The four fundamental elements that influence laser engraving are: engraving speed, laser power, engraving accuracy and material.
To achieve a certain engraving effect on a specific material, it is necessary to absorb a certain level of laser energy. This energy must be considered as the laser energy absorbed by the material = laser power/writing speed.
Simply put, to increase the laser energy absorbed by the material, you must increase the laser power or decrease the recording speed.
The method to adopt depends on the material and the final effect of the recording. Generally, users avoid high and low speeds as they reduce production efficiency.
Not only is recording efficiency affected by speed, but recording accuracy also has a significant impact.
From our practical experience, the difference between objects recorded at 500 dpi and 600 dpi is negligible to the naked eye, but the time consumed differs by about 20-30%.
Under normal circumstances, users use 500 dpi to complete most tasks and only use settings of 600 dpi or higher for cropping or when high-density power is required.
Therefore, the recording material probably has the most decisive impact on the final effect of the recording. New users often have a limited understanding of the characteristics of materials and do not have an in-depth understanding of the recording performance of different materials, which may inevitably cause some losses to customers.
Below, I will introduce some commonly used recording materials and their recording performance methods for your reference:
I . Grayscale representation
Conventional mechanical recording cannot economically record dots of different sizes and therefore lacks grayscale representation.
Laser engraving, obtained through matrix engraving, naturally stands out in the grayscale representation. Therefore, grayscale can be widely used in recording design.
This approach not only reduces the coloring process, saving costs, but also enriches engraving reproduction methods, adding depth to graphics.
When users use this, they first fill different gray scales in the graphic (text must be converted to graphic), select black and white mode for recording output, and can experience the effects of different point sizes, with precision usually not exceeding 500 dpi.
II. Recording Materials
1. Wood
A. Raw Wood (Unprocessed Wood)
Wood is the most used material for laser processing to date, as it is easy to engrave and cut. Light-colored woods such as birch, cherry or maple can be effectively vaporized by the laser, making them suitable for engraving.
Each type of wood has unique characteristics; some are denser, like hardwoods, and require higher laser power for engraving or cutting.
We recommend studying the engraving characteristics of unfamiliar woods before engraving.
B. Plywood
Sometimes customers may request engraving on plywood, which is not significantly different from engraving on wood, but it is important to avoid engraving too deeply.
The edges of cut plywood will darken like wood, with the key factor being the type of wood used in the plywood.
C. Wood cutting
Laser engraving machines typically do not cut deeply into wood, usually less than 5mm, due to the lower laser power. Decreasing the cutting speed may result in wood combustion.
In specific operations, it may be worth trying to use a large objective lens and employ a repeated cropping method.
D. Coloring
Wood often has a burnt sensation after engraving, which when combined with the natural color of the wood, creates a pristine artistic beauty. Color depth mainly depends on laser power and recording speed.
However, some types of wood, usually those with smoother textures, cannot change color no matter what you do (e.g. birch). Sometimes customers may ask you to paint the finished product, in which case acrylic paint may be used.
2. Density Overlay Panels
A. Common Density Overlay Panels
This type of panel, often used to make sign backplates, consists of high-density boards covered with a thin layer of wood fiber. Lasers can engrave this material, but the resulting pattern is uneven in color and tends to darken.
Usually needs coloring. You can usually get better results by learning proper design techniques and using a 0.5mm two-tone plate for inlay.
B. Laser-Specific Density Overlay Panels
Some density plates are specifically designed for laser engraving, producing uniform color patterns without the need for additional coloring to achieve a good effect.
C. Cleaning
The surface of the density plate can be cleaned with a damp cloth after engraving.
D. Coloring
You can use acrylic paint or alkyd paint. During engraving, the graphic color can be set to 60% gray to create a slightly rough bottom surface, improving color adhesion.
3. Acrylic (a type of plexiglass)
A. Acrylic
Acrylic is the second most used engraving material after wood. It is easily cut and engraved, comes in a variety of shapes and sizes, and is relatively affordable.
Plexiglass is produced in two ways: casting and extrusion. Laser engraving mainly uses cast plexiglass as it creates a very white ice effect after engraving, providing a strong contrast to its original transparent texture.
On the other hand, extruded plexiglass remains transparent after laser engraving, providing insufficient contrast. When purchasing plexiglass, insist on high-purity types from the dealer, otherwise the material may melt during the engraving or cutting process.
B. Engraving
Generally, plexiglass is back-etched, meaning engraved from the front and viewed from the back, giving the finished product a more three-dimensional feel.
When recording, mirror the image first by selecting high speed and low power settings. If the power is too high during recording, irregular streaks may appear at the bottom.
If you want to record more deeply, try recording several times. When coloring specific parts in a post-etching situation, etch the coloring area more deeply first, then polish with a flame polisher before applying color.
Without this polishing step, the color seen from the front will not be uniform.
C. Cut
Plexiglass is relatively easy to cut. If the customer's requirement is not high, the cut parts can be delivered immediately after cutting, without the need for flame polishing.
However, if flame polishing is necessary, use a blowing device during cutting to improve the quality of the cut. When cutting plexiglass thicker than 8mm, switch to a larger lens.
Note: Operators must not leave during the cutting process as flames may occur.
D. Cleaning
Use acrylic paint, as other paints can damage the smoothness of the plexiglass.
4. Two-color sheets
A. Two-color sheets
Bi-color sheets are a type of engineering plastic used for engraving, consisting of two or more layers of colors. The standard size is usually 600mm x 1200mm, with some brands offering a smaller size of 600mm x 900mm.
Two-color embossed sheets are often used for various signs and badges because of their uniform color, clear patterns and durability.
They are broadly divided into two categories, mechanical and laser, with some mechanical plates also suitable for laser engraving.
The characteristic of laser engraving sheets is that the surface color layer is thin (<0.1mm) and the whole sheet is a little thinner than mechanical sheets (laser sheets are generally 1.3mm and 0.8mm, mechanical sheets are generally 1.5mm).
When purchasing two-tone sheets, if you are unsure about their suitability for laser machines, it is advisable to consult your dealer or test a small piece first.
From our experience, if the surface color of the sheet is very thin, it can generally be laser engraved. If the surface color is thicker, consider engraving twice.
B. Engraving
If a laser sheet is used, the engraving results will be very good, with sharp contrasts and edges. When using a mechanical plate with a fine surface, the engraving effect is not much different from a laser plate, although the edges may not be as sharp upon closer inspection.
It is generally not advisable to use mechanical plates with a thicker surface, as it would be necessary to reduce the laser power and engrave repeatedly to clean the background, and the end result may not be very good.
On two-color sheets with high contrast (such as black and white), you can draw images engraved in shades of gray.
After a large amount of embossing, the two-color sheet itself may deform slightly. This can be fixed by heating it with hot water and straightening it manually.
C. Cut
In general, customers will ask you to cut bicolor sheets. If you are using a laser sheet, you can cut it after engraving. Be careful not to cut too slowly or cut all at once; It's best to do this in three or four steps.
This way, the cut edges of the material will be smooth and without traces of melting. The power used during the engraving process must be correct – not too high to avoid traces of melting.
If a mechanical sheet is used, it can only be cut to a depth of 50% and then manually broken and the edge sanded until smooth. If the customer has a mechanical machine, the sheet can be cut first and then moved to the laser machine for engraving.
D. Cleaning
After engraving, the surface can be cleaned with a damp cloth or alcohol.
However, be aware that if the laser power is too high during engraving, a hard-to-remove layer of soot may adhere to the surface of the two-color sheet.
E. Coloring
If the customer's requirements are not high, dot patterns can be used to represent different colors in the logo. If staining is required, the staining area must be engraved more deeply.
Acrylic paints or alkyd enamels can be used, as other types of paint can damage the smooth surface of the two-tone sheet.
5. Glass
A. Laser engraving on glass
Lasers can perform surface engraving on glass, although the depth of engraving is limited and cutting is not possible.
Typically, lasers can create a frosted or shattered effect on the glass surface.
Users generally prefer a matte effect to a broken effect. This mainly depends on the texture and uniform hardness of the workpiece.
B. Recording Process
Controlling glass etching can be a challenge. To achieve a smooth, matte surface, follow these steps: Apply some cleaning solution to the area to be engraved.
Cut a piece of newspaper or napkin slightly larger than the engraved area. Wet the paper well with water, squeezing out excess moisture. Then, place the damp paper over the engraving area, avoiding creases.
Place the glass in the engraving machine and engrave while the paper is still damp.
Then remove the glass, wipe off the paper residue and clean the glass surface. If necessary, gently polish the glass surface with 3M Scotch-Brite.
Typically, the laser power should be lower, the accuracy set at 300 dpi, and the engraving speed should be higher. You can try using larger lenses for recording.
Note: When engraving leaded crystal with a laser, extra care must be taken.
Leaded crystal has a different coefficient of expansion than regular crystal, which may cause it to crack or shatter during engraving. Lower power settings can avoid this problem, but it's crucial to be prepared for potential breakdowns.
C. Combining Laser Engraving with Sandblasting
Laser engraving machines can replace lettering machines, directly cutting protective glass films with sandblasting. This process eliminates the protective film transfer step, saving time and improving the quality of the final product.
D. Cleaning
After engraving, the surface can be cleaned with a damp cloth.
E. Staining
Acrylic paint can be used for coloring.
6. Paint coated copper plate
A. Paint coated copper plate
Typically, copper cannot be laser engraved. However, there is now a material available with a special paint on its surface that can be completely vaporized by a laser, exposing the underlying copper plate.
Manufacturers usually polish or specially treat the copper plate before coating it to ensure that the exposed area after engraving is smooth enough and can be preserved for a long time.
If the copper surface is not treated, a protective film must be applied after engraving to prevent surface oxidation and dirt over time.
B. Engraving
Generally, you can use low power consumption, high speed, and accuracy settings above 500 dpi.
C. Cleaning
After engraving, you can clean the surface with a damp cloth or alcohol.
D. Coloring
If user requirements are not high, halftones can be used to represent different colors in the logo. If coloring is necessary, acrylic paint can be used, as other paints may affect the smoothness of the surface of the copper plate.
