JP6822216B2 - Cutting method and cutting device - Google Patents

Description

The present invention relates to a cutting method and a cutting device, and more particularly to a cutting method and a cutting device capable of cutting a metal member by heat using a plasma arc or the like while using a refrigerant such as water.

For cutting a plate-shaped metal member, a cutting method using heat such as plasma cutting may be used. As described in Patent Document 1, plasma cutting is usually performed in the atmosphere, but in some cases, a cutting pool or the like is provided, a metal member is placed in water, and underwater plasma cutting is performed.

Japanese Unexamined Patent Publication No. 5-23859

There is a demand for cutting metal members having surfaces facing each other, such as a U-shaped cross section, by using heat such as plasma cutting. At this time, as shown in FIG. 9, if the metal member 90 is cut in the atmosphere, the influence of heat generated by the plasma arc A emitted from the plasma cutting torch 10 when the one facing surface 91 is cut is affected. , May extend to the other surface 92. Further, the metal material M1 melted down at the time of cutting from one surface 91 is ejected toward the other surface 92 and adheres to the other surface 92, so that the deposit M2 is likely to be formed. As described above, due to the influence of the heat of the plasma arc A, the surface 92 may be affected by melting off, dripping, and the like.

On the other hand, if the metal member is submerged in water for cutting, the smoothness of the cut surface is lowered due to the influence of water, and the cut surface is likely to be roughened. Further, since the portion that has been cut by applying heat is rapidly cooled by water, the hardness of the portion tends to increase.

The problem to be solved by the present invention is that when cutting a metal member having surfaces facing each other by using heat while using a liquid refrigerant such as water, when cutting one surface, It is an object of the present invention to provide a cutting method in which the other surface facing the other surface is less likely to be affected and the liquid refrigerant is less likely to affect the cut portion, and such a cutting device.

In order to solve the above problems, the cutting method according to the present invention uses a cutting means for applying heat to a part of a plate-shaped metal material and cutting the metal material in the part of the metal material. In a cutting method for cutting an object to be cut, which comprises a first plate-shaped portion and a second plate-shaped portion separated from the first plate-shaped portion and facing the first plate-shaped portion. Of the first plate-shaped portion and the second plate-shaped portion, one is a target portion and the other is a standby portion, the standby portion is arranged in the liquid refrigerant, and the target portion is outside the liquid refrigerant. The target portion is cut while being arranged in the above.

Here, the cutting means may be a plasma cutting torch. In this case, the plasma cutting torch may use oxygen as an operating gas.

The surface of the target portion facing the standby portion may be arranged so as not to come into contact with the liquid refrigerant.

It is preferable to cut the object to be cut while moving the cutting means with respect to the object to be cut while the object to be cut is fixed.

The cutting means is a plasma cutting torch, and cuts the target portion while moving the cutting means along the surface of the target portion, starting from the starting end edge which is one part of the end edge of the target portion. At that time, the cutting means is arranged outside the starting edge, the cutting means is moved toward the starting edge in a state where a plasma arc is emitted from the cutting means, and the cutting means and the object to be cut are used. When the value of the current flowing between the torches begins to increase, the moving speed of the cutting means may be increased.

The cutting means is a plasma cutting torch, and while moving the cutting means along the surface of the target portion, the target portion is cut with the end edge, which is one part of the end edge of the target portion, as an end point. When the current value flowing between the cutting means and the object to be cut begins to decrease after the cutting by the cutting means reaches the end edge, the cutting means before the current value becomes zero. It is advisable to stop the emission of plasma arcs from.

When the target portion is cut by the cutting means, the energy density of heat given to the object to be cut by the cutting means and the cutting means are described so that the smoothness of the target portion and the standby portion is increased. It is preferable to adjust at least one of the moving speed of the cutting means when cutting the object to be cut while moving the object to be cut.

The first step of cutting the first plate-shaped portion and the second plate-shaped portion using the first plate-shaped portion as the target portion and the second plate-shaped portion as the standby portion. Is used as the target portion, and the first plate-shaped portion is used as the standby portion, and after performing one of the second steps of cutting the second plate-shaped portion, the cut is performed. It is advisable to change the arrangement of objects and perform the other process.

It is preferable to use a plurality of the cutting means to simultaneously cut a plurality of objects to be cut held by the common holding means.

The object to be cut is a pair of metal members having a first plate-shaped portion and a second plate-shaped portion in a bending portion formed by bending a plate material into a U-shaped cross section, and the cutting means is used. After cutting the surplus at the edge of the bent portion of the pair of metal members, the pair of metal members may be abutted against each other and fixed at the edge.

The cutting device according to the present invention includes the cutting means, a holding means for holding the object to be cut at a position where the object to be cut can be cut by the cutting means, and a liquid storage means for storing the liquid refrigerant. The above-mentioned cutting method is executed.

Here, the cutting device has a transport means in the liquid storage means, and the transport means is separated into the liquid refrigerant when the object to be cut is cut by the cutting means. It is preferable that the cut pieces are transported to the outside of the liquid storage means.

In the cutting method according to the above invention, when cutting the target portion selected from the first plate-shaped portion and the second plate-shaped portion, the standby portion which is the other plate-shaped portion facing the target portion is used. While arranging it in a liquid refrigerant such as water, the target portion is arranged outside the liquid refrigerant. Since the standby portion is arranged in the liquid refrigerant, even if heat is applied to the target portion when the target portion is cut, the cooling effect of the liquid refrigerant makes it difficult for the heat to affect the standby portion. Further, the metal material melted down when the target portion is cut is cooled by the liquid refrigerant and solidified, so that it does not easily adhere to the standby portion. In this way, the influence caused by the cutting of the target portion on the standby portion is suppressed by the presence of the liquid refrigerant. Further, by performing cutting while cooling the object to be cut using a liquid refrigerant, it is possible to obtain an effect of suppressing deformation of the object to be cut due to the influence of heat given by the cutting means.

On the other hand, since the target portion is cut while it is outside the liquid refrigerant, the smoothness of the cut surface decreases due to contact with the liquid refrigerant, and the hardness of the cut portion increases due to quenching after cutting. Is avoided. In this way, the liquid refrigerant is less likely to affect the cut portion of the target portion.

Here, when the cutting means is a plasma cutting torch, it is possible to cut the plate-shaped portion at high speed and with high accuracy by using relatively simple equipment. In plasma cutting, when the target portion is cut, the metal material melted by the injection of the plasma arc is ejected to the back side of the target portion, so that the standby portion is likely to be affected. By arranging the plasma in the liquid refrigerant, such an effect can be effectively reduced.

In this case, if the plasma cutting torch uses oxygen as the operating gas, a material made of various metal materials can be applied as the object to be cut, and cutting is achieved even when the plate thickness is large. can do. In addition, by using oxygen as the operating gas, the injection of the metal material melted by the plasma arc occurs particularly strongly, but by arranging the standby part in the liquid refrigerant, the effect on the standby part is sufficient. Can be reduced to.

When the surface of the target portion facing the standby portion is arranged so as not to come into contact with the liquid refrigerant, it is particularly effective to prevent the liquid refrigerant from affecting the cut portion in the target portion. can do.

When cutting the object to be cut while moving the cutting means with respect to the object to be cut while the object to be cut is fixed, the object to be cut is large or the cutting shape is complicated. Also, it is easy to cut.

The cutting means is a plasma cutting torch, and when cutting the target portion while moving the cutting means along the surface of the target portion starting from the starting end edge which is one part of the end edge of the target portion, the starting end is used. With the cutting means placed on the outside of the edge and the plasma arc emitted from the cutting means, the cutting means is moved toward the starting edge, and when the current value flowing between the cutting means and the object to be cut begins to rise, cutting is performed. When increasing the moving speed of the means, cutting can be performed under stable conditions from the beginning of cutting at the starting edge. In addition, it is easy to protect the electrodes of the plasma cutting torch from unnecessary wear.

The cutting means is a plasma cutting torch, which cuts when cutting the target portion with the end edge, which is one part of the end edge of the target portion, as the end point while moving the cutting means along the surface of the target portion. When the current value flowing between the cutting means and the object to be cut begins to decrease after the cutting by the means reaches the end edge, the emission of the plasma arc from the cutting means is stopped before the current value becomes zero. The cutting can be performed under stable conditions until the cutting is completed at the terminal edge.

When cutting the target portion by the cutting means, the energy density of the heat given to the object to be cut by the cutting means and the cutting means are moved with respect to the object to be cut so that the smoothness of the target portion and the standby portion is improved. However, when at least one of the moving speed of the cutting means when cutting the object to be cut is adjusted, the smoothness of the target portion and the standby portion decreases due to the influence of the cutting, and the object to be cut after cutting. It is easy to avoid affecting the quality of.

The first step of cutting the first plate-shaped portion and the second plate-shaped portion as the target portion, with the first plate-shaped portion as the target portion and the second plate-shaped portion as the standby portion. Of the second step of cutting the second plate-shaped portion with one plate-shaped portion as the standby portion, after performing one step, the arrangement of the object to be cut is changed and the other step is performed. When doing so, both the first plate-shaped portion and the second plate-shaped portion can be cut by using a common cutting means, so that the first plate-shaped portion and the second plate-shaped portion in the object to be cut can be cut. It is possible to easily perform a process of cutting both of the plate-shaped portions of the above into a desired shape.

When a plurality of cutting means are used to simultaneously cut a plurality of objects to be cut held by a common holding means, it is possible to efficiently cut a plurality of individuals to be cut at the same time. Cutting can be performed on a large number of individuals.

The object to be cut is a pair of metal members having a first plate-shaped portion and a second plate-shaped portion in a bent portion formed by bending a plate material into a U-shaped cross section, and a pair of metal members are formed by cutting means. If a pair of metal members are abutted against each other and fixed at the edge of the bending portion of the metal member after cutting the surplus wall, the remainder at the edge of the bending portion is fixed. The meat can be cut in a state where the influence on the first plate-shaped portion and the second plate-shaped portion is small. By abutting the pair of metal members having high-quality end edges thus obtained against each other and fixing them by welding or the like, the accuracy of abutting and fixing can be improved. A typical example of a product manufactured through a process of cutting a pair of metal members with surplus meat, abutting them, and fixing them by welding is an axle housing for accommodating a vehicle differential gear. ..

When the cutting device according to the above invention is used, the object to be cut having the first plate-shaped portion and the second plate-shaped portion facing each other is held by the holding means, and the first plate-shaped portion and the second plate-shaped portion are held. The standby portion selected from the plate-shaped portion of the above is arranged in the liquid refrigerant stored in the liquid storage means, while the opposing target portion is arranged outside the liquid refrigerant, and the target portion is used by the cutting means. Can be cut. As a result, it is possible to suppress the influence of heat at the time of cutting on the standby part, and to prevent the contact between the target part and the liquid refrigerant from affecting the cut part of the target part. ..

Here, the cutting device has a transporting means in the liquid storage means, and when the transporting means cuts the object to be cut by the cutting means, the cut pieces separated into the liquid refrigerant are stored in the liquid. When transporting to the outside of the means, avoiding the accumulation of unnecessary cutting pieces separated by cutting in the liquid storage means, cutting a large number of objects to be cut continuously and efficiently. Can be carried out.

It is a figure explaining the structure of the cutting apparatus which concerns on one Embodiment of this invention, (a) is a front view, (b) is a side view. It is a figure which shows the state which held the pair of axle housing main body material by the holding jig in the said cutting apparatus, (a) is a perspective view, (b) is a plan view. It is a figure explaining the cutting method which concerns on one Embodiment of this invention, and is the side view which shows the state in the vicinity of the part where cutting is performed. It is a figure explaining the cutting method, (a) shows the state before cutting, and (b) shows the state after cutting. It is a figure which shows the state which a pair of main body materials are cut at the same time. It is a figure explaining each parameter measured as an index of deformation in an Example. It is a figure explaining the evaluation of the smoothness of the upper surface and the lower surface in an Example. It is a figure which shows the relationship between the energy density and cutting speed, and the quality of cutting conditions. It is a figure explaining plasma cutting in the atmosphere.

Hereinafter, the cutting method and the cutting apparatus according to the embodiment of the present invention will be described in detail with reference to the drawings.

[Example of object to be cut]
First, the cutting method according to the embodiment of the present invention and the object to be cut (work) in the cutting device will be described.

The work to be cut is made of a metal material, and has a first plate-shaped portion and a second plate-shaped portion as a portion having a plate-shaped structure. The first plate-shaped portion and the second plate-shaped portion are separated from each other and face each other. The first plate-shaped portion and the second plate-shaped portion may face each other with their surfaces substantially parallel to each other, or may have an angle between the mutual surfaces, one of which (for example, the first plate-shaped portion). When the surface of the plate-shaped portion) is arranged substantially horizontally, the surface of the other (second plate-shaped portion) exists below the portion where the surface (first plate-shaped portion) is scheduled to be cut. Anything that does.

The first plate-shaped portion and the second plate-shaped portion may be connected in any way as long as they are separated from each other. For example, a form in which the first plate-shaped portion and the second plate-shaped portion are connected at each other's edge, that is, a form in which the work has a U-shaped (U-shaped) cross section can be mentioned.

As an example of a suitable work, a main body material which is a metal member constituting the axle housing can be mentioned. The axle housing is assembled to the rear axle of a large vehicle such as a truck and accommodates the axle and differential gears. The main body portion of the axle housing is made of a pair of main body materials 90, 90 having substantially symmetrical shapes as shown in FIG. 5 and the like.

The pair of body members 90 each have a body portion 90a and tubular portions 90b and 90b formed integrally. The body portion 90a is formed by bending a steel plate into a semi-cylindrical shape (substantially U-shaped in cross section) and bulging in a substantially semicircular ring shape. The tubular portions 90b and 90b are integrally formed at both ends of the body portion 90a, and the steel plate is bent into a semi-cylindrical shape in the same manner as the body portion 90a, and is based on a half-width tubular shape. Here, the vertically opposed upper surface 91 and lower surface 92 constituting the body portion 90a and the tubular portions 90b, 90b serve as the first plate-shaped portion and the second plate-shaped portion at the time of cutting.

Each pair of main body materials 90 can be manufactured by bending a steel plate by press molding. Then, the surplus wall is cut from the longitudinal end edges 91a and 92a of the upper surface 91 and the lower surface 92, which are the edge edges of the bent portion, by the cutting method according to the embodiment of the present invention. Then, in the new longitudinal edge edges 91d and 92d obtained by cutting, the pair of main body members 90 and 90 are butted against each other, and the butted portions are welded to fix each other. In this way, the main body portion of the axle housing having a substantially annular body portion and a substantially square tubular tubular portion is manufactured. Further, the axle housing as a product can be completed by attaching accessory parts and the like.

[Configuration of cutting device]
Next, the cutting device according to the embodiment of the present invention will be described with reference to FIGS. 1 and 2.

FIG. 1 shows an outline of a cutting device 1 according to an embodiment of the present invention. The cutting device 1 includes a plasma cutting torch 10 as a cutting means, a numerical control (NC) device 20 as a driving means, a holding jig 30 as a holding means, a water tank 40 as a liquid storage means, and a conveying means. Conveyor 50 and.

The plasma cutting torch 10 emits a plasma arc A and can cut a plate-shaped metal material by the heat of the plasma arc A. Preferably, oxygen is used as an operating gas so that it can be applied to various metal materials and even a thick metal material having a plate thickness of more than 10 mm can be cut at high speed. When oxygen is used as the operating gas, the operating gas may be composed of oxygen alone or a mixed gas containing oxygen as a main component. Further, air or the like may be used as an assist gas as appropriate. The cutting device 1 according to the present embodiment includes two plasma cutting torches 10.

The NC device 20 holds each of the two plasma cutting torches 10 and gives the motion D1 to the plasma above the cutting target surface of the work (here, the axle housing main body material 90) and along the cutting target surface. Move the cutting torch 10. Cutting of the workpiece into a desired shape can be achieved according to numerical control by a control unit (not shown).

The holding jig 30 holds the work and holds the work at a position where it can be cut by the plasma cutting torch 10. Here, as shown in FIG. 2 and the like, the holding jig 30 can hold two axle housing main body members 90 and 90 as workpieces at the same time in a substantially mirror-symmetrical arrangement. The work may be held by any method, but a gripper (not shown) is used to sandwich both ends of the main body material 90 in the longitudinal direction between the holding jig 30 and the gripper, and an air cylinder is appropriately used. By pressing the gripping tool against the holding jig 30 using an or the like, the main body material 90 can be firmly held.

Further, the holding jig 30 can change the arrangement of the held main body material 90. That is, the motion D2 for rotating the central axis 31 by 180 ° can be performed while holding the main body material 90, and the upper surface 91 (first plate-shaped portion) is directed upward and opposed to the plasma cutting torch 10. A transition can be made between the first arrangement and the second arrangement with the opposite lower surface 92 (second plate-shaped portion) facing upwards and facing the plasma cutting torch 10. The holding jig 30 can perform exercises other than changing the arrangement of the main body material 90. For example, the position of the main body material 90 in the water tank 40 can be adjusted, or the main body material 90 to be cut can be replaced. It is possible to do.

The water tank 40 can store water W as a liquid refrigerant. While cutting with the plasma cutting torch 10, as shown in FIGS. 1 and 3, one surface (standby portion) of the upper surface 91 and the lower surface 92 of the main body material 90 is arranged in the water W. However, the other surface (target portion) is maintained so as to be arranged outside the water W.

In the conveyor 50, the transport surface 51 is arranged in water along the bottom surface of the water tank 40. Then, the transport surface 51 gets over the side wall 41 of the water tank 40 and extends to the outside of the water tank 40. The cut piece 95 cut and separated by the plasma cutting torch 10 is separated into water from the main body material 90, settles, and rides on the transport surface 51 of the conveyor 50. By driving the motion D3 that directs the transport surface 51 of the conveyor 50 from the inside of the water tank 40 to the outside, the cut pieces 95 can be transported from the inside of the water tank 40 to the outside and discharged to the outside of the water tank.

[Cut method]
Next, the cutting method according to the embodiment of the present invention will be described with reference to FIGS. 1 to 5. Here, the case where the body material 90 of the axle housing is used as the work to be cut and the surplus wall of the longitudinal end edges 91a and 92a is cut by using the cutting device 1 described above will be dealt with.

First, the holding jig 30 holds the pair of main body materials 90, 90 in a substantially mirror-symmetrical arrangement. Further, water W is stored in the water tank 40. Then, each main body material 90 held by the holding jig 30 is arranged in the water tank 40. At the time of arrangement, the upper surface 91 (first plate-shaped portion) and the lower surface 92 (second plate-shaped portion) of the main body material 90 are kept substantially horizontal.

At this time, as shown in detail in FIG. 3, of the upper surface 91 and the lower surface 92 of each main body material 90, the surface (target portion; in this case, the upper surface 91) where the surplus meat is cut first is placed in the water tank 40. It is arranged outside the stored water W, that is, above the water surface W1. On the other hand, of the upper surface 91 and the lower surface 92, the surface (standby portion; in this case, the lower surface 92) on which the surplus meat is not cut first is in the water W stored in the water tank 40, that is, below the water surface W1. Place it in. In this way, only a part of the area along the vertical direction of the main body material 90 is arranged in water. It is preferable that the inner side surface 91b of the upper surface 91, that is, the surface facing the lower surface 92 is also arranged above the water surface W1 so as not to come into contact with the water W.

With the main body material 90 arranged and fixed in this way, the surplus thickness of the upper surface 91 is cut using the plasma cutting torch 10. As shown in FIG. 4A, cutting is executed by performing motion D1 of the plasma cutting torch 10 by the NC device 20 along a path determined according to a virtual line to be cut in the main body material 90. .. Here, the imaginary line to be cut intersects the longitudinal end edge 91a, which is the edge of the main body 90 along the longitudinal direction, from one end to the other end, that is, the longitudinal end edge 91a. A continuous line is set along the longitudinal edge 91a from the start edge 93, which is one of the opposite edge edges, to the end edge 94, which is the other edge, at a position slightly inside the portion where the surplus thickness to be cut exists. Will be done. By cutting along such a virtual line, the cut piece 95 including the surplus portion is separated from the main body material 90 as shown in FIG. 4 (b). Further, by cutting, a new longitudinal edge 91d is formed inside the original longitudinal edge 91a, and the cut surface 91c is exposed. In the present embodiment, as shown in FIG. 5, the two NC devices 20 and 20 simultaneously operate and move the two plasma cutting torches 10 and 10, and the pair of main body materials 90 and 90 are operated and moved at the same time. Cut at the same time.

Generally, when cutting a metal material using a plasma cutting torch, a pilot arc having a smaller output than the main arc may be used before the main arc used for cutting the material is generated. In the present embodiment, the pilot arc is emitted from the plasma cutting torch 10 in a state where the plasma cutting torch 10 is arranged outside the main body material 90 from the starting edge 93. From this state, when the plasma cutting torch 10 is moved toward the start edge 93 by the NC device 20, the plasma arc A starts at a position approaching the start edge 93 to some extent, for example, a position about 5 mm outside the start edge 93. Start bending towards edge 93. Along with this, a main arc is generated between the electrode of the plasma cutting torch 10 and the metal material of the main body material 90, and the current value flowing between the two starts to increase. As soon as this increase in the current value is detected, the moving speed of the plasma cutting torch 10 by the NC device 20 along the upper surface 91 of the main body material 90 is controlled to be increased.

In this way, from the state where the moving speed of the plasma cutting torch 10 is increased at the start of cutting, the plasma cutting torch 10 is continuously moved by the NC device 20 along the longitudinal edge 91a of the upper surface 91 of the main body material 90. It is moved at a position inside the longitudinal edge 91a to continuously cut the surplus portion. Finally, the cut reaches the end edge 94 of the top surface 91. Further, by moving the plasma cutting torch 10 from the end edge 94 to the outside of the main body material 90, the main body material 90 is cut through, and the cut piece 95 including the surplus portion is separated from the main body material 90. In the present embodiment, the state in which the plasma arc A is emitted from the plasma cutting torch 10 is maintained even at the moment when the cutting reaches the terminal edge 94 and cuts through the terminal edge 94. After that, the current value flowing between the plasma cutting torch 10 and the main body material 90 begins to decrease with the cut-out. If left as it is, the generation of plasma arc A will eventually stop and the current value will reach zero. However, in this embodiment, instead of leaving the plasma to zero until the current value becomes zero, when the current value begins to decrease, the plasma cutting torch 10 is forcibly released before the current value becomes completely zero. Control is performed to stop the emission of the plasma arc A and end the operation of the plasma cutting torch 10.

At the time of cutting, the strength of the plasma arc A emitted from the plasma cutting torch 10, that is, the energy density of the heat given to the main body material 90 by the plasma arc A, and the plasma cutting torch 10 are moved along the upper surface 91 by the NC device 20. By changing the moving speed (cutting speed), the cutting conditions are changed, which affects the quality of the upper surface 91 and the lower surface 92 obtained after cutting. Therefore, at least one of these parameters may be adjusted so that the smoothness of the upper surface 91 and the lower surface 92 becomes high. Preferably, both parameters may be adjusted under such guidance. In particular, proper selection of the moving speed of the plasma cutting torch 10 has a high effect on improving the smoothness of the upper surface 91 and the lower surface 92. Here, the state in which the upper surface 91 has high smoothness means that the upper surface 91 is roughened due to contact with the cut portion of the water W, or the metal material melted at the time of cutting the upper surface 91 is the inner surface 91b of the upper surface 91. Refers to a state in which there are few uneven structures on the upper surface 91, such as protrusions and dross-like deposits M2 generated by adhering to. A state in which the lower surface 92 has high smoothness means that the lower surface 92 is roughened due to the influence of heat or the like, or a protrusion-like or dross-like deposit formed by the metal material melted down from the upper surface 91 adhering to the inner surface 92b of the lower surface 92. It refers to a state in which there are few uneven structures on the lower surface 92 such as M2. The values set as the above two parameters may be kept constant during cutting of one main body material 90, or may be appropriately changed during cutting. The energy density of the plasma arc A can be changed, for example, by adjusting the supply amount of the operating gas.

When the cutting from the start end edge 93 to the end edge 94 is completed, the cut piece 95 including the surplus portion separated from the main body material 90 settles in the water tank 40. When the settled cut pieces 95 reach the transport surface 51 of the conveyor 50 at the bottom of the water tank 40 and get on the transport surface 51, the cut pieces 95 are transported by the motion D3 of the conveyor 50 and discharged to the outside of the water tank 40. .. In addition, this discharge step may be performed every time the cutting of the upper surface 91 and the lower surface 92 of the main body material 90 is completed, or may be performed after the cutting of both the upper surface 91 and the lower surface 92 is completed. Further, after the cutting of the plurality of pairs of the main body materials 90 is completed, they may be collectively performed as appropriate.

When the cutting of the main body material 90 with respect to the upper surface 91 is completed, the holding jig 30 inverts the main body material 90 by 180 ° by the motion D2 about the central axis 31. Then, the lower surface 92 is arranged as a target portion outside the water W stored in the water tank 40, that is, above the water surface W1. Further, the upper surface 91 is arranged as a standby portion in the water W stored in the water tank 40, that is, below the water surface W1. As in the case where the upper surface 91 is the target portion, the inner side surface 92b of the lower surface 92 is preferably arranged above the water surface W1 so as not to come into contact with the water W. As shown in FIGS. 2 and 5, when the pair of main body members 90 and 90 are symmetrically held by the common holding jig 30 and the 180 ° arrangement is reversed around the central axis 31, the upper surface 91 The left and right positions of the pair of main body members 90 and 90 with respect to the central axis 31 are exchanged between the time of cutting and the time of cutting the lower surface 92.

Then, in the same manner as the cutting is performed on the upper surface 91, the lower surface 92 is cut along the longitudinal end edge 92a from the start end edge 93 to the end edge 94 by using the plasma cutting torch 10. Along with obtaining a new longitudinal edge 92d, the cut piece 95 including the surplus portion is cut off.

When the cutting of the upper surface 91 and the lower surface 92 is completed, the pair of main body members 90, 90 is removed from the holding jig 30. The removed pair of main body members 90, 90 are then abutted against each other at the new longitudinal edge 91d, 92d of the upper surface 91 and the lower surface 92 from which the surplus portion has been removed. Then, they are fixed to each other by being welded at the abutting portion.

The holding jig 30 after removing the pair of main body materials 90, 90 that has been cut can appropriately hold another pair of main body materials 90, 90 to be cut next. Then, by repeating the above-mentioned cutting process, it is possible to continuously cut a plurality of pairs of main body materials 90, 90.

When cutting the longitudinal end edges 91a and 92a of the main body material 90 of the axle housing using the plasma cutting torch 10, the upper surface 91 of the opposite upper surface 91 and lower surface 92 is set as the target portion to be cut. When the lower surface 92 is a standby portion on the side where cutting is not performed (hereinafter, the same applies to the case where the upper surface 91 and the lower surface 92 are reversed unless otherwise specified in this section), the lower surface 92 is directly below the upper surface 91. Is present, plasma cutting of the upper surface 91 will be performed. At this time, the plasma arc A is strongly ejected below (the back side) of the portion where the upper surface 91 is being cut. Therefore, if the upper surface 91 is cut in the atmosphere, the influence of the heat of the ejected plasma arc A is exerted. There is a possibility that the heated lower surface 92 may be melted, modified, deformed, roughened or the like, which is applied to the lower surface 92. Further, the metal material M1 melted down from the upper surface 91 may be ejected toward the lower surface 92, adhere to the inner side surface 92b of the lower surface 92 and solidify, and become a deposit M2, as shown in FIG. ..

However, in the present embodiment, as shown in FIG. 3, since plasma cutting is performed in a state where the lower surface 92 serving as a standby portion is arranged in water W which is a liquid refrigerant, the lower surface 92 is cooled. The heat of the ejected plasma arc A does not easily affect the lower surface 92. Further, the metal material M1 melted down from the upper surface 91 is cooled in water before reaching the lower surface 92 to become a granular solidified product M3, so that adhesion to the inner side surface 92b of the lower surface 92 is suppressed. Due to these effects, when the upper surface 91 is cut, the lower surface 92 is less likely to be affected by heat such as denaturation and the quality is less likely to be deteriorated by the deposit M2 due to the influence of the cutting. The metal material M1 melted down from the upper surface 91 may form deposits M2 not only on the inner side surface 92b of the lower surface 92 but also on the inner side surface 91b of the upper surface 91 (see FIG. 7), but directly below the upper surface 91. By cutting in the presence of water W, the formation of deposits M2 on the inner side surface 91b of the upper surface 91 can be suppressed due to the cooling effect of the metal material M1.

On the other hand, if the entire axle housing body 90, that is, both the upper surface 91 and the lower surface 92 are arranged in water W to perform plasma cutting of the upper surface 91, the high temperature immediately after cutting is performed at the portion of the upper surface 91 that has been cut. The metal material will come into direct contact with the low temperature water W. Then, due to quenching, the site may be denatured and the hardness may be increased. In addition, the cut surface 91c of the upper surface 91 may be roughened by the convection or wave motion of the water W, and the smoothness of the cut surface 91c may decrease. On the other hand, by arranging the upper surface 91 outside the water W, it is possible to prevent these situations from occurring due to contact with the water W. That is, on the upper surface 91, it is possible to avoid hardening due to quenching and roughness of the cut surface 91c due to contact with water W. Even if the inner side surface 91b of the upper surface 91 is in contact with the water W, if the portion above the inner side surface 91b to be the cut surface 91c is arranged outside the water W, those situations can be maintained at a certain level. It can be avoided. However, as described above, by arranging the upper surface 91 completely above the water surface W1 including the inner side surface 91b so that the inner side surface 91b also does not come into contact with the water W, the cut portion is particularly effective. Hardening and roughening can be avoided. In particular, if the water level is set so that the distance from the inner side surface 91b of the upper surface 91 to the water surface W1 is 50 to 100% of the plate thickness of the metal material constituting the axle housing main body 90, the inner side surface 91b Due to the effect of the voids between the water surface W1 and the water surface W1, smoothing of the cut surface 91c can be effectively achieved together with reduction of deposits on the lower surface 92b.

Further, by arranging a part of the axle housing main body 90 in water for cutting, it is possible to obtain an effect that the deformation of the main body 90 due to cutting is suppressed by cooling with water W. In a metal member manufactured through press molding, such as the main body material 90 of an axle housing, stress is accumulated during press molding, but stress is released by heating accompanying cutting, and the metal member has a thickness (upper surface). Deformation such as change (distance between 91) and lower surface 92), warpage, and bending may occur. However, by cutting while cooling with water W, deformation due to stress release can be suppressed. As a result, the pair of main body materials 90 and 90 after cutting are butted at the new longitudinal end edges 91d and 92d and then welded, and when the axle housing is constructed, the butting and welding can be performed with high accuracy. ..

Furthermore, by performing the cutting in water, the efficiency of the entire cutting work and the working environment can be improved. First, since the dust (fume) generated during plasma cutting dissolves in water without being dispersed in the atmosphere, the workability of cutting is improved. Further, since the metal material M1 melted down at the time of cutting is rapidly cooled to become a granular solidified material M3 and precipitates, the waste derived from the melted down metal material M1 can be relatively easily removed by filtration or suction of water W. Can be collected in. Further, in plasma cutting in the atmosphere, a large amount of nitrogen oxides (NOx) are generated, but the generation rate can be reduced by cutting near water W.

The cutting means is not limited to the form of plasma cutting using the plasma cutting torch 10 as the cutting means, and is capable of applying heat to a part of the plate-shaped metal material and cutting the metal material in a part of the region. Other forms can be applied as long as it is a cutting method using. Examples of other forms of cutting methods include a heat cutting method using a flame, a laser cutting method using a laser beam, and the like, such as gas cutting.

However, the plasma cutting method can perform cutting with high accuracy as compared with the case of using a flame, and can obtain a sharp cut surface 91c with high smoothness. In addition, cutting can be performed at high speed. On the other hand, the plasma cutting method can perform cutting with high accuracy and high speed by using simple and inexpensive equipment as compared with the laser cutting method. From these viewpoints, it is preferable to use the plasma cutting method.

In particular, when plasma cutting is performed using oxygen as the operating gas, cutting can be performed at high speed even on a thick metal material having a plate thickness of more than 10 mm. In the form described above, the axle housing body material 90 is applied as the work to be cut, but since the axle housing body material 90 is a constituent member of a vehicle such as a truck, high strength is required. .. Therefore, it has a large plate thickness of about 7 to 22 mm. By performing plasma cutting using oxygen as an operating gas, it is possible to efficiently cut the main body material 90 having such a large plate thickness. Further, as described above, the pair of main body materials 90, 90 which have been cut at the longitudinal end edges 91a, 92a are butted against each other at the new longitudinal edge 91d, 92d and fixed by welding, but plasma. By cutting, the new longitudinal edge edges 91d and 92d are formed with excellent shape accuracy and a smooth and sharp cut surface (91c and the corresponding cut surface of the lower surface) for butt and welding. The accuracy can be improved. As a result, it is possible to obtain an axle housing having high shape accuracy and high strength of the welded portion through welding.

As described above, the plasma cutting method has advantages over the thermal cutting method using a flame and the laser cutting method, but the plasma arc A is ejected from the plasma cutting torch 10 with a strong force to perform cutting. Plasma arc A and molten high-temperature metal material M1 are often ejected on the back side of the surface with vigorous force. In particular, when oxygen is used as the operating gas, the energy density of the plasma arc A becomes high, so that these phenomena become remarkable. Therefore, in the plasma cutting method, the influence on the lower surface 92 tends to be larger during the cutting of the upper surface 91 than in the thermal cutting method or the laser cutting method using a flame. However, in the present embodiment, as described above, the upper surface 91 is cut with the lower surface 92 placed in water, and the cooling effect of the water W affects the lower surface 92 that may occur during plasma cutting. Can be effectively suppressed.

In the above embodiment, the plasma cutting torch 10 is automatically moved with respect to the main body 90 by using the NC device 20 with the axle housing main body 90 as the work fixed, and the longitudinal end edge 91a is used. , 92a is cut along the entire area. The form is not limited to such a form, and the plasma cutting torch 10 may be manually moved, or conversely, the work may be moved with respect to the plasma cutting torch 10. However, by moving the plasma cutting torch 10, it is possible to cut a large work such as the axle housing body material 90, and to cut a long region such as the longitudinal end edges 91a and 92a. It can be easily applied to cutting into relatively complicated shapes. In particular, by controlling the position of the plasma cutting torch 10 using the NC device 20, cutting can be performed with high accuracy.

In this case, as shown in a later embodiment, the upper surface 91 to be cut and the upper surface 91 to be cut by appropriately adjusting the moving speed of the plasma cutting torch 10 together with the energy density of the plasma arc A emitted from the plasma cutting torch 10. It is possible to improve the smoothness of both the lower surfaces 92 waiting in water. As a result, in the obtained product, it is possible to improve the quality such as the smoothness of the surface constituting the product and the accuracy of the processed shape.

In the axle housing main body material 90, cutting is continuously performed from the start end edge 93 to the end edge 94, and the cut piece 95 including the surplus portion is separated, as in the above-described embodiment, from one part of the end edge of the work to the other. When cutting up to one site continuously, it is necessary to continue cutting stably from the cut at the initial stage of cutting to the cut through at the end of cutting. Usually, in plasma cutting, when cutting is started from an in-plane portion of a metal material, piercing for forming a through hole is performed using a pilot arc, and cutting is often started from that as a starting point. However, when starting cutting from the starting edge 93, which is the end of the surface of the metal material, it is necessary to cut from the portion where the metal material does not exist to the portion where the metal material exists, and the piercing is the starting point for stability. It is difficult to initiate a cut. In order to stably start cutting under such difficult conditions, as described above, the plasma cutting torch 10 is started to be moved at a low speed while emitting a pilot arc on the outside of the main body material 90. Then, the pilot arc sufficiently close to the main body material 90 is switched to the main arc, and immediately after the increase in the current value is detected, the moving speed of the plasma cutting torch 10 is controlled to increase the stability from the beginning of cutting. Cutting can be performed under the specified conditions. Further, by appropriately using the pilot arc, it is possible to prevent the electrodes of the plasma cutting torch 10 from being unnecessarily consumed before the cutting is started.

On the other hand, at the end of cutting, when the current value flowing between the plasma cutting torch 10 and the main body material 90 begins to decrease after the cutting reaches the end edge 94, the plasma cutting is performed before the current value becomes completely zero. By stopping the emission of the plasma arc A from the torch 10, cutting can be stably completed. As a plasma cutting torch, a torch in which the current value gradually drops and reaches zero or its vicinity is often detected as an abnormality. In such a case, an abnormality occurs due to the decrease in the current value. It is possible to avoid taking measures such as an emergency stop when the plasma cutting torch 10 is detected, and to stably stop the operation of the plasma cutting torch 10 after cutting through the terminal edge 94 to end the cutting. The specific current value when the operation of the plasma cutting torch 10 is stopped may be set to a value higher than the threshold value at which an abnormality is detected.

In the above embodiment, the cutting device 1 includes a holding jig 30 capable of holding a pair of main body materials 90 and 90, and a pair of plasma cutting torches 10 and 10, and a pair of main body materials 90. 90 cuttings can be performed at the same time. In this way, by configuring the plurality of cutting means to simultaneously cut a plurality of works held by the common holding means, a large number of works can be cut as compared with the case where only one work is cut at a time. It is possible to efficiently cut an individual. In particular, when one product is composed of a pair of workpieces such as the axle housing body material 90, the process of manufacturing a pair of workpieces from a common raw material or cutting by simultaneously performing the pair of workpieces. It becomes easy to secure continuity with the previous and next processes such as the process of joining the subsequent pair of workpieces.

Further, using a holding means capable of changing the arrangement of the work, as in the holding jig 30 of the above embodiment, the first plate-shaped portion 91 is set as the target portion with the change in the arrangement of the work sandwiched between them. The first step of cutting the first plate-shaped portion 91 with the plate-shaped portion 92 as the standby portion, the second plate-shaped portion 92 as the target portion, and the first plate-shaped portion 91 as the standby portion. If the second step of cutting the second plate-shaped portion 92 is configured to be continuously performed in sequence, both the first plate-shaped portion 91 and the second plate-shaped portion 92 can be formed. On the other hand, the processing for cutting can be efficiently advanced. In particular, when cutting two plate-shaped portions having substantially the same shape, such as the upper surface 91 and the lower surface 92 of the axle housing body material 90, into the same shape, basically the same process is repeated. As a result, both sides can be cut, so that highly efficient cutting can be performed using a simple device configuration and control mode.

Examples of the present invention are shown below. The present invention is not limited to these examples.

[1] Evaluation of deformation due to cutting The degree of deformation generated in the work due to stress release due to heating during plasma cutting was evaluated.

[Test method]
As shown in FIG. 6, the axle housing main body material was prepared by press molding, and the surplus portion of the longitudinal end edge thereof was cut by a plasma cutting method. The plate thickness of the steel material constituting the main body material was 7 mm.

Plasma cutting was performed under three conditions: air, semi-water, and total water. When cutting in the air, the cutting was performed with the main body material placed on a drainboard-shaped table. When cutting in semi-water or full-water, the cutting was performed with the main body material held in a water tank in which water was stored. In the case of semi-water, the main body material was made to exist in the water up to the central position between the upper surface and the lower surface. In the case of all water, the inner surface of the upper surface is in contact with the water surface, that is, the lower surface is in the water and the upper surface is in contact with the water surface on the inner surface and is outside the water.

A plasma cutting torch (manufactured by Komatsu) using oxygen as an operating gas was used for cutting. The cutting conditions were an output of 200 A, a nozzle diameter of φ2.2 mm, a cutting speed (moving speed of the torch) of 3 m / min, and a torch height at the time of cutting of 4 to 5 mm.

Before and after cutting, the width, warpage, and bending parameters of the main body material were measured. As shown in FIG. 6, the width P1 was measured with a caliper as a distance between the outer surface of the upper surface and the outer surface of the lower surface of the main body material. Measurements were made at multiple points on the top and bottom of the axle housing and the maximum displacement from the design dimensions was recorded. The warp P2 was measured using a three-dimensional measuring machine as a deviation from the plane of the surface of the plate material. At this time, the maximum value of the displacement amount at a plurality of points on the upper surface and the lower surface was recorded with reference to the central position in the longitudinal direction x of the axle housing. The bending P3 was measured using a height gauge as a deviation from the linear shape along the longitudinal direction x of the main body material. At this time, with reference to the straight line connecting both ends in the longitudinal direction, the maximum value of the displacement amount at a plurality of points on the upper surface and the lower surface and the inclination angle of the edge in the longitudinal direction were measured and recorded after cutting.

[result]
Table 1 summarizes the measurement results of the displacements of width, warpage, and bending under each condition of air, semi-water, and total water.

In Table 1, when the amount of change in width and warpage before and after cutting and the measured value of bending after cutting are compared between each condition, all parameters are more than in semi-water or in semi-water than when cutting in air. The value is small when cutting in all water. This indicates that by arranging at least a part of the work in water for cutting, the effect of cooling can reduce the deformation due to the influence of heat at the time of cutting.

In addition, the values of each parameter when cutting in semi-water are about the same as or smaller than those in the case of cutting in full water. This indicates that it is not necessary for the entire work to be placed in water in order to obtain the effect of preventing deformation due to cooling, and that the effect can be sufficiently achieved if only about half of the work is placed in water. There is.

[2] Evaluation of the influence of plasma cutting conditions The conditions of plasma cutting, the energy density of the plasma arc emitted from the plasma cutting torch, and the adjustment of the cutting speed (the speed at which the plasma cutting torch is moved) are adjusted to the cutting part and standby after cutting. The effect on the condition of the department was investigated.

[Test method]
The cutting test was performed under the conditions corresponding to the semi-water of the test of the above [1]. At this time, by changing the flow rate of the oxygen gas, the energy density of the plasma arc was changed variously, and the cutting speed was also changed variously. The nozzle diameter of the plasma arc was set to φ2.5 mm and φ3.0 mm.

The quality of the upper surface and the lower surface of the main body material after cutting was evaluated. On the upper and lower surfaces, dross-like or protruding deposits are not formed on the inner side surface, or even if they are formed, they are adhered only with a weak force that can be removed by the operator by hand. Was judged to be good. On the other hand, when the deposit was attached with a strong force that could not be easily removed by hand, it was determined to be defective. In the example of FIG. 7, protrusions M2 that cannot be easily removed are formed on the upper surface and are judged to be defective, but on the lower surface, no deposits are confirmed and it is judged to be good. When both the upper surface and the lower surface can be determined to be good, the cutting condition is determined to be good, and when either the upper surface or the lower surface is determined to be defective, the cutting condition is determined to be defective.

In FIG. 8, when the cutting conditions are judged to be good in each combination with the cutting speed as the horizontal axis and the energy density as the vertical axis, “○” (nozzle diameter φ2.5 mm) and “●” (nozzle diameter φ3.0 mm) ), And the case where it is judged that the cutting condition is bad is indicated by "x". Looking at the results, as shown by the broken line, points with good cutting conditions are gathered in the region of energy density of about 41 to 56 A / mm ² . This result shows that by appropriately adjusting the energy density and cutting speed, good finish quality with less deposits and high smoothness can be obtained on both the upper surface as the target portion and the lower surface as the standby portion. ing.

Although the embodiments of the present invention have been described in detail above, the present invention is not limited to the above embodiments, and various modifications can be made without departing from the gist of the present invention.

1 Cutting device 10 Plasma cutting torch (cutting means)
20 NC device 30 Holding jig (holding means)
40 Water tank (liquid refrigerant storage means)
50 Conveyor (conveyor means)
90 (Axle housing) Body material 91 Top surface (first plate-shaped part)
92 Bottom surface (second plate-shaped part)
91a, 92a Longitudinal edge 91b, 92b Inner surface 91c Cut surface 91d, 92d New longitudinal edge 93 Start edge 94 Termination edge 95 Cut piece A Plasma arc M1 Melted metal material M2 Adhesion M3 Granular solidified W Water (liquid refrigerant)
W1 water surface

Claims (11)

It is made of a metal material by applying heat to a part of the plate-shaped metal material and cutting the metal material in the part of the region, and the first plate-shaped part and the first plate. In a cutting method for cutting an object to be cut having a second plate-shaped portion facing the first plate-shaped portion separated from the shaped portion.
The cutting means is a plasma cutting torch.
Of the first plate-shaped portion and the second plate-shaped portion, one is a target portion and the other is a standby portion.
It said standby unit is arranged in the liquid refrigerant, in a state in which the target unit is arranged outside the liquid refrigerant, have rows cleavage of the target unit,
When cutting the target portion while moving the cutting means along the surface of the target portion, starting from the starting end edge which is one part of the end edge of the target portion.
With the cutting means arranged outside the starting edge and the plasma arc emitted from the cutting means, the cutting means is moved toward the starting edge and flows between the cutting means and the object to be cut. A cutting method characterized by increasing the moving speed of the cutting means when the current value starts to increase . The cutting method according to claim 1 , wherein the plasma cutting torch uses oxygen as an operating gas. The cutting method according to claim 1 or 2 , wherein the surface of the target portion facing the standby portion is arranged so as not to come into contact with the liquid refrigerant. The invention according to any one of claims 1 to 3 , wherein the object to be cut is cut while the cutting means is moved with respect to the object to be cut while the object to be cut is fixed. How to cut. While moving the cutting means along a surface of the front Symbol target portion, the terminal edge as an end point which is a part position of the edge of the target portion, when performing cutting of the object portion,
After cutting by the cutting means has reached the terminal edge, starting lower the value of the current flowing between said cutting means and said object to be cut, before current value becomes zero, the plasma from the cutting means The cutting method according to any one of claims 1 to 4 , wherein the emission of the arc is stopped. When the target portion is cut by the cutting means, the energy density of heat given to the object to be cut by the cutting means and the cutting means are described so that the smoothness of the target portion and the standby portion is increased. The invention according to any one of claims 1 to 5 , wherein at least one of the moving speed of the cutting means when cutting the object to be cut while moving the object to be cut is adjusted. How to cut. The first step of cutting the first plate-shaped portion by using the first plate-shaped portion as the target portion and the second plate-shaped portion as the standby portion.
Of the second step of cutting the second plate-shaped portion by using the second plate-shaped portion as the target portion and the first plate-shaped portion as the standby portion.
The cutting method according to any one of claims 1 to 6 , wherein after performing one step, the arrangement of the object to be cut is changed and the other step is performed. The cutting method according to any one of claims 1 to 7 , wherein a plurality of the cutting means are used to simultaneously cut a plurality of objects to be cut held by a common holding means. The object to be cut is a pair of metal members having the first plate-shaped portion and the second plate-shaped portion in a bent portion formed by bending a plate material into a U-shaped cross section.
The cutting means is used to cut the surplus wall at the edge of the bent portion of the pair of metal members, and then the pair of metal members are abutted against each other and fixed at the edge. The cutting method according to any one of claims 1 to 8 . With the cutting means
A holding means for holding the object to be cut at a position where the object to be cut can be cut by the cutting means.
It has a liquid storage means for storing the liquid refrigerant, and has
A cutting apparatus according to any one of claims 1 to 9 , wherein the cutting method is executed. The cutting device has a transport means in the liquid storage means.
The conveying means, the cut pieces are separated into the liquid refrigerant when performing the cutting of the object to be cut by said cutting means, to claim 10, characterized in that transport to the outside of the liquid storage means The cutting device described.

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