Shot Blasting Machine

Overview

Shot blasting is a mechanical surface cleaning and preparation process in which hardened steel shot particles (typically 0.4–3 mm diameter) are propelled at high velocity against a workpiece, fracturing and removing rust, mill scale, old paint, and other surface contaminants. The impact also induces a beneficial compressive residual stress in the surface, improving fatigue resistance. After blasting, the surface is clean, finely textured, and ready for painting or further processing.

The Blast Wheels accelerate the shot to 50–100 m/s via centrifugal force. The Work Conveyor carries parts through the Cabinet Enclosure where they are bombarded from multiple angles. The Recovery System separates the impacted shot from fine dust and recycles the shot back to the wheels. The Dust Collector filters the exhaust, and the Control & Monitoring orchestrates the entire process.

How it works

A batch of parts is loaded onto the Work Conveyor, a slow-moving belt typically running at 0.2–1 m/s. The belt carries the load into the Cabinet Enclosure, a sealed steel box lined with wear-resistant ceramic or rubber tiles to absorb shot impacts and minimize noise.

Inside, one or more Blast Wheels are already spinning at 1500–3000 rpm. The Vibration Feeder continuously meters steel shot from its hopper into the center of each impeller wheel. The shot lands in the curved blade slots of the Impeller Wheel, which accelerates it radially outward via centrifugal force. As the shot reaches the outer edge of the wheel, it flies off tangentially at 50–100 m/s, a velocity high enough to fracture rust and scale.

The shot impacts the parts on all sides, shattering and ejecting oxide layers, rust, and paint. Fine dust is generated, and the kinetic energy of the shot is absorbed and dissipated into noise and wear.

As the belt moves, the parts eventually exit the blast zone into the recovery chamber. Here, spent shot (now deformed and mixed with fine dust) falls through the Recovery System. A Magnet Separator first removes any ferrous contamination. Then a Gravity Separator, essentially an inclined chute with an air knife, blows the light dust and fines away (into the dust collector) while the heavier spent shot falls into a collection bin.

The recovered shot is not immediately reusable; it has been impacted many times and is deformed, work-hardened, and often contaminated with fine particles. A continuous Recycle Pump (a screw elevator or bucket conveyor) lifts the shot back to the Vibration Feeder hopper. Over time, as individual particles are struck repeatedly and splinter, they are continuously replaced with fresh shot added to the hopper. The cycle repeats.

Dust generated by impact and shot breakage is pulled by a Extraction Fan into the Dust Collector, a canister-style filter housing with pleated Filter Cartridge elements. As air passes through the cartridges, fine particles are captured. A Pulse Solenoid Valve periodically opens a compressed air valve, sending bursts backward through the cartridges to dislodge the collected dust into a scrap bin.

The Control & Monitoring monitors the process: a Pressure Switch on the dust collector detects when the cartridges are saturated and triggers a pulsing cycle. A Vibration Monitor on the wheel motor detects imbalance, which could indicate a feeder jam or wheel bearing wear. Shot velocity can be adjusted by changing wheel speed or shot size. Tougher coatings or heavily rusted parts require higher velocity; delicate parts or soft metals benefit from lower velocity to avoid damage.

After passing through the cabinet, parts exit clean with a textured, scale-free surface. The fine surface texture helps paint adhesion and improves the service life of painted components. Some parts are treated with a seal or rust inhibitor immediately after blasting to prevent flash rust.