Schenck Accurate - Powder and Bulk Engineering Magazine

Volumetricfeeders helpcreatechocolateysatisfactionA confectioner installs sixvolumetric feeders in a newmake-your-own candy barproduction line to accuratelydispense small ingredientamounts into chocolate basebars.New installationIn June 2010, The Hershey Company,Hershey, Pa., opened a newinteractive attraction at its HER-SHEY’S CHOCOLATEWORLD attraction.Called HERSHEY’S CreateYour Own Candy Bar, this hands-onattraction gives visitors the ability tocreate a customized candy bar with upto three inclusions, operate authenticfactory equipment, and design individualizedpackaging for the candybar.To make a candy bar, a visitor usesa touchscreen to select the ingredientsand starts the production process bypulling a lever.A food-grade belt conveyorthen moves a HERSHEY’Smilk chocolate base bar under a seriesof feeders that fill the selected ingredientsintothebasebar’srecessedcavity.After the filled base bar movesthrough an enrobing and coolingprocess that seals in the ingredients,it’s transferred to the attraction’s packagingarea, where the visitor selects acustom overwrap sleeve for the completedproduct. The candy bar is thenplaced in a carton that’s put into a souvenirtin, and the selected overwrapsleeve is placed around the tin, whichis given to the visitor at the end of theprocess. When designing this attraction,the company needed to ensure aperfectly made candy bar for everyvisitor, so it selected volumetric feedersto consistently fill the various ingredientsinto the base bars.Selecting the feedersEach base bar is about 133 millimeterslongby67millimeterswide,anditsrecessedcavity is about 5 millimetersdeep and has a volume of approximately38 cubic centimeters. Since thecompany planned to allow visitors tochoose up to three ingredients, thefeeders in the attraction’s productionline had to be able to accurately dispenseeachchoseningredienttofillapproximatelyone-third of the cavity’svolumewithoutoverfillingit.Tomaintainefficiency, the fill time for each ingredienthadtobelessthan5seconds.“We needed feeders that could reliablyfeed small batch sizes in shorttime intervals and handle a wideCopyright, CSC Publishing, Powder and Bulk EngineeringThe volumetric feeders are installed side-by-side in a straight line, and abelt conveyor moves the chocolate base bars from right to left, firstunder two screw feeders and then under four vibratory feeders.

ange of ingredients with disparateparticle sizes and flow characteristics,”says Krista Cessna, Hershey associatestaff engineer. “For thisproject, we found that gravimetricfeeding wasn’t an option because ofthe small ingredient amounts andshort fill times. So we contacted severalvolumetric feeder suppliers, andone of them wanted to conduct tests attheir test center, so I sent them a varietyof ingredients for testing.”This supplier, SchenckAccuRate, operatesa full-service test center at itsfacility inWhitewater,Wis., and manufacturesand supplies volumetric andgravimetric feeders, vibratory feeders,weighfeeders, controls, customsystems, and other bulk solids handlingequipment to the food, chemical,pharmaceutical, plastics, andother industries.The supplier conducted multiple teststo determine the ideal equipment andpreliminary operating parameters forthe ingredients and sent the resultsback to the company. “I then took thebase bars to their test center, and weset up a belt conveyor and watched thefeeders fill the ingredients into thebase bar cavities,” says Cessna. “Thisallowed us to see that the various ingredientshave different trajectorieswhen they discharge from a feederand that they bounce differently whenthey hit the base bar, causing some ofthem to spill out. We found that thedischarge height is critical to not havingthe pieces bounce out, so we adjustedthe feeder’s height andhorizontal position for each ingredient,enabling each one to hit the targetmore accurately. We also determinedthe feeder run time and feedrate foreach ingredient.”After successfully completing thetests, the company placed a purchaseorder in Fall 2009 for two volumetricscrew feeders and four volumetric vi-“We needed feeders that couldreliably feed small batch sizes inshort time intervals and handle awide range of ingredients withdisparate particle sizes and flowcharacteristics.”Copyright, CSC Publishing, Powder and Bulk EngineeringA vibratory feeder accurately dispenses an ingredient into a chocolatebase bar’s recessed cavity.

atory feeders. Cessna says, “We selectedthese feeders not only becauseof their ability to precisely handlesmall batch sizes in short times, butalso because of their ability to feed anumber of ingredients with differentdensities and particle sizes.”The volumetric feedersThe two MECHATRON low-rangeConi-Flex dual-drive screw feedershave a maximum throughput of 21ft 3 /h and are used to dispense ingredientswith particle sizes larger than 5millimeters, such as rainbow jimmiesand rice crisps. Each feeder has a 1-cubic-foot-capacity hopper extension,a 0.75-inch-diameter helix withan end stub, and a 1.375-inchdiameternozzle with bottom discharge.The feeder has twovariable-frequency-drive, washdowndutymotors — one drives the helixand the other powers external agitationpaddles that massage the feeder’sFDA-approved flexible hopper topromote material flow to the helix.“Because of the ingredients’ largeparticle sizes, we had to oversize thefeeder’s nozzle to allow the ingredientsto move freely through it duringoperation,” says Tom Symoniak,Schenck AccuRate senior applicationsengineer. “A tight tolerance betweenthe helix and nozzle wallwould’ve stopped material flow anddegraded the ingredients. And sincewe used an undersize helix in an oversizenozzle, we put an end stub on thehelix and a triclamp fitting with endbushing on the bottom discharge nozzleto support and center the helix, ensuringthat it maintains positionduring operation and doesn’t ride upor down. Additionally, for cleanoutease, the triclamp fitting can be disassembledwithout tools, and a customcleanout insert installed in the hopperbottom allows it to be completelyemptied by just running the helix.”The four MECHATRON LS lowrangeConi-Steel Vibro vibratoryfeeders have a maximum feedrate of28 ft 3 /h and are used to dispense ingredientssuch as graham crackercookie pieces, white chocolate chips,chocolate cookie bits, and other freeflowingingredients that can be easilydamaged. The feeder has a 1-cubicfoot-capacityhopper extension and a70-millimeter-wide feed tray that canbe adjusted for height to accommodateingredients with different particlesizes. An electromagneticphase-angle vibratory drive with a 4-to-20-milliamp input vibrates the feedtray and controls the feedrate.A feedbacksensor on the tray monitors thetray amplitude and sends a signalback to the drive to maintain the designatedfeedrate.All six feeders are constructed offood-grade Type 304 stainlesssteel, and each feeder is mountedon a structural steel stand.All six feeders are constructed offood-grade Type 304 stainless steel,and each feeder is mounted on a structuralsteel stand. “A low-level indicatormounted on the side of eachhopper signals the production line’scontrol system to alert an operatorwhen a hopper needs to be refilled,”says Symoniak. “And a removablegrate magnet on each hopper’s top ensuresfood safety and allows easy accessto the hopper’s interior forcleaning.Additionally, since the interiorof each feeder can be accessedfrom the nonprocess side, the feederdoesn’t have to be removed from theproduction line for cleaning.”Feeding the ingredientsThe company installed the feedersside-by-side in a straight line so thatthe servo-driven indexing belt conveyorruns directly below eachfeeder’s discharge. A clear plasticguard between the belt conveyor andthe attraction’s visitor area allows visitorsto see the ingredients beingadded to their candy bar.During operation, a base bar is movedup to and parked at a photo eye that’sinstalled on the conveyor’s side andcentered under the feeder’s discharge.The photo eye signals the control systemthat the bar is in position andready to be filled with the selected ingredient.The conveyor then movesthe bar past the photo eye while thefeeder dispenses the ingredient intothe bar’s cavity, which takes less than5 seconds. After the bar moves pastthe photo eye, the conveyor stops for abrief moment before moving it to thenext feeder. If the next feeder’s ingredientis one that’s not been selected,the conveyor moves the bar just aspreviously detailed, but the feederdoesn’t dispense anything.“We place a ribbon of an ingredient inthe bar’s bottom, then another ribbon,and finally another ribbon on top ofthat to provide an even displacementof the ingredients,” says Cessna. “Wekeep the larger particles in the upstreamfeeders and the smaller particlesin the downstream feeders,because the smaller particles fill downinto the cavity and around the largerparticles, which helps minimize thebar’s profile.”Since opening the HERSHEY’SCreate Your Own Candy Barattraction, reactions from visitorshave been favorable and thecompany expects the attraction tobe one of its most popularexperiences.Creating a unique, positiveexperienceSince opening the HERSHEY’S CreateYour Own Candy Bar attraction,reactions from visitors have been favorableand the company expects theattraction to be one of its most popularexperiences. “The visitors are happybecause they get to be a part of the productionprocess and see authenticplant equipment making their veryown candy bar,” says Cessna. “We’repleased with the feeders’ability to hitthe target without spillage.Visitors areCopyright, CSC Publishing, Powder and Bulk Engineering