing scorching marks on the back of the material. Therefore, a honeycomb panel is required to provide the best ventilation environment so that the smoke can pass through the gap between the material and the baseplate smoothly. It is crucial to clean the honeycomb panel promptly after each processing session to prevent the material surface from being stained by any residual oil on the honeycomb panel.
c. Use air assist set
Air assist set provides a strong airflow to clear away debris and smoke from the material being processed. The color change on the material surface can be attributed to the heat carried by the smoke generated during the processing. To address the color change and prevent scorching marks on materials, an air assist set is necessary for lower temperature of material surface. Moreover, employing an air assist set can also help prevent materials from burning and improve the processing speed and efficiency of lasers.
d. Improve exhaust system and ventilation
A poor exhaust system for laser processing may lead to scorching marks on materials. The smoke produced during laser processing contains particles that can adhere to materials and accumulate if they are not effectively cleared from the working area. This may cause fires and leave permanent marks on the materials.
e. Add water
Wetting the wood materials can also prevent scorching marks. You can apply water to the wood material surface. For thin wood materials, soaking them in water can be particularly effective. Water on the material surface acts as a barrier, preventing smoke from causing scorching marks on the material.
f. Process multiple times
Choosing right parameters is the key to preventing wood materials from burning. For optimal results, it is crucial to adjust laser power, processing speed, and processing times according to the specific characteristics of the wood materials being processed. It is recommended to laser cut wood materials at higher processing speeds. This approach effectively minimizes the likelihood of scorching marks on cut lines, resulting in clearer and neater cutting edges compared to processing at slower speeds with higher power settings. In fine engraving, employing multiple shallow engravings rather than deep incisions on wood materials can help reduce the risk of scorching the materials. However, multiple cutting times on complex vectors in wood materials can generate debris that may smudge the surface. In such situation, the use of honeycomb panels is recommended.
g. Lower laser focus
To cut thick wood materials with lasers without causing scorching marks on the surface, it is recommended to adjust the focus of the laser inside the material. This can help achieve clean and precise cuts.
How to avoid getting wood materials warped
- Methods to avoid warped wood materials
a. Control of humidity and storage environment
Wood materials are sensitive to humidity levels. Excessive or insufficient humidity can lead to warping in the wood. Therefore, it is important to maintain the relative humidity of the working environment between 40% and 60% to prevent significant fluctuations in humidity levels. If wood materials have become slightly warped, placing them in an environment with stable humidity levels can help flatten the materials.
b. Pressure treatment
To address warped wooden materials, you can use a flat, heavy object to press down on the warped area. Simultaneously, spray a small amount of water evenly on the opposite side of the warped area. This can help balance the humidity and assist in flattening the material, and the materials may gradually return to a flat state after a long time. This method is suitable for thin or medium-thickness wood materials.
c. Sanding and trimming
If a wood material is significantly warped, you can sand the excess part, or heat up the excess portion and then sand it down to achieve a flat surface. This approach demands a higher level of expertise and is best suited for applications in craft production.
d. Cutting grooves into the back of wood materials
To address warping in thick wood materials, you can cut grooves into the back of the materials. This technique helps release internal stresses within the wood, which can alleviate warping issues. The depth and position of the grooves should be adjusted according to the extent of warping present in the wood materials.
Can laser-processed items come into contact with food
- Recommended use and handling of laser-processed items
To ensure food safety of laser-processed items, it is advisable to engrave on the side that does not come into direct contact with food. Alternatively, specializing in laser-engraved items that do not have direct contact with food is a prudent approach. Some users may choose to coat the laser-engraved surface with cooking oil in an attempt to avoid particles or debris from getting into the food. However, the application of oil cannot establish a sufficient barrier to impede bacterial growth or to prevent direct contact between food and the engraved area. Therefore, oil treatment is not a dependable solution for ensuring food safety when it comes to laser-engraved items.
a. Utilizing food-safe sealing materials
To ensure the food safety of laser-engraved items, it is recommended that the processed surfaces be sealed with food-grade epoxy resin. The epoxy resin effectively fills all the pores in the engraving area, forming an airtight layer that inhibits bacterial growth and prevents direct contact between food and the engraved surface. FDA-approved food-safe epoxy resins are readily accessible in the market, offering various colors and finishes that not only ensure food safety but also enhance the visual appeal of the item.
Despite the sealing with food-safe epoxy resin, it is not advisable to use these items for direct food cutting or preparation to maintain optimal food safety standards. Due to the limited durability of epoxy coatings, using a knife on these items may damage the coating, potentially exposing unsanitary carving areas. Therefore, the sealed item is better suited for serving food on a tray or as a decorative piece rather than for direct food cutting purposes.
b. Proper cleaning of laser-engraved items
Items that have undergone laser engraving should be wiped with a damp cloth to eliminate surface residue and debris. During the cleaning process, you can utilize warm water and soap to uphold cleanliness. Additionally, applying white vinegar to the engraved area can help eliminate bacteria in the grooves. After cleaning, be sure to thoroughly dry the item to prevent further bacterial growth due to moisture.
Metal processing guide
1. Laser processing
1.1 Principles
- Processing principles:
Laser processing of metals uses a high-energy laser beam to instantly melt, vaporize, or oxidize metal materials, achieving cutting, engraving, and marking effects. One of the commonly used laser is 1064 nm infrared fiber laser, which can be used to process stainless steel, aluminum, copper, and brass. - Material features:
- Thermal conductivity: The high thermal conductivity of metal materials make it possible for them to rapidly conduct heat from the processing area to the surrounding area after absorbing the laser energy. The higher the thermal conductivity, the slower the local temperature rise during laser processing, and the larger the heat affected zone (HAZ) will be. This may result in less clear edges, especially during cutting and engraving. Therefore, when processing metals with high thermal conductivity, it is necessary to optimize laser power, speed, and focal length to ensure that localized areas can reach temperatures required for melting or vaporization.
- Reflectivity: Most metals are highly reflective to laser beams, especially to that of 10.6 μm CO2 laser. For example, metals such as aluminum and copper will reflect most of the incident laser energy, causing energy waste and may even damage the laser machine. These highly reflective materials require specific coatings or absorption layers to enhance the absorption rate of laser energy. The smoother the surface, the higher the reflectivity and the lower the absorption rate.
- Absorption rate: The absorption rate of metals for different laser wavelengths plays an important role in laser processing effects. Generally, metals have a higher absorption rate for short-wavelength lasers, such as 1064 nm infrared fiber laser, and a lower absorption rate for long-wavelength lasers, such as the 10.6 μm CO2 laser. The absorption rate is affected by factors such as surface roughness, oxidation layer thickness, and temperature of the metals. Metals with rough surfaces or oxidation layers usually have a higher laser absorption rate. The higher the absorption rate, the higher the processing efficiency, and the faster the laser energy can be absorbed by the material and converted into thermal energy for processing. For metals with low absorption rates, adjusting laser power, processing speed, and focal length, or using a suitable wavelength can improve processing efficiency. Generally, the absorption rate gradually increases as the temperature rises.
1.2 Cautions
- Highly reflective materials: Metals with mirror surface treatment processes are highly reflective, which easily reflects laser beams and may damage laser machines. To reduce reflection, consider using specific wavelengths like fiber lasers or apply anti-reflective treatments to the metal surface, such as black painting.
- Protective measures: Laser processing of metals generates high temperatures. Always wear protective glasses, and avoid touching the metal immediately after processing to prevent burns.
- Laser focus: Make sure the laser is focused on the metal surface. Any deviation in focus could result in poor engraving effects or failure in engraving.
1.3 Processing techniques
How to colorfully engrave stainless steel and titanium alloys with lasers
- What is color laser engraving
Color laser engraving: Color laser engraving is achieved by controlling high-energy laser beams to interact with the metal surface and adjusting laser parameters to generate different colors. There are three main coloring principles:
- Coloring through oxide films: Laser irradiation triggers the formation of an oxide film on the metal surface. You can get oxides of different colors by adjusting laser parameters. For example, titanium alloys can generate yellow and blue oxides.
- Coloring through microstructural development: Laser irradiation triggers the formation of periodic microstructures on the metal surface. These microstructures, in turn, induce light diffraction and interference phenomena, ultimately manifesting as angle-dependent chromatic variations.
- Coloring through nanostructures: Nanoparticles and plasma effects formed by lasers result in the surface presenting specific colors.
Stainless steels and titanium alloys are common metal materials suitable for color laser engraving. Color changes can be achieved by adjusting power, speed, line density, processing times, and other parameters. The commonly used laser light sources are 455 nm blue light diode laser and 1064 nm infrared fiber laser.
- Application suggestions for metal color laser engraving
- Parameter matrix
Forming oxide films on the surface is a main method to achieve color engraving on stainless steels or titanium alloys with a 455 nm blue light diode laser. For coloring throught oxide films, the key is to control the composition and thickness which is related to laser processing parameters, environmental conditions, and sample properties. To achieve the desired reference color parameters, it is advisable to perform a parameter matrix test on a spare metal sheet by adjusting laser processing parameters such as laser power, scan speed, processing times, line density, and focal distance.
- Parameter matrix
How to engrave metal materials not suitable for 10.6 μm CO2 laser and 455 nm blue light diode laser
- Laser applications on non-adaptive metal materials
1. Laser marking spray
Using laser marking spray to coat the metal surface is an effective and stable auxiliary technique capable of significantly enhancing laser processing effects. The core principle is to evenly spray a specialized coating on the metal surface, allowing it to absorb laser energy more efficiently. This technology is particularly suitable for highly reflective metals such as aluminum, brass, and mirrored stainless steel. Without coatings, these metals often struggle to absorb the laser energy, making it hard for the lasers to work on the metal surface. The following steps introduce how to use laser marking spray:
- Apply the spray evenly across the metal surface, ensuring complete and bubble-free coverage.
- After spraying, wait for the coating to dry completely to ensure adhesion and uniformity.
- Once dried, guide the laser onto the coated surface to ablate the coating during engraving so that clear and precise marks or patterns can be generated on the surface.
One significant advantage of this method is the precise control of the engraving depth and width during the processing, contributing to effectively improving the engraving accuracy and clarity.
In addition, laser marking spray not only improves the engraving quality, but also the efficiency of laser processing of metals. Due to the improved laser absorption rate by the coating, the laser can process at a higher speed, thus shortening the processing time and improving production efficiency.
Finally, laser marking spray also has good durability and corrosion resistance, which means that the engraving effect can be maintained for a longer time, especially under proper maintenance.
2. Color laser paper
Using color laser paper is a common method for assisting in laser engraving of metals, especially applicable for scenarios requiring fast and temporary effects. The basic principle of this method is to firmly attach the color paper that is dark and able to absorb lasers, to the metal surface. When engraving, the laser beam ablates the color paper, causing physical changes to the color paper and leaving corresponding engraving marks on the metal surface, thereby achieving the expected engraving effect.
During the operation, it is first necessary to ensure that the surface of the color paper is smooth, and try to avoid bubbles and creases when pasting, to ensure that the laser can evenly act on the color paper. Then, use lasers for engraving after the color paper is attached to the metal surface. The lasers ablate the color paper by quickly rising the temperature, forming images and texts.
Although this method is simple, fast, and does not require complex equipment settings, the material and thickness of the color paper may affect the penetration and ablation effect of the laser. Moreover, color laser paper may fade or peel off after a long time. Therefore, for works that need to be preserved for a long time, it is recommended to choose a more stable engraving method.
3. Paint or marker pen
Applying a layer of dark paint or using a marker pen can increase the laser absorption rate of the metal surface, allowing the laser to effectively engrave on the metal. During the operation, it is first necessary to evenly apply paint or use a marker pen to cover the metal surface, and then carry out laser processing. The laser abates the coating and engravings will be formed. After completing the engraving, the coating can be removed by washing or wiping, leaving a clear engraving effect. However, due to the difficulty in controlling the uniformity and thickness of the coating, the precision and consistency of the engraving may not be as stable as using the laser marking spray.
Acrylic processing guide
1. Laser processing
1.1 Principles
- Processing Principle: Laser processing of acrylic (also known as plexiglass) uses high-energy laser beams to locally heat the material until it melts or vaporizes, thereby achieving cutting and engraving. The 10.6 μm CO2 laser is the most commonly used laser type for acrylic processing, as this wavelength can be well absorbed by acrylics.
- Material features:
- Optical transparency: Acrylic has excellent optical transparency, with a visible light transmission of up to 92 percent, close to that of glass. During processing with a 10.6 μm CO2 laser, it can maintain high transparency, allowing for clear and smooth cuts and engravings. However, the visible light transmissions of acrylic materials with different colors are different, which will affect the processing results.
- Absorption: Acrylics can rapidly heat up after absorbing laser energy, and then melt and vaporize, achieving cutting or engraving effect. Meanwhile, due to the different dye formulas used in the production, the absorption rate of lasers will also vary for acrylic materials of different colors. For example, white acrylics reflect most visible lights, resulting in a low absorption rate for visible light wavelength lasers, leading to poor processing effects.
1.2 Cautions
- Ventilation and smoke exhaust: Laser processing of acrylics releases harmful gases. Consequently, an effective ventilation and smoke exhaust system is required to protect operator's health and reduce smoke's impact on processing. During processing, xTool SafetyPro™ IF2 Inline Fan and xTool SafetyPro™ AP2 Air Purifier can be used together to efficiently extract smoke and gases, ensuring both processing safety and good ventilation.
- Fire safety: Acrylic may catch fire during processing, so keep the workspace clean and closely monitor the process to prevent fire hazards. You can use xTool Fire Safety Set to effectively enhance safety and reduce fire risks.
- Removal of protective film: Acrylic materials are often covered with a protective film at the factory to prevent surface scratches or damage during transportation and handling. It is recommended to remove this film before laser processing, as it may ignite during processing, causing accidental burning of the acrylic material itself.
1.3 Processing techniques
How to prevent excessive kerf and edge melting when laser cutting acrylics
- Select correct parameters
When laser cutting acrylics, choosing right parameters is key to preventing excessive kerf and edge melting. First, reduce laser power. Since acrylic is heat-sensitive, excessive laser power can cause the cutting edges to overheat, leading to material melting and a wider kerf. Therefore, selecting the appropriate power settings is crucial because appropriate laser power can provide enough energy to process the material without overheating. Secondly, increase the cutting speed. A higher cutting speed can shorten the laser’s dwell time in one area, preventing localized overheating. If the speed is too slow, heat may accumulate, increasing the risk of melting. Therefore, a reasonable increase in power and speed can effectively improve cutting quality and reduce risks of melting. - Lower laser focus
During acrylic cutting, it is recommended to adjust the laser focus to be within the material and lower the focus to reduce surface heat buildup, prevent excessive edge melting, and significantly improve cutting efficiency. - Use air assist set
When laser cutting acrylic materials, using an air assist set can effectively and significantly improve cutting quality and reduce the risk of edge melting. The air assist set sprays compressed air into the cutting area, which can rapidly dissipate heat generated during the cutting process. In this way, the temperature can be maintained within a reasonable range and overheating can be prevented, thus avoiding melting or deformation of the acrylic material and ensuring cutting edges are precise and neat.
Moreover, the laser cutting process will generate a substantial amount of particulates and smoke which, if not promptly removed, can affect the propagation of the laser beam and the cutting performance. Air assist set helps blow away these particulates and smoke from the cutting area, enhancing the accuracy of the laser beam and further improving cutting stability and precision. The air assist set reduces heat accumulation and increases cutting speed, allowing for better material penetration and enhancing overall processing efficiency.
How to process translucent or transparent acrylics with a 455 nm blue-light diode laser
- Application of light-shielding layer
To effectively engrave transparent or translucent acrylics using a 455 nm blue-light diode laser, a light-shielding layer must be applied to enhance laser absorption. The key is to choose a layer that's easy to remove and won't damage the acrylic, such as mural paint, dry-erase markers, magic markers, sidewalk chalk, or watercolors.
The color of the light-shielding layer is also significant as it will permanently transfer to acrylic. Darker colors work best, while white is the least effective.
During the preparation of acrylics, you need to peel off the protective film on one side. Then, apply the light-shielding layer as smoothly and evenly as possible until the acrylic becomes opaque. For double-sided engraving, apply the same number of layers to both sides. For single-sided engraving, the process is complete once the paint is fully dried. Check the coating's effectiveness by holding the acrylic up to the light. If areas show less paint than others, attempt to even it out. Perform the same check for double-sided engraving. Then, peel off the protective film from the other side and repeat the coating process. - Use of laser marking spray
The Laser marking spray is an effective auxiliary method similar to the application of a light-shielding layer. By evenly spraying the marking spray on the acrylic surface, the laser absorption rate of the material can be improved, helping the laser to engrave clearer marks or patterns on transparent or smooth acrylic.
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