Folding carton machines are an essential part of the carton board packaging production process. There are straight folder gluers for simpler designs, and tray forming machines that can handle more complex folding and gluing jobs. Heiber + Schröder's tray formers are among the most advanced in the market.
Cartons arrive at the folding carton machine from printing station. This previous stage is usually done via offset lithography, which is the most cost-effective printing method, delivering high-quality output with shorter lead time. Some packaging is printed through the gravure system although the expense of developing the cylinders only justifies it for very long runs.
In order fo the printout to become three dimensional, it must be cut following a particular shape, and the folds must be marked on the piece.
Cutting is achieved by sharp steel cutting rules that exert several tons of pressure onto the sheet, which is placed against an opposing plate where female "channels" receive the rules after cutting the carton.To crease the carton, shorter rules with rounded edges are added, pressing but not cutting in the places where it will fold.
Following the cutting step, the carton is transported to the stripping station where excess material is removed from the design. It can later be sent for recycling. As cardboard can make up to 35% of total package cost, designers must ensure that their carton layout makes the best usage of the sheet size to reduce waste.
After stripping, folding and gluing takes place. The straight line folder gluer is used, for example, in rectangular boxes. The packaging design is printed on four sides, and an extra flap is added for gluing it to the backside of the first panel. After gluing the carton is folded flat for more convenient shipping to the customer's premises.
Bottom Mounted Glue Gun System
Top Mounted Glue Guns
Tray forming machines can manufacture clamshell boxes, french fry trays, Chinese takeaway boxes, popcorn trays or pizza boxes, for example. They fall under the classification of 4-point trays, 6-point trays, and 8-point trays.
When actual product display is paramount, the design can include clear windows, which are incorporated into the carton cutting die. A specialized machine called window patcher receives the cut cartons, applies glue around the window borders while simultaneously cutting the transparent windows and presses them onto the carton.
All steps involve graphic design and production programs that ensure proper register of the design itself, cut and crease marks. Die boards are usually cut by a digitally controlled laser.
When positioning the design on the printing plate layout, the designer should use the paper grain to their advantage. Carton's fibers lie in the direction in which the sheet was produced. Placing a fold across the grain makes it more prone to re-opening and deteriorating.
In the case of rectangular boxes, cartons are sent to the customer cut, creased, folded, glued and flat. The client opens them at the plant and fills them with the product. Trays are folded, glued and stacked open, then placed in secondary packaging for the customer to use.