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Auxiliary equipment.

Auxiliary Equipment

Auxiliary equipment is now an inseparable part of the plastics industry's move towards greater precision, quality, productivity, and cost-effectiveness. Today's processing requirements demand that the auxiliary equipment be strong, reliable links in the overall production system.

In the traditional, and dominant, approach, auxiliary equipment functions largely independently. A second approach reflects the growing emphasis on system integration, and is often implemented through single-source turnkey projects. Large, new installations, and manufacturers with dedicated product programs, are increasingly utilizing the more interdependent system method.

In turnkey installations, a supplier typically assumes the responsibility of selecting auxiliary equipment and interfacing it with the primary machine. With the trend of manufacturers to "farm out" their engineering and implementation requirements, suppliers of discrete units also are being asked to provide higher levels of technical know-how and service.

INCREASING PRESSURES

B. Patrick Smith, vice president, marketing, The Conair Group, which designs, manufactures, and installs a complete range of auxiliary equipment and integrated systems, believes that in the future, "producing a single line of auxiliary equipment may not be sufficient to meet the new demands." In the past, he says, a granulator supplier could profit with a single comprehensive line, but to keep business in the future, the pressure will increase for him to take over more of the developmental and installation problems of the processing system.

At least, Smith asserts, "that is the wisdom that is becoming apparent in the field. The new challenge will be for an auxiliary equipment supplier to be able to provide, or to at least oversee, the selection and networking of diverse auxiliary equipment components that are fully integrated with the primary processing machinery.

"The requirements of many custom plastics processors are changing. Having a range of machines capable of molding a variety of plastic products may, in many instances, not be enough. One growing direction is for more dedicated, in-house processing for manufacturers of individual products."

Smith cites a manufacturer of thermal window panes who no longer arranges with an outside plastics processor to produce window extrusions. Those extrusions are now made in-house by a system coordinated by a single-source supplier who is capable of making plastics processing an integral part of the manufacturer's business.

Smith believes that the expected growth of systems-based installations of auxiliary equipment is bound to make a significant impact on the marketers of individual components.

This strong opinion is counterbalanced by suppliers of discrete auxiliary equipment components. While conceding the validity of the turnkey direction as a significant market development, they nevertheless contend that their traditional market base is more solid than ever, and that their strength will continue to grow.

INCREASING TURNKEY RATE

The multidirectional development of the auxiliary equipment industry is very apparent. Berstorff Corp., for one, says that its business reflects major changes in controls that interlink a complete system through one control panel. "We find that major companies have been cutting back on their engineering staffs and are looking to suppliers to perform many of the tasks that were previously done in-house," says Gene Stroupe, product manager, compounding equipment. "The companies are coming to us to do complete turnkey projects. We are now doing this with about 2 out of 10 extruders that we install. We expect this rate to probably increase to about half the lines within 10 years."

Berstorff's twin-screw extruders now range between 25 and 300 mm, but the typical turnkey installations have been in the 60- to 90-mm area. Stroupe observes that larger companies now are also looking for more multipurpose processing lines with greater flexibility in their systems. The objective is to accommodate the multiple products being processed by convenient incorporation of several types of feeders, various downstream addition capabilities, and perhaps two or three types of pelletizer systems.

MUCH STRICTER CONTROL

Alex Mora, Formula Plastics Inc., a custom injection molder, has 16 machines ranging from 40 to 300 tons, with shot sizes from 1 to 20 oz. He documents the greater demands for closer-tolerance controls on auxiliary equipment.

"When considering the purchase of auxiliary equipment," Mora says, "we ask to try it for 30 days, with an option to return. We are stricter now because we cannot afford to improperly process and lose the more expensive engineering materials. Materials such as the polyesters or polycarbonates, for example, often cannot be reground because, once hydrolysis occurs, they undergo a chemical change and degradation. The temperatures must be kept stable, and alarms are essential when the dew points are not precise.

"Microprocessor controls on our dryers, chillers, and mold temperature controllers assure us that the temperature of drying the plastic, and the dew point, are correct, and that filters are clean and hopper levels are being properly maintained."

Mora indicates that these components currently are monitored independently of the machine's computer processing unit, but that in the future, he intends to be able to monitor the auxiliary equipment from the machine computer's CRT in an interconnected system.

EQUAL STATUS

It is apparent that within the last few years, auxiliary equipment has been moving into a position of equal status with the primary molding machine. The high precision expected from the molding machine and the molded part cannot be achieved if the auxiliary equipment is not in step with overall process requirements. Malfunctioning of a chiller, for example, and the resulting mold temperature changes could produce short shots, skin imperfections, and reduced dimensional stability of the parts.

Until about 1985, it was typical for auxiliary equipment, such as loaders, blenders, dryers, and chillers, to operate almost exclusively with their own independent controls. The integration of microprocessor controls then facilitated communication networks that enhanced the capabilities of auxiliary equipment to parallel those of the primary machine, and permitted more centralized regulation of the molding cycle.

Machine recipes then could be downloaded to a work center for setting up the auxiliary equipment to the proper cycle parameters, thus substantially taking the human element out of the processing loop. It also became possible to receive alarms at the central computer station as soon as any element of the process, or the auxiliary equipment, started to malfunction.

The instantaneous responses of the alarms represented significant cost savings in labor and materials, because they prevented stretching out the production of defective parts. Since the alarm messages also were diagnostic, troubleshooting times also were significantly compressed.

The capability of system integration, with microprocessor controls, was a major leap forward. It responded to the need to bring auxiliary equipment to control parity with the sophistication of the molding machine. Recognizing the emergence and the benefits of the systems approach, some plastics machinery manufacturers introduced their own lines of auxiliary equipment, which could be networked directly to the molding machine.

As Denes Hunkar, president, Hunkar Laboratories, points out, "Now, a new job could be treated at a work center, where all the machine and auxiliary equipment setups could be inputted. The advantage is that every aspect of the process that could have an effect on the part is controlled by the integrated network."

One limitation that still existed, however, was that there was no commonality between the many different equipment brands, making the networking difficult, if not impossible. But some machinery manufacturers with dedicated programs to provide interconnected turnkey systems, using their own auxiliary equipment or that made for them under a private label, were able to bypass the typical networking limitations.

COMMUNICATIONS PROTOCOL

The Machinery Component Manufacturers Division and the Machinery Manufacturers Division of The Society of the Plastics Industry (SPI), reacting to the lack of interfacing commonality between the different brands of auxiliary equipment, embarked on an effort to develop a language, or protocol, so that dissimilar products would have a necessary degree of compatibility for convenient linking in a processing network. Through software built into each auxiliary unit, and an RS 232 or RS 485 serial communication port, the varied commercial elements will be able to "talk the same language" in a networked arrangement, with the processing machine as the centerpiece of the system. Available to SPI members for $2500 and to nonmembers for $5000, the protocol, however, is designed only for communication between a machine and its auxiliary equipment, and not between machine and machine, or between a machine and a host computer.

There is also growing interest in connecting processing machines and their associated auxiliary equipment components to a supervisory central computer in an automated plant, and thereby increasing the potential for computer-integrated manufacturing (CIM). Post-processing functions, such as painting, plating, or assembly, can also be included in the control network.

As Hunkar says, the state of the art now encompasses a capability of integrated control of every equipment component in the molding process that affects the quality of the final product. Still, the absence of a standardized protocol for intermachine networks currently limits the implementation of higher integration levels with multiple machines to the existing proprietary technologies. Nevertheless, Hunkar maintains that in the last 10 years, company missions have advanced from impoving the productivity of a single machine to enhancing the productivity of an entire plant.

Hunkar Laboratories provides total system connections from sensors to a plant's host computers. The company's CIM-1 program, for example, incorporates all processing and auxiliary equipment, and all post-molding processes, into a master network connected to a plant's supervisory computer. The computer automatically searches process variables and provides a warning when a deviation occurs.

Hunkar says that users confirm that the warning, initiated 20 to 25 minutes before a bad part is made, is achieved with programs that evaluate process trends and predict when a parameter will change sufficiently to cause a problem. The company's Expert Analyzer, for example, searches the database of the central computer for deviating parameters. If it finds one, it predicts when the deviation will cause the production of bad parts and issues the alert. If the problem is machine-related, a manual adjustment is then made.

"Can zero-defect processing be far behind?" Hunkar says, reiterating that incorporating microprocessors in auxiliary equipment has been a critical step forward in providing much more accurate performance than ever before.

A KEY INFLUENCE

Mark C. Stencel, director of marketing, AEC Inc., another leading system-oriented supplier of auxiliary equipment, sees the linking of the computer to plastics processing as one of the key influences on the future development of auxiliary equipment. AEC's product line from its four divisions includes process water equipment, such as chillers and cooling towers; temperature control units; water recirculating equipment; resin handling, bulk storage, and drying and blending systems; plastic scrap recovery and granulation equipment; and automatic conveying and robotic products.

Reclamation and recovery of waste or scrap plastic material, Stencel says, offers an increasing opportunity for the auxiliary equipment manufacturer. "Farsighted suppliers of granulation and scrap-recovery equipment are looking beyond the 'beside-the-press' needs and expanding their product offerings to provide solutions to the global waste problem, before it chokes off the industry's positive developments," he says. "The trend in beside-the-press granulators is to develop two-stage units with rotary shear devices for granulation of large parts, and to shorten the distance between the granulator and the robot by consolidating the package."

Microprocessor control of centralized vacuum loading/conveying systems as well as of drying and blending, and chiller and temperature control systems, are now offered as stand-alone units or networked systems. In an AEC design, a tangential, rather than the conventional 90-degree, inlet to hopper loaders ensures gentler materials handling, and use of electronic sensors, rather than electromechanical timers, on the hopper loader avoids underfilling or overfilling.

Stencel adds that the increasingly global economy has spurred some auxiliary equipment suppliers to review their product offerings in the light of growing requirements for "world-class" lines. In this context, AEC, in addition to integrating microprocessor-based control systems, is focusing on a company-wide effort on basic product improvements. "A rework of each of AEC's core products is under way," Stencel says, "aiming at the introduction of 10 new product lines from the four divisions in 1989. Much of this 'newness' derives from the use of computer-aided design techniques aimed at simplification of the manufacturing process, thus increasing product reliability."

But Stencel emphasizes that much of the improvement is also achieved through the application of advances in component design. "While this may lack the glamor of advances in control technology," he holds, "a lack of attention to a market demand for reliable, state-of-the-art mechanical design could spell doom for those emphasizing only control, at the expense of overall product quality. The requirements of the 1990s will force this balanced view."

MULTIFACETED

COORDINATION

Cincinnati Milacron entered the auxiliary equipment business four years ago with an emphasis on the turnkey approach. The company's Specialty Equipment Business Unit coordinates auxiliary equipment with primary processing machines, computer-integrated control systems, machine sizing and selection, plant layout, and other facets of plant operation.

Unit manager Robert Kadykowski says that the total package of machinery and service can include sizing of injection molding machines by computer program; listing auxiliary equipment requirements as another function of the sizing software; and charting the flow of incoming materials, subassemblies, inventory levels, production requirements, and personnel needs. Computer control and communications systems can tie auxiliary equipment to processing machines and link with host computers for implementation of management information systems, computer-integrated manufacturing, and statistical process quality control. Kadykowski says the turnkey approach has been especially successful for customers building new facilities where machine layout and overall plant design capabilities are required.

"Flexible manufacturing and dedicated manufacturing cells and plants, designed, supplied, and running, are the result of a focus on development of a particular plastics process, rather than simply supplying the traditional hardware," Kadykowski adds. "A key to success is a capability of communicating with the injection machine controls to make process conditions easy to set. This has been one of the driving forces for the standardization of communications between machine and auxiliaries, as now represented by the new SPI protocol."

MORE MICROPROCESSORS

With the auxiliary equipment industry now past the first and second generation of controls, including electromechanical and discrete electronic devices, it is now building in more microprocessor-regulated features than ever before. Ronald T. Bankos, sales manager, Universal Dynamics Corp. (Una-Dyn), comments that, for example, dryers now incorporate built-in energy monitors, and electronic temperature sensors provide precision system readouts. Color feeders have adaptive conrols that sense shot times and correct auger speeds to match the process, and almost all controls have digital readouts of set points and actual process limits. Customers are demanding and getting networked systems that download set points to monitor operations and initiate alarms in event of deviations.

Bankos adds that equipment appearance, together with increased functional accuracy and safety, is being increasingly considered. He says that because of an overseas influence on style, some auxiliary equipment manufacturers are making more use of castings instead of fabrications and are designing improved sheet metal housings to encase internal components.

Greater functional capabilities and accuracoes are being obtained from the expanded use of microprocessor controls on volumetric- and gravimetric-controlled feeding and blending devices. The applications are diverse, but the pattern is consistent. Una-Dyn, for example, has developed a system to provide quick material changes from up to 1k sources to 15 destinations, through totally automated vacuum conveying that requires no manual switching or hose changing. The heart of the system is a microprocessor-controlled valve that automatically indexes to select the proper source and destination.

Worker safety, says Bankos, also is "rightfully a major concern in the industry." Una-Dyn has responded to this concern in a number of ways, with dryers that utilize heat shields on desiccant beds; dryer hoppers that are insulated; and afterheaters that are hopper-mounted to reduce runs of "hot" ducts. All of the equipment has increased safety labeling to warn of potential hazards.

WEIGH FEEDING AND

BLENDING

Innovations in feeding and blending have improved performance, increased reliability, and provided more options for the processor. Broader and more effective materials handling capabilities are helping to control the flow of "difficult" materials such as tiO.sub.2., carbon black, talc and others, ranging from varied fillers to fiberglass, powdered pigments, slip agents, and stabilizers.

New, high-resolution weighing systems sense material weight in digital format and are specially designed for performance in the process environment. And, although microprocessor-based control is to be expected nowadays, the power of the chip is being used in new ways to optimize performance as well as to make operation easier and data more available. More sophisticated feeder and blender controls now can regulate even the most extensive systems, either on their own or through a host computer.

Complex or critically demanding applications will clearly benefit most from these and other advancements. However, just as a rising tide lifts all boats, even the typical processor with less demanding requirements is likely to gain from the advancements in feeding and blending technology.

The most visible recent trend in feeding and blending, whether for the compounder or molder, has been a progressive shift from volumetric to gravimetric control. Prime factors fueling the transition to gravimetric feeders include the increasing use of more expensive and exotic additives, tighter blend tolerances for improved quality, and the ever-present need to reduce scrap/recycle requirements, as well as to minimize overfeeding critical ingredients.

Don Melchiorre, national sales manager, K-Tron Corp., producers of weigh-belt, loss-in-weight, and volmetric feeders, says, "In the early 1970s, we recognized the need for an additive feeder with broader materials handling capabilities than the helical-type auger feeders then in common use. The conventional auger feeders were satisfactory for materials that flowed smoothly and did not clump, stick, or flood through the auger. For materials that exhibited those difficulties, however, we developed the twin-screw feeder, in which a matched pair of intermeshing, co-rotating, closed-flight screws prevent flooding in aerated materials, and with its self-cleaning design, the feeder avoids clumping and sticking in hard-to-flow materials. The twin-screw feeding concept was further exploited by means of a family of screw geometries to handle nearly any material gravimetrically or volmetrically, whether powder, paste, pellet, or granule."

While many in-house, captive, or custom compounding operations require the higher feed rates provided by dedicated feeders, where each feeder is tailored to handle a specific material, growing requirements for on-line gravimetric blending in processing operations demand specialized, multi-ingredient blending systems. Bruce Lowden, national sales manager for K-Tron Vertech's Graviblend continuous weigh blender, a new entry in the burgeoning weigh blender market, says that "the advent of highly critical processes such as multilayer film coextrusion imposes new, more stringent blender performance requirements. Volumetric blending cannot attain the accuracies needed in these high-tech processes, and as a result, processors are looking to weigh blending for the needed performance. Our weighing and control technologies are addressing the challenges of continuous on-line blending and extruder throughput regulation."

A durable, accurate weighing system is central to any gravimetric feeder or blender. K-Tron's Digital Force Transducer, using a vibrating load cell, senses the resonant frequency of a small wire placed under tension by the process load. Electronically driven to maintain resonance regardless of its value, the wire's frequency rises and falls with the applied load, similar to a guitar string sounding a higher note when the string is tightened and a lower note when the tension is reduced. Load is then sensed directly in digital format simply by measuring the wire's resonant frequency. A resolution of one part in a million is reported, and the transducer is claimed to be insensitive to the performance-eroding effects of vibration and ambient temperature variations.

AN INCREASING ROLE

John Angliss, sales manager, Schenck Weighing Systems, sees the specialty equipment suppliers having an increasing role as the plastics industry focuses on quality and dependability. Schenck's range of continuous weighing and feeding equipment includes conveyor belt scales, momentum flow meters, Coriolis mass flow meters, weighbelt feeders, loss-in-weight feed systems, and supervising controls with graphics.

Schenck's recently introduced totally enclosed mass flow meter, operating on the Coriolis principle, meets demands for measurement accuracy by applying the science of particle acceleration and its resultant forces to continuous weighing and control of bulk solids. The material, fed vertically and centrally to the flow meter, falls on centrifugal wheel whose rotating guide vanes divert the flow radially outward in a horizontal direction. The materials is deflected by the inner surface area of the casing to the centrally located discharge outlet. As a result of the Coriolis forces occuring as the particles move along the guide vanes, the acceleration of the bulk solids by the centrifugal wheel generates a measurable torque that is directly proportional to the mass flow. A microprocessor-controlled measuring system then amplifies the torque signal and computes the mas flow.

Angliss finds that more customization of process systems and ingredients are making materials handling capabilities an increasing important consideration in choosing proportioning and feed systems. "As a result," he maintains, "components designed for easily handled materials, such as pellets, and for generalized applications often cannot meet the requirements presently being specified. Twenty years ago, volumetric feed systems were typically employed for controlling the flow of materials, and today the majority of units are still of volumetric design. However, the gravimetrically controlled feed systems are now the preferred norm for increasing applications. In additions, sophisticated microprocessor-controlled systems with recipe storage and compatible communication interfaces are important in the overall product packages."

MULTIPLE MIXING

The continual emergence of new and more advanced raw materials often requires multiple mixers for processing medium-to high-viscosity formulations. A high-speed disperser often wets-out and disperses the solids into a liquid vehicle, followed by a low-RPM, high-torque mixer that blends the product as the solids loading and viscosity increase.

A high-speed sawtooth blade usually is used for solids dispersion. Because the blade is situated in one fixed location in the mixing zone, thi design is dependent on the flow characteristics of the materials. The efficiency of the mixer therefore decreased as the viscosity of the mix increases over 50,000 cps. Furthermore, localized heat buildup is not uncommon with this design, since the blade rotates at high speed in one specific spot in the mix vessel.

In mixing applications involving high-viscosity formulations, a well-proven double planetary, low-speed, high-torque mixer, with two paddle blades that revolve on a common axis, is frequently used. Simultaneously, each blade rotates on its own axis, with the blade advancing along the vessel wall with every revolution on its own axis. The double planetary motion helps ensure the homogeneity of the mix within a few minutes.

Bogard Lagman, vice president, sales, Charles Ross & Son Co., manufacturers of special mixers, has developed a design that combines the high-speed disperser and double planetary mixer concepts. The PowerMix Planetary Dispenser utilizes a sawtooth blade rotating at high speed, while a rectangular paddle blade rotates at low speed, thereby continuously feeding material toward the disperser blade. Simultaneously, the disperser and the paddle blades both revolve on a common central axis. the epicyclic movement ensures complete coverage of the mix zone, independent of the flow characteristics of the materials. Combining high-speed dispersion and low-speed blending into one unit eliminates transfer steps from one mixer to another and, in addition, as the disperser blade moves through the batch material, minimizes localized heat buildup.

WIDER CAPACITY RANGE

John W. Doub, marketing manager, Novatec Inc., says that while he sees a trend toward single sourced systems, 95% to 98% of the company's sales are direct to the users as independent components. He says the major markets now are for smaller at-the-machine dryers, mostly equipped with microprocessors, for industries such as the electronic and medical, and for large central drying stations for molding large parts, for industries such as automotive. From drying capabilities ranging from 50 to 2000 lbs/hr about 10 years ago, the technology now has advanced to cover 2 or 3 lbs/hr at the low end, up to over 4000 lbs/hr. In addition, there is a greater demand for quick-change capability to accommodate frequent product variations with minimum downtime. Doub says that today's more precise units are also more energy-efficient, with their on/off time cycles being electronically controlled for switching to alternate desiccant beds on demand, rather than by preset mechanical timers.

For materials handling, Robert Barlow, material handling manager, Novatec Inc., cites the still predominant use of vacuum conveying systems, to a maximum of about 15 inches of mercury, and use of solid state and programmable controls. Pressure systems up to about 15 psi now provide higher material-movement capacities.

MANY TECHNICAL

ADVANCES

The auxiliary equipment segment of the plastics industry obviously has incorporated many technological advances. Among the gains are increased dedication to precision temperature control, within [plus-or-minus] 1[deg.]; more computer interfacing; and ruggedized design of heat transfer equipment. In resin drying, energy-saving options now include use of alternative energy sources such as natural gas and RF energy.

Silo designs permit quicker construction and more flexible operation, even with materials having difficult flow characteristics. Enhanced control systems provide inventory reports and more sophisticated networking of raw material supplies with end-use machines, such as blending/drying stations. More readily calibrated, high-precision coloring and blending, and inventory reporting are now achieved with computer-controlled gravimetric models.

Vacuum loading systems now allow for a choice of control formats, some with computerized capability. Loading units are being redesigned to handle wider varieties of materials or are quickly adaptable to different applications. System designs include features that minimize maintenance.

New materials and new scrap forms necessitate developments in throat and cutting chamber configurations. Scrap granulation developments include improved blade and rotor designs. Noise abatement and reductions in energy consumption are targets of other ongoing research efforts.

For compounding, new die-face models eliminate the need for water baths and highly monitored operations. Increased control of downstream components of pipe, tubing, and profile extrusion systems facilitates greater precision of end products. Much higher throughputs on critical jobs, such as medical tubing, are due to the precise, highly engineered nature of today's modern auxiliary equipment. Just-in-time manufacturing technology also has forced some bold new control formats that allow sophisticated changes to take place in production, while materials are still on-line.

Robotics design is now more dedicated in the plastics industry, with specific robotic packages specifically developed for quick installation and application. Control systems allow previously dedicated, single-application robots to be easily programmed for other uses.

As the economics of plastic reclamation change, opportunities emerge for new machinery and systems. Recycling of scrap has formed the foundation of the reclaim system technology, but one of the big issues is the development of new product designs that incorporate scrap materials.

NO STRONG SHIFT

Thomas A. Benson, vice president of sale and marketing, Thermal Care/Mayer, leading manufacturers of heat transfer equipment, does not now see a major trend to eliminate the small molder, or a strong shift in the industry where customers are looking for a single source of supply to meet their auxiliary equipment requirements.

"This is most often seen in large plant expansions," he maintains, "where the desire is to give the project to one individual and not have to be concerned about any of the details. In any case, more often than not, if the customer does have this interest, he will ask the molding machine manufacturer to be the sole source, rather than an auxiliary equipment supplier.

"In our case, the cooling tower, pumping systems, and chiller all interface and are piped together, so there is value in having a single supplier to provide that equipment, including engineering drawings. However, there is no interconnection of the heat transfer equipment with materials handling, granulation, or robotic equipment. From Thermal Care/Mayer's standpoint, currently we find that reliability, quality, and workmanship are most important to a customer."

Benson concedes, however, there will be significantly increased customer interest in direct communication between the primary and auxiliary equipment, especially with the availability of the SPI communications protocol.

TEMPERATURE

PRECISION

Liquid circulating temperature control units, which typically have been used in plastics processing for many years with mechanical and electromechanical controls, have also been the beneficiary of improved electronics, which provide much faster response times and more precise regulation. Scott T. Dieckelman, sales manager, Industrial Control Div., Sterling, Inc., says that the use of more accurate sensing devices in temperature controllers, including dual sensors, are important developments that enhance equipment reliability.

To conserve energy, many manufacturers now use three-phase motors and three-phase heater elements for minimum power consumption for a given wattage output. Another current advantage is the ability of programmable controllers in the temperature control equipment to interface with the machine process controller for improved regulation of temperature and alarm settings.

Sterling offers a range of water-circulating temperature control units for operation to 250[deg.]F, and high-temperature equipment for operation up to 550[deg.]F, with solid state or microprocessor-based controllers.

MORE EFFICIENT

GRANULATORS

The increased molding of both small and large plastic parts has also expanded the market for granulators that can efficiently handle highly filled materials requiring different cutting actions and blade alloys that resist abrasion. Robert Ragosta, product manager, Beside-the-Press Granulators, Cumberland Engineering Div., John Brown Plastics Machinery, says that closed loop systems can now bring the granulate back to the feed hopper of the machine. Heat buildup, evacuation of material from the granulator, or a stall condition can be monitored with microprocessors. Larger rotors and greater screen areas increase throughput.

Ragosta points out that any granulator now can have microprocessor control as an option, although captive operations that consistently process the same parts, and which represent a small percentage of the total market, typically tend to utilize it.

Quieter running granulators are achieved by increasing the number of blades on the rotors, which allows lower rotor speeds for the same outputs. Current noise levels of 80 to 85 dB compare with the 90 to 95 dB that were common 10 years ago. The noise reduction was largely accomplished by rotor geometry modifications and the use of damping materials such as absorbing foams and dense composites.

FLEXIBLE

COMMUNICATIONS

Buhl Automatic confirms that molders are increasingly requesting the ability to regulate manufacturing cells from a central plant or supervisory computer. The challenge often confronting today's control manufacturer is to provide the integrated network that can link the variety of communications protocols to one central point, as well as to provide direct control of older equipment. Buhl's development of its PPC 2020 cell control package provides a tightly coupled integrated network system that the company says puts the complete control capability on a single platform.

The PPC 2020 supports RS232/422/485 communications with intelligent auxiliary equipment, and can communicate concurrently with a number of devices using different protocols. Set points can be downloaded to the device, and actual values for quality monitoring, statistical analysis, and data logging can be read. The control can be programmed to regulate less communicative auxiliary equipment directly, thus replacing the current controls with the unit's intelligence, and allowing the device to be set up from a central point. Monitoring, analysis, and data logging capabilities are extended to the previously more limited equipment. Buhl says that any combination of intelligent communications and direct control can be implemented.

The programmable communications capability provides flexibility for interfacing with any plant or supervisory computer via a dedicated communications port. All set points for a given job can be stored locally in battery-backed memory or on a floppy disc, or they can be uploaded to a central computer. The complete machine and auxiliary equipment setup can then be automatically downloaded the next time the job is run.

For production and quality monitoring, all actual and calculated values can be requested by the central computer. Process and production data can then be sent to a plant computer for management reporting and quality analysis.

HEARING THE DRUMBEAT

Auxiliary equipment obviously must march to the drumbeat of each particular plastics process. Whether it is sufficient that the equipment function independently, as it now often does, playing its part in the overall production cycle, or whether it becomes part of an integrated networked system will be determined by the emerging specifications for each project. The important fact is that auxiliary equipment technology, both existing and evolving, both stand-alone and integrated, is now very responsive to plastic industry needs and can be expected to continue to be alert to emerging processing requirements.
COPYRIGHT 1989 Society of Plastics Engineers, Inc.
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Title Annotation:plastics industry equipment
Publication:Plastics Engineering
Date:Jul 1, 1989
Words:5382
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