A Comprehensive Guide to Surface Sandblasting in CNC Machining

1. What Is Sandblasting?

Sandblasting is a surface treatment process that uses high-speed abrasive blasting to impact and rub against a workpiece surface. The goal is to clean the surface, remove rust, increase surface roughness, and improve coating adhesion. This process is widely used on metal, glass, ceramic, plastic, and other materials.

2. How Sandblasting Works

The basic principle of sandblasting involves using compressed air or high-pressure water to accelerate abrasive materials and blast them through a nozzle onto the surface of a part. The abrasives strike the surface at high speed, generating friction and impact, which removes contaminants, smooths or roughens the surface, depending on the application.

Common abrasives include:

• Silica sand

• Aluminum oxide

• Glass beads

• Steel shot

3. Types of Sandblasting

Depending on the equipment and technique used, sandblasting can be divided into several types:

3.1 Dry Sandblasting
Uses compressed air to shoot dry abrasive onto the surface. This is the most common method and works for most metal and non-metal materials.

3.2 Wet Sandblasting
Combines abrasive with water to reduce dust and improve surface cleanliness—ideal for environmentally controlled environments.

3.3 Vacuum Sandblasting
Utilizes a vacuum system to recycle abrasives and collect dust in a closed-loop system. This method is often used in industries requiring strict dust control, like electronics or medical device manufacturing.

3.4 Liquid Sandblasting
Abrasives are propelled using high-pressure water. This technique is especially suitable for cleaning oils, rust stains, and surface contaminants.

4. Key Parameters in Sandblasting

Several factors influence the effectiveness of sandblasting:

4.1 Type of Abrasive
Each abrasive has unique hardness, shape, and particle characteristics suited to different applications.

4.2 Grit Size
The finer the grit, the smoother the surface finish. Coarser grit provides a rougher texture for applications needing high surface adhesion.

4.3 Blast Pressure
Higher pressure increases cleaning speed but may also risk surface damage.

4.4 Blast Angle
The angle of impact affects how abrasives interact with the surface, changing the final texture and cleaning quality.

4.5 Stand-off Distance
Closer distances result in stronger impacts and quicker material removal but may cause surface over-etching if not controlled.

5. Common Abrasives & Their Applications

5.1 Silica Sand
Use: Removing rust, oxidation, and paint from metal surfaces.
Feature: Medium hardness; cost-effective and widely available.

5.2 Aluminum Oxide (Emery)
Use: Treating high-hardness materials like stainless steel or alloy components.
Feature: Extremely hard and reusable.

5.3 Glass Beads
Use: Polishing aluminum and stainless-steel components where a smooth finish is needed.
Feature: Gentle impact; ideal for delicate surfaces.

5.4 Steel Shot
Use: Heavy-duty cleaning or strengthening of cast iron and steel.
Feature: High impact force, aggressive material removal.

6. Applications of Sandblasting

6.1 Metal Surface Preparation
Used to clean, de-rust, and strip oxidation or old paint before painting or plating.

6.2 Mechanical Manufacturing
Removes burrs, weld slag, and roughens surfaces to improve adhesion or mechanical performance.

6.3 Aerospace Industry
Improves fatigue resistance and corrosion protection by treating aircraft components.

6.4 Automotive Manufacturing
Sandblasting is used on car bodies, engine parts, wheels, and chassis components for surface cleaning and prep.

6.5 Electronics & Electrical Components
Used to clean circuit boards or casings to improve plating quality and durability.

6.6 Architectural Finishes
Applies to glass, stone, or wood to achieve textured surfaces or decorative effects.

7. Advantages and Challenges

Advantages:

• Efficient Cleaning:
  Quickly removes rust, oxidation, and surface contaminants.

• Better Adhesion:
  Increases surface roughness, promoting stronger adhesion for paint, coatings, or electroplating.

• Versatile Applications:
  Suitable for a wide range of materials and industries.

Challenges:

• Dust Generation:
  Dry blasting creates heavy dust that requires protective gear and ventilation systems.

• Potential Surface Damage:
  Excessive pressure or improper abrasive selection can damage delicate surfaces.

• High Equipment Cost:
  Initial investment in sandblasting equipment and abrasive materials can be significant.

8. Conclusion

Sandblasting is a vital surface treatment method across many industrial sectors. By selecting the right abrasive, grit size, pressure, and blasting angle, you can achieve highly customized surface finishes for a variety of applications. While it comes with certain risks and costs, its efficiency and adaptability make it indispensable in industries like metalworking, aerospace, automotive, electronics, and architecture.