The Shot Blasting Cleaning Process For Loader Buckets

The shot blasting cleaning process for loader buckets
Loader buckets are large, irregularly shaped, high-strength welded structural components. Their surfaces are covered with a large amount of welding slag, oxide scale, rust, and the cutting edge areas need to be strengthened simultaneously. The complete shot blasting cleaning process is as follows:
1. Preparatory work: Equipment selection and pre-treatment
1.1 Selecting the appropriate shot blasting machine
Opt for a large-tonnage double-hoist type shot blasting machine (for batch production, a through-type hoist shot blasting machine can be selected):
The hoist load should be ≥ 1.2 times the weight of the bucket (for a 5-ton loader bucket, the single weight is 1-2 tons, choose a 5-ton hoist). The size of the shot blasting chamber should be larger than the maximum size of the bucket by 15% or more to ensure a distance of 0.75-1.5 meters between the workpiece and the shot blasting machine, avoiding collisions or insufficient throwing distance.
The hoist should be capable of 360° self-rotation and be equipped with ≥ 6 shot blasting devices to cover the inner cavity, weld seams, cutting edges and other blind areas of the bucket.
1.2 Pre-treatment of the workpiece (key quality control points)
Defect pre-grinding: Manual grinding to remove > 1mm weld spurs and welding splashes - large protrusions will cause the shot to rebound, resulting in uneven surface pitting and cannot be removed directly by shot blasting.
Seal the holes: Use rubber plugs to seal the pin shaft holes, thread holes, and process holes to prevent the shot from embedding and affecting subsequent assembly.
Center finding: Mark the center position of the bucket, ensure balance when hoisting to avoid shaking and collision during shot blasting.
2. Core shot blasting operation process and parameter settings
1.1 Standard operation sequence (cannot be reversed)
Start-up: Start the dust removal system → Start the elevator → Start the separator → Start the shot blasting machines one by one → Start the hoist self-rotation → Open the pellet supply valve
Operation: The hoist drives the bucket into the shot blasting chamber and continuously rotates and throws
Stop: Close the pellet supply valve → Stop the shot blasting machines → The hoist continues to self-rotate for 1 minute (to empty the remaining pellets) → Stop the elevator/seperator → Delay-stop the dust removal system
2. Precise setting of process parameters (adapted for high-strength steel loader buckets)
Shot selection: S330 alloy steel pellets (diameter 0.8-1.2mm), balancing cleaning efficiency and coating roughness, prohibit the use of steel wire cut pellets (which can cause excessive surface roughness)
Shot blasting machine rotation speed: 2500-2800rpm
Hoist self-rotation speed: 3-5r/min, ensuring uniform impact on all surfaces, and the blind areas can pause and adjust the hoist suspension angle during the shot blasting process
Shot blasting time: 5-8 minutes, for severely rusted old buckets extend to 10 minutes, for newly welded buckets 5 minutes is sufficient
Dust removal negative pressure: -15~-20Pa, to avoid dust spillage and ensure the shot blasting separation effect
3. Post-processing and quality acceptance
1. Post-processing procedures
Residual pellet cleaning: Use 0.6-0.8MPa compressed air to blow the inner cavity, weld seams, and blind areas of the bucket to completely remove embedded pellets;
Re-work for uncleaned local welds and blind areas:定点 re-blasting for the uncleaned local welds and blind areas;
Surface inspection： Confirm no shot residue before transferring to the coating process.
2. Quality acceptance standards
Cleanliness： Reach Sa2.5 grade (near-white grade) - no visible oxide scale, welding spurs, or rust on the surface, exposing a uniform metallic color;
Roughness： Surface roughness controlled at Ra20-30μm, ensuring the subsequent coating adhesion reaches ISO 1 grade;
No embedded pellets： No pellets remaining in all holes and gaps, not affecting subsequent assembly.