Tempo di lettura stimato: 19 minuti

Mechanical cutting（especially for hydraulic shear cutting machine） is the use of special cut mechanical equipment for cutting separation of sheet metal, which is the most common cutting method used in sheet metal blanking processing. It has the advantages of high production and processing efficiency, cutting precision is higher, but need to have special cutting equipment.

1. Mechanical Cutting Equipment

Mechanical cutting equipment mainly has the cesoia, vibration shearing machine, roll shearing machine, and so on.

The Shearing machine is mainly used for cutting plate, and can only cut straight lines, its working principle is through the use of the upper and lower blade for straight lines to cut the blank plate, the following picture shows the working principle of the shearing machine diagram, the upper blade 8 is fixed on the knife holder 1, the lower blade 7 is fixed on the lower bed surface 4, the bed surface is installed with a ball 6, in order to facilitate the sheet 5 into the movement, the rear baffle plate 9 for the plate positioning, the position of the adjustment pin 10 to adjust the hydraulic pressing barrel 2 for the plate, to prevent the plate in the shear turnover. Shed board 3 is a safety device to prevent accidents at work. When working, the working crankshaft drives the sliding block of the shearing machine to move, and the relative movement of the upper and lower cutting edges is used to cut off the material.

The Shearing machine according to the different transmission modes is divided into mechanical transmission shearing machine and hydraulic transmission shearing machine. Thickness is less than 10mm of the sheet, the shearing machine is mostly mechanical transmission structure; thickness is greater than 10mm of the sheet, the shearing machine is mostly hydraulic transmission structure.

Vibration shearing machine according to the general model for shear line or, commonly used in material under 2 mm sheet metal processing, the principle of work is the use of mechanical transmission of high-speed movement of the blade back and forth and staggered movement of blade formed under relatively a short cut to the sheet can also be used to cut surfaces of the inner and outer contour curvature radius is larger the shear. Its structure and working principle are shown in the picture.

Rolling shearing machine can achieve straight shear, can also be cut along the curve, using the characteristics of rolling shear can be round or curved, some small batch production of large stamping parts. It can be used to replace die blanking or trimming, but the cutting quality and productivity are not high. Its working principle is to use a pair of disc shear blades with opposite rotation directions to cut the sheet. The following picture (a) shows the structure and working principle of the rolling shear. Picture (b-d) respectively show the centralized configuration method of the disc cutter.

Commonly used sheet metal shearing equipment mainly includes shearing machine and so on.

2. Basic Method of Shearing Machine

According to the different assemblies of the upper and lower blades, the shearing machine is divided into flat blade shear and oblique blade shear. Oblique blade shear is more labor-saving than flat blade shear. It is mostly used for sharing plates with larger width dimensions and thinner thickness. The picture (a) below is a schematic diagram of cutting with inclined blades on the upper and lower blades.

The oblique blade shear can greatly reduce the shearing force. The lower cutting edge of the oblique-blade shearing machine is horizontal, and the upper cutting edge and the lower cutting edge are inclined at a certain angle. The cutting is carried out between the upper and lower cutting edges. Because the upper cutting edge is inclined, the cutting edge and material The contact length is much smaller than the width of the sheet material. Therefore, this shearing machine has a large stroke, small shear force, and stable work. It is suitable for cutting sheets with small thickness and large width.

Generally, the inclination angle Φ of the cutting edge is between 1°-6°. When the sheet thickness is 3-10mm, take Φ=1°-3°, and when the thickness is 12-35mm, take 3°-6°. γ is the rake angle, which can reduce the rotation of the material during shearing; α is the relief angle, which can reduce the friction between the cutting edge and the material. γ generally takes 15°-20°, and α generally takes 1.5°-3°.

The picture (b) below is a schematic diagram of a flat-blade shear using a flat-blade shearing machine, which cuts between the upper and lower parallel cutting edges. β generally takes 0°-15°. This type of shearing machine has a small stroke and large shearing force, which is suitable for shearing large thickness and small width plates.

3. Operative Method of Shearing Machine

The shearing machine uses the blades with the upper and lower blades as straight lines to cut the blank. In order to cut the blank into a certain shape and size during cutting, the gantry shearing machine is equipped with a stopper device. The device consists of a front baffle plate, a rear baffle plate, a side baffle plate, and a special angle baffle plate. The front and rear baffle plates and the side baffle plates can be installed and fixed on the workbench or bed of the shearing machine, and the front, back, left and right positions can be adjusted at any time through the adjustment mechanism. The angled baffle is generally installed in the T-shaped groove of the table, and it can be installed and fastened to different positions on the bed according to the shape of the plate to be cut.

Although many digital displays or digital control shearing machines are currently produced, and automatic positioning control and display are realized on some baffles (such as rear baffles). It greatly facilitates the cutting of blocks and strips of a certain length, but for cutting parts with more complex shapes, manual adjustment of various baffles can still be used to cut. For blanking with more complicated shapes, manual adjustment according to the template is usually used.

One of the important contents of the blanking operation is to adjust the position of the various baffle plates installed on the shearing machine to complete the cutting of strips of different widths and sizes and various shapes and shapes and to ensure and control their quality. The adjustment methods of various baffles are shown in the picture.

• General width strip cutting. For the cutting of the general width of the sheet, it can be carried out by marking or positioning with the back baffle and adjust the position of the back baffle with a screw. When cutting, use a pressing plate to compress the sheet material first, and then lower the pallet with the upper cutting blade. The sheet material is cut when the cutting blades are staggered on the upper and lower sides. Generally, the cutting section does not need subsequent processing to ensure the cutting quality, as shown in picture (a).

• Cutting of larger width strips. For the shearing of large width strips, if the plate is positioned by the rear baffle, its outer overhang will sag due to its own weight, and the larger the ratio B/t of the outer overhang to the thickness of the plate, the positioning error will also be Bigger. Therefore, when the strip width is 300-400mm, the front baffle should be used for positioning, as shown in (b). As for the position of the front baffle, general measuring tools or templates can be used for positioning.

• Trapezoidal and triangular wool cutting. When cutting trapezoidal and triangular wool, you can use the side baffle to coordinate with other baffles for positioning, as shown in (c). When installing, you can first put the template on the table to its lower edge, and then adjust and fix the side baffle. Then, adjust the back baffle according to the template, and use the side baffle and the back baffle to the position at the same time when cutting, as shown in picture (c). In addition, the method of co-locating side baffles and other baffles can also be used, as shown in the picture (d-f).

• Cut the material narrowly. The plate is far away from the pressing device and cannot be pressed. In order to cut safely and smoothly, a backing plate and pressing plate of the same thickness as the cut plate can be added for cutting. The pressing plate can be thicker, as shown in the following picture. It is not necessary to add a backing plate to the thin plate, and the plate material is directly pressed firmly by the pressing plate.

4. Blade Selection for Shearing Machine

Brief Introduction of The Blade

• The blade material of the shearing machine is generally T10, 9CrSI, 6CrW2Si, Cr12MoV, H13, alloy steel, and other materials. Products are widely used in the light industry, aviation, shipbuilding, metallurgy, instrumentation, electrical appliances, stainless steel products, steel structure construction, and decoration industries.

• The shearing machine uses a moving upper blade and a fixed lower blade and uses a reasonable blade gap to apply shearing force to metal plates of various thicknesses so that the plates can be broken and separated according to the required size. The shearing machine is a kind of forging machinery, and its main function is in the metal processing industry. General shears can be divided into pedal type (manpower), mechanical type, hydraulic swing type, hydraulic brake type.

• Shearing machines are often used to cut blanks with straight edges. The shearing process should be able to ensure the straightness and parallelism requirements of the sheared surface of the sheared sheet and minimize the distortion of the sheet to obtain high-quality workpieces.

Blade Material

The materials selected for the shear blades are divided into three categories: carbon-bonded tool steel, low-alloy tool steel, alloy tool steel, etc.

• Carbon-bonded tool steel: Carbon-bonded steel is generally selected from 65, 75 steel, T8, T10, and other materials. The heat treatment hardness of the blades produced by this material is within the range of HRC57-59 degrees, which is suitable for ordinary low-carbon cold-rolled plates and ordinary A3 plates. Compared with the recycling and cutting of waste materials, this feature is low cost and reasonable product price.

• Low-alloy tools: The commonly used materials for the blades of low-alloy tool steel are: 6Crw2sI, Cr5Mo1V, 9CrSi, Cr12MoV, etc. The heat treatment hardness of the blades is within the range of HRC58-62 degrees. Shearing of medium and thick plates.

• Alloy tool steel: The shear blade materials of alloy tool steel are: 4Cr5MoSiV1 (H13K), 7Cr7Mo2V2Si9 (LD), W6Mo5Cr4V2 (6542), H13, etc. The blades of this material are used for hot-rolled steel billets, hot-cutting medium and thick steel plates, etc. This feature is high-temperature resistance, not easy to anneal, and is used for hot rolling and hot shearing processes in steel mills.

5. Cutting Operation Steps And Alignment Methods of Shearing Machine

When performing shearing and cutting operations, first of all, you should strictly abide by the safety operating rules of shearing and blanking; secondly, you should ensure the straightness and parallel requirements of the shearing surface of the sheared plate, and minimize the distortion of the plate to obtain high-quality parts. The following describes its cutting operation steps and alignment method in detail through examples.

The workpiece shown in the picture below is made of a 10mm thick 25 steel plate, and the tolerance of each dimension after cutting is required to be ±1mm. It is cut by a gantry oblique shearing machine. The cutting operation steps and alignment methods are as follows.

Cutting Operation Steps

• Determine the number of shears. For pieces with a large sheet area, one person cannot operate it alone when cutting, and 2~3 people can be arranged to work together. However, one person should be designated to command, and all shearing personnel should coordinate their actions and obey the command.

• Determine the cutting sequence. The cutting of the workpiece often has multiple cutting lines. When cutting on the front bed of the gantry oblique opening, the cutting sequence must comply with the principle that the sheet can be divided into two pieces each time. The above figure shows the cutting sequence of the workpiece, and the cutting is carried out according to the cutting line number.

• Analyze and determine the method of cutting and aligning the workpiece. Cut the workpiece on the gantry oblique shearing machine. There are a variety of workpiece alignment methods, which should be used flexibly on the basis of analyzing the structure of the workpiece. In order to master a variety of alignment methods, the method used for alignment of this workpiece is: the first cutting line is cut by direct visual alignment or the shadow alignment method; the second cutting line is cut by the angle baffle alignment method Cut; the third cutting line is cut by the rear baffle alignment method; the fourth cutting line is cut by the front baffle alignment method.

• Check and adjust the gap of the cutting blade according to the nature and thickness of the material to be cut. If the shearing machine is attached with a shearing blade gap adjustment datasheet, the shearing blade gap should be adjusted according to the data. You can also refer to the following table to determine the shearing blade gap.

Material type	Gap t%	Material type	Gap t%
Electromagnetic pure iron	6-9	Stainless steel	7-13
Mild steel (low carbon steel)	6-9	Low-alloy steel	6-10
Hard steel (medium-carbon or high strength steel)	8-12	Duralumin, brass	6-10
Electrical silicon steel	7-11	Anti-rust aluminum	5-8

• After checking and adjusting the front edge clearance, start the empty car to run, and confirm that the equipment is in good working condition before loading. Before loading, clean the surface of the sheet and check whether the cutting line is clear and correct.

• Cutting. According to the above-determined workpiece cutting method to cut the line. although

• Quality inspection: Measure whether the size of each part of the cut workpiece meets the drawing requirements; check the quality of the cut section of the sheet.

Operation of Cutting Alignment Method

In the following, the workpiece shown in the figure will be cut according to the above-defined cutting and alignment method.

• Cutline 1. Place the sheet on the surface of the shearing machine, push it into the cutting edge, and visually inspect both ends of the cutting line to align the cutting edge of the lower scissors, as shown in the picture. Then, the operator evacuates the cutting opening with both hands to the outside of the pressure plate, presses or steps on the switch, and cuts the sheet.

• Cutline 2. Adjust and fix the corner positioning baffle, and use the baffle as the positioning reference, put the sheet on the shearing bed, and cut the sheet along the cutting line 2, as shown in the picture.

• Cutline 3. When the rear baffle is positioned at the cutting line 3, the position of the rear baffle can be determined by two methods: a direct measurement with a steel ruler, so that the distance from the upper and lower cutting openings to the rear baffle surface is equal to the width of the part to be cut. After the rear baffle is fixed, it is necessary to measure and recheck to ensure accurate positioning. Template positioning method: Place a template with the same width as the material to be cut between the cutting edge and the rear baffle to determine the position of the rear baffle. After the position of the rear baffle is determined, it can be positioned and cut the cutting line 3, as shown in the picture.

• Cutline 4. When the front baffle is positioned at the cutting line 4, the method of determining the position of the front baffle is the same as the method of determining the position of the rear baffle. The position of the front baffle plate is cut as shown in the picture.

6. Precautions For Cutting Operation of Shearing Machine

• Before starting, you must carefully check whether the operating system, clutch, and brake of the shears are in a reliable and effective state and whether the safety devices are intact and reliable. If an abnormality is found, immediate measures shall be taken to strictly prohibit the operation of the equipment with diseases. During the operation of the rigid clutch, it should be ensured that there is no obvious impact sound from the pivot pin and the key.

• The motor should not be started with load, and the clutch should be disconnected before starting. Before the formal operation, the test run must be idling to check whether the tie rods are malfunctioning, whether the screws are loose, and confirm that the components are normal before the formal operation.

• In the cutting operation, the energy must be concentrated. When multiple people are operating, the cutting switch must be operated by a dedicated person, and it is strictly forbidden to reach into the cutting mouth. Concentrate when feeding, and pay special attention to ensuring the safety of your fingers. When a sheet is cut to the end, do not use your fingers to feed under the sheet.

• The blade and the edge of the knife must be sharp. The blade must fit tightly when cutting thin plates. The upper and lower blades must be parallel. Blunt scissors should not be used. Check whether the cutting edge of the cut piece is flat. After adjusting the blade, be sure to perform the manual test and an empty vehicle test first.

• When cutting small pieces of material, padding and pressing should be adopted to prevent accidents caused by improper pressing.

• Do not place other objects and sundries irrelevant to the work on the workbench, and the machine must be shut down for adjustment and cleaning.

• It is strictly forbidden for two people to cut two kinds of sheets on the same shearing machine at the same time. During the operation, no pedal is allowed to be stepped on before the workpiece is calibrated, no air hook is allowed to be pulled, and no head or hands are allowed to be placed under the knife-edge at any time and under any circumstances.

• Keep the surrounding area clean and tidy to ensure that the workpieces or parts are lifted vertically without obstruction.

• It is forbidden to use the front bed to process ultra-long and ultra-thick workpieces; it is not allowed to use a shearing machine to cut quenched steel, high-speed steel, alloy tool steel, cast iron, and brittle materials. The main specification of shearing machine calibration is t*B, where t is the calibrated maximum allowable cutting material thickness, B is the calibrated maximum allowable cutting width. The selected shearing machine cannot be used to process workpieces that exceed the width B and the maximum allowable sheet thickness t.

But when shearing higher strength (such as spring steel, high alloy steel plate), you should also check the maximum allowable sheet thickness t_max. This is when the shearing machine is designed, it is generally considered to cut medium-hard materials (25-30 steel with a tensile strength of about 500MPa). Therefore, the tensile strength of the material being sheared σb>500Mpa, the maximum allowable shearing thickness t_max can be calculated as follows:

tmax =√(500/σb t)

t——Maximum allowable shearing thickness, mm;

σb——The tensile strength of the material to be cut, MPa;

T_max——Maximum allowable shearing thickness, mm.

Through formula, if the maximum allowable thickness of the sheet material to be cut is smaller than the thickness of the material to be cut, it can be used on this shearing machine. The following table shows the technical specifications and models of the shearing machine.

Parameter	Q11-1*1000	QY11-4*2000	Q11-4*2500	Q11-12*2000	Q11Y-16*2500
Thickness of cutting sheet/mm	1	4	4	12	16
Width of cutting sheet/mm	1000	2000	2500	2000	2500
Cutting angle	1°	2°	1°30’	2°	1°-4°
Number of strokes/(time/min)	65	22	45	30	8-12
Back gauge distance	500	25-500	650	750	900
Power/KW	0.6	6.5	7.5	13	22
Structure type	Mechanical transmission	Hydraulic transmission	Mechanical transmission	Mechanical transmission	Hydraulic transmission

• When cutting long sheets, there should be an auxiliary support; when cutting large and heavy sheets, in order to facilitate feeding and reduce the friction on the surface of the material to be cut, there should be a rolling support (that is, the support should be equipped with a steel ball support material , The structure is shown in the picture). Lifting devices and sufficient auxiliary workers should be provided for lifting the plates, and coordination should be ensured when cooperating with the auxiliary workers.