Machine manufacturer also contract packs

When a company introduces a new packaging concept, even if it's only new to itself, it is always a scary prospect, particularly for the individual in charge of the project. This is speaking from experience, because I was project engineer for a number of new packaging concepts at Kraft Foods in the '60s and '70s, including the first bulk-glass line for mayonnaise (running 600 qt/min) and the first continuous-motion machines to produce single-serve pouches of a wide variety of condiments. This sounds mundane, but those were 16-hour days of sweat and nail-biting.

Robert's Packaging alleviates much of this anxiety with its Contract Packaging Div., which runs products in its own factory on its own machines for potential machine purchasers. This enables the end-user to evaluate the performance and suitability of the machine with the same products it will ultimately be running in its own factory, as well as train its operators and maintenance people under the guidance of Robert's experts. During PD's visit to the Roberts plant, it was running pet food in gusseted, stand-up pouches on a Model C-1500 horizontal form/fill/seal machine at a speed of more than 100 pouches/min.

Servo drives improve efficiency
Major factors in achieving these speeds and efficiencies are the machine controller, servo drives and associated hardware that power the machine. Supplied by Yaskawa Electric America, Inc., this servo system increased the speed of the machine by as much as 30 percent by eliminating most of the chain and sprocket drives, thus reducing inertia and improving control of the acceleration/deceleration profiles of the machine.

The MP920 machine controller incorporates the Yaskawa Mechatrolink open-architecture digital network, which provides high-speed, distributed control and a reduction in wiring. This reduces integration time and hardware costs by minimizing the wiring and hardware, and instead allows connection between the drives and I/O via a single interface cable. All servos and variable-frequency drives are controlled by the MP920 controller over this same, high-speed digital network.

"Benefits of eliminating hardware with a digital system include cost savings, shortened setup times, reduction in errors often incurred with hardware setup and improved performance as a result of improved communications between controls and drives," says Scott Risnes, senior engineer at Robert's Packaging. "In addition, servo drives are very flexible. Changeovers for different products and/or bag dimensions are much simpler and shorter, and can be implemented through the human/machine interface, rather than requiring mechanical changes."

"Another feature of this controller and network topology is that diagnostics and real-time monitoring are inherent to the MP controller family," says John Downie, packaging industry manager at Yaskawa Electric America. "Since most of the machine functionality is managed by this controller, the operators have monitoring access to almost every function of the machine."

The Robert's C-1500 horizontal f/f/s machine can produce stand-up, gusseted and flat pouches up to 12 in. wide by 15 in. high with up to a 5-in. gusset. Pouches can be produced with or without zippers. During PD's visit, the plant was running zippered pouches approximately 6.5 in. wide by 8 in. high with a 1.25-in. gusset, containing approximately 6.5 oz of a pet food.

Robert's machines are generally used for products with relatively rigorous packaging requirements. The product being run during PD's visit to Robert's is proprietary, so the exact structure is not disclosed, but in September, 2001, PD ran a story about Poore Brothers running potato chips on a similar Robert's hf/f/s machine. The film for those products is a five-layer laminate from Printpack that comprises (outside to inside) 48-ga polyester/ink/low-density polyethylene/50-ga metallized polypropylene/ LDPE/1.5-mil PE sealant. The PET film is used because of its stiffness and resistance to stretching. This is very critical with the Robert's and other hf/f/s pouch machines. The metallized PP provides both an oxygen and a moisture barrier. The 1.5-mil PE sheet on the inside provides thorough sealing characteristics, and puncture-resistance and sealability for the applied zipper. The PET and metallized PP films have excellent moisture- and oxygen-barrier features that provide a shelf-life up to 180 days for the warehouse snack food market.

Combination of intermittent and continuous motion
A unique feature of the Roberts machine is its combination of intermittent-motion pouch forming with continuous-motion filling. To start this operation, film is pulled from a roll mounted on the front of the machine by powered draw and unwind rollers. The film passes over a series of dancer rolls between the two powered rollers, and date and product code are applied to what will be the bottom of the gusset by a Markem SmartDate 2i thermal transfer coder.

Next, two holes are punched through the film in the gusset area to assist in sealing the gusset tails together. The film then passes over a plow, after which the machine folds the front and back portions of the film to create the gusset or "W" fold. A Fresh-Lock zipper closure from Presto Products feeds down between the two layers of film, and the top and bottom flanges of the zipper are heat-sealed to the product contact layer of the film. The zipper is then plowed open, and the side and bottom heat seals are made. The holes punched through the film in the gusset area are then sealed to give the gusset strength. The last pouch-making station is the zipper-crush area, where a series of multiple heat-seal dies flatten the zipper at the side seals.

A photoeye at this point registers the film and tells the draw rollers how far to pull the film for each pouch. Next, a vertical knife cuts the continuous web of film into individual pouches.

A continuous-motion transfer assembly then delivers the pouches to double-armed pouch clamps that grip the pouches on both sides to prevent sagging. The pouch clamps pivot inward, suction cups open the pouches, and air jets completely expand the pouches/gussets to prepare for filling. With the bottom opened, the bag moves to the filling station, where 10 funnels travel continuously above the pouches in an oval racetrack on the machine.

Product is weighed by an Ishida NZ three-tiered, 16-head scale from Heat and Control mounted above the pouch machine. Product is delivered into the buckets from a central hopper. The amount of product delivered to each weigh bucket is about one-third of the weight of the finished package. For each weighing, the control system selects the combination of three or four buckets that comes closest to the total bag weight without being under that weight, and empties those buckets into an oscillating timing hopper. The hopper directs the product into the funnel, which dips into the pouch and travels with the pouch for four seconds along a 107-in. stretch as the funnel discharges. This prolonged filling feature is the key to the machine's high speed, because it eliminates the long dwell time typically required for filling. The pouches are agitated during filling to help settle the product.

At the end of filling, the funnel is lifted out of the pouch, and the pouch is dusted to remove product from the top-seal area. The filled pouches travel over a settling conveyor, after which the pouch clamps pivot outward to pull the top of the pouch tight to provide a wrinkle-free surface.

Reciprocating seal bars clamp and seal the tops, after which a cooling bar chills the seals to give the package top a firm, straight shape. Finally, the clamps release to drop the pouches onto the discharge conveyor.

The oscillating timing hoppers communicate between the Ishida netweigher and the Robert's hf/f/s machine. This added communication provides a safeguard for correct filling weights, and it strives to optimize uptime for continuous-motion filling.

The C-1500 incorporates eight Yaskawa servo drives, which are used for the main line shaft; the film-draw roller; the film-tension roller; the chain with the pouch clamps; the vacuum-cup drive; the v-belt discharge conveyor; and the discharge kicker.

"We are very pleased with the Yaskawa servo drives. They are extremely rugged," says Risnes. "Rather than use gearboxes, we connect belts, chains and couplers directly to the shaft out of the servo drive. It has to be very strong so it doesn't deflect. In addition, the Yaskawa units are more compact than other servo drives, so they don't take as much space on the machine, and we've found them to be less expensive."

The machine also incorporates five Yaskawa variable-frequency drives, which are used for the film unwind, zipper unwind, settling conveyor, settling agitator and takeaway conveyor.

Pouches leaving the hf/f/s machine pass through a Cintex metal detector and an Ishida DACS checkweigher, and are hand-packed into shippers. The shippers are closed by a Belcor taper, and a Marsh Patriot ink-jet printer applies the product name, code and other information to the case.

More information is available:

Form/fill/seal machine, contract packaging services: Robert's Packaging, 269/962-5525. Circle No. 223.

Servo drives, digital network, variable-frequency drives: Yaskawa Electric America, Inc., 847/887-7219. Circle No. 224.

Rollstock: Printpack, Inc., 404/691-5830. Circle No. 225.

Thermal transfer coder: Markem Corp., 866/263-4644. Circle No. 226.

Zippers: Presto Products Co, 800/558-3525. Circle No. 227.

Ishida scale, checkweigher: Heat and Control, 510/259-0500. Circle No. 228.

Metal detector: Cintex of America, 414/657-7848. Circle No. 229.

Taper: Belcor Industries, Inc., 604/270-0811. Circle No. 230.

Ink-jet printer: Marsh Co., 618/234-1122. Circle No. 231.