Slitter Rewinder

Slitter rewinder is one of the important machineries used for slitting varieties of materials, like papers, plastics, metal sheets, etc.

In Filter Manufacturing Industry
Slitter rewinders are largely used in the manufacturing of filter making machines. They trim the edges of the filter paper to the required sizes. Usually the slitter rewinders in the filter manufacturing industry are designed for undertaking slitting of large size filter paper reels. Quite often the manufacturers need to procure their filter paper in large width jumbo reels and thus it is quite helpful. They help the manufacturers save those extra charges, as they diminish the wastage as paper is slit to specific sizes just before the production.

Slitting Modes
There are three common slitting methods used today, which are quite popular. Each method works on distinctly different principles. These principles need to be understood prior to making a decision that which slitting method is preferred for a given material. They are Shear, Crush(Score), and Razor.

• Razor Slitting: Razor slitting is the simplest, cleanest and cheapest slitting method, assuming the appropriate materials are being slit. This method can be easily adapted to almost any machine and in almost any location. It is most generally used for light gauze films. The razor blades are cheap and simple to setup and replace.
  
  The resulting slit edge depends on the characteristics, like material thickness, plasticity, density, coating, rigidity, bonding, and many other factors. There are certain points which need to be take care while the razor slitting process. They are: blade life, slit edge quality, and safety.
  • Blade Life: As a very small section of the razor blade is engaged in the slitting zone, so the wear and tear of the extremely thin edge is rapid, and it may fail frequently at critical times. It can cause down times in the process lines.
    
    
  • Slit Edge Quality: A typical raised edge may be displayed for thicker and denser materials. Surface coatings may be disrupted, tearing or splitting may propagate from the cutting point.
    
    
  • Safety: It is the most frequent problem. Exposed razors and their handling during replacement require extreme care and attention. It may results in frequent accidents.
  
  
  
• Crush (Score) Slitting: Crush slitting or score slitting is the most dusty slitting methods, providing the poorest edge quality. This method is more complex than razor slitting. It is commonly used for adhesives and certain papers. It requires the installation of a hardened anvil roll and wrapping the web over the roll. The slit occurs in the crushing nip between the anvil and the slitting wheel. However, changing slit widths is relatively easy and only the slitter is repositioned over the fixed anvil roll.
  • Blade Life: The blade exerts significant amount of force on the anvil roll, as a result the metals suffer repetitive stress cycle failure. The cheaper slitter blade edges deteriorate the slit quality and the anvil surface becomes grooved. The blade life is mostly depends upon the parameters of metal durability, nip stress, and number of stress cycles (actual number of slitter revolutions at any given nip stress).
    
    
  • Slit Edge Quality: Slit edge quality depends on the blade edge profile, blade edge finish, material being slit, and anvil smoothness.
    
    
  • Slitting Speed: The slitting speed is limited by two important factors. One is critical speed of the anvil roll, and other is the ability of the blade steel to absorb high repetitive stress cycle rates. Its solution is to increase the diameters of the anvil rolls and slitter wheels, wherever possible.
• Shear Slitting: Shear slitting is the most versatile slitting method, which can accommodate a broader variety of materials than the two above defined methods. It can be used for a wide variety of papers, films, laminates and foils. The shear slitting variations may be 'tangential/kiss' or 'wrap' shear. It involves a loaded male blade against a female ring, thus creating a scissoring effect to slit the material. It provides the highest quality edge. The points which decide the functioning are:
  • Complexity of changing the slit width
  • Precision of the nip con-figuration
  • Blade wear

Types of Slitters/Slitter Rewinders

• Duplex Slitter Rewinders: They can be used for any material including papers, laminates, films, non-wovens, pressure sensitives, etc. They have two rewind shafts, which allow for cut separation and excellent tension control of virtually any material.
  
  
• Duplex Center Slitter: These machines are generally used in the label industry to inspect rolls. Sometimes they have sophisticated equipment, which help detect print skips, splices, or things of that type. They are used by the converters to rewind poorly wound rolls, to slit rolls into narrower widths. It is operated easily with the help of the cantilevered feature. These machines can be equipped with score, razor, or shear slitting.
  
  
• Simplex Slitter: The simplex slitters wind material on one shaft. They are used mainly for paper, laminates or other materials, which don't tend to stretch and have little gauze variation. Due to the single shaft on the rewind, they are very productive.
  
  
• Single Knife Cutter: In these type of machines, there is no need to unwind or remind the substrate. They are used to cut small diameter rolls. The log of material is kept on a mandrel, matching the inside core diameter, and then rotated while a rotating blade is inserted into the log at the appropriate widths.
  
  
• Turret Slitter Rewinders: The Turret Slitters use a 'rotating rewind shaft' system, consisting of two sets of rewind shafts, which help minimize down-time. It does so by allowing the slitter to keep running while the operator removes finished rolls and sets up new cores. Varieties of automated material handling solutions are used to decrease the level of down-time for high volume converters.
  • These systems provide maximum productivity.
  • They can be used for narrow web or wide web applications.
  • The Inspection turret slitter rewinders are mainly used in the label industry.
  • They have duplex winding capabilities combined with the functionality of a turret rewind system.
  • This is ideal for high speed automated winding of small diameter rolls.
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• Duplex Center Surface Slitter: They can wind rolls both from the center as well as the surface.

Other Slitter Rewinders

• Cantilevered Slitter Rewinders: By definition, cantilevered slitter rewinders are machines provided with rewind shafts that are supported on one end. They are actually supported during the run-time for optimum performance. As the rewind set is finished, shaft supports lower out of the way allowing finished rolls to be easily removed and new cores to be setup. It helps the operators to never handle heavy shafts or tooling. These machines are widely popular in the industry due to the decreased down-time between sets. They eradicate the need to handle heavy shafts by operators, so it results in improved ergonomics.
  
  
• Center Surface Slitter Rewinders: The center surface winding is mainly used for rewinding large diameter rolls on extended web width applications. They are found in various models including lift-out mandrel, cantilevered and with multiple individual shaft-less rewinds.

Characteristics of the Material Being Slit: The properties of materials being slit determines the type of slitting process to be used, type of blades, effectiveness of slitting, etc.

• Density: The low density materials compress in the slitting nip. However high density materials may benefit from radically different blade profiles.
  
  
• Elongation: The elongation of the material determine whether the material will recover after being slit.
  
  
• Stiffness: If the material seems extremely stiff then it will have a conflict with slitter blade.
  
  
• Caliper: It is the measurement of thickness of materials to be slit. It determines what type of blade should be used.
  
  
• Compressibility: It is essential for the material to recover from compression. It helps minimize edge distortion.
  
  
• Abrasiveness: Abrasiveness of the materials are responsible for wearing out the extreme tip of the slitter blade.

The materials to be slit possess these properties, some in lesser extent while some in larger extent. To achieve the optimum slitting quality, it's essential to identify the dominant property of the material and design the slitting system accordingly.

Applications
The slitter rewinders are used in a large number of industries. Their use and applications vary from one industry to another. They are dominantly used in the making of filter manufacturing machines.

• Filter Machine Industry
• Paper Industry
• Steel Industry
• Packaging Industry
• Electronic Industry
• Printing Industry
• Medical Industry