How to Get Rid of Burrs for CNC Machining Parts

Producing parts with high precision is critical across several industries today. Yet, even with advanced technology, machining processes often leave behind unwanted imperfections. Among these CNC machining defects are burrs. Burrs are small, sharp, or ragged projections of material that occur along the edges or surfaces of machined components. They form due to cutting, drilling, or other material removal processes and can appear in several forms depending on the method used. Removing burrs is essential for the part’s aesthetic appeal, functionality, durability, and safety.

The presence of burrs in mechanical parts poses serious concerns, especially in high-precision fields where even the smallest deviation can compromise performance. If left unchecked, burrs can cause issues like poor assembly fit, increased wear, and even safety hazards. This post dives into what burrs look like and the most effective deburring methods to eliminate them and ensure optimal part quality.

What Do Burrs Look Like?

Burrs vary in appearance depending on how they are formed, but all share the common characteristic of being unwanted excess material. In CNC machining, burrs often appear as jagged, rough, or protruding edges that detract from the clean finish of the part. Burrs can form on any material—from metals like aluminum and steel to plastics. They occur as a byproduct of cutting, milling, drilling, or grinding processes, where forces applied to the material cause deformation or fracture.

Here’s a look at some of the most common types of burrs found on machined parts:

• Rollover Burrs: These occur when the cutting tool pushes material aside rather than cleanly cutting through it. The result is a burr with a rounded edge that rolls over from the surface of the part. Although common, rollover burrs can be difficult to remove due to their rounded shape.
• Breakout Burrs: They happen when material tears or fractures as a cutting tool exits the part. This type of burr can be quite large and may require a combination of deburring techniques to remove completely.
• Poisson Burrs: These burrs form when the material flows sideways, typically occurring at the edges of a cut. They are characterized by a thin, raised ridge along the edge of the workpiece. Since they are relatively small and delicate, Poisson burrs are often easier to remove compared to other types.
• Tear Burrs: Formed during cutting operations, tear burrs have an irregular, jagged edge where the material has torn instead of being cut cleanly. These burrs are usually more pronounced and need aggressive deburring methods for removal.
• Micro-burrs: Invisible to the naked eye, micro-burrs form on precision parts and can affect functionality if not removed. They are usually addressed through polishing techniques that reach high tolerances.
• Oxide Burrs: Caused by heat during the cutting process, oxide burrs are formed when the metal oxidizes, leaving behind raised, oxidized edges. These burrs require both mechanical and chemical techniques to fully remove.

How to Get Rid of Burrs for CNC Machining Parts

The removal of burrs, known as deburring, is crucial in ensuring the functionality, safety, and durability of machined parts. If not removed, burrs can compromise the overall quality of the part by affecting fracture resistance, causing material failure, and leading to increased surface wear. Additionally, burrs can damage fasteners, cables, and other components during assembly.

Deburring improves the appearance of the part and its performance. By eliminating burrs, manufacturers can prevent unnecessary material consumption, reduce friction between moving parts, and ensure better corrosion resistance. In CNC machining, deburring is part of a broader surface finishing process, including edge breaking, graining, deslagging, and descaling.

Different forms of abrasive media are used in deburring processes, depending on the material type and desired finish. Common types of deburring media include:

• Ceramic Media: Ideal for deburring hard metals, ceramics offer various finishes at different speeds due to their high hardness.
• Plastic Media: A general-purpose medium used for deburring both ferrous and non-ferrous metals, plastics are a good option for softer materials.
• Synthetic Media: Containing up to 70% abrasives like emery or silicon carbide, synthetics are used for precision deburring, leaving smooth finishes.
• Steel Media: While expensive, steel media is highly efficient for light deburring and has a long lifespan.
• Organic Media: Made from materials like corn cob or walnuts, organic media absorbs oil and water, making it ideal for drying applications.

Deburring methods can vary based on part geometry, material, cost considerations, and production volume. Below is an extensive look at the most widely used deburring techniques.

Manual Deburring

This method involves using hand-held tools such as files, scrapers, sanders, or deburring knives. It’s a traditional and highly localized method, allowing operators to focus on specific areas without affecting the rest of the part. This technique is time-consuming but ideal for low-volume production or parts with intricate designs. Manual deburring requires a high degree of craftsmanship to achieve consistent results.

Although slow, manual deburring offers precise control, making it a preferred method for small machine shops that handle custom or prototype parts. It is also versatile, accommodating different tools to match the material and burr location. However, it may not be the most efficient method for large-scale production due to labor costs and time constraints.

Mechanical Deburring

It relies on automated equipment to streamline the process. Techniques such as tumbling, vibratory deburring, and grinding fall under this category. This method is more suitable for high-volume production as it offers speed and efficiency.

• Tumbling: A popular method for small parts, tumbling uses abrasive media inside a rotating container to rub against the workpiece, gently removing burrs. This method provides a uniform finish, especially for parts with complex geometries.
• Vibratory Deburring: In this technique, parts are placed in a vibrating container filled with abrasive media. The constant motion gently removes burrs while preserving the part’s surface integrity. It’s an efficient method for batch deburring and provides a smooth finish without excessive wear.
• Grinding and Sanding: These methods use abrasive belts, discs, or wheels to physically grind down burrs. Grinding can be aggressive, suitable for tough burrs on harder metals, while sanding is often used for softer materials.

Mechanical deburring is highly efficient for large volumes and provides a consistent finish, though it may require specialized equipment and space.

Chemical Deburring

This method of removing burrs on CNC machining parts involves immersing the machined part in a chemical solution that selectively removes burrs. It is ideal for parts with internal burrs or difficult-to-reach areas, as the chemical reacts with the burr material, dissolving it without affecting the rest of the part. 

It is particularly effective for complex shapes, hydraulics, pneumatics, and heat-treated parts. Chemical deburring ensures high precision and consistency across all parts, making it suitable for mass production. However, it requires careful handling and control of the chemicals used.

Electrolytic Deburring

Electrolytic deburring, also known as electrochemical deburring, uses electrical current to dissolve burrs on metal parts. The part serves as an anode, while a tool acts as the cathode. When submerged in an electrolyte solution, the electrical current removes burrs at a controlled rate.

This method is efficient for removing burrs in hard-to-reach places, such as holes or intersecting features. It is commonly used for rounding edges and deburring complex parts like gears and valve bodies. The main drawback is the risk of affecting dimensional accuracy if not carefully monitored.

Thermal Deburring

Also known as explosive deburring, this technique uses a controlled explosion of gases to remove burrs from multiple parts simultaneously. The process takes place inside a combustion chamber where oxygen and combustible gases burn away the burrs in seconds.

Thermal deburring is fast and effective for small, intricate parts that would otherwise require manual attention. It’s highly efficient for high-volume production, but the setup costs can be significant.

Ultrasonic Deburring

Manufacturers often use high-frequency sound waves to agitate an abrasive slurry, which in turn removes burrs from the CNC machined part. This method is best suited for precision parts with micro-burrs that are not easily visible. It is gentle and does not affect the integrity of delicate parts. However, it is less effective for larger, more visible burrs.

Waterjet Deburring

It uses high-pressure water streams to blast burrs off a part’s surface. It is ideal for delicate or intricate parts where mechanical methods might cause damage. Waterjet deburring is a fast, non-abrasive method, but it may not be as effective for thicker burrs.

Conclusion

Getting rid of burrs for is an essential aspect of the CNC machining process. It ensures that parts meet both functional and safety standards. While minimizing the occurrence of burrs during machining is ideal, complete elimination often requires additional finishing processes. There are several deburring methods, as discussed above. Automated deburring methods offer significant cost and time savings for manufacturers handling large volumes or complex parts. On the other hand, manual techniques remain invaluable for detailed craftsmanship. Choosing the right option will enhance part quality and avoid defects that compromise performance.