Paper Calendering Techniques Quiz

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Questions and Answers

What is the primary advantage of on-machine calendering over off-machine calendering?

It is more cost-effective and utilizes current technology. (correct)

It is faster than off-machine calendering.

It produces thicker paper more efficiently.

It requires less energy to operate.

How many sets of rolls can high-grade finishing involve during the calendering process?

Up to 5 sets of rolls.

Only one set of rolls.

Only two sets of rolls.

Up to 3 sets of rolls. (correct)

What distinguishes the soft-nip machine calender from the hard-nip machine calender?

The soft-nip calender has a soft roll layer made of elastic material. (correct)

The soft-nip calender uses hard metal rolls.

The soft-nip calender creates thicker paper.

The soft-nip calender is less commonly used.

Which factor influences the calendering level required for a specific type of paper?

The finishing grade desired. Signup and view all the answers

What is one of the methods used to heat the rolls in an intermediate rolls stack during calendering?

An inlet of hot water. Signup and view all the answers

What is a major advantage of soft-nip calendering?

It produces a uniform size distribution of pores. Signup and view all the answers

Which statement is true about supercalenders?

They include both hard and soft rolls for better paper smoothness. Signup and view all the answers

What is a drawback of using soft rolls in supercalenders?

They require frequent roll changes. Signup and view all the answers

How does blackening affect the printing quality of paper?

It leads to uneven absorption of ink. Signup and view all the answers

What process takes place after drying and calendering paper?

Reeling the paper onto a metal cylinder. Signup and view all the answers

What is the primary function of the driving drum in the reeling process?

It controls the speed of the reeling process. Signup and view all the answers

During the reeling process, what happens as pressure is applied by the secondary arms?

The paper on the drum is wrapped onto the reel spool. Signup and view all the answers

What is the most common defect encountered during the reeling process?

Wrinkles and breaks due to air pockets. Signup and view all the answers

What role do the secondary arms play after the desired diameter of the paper reel is reached?

They reduce pressure and slow down the reeling process. Signup and view all the answers

What is the typical diameter range for a reel spool used in the reeling process?

20 – 100 cm Signup and view all the answers

What is the primary objective of the calendering process in papermaking?

To reduce thickness and obtain a smooth surface Signup and view all the answers

Which part of the calender stack consists of heated rolls and variable-crown rolls?

Intermediate rolls Signup and view all the answers

What does the calendering section control in addition to smoothing the watermark on paper?

Paper density Signup and view all the answers

What is true about the time taken for pressing in the calendering process?

It is very short to maintain production speed. Signup and view all the answers

Which rolls are usually considered the driven rolls in the calender stack?

Queen rolls Signup and view all the answers

Study Notes

IWK 203/4: Stock Preparation and Papermaking

Course code: IWK 203/4
Course title: Stock Preparation and Papermaking
Also known as: Penyediaan Stok & Pembuatan Kertas (Malay)
Instructor: Dr. Kushairi Mohd Salle
Institution: Universiti Sains Malaysia
Academic year: 2024/2025

Papermaking Sections

Introduction to Papermaking (2.1)
Approach Flow System (2.2)
Forming Section (2.3)
Pressing Section (2.4)
Drying Section (2.5)
Calendering, Reeling, and Finishing Sections (2.6)

Calendering, Reeling, and Finishing Sections (2.6)

Calendering:
- After drying, most paper grades pass through calendering.
- Calendering uses rolls to press the paper under high pressure.
- The calender stack consists of horizontal rolls (steel or cast iron) stacked vertically.
- The objectives of calendering are to reduce paper thickness and create a smooth surface.
- Calendering is also used to control paper density and smooth watermarks.
- Rolls may not have equal hardness. Nip pressing time is shorter.
- Calendering level depends on desired finishing grade.
- Low-grade paper requires only one or two nips. High-grade paper may pass through several sets (7-9 rolls per set).
Rolls:
- Intermediate rolls (upper stack): Heated rolls and variable-crown rolls.
- Queen rolls: Usually driven rolls.
- King rolls (bottom): Act as variable rolls.
Types of Calenders (and types of rolls):
- On-machine calenders are more economic.
- High temperature calendering allows for lower pressure. Frequently first two rolls are heated by hot water.
- Tri-pass drilled rolls are most efficient. Shell rolls are efficient. Bored rolls are least efficient.
- Machine calenders use a hard-nip system (pair of hard metal rolls) to produce uniform thickness.
Reeling:
- Post-drying and calendering, paper is collected on a metal cylinder (reel spool).
- Reeling gathers paper from the paper machine and forms a loop (full reel).
- On-machine reeling happens after calendering. Off-machine reeling happens before calendering.
- Key components: driving drum/reel drum, reel spool, primary arm, secondary arm.
Reeling process details:
- Driver drum is the most important component as it controls the speed.
- Reel spool is initially positioned in the primary arms, then the secondary arms apply pressure for wrapping.
- Reeling stops upon reaching the desired diameter (full reel).
- Reeling is stopped, the paper is broken, and the full reel is moved to the end of the rail.
Winding:
- Post-reeling, the paper travels through a winding stage.
- Purpose: Cut and wind the full reel into smaller, usable rolls.
Size press: Size press distributes sizing agents (like starch) on paper, improving water and air permeability to strengthen the paper.
Pigment coatings:
- Improve the sheet's surface for printing by mixing fillers and binders with the paper.
Modern Paper Machine Finishing:
Now finishing is done on machine.
Paper Coating Principles:
- Blade coating, Size press, Film coating, Curtain coating, Spray coating.
Blade coating produces smooth but uneven coatings. Curtain coating produces even but rough coatings.

Additional Information

Typical reeling defect: wrinkles and breaks due to air pockets, especially in dense/low porosity paper.
Winding process trims both edges of the paper. Broke is recycled. The middle is cut depending on the width.
Paper rolls are marked with details like grammage, thickness, and width.
Paper rolls are sent for further treatment to produce additional paper products.

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Description

Test your knowledge on paper calendering techniques, including the differences between on-machine and off-machine calendering, and the types of machines used in the process. Explore advantages and disadvantages of various calendering methods, and understand the impact on printing quality. This quiz is perfect for those studying paper manufacturing.