Color feeders: now they're smarter & more accurate.

Volumetric and gravimetric feeders and blenders have more sophisticated microprocessor controls that can stay tuned to the process. Higher accuracy at low throughputs suits smaller molding presses and extruders.

What do processors want from a color and additive feeder today? A short list would include competitive pricing, improved accuracy and reliability, ease of use and maintenance, enhanced computer controls, and a supplier attuned to system integration.

These requirements apply both to stand-alone feeding/metering units that discharge directly into the throat of a processing machine and those supplied as parts of an integrated metering/blending system.

Suppliers of colorant feeders have responded to these demands with a number of recent improvements. One trend is toward smaller, lower-throughput systems with more precise, repeatable metering performance. Such units better complement the needs of smaller injection presses (below 100 tons) and extruders, while the need for higher accuracy reflects greater demands placed on processors to upgrade the quality and consistency of their parts.

Another trend involves incorporating more sophisticated microprocessor controls on feeding and metering devices. Through automation, processors seek to make at-the-press coloring operations more machine-driven and repeatable, free of operator deviations. They also want colorant feeding to be electronically coordinated with shot size, cycle time, extrusion rate, and virgin/regrind levels. And they want to take advantage of ancillary benefits of microprocessor control, such as statistical process control (SPC) recordkeeping and instant recall of preprogrammed recipes.

GRAVIMETRIC OR VOLUMETRIC?

Colorant feeders (and blenders) fall into two basic categories: gravimetric and volumetric. Volumetric devices measure colorant volume that passes through an auger or metering disk with holes of known size. Gravimetric types measure and control the weight of additive dispensed over a given time period. Both can be effective solutions, depending on the job requirements.

Volumetric units are a simpler, less expensive choice that many suppliers recommend for metering a single additive directly to the feed throat of a molding or extrusion machine. Gravimetric types are more costly and require more sophisticated computer controls than volumetric units, but are recommended especially when two or more additives are being dispensed--either at the machine throat or in a blending system. (Note that gravimetric systems often incorporate volumetric metering components--disks or augers--to physically dispense materials into a weighing chamber.)

Sources at Conair Franklin and Process Control Corp. say gravimetric systems can better compensate for material and process variations and have the added capability of fully documenting the percentages of materials in a blend by weight. Gravimetric feeding and blending systems come in batch and continuous types. HydReclaim, for one, recommends simpler and lower-cost batch blending for most situations if extrusion-rate control is not required. Continuous gravimetric feeding/blending reportedly provides higher accuracy for applications where additive ratios fall below 1%.

Metering accuracy depends both on how feeder operation is coordinated with the process and on the inherent reliability of the controls and feeding/metering mechanism. Agitation devices can be incorporated into the feeding system to maintain consistent flow of material into the weighing zone, auger, or metering disk. Some equipment builders "slave" the additive feed rate to extruder screw speed or injection cycle time; some tie it to the rate of virgin resin feed with an adjustment factor for colored regrind percentage. Still others have more elaborate controls for programmed dosing of additives based on a combination of the foregoing parameters.

Maintaining dosing accuracy despite vibration of the processing machine on which a feeder is mounted is a primary challenge for any feeder system. A K-Tron spokesman claims the firm's newest Colorblend rotating-disk feeder uses a positive-displacement method that remains unaffected by machine vibrations that can cause inconsistencies with auger-type feeders. (Other users of the metering-disk principle include Comet Automation Systems and Matsui.)

NEW INTRODUCTIONS

The last year has seen numerous feeder and blender introductions, including several at NPE '94 (see accompanying supplier listings). The following are three of the latest entries:

* Motan is developing a new volumetric feeder for up to two additives, known internally as the MB "Mini ECO." A company official says the unit is in the final stages of test marketing and will be unveiled in the near future. It reportedly will be competitively priced and have a new user-friendly controller. Apparently, this device can operate as a stand-alone unit or can be incorporated into a blender system.

* Maguire Products is launching its new WSB-140 gravimetric blender, which can handle four components at up to 150 lb/hr. The unit employs a four-chambered main hopper with individual microprocessor-controlled portals that allow materials to drop into a single weighing chamber. All dispensed materials are individually weighed and electronically recorded, with any deviations compensated for in the following dispensing cycle. The microprocessor controls also automatically compensate for the use of colored regrind. Base price is $7250.

* Acrison Inc.'s new Model GP403-101 is a microprocessor-controlled loss-in-weight gravimetric feeder designed for extrusion. It has throughput rate of 2 to 2000 lb/hr and features a counterbalanced, all-digital weighing mechanism that does not use a load cell and reportedly never requires recalibration. Base price is $12,000.

Suppliers of Additive Feeding Equipment

Brief descriptions of product lines follow. In some cases, feeders are offered only as part of an integrated blender unit.

* AccuRate Inc., Milwaukee: Multifeed 2001 gravimetric metering system has modular hoppers and feed rate of 0.5 to 20,000 lb/hr. Six other models of volumetric feeders have feed rates from 0.5 to 2400 cu ft/hr.

* Acrison Inc., Moonachie, N.J.: New Model GP403-101 loss-in-weight gravimetric feeder for extrusion has feed rates of 2 to 2000 lb/hr. Numerous auger-type volumetric feeder models (available with agitators) meter down to 0.0006 cu ft/hr.

* AEC/Whitlock, Wood Dale, Ill.: Sole North American supplier of Colorfeed line of modular, auger-type volumetric feeders built by Scanmatic of Sweden. Available in five basic models. Also supplies volumetric and gravimetric blenders--both batch-weigh and loss-in-weight types (see PT, Nov. '93, p. 73).

* Andrews Products Inc., Statesville, N.C.: Integrated liquid-color dispensing system includes "Add*Flow" progressive-cavity pumping system and "Add*Too" blender. Machine-mounted blender handles up to 2000 lb/hr. Various drive and control options available.

* Louis P. Batson, Inc., Greenville, S.C.: Colormax Micro Module Feeder for injection, extrusion or blow molding is a volumetric unit providing additive dosing control down to 5 g/hr. Also offers volumetric and gravimetric, floor- and machine-mounted blenders.

* Cincinnati Milacron, U.S. Plastics Machinery Div., Batavia, Ohio: Offers auger-type volumetric pellet feeders through a licensing agreement with Universal Dynamics Inc.

* Comet Automation Systems Inc., Dayton, Ohio: Volumetric "Sure Feed" disk-metering unit mounts directly on feed throat, provides throughput of up to 90 lb/hr. Disk metering is also used in Series 150 (250 lb/hr) and Series 500 (4000 lb/hr) volumetric blenders. WB Series weigh blenders combine volumetric disk metering with batch weighing (PT, Sept. '94, p. 66).

* Conair Franklin, Franklin, Pa.: New control package for at-the-throat volumetric feeders (models 470 for up to 60 lb/hr and 476 for up to 300 lb/hr) has thumb switches and LDC readouts for metering speeds and times. It provides independent settings for regrind and colorant in Conair's dual-metering volumetric proportioning feeder. Other auger feeders include Model BF0 (0.08-29 lb/hr) and BF6 (0.4-300 lb/hr). Several series of batch-weigh and continuous loss-in-weight gravimetric blenders include new AutoWeigh GB140 unit for metering up to four materials at up to 150-200 lb/hr with claimed accuracy of 0.1% (PT, Aug. '94, p. 63).

* Dri-Air Industries Inc., East Windsor, Conn.: Volumetric feeders (0.875- and 1.5-in. screw diam.) are typically integrated into PD-Series dryers. Colorant rate slaved to volumetric feed of virgin resin.

* Ferro Corp., Liquid Coatings and Dispersions Div., Edison, N.J.: Two liquid-color peristaltic pumping/metering units can be combined in the new CC120 SpectraChange system, which is said to permit 2-min color changes on injection machines and extruders. Special grooved barrel feed section is required (PT, May '94, p. 15; Aug. '94, p. 35).

* Hamilton Avtec, Mississauga, Ont.: Colortech series of volumetric feeders includes three models (12-24 mm screw sizes) with different control packages--thumbwheel speed setting, digital keypad, and full computerization that automatically adjusts to changes in operating conditions.

* HydReclaim Corp., Fenton, Mich.: HydraColor 270 gravimetric pellet feeder comes in extrusion or injection molding versions. Unit is self-calibrating, with accuracy of 0.1% of span. Also offers volumetric color feeders, 400RWIMB ratio-weigh batch blending system for injection molding, HydraColor 400HC gravimetric batch blenders, and 470 Ulti-Meter continuous gravimetric blenders with new touchscreen CRT interface (PT, May '94, p. 128).

* K-Tron North America, Pitman, N.J.: Recently introduced new-generation Colorblend volumetric disk feeders, Graviblend-Plus continuous gravimetric weigh blenders for up to eight ingredients, and compact loss-in-weight feeders for tight space requirements (PT, June '94, p. 91; Aug. '94, p. 62). Both Colorblend and Graviblend use synchronous feeding for "mixerless" blending.

* L-R Systems (Lasits-Rohline), New Lenox, Ill.: Offers throat-mounted model CC1 volumetric feeder for up to four additives and WSB Series floor-mounted gravimetric weigh blenders.

* Labotek Inc., Rochester, N.Y.: Mini Master Batcher volumetric feeder is throat-mounted, meters a single colorant. Conti Master volumetric feeder comes in two models with 250- and 2500-lb/hr capacities; both handle two to five ingredients.

* LCI Corp., Charlotte, N.C.: Smart Hopper gravimetric feeder, designed for extrusion, comes in eight models that cover a throughput range of 3 to 12,000 lb/hr.

* Maguire Products Inc., Media, Pa.: Offers several auger feeders for pellets and a special powder feeder. Also several models of what are said to be low-priced gravimetric batch blenders for up to eight components and throughput rates of 300 to 5000 lb/hr. Liquid-color pumps in several models include peristaltic types and a gear pump for higher-throughput extrusion.

* Matsui America Inc., Elk Grove Village, Ill.: Three volumetric feeders (rotary and vibration types for pellets and a mini unit for powders) are designed for integration into the Jet Color (JC) II blender. New JCM blender uses volumetric disk metering (PT, April '94, p. 70).

* Motan Inc., Plainwell, Mich.: MB Series volumetric additive feeders have have "countback" control of 100 pulses per screw revolution. MB Mini single-additive feeder provides accuracy of 3000 pulses per screw revolution. Also offers central and machine-mounted blenders.

* Mould-Tek Industries Inc., Scarborough, Ont.: Throat-mounted volumetric pellet feeders, models AF-1 and AF-2 have different control packages and process 0.5 to 1000 lb/hr. Company also offers GXB and XB gravimetric batch-type blenders.

* Novatec Inc., Baltimore: AF-1 volumetric throat-mounted auger feeder handles 1 to 60 lb/hr. Also offers volumetric and gravimetric blenders (PT, Aug. '94, p. 63).

* Plastore Inc., Hudson, Ohio: Plasticolor volumetric feeders (2.5 oz to 5000 lb/hr) offer options on mixing stations, motors, and controls.

* Premier Pneumatics Inc., Salina, Kan.: ProRate volumetric auger feeders process 0.5 to 3500 lb/hr. ProController calculates dispensing weight from count of auger revolutions, stores up to 150 recipes.

* Process Control Corp., Atlanta: Several models of volumetric and continuous loss-in-weight gravimetric blenders include the new XB Series gravimetric blender, which processes up to 700 lb/hr. It has newly designed weigh hoppers for accurate feeding at down to 0.5 lb/hr or less (PT, Dec. '93, p. 55). Controller stores 400 recipes. No-moving-parts "cascade" mixing directly above machine throat reportedly prevents demixing.

* Tecnetics Industries Inc., St. Paul, Minn.: Tecweigh volumetric auger feeders (with external agitation) come in three models for 6 to 900 cu ft/hr. Can be upgraded to a continuous gravimetric system with a loss-in-weigh controller. New Multi-Weigh Controller handles multiple feeders (PT, Sept. '94, p. 67).

* Thoreson-McCosh Inc., Troy, Mich.: MC Series of volumetric auger feeders for 0.5 to 800 lb/hr include six models with optional microprocessor controls and feed-throat mixers. Can be integrated into Acra Color blender system. New Intelli-Color (Tech II) microprocessor-controlled gravimetric color blender uses vibratory feeders for throughputs to 1000 lb/hr. Compact design permits floor or machine mounting (PT, May '94, p. 129).

* Universal Dynamics Inc., Woodbridge, Va.: Volumetric auger feeders for pellets include compact Mini unit for up to 28 lb/hr and Heavy Duty model for up to 2200 lb/hr. Both mount just above feed throat, below main resin hopper. Mini feeder can be combined with Sav-Air GT Loader to make a quick-change loading/feeding system. All feeders can use Omni IV microprocessor controller for injection molding. Company also offers volumetric and gravimetric blenders. high-capacity WB series weigh blenders handle up to four materials at 1500-4000 lb/hr (PT, March '94, p. 53). "Target" batch weigh blenders include new Micro unit for up to 250 lb/hr and can use new "Echo" distributed control system (PT, May '94, p. 127; Aug. '94, p. 62).

* Vibra Screw Inc., Totowa, N.J.: VersiFeeder MiniFeeder gravimetric unit for extrusion is slaved to extruder screw speed. Output range is 2 to 50 lb/hr. It has microprocessor controls and vibration of hopper, trough, auger, and feed tube.

* Walton/Stout Inc., Lithonia, Ga.: CPF-1 volumetric, at-the-throat auger feeder delivers 65 lb/hr.