SEMINAR SEMINAR ONON

CALENDERINGCALENDERING

PRESENTED BYPRESENTED BY

MARIA IMMANUEL RICHARD LMARIA IMMANUEL RICHARD L

II ND SEM M.Tech TOOL ENGINEERINGII ND SEM M.Tech TOOL ENGINEERING

R V COLLEGE OF ENGINEERINGR V COLLEGE OF ENGINEERING

CalenderingCalendering In the calendering process melted In the calendering process melted

plastic is passed through heated rolls to plastic is passed through heated rolls to form a sheet, and continues down a form a sheet, and continues down a series of rollers with gaps of decreasing series of rollers with gaps of decreasing size until the required thickness is size until the required thickness is achieved. Afterwards the film is cooled achieved. Afterwards the film is cooled on a chill roller. on a chill roller.

The equipment for calendering cost The equipment for calendering cost more than the equipment for extrusion. more than the equipment for extrusion. However, the process involves far less However, the process involves far less cleaning than the extruder, which must cleaning than the extruder, which must be flushed and cleaned post use. be flushed and cleaned post use.

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The MachineThe Machine

Typical Calender LineTypical Calender Line

Calender Roll ArrangementsCalender Roll Arrangements

I

L

F

Z

Calendering Sheet DefectsCalendering Sheet Defects

Dimensional Non-uniformitiesDimensional Non-uniformities Thickness variations in the sheets due to roll bending with large separation forces. Thickness variations in the sheets due to roll bending with large separation forces.

Compensated with crowned rolls – larger diameter in center than at ends.Compensated with crowned rolls – larger diameter in center than at ends. Structural AnomaliesStructural Anomalies

Particulate and crystalline structure changes under the influence of high temperature Particulate and crystalline structure changes under the influence of high temperature and stressand stress

MattnessMattness Micro-irregularity or loss of surface gloss on the surface not in contact with the roll Micro-irregularity or loss of surface gloss on the surface not in contact with the roll

when leaving the calender gap. Onsets at a wall shear stress value of 5x10when leaving the calender gap. Onsets at a wall shear stress value of 5x1088 Pa. Pa. V-shapesV-shapes

Surface thickness variations with vertex of v-shape at center of sheet. Due to Surface thickness variations with vertex of v-shape at center of sheet. Due to undulating motions in the melt bank from the center to edges.undulating motions in the melt bank from the center to edges.

Air BubblesAir Bubbles Captured in the melt bank. Can be prevented from passing through the calender rolls Captured in the melt bank. Can be prevented from passing through the calender rolls

through high pressure.through high pressure.

UsesUses

Major plastic material is PVCMajor plastic material is PVC Also produced are:Also produced are:

Wall coveringsWall coverings Upholstery fabricsUpholstery fabrics Reservoir liningsReservoir linings Agricultural mulching Agricultural mulching

materialsmaterials Rubber sheetRubber sheet

RubberRubber

Made by a combination of extrusion and Made by a combination of extrusion and calenderingcalendering ““roller die process”roller die process” Better quality products than single processBetter quality products than single process

Coating and Impregnating FabricsCoating and Impregnating Fabrics

Industrial process Industrial process used to produce:used to produce: Car tiresCar tires Conveyer beltsConveyer belts Inflatable raftsInflatable rafts Waterproof cloth Waterproof cloth

tentstents Rain coatsRain coats

LimitationsLimitations

ThicknessThickness Generate film or sheet with a uniform thickness Generate film or sheet with a uniform thickness

distributiondistribution Precise dimensions of the rollsPrecise dimensions of the rolls

CostCost Installation requires large capital investmentInstallation requires large capital investment Extruder is fraction of cost of calenderExtruder is fraction of cost of calender Superior for product production due to high Superior for product production due to high

quality and volume capabilitiesquality and volume capabilities