Does Dalian shot blasting process affect the size of workpieces?

Dalian shot blasting is a surface treatment process mainly used to improve the surface quality of workpieces, remove oxide scales, increase surface roughness, and enhance the fatigue resistance of workpieces. Although the main purpose of shot blasting is to improve surface properties, it also has a certain impact on the size of the workpiece. The following provides a detailed analysis of the impact of shot blasting on workpiece dimensions from multiple perspectives.

1. Basic principles of shot blasting processing

Shot blasting is the process of using high-speed metal pellets (such as steel pellets, cast iron pellets, etc.) to impact the surface of a workpiece, using the impact force to remove surface impurities, oxide layers, or perform surface strengthening. Due to the impact of metal pellets on the surface of the workpiece during shot blasting, there may be slight changes in the size of the workpiece, especially in high-intensity shot blasting treatment.

2. The direct impact of shot blasting on workpiece size

(1) Removal of surface materials

Shot blasting can remove some material from the surface of the workpiece, especially when dealing with oxide scale, rust, or burrs. Although this material removal is usually minimal, it may result in small changes in size for precision or thin-walled parts. For example, for thin sheets or small parts, shot blasting treatment may result in a slight reduction in thickness.

(2) Surface deformation

During the shot blasting process, the impact of high-speed pellets may cause slight plastic deformation on the surface of the workpiece. For workpieces with low hardness or thin wall thickness, this deformation may result in slight changes in overall dimensions. For example, thin-walled pipes or thin plates may experience slight bending or uneven dimensions after shot blasting.

(3) Edge effect

In shot blasting treatment, the edges of the workpiece are usually subjected to stronger impacts, resulting in the removal or deformation of the edge material. This may cause changes in the edge dimensions of the workpiece, such as larger rounded edges or reduced edge thickness.

3. Indirect effects of shot blasting on workpiece dimensions

(1) Increase in surface roughness

Shot blasting significantly increases the surface roughness of the workpiece. Although the increase in roughness itself does not directly affect the overall size of the workpiece, in some cases, rough surfaces may affect the accuracy of subsequent processing or measurement. For example, in precision assembly, an increase in surface roughness may lead to changes in fitting dimensions.

(2) Introduction of residual stress

Shot blasting can introduce compressive stress on the surface of the workpiece, which may affect the dimensional stability of the workpiece. For example, after shot blasting treatment, the workpiece may undergo slight deformation due to the release of residual stress, resulting in dimensional changes.

(3) Thermal effect

Although shot blasting is a cold working process, local temperature rise may occur on the surface of the workpiece under high-speed impact. Although this temperature rise is small, it may cause thermal expansion or small changes in size for certain materials or precision workpieces.

4. Factors affecting the size of shot blasting processing

(1) Workpiece material

Different materials have different responses to shot blasting processing. For example, materials with lower hardness (such as aluminum and copper) are more prone to dimensional changes due to shot blasting, while high hardness materials (such as quenched steel) are relatively stable.

(2) Shot blasting parameters

The intensity, particle size, ejection speed, and time of shot blasting all affect the size of the workpiece. High intensity or prolonged shot blasting treatment is more likely to cause dimensional changes.

(3) Shape and size of workpiece

Thin walled parts, small components, or workpieces with complex shapes are more prone to dimensional changes due to shot blasting, while large or thick walled workpieces are relatively stable.

(4) Accuracy of shot blasting equipment

The accuracy and uniformity of shot blasting equipment can also affect the size of the workpiece. If the shot blasting is uneven, it may cause local dimensional changes in the workpiece.

5. How to reduce the impact of shot blasting on size

To reduce the impact of shot blasting on workpiece size, the following measures can be taken:

Optimize shot blasting parameters: Select the appropriate shot blasting intensity, particle size, and time based on the workpiece material and size.

Control shot blasting uniformity: Ensure even shot blasting treatment and avoid excessive local impact.

Choose appropriate workpiece design: For precision workpieces, a certain amount of machining allowance can be reserved during design to offset the size changes that may be caused by shot blasting.

Follow up processing: Conduct size inspection and necessary adjustments after shot blasting to ensure that the workpiece size meets the requirements.

6. Precautions in practical applications

In actual production, the impact of shot blasting on workpiece size is usually small, but special attention still needs to be paid to precision parts or workpieces with high precision requirements. For example, in the fields of aerospace, automotive manufacturing, or medical equipment, the dimensional changes after shot blasting may affect the performance and assembly accuracy of the workpiece. Therefore, in these fields, shot blasting usually requires strict process validation and dimensional inspection.

The impact of shot blasting on the size of workpieces is mainly reflected in the removal of surface materials, small deformations, and edge effects. Although this impact is usually small, special attention should still be paid to precision or thin-walled parts. By optimizing shot blasting parameters, controlling process conditions, and conducting subsequent inspections, the impact of shot blasting on workpiece size can be effectively reduced, ensuring the dimensional accuracy and performance requirements of the workpiece.