CalenderingMike Coster James Coffey Carly Snyder

The Machine

Typical Calender Line

Calender Roll ArrangementsL

I

F

Z

Problems with Rollers

Newtonian Model Assumptions Newtonian flow Very small gap-to-radius ratio gap-toLubrication approximation, only velocity components Large bank of melt in feed side Uniform velocity at outlet, no shear stress Compute flow rate per unit width Maximum pressure, shear strain, shear stress Power to drive system Roll separating force Rise in temperature

Advantages

Disadvantages Inaccurate for values less than = -

Newtonian Model vs. Experimental Data

Osswald, Tim A., and Juan P. Hernndez-Ortiz. Polymer Processing - Modeling and Simulation. 1st ed. Cincinnati, OH: Hanser Publishers, 2006.

Roller Schematic

Osswald, Tim A., and Juan P. Hernndez-Ortiz. Polymer Processing - Modeling and Simulation. 1st ed. Cincinnati, OH: Hanser Publishers, 2006.

Newtonian Model Equations Maximum Shear Stress:Speed on roll surface:n = revolutions per second, R = radius of roll

Flow rate per unit width:

Power to drive system:

h = gap height, =velocity component, p= pressure, x = position on x-axis of roll

W = gap width, = dimensionless x-direction

Maximum pressure:h0 = half the gap height

Roll Separating Force:

Maximum Shear Strain:

Rise in Temperature:

= height to roll from half gap height for given x-axis position

Q = heat transfer, Cp = constant pressure heat capacity

Shear Thinning Model Assumptions Lubrication approximation, only velocity components Large bank of melt in feed side

Advantages Correlates very well with experimental values (max pressure) Can compute the pressure gradient, roll separating force, and power required to drive system

Shear Thinning Model vs. Experimental Data

Osswald, Tim A., and Juan P. Hernndez-Ortiz. Polymer Processing - Modeling and Simulation. 1st ed. Cincinnati, OH: Hanser Publishers, 2006.

Shear Thinning ModelModelShear Stress: Equationsm = consistency index, n = power law index

Pressure Gradient:

Power law dimensionless pressure

Roll Separating Force: Power to drive system:Osswald, Tim A., and Juan P. Hernndez-Ortiz. Polymer Processing - Modeling and Simulation. 1st ed. Cincinnati, OH: Hanser Publishers, 2006.

Finite Sheet Thickness Previous had large mass Power law dimensionless of polymer melt fed pressure: A finite polymer sheet of thickness hf is fed R = roll radius, h = half the spacing between the rollers , Mathematical conform P(n) = rolling pressure as a function of power law index n well with experimental data for both Newtonian The position where the sheet being fed enters the system: and shear thinning polymers.0

hf = initial finite sheet thicknessOsswald, Tim A., and Juan P. Hernndez-Ortiz. Polymer Processing - Modeling and Simulation. 1st ed. Cincinnati, OH: Hanser Publishers, 2006.

Calendering Sheet Defects Dimensional Non-uniformities Non Thickness variations in the sheets due to roll bending with large separation forces. Compensated with crowned rolls larger diameter in center than at ends.

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

Mattness Micro-irregularity or loss of surface gloss on the surface not in contact with the Microroll when leaving the calender gap. Onsets at a wall shear stress value of 5x108 Pa.

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

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

Uses Major plastic material is PVC Also produced are:Wall coverings Upholstery fabrics Reservoir linings Agricultural mulching materials Rubber sheet http://www.allproducts.com/machine/shinekon/02.jpg

Rubber Made by a combination of extrusion and calendering roller die process Better quality products than single process

2002 John Wiley & Sons, Inc. M. P. Groover. Fundamentals of Modern Manufacturing 2/e

Coating and Impregnating Fabrics Industrial process used to produce:Car tires Conveyer belts Inflatable rafts Waterproof cloth tents Rain coats 2002 John Wiley & Sons, Inc. M. P. Groover. Fundamentals of Modern Manufacturing 2/e

Limitations Thickness Generate film or sheet with a uniform thickness distribution Precise dimensions of the rolls

Cost Installation requires large capital investment Extruder is fraction of cost of calender Superior for product production due to high quality and volume capabilities

References Osswald, Tim A., and Juan P. Hernndez-Ortiz. Polymer HernndezProcessing - Modeling and Simulation. 1st ed. Cincinnati, OH: Simulation. Hanser Publishers, 2006. Vlachopoulos, J., and E. Mitsoulis. "Fluid Flow and Heat Transfer in Calendering." McMaster University, Department of Chemical Engineering. Engineering. 2002 John Wiley & Sons, Inc. M. P. Groover. Fundamentals of Modern Manufacturing 2/e