Common Calendering Defects

Gauge Variation
Incorrect crowning of rolls
Excessive wearing of bearings
Improper operation of roll bending/zero clearance devices.

Stock Blisters
Roll temperature too high
High feed bank
Stock warm up for long time

Holes in the sheet
Insufficient break down of the compound
Inadequate temperature control
Insufficient compound in the bank

Lumpy
Roll temperature too high
Large nip opening
Stock warm up for long time
High Compound in the nip



Crushed Fabric
Insufficient nip opening between rolls
Excess compound in the nip
Improper roll crown
High compound viscosity

Loose coating
Improper Roll temperature
Improper running speed
Low compound viscosity
Improper warming of the compound


Crows Feet (improper flow behaviour)
High viscosity compound
Improper warm up, high bank
Non uniformity of warm up
Lower roll temperature

Calender grain (Directional strength)
Lower temperature in one of the rolls
High friction ratio
High calendering speed
Use of anisotropic fillers



ACCEPTABLECRITERIA FOR THE INPUT MATERIAL-FABRIC

Dipped fabric tested in lab for the following parameters:

Breaking strength.
Part load elongation.
Elongation at break.
Dip pick up %.
H-adhesion.
Stiffness.

Only Lab released okay dipped fabric to be used.
Damaged free packing.
Dipped fabric width should be within the specified limit.


Compound tested in lab for the following parameters:

Rapid rheoproperties.
Specific gravity.
Mooney viscosity.
Mooney scorch.

Only Lab released okay Compound to be used.
Compound should be identified with tag and crayon mark.