Modern methods of cutting sheet metal

02/14/2019 Author: VT-METALL

Issues discussed in the material:

• How to choose the most economical method of cutting metal
• What are the main methods of cutting metal
• How to select a method and cut metal after cutting

In the technological chain of manufacturing metal structures, cutting of profiled metal products plays an important role. The complexity of further processing and assembly, as well as the quality of the finished product, depends on how accurately and correctly this operation is performed. Over the long history of metalworking, a large number of different technologies have been developed. In our article we will look at the main methods of metal cutting that are used in modern manufacturing enterprises.

How to choose the most economical method of cutting metal

When cutting, special attention is paid to the location of the workpiece on the strip or sheet of metal. Most often, product blanks have a shape close to rectangular, but often there are parts that have a more complex contour.

In the process of manufacturing metal blanks, waste is generated, the volume of which is determined by the correct choice of cutting method.

There are two types of waste generated during the production of metal products:

• Process waste refers to material that is lost due to melting during cutting (melting during high-temperature cutting and chips or irregularities during mechanical cutting).
• Cutting waste consists of the material of sheets, strips, rods, etc., which remains untouched by a certain method of manufacturing blanks.

The production of cutting waste is determined by two factors, according to which they can be divided into two groups:

• mold waste;
• non-recycling waste.

Mold waste is material that is located between the contours of several workpieces within a rectangle that encloses their shapes and remains unused (for example, between the abed rectangle and the perimeter of the workpiece).

Non-recyclable waste refers to unused sheet metal or other rolled metal, the dimensions of which are greater than the sum of the dimensions of the workpieces.

In order to obtain the largest possible number of blanks from rolled metal, it is necessary to select the most optimal cutting method, which is accompanied by the least amount of waste. To do this, you need to take into account the features of the technology for obtaining blanks.

Basic methods of cutting metal

In production, to optimize metal cutting, the most advantageous technology for separating rolled metal into blanks is selected. For example, the advantage of using a torch or rotary shear is that the blanks for production can be placed anywhere on the sheet metal. If guillotine shears are used to cut the material, then a number of restrictions appear on the choice of location of the workpiece contour. It should be positioned in such a way that it is possible to perform a straight cut along the length and width of the sheet and straight cutting at an angle.

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For industrial production of large batches of products, it is more logical to use a combined cutting method. In this case, blanks of various shapes are combined in such a way that they can be folded into rectangles with the smallest possible dimensions. With the help of such rectangles, the filling of the metal sheet is optimized.

The method of rationally filling the sheet along the width ensures a reduction in the volume of non-folding waste. The unused part of the sheet in this case will be smaller than when the forms are arranged along the length of the sheet. It is necessary to select a combination of blanks in such a way that the sum of their sizes contributes to the most complete filling of the smaller side of the sheet. The same technique is used to mark along the length of the sheet.

The marking method by forming dimensional sequences involves placing blanks for cutting from larger to smaller ones. The task of optimizing metal cutting is solved by special technological groups. They receive a monthly request from production units, which indicates the required types of workpieces. The application contains the order number, drawings of finished products, grade of metal and standards for its consumption. Based on the received drawings, employees of the technological groups group products by metal grade and the required thickness of the workpieces.

After this, taking into account the dimensions of the metal sheets that are present in the enterprise’s warehouse, cutting maps are drawn up. First, the approximate number of required sheets of metal is calculated. Then the technologists draw their dimensions on the most convenient scale. In the same size it is necessary to cut templates for making blanks on paper. The cut stencils are combined on the drawings of metal sheets in such a way as to minimize costs.

After completing work on technological cutting charts, a picking list is drawn up. Based on the data in such a document, you need to select the metal and transfer it along with the documentation to the workshop. For the performer of the blank production process, the working document is the cutting map. If, in order to produce the required number of blanks, only a part of a whole sheet of metal is needed, then the remaining material, which is called “business waste,” is returned to the warehouse with an appropriate entry made in the accounting documents.

The method of cutting metal described above is called operational, since it is based on obtaining information about the availability of material in the warehouse. In production, the method of perspective cutting can also be used. It is applicable for mass production of repeating products. In this case, technological maps are drawn up approximately 6 months before the release date of a batch of products and an order for a measuring sheet is placed on them.

Cutting plans are not drawn up if the workpieces are made not from sheet metal, but from rolled profiles. Rods, channels, angles and other rolled products are issued to production areas in length measurements, taking into account the dimensions of the workpieces and allowance standards for cutting. After cutting is completed, the remains are marked and transferred to the warehouse. To optimize the consumption of rolled profiles, metal blanks should be produced centrally. The selection of materials is carried out depending on the brand, profile and size so that the workpiece is a multiple of the dimensions of the rolled metal.

Basic methods of metal cutting

Guillotine cutting.

In the field of metal products production, a variety of equipment is used that allows efficient cutting of metal in different ways. For cutting materials with a thickness of 0.45–2.5 mm, simple mechanical devices are used, and for thicker metals (20 mm), electric or pneumatic guillotine-type shears are used (such equipment allows for direct, clean cuts).

Affordable mechanical guillotine equipment (for example, machines for cutting metal sheets) is popular in the construction industry for the production of products from galvanized sheets or metal tiles. Using such devices, window sills, cornice overhangs and other elements are made. The biggest disadvantage of guillotines (hydraulic, pneumatic or electromechanical) is that such equipment can only perform straight cuts.

Metal cutting with band and circular saws.

If the chosen method of cutting metal does not require high precision, then the most popular solution for cutting the material would be to use an angle grinder (a regular “grinder”).

Stationary saws that can handle large-diameter blades allow you to produce workpieces with more accurate dimensions. Such equipment is used in small-scale production of metal products for construction and industry. When choosing this cutting method, the cutting thickness is 0.08 cm. Its advantage is that the material can be cut at an angle. But in this way it is very difficult to make a figured cut along a curved perimeter.

Perforating presses.

In the industrial production of aluminum structures or for finishing metal sheets (for example, for the production of expanded metal sheets), special expanded metal presses are used.

Oxygen gas cutting

– a highly productive method of cutting metal, which is used in various production areas. Its disadvantage is that it produces a wide cut, along the edges of which scale with unevenness is formed. In addition, the oxygen gas river cannot be used for cutting thin sheets of metal.

Guillotine cutting

The history of this equipment, according to official data, dates back to the times of the French Revolution. At that time, it was used to eliminate “enemies of the people” and only many years later, another application was found for it, namely, in cutting sheet metal. Using some devices on a guillotine (mechanical shears), you can cut rolled steel and reinforcement.

Sheet cutting occurs during a series of operations.

1. The sheet is placed on the desktop. On the back of the machine there is a ruler on which the size of the workpiece to be cut is set.
2. Once the sheet is positioned, the machine operator starts it. The front plate presses the sheet to the table surface, the second plate, on which the knives are installed, then lowers and, under its own weight, cuts the sheet into the specified size.

It should be noted that if the knives are properly sharpened and installed with a minimum error, then the cut is obtained without burrs or jams. At the same time, there will be no curvature on the sheet, since the cut occurs along the entire length of the sheet at the same time.

Guillotine cutting

Equipment of this class is equipped with electric motors. For some brands, for example, H177, the front and rear plates are moved using a mechanism based on a fairly large flywheel. On such machines it is permissible to cut sheets up to 12 - 14 mm; of course, the thickness depends on the properties and brand of the material.

There are machines of this class in which the plates are moved using a hydraulic mechanism. But unlike mechanical devices, they require careful treatment, constant monitoring of the level and condition of the oil, etc. On such machines it is permissible to cut materials up to 30 mm thick.

Modern guillotine shears are equipped with digital sizing technology, the ability to adjust the cutting force and other options. There are also machines equipped with numerical control systems. Equipment of this class performs metal cutting with minimal errors.

Hand scissors are used to create products from tin (galvanized metal). Depending on the design, they can be used to cut sheet metal with a width of two or more meters and a thickness of up to 20 mm.

There is another type of guillotine - saber. They are also used in handicraft workshops or small industries.

Guillotine for cutting metal of saber type

By the way, guillotine-type scissors have found their use not only in the manufacture of metal structures but also in printing; they are used to cut large stacks of paper.

Laser and plasma cutting of metal

The main advantage of this cutting method is the high productivity of the process and the ability to perform figured cuts when making blanks from metal sheets.

For plasma cutting, the technology of heating the metal in the area of ​​the cutting line is used with further removal of the melt by a plasma flow. For this purpose, the energy of an electric arc is used. The high temperature of the ionized gas flow (from +15,000 to +30,000 °C) provides the necessary speed for cutting metal. Plasma cutting is the most effective way to cut metal sheets.

Considering the advantages of this method, in addition to high cutting accuracy, we should highlight:

• Possibility of use for the production of workpieces of complex shapes.
• No thermal deformation of the metal.
• Efficient for producing repeatable, uniform products with contour tolerances of up to 0.5 mm.
• The cutting method is completely safe and environmentally friendly.
• Possibility of use for cutting ferrous metal, as well as stainless steel of different thicknesses.

The plasma cutting method can be used for:

• Aluminum blanks up to 12 cm thick.
• Copper and bronze alloys up to 8 cm thick.
• Alloy steel sheets up to 5 cm thick.

Different permissible cut thicknesses for different metals are due to their thermal conductivity characteristics. The thicker the sheet, the less economically profitable this cutting method is, since energy costs increase significantly.

Enterprise equipment

Our production park has laser cutting machines with the following technical characteristics: Model – BODOR F3015-1000W

Power – 1000W Maximum load on the table – 900kg Positioning accuracy – 0.03mm Minimum sheet thickness for cutting – 1mm Maximum sheet thickness for cutting – 12mm Table dimensions – 3000×1524mm Working speed – 8.0-10m/min (with a steel thickness of 1mm) Type control – CNC Note – Cutting head with autofocus
Model – BODOR P3015-3000W IPG
Power – 3000W Maximum table load – 900kg Positioning accuracy – 0.05mm Minimum sheet thickness for cutting – 1mm Maximum sheet thickness for cutting – 20mm Table dimensions – 3000×1524mm Operating speed – 30-40m/min (with a steel thickness of 1mm) Control type – CNC Note – function for determining the position of the sheet
Model – Fanuc C1000i-MODEL C

Power – 1000W Maximum load on the table – 750 kg Positioning accuracy – 0.03mm Minimum sheet thickness for cutting – 1mm Maximum sheet thickness for cutting – 10mm Table dimensions – 700x1500mm Operating speed – m/min (with a steel thickness of 1mm) Control type – CNC Note – carbon dioxide laser

Disadvantages of plasma cutting:

• Increases edge hardness at high temperatures.
• The presence of a tarnished zone and a rainbow change in color of materials along the cutting line.

The catalogs of manufacturers of metalworking equipment present a wide selection of devices of different classes. For cutting metals, contact devices demonstrate high efficiency. This cutting method is based on the use of an electric arc between a sheet of material and an electrode.

Main elements of plasma cutting equipment:

• The plasma torch ensures the conversion of electric arc energy into plasma heat.
• Power supply.
• A compressor or gas cylinder provides a gas jet.

Only highly qualified specialists can cut metal using plasma cutting. It is necessary to maintain a stable gap between the sheet plane and the nozzle. This is a rather complex and responsible process, since uneven movement of the cutter during cutting causes the appearance of sagging along the edges of the metal and the formation of scale. The laser cutting method is based on focusing radiation, in which thermal energy is concentrated, at the cutting point. When using this technology, it is possible to obtain thin cuts with high accuracy and minimal distances between marking lines. The cutting process itself is fully automated. Robotic equipment carries out precise movement of the laser according to electronic drawings, which are entered into the machine program.

Advantages of laser metal cutting:

• Ability to cut along complex closed curved contours.
• Economical material consumption is ensured by the most dense arrangement of workpiece parts on a sheet of metal and the use of software cutting, which reduces the likelihood of errors.
• Metal cutting is carried out without prolonged mechanical or thermal effects, so the edges of the workpieces are not deformed and there is no tarnishing color.
• After cutting the workpiece, perpendicular edges with a low roughness coefficient are obtained.

Disadvantages of cutting metal with a laser:

• The thickness of the metal cannot exceed 2 cm.
• When using this cutting method, cutting performance decreases significantly when processing materials with high reflective characteristics (for example, polished stainless steel). This is due to a decrease in laser power.

Laser cutting of sheet steel is widely used in the production of serial parts with high precision requirements in the automotive industry, in the production of high-precision equipment, exclusive decorative products, etc.

Laser and plasma cutting methods are relatively new technologies that are becoming increasingly used in various fields.

Ultra-precision cutting technologies

Ultra-precise cutting of metals is carried out using thermal, thermochemical processing of the material. These include plasma and laser cutting.

Cutting by these methods is based on a narrowly targeted effect on a specific point of a metal sheet with a laser or plasma beam.

The zone in which the impact point is located is considered to be a catalyst for oxidation occurring as a result of thermal exposure. It is supported by oxygen flow during combustion.

Thermal oxidation can be controlled. To do this, the nozzle can be moved, and the high-temperature zone will move accordingly.

In this way, it is possible to achieve penetration of the sheet along the contour of the workpiece by plasma or laser.

If the need arises, you can make a hole in any place on the workpiece in the same way. All operations must be performed on special equipment.

How to choose a metal cutting method based on the cutting method

As noted earlier, the correct choice of cutting method is a very important stage in the manufacture of blanks and sheet metal parts. A number of points depend on this: the quality of the edge, the accuracy of the cut, the amount of material waste and additional processing after cutting.

Advantages of laser cutting

Laser metal processing technology is best suited for industrial work due to a number of advantages. Laser cutting can be used to finish materials that are easily deformed. The technology is easily used in working with carbide metal products. In production, it is less expensive to cut parts with a laser, which will operate according to a clearly defined drawing prepared on a computer. Materials undergo almost no deformation during laser processing, since there is no mechanical contact with the product.