Auxiliary equipment is shrinking to catch up with a growing market for small precision parts. Dryers, loaders, blenders, grinders, and chillers have all dropped in size for accuracy and fast product changeovers.
A decade ago, processors doing small-parts injection molding or extrusion of thin medical tubing or multi-layer products would have been hard pressed to find auxiliary equipment sized small enough for their needs.
Standard-size blenders, dryers, loaders, chillers, and granulators were too large for emerging applications in medical, electronic, automotive, and communications markets. Examples included cellular-phone flaps, hand-held organizers, toys, and compact discs. This disparity has become even more glaring with the recent growth in "micro-molding" of parts weighing less than a gram. Applications include watch gears, mini optical lenses, and tiny electrical parts. In one example, two wiring bobbins plus the runner weigh a total of less than 1 g. The parts are so small that dimensional checks must be performed under a microscope. These parts are being molded in only one- or two-cavity tools. "Some customers have requirements of one-tenth of a pound of material per hour, with accuracy of ±0.25% at 2 sigma [two standard deviations divided by the mean]," says Don Dunnington of K-Tron America.
Conventional auxiliary equipment moves hundreds of pounds and hour in injection applications and thousands of pounds an hour for extrusion. Such equipment sits rather uncomfortably atop molding presses of under 100 tons that process less than 120 lb/hr, or extruders with up to 2-in. screws running 700 lb/hr or less.
"We discovered that molders producing smaller parts had almost no alternative to a lot of manual operations. When drying small lots for instance, standard practice was to manually place a quantity of resin on a drying tray, bake it in an oven, then manually remove and transfer it to the machine hopper," says Chuck Morgan, Conair product manager for conveying products. Many times, handling smaller volumes of material involved a guy with a shovel, says Tom Rajkovich, president of Comet Automation. Moving small material volumes, either through manual handling or with larger auxiliary units, often resulted in an inaccurate measurement that could be costly if expensive resins or additives were being used.
Although most of the demand for small auxiliaries is to accompany small injection machines, extrusion also accounts for a share. The growth in extrusion of tiny medical catheters is one factor. Another is the need to equip small coextruders on multi-layer lines--e.g., barrier layers in packaging and cap layers on sheet and profiles. "There are more coextrusion film applications on the market, and with that comes multiple extruder setups to produce the films. Plant floor space has become scarce, which has created demand for smaller equipment to fit in," says Joe Robertson, president of Process Control Corp.
Auxiliary-equipment suppliers have responded in recent years with a proliferation of pint-size units-- both physically smaller and able to provide lower throughputs with high accuracy. The new diminutive equipment is principally dryers, blenders, loaders, and receivers. Some of the newer offerings include zero-desiccant dryers, 15-g loaders, 0.1-g/cycle additive feeders, and low-rate granulators, blenders, chillers, and mold-temperature controllers.
"Auxiliary units being made today are at least one-third to 50% smaller in size and throughput than the smallest made five to seven years ago--and there may be more shrinking to be done," says Comet's Rajkovich. A majority of equipment suppliers surveyed confirm that they have downsized existing technology for modest throughput rates while keeping a full menu of features. For example, the controls on continuous gravimetric blenders from Process Control have been shrunk to one-eighth the previous size yet provide the same power and features, says Robertson.
"Five years ago, we didn't make a chiller smaller than 1.5 tons," says Jon Gunderson, marketing/sales manager for Advantage Engineering. Now the company offers models down to 0.25 ton.
"Even the granulators have to get smaller because the sprues and runners are," says Jim Hoffman, regional sales manager for Rapid Granulator. Rapid has added a second facility in Charleston, S.C., to build small units like its SR series granulator, sized down to a 6 x 6 in. cutting chamber.
The use of smaller auxiliary equipment frees up more space on the shop floor. In the case of central systems, auxiliaries at the processing machine may be stripped down to only a tiny just-in-time loader or additive feeder at the throat of the press or extruder, notes Lou Zavala, v.p. product marketing and engineering at AEC Inc.
Portability of small units is another option that can speed set-up and changeover times. "With smaller units, one can wheel away one dryer and wheel in another that has the next resin already dried and ready to go, so there's no need to wait," says Richard Hamilton, president of Hamilton Avtec.
While some hardware suppliers may have gotten started early, the trend to downsizing auxiliaries has picked up steam and has by now enlisted the majority of vendors. It is not possible here to catalog every small unit on the market, but we attempt to cite representative examples of this trend, with emphasis on developments in approximately the last two years.
Small batch-type and continuous gravimetric blenders are proliferating, with capacities down to micro scale. Maguire Products, the market leader in batch blenders, came out relatively recently with the Micro-Pulse vertical valve, which is said to meter as few as one or two pellets at a time. Here are some other recent or upcoming developments:
Even the smallest dryers today (60 lb/hr and lower) offer dual desiccant beds, drying temperature up to 350 F, -40 F dewpoint, microprocessor controls, and no moving parts. Here's a sampling of the latest developments:
A number of recent entries use vacuum or compressed air to move handfuls of material from a central or press-side container to the machine throat:
The new Graviblend S low-rate additive blender from Colortronic provides continuous loss-in-weight feeding at rates down to 0.1 g/cycle or 0.25 lb/hr using its digital disk technology. The firm also developed the Colorblend S additive feeder to dose virgin and masterbatch at throughputs less than 33 lb/hr. It works on a venturi principle.
Comet Automation's new model PF-1200 feeds non-free-flowing powders at rates down to 5 lb/hr. It is said to be accurate to ±0.5%. The compact unit extends just 20 in. from the centerline of the feed throat. And for pellets, Comet's model 1000-SM reportedly can run at 0.5 g/cycle with 0.5% accuracy. Comet eliminated the pulsing of an auger screw by substituting a helix coil, which continuously drives a column of material.
The new BAF Series volumetric disk feeder from Conair adds small quantities of minor ingredients to the primary material just before it enters the feed throat. Designed specifically for small molding machines and extruders, the BAF feeder meters down to a fraction of a gram/sec.
Motan's new three-model ECO line of additive feeders uses an inclined auger to feed 0.22 to 44 lb/hr.
Highly efficient scroll compressors have been adopted by a number of chiller makers as a means of squeezing the equipment into a smaller package. Recent examples include the PSA line of chillers from AEC/ Application Engineering, which have a 25% smaller footprint than previous models. Iceman portable chillers of 3-10 hp from Mokon also have scroll compressors, as does a recent 5-ton model from Kleen-Rite.
Scroll compressors are also used on some models of the space-saving Sterlco Vision line from Sterling Inc. These portable units come in 0.5 to 3 hp and occupy a maximum of 20 x 31 in. Here are some other recent developments:
Small-size scrap is more efficiently handled by smaller granulators. For example, AEC/Nelmor came out with the 3-5 hp Talon 6 x 8 in. granulator for small injection presses.
Ball & Jewell's smallest model is the new Vision BPV68 6 x 8 in. model with 2-5 hp.
The new six-model GR series press-side granulator from Comet provides sprues and runner processing at rates from 17 to 132 lb/hr. The 1-7 hp units have two stator blades and six to 24 rotor blades.
The new M80 granulator from Colortronic can fit beside the press or under the press due to its low profile. It operates at 100 rpm for less dust generation. The two-bed knife unit uses a new blade geometry that imparts no thermal stress on small sprues and runners. It grinds less than 5 lb/hr.
Cumberland Engineering's new 700 series beside-the-press models come as small as 7 x 9 in. The company also introduced a 6 x 8 in. RR (reverse rotor) model that can reverse the direction of rotation to utilize the opposite knife edges when one side becomes dull.
Smaller sprues and runners can be downsized at rates up to 100 lb/hr in the new 5-hp 10 x 8 in. press-side grinder from Foremost Machine Builders. The unit comes with a very small screen size to handle the small sprues. The top-feed unit has a footprint of 22 by 22 in. and stands more upright than traditional designs. It is a two-bladed unit with an angled-cut rotor. Foremost also redesigned its HD series grinder with an offset motor for compactness.
A small model designed for robotic feeding is the Robo 810 from Granutec. It can switch from 200 to 400 rpm and grinds 30-150 lb/hr.
Super-compactness, low horsepower, and low cost are hallmarks of the unusual R-9 "Radial" granulator introduced last year by Maguire Products. The two-knife rotor is mounted at a 45¡ angle in a vertical cabinet with a footprint of only 16 in. square. It has a 6 x 7.5 in. opening and 3-5 hp drive, but grinds more than 400 lb/hr.