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The new Emhart Glass Plunger Pro-cess Control (PPC) provides for thefirst time a complete visualization ofthe parison forming for narrow neckpress and blow as well as wide mouthpress and blow. The system recordscontinuously the entire plunger strokeon all cavities across the machine inreal time, as the plunger actually trav-els through the glass whilst formingthe parison.

PPC also provides a precise gobweight control through automaticfeeder tube height adjustment andoptional needle height adjustment.The wireless connection from baseplate adapter to plunger mechanismwith full stroke sensor eliminates therisk of cable damages during a mecha-nism exchange. The Emhart GlassPPC system permits early detectionof currently unknown variations inthe NNPB and PB process, offeringthe potential to improve productionquality. Especially finish defects canbe detected and rejected by using theinnovative software features and theautomatic Hot End Ware Reject(HEWR).

Precise Plunger PositionDetection

The full stroke sensor integrated intothe Emhart Glass Quick ChangePlunger Mechanism is the signalsource of the system. The ceramic

sensor tube carries at the inside acopper surface, which represents ca-pacitor electrodes, influenced by ametal tube mounted inside the pistonrod and surrounding the ceramic tube.A coil is connected inside the lowerflange of the ceramic tube. Coil andcapacitor in connection with theadapter plate create an electrical os-cillator circuit. The capacity changesrelative to the position of the pistonwhich leads to a change in the reso-nance frequency of the oscillator cir-cuit. The adapter plate is mounted onthe plunger base plate and suppliesthe oscillator circuit of the sensor withenergy wirelessly. The position sig-nal is modulated onto the energy sup-ply and transferred with one cable percavity from the adapter plate to themaster unit. This is a very stablemethod of position measurement andsignal transition which makes PPCvery reliable.

Christian Fröba, Emhart Glass SA, Cham, CH

Optimization of Container Productionwith Plunger Process ControlThe glass container industry today is facing high demands of product quality.Frequently glass container manufactures are confronted with quality issues indifferent areas, those applying narrow neck press and blow (NNPB) as well aswide mouth press and blow (PB) process are often experiencing finish defects.These defects often have there origin in parison forming process. The industrycurrently has limited means of controlling this vital process.

Piston and Rod with Full StrokeSensor. Photo: Emhart Glass

Full Stroke Visualizationand Production Tracking

The acquired signal is then, in realtime, processed and analyzed in PPCMaster creating valuable informationabout the parison forming process.Several screens at the Master are dis-playing this information and makingthem a quick and easy reachable sourcefor process improvements.The Status History screen virtualizesthe selected plunger stroke.

�: The Master splits the entire strokeautomatically into seven signifi-cant parts of the motion. The colorcoding of these intervals is con-sistent with other screens and al-lows the operator easy under-standing of the process.

�: All important process parametersare displayed numerically andgraphically and recorded everystroke with the production time.Limits of this values can be setwhich activates the Hot End WareReject (HEWR) in case of viola-tion of these limits. This allowsrejecting defective containers al-ready at the hot end. As these dataare available immediately the op-erator can react quickly withoutwaiting until the defect might bedetected at the cold end. This savesvaluable time and helps increasethe overall efficiency of the pro-duction line.

�: In the upper part of the screen theentire production recording is dis-played. Abnormal production likeviolations of process parameterlimits are marked with colors.

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differences in cooling and press forceas well as any changes at startup of asection.

In the light red “area” interval repre-senting the final press duration a smallblack point is drawn. This visualizesthe time, when the highest press posi-tion has been reached. This is a goodindication of process stability as themore of these black points build up ahorizontal line, the more stable is theplunger end position. The more theblack points deviate, the more un-stable plunger final press position iswhich shows variations during theparison forming process.

The effect of parameter adjustmentscan be seen immediately as this screengives a very good overview about thecurrent production condition on allsections as well as any drifts which

The Status History screen virtualizes the selected plunger stroke.gray: reverse position – white: motion into loading position – blue: stop inloading position – dark red: fast upward to press – yellow: transition into finalpress – light red: final press – green: fast downward to reserve position

Photo: Emhart Glass

Easy navigation and recall of thestored process parameters andstroke visualizations is possiblewithin the entire production time.A transfer of all the data to astandard PC is possible for per-manent storage of the informa-tion. This allows a productiontracking, which was not possiblein the past.

The connection to the plant wide in-formation system, transferring weigh-ing and HEWR information is closingthe loop to integrated quality control.

Visualizing ProcessVariations

The Press and Loading Duration His-tory screen shows the previously colorcode stroke visualization scalded bytime. Each line represents one plungerstroke. This kind of visualization en-ables to determine long and short termdeviations in the press duration be-havior of the process, for exampleduring swabbing, changing the molds,

The Press and Loading Duration History screen.– detail– finish defects Photo: Emhart Glass

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may only appear on one section. Withexperience, this information will al-low conclusion about the machineadjustments and function/malfunc-tions of the machine, lubrication sys-tem and associated equipment likefeeder and shear.

Precise Gob WeightControl an EssentialFactor for NNPB andPB Production

Stable gob weight is one of the keyfactors for successful NNPB as wellas PB production. Equal gob weightcut by cut without variations reducesthe risk of producing critical defectsright from the beginning. Customersexperience shows that the PPC gobweight control works very stable us-ing advanced control algorithms toadjust the tube height in NNPB aswell as PB process. For higher preci-sion demands the needle height canalso be controlled individually. PPCmanages to keep the gob weight veryconstant even with unstable upstreamproduction processes like variationsof temperatures in furnace and fore-hearth.

�: In the upper part of the Weight &Controller History screen theweight of each gob is visualizedas a dot.

�: In the lower part of the screen thecontroller history is recordedshowing all adjustments made bythe tube height control loop orone of the two needle height con-trol loops at this TG installation.While PPC is taking care of thegob weight, the machine operatorcan concentrate on keeping theproduction and quality at a highlevel. All of this increases theacceptance of advanced technol-ogy in the glass plants.

In order to meet the quality demandsof the packaging industry today and

Weight and Controller History screen. Photo: Emhart Glass

in future, process control and automa-tion will be a major factor. EmhartGlass offers with PPC a valuable toolfor NNPB and PB production optimi-zation. Using PPC means producinggood quality at the hot end instead ofselecting for good quality at the coldend.

Further information:Emhart Glass SA,Hinterbergstrasse 22, PO Box 5361,CH-6330 Cham, Switzerland,www.emhartglass.comThe author Christian Fröba is actively asa Product Manager Plunger Systems atEmhart Glass AG.

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