Slitting may seem like a simple process of cutting a wide roll into narrower rolls, but it's not always that easy in actual production. Material tension, blade setup, knife positioning, and rewinding control can all affect the finished rolls.

When these factors aren't properly controlled, manufacturers may encounter issues such as rough edges, dust, wrinkles, misalignment, or unstable finished rolls.

In this article, we'll explain what slitting is, how slitting machines work, the common types of slitting methods, and how knife positioning systems help improve cutting quality and efficiency.

What Is Slitting?

Slitting is the process of slitting a wide roll of material into narrower widths for downstream manufacturing, packaging, printing, and other converting applications.

It's widely used for roll materials such as paper, plastic film, foil, fabric, and other flexible web materials that need to be slit to a specific size before use in production.

Equipment Used in Slitting: Slitting Machines

The main equipment used in slitting is a slitting machine, also known as a slitter machine. It combines unwinding, slitting, and rewinding in one continuous operation.

The parent roll is first unwind, guided through the slitting section, slit into the required widths, and then rewind into smaller finished rolls. Depending on the material and production requirements, manufacturers will use different slitting systems.

Types of Slitting Methods

Different materials and production goals call for different slitting methods. Material thickness, flexibility, required edge quality, cutting speed, and dust control all play a part in choosing the right method for an application.

Here are three common types of slitting methods:

• Razor Slitting

  

  Razor slitting uses a thin, straight blade to slit directly through moving material. It's one of the simplest methods and is often used for thin, flexible materials like plastic film, light foil, paper, and laminated films.

  Razor slitting is divided into two methods:

  • Razor in Air

    In razor-in-air slitting, the blade slits through the material without lower support at the slitting point. The setup is simple and efficient, but cutting results depend heavily on stable web tension. If the material isn't properly tensioned, the slitting line may shift, affecting width and edge consistency.

  • Razor in Groove

    Razor-in-groove slitting uses a blade that slits into a groove on the lower roller, providing support and guiding the slitting line. This method is chosen when the application requires more control and precision.

• Shear Slitting

  

  Shear slitting works like a pair of scissors. The material passes between upper and lower circular knives, and the two knives slit the web through a shearing action. It provides good edge quality and produces less dust, making it suitable for films and paper materials.

  There are two common ways to set up shear slitting:

  • Tangential Web Path

    In tangent slitting, the material passes across the slitting point without wrapping around the lower knife. The material has a more direct path through the slitting section. This method works better for stiffer materials because they don’t have to bend over the knife.

  • Wrap Angle

    In comparison, the material wraps around the lower knife in wrap slitting. This creates more contact and stability at the slitting point, which can help improve slitting control. However, it's a better fit for flexible materials, since rigid materials can deform when wrapped around the knife.

• Crush Slitting

  Crush slitting separates the material by pressing the upper knife into the material against a lower anvil. Instead of slicing or shearing the material, it uses pressure to crush and separate the web along the cutting line.

  The setup is simple and cost-effective, but it produces more dust and rougher edges. It's applied to materials that can tolerate pressure-based cutting, such as nonwoven materials, certain textiles, rubber, and thicker or tougher web materials.

Knife Setup Requirements by Slitting Method

Choosing a slitting method is only the first step. To achieve stable slitting quality, each knife system must also be set up correctly.

• Razor Slitting Knife Setup

  For razor slitting, blade penetration depth and blade angle must be precisely set according to the material being processed. The blade should enter the material at the correct depth and angle.

  If the blade penetration is too shallow, the material may not be fully slit. If the blade enters too deeply or at the wrong angle, it can create rough edges, increase blade wear, damage the material, and create safety risks during the operation.

• Shear Slitting Knife Setup

  The setup for shear slitting should consider knife overlap, side clearance, shaft parallelism, and knife pressure control. These settings ensure that the upper and lower circular knives meet at the correct position and pressure to create a clean scissor cut.

  Poor setup can affect edge smoothness, burr formation, and blade life. Too much pressure can increase blade wear, while incorrect clearance or overlap may create rough edges, uneven cuts, or unnecessary stress.

• Crush Slitting Knife Setup

  Knife pressure depth, anvil material, and the hardness match between the knife wheel and anvil are key considerations for the crush slitting setup. Since it separates material through pressure, the knife and anvil must work together without over-compressing the web or damaging the edge.

  Improper setup can cause excessive indentation, higher dust levels, rougher edges, or greater edge crushing.

Common Types of Knife Positioning Systems

The knife positioning system directly affects setup time, operator workload, and slitting consistency. These systems can be grouped into three types depending on the level of automation:

• Manual Knife Positioning System

  In a manual knife positioning system, operators measure and adjust each knife position by hand. Although it's easy and cost-efficient, it depends heavily on operator experience. It's also more time-consuming when there are more knives or frequent job changes.

• Semi-Automatic Knife Positioning System

  A semi-automatic knife positioning system uses both machine-assisted and manual operations for positioning and adjustments. It can help reduce setup time and improve positioning consistency, especially when operators need to repeat similar cutting widths.

• Fully Automatic Knife Positioning System

  

  With a fully automatic knife positioning system, the knives are automatically positioned according to the required slitting specifications. This helps reduce manual setup work and makes knife arrangement faster, more accurate, and more repeatable.

Improve Slitting Quality with Yo Den Slitting Machines

Slitting quality depends on choosing the right slitting method, knife setup, and positioning system for your material. That's why it's crucial to work with a slitting machine manufacturer you can trust.

Founded in 1994, Yo Den brings decades of engineering expertise to slitting machine manufacturing and customization. We provide slitting machines for various industries, including packaging, printing, electronics, and medical manufacturing.

To help manufacturers improve slitting quality and efficiency, Yo Den offers customized slitting machines and knife positioning solutions, such as automatic shear knife positioning systems, automatic razor knife positioning systems, and crush slitting systems.

Contact us now to discuss the right slitting machine configuration for your production needs.