Screw Press for Forging

Overview

A screw press, also called a spindle press, is a die-forging machine that delivers its work as a blow rather than a slow squeeze. A Flywheel is spun up to speed, and its stored kinetic energy is driven through a Screw Spindle into the downward travel of the Ram. When the dies close on the hot part the flywheel decelerates, and the blow ends when its energy is spent. This makes the press energy-bound, not force-bound: it is rated in the energy it puts into the part, from a few kJ on small machines to over 1000 kJ on large ones, and the peak force it develops depends on how stiff the part and frame are at the moment of impact. A typical forging press of this kind runs 1.6 to 40 MN nominal force at 8 to 40 blows per minute.

Screw, nut, and flywheel

The core of the machine is the Spindle and Flywheel Assembly assembly. The Screw Spindle, usually forged 34CrNiMo6, has a large lead so that flywheel rotation turns quickly into ram descent. It runs through the Main Nut, a bronze nut fixed in the frame head that carries the full blow reaction in compression and is treated as a wear part. The Flywheel above the nut is the energy store: the larger its inertia and the higher its speed, the more energy each blow can deliver. A Thrust Bearing in the Spindle Housing takes the upward reaction during impact, and a Flywheel Brake stops and reverses the flywheel so the ram returns under control. Spindle guidance runs on Ball Bearing sets sealed by Oil Seal elements.

Ram and frame

The Ram and Slide carries the upper die and is held square to the bed by Ram Gib strips and a Linear Guide Rail pair, which matters because die forging often loads the ram off-centre and would otherwise tip it. The Upper Die Holder clamps the upper die, and a Counterbalance Cylinder cylinder pair supports the ram weight on the return. A Overload Disc sits between ram and die so that a blow landing on a cold or doubled part yields the disc instead of the screw. The whole force loop is the Frame: a Frame Head carrying the nut and flywheel, two Column members, a Bed, and four Tie Rod elements pretensioned by Tie Rod Nut hardware so the joints stay closed under impact. On a blow the frame stretches elastically and stores part of the energy, which it returns on the rebound, so the structure is built stiff and mounted on Shock Mount units that keep the shock off the floor.

Drive

The Drive comes in two forms. A direct servo press couples a large Servo Motor straight to the screw or flywheel and spins it up electrically, with an IGBT Power Module power stage and an Encoder for feedback; the blow energy is set by how far the motor accelerates the flywheel, and the same motor reverses for the return. A friction press instead runs a pair of Friction Disc wheels on a Friction Disc Shaft above the flywheel, and a Clutch Cylinder presses one disc against the flywheel rim to spin it down for the blow and the other to reverse it. The servo type is cleaner and more controllable; the friction type is simpler and long proven. The Drive Coupling and Drive Belt elements transmit the acceleration torque.

Die space, hydraulics, and lubrication

The Die Space and Ejector holds the work tooling: a Bolster raising the Die Block to height, a Die Clamp set locking the dies, and a Ejector Pin group driven by a Ejector Cylinder to lift the hot forging clear after the blow. The Hydraulic Power Unit feeds these circuits: a Hydraulic Pump supplies 200 to 250 bar, a Valve Manifold sequences clamp, counterbalance, and ejector, an Accumulator holds pressure steady, and a Pressure Sensor watches the line. The Lubrication System system meters oil to the screw thread, nut, and guides through a Lubrication Distributor and sprays die release from a Die Spray Nozzle nozzle between blows.

Control and use

The Control Cabinet cabinet houses a PLC Control and a Energy Controller module that sets flywheel spin-up so each stroke delivers the chosen energy and trims it from the measured result. The Operator HMI holds die recipes and blow counts, and power runs through a Power Supply and Relay bank wired by a Wire Bundle. Screw presses suit precision die forging of parts such as turbine blades, fasteners, valve bodies, and gear blanks, where a controlled energy blow fills deep impressions and the bottom dead centre is set by the part rather than a fixed stroke, so die wear and overload are easier to manage than on a hammer.