Why do you need a compensating web-stacker?

India is the seventh largest textbook printing country in the world – industry experts have projected a growth of 18.7% in publishing/printing and 17.9% in the newspaper industry. Publishing/ printing growth in India keeps pace with the fast-growing literacy rate in the country.

The web offset technique has entrenched itself in the newspaper industry worldwide because of its efficiency and speed and its adaptability to the latest technology and attachments. All the machines are of high speed and can complete production commitments in a very short space of time (even within 8-10 hours). They are mostly used for commercial print jobs – mainly textbooks and workbooks printing – and during the down time, large print-runs of periodicals and magazines are executed.

To meet deadlines for commercial print jobs, compatible post-press machines are required, starting from web-stackers or compensating web-stackers. To what extent does the web-stacker or compensating web-stacker enhance the production capacity of a print plant?

Compensating web-stackers satisfy the demand of newspapers, magazines, retail and commercial printers for accurate performance, quality and reliability at low- to mid-speed range up to 75,000 iph. Compensating stackers produce counted, compressed and compensated stacks of high quality inserts or signatures and require minimum manpower.

Precision and quality with high output are the basic requirements of any high-speed web-offset machine. Compensating web-line stackers give alignment to the printed signature and also work as pressing stations, improving the fold and eliminating air trapping, thus producing proper stack formation.

The choice of the right post-press attachments to go with existing printing machines in the plant is crucial – The questions to be considered include:

• What are the attachments which will promote smooth and enhanced productions?
• How can the selected machines be deployed in order to enhance the production and gain on delivery time?
• What is the available space close to the press and the plant?
• What is the product flow through the existing system, including back-up?
• What is the ergonomics for the operators’ easy access, free floor space and safe environment?

Domestic manufacturers have done a great deal of R&D in devising, designing and manufacturing normal web-stackers and compensating web-line stackers and have even supplied the equipment to prominent overseas newspapers in South Africa and Nigeria, besides scores of domestic newspapers and printers.

The Government of India is encouraging domestic manufacturers and is ready to establish print clusters in partnership with the industry and provide financial support under the MSME (Micro Small and Medium Enterprises) programme. The clusters would offer common design centres, tool rooms, skill development centres, bulk buying of raw materials and modern treatment plants at low costs, with the aim of raising the quality to international standards.

Made-in-India web-stackers and compensating web-line stackers are better than machines made in many other places because of easy availability of spares and after-sales service. Also, one can custom-build the machine to individual specifications to meet production requirements and logistic considerations.

Most domestically manufactured web-stackers and compensating web-line stackers have been designed according to the unit-type principle. They prevent irregularities in folder delivery and, in the case of conveyance-stacker, gives alignment to the printed signature and works as pressing station besides improving folds and expelling air trapped during the folding process. The stackers are mobile and are built for use in different locations – meaning that the unit can be integrated quickly and flexibly by means of casters and quick connection devices.

In modern newspaper print plants, compensating web-line stackers have been integrated with mailroom system machines. Operation of the machines is based on human-machine interface system (HMI). Product sizes and stack configurations can be easily and quickly entered on the display and the operation is user friendly with complete safety for the operator.

I recall, back in 2009, during PrintPack at Pragati Maidan, a domestic manufacturer launched a Programmable Compensating Counter Stacker with inline sheet under-layer for the first time in India. The model was specially designed for web-offset machines with the speed up to 65,000 iph for 128-page tabloid or 64-page broadsheet. Sheet under-layer automatically detects the stack coming out of the counter stacker and feeds a pre-cut underlay craft sheet/ newsprint to the bottom, up to 30 stacks per minute, thus preventing the lower-most copy in a pile from getting soiled/ torn. Equipped with an audio-visual alarm system, the sheet under-layer is PLC controlled and has a man-machine interface (MMI) which makes it easy to diagnose faults and change system values.

There are compensating stackers designed for general pressroom, print finishing, or converting applications where speed, reliability, high stack quality and versatility are required. They can work directly in-line with press deliveries, rotary trimmers, or feeders at a maximum rate of 100,000 iph. High quality stacks of products are counted, compressed, compensated, and then delivered onto a belt-driven air table for further manual or automated processing.

The main features of these models are:

• Independently-driven waste divert conveyor, assuring clean transfer of waste
• Calibrated numerical readouts on upper bin and pneumatic crush roller settings
• Interfaces with delivery streams from 18-56 inches (457-1422 mm) without extra conveyors
• High-frequency stream alignment and jogging
• Reliable and accurate laser counting as standard
• High-frequency jogging in the stacking bucket on all sides
• Automatic lifting of upper belts for quick and easy jam clearance
• Quick lock swivel casters for easy movement in any direction
• Improved control for light-weight signatures
• Operator controls on all four sides of the stacker
• Self-supported air delivery table with auto detection which can be moved by one operator
• On board clock logs operating hours and drives maintenance schedule reminders
• High-visibility touch screen with easy access, easyto-understand operator controls, maintenance menus and troubleshooting
• Full 17 inches (432 mm) stack height capability
• Very fast cycle times, pre-staging of delivery table belt, bundle pusher and auto-sensing for last drop compression
• Simplified, durable guarding with wide-open access to all components
• All guards safety interlocked and enunciated on main control
• Alternating side push-out with optional second delivery table for very fast cycle times
• Full-length removable steps on both sides
• High-quality AC drive controls
• Automatic homing features on restarts

Double crush rollers with independent pressure adjustment which ensures tight fold compression for high quality stacks are unique features of the machine, besides simplified operator controls with fewer adjustment knobs.

A couple of domestic manufacturers have devised, designed and created a range of compensating web-line stackers for newspaper and commercial printers and these are integrated with tried and tested technology system drive, good performance with a speed rated at up to 65,000 products per hour.

They work directly in-line with most standard press deliveries or rotary trimmers to produce counted and compensated stacks of superior quality of inserts, or signatures with minimum manpower.

The product enters the stacker in shingled form. The divert gate is activated when there is a jam in the stacker, thus allowing the press to continue to run while the jam is cleared. Once past the divert area, the product enters the stream aligner, which ensures that the edges of the stream are perfectly uniform. The product subsequently passes through a squeeze roller which tightens the fold of the product. Precision counting of the product occurs as the next step in the process followed by forming a gap which breaks the stream into pre-selected batch quantities.

As I understand it, the best advantages of these types of compensating stackers are:

• Excellent quality stacks
• Lower skid heights and more products per skid
• Low in-feed height
• Large, satisfied customer base (newspaper mailrooms) with more efficient stuffing operation
• Reduced waste
• Operator interface panel and industry standard high speed PLC
• Simple text prompts to set counters and timers

Some of the domestically manufactured compensating web-line stackers have been designed for general pressroom, print finishing, these models can work directly in-line with press deliveries, rotary trimmers, or feeders at a speed of rated up to 65000.

The models stack a wide range of products efficiently and conveniently, as these are a combination of the latest technology and new and innovative features that allow use throughout the plant on poly wrappers, binders, inserters and mail bases, and are adjustable quickly and easily to accommodate a wide range of material from small 127x178 mm books up to full size newspapers.

Stack integrity is maintained using joggers and a receding lift table to minimize the stack-drop distance. The unique design of these models allows one to configure it to match the space requirements. Output stacks exit right, left or straight through –based on the position of the exit conveyor with no sacrifice in throughput. Changeover between exit positions is quick and easy.

Undoubtedly, the newspaper industry throughout India has gained on the production/ delivery time and diminished wastage of their product by integrating

compensating web-line stackers to their existing web machines – either manufactured domestically or imported. Most domestically manufactured models are compatible with any web-offset machine up to 75000 iph.