Bigger, faster, more accurate RIM and urethane machines at K'89.

Bigger, Faster, More Accurate RIM and Urethane Machines at K'89

There were quite a number of unusual developments in clamps, metering systems, and mixheads for urethanes and RIM at K'89. Exhibitors tended to emphasize high-capacity machines for large auto parts, fast-setting polyureas, RRIM and structural RIM (SRIM). But among the biggest news of the show in RIM/urethane machinery was a pair of new business alliances. First, Battenfeld sold its RIM and urethane machinery division to Klockner Ferromatik Desma (U.S. offices in Erlanger, Ky.). As we reported in December (p. 90), Battenfeld's RIM systems for large automotive fascia-type parts complement Klockner's specialty in rotary-table systems for smaller RIM parts, such as steering wheels and headrests.

Second, Cannon of Italy (with U.S. offices in Mars, Pa.) now can offer proven technology in continuous slab and panel processing, thanks to its acquisition of Viking of England from the West German PTI Group. Viking is licensed to supply the patented Vertifoam, Maxfoam, Varimax, and Plani-block systems.

Partly as a result, Edge-Sweets (PTI) Co., Grand Rapids, Mich., plans to resume building continuous foam bun lines there. V.P. of sales and engineering Dario J. Ramazzotti notes that the PTI Group retains the rights to build Vertifoam systems.

BALL-SCREW METERING DEBUTS

A novel metering mechanism for RIM and other high-pressure machines was introduced by two suppliers. For small shots, Cannon of Italy (with U.S. offices in Mars, Pa.) introduced a nonhydraulic piston metering action on its new Model S20 high-pressure system. The electronically controlled pistons are driven by a ball screw and induction motor. A special magnetic clutch transmits drive force from the motor to the pulley; thus motor speed remains constant while the pulley speed is varied through electronically controlled changes in the magnetic field within the clutch. A tachometer gives actual rpm, a direct indicator of actual flow rate, which is fed back to the motor controller for closed-loop speed and flow regulation.

This system is said to provide unusually high accuracy in metering small shots for components such as steering wheels, gearshift knobs and other integral-skin parts, small cavity-filling jobs (car body pillars), and spray applications that require outputs of no more than 140 cc/sec per component. (CIRCLE 50)

Meanwhile, Impianti OMS SpA of Italy (represented by IFTA Canada Inc., St. Martin Laval, Quebec) introduced a combination of ball-screw metering control with hydraulic drive on its new RIM-Master series. This series of lance-cylinder machines is designed for RRIM, especially the new fast-cure polyurea systems. In order to combine high output (up to 17.6 lb/sec) with high accuracy, these systems use a patented Dual-Drive arrangement. A simple hydraulic pump and gas accumulator unit powers hydraulic cylinders that are attached to the metering lance by a rigid yoke. The hydraulics provide only the motive force for metering; control is furnished by a high-resolution ball-screw with a small d-c drive, which is used only to monitor and control the rate of movement of the lance. This system is said to use only about half as much energy as other systems for comparable output rates.

OMS also offers entirely ball-screw driven systems for low outputs (down to 100 g/sec) of unfilled, low-viscosity systems without leakage. (CIRCLE 51)

Another unusual technology, which is reportedly applicable to all types of high-pressure urethane metering machinery, is automatically self-flushing pump seals from Elastogran Machinery (EMB). Robert L. McBrayer, v.p. of EMB's U.S. branch in Wyandotte, Mich., says timed auto-flush cycles greatly reduce the seal wear that occurs when many PUR processors fail to service the pump seals daily. Cannon says it uses this type of seal on its Model "a" machine. (CIRCLE 52)

MORE NEW RIM SYSTEMS

Klockner's main new entry at the show was the PU 2000 RRIM system, developed by its Desma group. Among the most significant features are a single microprocessor control and single hydraulic system for both metering and clamping units, a relatively unusual arrangement that is said to minimize cost. All metering and clamping parameters are entered into the controller in physical values; actual values for injection pressures are displayed graphically. Core-pull action is freely programmable.

Also interesting is the use of three metering cylinders - one for isocyanate, one for polyol, and a second, smaller cylinder on the polyol side for prepressurizing the material before injection. This is said to be especially valuable when using high levels of nucleating air, rendering the mix more compressible. Precompressing the polyol/air mix to 500 psi reportedly ensures synchronized metering and reduces the pressure build-up time that would otherwise be necessary. Incidentally, a density scale at the air-charging station provides continuous closed-loop density control.

Closed-loop metering control is also provided, using metering pistons with integrated servovalves and position transducers, which reportedly allow settings to be adjusted with extremely fine resolution.

The accumulator-assisted metering system can deliver up to 210 liters/min; double-jacketed tanks have a special stirrer on the polyol side and level control by means of load cells.

The clamp (available in a horizontal version) has separate traversing and clamping cylinders in order to save energy; it comes in 165, 220 and 275 tons, with mold area up to 100 x 44 in. It's said to be very fast-acting, with speeds over 16 in./sec. (CIRCLE 53)

Klockner's other news was a new controller for its PSA 74 22/23 system, which offers more complete and accurate process monitoring - including temperature and pressure sensing at the mixhead, pump and tank, with tolerance bands on each parameter and automatic shutdown if they are exceeded. The system also monitors throughput, ratio, shot count, and material consumption for each component. (CIRCLE 54)

POLYUREA, RRIM AND SRIM

For polyurea RIM and RRIM, where high output is a necessity, a new Cannon metering unit is built to deliver more than 10 liters/sec, while reportedly consuming no more power than a machine with only 25-33% of that output. The system utilizes multiple accumulators to provide materials feed at pressures of 2175 psi or higher. Metering accuracy is achieved with electronically controlled proportional valves that reportedly have response times as fast as 20 millisec. (CIRCLE 55)

Also new is Cannon's Trio mixhead for polyurea, capable of up to 10 liters/sec output at 2:1 ratio. To attain such high throughput, the higher volume component stream is split into two, so a total of three jets of material enter the mixing chamber at angles of 120 [degrees] to each other. This design reportedly eliminates the mutual interference typically generated by the difference in output volume, pressure, and viscosity of the two material components. And, since at such high delivery rates, fast termination of the shot is essential to prevent overfilling of the mold, the Trio head has a short mixing chamber, and the 28-mm stroke of the cleaning piston is accomplished in only 40 millisec.

Also new in mixhead design is the remote-control (Reco) nozzle concept, which is just being introduced commercially this year. This system, said to be suitable for high-output polyurea applications, as well as RRIM and dual-hardness foam seating, reportedly maintains constant injection pressure by varying the nozzle diameter according to the output rate. What's more, this is achieved in a compact head design, according to Cannon USA's Bruce Mazzoni. Automatic injection-pressure control is valuable for applications such as automotive fascia, since it permits SPC documentation of the actual pressure used.

In the Reco head, there is no diverter valve - instead, the injection nozzles retract for low-pressure recirculation through the head between shots. Recirculation through the head is essential for RRIM, says Mazzoni, because the filler could settle out in the lines otherwise. (CIRCLE 56)

(This is not the first appearance of servocontrolled nozzles; Edge-Sweets introduced them about two years ago. And, as seen below, others are coming out with them too.)

Krauss-Maffei (U.S. offices in Florence, Ky.) also has an improved mixhead for RRIM; this linear, short-stroke head now incorporates a full-length piston channel in the mixhead plunger, in place of the recirculation groove in earlier designs. Thus, the passage from the nozzle to the return line is now unrestricted, causing less fiber breakage and better part surface finish, according to the company. Also, the polyol flow rate reportedly can be increased many times over, owing to lower backpressure, which also contributes to longer service life. Finally, the absence of the recirculation groove permits a more compact design. (CIRCLE 57)

And Krauss-Maffei, like Cannon, has adopted the concept of hydraulically controlled orifices to automatically adjust mixing pressure to changes in throughput rate or component viscosity. A hydraulic servo system pushes the piston needle against the injection nozzle; the nozzle pressure is set from the control panel, and actual pressure is measured by a transducer. This configuration (which can be retrofitted onto existing heads) is part of the fully closed-loop control on K-M's new RIM-Star B series of axial piston-pump metering systems, which also have close-loop control of flow rates and shot times. Douglas L. Lammon, marketing/sales manager for the U.S. RIM Div., says the B Series is outstanding for its precise accuracy. Servovalve control of the metering pumps, he says, allows output to be changed very fast - shot intervals can be as short as 2.5 sec - and with accuracy as fine as [+ or -] 0.2-0.3%, whereas [+ or -] 0.9% has been typical before. Such accuracy reportedly can pay for itself in materials savings; and the versatility to change shots quickly and exactly is useful for filling a variety of molds on a carousel. (CIRCLE 58)

Elastogran Machinery also has a new short-stroke mixhead, aimed at SRIM. According to Bob McBrayer, these systems tend to be low-viscosity and very adhesive, with a tendency to jam conventional mixheads. The company has another new mixhead design that's said to be lighter in weight and easier to maintain. (CIRCLE 59)

Hennecke (represented by Mobay Corp.'s Machinery Group, Pittsburgh) approached the challenge of high-output polyurea RIM and RRIM processing with the new RIMdomat HS 10000-2.5 piston metering system and new MP 4 mixhead, capable of up to 20 liters or 44 lb/sec. The metering pistons each have a special linear-amplifier drive. Piston speeds are controlled by counting pulses at preselected frequencies up to 10 kHz (10,000 pulses/sec); each single pulse actuates a microscopic stroke movement of the piston. This system reportedly eliminates the need for making closed-loop corrections in piston speed, since it is always accurate in the first place. Also, Hennecke says this approach controls piston speed exactly, regardless of backpressure, which is especially important at the critical switchover points at the start and end of a shot. (CIRCLE 60)

The MP 4 mixhead uses Hennecke's approach of impingement mixing just before the exit of the head. This eliminates the need for a cleaning piston - since there is nothing to clean - and is especially advantageous with sticky polyurea systems. The new head reportedly also provides unusually fast switchover from recirculation to dispensing - i.e., around 3 millisec, vs. 10 millisec in the past. (CIRCLE 61)

Cannon also had a number of developments for SRIM. Its Compotec system now incorporates variable-output metering, which can be programmed to inject fast initially and slow down just before the mold is full, to prevent a pressure "spike" at the end of filling. Cannon's Mazzoni says this feature could be useful in other applications as well. (CIRCLE 62)

Cannon also showed how a compact package of four metering cylinders (two A-side and two B-side) could be used for fast filling of very large SRIM or other parts. Such a system, occupying less than 1 sq meter, could be used with twin mixheads to fill a large part at two injection points, or to fill two smaller parts at once. Faster filling is achieved without a runner, says Mazzoni. (CIRCLE 63)

MONSTER CLAMPS ARE 'IN'

For polyurea RIM and SRIM in general, higher-tonage clamps are all the rage. Cannon, for example, has built up to 600-ton models and has quoted up to 800 tons. Krauss-Maffei has actually sold an 1100-ton RIM press, the largest in its Orion series, to a European chemical company. These four-tiebar units (also available in 275 and 495 tons) have separate traversing and clamping cylinders (as on the Klockner machine described above), and reportedly operate at speeds up to 960 in./min Dry-cycle times of 20 sec are said to be attainable at full stroke and platen tilting; without tilting, dry cycles reportedly can be shorter than 10 sec. (CIRCLE 64)

New RW and RWS (tilting-platen) series of RIM/RRIM presses with clamp forces up to 495 tons and platen areas up to 120 x 44 in. are built specially for Hennecke by Wemhoner Spezialpressen. Closing speeds can be up to 1200 in./min, clamping speeds to 400 in./min, and platen booking times (both platens) from 0 to 45 [Degrees] in 6 sec. Instead of round columns, these presses have diagonal key-way or "prism" guidance on the four corners. The upper platen can be allowed to "float" until it engages the mold, and then hydraulically locked in position. This permits lateral alignment to reduce wear on mold shear edges. Another interesting feature is the socalled dwell pressure, which reportedly provides improved surface quality in large parts, without pinholes or sink marks. Using a shear edge mold, the mold is closed the last 8 mils or so only after the shot is injected. (CIRCLE 65)

This dwell-pressure feature is also available on Hennecke's novel horizontal, "tandem" press for fast-acting RIM systems, in which the injection and curing phase is about the same length as the mold opening/demolding/closing phase of the cycle - around 30 sec in each case. The tandem clamp has two molds and two fixed platens, with a moving platen in between. While injection and curing is taking place in one closed mold, the other mold is open for demolding or cleaning. Only one operator or robot is required to service two molds. This approach costs less than buying two separate presses, and is best suited to molding matched pairs of right-hand and left-hand parts. (CIRCLE 66)

Krauss-Maffei's newest polyurea and RRIM systems come with a hydraulic accumulator that alternately supplies the clamp and the piston-metering units. It has been designed to accommodate cure times as short as 20 sec and shot-metering times down to 0.5 sec. At the same time, its connected load has been reduced from 300 kw to 144 kw, a considerable energy saving. High-output polyurea systems are available with capacities up to 500 liters/min for each component. Output rates are closed-loop controlled, with servovalves mounted directly on the metering cylinders to ensure fast cutoff. (CIRCLE 67)

Cannon has also enhanced its relatively new SPC package for RIM control systems (see PT, June '88, p. 35). Now, production monitoring has been integrated into the SPC package, and preventive maintenance software is also provided. The latter counts shots and projects when the next servicing will be required. The full SPC package is available on one version of the new S20 machine and on the Model a system introduced at NPE '88. (CIRCLE 68)

HIGH-PRESSURE POURING NEWS

Both Elastogran Machinery and Hennecke showed off the latest-generation sophisticated mold carriers (see photo) for car-seat production with the "foam-in-cover" or "direct back-foaming" process. In this process, a film/fabric seatcover laminate is vacuum formed into the mold, and foam is poured directly behind it, producing an integral seat in one operation with minimal manual labor. EMB supplied the first 77 mold carriers of this type to various European foam molders, for production of integral seating for the Ford Fiesta in Europe in 1987 and '88. More than 200 of these carriers now have been ordered, and, at Ford's request, EMB has shared the technology with Hennecke and Krauss-Maffei so that they could build the same equipment. Each mold carrier has a plug assist, slip-ring type clamp frame, independently tilting upper and lower mold halves, and its own programmable logic controller to handle the multi-step automatic cycle. Two papers on this technology were presented by Elastogran and Grammer Sitzsysteme at the SPI Polyurethane Div. meeting last Fall in San Francisco.

Hennecke has also come up with its own variant on this technology, called the Teco Foamer system. Hennecke sees additional uses for its Teco Foamer system in making bus seats and office furniture. (CIRCLE 69)

The Teco Foamer system includes a new high-pressure pouring robot with three axes of NC control (five axes optional), which is fast - up to 1.5 m/sec - and compactly designed. All hoses are contained on cable tracks to prevent twisting. The programmable metering system can change index and output rate at the same time, and the mixhead injection nozzles are automatically adjustable to maintain mixing pressure at different output rates (like some of the RIM systems discussed above). A new control system regulates not only the foaming pressure but also the recirculation pressure, via a recirculation throtle, so that both pressures are the same at all times. Also new are stepping motors on the pumps, in place of a-c frequency-controlled motors, which gives a wider range of throughput, from 5:1, vs. 3:1 in the past.

Elastogran has also introduced a new metering unit for high-pressure pouring, which features an a-c variable-speed, frequency-controlled drive. It's said to give very fast and accurate changes in throughput rate, and can be tied into flowmeters for closed-loop control. Also new is a digital pressure readout that can be used for closed-loop control and SPC monitoring. (CIRCLE 70)

A new CRT control is the heart of OMS's new VHP Data high-pressure systems. The 14-in. monochrome screen displays real-time current working data on component temperatures in both tanks and feed lines, tank levels, pouring pressures and times, ratio, shot weight (to 1-g resolution), and output rates for each component. Actual vs. setpoint data for ratio, total shot quantity, and pouring time are also available, as are an alarm page and a page for setting tank levels for auto filling and tank pressures. Up to 100 pouring programs can be stored, including multi-pour programs consisting of eight different pouring sub-programs. The system also displays the number of pours for each head and total consumption of each component. (CIRCLE 71)

A new contribution to the CFC/ozone problem is called Easy-Froth, and is a modification of traditional high-pressure metering/mixing, aimed at producing low-density rigid foams for refrigerators and panels without using CFC-11 or 12. Cannon says it has successfully substituted HCFC-22 (a so-called "soft CFC"), which costs more, but is used in lower quantities because of its lower molecular weight. A positive-displacement metering device was developed and patented to be able to meter this low-boiling material at pressure above 2175 psi, which is necessary to keep it liquid. Two of these devices are connected to the isocyanate and polyol high-pressure lines, immediately before the specially designed injectors of the mixing chamber. With these devices and patented procedures, Cannon says it's possible to obtain HCFC-22 foams with free-rise densities equal to those obtained with CFC-11, and with thermal conductivity similar to foams using only 50% of "hard" CFC's. (CIRCLE 72)

Elastogran Machinery has developed two new systems for hard-to-handle alternatives to "hard" CFC's. One is for metering and blending HCFC-22; the other is for feeding n-pentane into integral-skin foam systems. The latter requires an explosion-proof pumping system and metering directly to the head. (CIRCLE 73)

LOW-PRESSURE FOAM SYSTEMS

In addition, Cannon introduced about a year ago the Model b, its first to provide closed-loop electronic control for low-pressure metering. Simple pushbutton operation with d-c drives and magnetically driven pumps is said to be unique. More than 74 of these systems have been sold in Europe. Flexible foamers reportedly like its ability to store eight pouring programs with different ratios and hardnesses; this allows them to mold eight different cushions at the push of a button. And rigid foamers report up to 7% materials savings, thanks to a more efficiently designed mixhead whose special premix chamber reportedly eliminates preflow. The company also claims energy savings, because the system automatically reverts to low-throughput recirculation mode at the end of a shot, avoiding build-up of excess heat in the chemicals and reducing power consumption. (CIRCLE 74)

More sophisticated controls is the essential feature of OMS's new 2002 series of low-pressure metering units. Expanding on the digital electronic control and diagnostic features of the OMS 2001 series, the new ones provide programmable closed-loop control of individual component outputs. Now it is possible to store 12 pouring programs that specify pouring time and individual output rates for isocyanate and polyol; or one can simply program pouring time, component ratio, and total output rate. Each component pump has its own variable-speed motor, but closed-loop control is based on monitoring the pump shaft speed, not drive-motor speed. Also new is a schematic process display with LED's for parameter values shown at relevant locations. (CIRCLE 75)

And Edge-Sweets reports that it, too, is now equipping low-pressure foam machines with SPC monitoring and computer controls. (CIRCLE 76)

Cannon has a new "environmentally friendly" technology that can be added to the Model b. It's called Water Wash, and it cleans the mixing chamber with an aqueous detergent solution instead of chlorinated solvents. The Purgaren cleaning agent from Rhein Chemie of W. Germany is said to be nontoxic and biodegradable, so that it can be disposed of without special precautions, and its cost is said to be comparable to that of solvents. A special hardware kit is available on new Model b machines that consists of an electrical heater for the detergent tank, heated connection pipes to the mixhead, valves for controlling flow of the detergent and for flushing air into the mixhead, and electronic control for the washing operation. It's also possible to retrofit this kit on some existing Model C machines. (CIRCLE 77)

Edge-Sweets is also now equipping low-pressure foam machines with modifications to permit flushing with water-based detergents or with Du Pont's biodegradable dibasic ester (DBE) cleaning agent (PT, March '89, p. 13), in place of methylene chloride (CIRCLE 78). And EMB has offered it on its F Series since 1986. (CIRCLE 114)

HOT-CURE COMING BACK?

Although hot-cure molded foams for auto seating were superseded by coldcure HR foams 10 years ago in the U.S. and Europe, they still predominate in Japan and may be poised for a comeback elsewhere, according to Cannon officials. Hot-cure retains several advantages: 1) lower densities for equivalent mechanical properties, making them more economical; 2) lower viscosity, allowing free flow in the mold and permitting thinner cushions to be produced; and 3) lower reactivity, allowing more precise distribution of foam in all areas of the mold.

These advantages have been offset somewhat by limitations in cycle times and capital equipment requirements. According to Cannon, these limitations may be overcome by new formulations developed in Europe and Japan. (For example, Mitsui Toatsu Chemicals of Yokohama discussed a new polyol for hot-cure at last fall's SPI Polyurethane Div. conference.) These are said to reduce hot-cure cycle times from 20-25 min down to around 10 min. With higher productivity, fewer molds are required, permitting use of turntable carrier systems rather than conventional chaindriven carousels. Using turntables, molds can be integrally steam heated and water cooled by on-board heating and cooling systems, eliminating bulky and inefficient ovens and cooling baths. Cannon offers a new mixing head, model FPL 18/5, capable of handling the five or more components required for hot-cure systems, and of splash-free pouring into open molds. (CIRCLE 79)

PHOTO : Hennecke's Teco Foamer is one example of highly automated mold carriers for direct foam-on-fabric molding of car seats - and perhaps also bus seats and office furniture. New foaming robot is at left.

PHOTO : Two of many new products for RRIM and SRIM: (L.) Klockner's PU 2000 RRIM system, with clamps up to 275 tons and outputs to 210 liters/min. (R.) Cannon links two polyol and two isocyanate lance cylinders together for fast filling of large SRIM parts.

PHOTO : Novel horizontal tandem RIM clamp from Hennecke takes two molds at once. One is closed for filling and curing while the other is open for demolding and cleaning.

PHOTO : Bigger is the trend in RIM clamps. Perhaps the biggest is an 1100-ton Krauss-Maffei Orion clamp (a smaller model in the series is shown here), which was sold to a European chemical company.