MAYURBHANJ SCHOOL OF ENGINEERING, BARIPADA

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Branch : Mechanical Engineering�Semester : 6th

Subject : Advance Manufacturing Process

Topic : CALENDERING

Faculty : Er. R PATTANAK

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CALENDERING PROCESS

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CALENDERING PROCESS�

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BASIC PRINCIPLE

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• Calendaring is the process of squeezing a plastic melt between two or more counter rotating cylinders or rolls to form a continuous film and sheet.
• The art of forming a plastic sheet has been adopted from the technique of making paper, metal and rubber in industries

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Introduction

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• Both rigid and plasticized compounds of PVC resin can be used in calendaring process.
• The sheet is formed in the range of 0.1 to 1.0 mm and above thickness. The sheet can be transparent, colored, embossed, printed or laminated form.

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Plastic material and its Compound

• The PVC resin is generally processed in calendaring plant, and it needs blending, mixing and compounding by addition of suitable chemicals called as additives and fillers to make compound before processing in the calendering plant.
• Other then PVC resin ABS, PE, PP and Styrene are also used for calendering process.

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Coloring materials and fillers �

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• The pigments or dyes which can withstand temperatures of processing at about 180°C should be considered. Pigments which are suitable for coloring plastic materials are metallic salts, lead, Cadmium based and also organic colors are used.

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Coloring materials and fillers

• Inorganic materials in the form of fine powder can be added in the Plastic compound which helps to reduce cost and improve properties. The popular fillers are china clay (a hydrated aluminum silicate) and the various grades of chalks (Calcium Carbonates). Also red mud (hydrated aluminum silicate) is also used as fillers. The fillers improve the modulus and the low temperature crack resistance is reduced

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Compound preparation (Blending & Fluxing)

• The resin is premixed and blended with stabilizers and other additives by using Ribbon blender or High speed mixture. The premixing is done up to 80°C for better absorption and soaking of the resin.
• After blending of the two compounds, it is fed to a fluxing machine. Fluxing is done under temperature at about 150°C.
• Fluxing can be done in banbury mixture or a continuous extruder
• The residence time of the plastic flux at high temperature must be limited.

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Sectional diagram of ribbon blender

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Calendering process with plant details

• The rolls are heated either by steam or hot oil and roll temperature ranges from 150° to 180°C.
• Fluxed material delivered to the first calendar nip is regulated to form a rolling bank. The sheet passing the first nip forms another bank between the second and third rolls, at the final nip, the desired thickness is obtained from the smallest bank possible to minimize stress in the sheet.

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- Type

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Calender rolls and its Heating arrangement

• Calendar rolls are normally made of chilled cast iron. Calendars are also made with steel rolls which are more resistant and which exhibits less deflection under the pressure of the material in the nip.
• Heating system
• High pressure steam is used on calendaring plants. Working pressure range – 680-1380 KN/m and a temperature range 120-185°C.

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Typical drilled calendar roll

• High pressure hot water (H.P.H.W.),This is effective method to heat and cool the calender rolls by circulating H.P.W.H. through each roll.
• The hot oil can be circulated through the rolls to achieve the high operating temperature.

Processing Parameters

The processing parameter needs to be set and control are temperature, speed, pressure and the nip gap.

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Applications

• The applications include sheets in hospitals, Printer blankets, rain coats, table cloths, draperies, water tank liners, wall covers, thermoform sheets, packaging applications, medical applications, stationery items, files, folders, luggage bag applications, counter tops, flooring, upholstery, automobiles applications, and Toys.
• They may be heat-sealed, heat shrunk for blister packaging or used plain as wrapping materials, mulches, swimming pool liners, reservoir films, vapor barriers.

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THANK �YOU

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