DUSSELDORF, GERMANY - ``Plastics High Performance Packaging,'' a conference in Dusseldorf before K'95 opened, turned into a forum for PET blow molding technology. Ten of the 18 papers presented focused on PET resin or injection stretch blow molding. The global conference, held Oct. 3-4, was sponsored by the Society of Plastics Engineers, based in Brookfield, Conn. About 100 people attended.
Machinery company papers focused on new technology to improve the efficiency of injection stretch blow molding. One popular topic: How to alleviate production bottlenecks on a single machine caused because injection molding preforms take longer than blow molding. Firms also detailed new grippers for moving preforms to the blow station.
All of the development bodes well for injection blow molding, said Dewey Rainville, a consultant in North Plainfield, N.J., who was a session moderator at the SPE conference. Some processors have switched to extrusion blow molding, he said, because machinery companies have improved the process, especially for molding thin-wall parts.
To compete, injection blow molding has to keep improving, Rainville said.
Here is a look at some conference papers detailing innovations for blow molding PET bottles:
Nissei ASB Machine Co. Ltd.'s approach, through its new PF Series of blow molding machines, is to employ two sets of injection cores, used alternately. Nissei engineers combined the best aspects of both one-stage and two-stage systems to eliminate steps that are nonproductive, such as a longer injection molding time to properly cool the preforms, said Bob Blakeborough, vice president and European technical services manager in Peterborough, England.
On the PF machine, the first set of preforms is molded in the neck-up position and lifted out of the cavities while remaining on the injection cores and held by the neck splits. A servo motor swings the cores/preforms away and the mold immediately closes again with the second set of cores. Meanwhile, the first preforms cool on the cores. Before blow molding, the preforms are reheated by infrared lamps.
Nagano, Japan-based Nissei ASB launched the first FS model at BrasilPlast'95 in May, with a one-stage machine that integrates both injection and blow molding. At K'95, the company showed three new models; two-stage machines that include an injection press, reheat machine and a blow molding machine.
Currently, the FS machines can mold only circular containers. Blakeborough said Nissei ASB engineers are working on FS machines that can make oval bottles and other shapes.
Another benefit, according to Blakeborough, is a new preform-handling system that uses a plastic gripper. Traditionally, the number of cavities had to be the same for both injection and blow molding, resulting in the under-utilization of the blow molds because injection molding preforms takes much longer than blow molding bottles. The PF machine uses blow molds with fewer cavities than the injection mold, and makes them work faster. Blow molds can be smaller, lighter and cheaper, he said.
Blakeborough said the PF also is smaller and faster than other machines, and uses less energy.
The SPE conference and K'95 marked the move into injection stretch blow molding by extrusion blow expert Krupp Kautex Maschinenbau GmbH.
Krupp Kautex did not display its new KBS 5-1500 on the K-show floor, but the company ran a shuttle bus to an open house at its plant in Bonn, Germany.
The new one-stage machine combines the advantages of a rotary machine and a shuttle-type machine, said Stefan Bock, who manages the firm's diehead and extruder design department.
The KBS 5-1500 uses twin injection clamping units, each with its own mold, mounted at right angles to one another. A single extruder feeds plastic into both clamping units, which pivot to move the injection molded preforms for transfer into the blowing position. The extruder screw never stops.
Action alternates between the two clamping units. During the period of interruption between injection, the screw shifts back to provide space in front of the screw tip for melt accumulation. The screw moves forward to its original position when it is time to refill the injection mold.
Bock said flexibility is a major advantage of the KBS 5-1500. It can be operated with one injection mold only. The machine is never totally ``down,'' because one mold can be worked on while the other mold continues to produce.
For moving the preforms from injection to blow molding, Krupp Kautex developed special grippers that grasp the inside preform surface, not the outside, where they could mar the surface, Bock said.
In PET preform injection molds, Tooling Preform Systems BV of Veenendaal, the Netherlands, showed a shuttling-mold system, now under development, which the company claims cuts cycle times nearly in half from conventional technology. TPS is billing its Multi Cavity Preform System as an alternative to stack molds.
Sections of the mold shuttle back and forth. Molded preforms are removed by two robots and placed on a conveyor on top of the injection press. The conveyor runs down the clamping end of the machine and drops the preforms into bins at the end of the machine.
TPS claims its shuttle mold can run on a 10.5-second cycle, compared with 18 seconds for a conventional mold. Floor space is cut in half, the firm said.
Although cooling time is somewhat longer because the preform stays on the core longer, TPS says that means the cooling is more intensive.
A patent is pending. TPS officials showed a video at the conference of the shuttle system using single-cavity molds.
The Dutch company also will introduce in mid-January a 32-cavity hot-runner mold for co-injection of multilayer preforms.