2009/3/18 9:45:12
If you’re a user of all-electric injection machines or only a wannabe, IPF is the event to view the latest and hottest. The most recent edition proved no exception.
At the International Plastic Fair in November in Tokyo, show visitors could view everything from a tiny 10-metric-ton micromolding press employing magnetic clamping to massive two-shot all-electric machines targeting the molding of large automotive components. Hybrid machine proponents, meanwhile, were not to be outdone, showing that the latest machines powered by servodriven pumps could offer the same benefits as all-electrics, plus better pressure control and the advantages of direct clamping to boot.
Linear motor and electromagnetism Toshiba's all-new EC-SX Series has a distinctively European look. JSW's midsize machine range gets a speed boost. A two-shot electric giant from Mitsubishi has a rotary center platen. Upgrades all around on Ube's MDS-V series. A shot of compressed air accelerates a Niihata turntable vertical. In-spec molding from shot one is promised with this super-responsive Nissei press. |
All-electrics
Market leader Sumitomo (Tokyo) packed its stand with a total of 11 all-electrics, showing off not just the machines themselves but the company’s back-to-basics concept of Zero Molding, whose key components include Flow Front Control (FFC) for complete packing at low pressure and Minimum Clamp Molding (MCM). FFC is a means of better introducing the melt into the cavity. “Normally, the screw forces the melt into the barrel, and this can lead to undue stress or flash,” notes Sumitomo. FFC allows the melt to be introduced at the lowest possible pressure.
Sumitomo also debuted a new screw design with no compression zone called the SL (Spiral Logic) screw. The SL screw is two-thirds the length of a standard screw, does not generate shear heat, and is said to reduce short shots and defects such as warping. The screw was demonstrated on the prototype 10-metric-ton ML200, which uses a linear electromagnetic clamping unit (see diagram above). In essence, a linear motor is used for mold open-close and an electromagnet for clamping. The noncontact clamping mechanism is said to be much more durable than toggle presses.
Among machines on show were the 130-metric-ton SE30DUHP-CI two-shot press with injection speed up to 800 mm/sec and the 530-metric-ton CL7000 press, which was handling a molding task normally carried out on an 850-metric-ton press through MCM and adoption of a double center press platen.
All-electric pioneer Fanuc (Yamanashi, Japan), meanwhile, was intent on proving that its injection presses are not only capable of high injection speeds, but also can accomplish this with fast response and precise control, and at high injection pressures. The 100-metric-ton S-2000i 100Bh press at IPF claimed 1000-mm/sec injection speed with ramp-up time of 33 ms. According to Katsuyuki Yamanaka, manager of the Roboshot sales division at Fanuc, injection power is 2.9 times that of the previous Fanuc all-electric rated at 500 mm/sec.
Fanuc adds that it can now control the V-P switchover point with an accuracy of 0.01 mm, which enables a decrease in peak pressure and better control of injection volume. Its new control capability also offers eight high-response patterns for pressure decompression, thereby allowing fine adjustment of the pressure profile, which in turn prevents overpacking and short shots.
Fanuc’s injection unit is actuated via a direct low-inertia coupling instead of the more traditional belt drive. At IPF, the S-2000i 100Bh was molding light guide panels for a portable music player in a two-cavity tool. Maximum flow length was 83.7 mm for the polycarbonate parts with an average thickness of just 0.35 mm.
Toyo Machinery & Metal (Akashi City, Japan) highlighted a number of developments that reduce the carbon footprint of its machines, among them a two-step reduction system for plasticating and optimized toggle mechanism that enables use of a smaller servomotor. It also showcased its high-speed (700 mm/sec) Si-50IV machine molding 3-inch, 0.3-mm-thick light guide panels from polycarbonate using an injection press function with response of 50 ms and injection speed of 700 mm/sec.
Traditionally strong in the small machine segment, Toyo’s largest offering is now the Si-850W, seen molding 30-liter trash bins at IPF. The 850-metric-ton press is equipped with a 100-mm screw, and claims maximum injection speed of 150 mm/sec and maximum injection pressure of 186.2 MPa.
Toyo also unveiled a two-color 230-metric-ton horizontal press, the Si-230IIIRW, molding acrylic Fresnel lenses on the show floor, and the ET-80HR4 vertically clamped machine with horizontal injection, seen molding four different types of cutlery from polylactic acid (PLA) biodegradable resin in a family mold.
Toshiba Machine (Tokyo) debuted its new EC-SX series of all-electric machines at IPF in clamping forces of 50-350 metric tons. Key new attributes, according to Kent Sato, general manager of the injection molding machine department at Toshiba, are the Linkline toggle system coupled with two-piece platens that combine to increase clamping unit rigidity by 30%; dynamic velocity clamp control that reduces dry cycle by up to 20% without subjecting mechanical components to shock; the S-Cube (Simple, Steady & Smooth) injection unit with linear guide rails and a digital load cell that improves pressure control; and an option to achieve injection speed of 1300 mm/sec in 16 ms.
The EC-SX Series machines also feature what Toshiba calls Dynamic Self Tuning (DST) – essentially tools to optimize the filling (DST-Fill) and clamping (DST-Press). The tools allow adjustment and control of process parameters in order to account for viscosity variations in the resin being molded.
JSW (Tokyo) announced a major upgrade of its 550-metric-ton and upwards J ADII all-electric machine series, bringing improved productivity through faster mold open-close and use of a new screw design for faster plasticating and recovery. “The toggle clamp can open at a speed of 65 m/min,” says Yoshiaki Miyamoto, JSW’s manager of overseas sales. Miyamoto adds that the second-generation all-electric J650ADII-3100H machine on show at IPF is 27% faster than its equivalent hydraulic injection press and saves 45% on energy costs. Additional advances include “drastically improved” ballscrew life through utilization of newly developed JS1 grease and retaining pieces.
JSW is now in the fifth iteration of its small and midsize all-electric presses, and gen-five improvements include 6.04G acceleration to 800 mm/sec (in 8.4 ms) for molding 0.33-mm-thick cell phone light guide panels on the J110ADII60H-SA. Previously, ramp-up time was a more leisurely 22.5 ms.
JSW’s JT40AD20VS-US vertical machine also boasted an 800-mm/sec injection speed achieved in 21 ms. Previously, maximum speed attainable was 500 mm/sec. The press at IPF demonstrated molding of LED bases from PA9T (a semiaromatic nylon with high heat resistance) with wall thickness down to 0.07 mm.
Mitsubishi Heavy Industries Plastic Technology (Nagoya, Japan) was promoting large all-electric machine developments at IPF. “We now use direct-drive servomotors on all our all-electric machines, including two-platen machines,” says Hiroto Matsushita, manager of new machine development. Previously, direct drive was only used on toggle machines up to 850 metric tons. Technically speaking, Mitsubishi’s two-platen machines are hybrid because hydraulics are used for final clamping.
Also new at IPF was the emR series of two-platen coinjection machines with rotary center platen. Presses sized at 1450 and 3000 metric tons are available and as with other large Mitsubishi machines, they regenerate electricity via the servomotors through harvesting mechanical braking energy.
Other developments at Mitsubishi included active mold temperature control using steam, and wireless machine monitoring via LAN. Mitsubishi also exhibited a 1050-metric-ton press outfitted with a second side-entry injection unit.
Also in big machines, the MDS-V series of large all-electric presses (650 metric tons and upwards) from Ube Machinery Corp. (Ube, Japan) features a series of improvements including sealed ballscrews that reduce grease volume by 90% and also feature improved durability. Platen rigidity, meanwhile, has been further increased, new insulated covers reduce noise levels, and an electric belt drive is used in operator safety doors, thereby eliminating the need for pneumatics. Finally, a new high-response servo system uses fiber optics for servo amplifier-to-amplifier connection, which also reduces heat and prolongs system life.
In the vertical arena, Niigata Machine Techno Co. (Niigata, Japan) showed what can be achieved with a cushion of air in its MDVR-Z Series presses – namely, rotation of a table carrying two 280-kg mold halves in a single second, compared with 3 seconds previously. “Standard compressed air is employed to raise the table by a fraction of a millimeter during rotation while a belt drive is used for table rotation,” says Denny Yanagibayashi, deputy GM of international operations.
Precision hybrids and hydraulic heavyweights
All-electrics didn’t have the floor to themselves at IPF, however. A look at Nissei Plastic Industrial (Nagano, Japan) was enough to gauge that there is significant interest in the market for servodriven hydraulic-pump hybrids. Docking a servomotor with a hydraulic machine’s pump enables precise and flexible control of oil flow; in fact, oil flow shuts off when not required. This realizes energy savings and enables the processor to take advantage of the benefits of direct clamping and better control over injection pressure.
Nissei had on show the tiny 7-metric-ton NPX7-1F press that uses its X Pump servodriven pump to save 40% on energy consumption vs. an equivalent hydraulic machine, as well as the PNX40-5A X pump-driven machine with a low-compression screw especially for molding the company’s Voltiga carbon nanotube compounds, and the FNX80-9ALM machine for LSR molding, also featuring the X Pump.
Nissei also debuted the X Pump-drive, compact NEX15-1FN press, whose claim to fame is the ability to achieve parts within spec from the first shot. Key is use of a high-response linear direct hydraulic servo valve (LDV) from Yuken that hits 400-mm/sec injection speeds in just 4 ms.
If you’re wondering, Nissei did have two all-electric machines on show at IPF, the 50-metric-ton NEX50-5E molding connectors with cavity pressure sensing, and the NEX110-18EPI electric pulp injection machine. The latter uses a special screw to mold a mixture of pulp, starch, and water into biodegradable lids using a four-cavity mold with a 30-second cycle time for the 10g shot.
Like Nissei, Sodick Plustech (Kaga, Japan) now also uses servodriven hydraulic pumps on its hybrid machines for both clamping and injection, as well as LDVs as an option for high-precision applications. Sodick was highlighting the exacting precision of both the injection and clamping units that is achievable by using LDVs, in which the motion of a spool directly driven by a linear motor is used to regulate oil flow. Its LD10m8 machine for lens molding, for example, uses the LDV’s 2-ms response time to successfully mold lenses for 8-megapixel compact camera modules with spherical surface tolerance of an infinitesimal 1.8 µm. By comparison, a linear servovalve composed of a pilot spool and hydraulic pilot valve has response time of 15-20 ms, and a conventional servovalve’s response time is 25-30 ms.
Sodick has also made progress with the clamping mechanism on its LD Series machines. Platens are supported at the center, Invar bimetal is used in the symmetrical clamping unit, and a new self-lock direct clamping mechanism is employed.
Sodick’s LIM machines have also undergone a makeover. The company offers two options to processors depending on the viscosity of the silicone being molded. A servomotor-actuated injection unit is used for viscosity up to 100 Pa-sec, while a linear direct hydraulic unit is employed for higher viscosities. —stephen.moore@cancomimould.com
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