Forging Roll Machine

Overview

A forging roll machine, also called a reducer roll or roll forging machine, shapes a hot billet by passing it between two counter-rotating rolls that carry shaped die segments. The dies cover only part of each roll's circumference, so the gap opens once per revolution to admit the billet and closes to roll it. As the gripped end is pushed in, the closing dies bite and draw the billet through, spreading and lengthening it while reducing the cross-section. The machine does not finish a part on its own; it produces a preform whose mass is distributed along the length to suit the next die-forging step, typically on a press or hammer. Roll forging is common for connecting rods, axle beams, crankshaft blanks, hand tools, and turbine blade preforms, where moving metal ahead of the final forging cuts press tonnage and saves material.

Roll stand and dies

The heart of the machine is the Roll Stand, a pair of Roll Shaft units held in heavy Stand Housing castings. Each shaft carries one or more Die Segment blocks bolted around part of its circumference and locked by a Die Clamp. Because the segments span only a sector of the turn, the rest of the rotation leaves the gap open so the billet can enter freely. A row of grooves side by side lets the operator move the billet from one pass to the next, taking it down in steps. The Screw-Down Unit sets the gap and so fixes the section each pass leaves, while the Thrust Block absorbs the axial load from any asymmetry in the grooves. The roll necks run in Ball Bearing sets sealed by Oil Seal elements against scale and spray.

Drive train

Rolling a hot billet draws a large but intermittent torque, because the dies engage only part of each turn. The Drive Train handles this with a Main Drive Motor of 75 to 400 kW backed by a Flywheel that stores energy between bites and keeps roll speed steady through the stroke. A Pinion Stand splits the drive into two equal outputs so both rolls turn at the same surface speed and stay in phase, which matters because the upper and lower die segments must meet the billet at the same instant. Drive reaches each roll through a Spindle Coupling and a universal-joint Drive Spindle that allows the gap to change without binding. A Helical Gear Pair in a Gearbox Housing sets the reduction, and an Encoder on each roll reports angular position to the control so the manipulator can time billet entry to the open gap.

Manipulator and handling

The billet is held by the Billet Manipulator, whose water-cooled Gripping Tongs grip the cool tail while the hot end is presented to the rolls. The Tong Arm keeps the part in line with the chosen pass, and the Traverse Slide advances and retracts it and shifts it sideways to the next groove. Between passes the Billet Rotator turns the billet about its own axis so the section is worked evenly all the way around, which is what produces a clean round or oval preform rather than a flattened one. The Grip Cylinder closes the tongs hard enough to resist the pull-out drag as the rolls draw the billet in, and a Pressure Sensor confirms the grip is holding. On automated lines the slide runs on a Linear Guide Rail pair driven by a Servo Motor.

Lubrication, cooling, and hydraulics

Hot forging is hard on dies, so the Die Lubrication and Cooling system sprays a graphite or water-based release agent from a Spray Header onto each die segment as it rotates past, between billets. The Lubricant Pump meters it from an agitated Lubricant Mix Tank, and a Roll Coolant Circuit circuit pulls heat from the rolls so the die grooves keep their hardness. The Scale Blow-Off clears furnace scale off the billet before it can roll into the surface. The Hydraulic Power Unit feeds the grip and traverse cylinders: a Hydraulic Pump supplies 160 to 210 bar, a Valve Manifold sequences the motions, an Accumulator steadies pressure, and the Oil Cooler holds oil temperature down near the hot stand.

Control and integration

The Control Cabinet cabinet houses a PLC/CNC Control that ties roll angular position to manipulator advance, so the billet end enters at the moment the die segment opens the gap. The Operator HMI holds pass schedules, spray timing, and roll-gap recipes per part number, and a Drive Module feeds the main and servo motors. Power runs through a Power Supply, an IGBT Power Module stage, and a Relay bank, all wired by a Wire Bundle to a Connector panel. The whole stand sits on the Guarding and Base base, where a Scale Chute carries away scale and offcuts and Guard Panels shield operators from spray and the rotating dies.

Materials and use

Rolls and shafts are forged alloy steel such as 34CrNiMo6, while die segments are hot-work tool steel like H13 or 5CrNiMo hardened to resist the heat and abrasion of repeated hot contact. Billets enter at 1050 to 1250 deg C for carbon and alloy steels, lower for aluminium and copper alloys. A single machine may carry two to six grooves across its width, taking a part down in steps with up to about 40 percent area reduction per pass. Roll forging suits medium and high volume preforms where the saving in downstream press tonnage and stock weight repays the tooling, and it is often the first station on an automated forging line feeding a Billet Manipulator handoff to a press.