Posted on Dec 31, 20194
In the production process of slit metal there are a lot of supportive equipment involved in the production line. Regarding its working concept, roll slitting is an operation of shearing which cuts a large roll of metal material into narrower rolls without further quality change during the process.
Considering the materials, there are primarily two types of slitting. They are, log slitting and rewind slitting. In log slitting model, the roll of material is treated as a whole, i.e. the log, and one or more slices are taken from it without specific unrolling and re-reeling process.
On the other hands, the in rewind slitting the web is unwound and run through the machine, which passes through cutting tools such as knives before being rewound on the shaft in order to form narrower rolls. The multiple narrower strips of metal material are called as pancakes if their diameter is much more than their width. Speaking of the rewind slitting the machine used is called a slitter, slitter re-winder, or a slitting machine. These names are used interchangeably for the same machines.
In some cases when the band width is specifically narrow and the material is thin, the pancakes (as we mentioned above) would be unstable so that the rewind process will be onto a bobbin-like reel which is wider than the slit width and the web oscillates across the reel as it is rewound. For these extreme cases the metal materials would be different so that the specific purpose is to be achieved..
In the case of harder materials to be slit, such as sheet metal, high carbon steel, etc, the blades cannot be used. Instead of the blades or knives, a modified form of shearing is used for the cutting purpose. There will be two cylindrical rolls with matching ribs and grooves are used to cut a large roll into multiple narrower rolls.
This continuous line of metalworking production process is practical and precise at the same time. Normally, it is more precise than most other cutting processes in the industry. However, the occurrence of rough edges as burrs are commonplace on the slit edges so that further finishing is needed. In addition, the geometry of these rolls is determined by specific tolerances in addition to the type of material and work piece thickness and width. For this application type, it is also called die cutting, or shearing.
In the field of metalworking, die cutting, or shearing are the same thing in which a process which cuts stock without the formation of chips or the use of burning or melting procedure.
Theoretically speaking, if the cutting blades are straight, the process is called shearing; if the cutting blades are rather curved, then they are shearing type procedures. The most commonly sheared materials in the market nowadays are in the form of sheet metal or plates, yet rods can be sheared as well. Shearing type machining includes (but not limited to) blanking, piercing, roll slitting, and trimming. The cutting method is not confined to metalworking but is also widely applied in the industrial sectors of paper and plastics manufacturing.
In the purchase procedure, what concerns customers and decision makers regarding the slitting machine (or say, slitting line) are complicated. Those issues are based on the end product requirements. They are the minimum slitting width, slitting nos., slitting shaft, slit blade material, slit blade hardness, suitable slitting material essence, suitable slitting thickness, suitable slitting width, suitable interior diameter, suitable outer diameter, maximum coil weight, end product of coil interior diameter, end product of coil outer diameter, maximum coil weight of end product, running speed, slitting width accuracy, power supply, feeding direction, machine central height, net weight, just to name a few.
In the official procedure, a punching blade is used to push a work piece against the die, which is fixed blade as called by the operators. Usually the clearance between the two is about 5% to 40% regarding the thickness of the materials, but is also dependent on the material specifications.
Clearance is defined as the separation between the blades, which is measured at the point where the cutting action occur and perpendicular to the direction of the blade movement. This affects the finishing of the cut (to modify the burr issue) and the machine's power consumption. This process causes the material to experience highly localized shear stresses between the punching tool and the die.
The work piece will fail when the punching is activated about 15% to 60% the thickness of the work piece, as the shear stresses are greater than the shear strength of the work piece, and the remainder of the material is torn.
Machines used to create slit coil are typically composed of stations for uncoiling, slitting, and recoiling. The thicknesses and the widths that a coil can be cut is based on the machine specification. Machines used for the slitting process can run both ferrous and non-ferrous materials and the models are depending on the machine types, may be used for sheet metal or rolled coils.
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