Looking Into the Tunnel

As film becomes increasingly popular, shrink packers are understandably gaining importance. There are the arguments of attractive packaging at the point of sale; the issue of lowered costs, with film being less expensive than cardboard; and the environmentally-friendly aspect of less material consumption. Now, new developments are also making the process easier as well. Camera systems have opened up the shrink tunnel, making it viewable, right down to the last detail.

Viewing problems

Historically, heat-resistant curtains have kept the temperature of the shrink tunnel constant; but they have also blocked the viewing of the process. Infeed curtains are only lifted by incoming pack-formations entering the tunnel, while the outfit curtains are only raised by outgoing ready-shrunk packs.

Thus, the shrink process can only be checked from the outfeed area when the curtains are dismantled—a time-consuming and costly procedure that requires a technician.

Visual accessibility

Now ‘air curtains’ and cutting-edge camera equipment are changing all of that. Here is how it works. The air curtain uses the same principle as department-store entrances and exits. An uninterrupted flow of air circulates from the upper area of the shrink tunnel infeed and outfeed areas to the lower area of the shrink tunnel infeed and outfeed areas. The result is that an air barrier encloses the shrink tunnel, keeping the heat inside. The obvious advantage is a clear, permanent view into the shrink tunnel. An additional plus is that the pack is no longer subjected to any kind of mechanical contact. In the past, a still-warm, freshly-shrunk pack was at risk for deformation by dragging outfeed curtains. Dirty curtains could also leave unattractive streaks.

Camera equipment also allows for exact monitoring. Located between 1.50 and 2 meters from the shrink tunnel, it focuses on the critical first one-third of the shrink process where pack quality is determined. (Here, overlapping sections of film are sealed underneath each pack, inflated with hot air at controlled temperatures to initiate the shrinking process, followed by the so-called shrinking-out process.)

If problems occur in the rear section of the shrink tunnel, the camera equipment can be shifted to change the viewing angle. Therefore, the area in question can be brought into focus without delay. Up to nine heat-resistant lamps can be installed in the tunnel area to illuminate its length, while a monitor records and displays images. Thus, it is possible to respond immediately to issues in the shrink-wrap process. New settings of temperature and air feed can be quickly made.

While the camera system can remain in continuous operation, it is used primarily to check the shrink-wrap process after a format change—when new settings have been made, or if the film quality varies. The general rule is that camera monitoring is used whenever shrink-pack processing parameters are changed. The camera system can be activated and deactivated at the push of a button from the shrink-packer control panel.

Modern camera equipment systems can monitor two and three-lane operations with the same accuracy as a single-lane operation. If the shrink-pack formations are changed—for example from 12-packs to 4-packs, and therefore from two to three-lane operation—no camera-changeover work is needed.

Information integration

In the future, expect the camera equipment to make it possible to forward images of shrink packs and the shrink process directly to an equipment manufacturer, like KHS, online.

Communication between the camera equipment and a plant-information system is also conceivable. A plant information system records the operating state of a line, including the condition of the line and if individual machines are ready for retrieval. It also documents process values. Thus, links between camera equipment and a plant information system can make it possible to recall shrink processes, and to make analysis in order to draw conclusions.