Problems of insufficient or uneven surface roughness after shot blasting
The core reason for insufficient or uneven surface roughness after shot blasting is the inconsistency between shot blasting energy and coverage. The following are specific troubleshooting and adjustment solutions:
Insufficient Roughness (Overall Too Smooth)
This reduces coating adhesion and can be addressed in three main ways:
Increase steel shot size: Small steel shot lacks impact force. For high roughness requirements, select steel shot larger than 1.0mm (such as S330 or coarser).
Increase blasting speed: Check if the blasting head speed has decreased, or adjust the shot blasting flow valve to increase the initial velocity of the steel shot.
Replace with high-hardness steel shot: If the steel shot is worn and rounded or has low hardness, it needs to be replaced (e.g., cast steel shot HRC 40-50).
Extend shot blasting time: Ensure complete coverage and avoid "under-blasting" due to insufficient processing time.
Uneven Roughness
This manifests as uneven surface roughness on the same workpiece, with some areas being rough and others smooth. Common causes and solutions include:
Thunderbolt Angle and Blind Zones: Adjust the direction of the blasting head to ensure the steel shot impacts the surface at a 30-70 degree angle. If necessary, increase the number of blasting heads or perform manual supplementary blasting.
Workpiece Obstruction: Improve the hanging or tooling fixtures to ensure the steel shot hits all areas, avoiding "shadow zones" on the workpiece.
Uneven Steel Shot Flow: Check for blockages in the blasting head's feed cup or control valve, ensuring a stable feed to each blasting head.
Equipment Wear: Inspect and replace worn directional sleeves and blades; otherwise, the blasting band will be disrupted, leading to insufficient energy in certain areas.
Special Cases and Quick Troubleshooting
Ineffective Old Steel Shot: If the steel shot contains too much debris (particle size <0.3mm) or dust, immediately turn on the separator or replace with new steel shot.
Thin-walled part vibration: Reinforce workpiece clamping to prevent uneven impact caused by vibration during shot blasting.
Adjustment parameter reference:
For a surface roughness of Ra 6.3-12.5µm: S330 (1.0mm) cast steel shot is recommended at a speed of 70-80m/s.
For a surface roughness of Ra 3.2-6.3µm: S230 (0.7mm) cast steel shot is recommended at a speed of 60-70m/s.