Roadheader

Overview

A roadheader is a tracked tunnelling machine that mechanically excavates rock and soil by rotating a Cutting Boom Assembly armed with tungsten-carbide picks. The rotating boom sweeps across the rock face, picks chipping away fragments, and a Loading Apron Assembly collects and conveys the broken material to Material Conveyor System that stack it into an adjacent haul truck or stockpile. It is used in tunnel and underground mining work where explosive blasting is forbidden or undesirable.

The machine is often called a "continuous miner" in coal mining, a "roadheader" in hard rock tunnelling, and a "mucking machine" in soft-ground work. The fundamental principle is the same: mechanical cutting and continuous mucking (loading and hauling) of excavated material.

How it works

The operator sits in the air-cooled Operator Cabin, surrounded by all-round windows, and watches the rock face while manipulating the main control joystick. The main Track Drive & Steering are driven by two independent electric motors (fed from a high-voltage surface supply via a cable reel), one for each track, allowing the operator to steer, position, and push the machine against the face.

The Cutting Boom Assembly, anchored to the frame through a large slewing Boom Pivot Bearing, rotates 0–360° and can raise and lower independently. The boom is driven by a Boom Drive Motor coupled through a Boom Gearbox to provide controlled low-speed, high-torque rotation. As the boom rotates, the Pick Cluster, typically 12–16 clusters arranged around the boom head, attack the rock face.

Each pick cluster is a group of tungsten-carbide insert picks, identical to those used in rotary drill bits. As the boom spins slowly (0–30 rpm), each pick digs into the rock, then lifts out as it rotates past. The repetitive action fractures the rock along natural cleavage planes. The chips and fragments tumble down the Loading Apron Assembly, an inclined conveyor shelf directly under the boom.

The apron is driven by a Apron Drive Motor and Apron Gearbox, moving fragments forward and upward toward the Main Conveyor Belt. The main conveyor carries the material toward the rear or side of the machine, either into a haul truck or up a second conveyor discharge boom to a stockpile. The main conveyor is driven by a third electric motor, running at high speed (10–20 m/s belt speed) to keep up with boom output.

Rock type determines cutting efficiency. Hard rock like granite and basalt requires slower boom speed and more pick pressure (pushing the boom into the face), while softer rock allows faster rotation. The operator controls boom speed and positioning by adjusting joystick angle and pushing forward against the face with the Track Drive & Steering.

The Dust Suppression System system sprays water at the Pick Cluster and across the Loading Apron Assembly to control dust, critical in tunnels where ventilation is limited and silica dust is a health hazard. The Water Supply Tank supplies low-pressure spray Spray Nozzle around the cutting head, and a Dust Vacuum Pump may extract dust-laden air from a Dust Capture Hood enclosure over the apron.

All electrical power is supplied from surface via a long trailing cable on a reel winch. The Electrical Power & Control system onboard includes a High-Voltage Transformer to step voltage down for control circuits, motor Motor Contactor switches, and safety interlocks. Safety relays ensure that no motion is possible unless the operator presses a deadman switch, essential for underground work where a machine running loose could cause catastrophe.

Maintenance access is critical, all major components (boom motor, conveyor motors, track motors, gearboxes) are designed to be replaceable without major disassembly. Wear items (picks, apron belts, conveyor belts) are replaced regularly depending on rock type and production rate. A production roadheader can excavate 100–500 m of tunnel per month, equivalent to a small team of explosion-powered drill-and-blast mucking.