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Based on: Industry Standards and Best Practices

Languages: English

Sample Transcript

The use of different furnishes in different layers gives the paper or boardmaker greater flexibility. Multi-ply forming is often used to produce paper or board grades with the required performance characteristics using lower cost fibers in the middle of the sheet. As an example, for printing and writing grades, shorter fibers and fillers that enhance surface properties and printability of the sheet can be used in the outer layers, and longer fibers can be used in the middle to give the sheet the necessary strength characteristics. If a cheap source of long fiber can be found, this can lower production costs. Additionally, expensive high-performance fillers like titanium dioxide can be concentrated on the outside surfaces of the sheet.

Multi-ply Forming

Training Time: 20 minutes

Multi-ply forming was first introduced in 1830 when two cylinder formers were combined to produce a two-ply sheet. Equipment designs have changed over the years, however, the multiple cylinder former design is still in use. Multi-ply sheets can contain a different stock mixture in each layer, which has several potential benefits, including those related to fiber costs, machine speeds, and sheet properties. Therefore, multi-ply forming has expanded from mostly paperboard grades to tissue and other paper grades.

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The use of different furnishes in different layers gives the paper or board maker greater flexibility

The use of different furnishes in different layers gives the paper or board maker greater flexibility

"Dry vat" and "half vat" cylinder formers restrict the exposure of the wire to the stock, which shortens the forming zone

"Dry vat" and "half vat" cylinder formers restrict the exposure of the wire to the stock, which shortens the forming zone

An ultra former consists of a felt-wrapped cylinder mold with a headbox; it can be used to add an additional layer on top of an existing sheet

An ultra former consists of a felt-wrapped cylinder mold with a headbox; it can be used to add an additional layer on top of an existing sheet

Learning Objectives

  • Describe the history of multi-ply forming
  • List the goals of multi-ply forming
  • Describe the three basic methods of multi-ply forming
  • Describe the design and operation of cylinder formers
  • Identify and describe the different types of equipment used to produce multi-ply sheets
  • Identify the challenges of multi-ply forming
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Multi-ply Forming FAQs

How can multi-ply forming reduce costs?
For high basis weight grades; multi-ply forming can run at higher speeds than are possible with single-ply forming. Also, more economical furnish components can be used in some layers, and expensive components can be concentrated in the layers where they can make the most impact.

What are three basic ways that a multi-ply sheet can be formed?
A multi-ply sheet can be formed by forming additional layers on top of an existing sheet, separately forming multiple layers and then combining them together while they are still moist, or using a multi-layer headbox

What are some of the downsides of multi-ply forming?
Additional equipment must typically be installed and operated to prepare and deliver different furnishes to the different layers. Also, bonding between the plies or layers can be a problem.

What kinds of products are made using multi-ply forming?
Multi-ply forming was originally used to produce heavy weight grades, but it is now used to produce a wide range of products, including tissue and towel, and printing and writing, grades.

How can cylinder formers be used to produce a multi-ply sheet?
A cylinder former forms a sheet on its mesh-covered surface and then transfers it to an absorbent felt that is pressed against it. When multiple cylinder formers are arranged in series with a single felt, each additional former adds another layer to the sheet that is forming on the felt.

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