Finishing Up: Folding Can Be Tricky, But It’s Not Magic

Now and again I take time out to muse things over. Sometimes I think about the big issues such as “What is the meaning of life?” or “How can we achieve peace in the world?”, and sometimes I reflect on the small things like “Where did I leave my car keys?”

Recently I have been musing over a saying I heard. Attributed, I think, to Theodore Roosevelt, it went something like “Nothing in the world is worth having or worth doing unless it means effort, pain, difficulty...”

Now Teddy may be one of the most esteemed former Presidents of the USA, but it seems to me that if you can take the effort, pain, and difficulty out of a small thing, it can free up time to attend to the bigger issues. So while I’m not about to come up with a solution to all the conflicts in the world, I am able to suggest some ways that can help you take the effort, pain, and difficulty out of folding and gluing crash-lock bottom boxes. They may be small things, but they can free up more of your time for production and extra quality control and help you exploit the higher margins possible from crash-lock carton production.

The crash-lock base box is one that many printers who manufacture cartons are wary of. Many believe that folding and gluing them requires some sort of magic. Unfortunately for box makers, brand owners have a love for crash-locks because they stop the product falling out of the carton, they can be reinforced for extra strength and security, and they are ideal for use on automatic packing lines. What a lot of people don’t realize is that by making small design changes, implementing systematic set-up techniques and using the latest technology, making crash-lock cartons can be as easy as ABC - with no wizardry required.

The idea that this type of box is difficult to fold and glue has come about because there are more opportunities for things to go wrong with a crash-lock than with a straight-line box. So, running crash-locks profitably means that the operator needs a deeper knowledge of the whole box making process, especially as some of the things that go wrong can be outside of their control. For example, there could be an issue upstream with the quality of the diecutting of the box. A similar problem affecting a straight-line box may not show up on a gluer, but a crash-lock undergoes much more stress so it’s more susceptible to failure.  One simple test for upstream problems is to take a composite panel, fold it back by hand like the machine would, then fold back the 45 degree flap. If its top is not perfectly parallel with the top edge of the panel, then it’s never going to fold and glue correctly.

Taking things one step further back in the production process, design has an important role to play in ensuring efficient crash-lock production. For example a radius curve on a glue flap gives a larger area for the application of glue, which particularly helps on smaller boxes. Similarly, fishtailing can be a problem on wide, short boxes and is common on disproportionate crash-lock bottom boxes, especially those made from corrugated or litho-lam. If the designer can change the layout to incline the second crease, this will push the top edge of the glue flap against the folded inside flap, resulting in perfect alignment of both glued panels. Things like this are important if you’re to get the best performance out of your folder-gluer.

When it comes to setting crash-lock cartons to run on a folder-gluer, some people have a trial and error approach, for which there is no excuse. My colleagues in the Bobst folder-gluer team tell me that you don’t need any more blanks to set-up a crash-lock box than you do a straight-line box. Their advice is that operators just have to follow simple, and widely available, set-up procedures to master folding and gluing of crash-locks. For instance the length of the panel to be folded determines the length of the hook. If you set both the hook and the helical guide to the correct height, the carton has to fold properly. There is a simple formula in the BOBST ‘ABC of Folder-Gluer Production’ that tells you how to work it out and, with the right training, set-up of a crash-lock on a conventional folder-gluer doesn’t need to be overly difficult.

Very small, very large, or disproportionate crash-locks can be set quickly and easily with the devices available to boxmakers on modern high quality folder-gluers. With accurate feeding and good blank alignment, crash-lock production becomes much more consistent, because variations in the blanks are compensated for. Even corrugated and litho-laminated substrates should be straightforward to process if the correct techniques are followed. The key issues are still squaring and folding quality. If you use a folder-gluer with an accurate alignment device on the infeed, then you have already won half the battle.

However, even with alignment devices, the need to use mechanical hooks has placed a major restriction on the speed in which crash-locks can be produced. Equipment and processes have evolved and the technology now exists to fold and glue crash-lock cartons without hooks… and at speeds almost double that of conventional systems. This new technology has involved a complete rethinking of the way crash-locks are produced. If you follow set-up procedures on a conventional machine, you can produce crash-locks pretty efficiently, but this new technology is even easier to set; has fewer components, all of which stay on the machine; is much more tolerant of apertures and windows; and can easily add 30,000 boxes an hour to the production from a line.

Now you might think that extra speed would just highlight any problems from upstream. However, because of the way this new technology works, there is less stress put on the box and the glue flaps, so it tends to be more forgiving of problems from upstream production processes.

Of course, there is little point having all that extra speed if you can’t get the boxes packed, which is why autopackers have had to evolve alongside folder-gluers. The packing of crash-locks has traditionally been very labor intensive since the thickness variance requires inverting to balance packing. If you have much faster crash-lock production you really must have autopacking, because end of line staff simply cannot keep up if they are packing manually. This has led to the development of new autopackers that can keep pace with the new speeds possible for crash-lock carton production.

Now, if I only had a device that would take the pain and effort out of finding my car keys.