CNC vs Laser Engraving: Differences Explained

CNC vs Laser Engraving: Differences Explained

CNC vs Laser Engraving: Differences Explained

CNC engraving and laser engraving are subtractive manufacturing technologies. They remove material to create grooves in desired shapes and patterns.

Both techniques provide high material flexibility, and the ability to automate the process makes them ideal for large-scale production.

So, what exactly is the difference between laser engraving and CNC engraving? And which one should you choose for your application?

This article discusses the major differences between laser engraving and CNC engraving to help you select the right one for your application.

Differences between CNC Engraving and Laser Engraving

The difference between CNC engraving and laser engraving is that CNC machines use a rotating spindle with an end mill attachment that digs into the material to produce the desired engraving, while laser engravers use a high-energy laser to heat and vaporize the surface of a material to create engravings.

Difference in Method

CNC (Computer Numerical Control) engraving is a direct-contact machining process.

It is a type of CNC manufacturing process in which the material is removed by a cutting tool attached to a high RPM motorized spindle.

The cutting tool, rotating at a high speed, plunges into the material and a computer system guides its movements to create the desired engraving.

Whereas, laser engraving is a non-contact process that uses high-energy lasers to heat and vaporize the surface of a material.

In this technique, the tool does not plunge into the material, and the depth of engraving is controlled by varying various laser parameters such as laser power, engraving speed, etc.

The computer system guides the movement of the laser head to produce the required engraving pattern.

Accuracy Differences

Standard CNC machines can provide an accuracy of about 0.001” to 0.005”, whereas specialized processes like polishing provide a repeatable accuracy of 0.00005”. 

Generally, desktop Laser engravers provide an accuracy of around 0.001", whereas industrial-grade laser machines can be accurate up to 0.00005”.

Laser engravers can create high-resolution engravings with dark and light contrast areas. Hence, they are suitable for engraving photographs and other similar applications that require variable contrast.

On the other hand, CNC machines cannot produce variable contrast in the engravings, but they are ideal for deep engravings (3D engravings).

Material capability

Materials that a Diode laser can engrave
Materials that a Diode laser can engrave

CNC machines can be used to engrave almost all machinable metals like aluminum, alloy steel, low carbon steel, brass, and titanium.

It can also engrave non-metals such as wood (hardwood, softwood, and plywood), foam, plastics (acrylics, polypropylene, and polycarbonates), etc. 

Depending on the hardness and the density of the material to be worked on, the appropriate mill attachment for the CNC engraver can be used. 

Laser engravers can work on glass, wood, acrylic, leather, paper, fabric, anodized aluminum, stainless steel, brass, and silver.

The type of laser should be chosen according to the material to be worked on, eg. when working on non-metals, CO2 lasers are the best choice, whereas fiber lasers work best on metals. 

Materials, such as PVC and vinyl, emit harmful fumes when vaporized, and are therefore not recommended for laser engraving. 

However, such materials can safely be used with CNC engravers since CNC engravers don't vaporize the material. 

Furthermore, laser engravers can also be used for 3D laser engraving applications, but their performance drops drastically as the depth of the engraving increases.

Whereas CNC machines can perform comparatively deeper engravings with better speed and quality.

Therefore, when comparing CNC cutters with laser cutters, the latter performs well for material thickness under 0.5" and the former provides better output for thicker materials.

Differences in the Design Phase

The primary requirement for preparing the design is to use CAD software to create a digital model of the required part.

Modern CAD software have an in-built CAM protocol that converts the model (such as SVG file) into appropriate G-code.

After the G-code is ready, you can either use a G-code editor to tweak the program or directly upload it to begin the engraving process. 

You should have an understanding of how many axes (degree of freedom) will be needed to complete your model.

Furthermore, having good knowledge about the optimum system settings like feed rate, plunge rate, and spindle RPM for engraving the desired material plays a vital role in defining the quality of the engraving.  

Along with this, defining the correct tool path is also important.

An inefficient tool path will not only increase machining time but also affect the quality of the output.

In laser engraving, software like LaserGRBL and LightBurn can import and use various raster and vector file types like AI, PDF, SVG, DXF, PLT, PNG, JPG, GIF, and BMP. 

These files can be created using various free and paid software like Inkscape, CorelDraw, and Adobe Illustrator.

After importing the file into the layout template, you can add other desired themes, characters, or texts.

Next step is setting up the engraving area and selecting the appropriate power settings for the laser module. 

The power settings will depend on the type of material, speed, and quality of engraving required. 

Most budget-friendly laser engravers have a fixed focus. For example, if the fixed focus is 2mm, you have to adjust the height of the laser to be exactly 2mm from the material surface.  

After preparing the design and finalizing the optimal parameters, the laser engraver is ready to start working. 

Tools

CNC router end mills
CNC router end mills

The commonly used tools in CNC engraving are clamps, drill bits, end mills, face mills, reamers, gear cutters, hollow mills, thread mills, slab mills, and fly cutters. 

Whereas in laser engraving machines, the laser module is the only tool used for different applications.

These modules are available in different operational wavelengths and power ratings.

The wavelength of the laser module is generally dependent upon the type of laser being used.

CO2 lasers with a wavelength of 10600 nm is ideal for engraving non-metals, whereas the wavelength of fiber lasers (1060 nm) is ideal for engraving metals.

On the other hand, diode lasers with a wavelength of 550nm - 950nm can be used for engraving both metals and non-metals, but their low power is not suitable for vaporizing hard metals.

Accessories

Accessories used in CNC and Laser engraving
Accessories used in CNC and Laser engraving

Commonly used CNC engraver machine accessories include diamond engraving bit holder, toggle clamp, carbide cutting tools, vice, machine housing, lubrication system, cooling system, collet holders, spindle mounted duster, and suction pump. 

Since CNC machine works by removing material in the form of chips, it results in a lot of dust and debris which have to be cleaned from the work area.

A spindle-mounted dust shoe and a suction pump are used to clear away the dust and keep the work area clean. 

Moreover, the friction between the engraver and material generates heat, so a cooling system, generally liquid cooling, is required to prevent the material and cutting tool from overheating. 

On the other hand, the accessories used with a laser engraving machine comprise a rotary roller, air assist system, exhaust system, and safety goggles.  

The rotary roller provides an additional rotating axis, which will allow the laser machine to engrave on curved surfaces. 

Since laser engraving works by vaporizing the surface of a material, it generates heavy fumes which can be toxic or in-toxic, depending on the type of material being engraved.

Therefore an exhaust system is required to dispose of the smoke away from the operator and engraving area, especially when working with materials like vinyl, which emits harmful chlorine gas when vaporized.

The air assist system blows compressed air or auxiliary gas to enhance the material removal rate and keep the smoke and debris away from the focusing lens and laser beam path.

This increases efficiency and prevents the build-up of debris on the surface of the workpiece and laser optics.

Applications 

Laser engraving wood(Source: Etsy)
Laser engraving wood(Source: Etsy)

CNC engraving is used for rapid prototyping, precision engraving, deep engraving, and cutting of machine parts.

It can be used on almost all materials from metals like aluminum, brass, silver, and titanium to non-metals like acrylic, wood, plastics, and foam.

Laser engraving has its applications in engraving plaques on awards, trophies, barcode/QR on machine parts, electronic devices, medical devices, signs, and badges.

High-powered lasers can be used to produce deep engravings on various metals and non-metals.

A MOPA fiber laser can also be used to produce color laser engravings on metals like stainless steel, titanium, and aluminum.

CNC engraving provides comparatively greater material flexibility than laser engraving.

Changing the tool according to the need makes it possible to engrave almost any material on a CNC machine.

Whereas in laser engraving, a single engraver cannot be used for engraving different materials.

Hence, the laser machine should be chosen according to the material to be worked on. 

Due to the accuracy and repeatability offered by CNC machines, they are used in many industries like aerospace, automotive, defense, healthcare, and oil and gas industry. 

However, since CNC engravers work by applying constant pressure on the material, there is a possibility of material breakage.

Furthermore, typical CNC engravers are also not suitable for engraving fine patterns that require extremely high precision to handle a very thin bit without breaking it. 

On the other hand, laser engravers can be used for very intricate detailing on low density and thin materials, as the laser focus spot can have a cross-section of 0.19 x 0.16 mm or smaller. 

However, since the laser heats and vaporizes the material to create engravings, there is a possibility of edge burns if the power and speed settings are not optimized. 

Clamping

Clamping Workpiece On CNC Router Bench
Clamping workpiece on CNC router bench

CNC machines operate by delivering a high cutting force to engrave the material with a motorized spindle. So the material needs to be clamped properly. 

On the other hand, laser engraving is a non-contact process that does not deliver any mechanical force on the material and hence does not require strong equipment to clamp the material onto the workbench.

Light materials like paper and fabric need to be held in place using double-sided tape, paperweights, or magnets. 

Whereas, wood screws, double-sided tape, toggle clamps, step blocks, and vacuum clamps are some of the popular clamping tools used on a CNC engraving machine. 

Wood screws are one of the cheapest and most effective clamping tools that can be used to hold the workpiece in place.

However, it will damage the workbench and does not allow the whole surface of the workpiece to be used. 

Double-sided tape is another option, but the tape should be of high quality, else the workpiece might come off during the machining, which can be dangerous. 

Using toggle clamps is an effective way of clamping workpieces that have a uniform thickness (flat surface), but adjusting the rubber pad to accommodate a material with variable thickness (curved surface) can be complicated.

It also does not allow the whole surface of the workpiece to be engraved as the clamps cover a portion of the surface. 

Step blocks can quickly and easily clamp workpieces. However, they only work if you have a T-slot worktable or threaded insert grid. 

Vacuum pads can be used to hold the workpiece firmly on the bench. It can hold material of any thickness and is a robust clamping system.

However, the added requirement of a vacuum pump, makes it an expensive clamping system. 

Pre-processing

In CNC machines, materials should be cut into machinable sizes before they can be worked on.

Generally, it is recommended to use simulator software to ensure a safe toolpath for CNC engraving.

Whereas for laser engraving, most CAM software provide a test feature in which the laser head traces the machining pattern without turning the laser on.

Transparent or reflective materials like glass and metal should be painted or covered with masking tape before they are laser processed.

Both lasers and CNC engravers operate on the basis of the G-code generated by the CAM software.

However, you can use a G-code editor to tweak the program and ensure the safest and most efficient toolpath.

Noise

Since CNC machines use a motorized spindle to engrave on materials with direct contact, they tend to have a noise level of around 80-120 dB. 

Whereas laser engravers use a laser beam, eliminating the use of a high RPM spindle.

As a result, laser engravers are much quieter than CNC engravers.

They generally have a fully operational sound level of 60-75dB (for reference, we normally talk in the 60dB range). 

Maintenance

In CNC machines, the cutting tool engraves on material by direct contact.

This creates friction which causes wear and tears on the engraving tools, thereby requiring frequent tool sharpening or replacement.

For example, collets that are regularly used for around 8 hours a day undergo heavy wear and often require a replacement within 3 months.

Laser engraving is a non-contact process in which the material does not come in contact with the engraving tool. This lowers the maintenance of the laser engravers. 

However, a faulty or damaged laser tube can result in a costly replacement which increases the maintenance cost of a laser engraver.

Generally, laser modules have a lifetime of 10,000 to 100,000 hours depending on the type of laser and quality of the machine. 

Different CNC and Laser Engravers and Their Axis System

Multi-Axis CNC Machine
Multi-axis CNC machine

CNC engraving machines can be divided into 3-axes and multi-axis machines. 

Whereas laser engravers are categorized on the basis of the type of laser they use. 

CNC milling and turning work in 3-axes (X, Y, Z), and the cutting tool moves around the workpiece. 

Sometimes, the parts to be engraved are complex. These complex parts can be engraved using a multi-axis (4, 5, or 6-axis) CNC machine.

The 5-axes include the conventional X, Y, and Z axes along with the ability to rotate about any two of these 3 axes.  

The laser types are differentiated based on their laser source (CO2, diode, and fiber lasers) and operational wavelength. 

Most laser engravers have 3-axis movement.

X and Y-axes are controlled by the computer system to trace the path for the required engraving pattern, whereas the Z-axis controls the laser focus which may or may not be automated.

Cost Comparison- CNC engraving vs Laser engraving

The tables below mention the estimated price range of laser and CNC engraving machines along with the average running costs.

CNC EngraverPrice range ($)Average running cost ($/hour)
Desktop machine350-5k40
Benchtop machine500-10k75
Industrial 3k-150k120-200

CNC Engraving machine costs
Laser EngraverPrice range ($)Average running cost ($/hour)
Benchtop500-2k0.15-0.20
Industrial2k-200k0.25-0.5

Laser Engraving machine costs

However, these values can vary depending on factors like material being used, the complexity of the design, labor, time taken to complete the job, volume, and overheads. 

A laser engraver of similar capability can cost slightly more than a CNC engraver but provides a comparatively lower average operational cost.

Furthermore, depending on the accessories used, laser engravers can have a slightly higher overall cost than CNC engravers.

Final thoughts

CNC engravers and laser engravers have their pros and cons. Both are advanced technologies that are capable of producing far superior results than traditional engraving techniques.

CNC machines offer a higher degree of freedom than laser engravers. They can also work on a wider range of materials with adjustments in the type of cutting tools. 

In the case of laser engravers, a single laser engraver cannot be used to work on all types of materials, and therefore it is important to identify your requirement before buying a laser engraver.

Overall, a CNC engraver is ideal for engraving applications that require variable depths, such as 3D engraving, and a laser engraver is ideal for engraving applications involving intricate patterns with high resolution.

Frequently asked questions 

Why can't a single laser engraver engrave on all types of materials? 

A single laser engraver can't engrave on all types of materials because different types of lasers operate in different ranges of wavelengths. Not all wavelengths are readily absorbed by different materials and the laser type should be chosen according to the material to be worked on. For example, fiber lasers work in the 780nm to 2200nm range and are best absorbed by metals, hence fiber lasers are suitable for engraving metals.

Why are accessories like air assist systems and safety goggles needed with Laser engraving?  

Air assist systems and safety goggles are required with laser engravers because laser engraving operates by heating the surface of a material and vaporizing it. This creates engravings. The vaporization of the material results in fumes, which need to be kept away from the workpiece and laser optics to maintain the quality of engraving. Safety goggles protect your eyes from being exposed to the harmful radiation of the lasers. Most laser engraving machines have acrylic shields to filter out most of the radiation. In such cases, the goggles provide added safety. 

Can the same cutting tool engrave aluminum and titanium in a CNC engraver? 

No, the same cutting tool cannot engrave both aluminum and titanium. This is because aluminum is softer and less dense compared to titanium, which is one of the strongest metals. Hence to engrave titanium you will need special carbide-coated tools. 

About John

Hey I'm John. I talk about CNCs and Power Tools at Mellowpine. I'm a CNC hobbyist who has been making CNCs and writing about CNCs for a while. I currently also work as a consultant for business owners and hobbyists setting up their own CNCs. If you have any questions related to CNC, I'd be happy to answer them. Reach me at john@mellowpine.com

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John

Hey I'm John. I talk about CNCs and Power Tools at Mellowpine. I'm a CNC hobbyist who has been making CNCs and writing about CNCs for a while. I currently also work as a consultant for business owners and hobbyists setting up their own CNCs. If you have any questions related to CNC, I'd be happy to answer them. Reach me at john@mellowpine.com

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