Thin paper behaves differently from the 100 to 350 gsm stock most offset shops handle every day. Sheets flex under the suction heads, pick up curl at the delivery, and drift out of register at speeds that feel normal for board. The press rarely needs new parts to cope with thin stock. It needs the feeder, the pile and the room set up around the paper instead of around the job that ran before it.
The adjustments below come from sheet-fed work on thin offset stock, typically in the 40 to 70 gsm range, and each one costs minutes rather than money.
Jog the Pile Evenly
Thin paper cannot be knocked the way thick stock is knocked. The pile has to be worked evenly and left flat, with the knocked sections set close together and at the same interval. Uneven knocking shows up later as creased sheets and as a pile that will not sit square in the feeder.
When the job is already waiting at the machine, knock only the trailing edge. Leave the gripper edge flat and undisturbed so the suction heads can lift the top sheet cleanly. A flat gripper edge is what keeps the feed rhythm steady from the first impression.
Lighten the Feeder Settings
Set the pressure feet lower than you would for thick stock, around 5 mm is usually enough to hold the pile without dragging at the top sheets. Back the feed wheels off until they just roll as the sheet passes underneath. Excess wheel pressure flattens the sheet against the tape, adds drag and starts the curl that later turns into a jam or a missed register.
Keep the Gripper Edge Free of Dust
Thin sheets shed dust and coating particles at the gripper edge, right where the optical sensors read the sheet. On presses with sensitive detection, KBA and Komori machines among them, that dust film causes false double-sheet stops and shutdowns that appear to come from nowhere. Wipe the area once per shift. The sensor works harder on thin stock than on board, so a dirty lens costs more production time here.
Match the Room to the Paper Store
Bring the pressroom temperature and humidity in line with the paper store before the run starts. Thin sheets take on moisture quickly, and the result is wavy edges, shrinkage across the sheet and registration that moves as the pile goes down. Air conditioning or a humidifier is the clean answer. Without either one, sprinkling the floor and airing the paper for a few hours will improve how the stock feeds and prints.
Run a Little Faster
Thin paper often runs better at a slightly higher speed. The delivery and feed systems settle into a smoother rhythm, and the sheet spends less time hanging between grippers where it can sag or flutter. As a working guide, a press rated at 10,000 sheets per hour runs thin stock at around 6,500 sheets per hour. On a 15,000 sheet per hour machine, 9,500 is a sensible setting. Push well beyond that and the pile starts to bounce.
Check Registration Early
Pull a sheet after the first few hundred impressions and check register at all four corners, not only at the guide edge. Thin stock stretches and shifts as the run warms up, and a small correction at the start costs far less than a reprint. Keep the same paper batch for the whole job where possible, since a change of batch can alter both caliper and moisture content.
None of these steps asks much of the operator. The gains come from treating thin paper as its own material with its own settings, then holding those settings for the length of the run.