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Article | July 31, 1996
Modular molds add flexibility to bottle molding
Unique system makes it easier for packagers to have custom bottles injection/ blow molded even when the number of bottles needed is relatively low.
Removable mold sets The key to MMT's flexibility is that individual blow molds and injection molds can be quickly removed from the frame they operate in and replaced with new ones. To understand how this is done it helps to examine the system's components. Like conventional injection/blow molding systems production begins with resin being melted and sent through the barrel of an extruder. The resin is injected into preform molds fitted with core rods. Again this is pretty standard stuff-or is it? "Because we are producing different-sized bottles with one shot which is very unusual the design of the hot-runner manifold is extremely critical and considered proprietary" says technical director Anthony Fry. Individual preform core rods are carried on left and right "frames." Typically there are 12 rods per frame. The frames shuttle in front of and then away from the extruder as the machine cycles. When the right frame of core rods is positioned in front of the extruder the preform cavities also mounted on a single frame stroke forward and close so that each core is inside a matching cavity. Resin is shot into each cavity around each core rod and after a cooling cycle the cavities open and the frame retreats. The frame of core rods with an injection-molded preform on each rod now shuttles toward the blow cavities on the right side of the machine. These cavities close for the blow cycle. As this happens the left frame of preform core rods has positioned itself in front of the extruder. So as one frame of preforms is being blown into finished containers the other frame is injection molding a set of preforms. As blown bottles emerge from the blow cavities pick-off pins move in from the right remove the bottles and stroke back. Ultimately the bottles are discharged via chutes into cases. IP has eight MMT systems in production in its Paterson plant. The precise configurations of each can vary but typically they're set up with 12 injection mold cavities and 24 blow mold cavities running at one time. This set up can produce as many as 24 different bottles simultaneously. Sizes range from as small as 30 mL to as large as 625 mL. Resins used thus far are PS and high-density polyethylene though Weinstock says some interesting work with PET is underway as well. Quick-change molds What's involved in plugging in a new mold? "We stop the extruder purge it install the new mold and resume" says Fry. "In the simplest situation where only one cavity or core needs changing we can be back in production within 30 minutes." What IP doesn't describe is how the size of the resin shot is changed when a larger heavier bottle goes into production in the place of a smaller one. As Fry says it's considered proprietary information. Each bottle produced by IP requires a unique blow mold. But the injection molds used to make the preforms don't always have to be changed. "Where bottles are not too dissimilar in shape we sometimes use the same injection mold and core rod for two or three different bottle shapes" says Fry. The customer base IP has built upon thus far consists primarily of health care and nutrition supplement manufacturers. From a single mold set-one preform cavity one core rod two halves of the blow mold one base plug and a pair of neck splits-such customers can count on IP for a million bottles annually or about 20 per week. Should their needs increase they can add cavities as required inexpensively. The packagers most likely to benefit from such technology have a predictable profile. They have a new product to test or an existing product that's not intended to be a big-volume item. They can't settle for a stock bottle because only a custom bottle can differentiate their product sufficiently. They want the quality of an injection blown bottle where control over neck finish and material distribution in the sidewall is typically greater than in an extrusion blown container. And their volume requirements can't justify the cost of conventional injection/blow molding because it requires a sizeable investment in multiple cavities. Add tools as you grow Nature's Bounty's purchasing agent Michael Oliveri especially likes the way tooling can be added if volume requirements for a certain container should grow. Then when it's time to run the container IP plugs two sets of molds into the frame rather than one. The need for second mold sets on Body Fortress has not arisen says Oliveri but it has for other products marketed by Nature's Bounty. Though plugging modular molds into a frame sounds simple enough it's a complicated challenge requiring a great deal of planning if it's to be done profitably. So many questions must first be answered including things like how long is the run and when does the run fit in and on which of eight machines? Also does the core rod or preform cavity require changing? This complexity is daunting making scheduling a real logistical challenge. But as Weinstock puts it "Scheduling proficiency is a hallmark of IP Jaycare."
A unique and generally unpublicized method of container making has emerged that makes it possible to injection/blow mold as many as 24 different bottles simultaneously in a single cycle. IP Jaycare (Paterson NJ) calls its patented concept Modular Mold Technology. (The firm is not affiliated with International Paper.) Aimed specifically at customers needing a custom bottle in small quantities MMT says marketing manager Susan Weinstock "delivers multi-cavity piece price even though a customer may only use a single cavity." Among IP customers is Nature's Bounty a prominent full-line vitamin company in Bohemia NY. The firm does a significant amount of business with IP a good example of which is its line of Body Fortress® supplements for body builders. "We decided to enter this supplement category a few years back and we felt that since we were the Johnny-come-lately in the category we needed something special to differentiate ourselves onthe shelf" says Jim Flaherty advertising vice president at Nature's Bounty. "Custom packaging was one of the ways." IP developed for Nature's Bounty a line of polystyrene bottles-100 150 300 cc- designed in the shape of something all body builders know and love: a barbell. "This category is saturated and the competition is tough" says Flaherty. " The package really helped us stand out from the crowd and I believe it's made a significant difference." Paper pressure-sensitive labels on the Body Fortress line are printed flexo in four colors plus UV varnish. They're supplied by Paris Art (Ronkonkoma NY). The package uses the IP Jaycare HingeGard® closure. The low-density polyethylene closure is a one-piece TE hinged item that snaps in place. Proper opening is accomplished by removing the tear band around the circumference of the cap and then pushing up on the thumb tab. "This closure works nicely with the barbell design" says Flaherty. "We made the ridges on the top match the ridges on the bottom so it looks all the more like a barbell."
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