In an effort to increase the performance of an existing machine, the Swiss foods producer and packer Sunray, a division of Coop, converted from thermal sealing to ultrasonic sealing – with resounding success. Today, cycle times are higher by up to 33% and the percent defective has been reduced considerably.

“Since we began to use Telsonic’s ultrasonic module, we can pack critical products like baking powder with measurably higher cycle times and seal them securely,” Domink Leder insists. “The exceptional teamwork between the mechanical engineer, the ultrasonic specialist and our technical department turned the conversion to the new sealing module into a sustainably profitable business,” the final packaging section head for the Swiss Sunray went on to say.

Reduced cycle times for dusty products

The Swiss are happy with the horizontal form, fill and seal machine with rotary filler by HDG that was installed in 2006; it brought an appreciable advance in flexibility, too. This is very important for Sunray, a division of the Coop company. In the production of baking and dessert goods, which frequently alternates between pudding powder, vanilla sugar, poppy seeds or baking powder, for example, partially very dusty products are packed in three and four-side-sealed pouches, stand-up pouches or bottom-folding pouches for fill weights of both 13g and 200g. The appropriate pouch is fed accordingly.

The thermal sealing of the pouch at the top sealing seam was the limiting process. For dusty products, the cycle times had to be reduced because many packages were not sealing completely at the product-humidified sealing seam notwithstanding aspirators and skimmers.

“Instead of the possible 80 or 90 cycles we had to go to 60 to keep the rejection rate lower,” Leder recalls.

In this way the number of open pouches and unnecessarily spent packing material could indeed be reduced. However, to do so a third shift sometimes had to be arranged in order to meet the tight delivery deadlines. Moreover, in the case of particularly sugary products crystallised sugar built up on the sealing jaws and increased the cleaning expense.

Consequently, Sunray wanted to optimise the sealing down to the last seam and was hopeful when the Swiss Telsonic brought its modular technology into play. “Both machinists and packers can switch over very easily to efficient safe ultrasonics for sealing food packaging using our modular technology,” stresses Hartmut Möglich, in charge of Telsonic’s packaging department.

Autarkically operating module as a complete solution
Ultrasonics has a number of advantages compared to other sealing processes and stands out due to its great economic efficiency. With very short weld and hold times and ample seam strength immediately post-welding as well as extremely low reject rates packers achieve superior machine efficiency. In addition, ultrasonics can spot-weld with extremely high impermeability even in product-humidified seal zones and foods do not heat during the welding process.

The modularly assembled system produces high energy input in the shortest amount of time. In addition, the Telsonic welding process puts considerably less stress on the parts than conventional processes and at the same time produces greater strength. The top seal module was installed on the horizontal FFS machines in the plug-and-play mode. It functions as a standalone unit with drive and integrated pouch clamp. The autarkic module receives none but the start signal from the machine and gives a ‘finished’ signal back. Many find this modular autonomy defining.

Faster thanks to an auxiliary axis of movement

So, ultrasonic technology has brought the desired improvements. An additional mechanical demand emerged to challenge: an up and down movement was to be added to the operation of the pouch clamp. With this operation running parallel to the jaws’ opening, the range at which they can be kept open is reduced. This makes the process considerably faster.

“We’ve adapted our standard module accordingly by having installed a curve control that plays its part in achieving the required 90 cycles,” Möglich describes. Together with the movable parts’ dry guides, a clean and low-wear solution came about as a result, which has been operating reliably under full load since August 2010.

The four-side-sealed pouches are thermally sealed on three sides before reaching the rotary filler. After opening the pouch, shaping it via the ‘no-bag-no-fill’ function and then metering, the pouch is deaerated and the sealing surfaces tightened, as well as parallelly apposed. Finally, Telsonic’s top seal module ensures a secure and reliable top sealing seam employing ultrasonic technology.

A definite increase in efficiency at the top sealing seam

Thus, those 90 cycles can now be run for most packaged goods, which means 180 units per minute with the machine’s duplex design. Compared to the 80 cycles with thermal sealing, this is an increase of 12.5%. However, the greatest leap in efficiency becomes apparent in the case of baking powder and similarly dusty products.

“Instead of the earlier cycles scaled back to 60-65, today we run 80 cycles without any rejects,” Leder rejoices. Using ultrasonics that makes an increase in efficiency reaching as high as 33% on down to the last seam.