Blow molding.

Blow Molding

Coextrusion capability for accumulator-head machines was the most notable new presence in the blow molding exhibits. There was also an extraordinary number of new stretch-blow developments for oriented bottles. Quick-mold-change was the third recurring theme.

MULTILAYER MAKES A SPLASH

K'89 turned up no less than five three-layer accumulator-head machines for coextruding large HDPE containers, as we reported last month (p. 14). Johnson Controls, Krupp Kautex (now known in the U.S. as Krupp Plastics & Rubber Machinery, Inc.), APV Chemical Machinery, Bekum, and Battenfeld Fischer all showed--or talked about--machines of this type. Though the technology has been around for a while, limited uses and costs that run as high as $1 million per machine have prevented it from catching on. However, suppliers now say that multilayer accumulator-head blow molding is slowly coming into vogue, as processors are forced to begin using regrind for the manufacture of new items.

If this does become the case, suppliers say they want to be ready for the demand. All the multilayer machines at "K" were touted as being able to mold products using two thin outer layers of virgin material (perhaps with colorant only in the outer layer), sandwiched around a thicker layer of less costly (and less attractive) regrind. In two cases, as much as 70% recycled material can be buried in the center layer.

The newest three-layer accumulator-head coextrusion machine, the M-50 from the Uniloy/Moretti Div. of Johnson Controls, uses as much as 60% regrind in the manufacture of 60-liter drums. The M-50, a prototype of which was displayed at the show, can reportedly mold 50-55 HDPE containers/hr using three extruders--a main 90-mm extruder for the regrind and two 50-mm extruders for the virgin material. In this system, material first flows into the accumulator cylinder, where each layer is kept separate. When the cylinder is full, it pushes all three layers to the head, where they join.

A revamped version of Krupp Kautex's KB 300 multilayer accumulator-head machine, capable of blowing containers of up to 1500 liters (396 gal), made its debut. The new design, which includes a quick-change system for the extrusion die and a larger area around and below the mold, is aimed at speeding up production changeovers and facilitating placement of auxiliary equipment below the mold. Mold-clamping force has been increased to 180 tons, and there's faster clamp-force buildup to improve pinch-off weld formation, Krupp representatives said.

Krupp spokesmen said the most impressive feature of the redesign is the machine's optional nozzle-changing system, in which the extruder head is preheated and transported on a carriage suspended below the platform to the accumulator head, where it is installed using a quick-action clamping system. The new clamping system allows the installation of molds for parts up to 6.6 ft long, permitting the revamped KB 300 to blow mold fuel tanks for motor vehicles, industrial containers, and large packing and transport containers.

Krupp says it has included its coextrusion accumulator-head technology as an option on a few of its other machines. For example, the KEB 5 shown at K'89 is now available with a head that uses as much as 70% regrind between two layers of virgin material. Designed to mold containers up to 10 liters, the machine has a 121-ton clamp and 2.2-sec cycle time.

While most machine manufacturers have opted to bury as much regrind as possible in the middle layer, APV Chemical Machinery, in a joint venture with a resin manufacturer, has built a 16-lb, three-layer accumulator head that uses the smallest amount of material in its center layer. The head delivers a 10-lb shot to the innermost layer, a 2-lb shot to the middle layer and a 4-lb shot to the outermost layer, said Robert Slawska, general manager of APV's Blow Molding Div.

Bekum's version of a three-layer accumulator head, which was not shown at "K," uses one pin to push out all the material. Patented in 1985, the "Biex" head uses two extruders--one for the virgin and another for the regrind. The system can mold containers up to 60 liters, a spokesman said.

Battenfeld Fischer demonstrated its new multilayer accumulator-head technology during the show at its Troisdorf plant. Known as the ReCo (recycling coextrusion) system, it is claimed by Battenfeld officials to achieve the same output rates as monolayer technology. The new technology was shown producing 120-liter (32-gal) drums with up to 70% regrind in the inner layer. The company reportedly has sold several ReCo machines.

NEW TWISTS IN PET BOTTLES

Two years of research have resulted in the manufacture of a machine capable of extrusion blow molding unoriented bottles from standard injection-grade PET rather than the more costly PETG normally used for such bottles. The key to Automa's new single-extruder machine is a specially designed head that Automa representatives at the show declined to discuss in detail, saying only that its unique design gives the machine the capability to blow mold 7450 10-ml bottles/hr. Part of the secret appears to be the low melt temperature--less than 500 F.

In stretch-blow molding of PET and other resins, Nissei ASB showed no less than five new machines. One, the ASB-240 J, differs from Nissei's usual rotary design in that it has a linear-movement mechanism that slides the product being formed in a straight line from station to station after the preform injection stage. It's aimed at wide-mouth jars and has larger clamping area than Nissei's rotary machines, permitting production of jars with up to 160 mm neck diam. on four cavities and 83 mm with eight cavities. Four 6-liter containers of up to 200 mm diam. can be molded of PET, PP and polycarbonate. The machine, which keeps the products it's forming vertical at all times, can be used either as a four-station system (i.e., injection, conditioning, stretching, and blowing/ejection) or a three-station system for nonoriented containers. Clamp force is 220 tons.

Nissei's new ASB-32, an eight-station, twin-injector machine of its usual rotary design, is for high-volume production of PET containers. With six cavities it reportedly can mold 9600-1/4-liter bottles/hr, weighing 16 g each. Models with either a 70-ton clamp for bottles or 220-ton clamp for wide-neck jars are available.

Nissei's also introduced these rotary injection-stretch-blow machines: the ASB-16, a 16-cavity machine with two 18-oz injection units for speedy molding of 2-liter containers; the ASB-50, a compact machine for processors who frequently change the container size produced; and the ASB-70 DP-H for high-speed production of lightweight, wide-mouth PET or PP food jars. The latter is an extended-height version of the earlier ASB-70 DP, for molding larger jars. It reportedly incorporates a new approach to machine design, making it more economical than any other machine in its class. A unique mold design using a continuous injection nozzle can turn out up to 2700 bottles/hr using a six-cavity mold. R&D on molding PP jars with this machine reportedly now makes it possible to mold six cavities on a 13-sec cycle. Also, a "T" version of this machine is available for coinjection applications.

Nissei also showed for the first time its new preform molding machine, the ASB-650 NP II, which resembles its stretch-blow machine, but uses the stations after injection just for additional cooling to speed cycles. It's said to achieve 17 sec, which company sources think is the fastest available. The new machine, an upgraded version of the company's earlier ASB 650-NP, uses a 24-cavity mold to manufacture 4200 preforms/hr. A 32-cavity version is under consideration.

Nissei also demonstrated coinjection-stretch-blow molding on two machines. One of them showed how to make a pasteurizable bottle for carbonated beverages by coinjecting a layer of heat-resistant polyarylate between PET layers on the bottle neck and bottom. This is said to avoid the necessity of expensive recrystallization processes to heat-stabilize those areas. Then, heat setting is applied to the PET within one machine cycle. Such a bottle, containing 2.5 volumes of [CO.sub.2], reportedly can withstand 15 min at 150 F.

The second coinjection system demonstrated how recycled PET could be used in a beverage bottle--by burying it in the center of a three-layer structure. Up to 60% regrind can be used by this method, according to Nissei. On the same machine, Nissei demonstrated in-mold labeling of oriented PET bottles. Labels with a heat-activated adhesive are taken from a magazine by a suction-equipped robot and placed in the mold, where they are held in place by vacuum.

MORE STRETCH-BLOW MACHINES

There was other news in oriented bottle systems, as well. As noted in our September preview (p. 56), Sidel's new SBO 4R machine is designed to make shorter production runs of PET bottles for test marketing, prototyping, or short-run production (it has a quick-mold-change system). The new rotary press is said to be the smallest rotary blow molding machine ever made for PET bottles. It has four molds and can reportedly produce up to 4000 bottles/hr, ranging from 0.25 to 3 liters, though at 3 liters production drops to between 3300 and 3500 bottles/hr.

Aoki Manufacturing Co. of Japan (represented in the U.S. by Formex, Inc.), brought out an improved version of its SBIII series of rotary injection-stretch-blow machines. Among the changes made to the machines are a new method for raising and lowering the platen and a new clamping cylinder, both adding speed to the SBIII line. According to a Formex spokesman at the show, the machines can mold a 27-oz PET container in 13.8 sec, down from 22 sec when the machine was created in 1985. A 12-oz PP container that took 23 sec to mold two years ago, can now be molded in 15 sec, the spokesman said.

Bekum's new RBU-225 reheat stretch-blow molding machine is designed for making up to 1800 3-liter PET bottles/hr. This new machine design includes two heating lines in the reheat oven, allowing precise temperature control; a sorter that uses gripper clamps to carefully move preforms from the oven to the mold area, ensuring the preform is protected from being scratched; and a compact "footprint" of about 250 sq ft.

Also newly upgraded is Bekum's BMO 4 D extrusion-stretch-blower. Now called the BMO 6 D, the new machine is designed for blowing 1.5-liter PVC carbonated soft-drink containers. And BMO 6 D operates with two three-cavity molds and two conical twin-screw extruders to achieve higher production rates than the BMO 4 D--e.g., 2700 pressure bottles/hr or 3700 lightweight bottles/hr for noncarbonated beverages. It has an additional three-step conditioning and compensation station, ensuring an even temperature profile.

EXTRUSION BLOW NEWS

Quick mold change was incorporated into new Hesta machines from Stahl Blasformtechnik (represented here by FGH Systems). This reportedly cuts the time to change a double mold from almost 2 hr to less than 30 min. The key to the quick-change system is that the masks and the mold are combined into a single unit, eliminating the need to adjust the masks every time the mold is switched, a spokesman said.

Bekum added a quick-mold-change system to all of its BM machines. And a new series of twin-station, coextrusion blow machines from Battenfled Fisher also have QMC capability. Consisting of four machines that can produce containers up to 6 liters, the BFB1-D series have what's said to be an innovative clamp design with separate functions for guiding the platens and applying clamping force centrally to the mold. A special correcting feature is said to prevent minute lateral displacement of the parting surface of the mold during mold opening and closing, thus ensuring optimum protection of both the mold and part during part removal. The machines also have an integrated post-cooling station, in-machine deflashing, and aligned discharge. The series was inaugurated with the BFB 1-3 D and BFB 1-4 D, the latter of which was shown with a newly developed twin-coextrusion parison die in 2 X 2 cavity production of multilayer ketchup bottles. Battenfeld also introduced a new Blowcom 001 control system for these BFB 1 D machines.

Although not shown at K'89, another new clamping mechanism was discussed at the show by representatives of Mauser-Werke GmbH. Mauser, which makes machines for molding very large containers (up to 2000 liters), applies clamping force with short-stroke locking modules mounted on the platens rather than conventional hydraulic cylinders behind the platens. A Mauser spokesman said this ensures short cycle times and allows high clamping force with the use of very little oil. Changing clamping force is also easier, he said. Mauser's clamp units are designed for forces of 33, 66, 99 and 165 tons.

Magic MP (rep. by Big M Plastic Equipment) showed new version of its multi-head extrusion machines. The five new machines, which can blow containers from 1 to 5 liters, have been improved by the addition of lightweight-alloy platens that offer twice as much rigidity at half the weight of standard steel and permit a faster dry cycle (1.3-1.8 sec) at lower energy consumption, a company spokesman said.

NEWS IN CONTROLS

New controls for extrusion blow molding machines were exhibited by several companies, including Battenfeld Fischer and Moog GmbH. At the heart of Battenfeld Fischer's new Blowcom 002 system is a personal computer that monitors and controls temperature, wall thickness, and mold opening/closing speeds, as well as the sequential operation of the machine. Blowcom 002 can also run evaluation programs for statistical and management information systems.

Moog's new Total Machine Control (TMC) is a development for blow molding similar to its Mopac injection control systems. This is a modular micro-processor system that shows all control processes both graphically and numerically on colored screen pages. The controls have 128 timers, 128 counters, up to 32 zones of temperature control, 100-point parison programmer, and position, speed, and acceleration controls for all motions such as mold, blow pin, and ejection piston.

New water-temperature controls were shown by Jomar. The micro-processor-based controls have automatic compensation for in-process heating and cooling requirements and are totally adjustable. They feature a 15-kw heater for maximum molding range and faster setup, and a 2-hp, 50-gpm pump that provides turbulent flow of coolant for maximum efficiency, according to the company. Temperature ranges on the controllers are up to 250 or 300 F.