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Injection molding.

Injection Molding

K'89 was a hotbed of product introductions for injection molders. New modular, high-speed, and tiebar-less machines, enhanced controls and supervisory computer systems, "expert system" troubleshooting aids, new robots and other parts-handling devices, integrated CD manufacturing systems, and novel processes for liquid-crystal polymers, foams and hollow, complex parts--all provided attendees with a look at how injection molding will evolve into the 1990s and offered proof that injection molding will continue to be among the most innovative of plastics processing techniques.

A common theme of injection molding exhibits was new supervisory computer systems for cell control. While there are many differences among the systems, one thing they all share is statistical process control (SPC) capability. Processors considering these systems need to determine what capability they have, if any, for accommodating competitor's machines. Here's what's new:

* Boy Machines is offering an optional "CIM system" for use with its new Mipronic-Plus controls. Software compiles all required setup and process data, including special-purpose programs for SPC and production planning.

M Mannesman Demag and Bucher-Guyer (represented respectively by JMG Associates and Bucher, Inc.) are offering the same basic system developed by Demag, which Bucher has adapted for its thermoset machines. The CAS/CAP Information System can be integrated with the NC III machine controls (it's now standard on Bucher systems) to provide a view of production from up to 64 machines, and keep statistics on each shot, such as injection time, plastication time, cushion size, and total cycle time. (Production and SPC monitoring require separate IBM-compatible PC's.) Users can monitor any variable on any machine, choosing both the sampling frequency and number of shots per sample. Process data can be correlated with data entered manually or automatically on shot weights or dimensions. Notes can be entered on the SPC charts indicating events such as the start of a new lot of material.

K Klockner Ferromatik Desma has a new COMline host system that can display current and scheduled molding jobs, optimally assign jobs to machines using its own guidelines, compile monthly and shift-by-shift reports, and retrieve setups from a high-capacity storage unit. The system can also download changes in parameters into the machine controls.

* Other suppliers introducing supervisory computer systems at K'89 included Krauss-Maffei, Engel, MIR, Netstal, Battenfeld, and Stork Plastics Machinery (rep. by Phil Smith & Associates). Arburg (rep. by Polymer Machinery Corp.) enhanced its existing supervisory system so that it can accommodate up to 16 machines.

PC's MOVE MACHINE-SIDE

A lot of machinery suppliers introduced new or improved controls taking advantage of the latest in computer technology. In fact, a trend at the show was towards the use of standard personal-computer hardware and software for direct machine control:

* New controls from Hettinga Equipment employ factory-hardened 80386-based IBM PS/2's with OS/2 operating system and IBM's Presentation Manager software. This technology can provide graphic display with multiple windows illustrating several parameters simultaneously on one screen. It also can store up to 2000 mold setups, vs. a max. of 60 on previous systems.

* A new operator interface from Husky Injection Molding Systems also has multi-window capability and is also based on a factory-hardened IBM-compatible PC with high-resolution color monitor and soft-touch keypad. Among other capabilities, it can directly control auxiliaries using the SPI communications protocol.

* Klockner Ferromatik Desma also introduced controls with multi-window capability for its FX line of machines. Its "picture-in-picture" function lets an operator alter the values for one parameter while all the other parameters are displayed on the same screen in reduced scale.

Other suppliers at the show offering new controls concentrated on improving ergonomics and the operator interface:

* Billion SA says its DIXIT controls feature a sharper, touch-sensitive, iconic, color-CRT interface for setting parameters. The controls are also available on a new 420-ton machine that also features a "very long" opening stroke, automatic die-height adjustment, and choice of two platen sizes.

* Boy's Mipronic-Plus controls also offer improved resolution and mount the display and keyboard directly on the cover of the injection unit.

* New Sycap-Graphtrack controls from Netstal may be the first to introduce a "trackball" interface to plastics machinery. It's a handy device, similar to what's used in video games, for moving the cursor arrow. Graphtrack involves extra optional software, to become available in June, which differs from standard Sycap controls in that it graphs injection and hold pressure, and does it in 10 steps rather than five. The user can draw the desired profile or select discrete points and let the computer integrate between them. On each cycle, it displays set and actual curves. Setting the cursor at any point on the curve with the trackball produces a readout of the pressure value.

* Two new controls from Stork, the CDS 485 and the CDS 500, reportedly improve ease of operation by regrouping function settings more logically. The CDS 500, which was exhibited at the show but won't be available until later this year, features large memory capacity and greater speed to help customers custom-configure their systems.

* New controls for Arburg's new All-rounder M machine line are said to automatically adapt all relevant parameters when another parameter is changed. Manual changes are no longer necessary, according to the company.

'EXPERT' SOFTWARE

"PASS" Problem Analysis and Solutions System, is a new "expert system" troubleshooting aid from Plastics & Computer Inc. This qualitative analysis software is meant to complement the quantitative molding analysis provided by the firm's TMC software. For use at the shop-floor level on an IBM-compatible PC, the software leads the user through a multiple-choice, question-and-answer process to define the molding problem and the conditions that produced it, so that the computer can ultimately identify a cause and suggest corrective actions. If no cause can be identified, the computer will say so, or will display possible causes generically related to similar problems.

The user can customize the program, editing the language to reflect terms used in his shop, adding new choices to the multiple-choice format, and creating a database for specific molds and machines--e.g., cataloging past problems and solutions and possibly ruling out certain solutions as not applicable. It cab also serve as a learning tool--for example, preparing a report every week on problems for which no solution was found.

Like the rest of the TMC software, PASS is based on statistical analysis of a large empirical database of actual molding experience. It costs $5000, but is sold only to users of the TMC software for mold and process analysis. That's because the one diagnosis that has been left out of its logic is that your mold design is wrong to start with.

INJECTION ENERGY CONTROL

There appears to be some new interest in the use of injection energy--or the integral area under the curve of the injection pressure profile--as a process monitoring and control variable. Battenfeld has been offering a closed-loop injection energy control feature for about a year. This is a same-cycle correction technique that can change the boost-to-hold transition point and holding-pressure level to maintain a consistent value. One W. German toymaker is reportedly using this feature instead of closed-looop servovalve injection control.

What's more, Phillip Leopold, general manager of Bucher, Inc., is encouraged about the potential value to thermoset molding of monitoring the integral of the injection-pressure curve (based on hydraulic or cavity pressuree as a measure of total work performed on the material. A change in the area under the curve could provide a useful warning of changes in material viscosity, says.

MODULAR MACHINES

Besides controls, K'89 was also notable for the number of machine models introduced. Modular designs have become a big thing. This approach offers interchangeable standardized components to allow molders to mix-and-match various clamp forces, shot weights, controls, and other components to meet their specific requirements while keeping costs down. Battenfeld's recently introduced CD Plus line is described as tailor-made machinery in "componentized" form, offering a multitude of possible combinations at lower cost than non-standard configurations would have cost in the past (see PT, Nov. '89, p. 79). The CD Plus line replaces the previous CD and E series at prices that can be as low as the E ("Economy") line. That's because the lower-cost Unilog 2040 control of the E series was not available before on CD models.

With all the new modular choices, the automatic barrel-changing system on the CD Plus has been upgraded to permit exchanging barrels of different sizes and lengths. The quick-materials-change hopper slides forward and back on its base to accommodate different feed-opening positions on the interchangeable barrels.

Sandretto introduced its modular Serie Otto line (see photo) as a successor to the Serie Sette. It offers nine injection-unit options for each clamp size--three shot volumes at three L/D's. The new models--the first two are 65 and 390 tons--also boast wider platens and tiebar spacing (with even larger platen and mold areas available as a new standard option), longer strokes, and more powerful ejectors.

Other new modular series include the NB II line from Negri Bossi in 110 to 330 tons; MIR's Futura line (49-410 tons); a 463-tonner from Billion; and a new modular versions of Demag's D line (44 to 4000 tons).

IMPROVING ACCESSIBILITY

If tiebars are getting in your way, some machinery suppliers are working towards improving access to the platens for mold mounting and removal. Engel exhibited a 28-ton machine with a tiebarless C-clamp design, and Italian supplier Metalmeccanica Plast, S.p.A. introduced a machine featuring "automatic" tiebar removal.

Metalmeccanica Plast (owned by Sandretto but not yet marketed in this country) has a new Pentatron line of 38 to 1100 tons, featuring automatic tiebar removal. They employ a locking device based on hydraulic brackets to attach the removable tiebar to the moving platen. The tiebar can be removed by unlocking the hydraulic brackets, which releases the tiebar from the moving platen, the mold platen, and the mold platen gear. When replacing the tiebar, a clamp-force control on each tiebar is said to ensure correct tiebar resetting. Four transducers mounted in hollows of the tiebars control the "stretching" of each tiebar, which is displayed on the machine control.

Engel's new tiebar-less design will become standard for its small machines from 28 to 45 tons. Instead of clamping force being absorbed by the tiebars, this is done by a very rigid frame in the form of a reinforced C profile. A new type of joint between the moving platen and the piston of the hydraulic clamping unit is said to guarantee exact parallelism of the platens despite slight deformation of the frame as it takes up the clamping and locking forces.

FOR PACKAGING AND

HIGH SPEED

Netstal's new HP (High-Performance) Series includes eight model ranging from 110 to 385 tons. They have accumulators for very fast injection of thin-wall packaging, PET bottle preforms, medical equipment, technical parts with short cycles, and in automated configurations. The 220-ton model and a minimum dry-cycle speed of 1.4 sec. Injection ram speed can be up to 40 in./sec., more than twice as fast as Netstal's N Series. Bigger, stiffer platens and beefier frames are other features. Increased speeds of 20-30% relative to previous Netstal machines reportedly have been confirmed in production of thin-walled products such as PP base-cups and PS drinking cups. The HP Series will be equipped with Netstal's new Graphtrack controls, described above. Also, closed-loop clamp-force control and automatic die-height adjustment are standard on the HP models, optional on the N Series.

Incidentally, Netstal has a new partnership with the W. German firm SysTec, to supply turnkey production systems for thin-wall packaging. SysTec, which is owned by Uniplast, one of Europe's largest food-container manufacturers, provides molds (especially stack molds), parts-handling, and stacking/packing auxiliaries. One example of SysTec's patented technology is a novel take-out system built into the mold. Suction-equipped flippers whisk parts into guide rails beside the mold--reportedly faster than without a take-out mechanism at all, because the mold is opened less widely than usual. A mold-security system confirms the presence of a part in the flipper suction cups.

Stork's new SX series of medium-tonnage toggle machines are also being recommended for precision parts and packaging. With a new five-point toggle system driven by a redesigned hydraulic cylinder, they feature high speeds, rigidity, and a positioning accuracy that's said to be better than 0.5 mm. The series includes the T-range for precision parts and the P-range for high-speed, thin-wall production. The P-line is said to provide vibration-free operation with dry-cycle rates of up to 25/min. (See also Sept. '89, p. 42).

BIGGER MODELS FROM SMALL-MACHINE

SUPPLIERS

Boy Machines introduced the Boy 80 M injection molding machine with 88 tons of clamping force, its largest machine thus far. The 80 M's basic engineering corresponds to that of the Boy 30 and Boy 50 presses, but there are some improvements. The entire clamping unit is accessable from all sides. The injection unit has also been completely redesigned. The two nozzle clamping cylinders and the injection cylinder are built within a single casting. Only the piston in the injection cyclinder moves during injection, resulting in a reduction in the masses in motion for improved accuracy in injection control.

The hydraulic system has also been redesigned by adding special damping of pressure peaks to keep noise to a minimum despite more rapid component movements. Two different controls are available: the new Mipronic-Plus on the Boy 80 and standard Dipronic controls on the Boy 80 T2.

Arburg's machines are also getting bigger. In fact a new addition to its Allrounder line, the Allrounder V 2000-630, with clamp tonnage of 220 tons, falls into the medium-sized category. Arburg sources describe the machine as a completely new concept. Unusual, off-center injection points in special molds can be obtained on the Allrounder V by infinitely variable horizontal mobility of the injection carriage. Thus, a greater number of parts can be end gated for more uniform melt orientation throughout the part. It also provides an alternative to vertical parting-line injection in cases of limited headroom. The horizontal injection position of the Allrounder V can be programmed and stored together with other machine parameters.

Also introduced at the show was the Allround M. The machine will be available in sizes ranging from 28 to 94 tons, clamping areas of 35 to 51 in., and shot sizes ranging from 0.8 to 6.3 oz. The injection and control unit are newly designed. The controls now regulate barrel temperatures and control the strokes (via linear transducers) directly from the new Multronica CRT control, eliminating former "off-screen" settings via switches and separate temperature controls. A new injection unit joins all power connections to the plasticating cylinder in a central connector.

OTHER MACHINERY DEVELOPMENTS

Nissei Plastic Industrial Co. introduced an 80-ton machine at the show that makes innovative partial use of the electric servodrive that Nissei first introduced in 1984 as an alternative to hydraulics for injection machines. The 80-ton PS80S12ASE was incorrectly described in our September pre-show report as an all-electric servo machine. In fact, it uses a servodrive only on the injection unit, to provide very precise control where it's most needed. The clamp uses conventional hydraulics because, as Nissei president Tsukasa Yoda told PLASTICS TECHNOLOGY, control of the clamping end is less critical, and good repeatability can be provided at lower cost with hydraulics. This compromise helps reduce the cost premium for electric servodrive machines.

New from MIR is the HMP 1350, a horizontal machine with 1485-ton hydromechanical clamp and two injection units. At Dusseldorf, the machine molded four 5-gal buckets in two colors simultaneously on a 34-sec cycle.

Also new from MIR is an additional model in its recently introdued Futura Series. The RMP 190 Futura (205 tons) was equipped with new controls, the Captrol 2 Dis Plus, which features LCD display and a keyboard with 27 function keys.

This machine was also equipped with novel magnetic platens for quick mold locking and a semiautomatic moldchange system consisting of a motorized carriage with a handling bed and an upper platen. It has two independent series of rollers moveable alternately in parallel to the machine axes. The mold is premounted on two support plates, which are fixed to the machine by means of a shrouded-bracket locking system. To change the mold, the bracket system is integrated by two small roll guides mounted on both the moveable and fixed platens, which work as a ledge for the mold holding plates.

Hettinga Equipment introduced a "Little Giant" machine for molding parts of 27 to 110 lb in size. It's mounted on three tracks, allowing it to index laterally to inject from two to six molding stations. (Hettinga's smaller systems have rotary injection units feeding multiple clamps.) The clamps can be of varying sizes to produce different parts and can be injected in any sequence.

Klockner introduced what's said to be a new energy-saving drive system with two motors on its large W-Series machines, as well as a new hydromotor screw drive thaths also said to save energy and provide higher rpm and variable torque without gears. The CRT controller displays plasticating energy consumption in kw/kg.

Klockner also announced that in the second half of this year it plans to inroduce the first of its "unified" K Series, which will integrate the formerly separate FX and W lines, whose external appearance has already been "harmonized," and eliminate any overlapping sizes.

BOY TENDS BAR

As at most shows, suppliers were anxious to make a splash by showing off their finesse at automation and complex processing setups. Among several highly automated exhibits was one from Boy Machines that molded a cup, pad-printed a logo on it, and then filled it with beer and delivered it to thirsty onlookers.

Battenfeld Austria demonstrated an unusually complex, three-material molding job that produced a hockey puck with a flashing light molded in (see photo). The puck consisted of a printed circuit board and batteries, which was encapsulated by three injection machines linked by two robot systems and controls tied to a central computer. The first machine encapsulated the electronic gear in a clear, red-tinted PVC, which forms built-in lenses. The flashing light is concentrated onto the lenses by jacketing the casing in white polypropylene in the second machine. The third machine provides an outer, skin of black, impact-resistant TP elastomer. Finally, the pucks are automatically weighed to an accuracy of 0.001 gram, tested to see that the light works, and printed by a hot-embossing process.

Another automated Battenfeld exhibit showed off a new "fast-shuttle" linear mold-changing system, which served a production cell with two injection machines. The system is said to be distinguished by its modest cost and the time-saving simplicity with which it can be installed. Unlike track-mounted or stationar systems, this shuttle is reportedly the first to employ standardized components and controls that are also used for robot applications (linear robot system components, servo drives, planetary gears, and the Unilog 9000BR controls). The linear unit requires only two mechanical points of support per machine and/or magazine--i.e., no more than six points of support altogether.

Similar to some robot handling systems, the shuttle is arranged longitudinally along the rear side of the two machines, which are arranged end to end. The mold carriage runs on this linear unit at mold-loading height, driven by two three-phase servo motors. A mold magazine located at the end of the second molding machine has one preheat station and room for three more molds in reserve.

INTEGRATED CD MANUFACTURING

Another automated exhibit introduced the Uniline, a brand-new, self-contained clean-room cell for manufacturing 80-mm or 120-mm optical discs, from Netstal. This system, of the so-called "monoline" type, is built by First Light Technology, Inc., Saco, Maine, a new automation subsidiary of Netstal-Machinery Inc. (First Light also developed Netstal's new Graphtrack controls, described above.) This self-contained system contains a vacuum metallizer of the firm's own design, spin coater, uv-curing station, two-color Dubuit silkscreen printer with uv cure, and q-c inspection station. This preassembled system is designed for reliability and complete accessibility. All operating parameters are programmed from a PC, which also monitors the injection machine. The metallizer processes one disc at a time in 4.5 sec. The q-c station, from Automatic Inspection Devices, checks reflectivity, birefringence, I.D., O.D., eccentricity, and looks for pinholes and scratches--all in oen revolution of the disc. A complete q-c report is displayed on a color CRT.

The system is supplied for $1.25 million, complete with 60-ton Netstal Disc 60 molding machine, Robi-Sprint hydraulic take-out robot, and GPT Axxio (formerly Nagron) CD mold. The latter has a titanium nitride (TiN)-coating that's said to enhance stamper life, and a reduced sprue size to give a faster cycle. The system is guaranteed for a 7-sec cycle, though one customer is said to be running at 6.4 sec.

And that's not all for CD's from Netstal. Netstal is cooperating with Optical Disc Mastering (ODM) of the Netherlands, sub. of Philips Du Pont Optical (PDO), to supply complete CD-ROM plants--data formatting, recording, mastering, stamper manufacturing, and disc manufacturing with a Netstal Uniline. The LHH 8000 system is a modular, prefabricated, pretested, containerized system with integrated clean-room facilities, main electrical control, and air-conditioning and water-purification modules. It occupies 50 ft square and requires only electricity, tap water and drain, plus one to three operators and a technical supervisor. Turnaround time from tape to disc is claimed to be only 6 hr. It can be up and running in four weeks, providing 90% total yield, according to company spokesmen. Price is $5.5 million complete.

INNOVATIONS IN PROCESSING

As reported last month (PT, Dec. '89, p. 14), Klockner introduced at the show a "push-pull" molding technique for optimizing the properties obtained from liquid-crystal polymers (LCP's). Typical molded LCP's exhibit a highly oriented skin and amorphous core. To develop maximum properties, the core should be oriented, too. Klockner has found that this can be accomplished by injecting a part at two points, using a multicolor molding press, and alternating injection and suckback with both injectors so as to oscillate the melt in the cavity (see schematic). This can have the added virtue of virtually "erasing" the weak weld lines that can plague LCP moldings.

Test data reported by Klockner in the November 1989 issue of the W. German journal Kunststoffe (to be published soon in English in the same edition of Kunststoffe--German Plasticse showed that, as compared with a standard end-gated tensile bar, a push-pull molded bar could achieve tensile strengths 32% higher for 30% glass-filled LCP and up to 95% higher unfilled. Compared with a tensile bar injected at both ends to form a weld line in the middle, but with no push-pull action, tensile strengths were as much as 177% to 532% higher, respectively.

Klockner sources say push-pull molding could also be useful for molding ceramic and metal-powder compounds utilizing plastic binders, in order to optimally orient whisker reinforcements.

Incidentally, Arburg demonstrated injection molding of ceramics and metal powders at the show, highlighting its experience in an area that has heretofore been promoted primarily by Japanese injection machine builders (see PT, Feb. '87. p. 29 and Jan. '89, p. 64). Not only does the abrasiveness of the material require special wear-resistant machine construction, but special techniques for gentle and highly consistent treatment of the melt are also required.

Engel showed at its booth a new variant of the "lost core" technique for molding complex hollow parts, in this case using cores not of low-melting metal alloy, but of a special water-soluble polymer from Belland AG of Switzerland. (See PT, Sept. '89, p. 14).

And Hettinga is promoting its own process that can produce the same sort of complex, hollow parts without the expense and technical difficulties of the lost-core process. Hettinga advocates molding an inner liner of the part in two pieces by conventional techniques. Then the two pieces are assembled to gether in a second mold and are over-molded with more material to bond the halves together and provide structural integrity. What could be simpler?

Hettinga has pioneered the process of low-pressure injection molding of rigid backings onto soft fabrics for automotive interior and furniture parts. At K'89, Engel introduced its own low-pressure approach for such applications. By using a special machine and mold technology that it has dubbed Textilemelt, Engel says it can make plastic-and-textile laminates, and overcome the difficult challenge of molding onto velour-type fabrics with soft-foam backing. Both low pressures and preparing the melt at low temperatures are said to be the keys.

Hettinga also is offering a new approach to molding foam-core parts with solid skins. This "Controlled-density" process is a variant of Hettinga's existing Thermoplastic Cellular Molding (TCM) process, which uses a chemical blowing agent and prefoaming in the barrel to achieve precise shot uniformity. This proprietary method is a one-shot technique that uses one resin, one injector, and one injection point to produce density reductions up to 60%, vs. 22% with standard TCM. The core desntiy and skin thickness can be varied controllably, says Hettinga. Gas counterpressure can be added to achieve a smoother surface.

Meanwhile, Sandretto is now offering a special hardware and know-how package for gas-counterpressure structural-foam molding, based on five years of development. Sandretto says it has overcome problems that have limited application of this smooth-skin technique until now. New patents on this technology have been granted to the French-based Societe Europeenne d'Expansion (S.E.E.), a joint venture of Sandretto and Vape, a French molding conglomerate. Sandretto can recommend particular moldmakers and offers technical advice on mold design and material formulation (choice of blowing agent), as well as equipment with special nozzle and screw designs.

ROBOT NEWS

Husky introduced a family of top-entry servo robots for machines over 1000 tons. They're available in a variety of configurations and standard strokes, with up to six axes of movement and a peak velocity of 39 in./sec with payloads up to 330 lb. All linear axes may be servomotor, brake-motor, or pneumatically driven. Rotational movement is provided by either a hydraulic rotary actuator or servo-electric motor. Robot control functions can be operated from standard Husky machine controls. A free-standing Husky robot control is provided for retrofit applications to other injection molding machines.

Remak, a subsidiary of Klockner Ferromatik Desma, introduced the EX 550 swing-out sprue remover. It has a pneumatic vertical main stroke, which is said to be steplessly adjustable from 0 to 31 in. Its dedicated control system enables the selection of any of 10 different takeaway programs, or it can be integrated with the machine's controls if the two are purchased jointly. The robot reportedly can remove sprues in as little as 0.7 sec.

Wittmann Robot Systems (represented by Automated Molding Systems, Inc., New Hartford, Conn.) introduced the W 40 sprue picker. Iths described as a very compact design for extremely fast applications. The vertical air cylinder has two piston rods for high stability. The sprue gripper is directly attached to the rods. Compressed air is supplied through one of the rods, avoiding any external tubing and providing extremely fast movement with the smallest opening gaps of the mold, says a source. A quick-release feature is provided to ease setup for mold changes. The rotation and tilt movement are integrated in one block and are said to be easily adjustable. Also provided are microprocessor controls with a hand pendant and teachin programming. Twenty programs can be stored and recalled.
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Title Annotation:K'89 Report
Author:Fallon, Michael
Publication:Plastics Technology
Date:Jan 1, 1990
Words:4564
Previous Article:The nineties roundtable: processors talk to materials and machinery suppliers about their future roles.
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