CNC engraving is a subtractive manufacturing process that uses a rotating cutting tool to precisely remove material from a workpiece, creating a desired shape or design. It is highly accurate and efficient, allowing for repeatable and precise results. CNC engraving is preferred by many industries to create parts and components with intricate details, as well as in the production of signs and decorative items.
Given the advancement of manufacturing machinery and equipment, CNC engraving is the theme that we’re going to outline here. Check out this guide to find what you need to learn for your CNC engraving work.
What Is CNC Engraving?
Engraving is a process of cutting and carving a design into a hard material surface, often done to decorate or label the object. Traditionally, this was done using a set of hand engraving tools, but now CNC (Computer Numerical Control) engraving is also available. This method uses a computer-controlled machine to carve the design and can be used for both practical and artistic purposes. It is less prone to errors and increases the speed of the process, allowing for more intricate and precise engraving.
Types of CNC Engraving Machines
Mill and Mini CNC Engraving Machines
Engraving can be done with any CNC Milling Machine. The maximum speed of the spindle is an important factor to consider when determining the suitability of a machine for engraving. As the tools used for engraving are usually small in diameter and the materials that are engraved are often softer, higher spindle speeds are necessary.
If the spindle of the milling machine is unable to achieve the required speed, it may be a good idea to invest in a sub-spindle, which will enable the machine to undertake engraving tasks more effectively.
CNC routers are machines that are typically used for engraving purposes. They are comprised of a computer-controlled cutting device that is mounted with a hand-held router for the purpose of cutting various materials. CNC routers are usually equipped with a large bed and a high speed spindle for precise and efficient engravings, typically in three-axis. Since they are not as strong as milling machines, they are more suitable for softer materials such as wood, plastic, and acrylic.
Laser Engraving Machine
Lasers can be employed for engraving in two methods. Firstly, a sufficiently powerful laser engraver can cut through the material. Secondly, even if the laser engraver does not possess the required power to cut through the material, it can still be used to discolor it with a process known as Laser Marking.
Compared to tools utilizing rotating cutters, laser engravers are generally more straightforward to use. This is because they only need an XY position, as they do not necessitate the addition of a Z axis.
Furthermore, laser beams don’t impart any force onto the workpiece, meaning that there is no need to be concerned with workholding. Often, the workpiece can simply be placed on the laser machine’s table and held in place by gravity.
Common CNC Laser Cutting Machines
- Fiber Lasers
Fiber lasers are solid-state lasers that work by producing a “seed” beam of laser light that is then amplified in specially designed glass fibers. They are more suitable for metal engraving since they are able to produce a light beam that is 100 times more concentrated than a CO2 Laser.
- Crystal Lasers
Crystal Lasers share similar applications with Fiber Lasers.
- Laser Diodes
Very low end laser engravers are commonly equipped with laser diodes that are considerably less than 5 watts in power. Since such lasers are not capable of executing a large range of tasks due to their low power level, they are mostly a novelty.
- CO2 Gas Lasers
CO2 Laser is the most widely found type of laser used in laser engraving machines. This equipment is filled with carbon dioxide gas, and is relatively affordable yet possesses high performance and quality. Therefore, they are best suited for working on materials that are not metallic.
A laser engraving machine can work with a wide variety of materials, including:
- Coated Materials: Alternately, it can be simpler to use a laser that vaporizes or changes the color of a covering. Certain coatings have been particularly designed for this reason.
- Metals: It takes a large amount of energy and in some instances, certain types of lasers run at frequencies most suitable for working with metal to facilitate metal engraving.
Requirements of Laser Power
The strength of the laser needed is based on the material and what function it will be put to. For instance, the following data can serve as a guideline for different power requirements for different material thicknesses when cutting materials like plastic and wood:
- 1/8″ thick requires 30w
- 1/4″ thick requires 40w
- 3/8″ thick requires 50 to 60w
- 1/2″ thick requires 75 to 120w
The figures provided are simply estimates. It is plausible to use a laser with lower power to cut anything of any thickness, however it will take longer than the single pass estimated by the figures.
As selecting the right power laser can be complex, it is best to speak to the manufacturer to ascertain what would be most suitable for your given application.
Learn more about CNC Laser Cutter: What You Need to Know
Laser engraving is a modern cutting technology that utilizes a focused laser beam to vaporize material from a specified area. The laser head moves systematically in order to create clean, highly detailed engravings with precision control of direction, speed, and depth.
CNC Rotary Engraving
CNC rotary engraving is a form of material removal that uses a rotary tool to engrave signs, nameplates, and different 3D figures on wood, among others. By using computerized tools, a wide array of shapes and patterns can be produced.
Electric engraving works with electrical discharge machining and welding processes. An anode made of metal is placed against the material – acting as the cathode – through which current is passed, burning the material and producing the desired engraving. This method is limited to conductive materials only.
Hand engraving is a traditional technique and requires special tools like a sharp-edged curve. This method is most suitable for delicate engravings, like those on gravestones, and is an ideal choice for intricate manual work.
CNC Engraving Tools
Three types of cutters are commonly used in CNC engraving machines, namely, engraving cutters, V-bit, ball end mills, and diamond drag bit. Each one has specific advantages in terms of performance, material, or cost.
Engraving cutters are very similar to V-bits, but are smaller, made from solid carbide, and contain a single flat-ground flute. This type of cutter is often inexpensive and delicate, but not necessarily the best choice for performance.
A V-bit is the most frequently used for engraving on wood and is composed of a steel core with brazed on carbide edges. It is available in a wide variety of tip angles to allow for the creation of the desired level of detail and width.
Ball end mills
An alternative cutter, a ball end mill, is created from a 1/32” size and is beneficial for engraving on plastic and metal. It does not have a sharp tip and is made up of two to four spiral flutes, which makes it more durable and productive than an engraving cutter. However, the engraving precision may not be as sharp.
Diamond drag bit
A diamond drag bit is a tool used for engraving which consists of a diamond-tipped point that is spring-loaded and dragged along the material without any rotation. This method is used to etch the surface of the material and it is usually used to engrave materials such as:
- Stainless steel
- Glass and ceramic
- Anodized aluminum
- Acrylic and polycarbonate
- Marble / stone / granite
Materials Available for CNC Engraving
A CNC engraving machine is ideal for cutting wood, plastics, or metal.
Wood is a soft material so it cannot provide a great level of detail, which means that you will have to engrave deeper and use thicker bits than if you were engraving metal or plastic.
You can engrave on any type of wood, but you need to make sure that the size of the engraving is larger on softer woods in order to get a satisfactory level of detail.
Learn more about our CNC Machining Wood Capabilities
Most metal materials can be engraved on a CNC machine, even if the machine is not strong enough to cut all the way through the metal block. The force required for engraving is much lower than for cutting. Common metals using CNC engraving include:
Engraving on plastic is doable, however, it is recommended to use harder plastics to ensure good results. Common harder plastics using CNC engraving include:
Softer plastics such as polyethylene and LDPE can be used but they will require more care.
It is essential to use sharp tools and adjust the speed carefully, as dull tools and slow cutting speeds can cause friction and result in melted blobs of plastic stuck on the engraving bit.
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