The Digital Revolution of Gluing Technology in Multiwall Paper Sack Production

The first W and H paper valve sack bottomer featuring digital gluing technology celebrated its world premiere at the end of October with an audience of 300 visitors in attendance.

Under the slogan THE NEXT LEVEL, engineering company Windmöller & Hölscher (W&H) and paper sack manufacturer dy-pack had invited specialists from the trade to the dy-pack multiwall factory in Wenden-Gerlingen, Germany. During live demonstrations at dy-pack's paper sack factory, the new AD^®8330 CNC valve bottomer impressively demonstrated that its innovative digital nozzle gluing technology is definitely going to revolutionize the principles of multiwall paper sack production known so far.

The World's First Bottomer with Digital Gluing System

"The extraordinary response to the announcement of this event and the great interest shown in our new AD8330 bottomer has satisfied us that our engineers have succeeded in setting another milestone in multiwall engineering history. Marking the world's first bottomer with digital gluing system, it is bound to open new perspectives and potentials to the paper sack industry", says Dr. Jürgen Vutz, CEO/W&H, following the presentation of the AD8330, expressing his firm belief that the new machine will prove a success in the time to come. As reasons for his optimism he emphasizes lower per-unit costs resulting from reduced pre-production handling requirements, shorter change-over times and a notably reduced water penetration from the glue into the paper. Less water in the sack walls – not only does it mean improved quality, but, on top of that, allows for shorter drying times and, as a result, reduced storage costs.

Traditional Bottom Gluing Systems

Traditional bottom gluing systems were based on the use of pads to apply the adhesive to the paper. This involves the availability on site of a great number of different size parts and gluing patterns, which would normally have to be changed for each new order or may require regrinding. This obviously takes time and major paste pad management requirements, facts that are bound to have a negative impact on profitability and productivity, especially in view of increasing sack size diversification, ever-smaller order volumes and resulting more frequent job changeovers. – This is where the new digital gluing system takes effect.

Gluing System Technology

In place of pads, the gluing system of the AD^®8330 uses contact nozzles guaranteeing an exactly defined glue application pattern and perfectly reliable functioning, since contact with the moving webs keeps the nozzles clear of glue build-up. In order to remain so also during production interruptions or when switching off individual glue beads for different sack dimensions or when changing the adhesive, the nozzles are automatically pivoted off or flushed with water. The core element of the gluing system is the flow regulator. It guarantees consistent glue application at all times – independent of the machine's speed and the viscosity of the adhesive. In order for the glue bead pattern to exactly match the geometry of the bottom and to ensure tight joints, the nozzle heads feature a segmented design and are separately CNC adjustable. Precise glue application is a requirement to ensure that the least necessary amount of water is introduced into the paper, resulting inbetter quality joints and reduced storage time.

Decreasing Set-up Time, While Increasing Production

Because of the use of contact nozzles, size changeover of the AD^®8330 is accomplished notably faster than previously. It is not necessary to prepare any pads for a new production job. An easy to handle graphic tool makes it easy for job management or the operator on the machine to enter sack dimensions and glue patterns, while at the same time calculating automatically the glue pattern data on the basis of the dimensions entered. Corrections, if any, can be quickly made on line. Once generated, the data sets are permanently saved and can be push-button retrieved with practically no lead time, when running repeat orders or similar specification sacks.

Not only does this minimize set-up time, but at the same reduces pre-production handling requirements. Since glue pad management is not needed any longer, production costs are reduced and potential trouble sources eliminated. Corrections in regard to geometry or glue pattern can be made any time with the machine running. Thanks to shorter set-up time, complex production processes requiring frequent changeovers will no longer impede but rather enhance the productivity of the system.

How fast the AD^®8330 adjusts to the new dimensions was impressively demonstrated during live presentation of the machine. Setting up the system for a different glue quantity and adhesive type and bringing the new glue patterns into place was completed in no time. Not less important: saleable production was demonstrably run from the very first sack, as visitors could see for themselves. Other sack samples taken during production proved that the high product quality was being maintained even during acceleration of the machine to the maximum production speed of 330 sacks per minute. Another highlight of the presentation was the demonstration of a glue pattern change with the machine in operation, accomplished on-line via the touchscreen of the PROCONTROL^®TS operator console and including changeover from full-surface to economy gluing. The same operator console had previously been used to enter the new data relative to bottom cap length, valve position, valve type and material, as well as glue application.

On-line Quality Check

For on-line quality assurance, the AD^®8330 was equipped with the high performance image evaluation system TELESCAN^®Pro, which checks the bottom geometry, the presence and position of valves and bottom caps as well as the bottom cap print for completeness, separately for each individual sack. Defective sacks are automatically removed via the reject gate of the bottomer. TELESCAN^®Pro uses colour cameras and can therefore reliably identify faults and defects even with difficult contrast conditions and colour gradations.

Flexibility

In view of increasing product diversification, the industry demands bottomers that not only provide the largest possible size ranges but, at the same time, allow for variability of sack constructions. Featuring an extraordinary size spectrum of 1:50 with filling volumes ranging from 2 to 100 litres, the AD^®8330 covers the requirements of traditional markets equally well as the needs of new niche markets demanding small size consumer packages. A broad range of hinge sleeve and valve units are available with variation possibilities from tube forming to thumb notch cutter, longitudinal seam and cross pasting, and also including an additional unwind with web break sensors as well as web tension control, allowing for customized sack constructions. As for the AD^®8330 presented at the dy-pack open house, the machine allows producing bottom caps with integrated carrying handles mainly used for off-the-shelf sale to the end user of building materials and pet food articles. State-of-the-art servo drive technology of the web draws provides automatic infinite patch length adjustment and an extended cut-off length range, when compared to the traditional change-gear concept. Standard modules or special add-on attachments that may be needed at a later stage, can be retrofitted with ease.

The Paper Sack Line

The new bottomer at dy-pack was demonstrated in conjunction with the newly developed AM^®8125 CNC universal tuber, a FLEXA^®820 end printer, TRANSYSTEMS^®automated material flow elements between the production machines, as well as an ARCOMAT^®3 robot palletizer. Another "first" featuring on the paper sack line on show was PROCONTROL^®TS as an integrative operator concept eliminating the need for separate entry of size data for each individual machine.

FLEXA^®820, the in-line printer upstream of the tuber, is equipped with four doctor blade colour decks for demanding process printing at speeds up to 350 m/min. The integrated "insetter" controller allows for subsequent addition of special print design details.

The four-ply tuber AM^®8125 CNC tuber ideally matches the AD^® 8330 bottomer in terms of output as well as degree of automation (and, therefore, in terms of set-up time as well). It is laid out for stepped as well as flush-cut applications and can also handle HDPE film as a moisture barrier. Overall venthole perforation with skip capability for all webs permits precise micro-perforation for air escape from the sacks during filling.

The two sections of the TRANSYSTEMS^®automated material flow system feature transport and storage conveyors, turning stations, lifting table, etc. They ensure constant feeding of tubes to the bottomer as well as of finished sack packets from the bottomer to the ARCOMAT^®robot palletizer. Running at 28 cycles per minute, ARCOMAT^® is the currently fastest paper sack palletizer and capable of coping with even the maximum production output of the AD^®8330 of 330 sacks per minute, without difficulty and providing perfect stacking quality.

Windmoeller & Hoelscher is an international leader in the manufacture of machinery and equipment for the flexible packaging industry. Its manufacturing program encompasses blown and cast film equipment, flexographic and gravure printing presses as well as finishing machines, industrial sack, bag and carrier bag machines as well as packaging systems working on the FFS (Form-Fill-Seal) principle, and woven film converting equipment.