Injection molding.

Injection Molding 

For injection molders, NPE '91 brought about a wider range of choices--particularly in small machines. New machinery introductions in this area mean that North American molders need no longer look to Germany as the primary supplier of small presses. There was also a new assortment of machines for high-speed molding of packaging, as well as a slew of new general-purpose presses. NPE '91 saw new developments in gas injection molding, the promising technology that everyone is talking about but for which progress was slowed by patent battles. Almost overshadowing technology developments were announcements of a major acquisition, new joint venture, and changes in distribution arrangements among suppliers.

SMALL-MACHINE ARENA GROWS

HPM Corp., Mount Gilead, Ohio, one of several major equipment manufacturers to introduce lower-tonnage presses at NPE, is offering a new line of small machines for high-volume production designed primarily by the long-time British reseller of HPM presses, Dassett Process Engineering Co. HPM's Series C line of 35-, 55-, and 95-ton hydraulic machines have generous platen size, stroke, and daylight, said to allow for use of larger molds. Series C machines feature pressure-matched proportional hydraulics; low power consumption; fast-response, twin-cylinder injection; microcomputer control through the HPM Command 200 system; and reportedly high repeatability. Valves, pumps, controllers and cylinders are "totally Vickers" for performance reliability and ease of maintenance, according to the company. Pricing of HPM's C line is said to be competitive; a 55-ton press costs about $54,000.

A "completely redesigned" 75-ton press was unveiled by Jaco Manufacturing Co., Berea, Ohio. The Jaco III-H-75 offers a number of standard features such as low-pressure mold closing, programmable control, variable pressure compensated pump, sprue break, and hydraulic ejection. Options include mold unscrewing, bimetallic heating cylinder, and a thermoset conversion kit.

Nissei America, Inc., Anaheim Hills, Calif., introduced the PSX40-5A, a 44-ton press said to be suitable for high-speed precision molding (PT, May '91, p. 63).

Smaller machines will also be available soon from Sandretto Plastics Machinery, Farmington Hills, Mich., which announced at the show that its parent firm in Italy has made an agreement with a Milanese builder of small presses. Within six to eight months, Sandretto plans to offer presses in the 18- to 60-ton range. The company's current line begins at 66 tons.

Finally, Cincinnati Milacron's U.S. Plastics Machinery Div., Batavia, Ohio, introduced a line of small Vista Sentry presses at this year's show (see PT, July '91, p. 69).

HIGH-SPEED MARKET HEATS UP

Engel Canada, Inc., Guelph, Ont., introduced the HS line of specially designed high-speed/high-precision presses for packaging applications. The line has accumulator-based hydraulics and modified electronics to permit dry cycle times for a 300-ton model on the order of 1.5 sec. Other features include an energy-efficient mixing screw; closed-loop, in-cycle control; and energy-saving variable displacement pumps. The HS line is available in all standard tonnage sizes offered by Engel.

Cincinnati Milacron showed its new VH600 Vista injection machine for high-speed, high-volume, thin-wall part production. Features include an energy-efficient, variable-volume pump with proportional hydraulics; twin-cylinder injection unit; low-profile design; easy-to-use alignment; and twin-guide-rod injection unit carriage to maintain nozzle alignment.

Mannesman Demag's Plastic Machinery Div., Torrington, Conn., introduced the S Series of high-speed presses at NPE. On display was the 500-ton D 500 NCIII-S model molding PP industrial containers. The S Series' 11 presses range from 60 to 800 tons with injection shot weight up to 128 oz. The line is said to be suitable for closures, housewares, medical parts, and thin-wall parts.

Ferromatik's FM 250 molding machine for packaging was introduced by KFD Sales and Service, Erlanger, Ky. According to a spokesman, an energy-efficient asynchromotor screw drive replaces the typical hydraulic drive on the FM 250 E for a 48% increase in screw speed. This servo motor is electronically controlled to provide constant screw rpm over the entire recovery time. Performance options include 1000 mm/sec injection speed and a 25:1 L/D mixing screw.

Sandretto announced that within six to eight months it plans to begin offering North American sales of high-speed packaging-type presses built by its sister company Metalmeccanica Plast, a competitor it acquired in 1988.

GENERAL-PURPOSE PRESSES

Among the news at NPE was the announcement that Germany's Arburg Machinenfabrik will begin selling and servicing directly to the North American market (see Industry News-focus). Still, Polymer Machinery Corp., Berlin, Conn., displayed Arburg's Allrounder V line of presses here for the first time. The line includes presses of 132, 176 and 220 tons, extending the Arburg line upward from a previous max. of under 100 tons. The line is said to be "totally new" in terms of hydraulic and electric componentry, making it more applicable for high-volume tight-tolerance parts.

Allrounder V presser offer unusual mold design flexibility, according to the company. A proprietary feature, the Vario-Principle, is said to allow the ideal injection point to be determined within an 8.7-in. range in the horizontal plane of the tool platen.

HPM introduced two lines of machinery for general-purpose molding: H-Series hydraulic presses, ranging from 90 to 500 tons and T-Series toggle presses, ranging from 75 to 500 tons. Both lines have HPM's "clean design," which features integral piping.

HPM says H Series machines provide outstanding repeatability, superior cycling efficiency, rapid response, rugged durability, and maximum energy efficiency. Engineering features include "easy-roll" gates and guards, simplified manifold system, hydraulic system utilizing a fully independent ejector core system, and a combination fixed/variable-volume pumping system. A load-sensing feature assures pumps operate only at the pressure required to achieve the injection velocity setting.

Though T-Series machines are highly suited for general-purpose molding, HPM stresses they're adaptable to custom production of specialty parts. Machines in the T-Series feature a new hydraulic system, improved energy efficiency, and a combination fixed/variable-volume pumping system.

Also at NPE, HPM introduced two new screw concepts: It's Triple Wave Screw improves on HPM's Double Wave Screw and is based on the same proprietary principle; the patented Zig Zag design is said to offer dramatically improved dispersion over other screw designs. (See Extrusion section.)

Krauss-Maffei Corp., Plastics Machinery Div., Florence, Ky., whose German parent announced shortly after the show that it will acquire Swiss injection machine builder Netstal-Maschinen AG (Netstal Machinery Inc., Fitchburg, Mass.--see Industry Newsfocus), introduced a three-category series of injection machines. New B1, B2 and B3 machines have the same basic construction and feature standard MC3 controls. Clamping forces range from 65 to 880 tons on these hydraulic presses.

Pressures and speeds of category B2 and B3 machines are closed-loop controlled. B1 and B2 machines have variable-delivery pumps. B2 and B3 machines also feature a pressure accumulator. B3 machines have a "systems-separated" hydraulic system to enable movements of the machine and mold to be carried out simultaneously with plasticizing.

In order to make its machines available to a wider range of molders, Husky Injection Molding Systems Ltd., Bolton, Ontario, is expanding its modular, lower-cost "X" series of general-purpose machines from 250 to 4000 tons. According to Husky, one major difference will be reduced injection-pressure capability, from the 30,000 psi on standard machines to 20,000 psi on the "X" line. Accumulators will no longer be standard, but optional. In other respects, they're said to be "just as beefy" as regular Husky machines but cost about 20% less.

LARGE PRESS LINE EXPANDED

Cincinnati Milacron has added four more presses to its VL Series of large hydraulic presses. Last year, the company introduced the VL2000 and VL3000, with 2000 and 3000 tons of clamping force, respectively. At NPE, Milacron introduced two presses in the 1000-ton class and two in the 1500-ton class. The compact, low-profile machines are available in both square-and wide-platen configurations.

Cincinnati Milacron says the presses were designed to allow older plants to integrate larger machines into automation cells without extensive and expensive remodeling. The clamps have been designed with a headless ram with no piston rings for greater efficiency by reducing linear movement friction. Rapid traverse cylinders provide precise positioning control and sensitive mold-protection sensing through proportional-control valving driven by a real-time, closed-loop control.

SPECIALTY PRESSES ON DISPLAY

Krauss-Maffei exhibited a 165-ton press designed for making glass-fiber reinforced polyester parts. It's identical to Krauss-Maffei's new "B" range, except for its plasticizing unit and automatic material-feed system. Polyester resin is filled directly into the automatic feed system (mounted above the screw mechanism) from standard barrels using a barrel-lifting unit. The container can be filled before production to ensure a continuous molding process, says a Krauss-Maffei spokesman.

American Jet Stream, Inc., East Brunswick, N.J., introduced a 10-station coinjection press from Presma. It has dual injection units that work in conjunction with a rotary clamping mechanism to permit continuous injection while other parts cool. The press is aimed at applications mating elastic and rigid resins as well as using a less costly core material.

Engel introduced a line of standard injection molding machines without conventional tiebars. Available in 30-, 55-, and 85-ton models, these machines are said to take better advantage of the available tonnage of small machines.

Engel officials claim this is the first tiebar-less design that doesn't compromise clamp rigidity. They say omitting the tiebars enables molders to run larger, bulkier molds and offers simplified take-off options for automated parts removal. Engel says it already has over 100 such machines in operation in Europe.

Engel also introduced a line of vertical-clamp machines, built in North America, with shuttle and rotary tables for the growing number of insert molding applications. This line, which ranges from 25 to 200 tons, features an extremely rigid clamp module with a new bridge-type construction that's said to reduce clamp deflection to an absolute minimum. The injection and control modules are based on Engel's new line of ergonomically designed, high-precision, small machines.

BUBBLING INTEREST IN GAS

Interesting advances in the area of gas-assist injection molding turned up at NPE. Among them was a technique from Hettinga Equipment Co., Des Moines, Iowa, that doesn't require venting of the gas. Its "hot liquid gas" molding process is offered as an alternative to conventional gas-assist molding for making hollow parts. Hettinga injects a preheated, proprietary liquid into the melt stream at the nozzle. The heat of the melt vaporizes the liquid, which travels with the melt into the mold. Once in the cavity, the gas expands to hollow out the part and maintain pressure against the walls. Hettinga says the gas becomes dormant as it cools, remaining inside the part and not condensing back to liquid form. There's no need for vent holes.

Hettinga says that compared to other gas-injection methods, the injection pressure for its process is much lower--300 psi vs. more than 5000 psi--which it says makes it possible to use the process with virtually any thermoplastic, including those with low molecular weight, which are prone to blow-through. The liquid gas can also be turned on and off during the cycle to place it in specific sections of the part.

Converting a press to use hot liquid gas entails adding a container for the blowing liquid, changing the nozzle, and installing a control system. Initial costs include the hardware and a licensing fee of $75,000. There are no royalty charges after that.

Automotive Plastic Technologies, Inc., Sterling Heights, Mich., which exhibited in Sandretto's booth, is offering its proprietary Gastech molding processes and equipment for license. With the Gastech process, a conventional injection press is modified by the addition of a gas control unit. After a calculated short shot is injected into the mold, an inert gas (usually nitrogen) is injected into the melt stream under controlled pressure at either the nozzle, sprue, runner, or directly into the tool cavity. The gas forces the molten material outward from the center of the part, which is the hottest and has the lowest viscosity, along a predetermined network of gas channels to uniformly fill or pack out the extremities of the part. Finally, the gas is vented and the part ejected.

NEWS IN CONTROLS

Van Dorn Plastic Machinery Co., Strongsville, Ohio, which announced a joint research venture with Japan's Sumitomo Heavy Industries (see Industry Newsfocus), says it will be equipping all of its presses employing the Pathfinder-EL series controller with proprietary SPC software. This includes both the HT and HP series of presses. The software employs a user-friendly program and features a choice of 25 different parameters for performance measurements, as well as access to SPC data while the press is operating, according to the company.

Van Dorn continues to focus on compatibility between its controls and third-party supervisory systems. At NPE, it demonstrated new upload/download flexibility between its Pathfinder-EL controller and systems from Mattec and PlantStar.

Camis Systems, Inc., Erie, Pa., introduced two products designed to allow both large and small molders to implement either a management information system and/or process monitoring/SPC system at low cost. Process Pack reportedly provides an economical means to automate SPC on up to seven presses. It's designed to save labor hours and paperwork, and to prevent data erros by automatically sampling, analyzing, and charting the performance of various machine processes. As an option, Process Pack can transfer this data onto other systems. Historical reporting enables managers to perform trend analysis. Major features include control and capability studies, X-bar & R charting, press scheduling, and work-order generation. Price starts at $9000.

Also new from Camis is Entry Office+, an MIS package that includes order processing, sales analysis, purchasing, and inventory for smaller molders. A turnkey package combined with IBM's AS/Entry mid-range computer starts at about $25,000. The system is said to be upgradable to full MRP II.

Moog, Inc., East Aurora, N.Y., introduced MopacNET for process monitoring and networking of up to 99 machines. It connects Moog's Mopac 22 closed-loop controllers to one or more PCs. Machines not equipped with Mopac 22 may be served with Moog's new Sentry data-acquisition terminal (based on hardware from Production Process, Londonderry, N.H.).

Features of MopacNET include multiple user access (i.e., multiple PC workstations), remote access via telephone modem, network activity and process change reports, job summaries, downtime and reject reports, plant production status overview, operator identification, password protection, job scheduling, and machine setup and storage via MopacNET/Mopac 22 communications. One central PC with network software costs about $20,000.

Key to the network system is upgraded software for the Mopac 22. Even on a standalone basis, it now has new downtime and reject screens and the ability for the operator to enter reject counts at the machine. Also, Moog has increased the number of parameters to 14 on which limits can be set for automatic good/bad shot discrimination.

MOLDS AND MOLD-CHANGING

At NPE, Battenfeld of America, Inc., West Warwick, R.I., showed a new monorail-guided mold-changing system operating in conjunction with a BA-T 1600/630 press. This system has been designed to provide a rapid and economical means of changing molds in small- to medium-sized machines. It stores up to four 3-ton molds and performs mold changes in under 3 min without operator involvement, according to the company.

Automated mold-changing was also featured at the booth of Enerpac, Butler, Wis., which introduced the Quick Mold Change System, including a line of manual, semi- and fully automatic energy-coupling packages precision engineered to meet the most exacting QMC requirements, according to the company. Central to Enerpac's building-block concept are stainless-steel and brass clean break couplers. They're available in a range of sizes for connecting air, water, hydraulic fluid and hot oil up to 5000 psi. For electrical connections, Enerpac offers multiple pin connectors for hot-runner system thermocouplers, heating, and limit-switch applications.

Avalon Engineering, Inc., Boulder, Colo., introduced the Safetycycle Mold Press protection system, demonstrating it on a metal injection molding press in Battenfeld's booth. This machine vision system is said to save molds by inspecting for short shots and parts sticking in molds. The system reportedly performs both these tasks in 0.3 sec and then stops the press before the next cycle if there is a problem.

The system programs using English Script commands and is operated by pushbutton control after setup. It has 256 gray-scale analysis capability and operates on a standard 80286/386 PC platform. The $12,000 price includes ruggedized camera and solid-state adjustable light.

Gesswein & Co., a Bridgeport, Conn., supplier of mold-polishing tools, introduced a line of ceramic abrasive Supra Stones and Grinders. They are made of a new composite material of long, fine ceramic fibers and thermoset resin and are said to be thin, yet flexible, and virtually unbreakable.

ROBOTS KEEP COMING

Conair Martin, part of the Conair Group, Agawam Mass., took advantage of NPE to introduce its Sepro line of robots for presses from 100 to 5000 tons. Conair says the CNC-controlled robots with AC brushless servo drives are so advanced that absolutely no maintenance is required. The units include a four line alphanumeric display, said to simplify operation, programming, and troubleshooting. High-speed servo drive allows a max. instantaneous linear speed as high as 78 in./sec on some models, and with simultaneous combined movements on the three main axes, trajectory speed of 137 in./sec is achievable.

Conair says the new units are simple to program; up to nine different programs can be stored. Optional downloading to and from a PC is also available, as well as communications with a central computer network.

Conair also introduced a new robot from its Harmo line. Model HIM-SK has servo control on the horizontal axis, in addition to new Harmo hand-held controllers with alphanumeric display.

Star Automation, opening this month in Menomonee Falls, Wis., is a newly formed subsidiary of Japan's Star Seiki Co., Ltd. It introduced the Star BM Series high-speed servo-driven robots for presses from 50 to 550 tons, and the CY Series all-pneumatic traverse-type robot for presses from 25 to 300 tons.

AEC, Inc., Wood Dale, Ill., introduced the Excel-T 650 Series traversing pickers. They're said to combine the speed of a sprue picker with the flexibility and rigidity of a traversing robot. AEC says they're ideal for jobs on small-to medium-sized presses requiring more than a standard sprue picker can offer. Take-out time can reportedly be as little as 1.1 sec.

NEWS IN HOT RUNNERS

A.L.B.A. Enterprises, Inc., Torrance, Calif., introduced the Enrietti Thermoplay multigated nozzle to complement its hot-runner system. The nozzle is available in both a hot sprue version with up to eight gates or as a conventional nozzle used in conjunction with a manifold for multidrop applications. It features a new tip design that allows the nozzle to be lowered into the gate area farther, without blocking off the flow of plastic, thereby providing improved gate vestige, according to the company. Tips are said to be easily replaceable should they wear. They are available in three diameters with two, four, six or eight gates. Sources say they're suited for both high-volume resins and engineered or glass-filled materials.

Ewikon N.A., Inc., Concord, Ont., introduced its High Performance line of internally heated nozzles. They're said to have high mechanical strength and to be particularly suited to molding at high pressures with extremely short cycle times. The new design reportedly provides improved insulation, larger flow gap and, therefore, minimum pressure drop.

COMPONENT LINE EXPANDED

Cincinnati Milacron's energy-conserving Variable Power Package (VP) for hydraulic and toggle machinery has been expanded for use on all its presses with up to 1500-ton clamp force. Introduced last year, the VP package was originally available only on machines up to 500 tons. The package consists of a variable-speed, brushless d-c motor and a controller. On Milacron presses, it is used in conjunction with variable-volume pumps to match input power with output requirements of each phase of the machine cycle. The control software analyzes output requirements and adjusts motor speeds and power used to fit those needs, reportedly resulting in significant energy savings per cycle. According to the company, potential motor demand savings of a Vista injection press with VP vs. one without is 48%. Energy savings are said to be considerably higher with pre-Vista presses equipped with VP--as much as 74%.

Milacron also announced the availability of VP drives as a retrofit for its older machines through its Contract Services Business. Two retrofit variable-power drive configurations will be offered: The AC VariPower package is designed for the company's Vista injection presses. Taking advantage of the existing Vista control system, the AC VariPower adds an adjustable-frequency AC drive and the software to operate it. Also offered is the AC Smart Motor Processor, an energy-saving control mechanism for all other injection molding machines. This package consists of a Vista LC control, adjustable-frequency AC drive, control software to run on the VLC control and operate the drive, and hydraulic upgrades as needed.

MELT FILTRATION FOR INJECTION MOLDING

Two melt-filtering devices for injection molding were among the more novel introductions at the show. More molders are beginning to consider the value of protecting expensive, complex molds from becoming plugged by foreign particles in the melt, and such concerns are expected to increase with the use of recycled materials.

Gneuss, Inc., Langhorne, Pa., introduced a screenchanger for injection molding that is embedded in a plate that mounts against the platen. Inside is a wheel with several screen-pack modules. One module at a time is placed in the melt stream. When it becomes full, the operator causes the device to index another module into position. Dirty screen modules can be removed, cleaned, and replaced through an opening on the side of the plate.

Spear System, Inc., Camarillo, Calif., introduced the Super Cycle system first shown at JP '90 (see PT, Jan. '91, p. 60). One element of the patented technology is a hold-pressure device that fits onto the end of the barrel. It contains a valve and a small melt reservoir. Once injection is complete, the valve turns, cutting off flow from the screw, and a separate hydraulic cylinder maintains holding pressure with the melt in its reservoir. This allows immediate screw recovery and faster cycles.

The second element of the Super Cycle technology is a melt-screening system that fits onto the end of the screw. A filter plate with five slits of 10-mil diam. engages the I.D. of the barrel and prevents larger particles from passing. The particles merely remain in a reservoir area at the end of the screw, behind the filter plate, and reportedly do not cause any pressure drop. Accumulated particles can be purged by retracting the injection carriage and advancing the screw until the filter plate clears the end of the barrel. The entire Super Cycle system costs $25,000. The filter system is available separately for $10,000.