The main transmission structure of the CNC right-angle shearing machine mainly includes four types: hydraulic type, clutch-type, single-point servo ball head type, and four-point servo drive type. The hydraulic structure needs to be equipped with a hydraulic oil cooling system. The leakage of hydraulic oil and waste oil treatment will cause certain environmental pollution. In addition, the oil pump in the hydraulic station works continuously, which will generate a lot of heat energy loss. The shearing machine does not cut. It also consumes electricity at times, resulting in a lot of energy consumption. The clutch-type structure motor is always in working condition, and the energy consumption is high. In addition, the cutting stroke of the shearing machine needs to be adjusted on site. The adjustment method is a mechanical adjustment, the adjustment speed is slow, and the accuracy is not easy to be guaranteed.

Common main transmission structure

The main transmission structure of the CNC right-angle shearing machine mainly includes four types: hydraulic type, clutch-type, single-point servo ball head type, and four-point servo drive type. The hydraulic structure needs to be equipped with a hydraulic oil cooling system. The leakage of hydraulic oil and waste oil treatment will cause certain environmental pollution. In addition, the oil pump in the hydraulic station works continuously, which will generate a lot of heat energy loss. The shearing machine does not cut It also consumes electricity at times, resulting in a lot of energy consumption. The clutch-type structure motor is always in working condition, and the energy consumption is high. In addition, the cutting stroke of the shearing machine needs to be adjusted on-site. The adjustment method is a mechanical adjustment, the adjustment speed is slow, and the accuracy is not easy to be guaranteed.

The single-point servo ball head servo motor drives the ball screw to directly drive the upper tool post to realize the shearing of the sheet material. This structure is relatively compact, eliminates the need for intermediate transfer links, and can complete more efficient and energy-saving cutting work. However, the tool holder will generate large lateral forces in two directions during shearing, and the tool holder has the risk of turning over. This single-point ball head structure cannot overcome this drawback. All lateral forces are generated by the tool holder. The rear upright guide rail bears, when the tool post cuts sheets of different thickness or different strength, different lateral forces will be generated, and the guide rail will also deform to different degrees, which will affect the cutting accuracy in both directions. In order to avoid excessive lateral force, the maximum cutting length of the machine tool with this structure will be limited.

The four-point servo-driven structure is driven by four-point dual-servo motors. It has the characteristics of adjustable stroke, anti-eccentric load, and energy saving. Compared with other main transmission structures, it has obvious advantages. This article uses the main transmission method of right-angle shears as the research object, analyzes, and explains the precautions in the design process.

Structure composition and principle

The four-point servo-driven right-angle shearing machine is mainly composed of a frame, an upper knife holder, a lower knife holder, a driving device, a pressing device, a lubrication system, and a cooling system. Two sets of shear blades installed at right angles are installed in parallel on the upper and lower sides. On the X-axis and Y-axis of the tool post, the plate can be cut at right angles in the horizontal plane.

The transmission mechanism of the right-angle shearing machine is composed of a servo motor, a ball screw, a wedge block, etc., as shown in Figure 1. The servo motor drives the lead screw to rotate through the coupling, the lead screw pushes the wedge block to move to the right, and the lower surface of the wedge block presses the upper knife holder to push the upper knife holder to move downward, and then drives the upper blade to cut the plate. In order to ensure that the upper tool post can effectively resist the shearing force in the X/Y directions during the shearing movement, two sets of transmission mechanisms are set up. The two sets of transmission mechanisms drive the inclined wedge to contact the rollers of the upper tool post. When the right-angle shearing machine performs the cutting action, the left and right oblique wedges on the two sets of transmission mechanisms jointly push the upper knife post to move downward to complete the cutting action.

The anti-eccentric load principle of the four-point servo-driven right-angle shearing machine is: the moment the upper tool post cuts the sheet, the two sets of driving devices are synchronously controlled by the servo motors, and the synchronous driving device is extremely rigid. Pushing the upper tool post balances the turning tendency caused by the shearing force at any point so that the upper tool post can make the knife deformation very small under the action of the shearing force, thereby ensuring the cutting quality.

Rail assembly analysis

The upper blade of the four-point servo-driven right-angle shearing machine is located in the middle of the frame. The four-sided guide assembly is difficult and costly. Therefore, the upper blade holder in the industry mostly adopts double-sided guidance. The two guide assembly surfaces are perpendicular to each other. There are two ways to assemble the guide rails: near the blade and away from the blade, as shown in Figure 2.

In Fig. 2, the upper tool holder and the ram are connected by screws, and the guide rail and the frame are connected by screws. During the process of cutting the sheet, the reaction force of the sheet on the upper blade is horizontal in addition to the vertical shearing force. Directional thrust, which is generated by the upper and lower blades pressing the sheet.

When the guide rail is close to the blade assembly, the force is transmitted to the frame through the nearby ram, and the rigidity of the frame restricts the knife yield during the shearing process. The advantage is that the deformation of the upper knife frame has little effect, and the disadvantage is that the bearing capacity of the ram is uneven. The bearing capacity of the ram near the force is large, and the guide rail fastening screw shows a tendency to stretch under the force. The guide rail is easy to slip when the thick plate is sheared and deviates from the initial assembly position.

When the guide rail is far away from the blade assembly, the force is transmitted to the rack through the upper tool holder. Due to the coordinated deformation of the upper tool holder, the bearing capacity of each ram is uniform, and the guide rail fastening screws are not affected by the force and will not deviate from the initial assembly position. Disadvantages In the process of force transmission, the upper tool holder produces a certain deformation. When cutting materials with different thicknesses, the adjustment of the blade gap should comprehensively consider the influence of the deformation of the upper tool holder.

Analysis of the effect of the pressure cylinder

The shear section of the sheet metal is divided into four areas, namely the collapse area, the smooth area, the crack area, and the burr area. The smooth area is plastic deformation under extrusion stress, and the other three section areas are plastic under tensile stress. Deformation. In the extrusion stage, due to the limited constraints of the upper and lower blades, the sheet does not slip. In the stretching stage, the sheet is stretched and slips. In engineering, the pressing method is often used to limit the sheet slip.

In the actual shearing machine design, the pressing force design is much smaller than the calculated value of the empirical calculation formula. For example, 40 sets of cylinders with a cylinder diameter of 25mm are selected for the pressing material, and the working pressure is 0.6MPa. The maximum theoretical output force that the cylinder can provide is 9080N. When cutting a stainless steel plate with a size of 2500mm×1500mm×4mm, the pressing force calculated by the empirical formula is 87529N. The actual design value is much smaller than the theoretical calculation value, indicating that the shearing cylinder is not used to limit the slippage of the plate. Instead, it is used to limit the uplift of the sheet during the shearing process, and to prevent the upper blade from lifting the sheet during the return stroke. The sheet slip is mainly limited by the clamp, but in the area away from the clamp, the rigidity of the sheet is relatively high. Weak, this restriction will be insignificant, so the shear accuracy will be worse.

The blanking angle is too close to the blade, and the holding force provided by the holding force provides a small anti-uplifting moment. When cutting thick plates, the holding cylinder has insufficient holding up ability; the blanking angle is too far away from the blade, and the upper blade returns with the material when cutting thin plates. Frequently, the sheet waste is too wide and the sheet utilization rate is low.

Shearing machine accuracy guarantee measures

The cutting quality defects of sheet material mainly include sag, burr, poor parallelism of opposite sides, poor perpendicularity of adjacent sides, etc., which are related to blade gap, upper and lower blade parallelism, and sheet and blade perpendicularity.

Too small shear blade gap will increase the shear force, and at the same time increase the friction between the cutting edge and the edge of the plate, and accelerate the wear of the cutting edge. If the gap is too large, the steel plate of plastic material will produce burrs, and the fracture of the steel plate of brittle material will be rough. The value of the gap is related to the thickness of the steel plate and the mechanical properties of the steel plate. At present, the shears are mostly equipped with automatic gap adjustment devices.

The difference in the parallelism of the upper and lower blades will cause the blade gap to change during the operation of the upper blade, and the verticality of the upper blade will also change accordingly. During the cutting process, there will be defects such as edge collapse, burrs, material pulling, and blade stripping; The change of the perpendicularity to the blade, in addition to the blade itself, the deformation of the plate itself will also affect it.

Double servo motor synchronous control

The four-point servo-driven shearing machine adopts double servo drive and semi-closed loop control mode. The motor adopts synchronous control. The gantry synchronous axis is connected to the NC CNC system for unified control. The master and slave motors are simultaneously controlled by the NCU (Numerical Control System Control Unit). Position control. In the idle stroke, the synchronization of the dual servo motors is very good, but during the cutting process, the synchronization accuracy of the dual servo motors fluctuates at a certain moment. The non-synchronization of the dual motors causes the upper tool post and upper blade to tilt, and then Affect processing accuracy. By controlling the allowable fluctuation range of the phase difference of the dual motors, the upper tool post is controlled to run smoothly, thereby ensuring the parallelism of the upper and lower blades.

The inclined wedge is matched with the roller of the upper tool post

During the assembly process, the fit of the inclined wedge and the upper tool holder may not be very close, and there are several factors in this.

⑴ Assembly error. During the assembly process, the diagonal wedge must fit well with the roller of the upper tool post, and the contact force should be uniform. If the force applied by the individual wedges to the upper tool post is too large, the wedge and the roller will appear during operation. gap.

⑵ Manufacturing error. There is an error in the angle of the wedge assembled on the driving device, which is the main reason for the dynamic gap between the wedge and the roller during operation.

⑶ Assembly stress. If the double drive mechanism is connected to the upper tool post in an unreasonable way, or the synchronous motor is not properly cleared before powering on, there will be stress between the double drive mechanism and the upper tool post. In the idling operation, there will be only one drive The mechanism provides the main power. After a long time, there will be a gap between the other set of wedges and the upper tool post.

There is a gap between the oblique wedge and the roller of the upper tool post. The effect on the machining accuracy is similar to that of the servo motor synchronization error. During the cutting process, the height difference between the left and right sides of the upper tool post will fluctuate, which will affect the blade gap. This situation is also easy to cause shocks during operation, causing noise and damage to key parts. Therefore, in the actual assembly process, it is necessary to dynamically monitor the gap between the wedge and the roller at different time periods.

Sheet sagging

When the right-angle shearing machine cuts large workpieces, such as workpieces larger than 300mm in both X/Y directions, the rigidity of the plate is poor when it is laid flat. Before the cutting starts, the plate sags due to gravity and is far from the plate in the clamped area Due to the deviation of the deformation from the set position, the cutting quality of the adjacent edges of the plate, and the parallelism of the opposite edges will deteriorate. The simplest measure is to design a set of supporting mechanisms to limit the sagging of the sheet. Figure 3 shows the most commonly used supporting principle diagram of the shearing machine. The cylinder uses the principle of the lever to push the other end of the supporting roller to move up in a circular motion, saving assembly space.

This article elaborates on the characteristics of the existing right-angle shearing machine. Taking the four-point servo-driven right-angle shears as the object, the structure, composition, and working principle are explained. The guiding method of the upper tool post and the pressing cylinder The effect is analyzed; the influence of motor synchronization, transmission mechanism assembly, and sheet material sagging on the accuracy of the right-angle shears is analyzed, and corresponding guarantee measures are given to provide guidance and suggestions for the design of the right-angle shearing machine.