In the small German village of Werk Weiding about an hour’s drive from Munich is a perfect example of just what automation and machine vision inspection technology permit a food manufacturer to do.
The food manufacturer in this case is Nestlé, the world’s largest. The product is NaturNes®, a line of shelf stable meals for children. Now on store shelves for about two years, NaturNes represents a relaunch of sorts. A nearly identical product was produced in a plant in France from 1998 to 2009. But it was withdrawn until Nestlé’s packaging engineers came up with a way to better automate the way it was packaged.
What it came down to is building a better mousetrap. And boy did they.
Let’s begin with a look at the NatureNes package. It holds about 250 g of product depending on the variety—there are 20 or so, some for infants, some for toddlers—and it consists of four parts: plate, flexible lidding material, and a footed overcap with an in-mold label. Into the plate go three product components: cubed protein (chicken was in production on the day of our visit), vegetable mix (corn, carrots, peas, rice during our visit), and a sauce.
Once plates are filled and lidded, a quartet of robots places them into metal trays that fit into metal retort crates holding 425 plates each. The retort crates move automatically onto a shuttle that moves automatically to a large bank of retorts. An hour or so later, the shuttle removes the retort baskets from the cooking vessels and feeds them to secondary packaging, which is anchored by two more robots, 100% vision inspection, overcap application, and case packing on a pair of wraparound case packers.
And how many operators are required to make all this happen at an average of 180 plates/min? Just eight. A better mousetrap indeed.
Vision inspection a key
Managing much of the equipment specification and installation at the plant was Max Balhuber, whose business card succinctly identifies his title and role at Nestlé in a single word: Packaging. He points to the vision inspection system, which comes from Luceo, as one of the highlights of the sophisticated line. Luceo’s ThermoSecure L100 system examines the sealing area of 100% of the plates, and if any product contamination is detected, that plate is rejected.
“At this stage we see Luceo as the only appropriate partner for this kind of inspection,” says Balhuber. He notes that there are other suppliers offering such systems, but one thing that sets Luceo apart is the vision inspection reputation that its parent company, Tiama, has in the manufacturing of automobile glass.
According to Luceo’s Carole Besnard, Luceo makes all of its own vision inspection components and excels at all three major elements. First, the right camera and the right lighting are deployed in the image capture station. Second, the data captured by the camera is sent and processed by the best frame grabber at very high speeds. And third, the software processing the data is best in class.
In addition to determining if the seal of lidding material to tray flange is compromised, the Luceo system also singles out any pack that might have food product or sauce or other contamination on the white opaque top of the lidding. “Consumers are sensitive to such visual clues of quality, even though they have nothing to do with seal contamination or seal quality,” says Besnard.
One interesting bit of development work that had to be done jointly by Luceo and Nestlé revolved around the graphics on the flexible film lidding material. Originally the images were printed in a very dark blue. But the darkness of the ink made it difficult for the camera system to see through the blue ink for a good enough view of the plate flange to determine if there was product contamination on it or not. “So we lightened the print to a very light blue and it has resolved the problem,” says Balhuber.
Another issue still being tweaked has to do with the small flap of material in the flexible film lidding that is designed to make it easier for the consumer to peel the package open. On rare occasions this piece of material gets bent back during the retort process, so that when it later undergoes inspection the camera system will see something out of the norm and consequently will cause that package to be rejected even though there is no product contamination and the hermetic seal is perfectly good. Adjustments in software algorithms have brought this situation nearly under control, and Balhuber says he expects it to be resolved soon.
It starts upstairs
The first pieces of packaging equipment in the NatureNes line are on the floor above the filling and retorting equipment, where two custom-built systems from Del feed the plastic plates and the in-mold-labeled overcaps down to the floor below.
“We needed the overcaps to be denested into a single lane, and Del was the only supplier that seemed able to come up with a solution,” says Balhuber.
Supplied by RPC Bebo, the white plates are thermoformed from a multilayer coextrusion of PP/white PP/EVOH/whitePP/PP. The intermittent-motion, volumetric pocket filler to which the upstairs Del denester delivers the plates is a Waldner Dosomat 20. Its transport belt takes plates eight across through three filling stations. In station one is a pocket filler for cubed meat or poultry. A floor-standing hopper of the cubed meat is placed right beside this station. A bucket elevator brings the meat cubes up to a screw that extends out and over the eight-across plates. The screw distributes product to eight pockets, and when these pockets are full, their bottoms open to dispense product into the plates below.
A few feet later is station two, which operates in pretty much the same way except that it’s vegetables and rice that are being fed into the pocket filler and subsequently being deposited into the plates.
The final station on the Waldner system is where roll-fed lidding material is heat-sealed in place. Supplied by Mondi, the lidding is a multi-layer coextrusion of polyester/tie/OPA/tie/white peelable PP. “The composition of that inner layer of white polypropylene is crucial,” says Balhuber, “because we need to ensure a hermetic seal in the retort yet we want the consumer to be able to easily open the container in the home.”
Lidded plates in their eight-across orientation are picked from the Waldner transport belt by the vacuum cups of a KUKA robot. It takes 16 plates per cycle and turns 90 degrees to place the plates in two parallel conveyor lanes. A second KUKA robot uses its vacuum cup end effector to pick plates five across and two deep and put them onto an accumulation conveyor. From this accumulation conveyor, the vacuum pickup head of KUKA robot number three picks 25 plates at a time and puts them into the 25 pockets of a metal tray that sits in a metal retort crate. A fourth KUKA robot also plays a key role, though it does not touch the plates themselves. Its job is to continuously pick metal pocketed trays from a stack and place one on top of the metal pocketed tray that was just filled with plates. As soon as 17 filled metal pocketed trays are in a retort crate (425 plates per retort crate), that crate advances out of the robotic loading station and makes a 90-degree turn. Once four of these crates are in place, all four (totaling 1,700 plates) advance forward to a Kruse + Sohn shuttle that runs on a railroad track embedded in the floor. It transports the retort crates automatically to a row of retorts.
The retorts and the shuttle system were already in place when the new plastic-plate-filling line was installed. These were used formerly for producing glass jars of baby food, a packaging format still in production elsewhere at the Werk Weiding plant. Balhuber and colleagues removed one glass line to put in the new plastic plate line and kept the shuttle system and retorts right where they were. A second shuttle was added to keep pace with the new plastic plate line.
Sensors for safety
When the shuttle and its load of four retort crates reaches the retort to which the crates are assigned, all four crates are pushed automatically into the retort. Because the shuttle operates as automatically as it does, a number of sensors and light curtains from SIck are integrated into it and in the path it travels. Should someone stray into its path, an alarm is quickly sounded.
Once the shuttle has pushed its load of four retort crates into a designated retort, it also pulls from another retort four crates of product that has just been retorted. The shuttle then returns back in the direction whence it came. But this time, rather than picking up filled metal pocketed trays headed for the retorts, it feeds crates filled with pocketed trays of retorted plates to KUKA robots five and six. Robot five uses a vacuum pickup end effector to pick plates 25 at a time and put them on a conveyor belt that feeds a single-lane conveyor heading off at a right angle. As this conveyor belt advances, a vacuum cup pick-and-place system puts them five at a time on a single-lane conveyor. As for robot six, it picks just-emptied metal pocketed trays one at a time and stacks them so they can return to KUKA robot four and eventually be reloaded with freshly filled and lidded plates coming out of the Waldner filler and bound for the retorts.
Now that the plates are single-filed, they’re ready for overcapping and secondary packaging. First, however, they pass through a drier that blows off moisture. Then they pass through the Luceo ThermoSecure L100 vision inspection system. Exiting that machine, trays pass beneath a single-lane conveyor whose job is to bring the snap-fit plastic overcaps down to the packaging floor from the Del denesting system that’s on the floor above. Each plate picks up an overcap as it moves through and then an eight-station rotary Del system presses the overcaps onto the lidded plates.
A short while later, the single lane of overcapped plates is split into two so that two downstream Meypack wraparound case packers can both be fed. Special tooling on the case packers collates the plates in groups of six and stands each one up on the footed portion that is part of the plastic overcap. This produces a retail-ready look. Balhuber points out, however, that should retailers want to display the plates stacked flat and not in a vertical orientation, this can certainly be done, too.
According to Production Engineer Andreas Puschel, batches of plates can range from 15,000 to 50,000. Whenever one batch is past the Waldner machine, that system is washed down while the batch just packaged goes through retorting. When asked how challenging a task it is to keep the two halves of production—filling/sealing and batch retorting—synchronized and on schedule, he says the plant personnel have got it down pat. “The key is to be organized in the prep area with raw materials and pre-processing,” he adds.
Also essential in the installation of the new line were all the conveyor connections on which the plastic plates move from operation to operation. These were provided by JBT Corp., and that firm also played a key role in terms of integration and control.
Shelf life on the innovative package is about 12 months. This information is ink-jet printed on the sidewall of every plate by a system from Markem-Imaje.
