One Folder per Sheetfed Press A Revolution in Folding
By Joerg Daehnhardt, Vice President, Postpress, Heidelberg
It seems so simple: a sheetfed press yields net 12–15 thousand sheets per hour, and a typical folder can process 5–7 thousand sheets per hour (all speeds based on 16-page signatures, 8.5 × 11 in., and one folder operator). Count in some longer press makereadies and extended shifts on the
The Magazine 2 4.2017
folder and the ratio is about two to three folders per sheetfed press.
As presses have become faster and more efficient (typically adding 20–30% productivity every four years), the answer in the finishing department was simple: just add another folder (typically a legacy folder). The notion was that there have been no major performance enhancements in folding in many years.
But nothing could be further from the truth. The latest generation of portrait-fed buckle plate folders run at speeds beyond 16,000 sheets per hour and offer automated makereadies along the way.
So what has changed to enable this productivity jump of 300% in just 12 years?
The whole folder system has been redesigned. From the feeder and the folding stations to the delivery (and even the automation and sheet control systems), nothing has stayed the same. The ultimate peak productivity is achieved, even if the feeding direction is changed from the traditional portrait orientation to landscape (or oblong)
Consider some of the following key innovations within the folder:
Feeder Round-continuous versus pallet feeders, single sheet versus stream feeding. The traditional round- continuous feeder remains a mainstay in the industry. However, the operator has to regularly tend to the feeder in order to ensure continuous production. Similarly, the operator has to remove folded signatures at the delivery. This limits the maximum speed of the folder because the operator has to be present at both the feeder and delivery.
Pallet feeders rise above this limitation. The operator simply moves in the pallet and runs the folder from the delivery, enabling higher speeds and allowing more time for quality control. The latest generation of pallet feeders even allows you to stream-feed the folder, just like a sheetfed press. Stream-feeding has one key advantage: while the linear speed is kept constant, the throughput of the folder increases by up to 50%.
Folding Station Automation, stream-feeding, slitter shafts, pressing rollers. The first change in the folding station is automation, both for rollers (setting of paper thickness) and plates (for format and folding sequence set-up). The automation is most important to speed up makereadies, which is particularly impactful if many different folding schemes on different substrates have to be handled. If the folding schemes are similar but the substrates vary, roller automation might be enough. Front- and rear-mounted slitter shafts (even double) allow you to prepare the subsequent folds with perfing and scoring knives. A double slitter allows for a wider range of scoring, perfing, and slitting applications and provides additional sheet guidance. Stream-feeding
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