Carton Overwrapping Machine

Overview

A carton overwrapping machine wraps a single carton in a sheet of clear film, folds the ends into neat diagonal corners, and heat-seals the folds so the wrap is tight, glossy and tamper-evident. This is the crisp cellophane-style wrap on a box of chocolates, a perfume carton, a deck of cards, a pharmaceutical carton or a pack of tea. Unlike shrink wrap, which is loose film tightened in a heat tunnel, an overwrap is mechanically folded to the exact carton shape and sealed flat, giving a sharper, higher-end finish with square corners.

A carton enters at the Carton Infeed, the Film Feed cuts a film sheet, the Wrapping Turret wraps the film around the carton, the Folding Section fold the ends, the Heat Sealing seals the folds, the Tear-Tape Applicator applicator adds an opening strip, and the Discharge carries the finished pack out. Everything is timed off the Frame and Base cam shaft.

Mechanical timing

The defining feature of a traditional overwrapper is that all the folders, tuckers and pushers run off one central Main Cam Shaft. Each Fold Cam times one motion so the folds happen in the correct order: side flaps first, then ends, then corners. This mechanical synchronisation is what produces the precise, repeatable corner folds at high speed. A Servo Motor drives the shaft through a Gearbox Housing, and on newer machines some folders are independently servo-driven for faster size changeover, but the cam-timed core remains the reliable heart of the machine.

The Carton Infeed gates cartons so exactly one arrives per cycle. An Infeed Belt with Flight Bar lugs spaces them evenly, an Gating Sensor confirms each is present, and the Infeed Pusher shoves the carton into the waiting film.

Film handling

The Film Feed unwinds clear overwrap film, most often biaxially oriented polypropylene for its clarity and seal, sometimes PVC or cellulose for a more traditional look and feel. The Draw Roller pair meters the precise length of film needed to wrap one carton, then the Film Knife shears the sheet. For printed film, the Registration Eye reads an eye-mark so the cut lands in the same place on the artwork every time, keeping the design centred on the pack.

Wrapping and folding

The Wrapping Turret is where the carton meets the film. The Wrap Pusher drives the carton through the cut film sheet, which drapes around the leading face, top and bottom, leaving open ends. The carton sits in a Wrap Pocket as it indexes into the folding section.

The Folding Section do the work that gives the overwrap its finish. The Side Folder plates fold the side flaps against the carton, the End Tucker folds the top and bottom flaps over the open ends, and the Corner Folder plates crease the diagonal corner folds so the ends close into neat triangles. The fold sequence and overlap are what distinguish a clean overwrap from a sloppy one, and the cam timing keeps every carton identical.

Sealing, tear tape and use

The folds are held closed by heat, not adhesive. As the wrapped carton leaves the folders it passes over the Bottom Heat Plate and between the Side Heat Shoe heated plates of the Heat Sealing, which iron the overlapped film and fuse the seal-coated layers. Temperature is held by a PID loop on the Heat Thermocouple, because too little heat leaves loose folds and too much shrinks or scorches the film.

Most consumer overwraps include a tear strip. The Tear-Tape Applicator applicator lays a narrow Tape Applicator strip onto the film before wrapping and tacks it down with the Tape Tack Heater, so the consumer can pull a clean line to open the pack. The finished cartons leave on the Discharge belt past a Cooling Fan that sets the seals firm.

The Control Cabinet cabinet holds the PLC, the Servo Drive units, and the Temperature Controller loops, with the operator setting carton size, film length and seal temperature on the HMI Touchscreen.

The machine runs 60 to 300 cartons a minute. Single-carton wrappers handle one box at a time, while collating wrappers first group several items, such as a stack of soap bars or a bundle of cartons, then wrap the group as one pack. Changeover to a new carton size means adjusting the folder plates, the wrap pocket and the film cut length, which on a cam machine is a set of mechanical adjustments and on a servo-folder machine is mostly a recipe change.

Its users are confectionery, cosmetics, pharmaceutical and tobacco packers and anyone selling a carton that benefits from a glossy, tamper-evident, square-cornered wrap. The overwrap costs more film handling than a shrink sleeve but delivers a premium look and a built-in tamper seal, which is why it remains the standard for high-value cartons. The wrap also adds a moisture and dust barrier that protects the carton and its contents through distribution, and the tear tape gives the consumer a clean first-open that signals the pack has not been disturbed. For these reasons the overwrapper sits at the finishing end of many premium packaging lines, taking filled and closed cartons and turning them into the sealed, shelf-ready unit a buyer picks up.