Packaging designs are often presented to production as a fait accompli. It is then up to equipment and factory engineers to figure out how to run that pack on a production line.
Coding is one aspect of the packaging workflow that is rarely taken into account when a pack is conceived - even though clear and correct batch codes, use by dates and traceability codes are essential when supplying the retail market.
Consequently, some packs are inherently awkward to code online - perhaps because the area to be coded is in a hard-to-reach corner of the pack or because handling issues make it difficult for the pack to be presented squarely and consistently to the coding device.
In both scenarios, offline coding offers an affordable and practical technology. By coding cartons, sleeves or pouches offline before they are filled, they can be brought to the production line ready printed. This has considerable advantages for code quality as coding the pack in its flat form results in a consistently clear, perfectly positioned code. Furthermore, where an online coder is struggling and creating a bottleneck, removing the process from the critical path can deliver efficiency improvements.
Sleeves: reaching the parts other coders can’t
Take, for example, cardboard sleeves, an increasingly popular format for everything from ready meals to sausages, yogurts and desserts. Sleeves can be problematic when coding online, as they have a tendency to slide out of position, which can result in codes being applied outside the target area. Added to this, when marketing departments decide where codes should be printed on sleeves, they will usually opt for a discrete position, without taking into account how practical this will be to apply.
This was the issue facing a UK prepared foods manufacturer when it contacted Rotech to enquire about an offline sleeve overprinting system. The manufacturer in question had just taken an order from one of the multiples for 3,000 units of a product that was packaged in a tub with a cardboard sleeve. The manufacturer was applying date codes using an existing inline inkjet system, but because the code was positioned in a difficult-to-reach spot at the bottom of the sleeve, the line had to be slowed down by 30% to make sure the code was applied accurately.
Essentially the coding operation had become a bottleneck because the coder was having trouble printing at an angle just a few millimetres above the conveyor; it kept mis-firing and spraying the belt rather than the product. This was not only limiting line speed, but led to packaging waste.
Rotech’s provided a RF2, standalone friction feed overprinting system for the manufacturer to code the sleeves offline and bring them to the production line already printed. RF2 uses Rotech’s stack-to-stack feeding technology to pick sleeves from a stack, print date or batch codes, and place the printed sleeve onto another stack for collection, at speeds of 400 per minute.
Pre-coding enabled the manufacturer to deactivate the inline coding system, restore line speed and code the 3,000 sleeves in a matter of minutes.
Stability issues
The design of the pack within the sleeve also determines how easy - or tricky - online coding will be. It is straightforward enough to apply best before dates and traceability codes to a four-pack of yogurts or a sleeve wrapped around a rectangular tray that is being transported past the coder via a conveyor with a good guide rail. However, with more awkwardly shaped packs, the chances of the feeding system presenting the pack and sleeve squarely to the coder can be slim. Conical sundae-style containers, for example, are inherently unstable and can easily topple over on a conveyor belt.
Pre-made pouch problems
The rise of the doy style stand-up pouch for applications ranging from dishwasher tablets to snacks and soups has presented some serious challenges for the coding operation. Some of the more structured pouch designs are not so easy to produce on a form, fill, seal machine, so for small to medium volumes, producers are buying in pre-made pouches. The downside of this is that a thermal transfer printer cannot easily be employed to print on the formed pack. There is not always an opportunity to code the pouch online before it is filled and thermal transfer printers struggle to print on anything other than flat film.
Continuous Inkjet (CIJ) is a more common technology for this application. But whilst CIJ is ideal for printing small amounts of information, such as use by dates, producers are increasingly looking to overprint large amounts of information. Overprinting information such as product names, nutritional information and ingredient lists allows them to limit their stock of pre-printed packaging film, as the same film can be used for different SKUs and geographical markets.
On the face of it, online coding may seem to be the logical way to mark a pack, but in reality, online doesn’t always equal better efficiency. If the design of the pack precludes reliable online coding, chances are that offline will prove more consistent, flexible and economical.’