Diagraph's Blog

How do you Print on a Sachet or Stickpack?

By Steve Dods, Automated Labeling Products (ALP) & Thermal Transfer Overprinter (TTO) Products Manager

Sachets are packets or sealed pouches that contain liquids, gels, or powders and typically sealed on four (4) sides. Stickpacks are tube-like packaging that is sealed on two ends with a continuous seam side. These convenient packaging methods are highly utilized in the food and beverage additive markets, but can be seen in pharmaceutical as well as cosmetic industries.

This packaging type requires a specialized system to form the packaging receptacle, fill the product into the packet, and seal the ends to secure the product for transport. These systems are known as FFS, Form, Fill, and Seal machines, and they come in two different varieties. Once is Vertical, or VFFS, and the other is Horizontal, or HFFS. Vertical uses gravity to aide in the filling process, where horizontal is generally high speed by using mechanical methods for filling.

Since sachets and stick packs can be sold individually, there can be the need to print information about expiration date and lot code onto the individual products. Since it is far less accurate to accomplish this task once they are filled, due to irregularities in shape and placement control, it is done "upstream". Upstream of the fill process is where the film or web is unwound from a large roll. This is the best location to mark and code the product - before it is individualized in the process. There are many ways to accomplish this type of date / lot / id coding, but there is one that stands out amongst the rest.

In marking the products in the web matrix, there are several "lanes" of product on the master web. That means higher fill rates by handling multiple products in each indexing move through the process. A typical number of adjacent products is 5 or 6, but some are as few as 4 or as high as 12. In rare instances, lanes numbers exceeding 12 have been realized. Due to these high number of prints required at each indexing interval, traditional methods of marking are usually ruled out.

Of the possible marking methods, there are a few that have been used in practice. One is to brute force out the marking process by using multiple ink jet print heads. This is somewhat difficult to manage, as there is a requirement for non-porous ink to mark the web, which tends to have issues with the short decap time and fast dry times that can clog or require higher maintenance. Most objections from OEM FFS manufacturers and end users is the mess and chemicals in close proximity to dispensing foods and powders.

Another method is to use TTO (Thermal Transfer Overprinting) to traverse across the web to mark an indelible print using a clean ribbon method. This works, but the throughput rates suffer due to the time it takes to sweep laterally across the web each time. On the same idea, there are traversing ink jet solutions as well. They again suffer from the points above, and additionally add the time component for the sweep across the web.

The best method that eliminates the weaknesses of the aforementioned methods is the multi-lane intermittent (MLi) TTO system. The MLi incorporates a plurality of print heads to match the number of lanes requiring print. It utilizes one ribbon, to avoid multiple consumables running out at various, unsynchronized times. It is able to print very quickly, since each head can print simultaneously, each covering an area up 100 mm (across the web) x 52 mm (in the direction of web movement). Systems like these may have a slightly higher upfront price, but more than make up for it in much higher uptime and ease of use. Maintenance is fair less, and it requires little skill to perform daily operation functions, since loading a ribbon is straight forward.

Diagraph, An ITW Company is a leading manufacturer and distributor of marking, coding and labeling systems and supplies, and has been in the product identification industry for over 120 years. Diagraph’s products include all-electric printer applicator labeling systems, LINX continuous ink jet and laser coders, large character ink jet printing systems and thermal transfer overprinting systems.  For more information, call 800-722-1125, send emails to [email protected] or visit diagraph.com.