Guillotine Paper Cutter

Overview

A guillotine paper cutter is the machine that turns press sheets into finished pages. Printing presses work on large sheets carrying many pages or labels; the guillotine clamps a stack of those sheets, up to about 120 mm high, several thousand sheets, and shears the whole stack in one stroke of a steel knife. Print shops measure them by cutting width (a "92" cuts 920 mm) and rely on the programmable Back Gauge to hit dimensions within ±0.1 mm across a job of hundreds of cuts.

Because a machine built to push a blade through 100 mm of paper will pass through a hand without noticing, guillotines are among the most heavily safeguarded machines in any print shop, and the Safety System system is as much a part of the design as the knife itself.

The cut

The operator jogs a stack square on the Front Table, large machines blow air through Air-Float Table Jets in the table so a 50 kg ream floats like an air-hockey puck, and pushes it back against the Back Gauge Bar. The gauge position, not the operator's eye, defines the cut size: a Servo Motor turning a Ball Screw places the fence under Encoder feedback, and the console displays position to 0.01 mm. A Cut-Line Indicator Lamp projects a light line on the stack showing exactly where the knife will land.

On the start command the Clamp Beam acts first: the hydraulic Clamp Hydraulic Cylinder drives the Clamp Pressing Beam down onto the stack just ahead of the cut line with a force set by the Clamp Pressure Valve, a few hundred daN for soft coated stock that would bruise, up to several thousand for board. Clamping squeezes the air out of the stack; an unclamped stack would shift and "draw" as the blade wedges through it, giving each sheet a slightly different size. A False Clamp Plate plate spreads the pressure on delicate work.

Only with the clamp at pressure does the knife release. The Cutting Knife is a 12–15 mm thick steel bar with a hardened cutting edge ground at 19–24°; it does not chop straight down but descends with a lateral component, the draw cut, imposed by the Crank & Pull-Rod Linkage, so the edge slices rather than crushes. The blade tip finishes its stroke inside the Cutting Stick, a sacrificial nylon strip set flush in the table, which is what lets the very last sheet sever cleanly. Operators rotate the stick to a fresh face as it grooves, and the knife itself goes out for regrinding every few thousand cuts.

Drive train

Mechanical guillotines store the cut energy in a spinning Flywheel kept up to speed by the Main Drive Motor through a Helical Gear Pair reduction. The Clutch-Brake Unit couples the flywheel to the crank for exactly one revolution and brakes the mechanism with the knife parked at top dead centre, a single-stroke architecture shared with mechanical presses. Fully hydraulic machines instead drive the knife from the Hydraulic Power Unit: a Hydraulic Gear Pump feeds 50–150 bar oil through the Solenoid Valve Block, which sequences clamp-down, knife stroke, knife return, and clamp-up. Either way the knife carrier runs in adjustable Knife Guide Gibs gibs that hold the blade on its line to within hundredths of a millimetre, and the whole shock of the cut lands in the Side Frame Castings castings.

Safety

Modern machines (EN 1010-3 in Europe, ANSI B65.5 in the US) layer several independent protections. A Type 4 light curtain, Light Curtain Emitter and Light Curtain Receiver bars with 14 mm beam resolution, guards the table opening; breaking any beam mid-stroke aborts the cut, with the clutch-brake or hydraulic dump stopping the knife in tens of milliseconds. The Two-Hand Control control requires both palm buttons pressed within half a second of each other and held for the whole stroke, guaranteeing both operator hands are occupied away from the blade. A monitored Safety Relay Module cross-checks both channels and the curtain before it will energize the clutch or valves, and detects a welded contact or shorted wire as a fault rather than a start.

Programs

The Control Console console stores cut programs: an operator enters the sequence of dimensions for a job once, and the back gauge then steps automatically to the next position after every cut, often pushing the stack forward itself. On a label job with dozens of cuts per sheet this is the difference between minutes and an hour per ream, and it removes the transcription errors that scrap whole stacks.