Used cut-to-length lines
Contents
Classic structure and function of cut-to-length lines
Performance of cut-to-length lines
What can the automation of cut-to-length lines look like?
Tools and equipment for cut-to-length lines
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Cut-to-length lines - more than just right-angled cutting of sheets
Cut-to-length lines, also known as sheet cutting lines, are an important type of machine for the entire industry. As a rule, the cut-to-length lines are operated by suppliers (e.g. service centers). From there, blanks and metal sheets are delivered to the automotive industry, for example, in order to be processed into products such as deep punching articles or body shells on press lines or in forming machines.
Cut-to-length lines are used amoung other applications in the metal industry and also paper industry. In this treatise, cutting systems for the metal industry are considered. Cut-to-length lines are used for metals made of steel, aluminum and other non-ferrous metals.
The cut-to-length lines belong to the field of production technology, more precisely to the production process "material separating". Blanks are cut in rectangular, trapezoidal or curved shapes from a wide ring, also known as a coil. The cutting is done by cut-to-length process shears.
Classic structure and function of cut-to-length lines
The basic arrangement of a cut-to-length line is a horizontal material flow, either from right to left or from left to right. The information relates to the position from the operator's side. The operator's side with the control panels is freely accessible by the operator. The side opposite the operating side is referred to as the drive or motor side. If the current safety rules are observed, this area is not accessible in normal and automatic operation of the cut-to-length line.
The structure of a cut-to-length line consists of many individual machines, which are connected to one another with tables, roller tables and conveyor belts.
It starts with a coil or coil store. This can be designed as a ramp or as a carousel. The input coil store is equipped with a crane or self-propelled vehicles. Flange bearings can be designed with or without floor rollers.
From the coil store, the coil freed from the binding tape is transported by a coilcar onto the decoiler with a pressure roller and coil bending device. The coil eye (inside diameter of the coil) is aligned with the decoiler mandrel by the lifting function of the coilcar. It is important that the diameter of the coil eye matches the decoiler mandrel. The decoiler mandrel is adapted to the coil eye diameter using screwed segments. There are also mandrels with a large expansion range. These mandrels can work without attachment segments.
Depending on the width of the raw material and the weight of the coil, the decoiler must be equipped with a mandrel support bearing on the operator's side. For loading or unloading the mandrel, the mandrel support bearing is swiveled, moved or sunk, depending on the design.
After aligning and tensioning the coil on the coileye by the mandrel, the strip is unwound by rotating the mandrel and transported via a telescopic table into the entry pinchroll and the straightening machine. A strip center control positions the center of the strip to the center of the line by shifting the decoiler.
Cropping shears are usually used after the pre-straightening machine. The crop shears make a straight initial cut. The cut sheet metal is transported to a retractable scrap box via a scrap switch on the transfer table. It is of course also possible to cut several sheets of scrap that are defined in length and convey them to the scrap box. When the straightening process should start, the wide strip must be conveyed on over the transfer table.
Depending on requirements, side trimming shears are used in front of the levellers to straighten the strip sides. During the trimming operation, both edges of the strip material are cut off. These outer strips are scrap. This is discharged downwards and can be wound up with a strip winder or shredded with a scrap cutter. In both cases, the scrap ends up wrapped or shredded in containers.
After the edges have been separated by the side trimming shear, the strip material is fed to the levelller via a roller table. The leveller machine is used to straighten (smoothing) strips that are unwound from the coil in the transverse and longitudinal directions. The levelling machine consists of the upper and lower rollers. The upper rollers can be raised and tilted together to enable the beginning of the strip to be inserted. During straightening, the upper set of rollers then plunges into the spaces between the lower set of rollers; the dipping rate is greater at the entrance and decreases towards the exit of the levelling machine to such an extent that the last two rollers only touch the strip. There is no more immersion at the exit.
The strip, which is flat in the longitudinal and transverse directions, is conveyed after the leveller in the direction of the cut-to-length shear. A high-precision measuring wheel is arranged in front of a pinchroll, which is in front of the cut-to-length shear. The measuring wheel records the exact length of the run-through strip and thus controls the cut-to-length shears. The driver, which is arranged between the measuring wheel and the cut-to-length shears, has the function of keeping the strip from the levelling machine tight and, on the other hand, of keeping the shocks and vibrations coming from the cut-to-length shears away from the measuring wheel. The speed of the material is also recorded.
Before the blanks can be cut, the cut-to-length shears must perform a reference cut. The cut reference sheet is transported via a scrap switch into a box behind the cut-to-length shear. After one or more reference cuts, the blanks are produced.
The designs of the cut-to-length shears are versatile. In the thin strip area, so-called drum shears are often used, in the thickness range from 0.3 to 6 mm rotating shears are optimally used and in the thick strip area the flying slide shears have prevailed in the past. But the rotating eccentric shears can at least serve the area up to 16 mm material thickness. The crowning glory of the cross-cutting shears is the tilting eccentric shear. They can be used to perform trapezoidal cuts and even curve cuts. The two cutter beams of a cut-to-length shear are each equipped with a long knife.
Simple cut-to-length lines are equipped with start-stop shears. This means that the strip material to be cut must be stopped for each cut. The start-stop principle is mainly known from press feed.
Now we come back to the cut-to-length lines. A cut blank leaves the shears and is conveyed via segmented conveyor belts towards the stacking system. The conveyor belts have to be segmented in order to accelerate the blanks after the cut in order to create a gap from blank to blank. This distance is necessary in order to discard the blanks individually in the stacker above the stacking box.
Since the blanks arrive at the stacker at high speed, they must ideally be braked as much as possible before being dropped so that the kinetic energy of the blanks at the stop does not lead to deformations at the edge of the blanks. Rear, front and side stops ensure that the stack of blanks is built up precisely. As the stack grows, it is continuously lowered by means of stacking lift tables until the number of blanks or the maximum stack height is reached.
The variety of stackers is great. The range is very large, from slide stackers, flap or bomb door stackers, discharge stackers, magnetic belt stackers, vacuum stackers, suction belt stackers, brush stackers, air cushion stackers, segment belt stackers and hybrid stackers. The aerostatic stacker is a special machine. Thin blanks at high speed are often deposited by means of a shingle (overlapping) stacker and finally aligned in the stacking box so that they are positioned one above the other. The use depends on the material of the blanks, the shape and the speed. But this is a topic in itself. Another variant of the stacker is the number of stacking boxes. This can vary in the standards between one and four boxes. The stacking boxes can usually also be interconnected for control purposes in order to be able to produce blanks that are longer than one stacking box.
The blanks are taken over by a stacking lift table under the stacker. Stacking on this table can be done with or without a pallet. The stacking tables can be moved out of the stacker from the side either individually or, in the case of long formats, coupled. The stacking tables transfer the stacked blanks to segmented roller tables and chain conveyors. There the piled blanks are packed manually or conveyed to a packaging line.
The packaging can consist of the following components, depending on the end customer's packaging key: pallet, film and / or paper, edge protection, inner strapping, outer strapping, closures and closure protection, metal covers, shrink or stretch film.
Pneumatics, hydraulics, electrics and controls are other essential components for the function of a cut-to-length line.
Performance of cut-to-length lines
Cut-to-length lines are also available for various materials for thickness ranges from less than 0.1 mm to areas of one inch. Most systems have a thickness range of 0.3 to 4 mm. In terms of width, the current systems are between 950 and 1750 mm. However, cut-to-length lines from 450 to 2800 mm are available.
The speed ranges depend heavily on the material, surface quality and material thickness. Systems from 0.3 to 4 mm reach up to 120 m / min., thinner materials, especially with overlapping stacking and lengths close to synchronism, 400 m / min. and more can be achieved. Thicker materials are driven more slowly.
What can the automation of cut-to-length lines look like?
As in many other areas, the possible degree of automation is also a question of investment. Cut-to-length lines can be automatically linked with coil preparation stations and packaging systems. Manual intervention is then no longer necessary for feeding in the coils and removing the packages.
The operator then mainly takes on control tasks and tasks such as setting and setting up. The personnel deployed must be very qualified.
Typical automation features for cut-to-length lines are:
· Coil preparation station with and without automatic strap removal
· Automatic width and thickness measurement
· Automatic measurement of the blanks for dimensional accuracy and shape
· Automatic knife change of the cut-to-length shears
· Automatic oiling and de-oiling or brushing machines
· Automatic surface inspection equipment
· Process optimization through better division of the safety zones
This list does not claim to be complete.
Tools and equipment for cut-to-length lines
In cut-to-length lines, the term tools mainly refers to the long knives of the cut-to-length shears and cropping shears.
In addition, there are operating materials such as brushes and oils, depending on the equipment.
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tramao offers you a large selection of new and used sheet cutting lines or cut-to-length systems. You will also find the right service companies for repairs and spare parts procurement on tramao.de.
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Not to be forgotten is our range of tools.
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