JPH0418930B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Technical Field of the Invention] The present invention relates to a press working method for precisely cutting and punching thin metal materials without producing burrs.

[Technical background of the invention and its problems]

Generally, small metal parts used in electron tubes and the like are mostly formed into a predetermined shape by press working, but burrs generated during press working can have a negative effect on the characteristics of the product. For example, an inner shield provided within a color cathode ray tube is also a type of this type of component. That is, color cathode ray tubes are required to have stricter pressure resistance characteristics year by year, and this tendency is particularly pronounced for larger tubes. Here, there is a strong correlation between the amount of dust in the pipe and the process straight withstand voltage failure rate, and in particular, extremely small fallen metallic objects in the dust further deteriorate the withstand voltage characteristics. The inner shield has the highest specific gravity among the parts made of metal inside the pipe, both in terms of surface area and cutting length during processing, and reduces the amount of metal foreign objects (burrs) that will fall. There is a need.

The manufacturing of the above inner shield is shown in Figure 1 a, b,
It depends on the steps shown in c, d, and e. That is,
Step of punching a blank 11 and four square holes 12 from a material (not shown) by press working in a, b
a first bending and beat forming step, a second bending step c, a third bending step d, a U-shaped bending step e;
It is manufactured through a cleaning (degreasing) process and a blackening process (not shown). Among the above steps, burrs are generated in the blank made of the material a and the step of punching square holes.

Here, punching using a conventional press machine will be explained. First, as the material for the aforementioned inner shield, a very thin 0.15 mm thick iron material with low carbon content is used due to the necessity of its use. For this reason, the clearance between the punch and die for punching is set to an extremely small value of 0.01 mm or less on one side.

Normally, press machines used for blank processing for inner shields are in the 100-ton to 200-ton class because the area of the inner shield is large. For this reason, even if a press machine equivalent to JIS class 1 or higher is used, the parallelism accuracy between the press machine's head and the ram is only about 0.1 mm, and as a result, as mentioned above,
Even if the clearance of the cutting die is set to a high precision of around 0.01mm, when it is attached to a press machine, the clearance will be 0.03mm in some places, and negative clearance in other places, making it feel like the punch is biting the die. become.

The smaller the above-mentioned clearance is, the less burrs will occur, and good results can be obtained by setting the clearance to 0.01 mm or less. However, the clearance
When it is about 0.03 mm or more, the burr becomes large and a problem occurs when used as an inner shield.

Therefore, conventionally, the clearance was adjusted to 0.01 mm or less as follows. First, punches are made of tool steel that is hardened to a hardness of HRC 60 to 63.
On the other hand, the die heats the tool steel and has HRC40~
Make it a relatively soft hardness of about 45. Such a cutting die is attached to a press machine, and the material for the inner shield is test punched to check for burrs. As a result, in areas with large burrs, that is, areas where the clearance has become larger than approximately 0.03 mm due to the parallelism accuracy of the press machine, etc., as mentioned above, the cutting edge of the die in that area was hammered. Knock it out inside the die. This tapping is possible because the hardness of the die is made relatively soft. Next, the ram of the press machine is lowered, and the punched part is scraped off (sieving).
By repeating this several times, we completed the appropriate clearance adjustment (0.01mm or less) and center alignment of the upper and lower molds, and after confirming that the punching condition was good, we started punching the inner shield.

However, such a press working method has the following problems. In other words, because the clearance between the punch and the die is small, the inner surface of the die is rubbed by the outer edge of the punched blank, and the outer surface of the punch is rubbed by the inner edge of the punched workpiece. Since these parts are rubbed by the metal, the wear of these parts is large and the life of the mold is shortened. Furthermore, since the die is hammered out for the clearance adjustment described above, its hardness must be relatively soft (the highest hardness within the range that allows hammering out), and quenching cannot be performed. In addition, the reason why the die cannot be hardened is that the clearance is small, which causes abnormalities such as two-piece machining in the workpiece, and if some eccentric load is applied to the upper die and the perpendicularity of the punch is distorted, the punch may become distorted. Galling occurs with the die. In this case, if both parts are hardened and hardened, they will both be damaged and the work will become impossible. For these reasons, the die cannot be hardened. Furthermore, this caused the cutting edge to quickly wear out, resulting in large burrs on the workpiece.

When large burrs are generated in this way, they fall into the pipe during transportation or handling during the assembly process. Moreover, this burr scrapes off the blackened film of other inner shields, and it is attached to the inner shield and brought into the pipe.
As described above, these adversely affect the voltage resistance characteristics of the cathode ray tube.

In order to prevent such problems, conventionally,
Once the mold is installed on the press machine and the clearance adjustment is completed, even if the production at that time is completed, it is possible to maintain good clearance without removing the mold as long as the press machine is convenient, or to remove the punched inner The problem was dealt with by thoroughly controlling the burr on the shield (normally burr height is controlled at ±0.1mm) and by frequently performing mold repairs (blade sharpening, clearance control). However, these methods cannot sufficiently prevent the occurrence of burrs, and improvements have been desired.

[Purpose of the invention]

An object of the present invention is to provide a press working method that allows punching into a predetermined shape without creating burrs without performing troublesome clearance adjustments or the like.

[Summary of the invention]

In the press processing method according to the present invention, the clearance between the punch and the die is set to 100% or more of the thickness of the material to be processed, and the cutting edge of either the punch or the die is made into an arcuate edge, and the other The cutting edge of the press ram is a sharp edge, and as the press ram operates, the workpiece is torn and separated by the sharp edge while the workpiece is clamped and restrained by the opposing surfaces of the stripper, knockout, and die.

[Embodiments of the invention]

Hereinafter, the present invention will be described in detail with reference to an embodiment shown in the drawings.

FIG. 2 shows the cutting die section of the press machine used in the present invention. In the figure, a lower die shoe 15 is mounted on a pressbed (not shown), and a punch 16 for punching the outer shape of the blank 11 shown in FIG. 1 is fixedly attached to the upper surface of the shoe. This punch 16 has a die 17 for punching out the square hole 12 shown in FIG.
It also serves as a square hole punching die 17. A stripper 18 is fitted onto the outer periphery of the punch 16 so as to be movable up and down. Moreover, this stripper 18 is connected to the spring 1
9 on the lower die shoe 15, and is positioned by this spring 19 so that its upper surface is substantially flush with the upper surface of the punch 16. FIG. 3 is a plan view of the left half of this lower mold. In addition, the square hole die 17 provided on this punch 16 is
As shown in FIG. 5, it has the shape of a vertically extending through hole, and a knockout 20 is fitted inside the hole so as to be vertically movable. This knock out 20
is caused by the spring 21 so that its tip (upper end) is connected to the die 1.
It is positioned so that it is almost flush with the top surface of 7.

Returning to FIG. 2, reference numeral 25 denotes an upper die shoe, which is attached to a press ram (not shown) and moves up and down as the press ram operates. 26 is an outline cutting die, which is attached to the lower surface of the upper mold shoe 25.
When descending, it fits onto the outer periphery of the outline punch 16 while maintaining a predetermined clearance. Reference numeral 27 denotes a knockout, and as shown in FIG. 4, the outer circumferential shape is approximately similar to the inner circumferential shape of the outer punching die 26. This knockout 27 is connected to the upper mold shoe 2 via a spring 28.
5, and is normally positioned such that its lower surface slightly protrudes from the lower surface of the outline cutting die 26 by the repulsive force of the spring 28. Reference numeral 29 denotes a square hole punch, which is fixedly attached to the lower surface of the upper die shoe 25 so as to face the square hole punch die 17 provided on the lower die, and penetrates through the knockout 27 as shown in FIG. protrudes from its underside.

In addition, in FIG. 2, 30 is a workpiece for the inner shield.

Here, the clearance between the outline punch 16 and the die 26 and the clearance between the square hole punch 29 and the die 1
The clearance with 7 is 100 of the thickness of the workpiece 30.
Set to % or more. In the example, the thickness of the workpiece 30 was 0.15 mm, and each of the above-mentioned clearances was 0.3 to 0.5 mm on one side. In addition, the cutting edges of the punch 16 and die 17 are sharp edges, and the die 26 and die 26 have a sharp edge.
The cutting edge of No. 9 was an arcuate edge. Experiments have shown that a radius of about 1.0 mm is good for this arcuate edge.

In the above configuration, when the press ram is operated and the upper die show 25 is lowered with the workpiece 30 positioned above the stripper 18 of the lower die and the upper surface of the punch 16, the knockout 27 of the upper die side is first removed. The lower surface of is in contact with the upper surface of the workpiece 30,
The workpiece 30 is clamped and restrained by the upper surface of the outline punch 16. Next, the tip of the square hole punch 29 comes into contact with the upper surface of the workpiece 30, and the workpiece 30
to be clamped and restrained. Then, as the upper die shoe 25 descends, the workpiece 30 is punched out together with the square hole punching die 17, as shown in FIG. At the same time, the lower surface of the outline cutting die 26 comes into contact with the upper surface of the workpiece 30, and the stripper 1 located on the lower surface
The workpiece 30 is clamped and restrained together with the upper surface of the workpiece 8. Then, by further lowering the upper die shoe 25, the workpiece 30 is punched together with the outline punch 16 to obtain the blank 11 shown in FIG.

Here, the process of cutting the punched portion will be explained with reference to FIGS. 6 and 7. FIG. 6 shows an enlarged view of the punching process of the square hole 12. In this case, the workpiece 30
As described above, first, the cutout 27 is clamped and restrained by the lower surface of the knockout 27 and the upper surface of the square hole punching die 17 (which is also the upper surface of the outline punch 16).
In this state, the square hole punch 29 descends and punches out the workpiece 30 while clamping it between its tip and the knockout 20. In the figure, A, B, C, and D represent the lowered positions of the punch 29. As is clear from the illustration, as the punch 29 descends, the workpiece 30
It is pressed and bent along the arcuate edge of the punch 29, and is torn off and separated at the sharp edge 17a of the die 17. In this case, the hole shape is formed to follow the dimensions of the die 17 with a sharp edge. On the other hand, the punched blank part is deformed and becomes scrap. In addition, at this time, since the clearance between the punch 29 and the die 17 is large, the deformed outer edge of the scrap side does not come into contact with the inner surface of the die 17 during tearing, and this area is not rubbed and worn. do not have.

FIG. 7 shows the outline cutting process. In this case too,
The workpiece 30 is knocked out 27 as described above.
The lower surface of the punch 16 is clamped and restrained by the upper surface of the punch 16. In this state, the outline cutting die 26 descends and punches out the workpiece 30 while clamping the workpiece 30 between its lower surface and the upper surface of the stripper 18.
In the figure, A, B, C, and D represent the lowered positions of the outline cutting die 26. As is clear from the illustration, as the die 26 descends, the workpiece 30 is pressed and bent along the arcuate edge of the die 26, and is torn off and separated by the sharp edge 16a of the punch 16. In this case, the shape of the punched blank follows the dimensions of the punch 16 with a sharp edge. On the other hand, the punched workpiece 30 is deformed and becomes scrap. Also, in this case, since the clearance between the punch 16 and the die 26 is large, the inner side of the torn workpiece 30 does not come into contact with the outer surface of the punch 16, and this area is not rubbed and worn. do not have.

FIG. 8 shows a conventional punching section, and as shown in the figure, burrs are formed to protrude in the punching direction (downward). FIG. 9 shows a punched part processed by the method of the present invention. As is clear from the illustration,
Although arcuate portions occur, burrs do not occur as in the conventional method.

Further, in the present invention, since the clearance between the punch and the die is set to be large, there is no need for the troublesome clearance adjustment that involves punching out and shaving the die as in the past. Also, as a result,
Both the punch and die can be hardened and hardened. It has also become possible to use cemented carbide for these punches and dies. Therefore, machining problems due to such wear and the like do not occur, and high-precision machining can be maintained for a long period of time.

In the above embodiments, the inner shield of a color cathode ray tube was exemplified as the product to be processed, but of course the method is not limited to this manufacturing method, and is generally related to sheet metal press working in general. It is particularly effective for burr-free processing of thin plates, and is suitable for processing electron shields, inside electron shields, etc. in addition to the above-mentioned inner shields.

In that case, the cutting edge of one of the punch and die should be an arcuate edge, and the other cutting edge should be a sharp edge, but the cutting edge of the punch or die on the side corresponding to the one that remains as a pressed product should be a sharp edge. The cutting edge of the punch or die on the side corresponding to the scrap may have an arcuate edge.
It can be appropriately selected depending on the product shape and mold structure.

〔Effect of the invention〕

As described above, according to the present invention, it is possible to perform burr-free punching without the need for troublesome clearance adjustment, and the effect is extremely large when used in the processing of electron tube parts and the like.

[Brief explanation of drawings]

Figures 1 a, b, c, d, and e are diagrams showing the manufacturing process of the inner shield, Figure 2 is a diagram showing the main parts of a press machine used in an embodiment of the press working method according to the present invention, and Figure 3 4 and 4 are plan views of the lower mold and upper mold shown in FIG. 2, FIG. 5 is a diagram showing the operating state of the portion shown in FIG. 2, and FIG. 6 and FIG. Diagram showing the chopping separation process,
FIG. 8 and FIG. 9 are diagrams showing the shapes of punched parts according to the conventional method and the method of the present invention. 11... Blank, 12... Square hole, 16... Outline punch, 17... Square hole punching die, 18...
Stripper, 20, 27... knock out, 2
6... Outline punching die, 29... Square hole punch,
30...Work material.

Claims (1)

[Claims] 1. Set the clearance between the punch and die to 100% or more of the thickness of the workpiece material, and set the cutting edge of either the punch or die to have an arcuate edge and the other cutting edge to have a sharp edge. . A press working method characterized in that, as the press ram operates, the workpiece is torn and separated at the sharp edge while the workpiece is clamped and restrained by opposing surfaces of a stripper, a knockout, and a die.