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'Speed' and 'precision' were key words at Tokyo plastics fair.

Injection molding news predominated, with lots of new presses, controls, robots, QMC systems, and novel tooling approaches. There were also noteworthy developments in blow molding and extrusion.

Faster and more accurate molding were themes of the many injection molding exhibits at January's IPF '94 International Plastics Fair in Tokyo. New clamp designs, a host of more "intelligent" controllers, and tooling innovations to relieve stresses promise more flexibility in molding complex parts. A wide assortment of new servo robots also were displayed. Injection molding entries were joined by some interesting new developments in extrusion, blow molding, and auxilliary equipment. (For the robots and auxiliaries see New Products section.) In many cases, the Tokyo show offered a glimpse of what to look for at Chicago's NPE '94 exhibit this June.

PRECISE CLAMPING & INJECTION

Last month, we resorted on a new "Ultra" option from Sumitomo that controls hydraulic clamp force during injection in order to achieve stress-free molding of tight-tolerance parts. Sumitomo also modified the clamp cylinder on its fast-cycling SG 50 toggle press for smoother stopping. It was demonstrated molding nylon 66 eight-pin electrical connectors in a four-cavity mold with a cycle time of 3.5 sec.

Also reported last month, Toshiba's new IS-G series of injection presses, introduced by Toshiba Machine Co., offers energy-saving clamps that are 15-20% shorter than standard designs.

Another space-saving new clamp design eliminates the back platen and puts the clamp cylinders on the ends of the tierods alongside the injection unit on Toyo's new M8 series. 605-ton press. In addition, eight modes of injection are said to make this press capable of low-pressure molding of hard-to-fill parts without warpage.

A related system of four injection hydraulic cylinders, which can be used in five different combinations or stages, appears on Niigata's NN-MI series. This system is said to achieve low-pressure, high-speed molding without pressure peaks that may build in stresses. The NN-MI toggle-clamp series of 33-475 tons will be introduced to the U.S. at NPE '94 in June.

Multiple-cylinder combinations or stages of high/low injection pressure and speed were also shown on a new M-25B (27.5-ton) hydraulic press from Meiki. It's said to achieve high accuracy in four stages of injection pressure and speed, suitable for thin-wall and hard-to-fill parts.

Injection-compression molding was demonstrated by Meiki on a 70-ton press equipped with a new six-stage clamp-pressure control system. Pressure steps can be controlled by time, screw position, injection hydraulic pressure, cavity pressure, or the mold-opening gap.

SMALL-PRESS DEVELOPMENTS

A new SE series electric servo-driven press, which will be introduced in the U.S. at NPE '94 this June in Chicago, was demonstrated by Sumitomo. All machine movements are electrically driven except for small hydraulic cylinders built into the tiebars to develop clamp pressure. The machines will be available in 27, 83, 165, and 198 tons. (A new 83-ton, all-electric MD series press from Niigata is not yet offered in the U.S.)

Sumitomo also demonstrated new 18-ton addition to the Minimat hydraulic press line, which has closed-loop controls. The 18-ton Minimat will be available in the U.S. for under $40,000 in the latter half of this year.

A new dual-station, high-speed CV-20T-APC 22-ton vertical press from Multiplas Engineering Co. was demonstrated molding PVC electrical connectors in an 8-sec cycle time.

A new 55-ton NVR50 coil encapsulation from Niigata is capable of low-pressure molding (under 1450 psi).

Meiki demonstrated a 25-ton in-line CD injection molding machine with a 4.3-sec cycle time in a "class 100" cleanroom environment, emphasizing its ability to supply these systems on a turnkey basis. Another theme for Meiki was gas injection: It was molding a 203-g polycarbonate part in 90 sec on a 110-ton press. In this application, gas injection was said to save about 40% in clamp pressure, 20% in material, and 30% in cycle time. A new "Thermset" barrel, demonstrated on a Meiki 110-ton M-100-B-TS press, is said to provide more stable barrel heating for molding thermosets. Temperatures of three front barrel zones and one rear zone can be independently controlled.

SMARTER CONTROLS

New generations of injection machine controllers, on hand from several suppliers, showed increased monitoring capabilities in addition to various self-learning and "expert" functions.

New features on the Injectvisor V10 and S10 16-bit controllers were demonstrated on Toshiba's new IS-G series presses. The V10 "recommends" to the operator a barrel temperature, injection stroke, and cooling time based on six input parameters. In addition, both controllers now have a temperature feed-forward function that is said to increase molding stability and prevent resin degradation by controlling barrel temperature. Both controller versions also include closed-loop control of injection speed and pressure (also available on screw position and clamp position).

Sodick, a relatively new supplier in the U.S. (PT, Jan. '93, p. 91), introduced a new "NF" (neural and fuzzy-logic) marine controller that incorporates a learning process into its operation. Initial molding conditions are based on job information entered by the operator. The "intelligent" controller also infers the cause of bad parts and will automatically correct parameter values. The NF controls temperature and velocity by monitoring current values and predicting ahead, rather than performing simple "on/off" control.

Learning capabilities are also claimed for the new Data-hem-II controller from Shinwa Seiki, which is said to optimize molding conditions by detecting varying conditions from shot to shot and making required changes in subsequent cycles.

The new Syscom 1000 controller from Japan Steel Works includes color graphic screen displays and simplified operation. The controller accepts an optional "Camot II" data card, which upgrades the unit to an expert system with its own resin database. The expert system is said to improve mold setup conditions and infer necessary measures to be taken in case of defective parts. Syscom 1000 is available on J-E II series presses and is compatible with older equipment as well.

A new 16-bit controller from Toyo includes closed-loop control of injection pressure and speed and memory-card storage of up to 128 mold setups. As many as 87 parameters can be monitored. An "electronic weight gauge" option for weighing parts can be incorporated into the PLCS-9 controller through an interface. The controller was demonstrated on a new 55-ton Ti50H press, part of a "high-precision" series of hydraulic presses extending to 180 tons.

Ube Industries showed its new HUMMA-S controller (to be featured at NPE '94) for its mid-sized PZ-II machines. For simplified operation, its control panel and data panel are integrated. It has internal memory storage for 20 mold setups.

The latest generation of Mitsubishi's Mach VI controller is available in LCD and color-CRT versions featuring "one touch" setup of up to six molding conditions.

A new 16-bit "B2" controller is available from Kawaguchi with quick set-up keys and SPC capability.

Optional servovalve closed-loop control of injection speed and pressure, shot size, screw backpressure, and holding pressure is being offered by Jon Wai.

TOOLING INNOVATIONS

Two novel systems for in-mold degating and/or prevention of sink marks were shown by Sumitomo and Niigata. Both use specially placed ejector pins, which move forward after mold filling to pinch off the gate area, separating the part and runner while reportedly leaving a clean surface with no vestige mark. Alternatively, the movable pins can be used to compress a non-visible portion of the part after filling to counteract shrinkage and prevent sinks. This system reportedly can also prevent short shots and weld lines. Sumitomo calls its system "Press Alpha." It uses a mechanism in the moving platen to vibrate certain ejector pins at low frequency (10 Hz). Niigata's Ejector Compression System (ECS) operates the pins hydraulically.

In addition to degating systems, an "out-cooling injection" application was demonstrated by JSW on its DSI "Die-Slide" mold (PT, Jan. '91, p. 61). The mold has two cavities, one of which is alternately injected while the other cools. The process maximizes cooling time without significantly extending the cycle: it is said to benefit parts such as polycarbonate lenses, which require additional cooling.

90-SECOND MOLD CHANGES

A new, fully automatic quick-mold-change (QMC) system from Aioi Seiki changes molds on a 60-ton press in 90 sec. An hydraulic damp grabs the top and bottom of the mold and moves it onto or off of a mold-change table beside the press. During changeover, the first mold is unclamped and moved onto the table. The mold table then moves the second mold into position, which is loaded and clamped into the press.

BLOW MOLDING NEWS

Although it is still a prototype, the Blow Molding Center of Tahara Machinery Ltd., is notable for several reasons. One is an automatic tool-changing system that stops machine production after a scheduled number of shots, discharges remaining resin, changes all the tooling, and restarts the next production job with preset molding conditions--all without the help of a skilled operator. Pallets on a table beside the machine are used to automatically change, align, and center the mold and product holder, die tooling, blow pin, and deflashing tools.

The machine also helps an unskilled operator to establish and maintain molding conditions by means of parison length and wall-thickness control, automatic blow-pin centering, and automatic blow-pin height control in multi-cavity molds. Other features of this extrusion blow molding machine include all-servo-electric operation, easy loading and retrieval of molding conditions, self-diagnostics, reduced power consumption, and low noise level. Tahara expects to bring the machine to market in about a year.

All-electric servo-drive has been applied to blow molding by JSW. The company offers small, single-station JEB-3 and JEB-7 continuous-extrusion machines for PE and PVC (one or two cavities), with max. outputs of 44 and 77 lb/hr, respectively. In addition, JSW has a one-stage all-electric machine for PET bottles (no details were available). Cleanliness, high speed (1.7-sec dry cycle on the JEB models), low noise, and energy savings are claimed as advantages of all-electric machines.

A new BCI-T single-station extrusion blow molding machine for up to 1.5-liter PE bottles from Queen's Machinery Co. of Taiwan is equipped with an in-mold labeling system.

A number of improvements to one-stage injection-stretch-blow molding machines were shown by Nissei ASB. An upgraded model ASB-650N-II molds half-liter PET bottles in a 12-cavity mold with an 8.7-sec cycle time. Redesigned hydraulic and electrical circuits, increased pump capacity, and new hot runners with simplified wiring are said to contribute to faster cycles. A simplified water manifold and quick-connect hoses cut mold-change time by 30% vs. older models.

A 70-ton ASB-70DPH has extended tiebars to accommodate a maximum product height of 320 mm, vs. 280 mm previously; other new features include electric turntable operation and elimination of hydraulic motors above the turntable to prevent product contamination from oil mist.

New tandem molds on the 70-ton ASB-70DPW for small containers permits up to 24 cavities and higher outputs. Increased opening stroke on the ASB-50HII unit allows molding of 1.5-liter bottles in two cavities; other improvements include a redesigned hydraulic circuit for faster cycles and individual air cylinders for higher precision molding.

NEW CONCEPTS IN EXTRUSION

New "Stainless Steel Belt Sheeter" from Placo is said to extrude high-quality transparent PP sheet, making it a competitive substitute for PS. The company says a minor-like film surface is achieved by passing the extrudate between a synchronized stainless-steel belt and the large diameter cooling roll, creating pressure on the sheet or film. Molten sheet is then put through a water tank to quench it, providing a high level of transparency. After passing through the water tank, the sheet is reheated to recover rigidity. Line speeds are also said to be greatly improved over conventional sheet extrusion. The process is said to be applicable to other resins besides PP.

A new "IDC" internal die-lip cooling system for blown film from Tomi Machinery Mfg. Co. is said to result in better line speeds and production rates, as well as improved surface quality. Cooling takes place inside the die lip, and temperature is controlled by an oil-circulation unit.
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Title Annotation:International Plastics Fair
Author:De Gaspari, John
Publication:Plastics Technology
Date:Apr 1, 1994
Words:1989
Previous Article:Gas-injection molding: 'black art' or science?
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