Dual-lane shrink bundler for six-packs of Rave hairspray allows plant to run line at 200+ bpm, and higher speeds are being considered. New handling features cut downtime.
By Arnie Orloski, Editor
On the face of it a new dual-lane shrink bundling system at Chesebrough-Pond's Clinton CT plant seems to yield a relatively modest improvement over the single-lane system it replaces. The new equipment permits C-P to run its Rave pump hairspray packaging line at 200+ bpm compared to a standard of 175 bpm before. But it's not just line speed that's at issue. The new equipment is far more productive than the earlier line resulting in more product in the warehouse. This gain in productivity has helped to reduce the overall "supply chain" thereby increasing customer satisfaction. "The cost of the new machine was justified on the basis of increased output for the line" says Steve Martinik who is responsible for equipment purchasing and maintenance at Clinton. The line speed increase can be largely attributed to the dual lanes. The key reasons for the true increases in production are several product handling systems built into the new bundler by its manufacturer Packaging Machines Intl. (Elk Grove Village IL). These include: * The machine is outfitted with three sets of dual helixes or twin timing screws to carefully feed bottles to each of the two wrapping stations. * A new movable bridge assembly helps transport the group of six bottles as it's overwrapped with shrink film. This virtually eliminates the chance for misalignment or even toppling of a bottle. * A unique downstream combiner ensures that the two lanes of bundled bottles merge back into a single spaced lane without any chance of collision or damage. * A new coated seal bar helps minimize the downtime that's usually associated with application of nonstick tape to sealing jaws. * To nearly eliminate any downtime for film changes C-P specified a unique scissors-lift table that makes loading of film not only fast but almost effortless. This permits workers to create a flying splice so the machine need not even slow down for film changes. Output is crucial The hairspray packaging line at C-P's venerable Clinton plant has been subject to upgrades regularly in the last few years. "We package a variety of Rave products on this line" says Martinik "but despite all the differences in 'flavors' and bottle decorating most all the bottles are two-inch-wide cylinders. Even the bottle heights vary only a little." The Clinton plant blow molds Rave's 7- to 9.3-oz bottles of high-density polyethylene and decorates them on line. Once they've been filled and pumps with overcaps applied they are conveyed toward the PMI wrapper. "We had been running our previous film wrapper at 175 bottles per minute" Martinik recalls. "We wanted to get the speeds up above 200 bottles per minute since the other equipment on the line can handle that speed. "The filled bottles are fairly stable but they're tall so they can tip easily if they aren't handled smoothly. And the faster you move them the more stability becomes an issue." That's the reason PMI engineered the arrangement of dual helix bottle-control parts a first for the machinery builder. They were built by Ernst Timing Screw (Bensalem PA). "We hadn't used this technology before" says Randy Spahr of PMI. "Ernst is a regular supplier to Chesebrough so they were recommended to us." Before the bottles enter the wrapper they feed through one set of dual helixes that carefully reorient the bottles into two lanes. This helps control any back pressure on the bottles Martinik says. As each lane is conveyed toward the two sides of the wrapper each lane moves through another set that converts each single lane again into two lanes. "Bottle control is a major issue with these speeds" Martinik explains. "These sets of dual helixes split the bottle flow with careful control. We rarely have problems with bottles tipping unless the conveyor gets sticky." Incidentally Martinik's official title is "manager of machine adjusting" a term that's probably as old or older than the Clinton plant. Functionally he's responsible for equipment purchasing and maintenance. Offset wrapping Probably the most critical aid to bottle stability is the bridge assembly also a first on PMI equipment. As PMI's Spahr points out C-P runs the product grouping in the opposite direction from most manufacturers two bottles leading and three deep. "Most others run bottles three wide and two deep" he says. "That way you don't have the concern about the middle row coming askew. This was the reason we developed the bridge feature to transfer the bottles without disturbing the package configuration." After a group of bottles has been collated in the staging area the group of 2x3 bottles is pushed 900 into the loading area for wrapping. When the pusher bar begins to move the group into and through a curtain of film the bottoms of the bottles move onto a transfer plate that carries the group as the film is draped over the group. A hold-down device helps to stabilize the tops of bottles. Meanwhile the seal jaws come down behind the group to seal the film wrap around the bundle. C-P uses a 1.5-mil film of low-density polyethylene that's made by Union Carbide (Danbury CT). "There is a slight timing difference between the retraction of the transfer plate and the retraction of the pusher arm" Spahr says. "Thus we hold the group of bottles momentarily while the bottom plate is retracted." When both are retracted the bundle is then conveyed into and through the shrink tunnel. This same operation is repeated on each side of the wrapper. However each lane can operate independently should one lane be down for service. Quick-change seal bars Since the bundling system was installed last fall C-P has added one set of new coated seal bars that PMI has developed to help cut this source of downtime. In the past the seal bars had been finished with a self-adhesive tape made of a high-slip tetrafluoroethylene polymer. When the tape was worn this required C-P mechanics to remove the jaws from the machine replacing them with a spare. The machine would be down 15 minutes but the maintenance department had to rebuild them a process that could take 90 minutes to two hours according to Martinik. Like C-P the machinery builder has experimented with thin coatings of high-slip polymers applied directly to metal parts. It now offers coated inserts for the seal bars for quicker replacement but it also offers operating benefits. "We're experimenting with these on one side of the machine and they really look good so far" Martinik reports. Replacing the bar insert now takes about 10 minutes. Even more helpful is that the seal temperature can be reduced by 75°F or more because the film comes into almost direct contact with the hot metal--instead of trying to transfer heat through 5 mils of tape. "In most cases our coating will outlast the tape primarily because the higher temperatures will degrade the tape faster than the lower temperatures will wear the coating" Spahr says. "This turns a high-maintenance part of the machine into a low-maintenance area." The inserts cost about one-third more than the tape but Martinik confirms that longer life reduced downtime and lower heat more than make up that difference. Merging downstream C-P worked with Alliance Industrial (Lynchburg VA) to develop the unique combiner that merges the output of both shrink tunnels into a single lane. "This combiner uses photoeyes and gates that are really rubber bladders to control the flow of bundles. When we have two packs coming to the same point the sensors detect this and one side inflates to clamp the package on that side allowing the other to continue on the conveyor. When clear the bladder deflates to release the other pack" Martinik explains. The shrink-wrapped packs are conveyed into a wraparound case packer originally manufactured by Diablo Equipment and purchased through PMI. Diablo has since merged with Arpac L.P. (Franklin Park IL). This machine positions two six-packs onto a corrugated blank then folds the corrugated back over the bundles and seals the pack with hot melt. The 12-count case is eventually shipped to customers' warehouses. The six-packs are considered distributor packs. A distributor may allow stores to order in case lots or in the six-packs. Film on the fly Just as the bottle handling features were engineered to minimize downtime C-P and PMI worked to virtually eliminate it from the function of film loading. In fact PMI offered the company several choices of devices to aid in loading fresh rolls of film. This is critical at the Clinton plant Martinik says because many of its workers there are women some of them veteran employees. The wrapper itself was designed with two roll positions for each side of the machine. "We drive the front roll carriage so we have direct control over the front roll of film" says Spahr. "Plus these machines are equipped with a cradle roll-mount system. Most other wrappers use shafts and core chucks." The ergonomic film loading system is actually a hydraulic scissors lift that's covered with a fabric skirt. It's powered by a hydraulic pump that raises it into position and it can be locked into position at the machine with pins. However the lift is mounted on wheels so it can be easily moved out of the way or used with other machines. "The lift system works real well for us" says Martinik. "When it's positioned properly the worker simply slides the film roll to the edge of the machine maneuvers it over the machine frame and rolls the film right into the film bed. Then the cradle is moved back into position and the film is ready to be spliced." Workers can create a flying splice because the film is running quite slowly. A worker simply unwinds more film than needed and tapes the leading edge of the fresh roll to the existing roll. And says Martinik the machine doesn't even have to eliminate the spliced package from its production. "Our experience has been great with this line. We don't have a lot of downtime associated with this machine. It's very efficient. Because we run at relatively low cycles per minute on each lane we're not pressing the machine either."