JPH0757468B2 - Mold cleaning method by electric discharge machining - Google Patents

Description

Detailed Description of the Invention [Industrial applications]

The present invention relates to a method for blasting a die by electric discharge machining, and more specifically, it removes a deteriorated layer such as a hardened layer on the die surface by electric discharge machining and improves the surface roughness of the machined surface, and increases fatigue strength by peening. For the cleaning method.

[Prior Art and Problems] Generally, a die such as a die-casting die manufactured by die-sinking electric discharge machining has a residual stress caused by tensile stress acting on the surface due to the presence of a layer in which the surface of the electric discharge machining is once melted and re-solidified. However, the residual residual tensile stress weakens the fatigue strength, and the hardened layer below the re-solidified layer causes microcracks, so the solidified layer and the deteriorated layer of the hardened layer must be removed to obtain a mold. Which cannot be used,
Also, in order to obtain the surface roughness required for die-castite products, the surface roughness of the die-casting die itself must be made corresponding to this, and further, the deteriorated layer such as the hardened layer is machine-engraved. Since this causes the life of the electric discharge mold to be about half that of the mold, it is necessary to remove and polish the deteriorated layer. In addition, since the hardened layer becomes an obstacle during the polishing, it is necessary to remove the deteriorated layer also in this sense. For example, the removal and polishing of the deteriorated layer such as die-casting dies of automobile parts with complicated shapes consisting of unevenness, grooves, taper etc. with high and low is conventionally done manually with a diamond file using a hand tool. With regard to the above, there is only a method in which a skilled worker works by gradually reducing the grain size of the paper file by hand, and it is not possible to meet the demand for mass production due to a long labor of about 30 to 40 hours. It was expensive.

【Purpose】

The present invention automates the above-mentioned conventional complete manual work, removes the deteriorated layer of the mold and polishes the processed surface in a short time of about 20 minutes, and processes to a surface roughness of 10 μ (Rmax) or less. However, at the same time, it is an object of the present invention to provide a blasting method that can achieve a life longer than that of a machine-engraved die by the effect of peening.

【Constitution】

The constitution of the first invention of the present application is # 46 to # having a hardness higher than that of the deteriorated layer of the machining surface with respect to the machining surface of the die by electric discharge machining.
The first step to obtain a surface roughness suitable for the peening treatment in the second step by injecting 80 irregular-shaped abrasives, and the # 80 to # 150 spherical abrasive having a hardness higher than that of the base material of the die. A second step of spraying a cleaning material and subjecting the die surface to a peening treatment. Further, the configuration of the second invention of the present application is such that the first step of injecting an irregular-shaped abrasive having a hardness higher than that of the deteriorated layer of the machining surface onto the machining surface of the mold by electric discharge machining, and the mother of the mold. A mixture of spherical abrasive having a hardness higher than that of the abrasive, which is 50% or less in weight ratio, is mixed with the abrasive in the first step and / or the abrasive that has been worn and crushed in the first step. And a second step.

[Action]

Therefore, according to the present invention, almost all of the deteriorated layer is removed by the injection of the irregular abrasive having a hardness higher than that of the deteriorated layer on the machining surface of the die by the electric discharge machining, and then the spherical polishing in the second step is carried out. By injecting a grinding material or a mixture of the grinding and cleaning material with 50% or less of the grinding material of the first step, the deteriorated layer on the processed surface is completely removed, the surface roughness is improved, and polishing to a glossy surface level is performed. At the same time, due to the peening effect of the second step, the fatigue strength of the mold, which is the work material, increases.

【Example】

The figure shows the whole apparatus for carrying out the method of the first invention of the present application, in which 10 is a direct pressure blast chamber in which abrasive is pressure-fed from a recovery tank 41 by compressed air, and the compressed air is branched and introduced from a nozzle. The abrasive is jetted together with the compressed air onto the processed surface of the die, which is the aluminum die casting die in the embodiment. Reference numeral 11 denotes a gravity blast chamber, and the abrasive material is transferred to the nozzle by weight and is jetted from the nozzle to the surface to be processed together with compressed air. The direct pressure blast chamber 10 and the gravity blast chamber 11
Is configured so as to be hermetically sealed by inlet and outlet doors 12 and 12 which are opened and closed by an air cylinder 16, respectively, and is internally provided with a rotary table and a plurality of nozzles driven by a motor 14, and these nozzles are driven by a motor 15. Composed of grinding material and abrasive material for the mold formed by electric discharge machining which is transferred from the direct pressure blast chamber 10 toward the gravity blast chamber 11 on the conveyor line 30 consisting of roller conveyors while reciprocally swinging. The injecting material is ejected to remove the deteriorated layer, perform a polishing process, and perform a peening process. In the blasting method of the first invention of the present application, first, as a first step, the workpiece is conveyed from the inlet 12 of the direct pressure blast chamber 10 to the chamber 10, and when the inlet is closed, in the direct pressure blast chamber 10. , 3 nozzles with a diameter of 5 mm inject the abrasive. As this abrasive, an amorphous abrasive having a relatively large grain size and a hardness higher than that of the hardened and deteriorated layer of the workpiece is used so that the grinding effect can be enhanced and the processing time can be shortened. # 46 to # 80 (590
~ 125μ). In this example, # 46 to # 80 white fused alumina chamber (WA) particles were blown at a pressure of 4 to 5 kg / cm ² and a range of 150 to 200 mm for about 15 minutes while the nozzle was rocked for 10 minutes. The working surface of the mold, which is the material to be processed, is sprayed on the table that rotates inside, and the altered layer on the working surface is removed. The WA particles may be replaced with other fused and abrasive materials having a predetermined hardness such as brown fused aluminous (A) particles, so-called alundum or carborundum. Then, the mold, which is the workpiece to which the WA particles are sprayed,
When the outlet 13 of the direct pressure blast chamber 10 is opened, the direct pressure blast chamber 10 is transferred to the gravity blast chamber 11 which is transferred on the conveyor line 30 and has the inlet 12 open, and when the inlet 12 is closed,
Three nozzles with a diameter of 4 mm are # 80- # 150 (297-44μ) with respect to the processing surface on the table that rotates as a process.
Steel beads of particle size of about 5 minutes, air pressure 4-5kg /
cm and jet distance 150 to 200 mm while oscillating the nozzle to perform peening treatment. The abrasives are not limited to steel beads, but ceramic beads and glass beads can be substituted if the degree of wear is not taken into consideration. Since the abrasives such as the steel beads are mainly required for the peening effect rather than the grinding effect, they are spherical, and the high temperature due to the discharge is not transmitted to the inside of the material, so that the metal structure does not change. The hardness (HRC60 to 65) is higher than the hardness of the base material of the mold located in the lower layer of the altered layer removed in the first step. The jetting of such steel beads exerts a peening effect such as improving the fatigue strength of the work piece by the compressive residual stress acting on the work piece, and at the same time, the work surface is cleaned and polished. When the peening process in the gravity blast chamber 11 in the second step is completed, the outlet 13 is opened by the air cylinder 16 and transferred from the conveyor line 30 to the next step. In the next step, dust on the processed surface is removed. If the blasting in the first step is performed by a blowing method, it takes a long time to grind the deep side surface of the groove portion engraved in the mold, so that the method of direct pressure blasting is adopted. Also, there is one dust collector in the blast chamber of the first and second steps.
40 and abrasive pressure recovery tank communicating with direct pressure blast chamber 10.
41 and a polishing / cleaning material recovery tank 42 that communicates with the gravity blast chamber 11 are respectively provided to separate and collect the worn or crushed abrasives and abrasives and the reusable abrasives and abrasives. That is, by the exhaust fan 17 inserted into the dust collector 45, centrifugal force due to the dust removal airflow is generated in the recovery tanks 41 and 42 which are alternately communicated with the dust collector 45 via a switching damper including an air cylinder (not shown). Fine powder, dust or dust collector that acts and is regenerated when the abrasive and abrasive cleaning material collides with the workpiece and is processed
Reusable propellant collected in 45 collects at the bottom of each tank. There is almost no consumption of steel beads. In the above-mentioned embodiment, the first step and the second step are performed in different blast chambers 10 and 11 which are different from each other. However, in order to carry out the present invention in a limited space, both blast chambers 10 and 11 are combined into one. It is also possible to construct a blasting chamber of and process this. In this case, the blast treatment was performed with the WA particles used as the abrasive in the first step, and the WA particles used as the abrasive used in the first step that could not be collected in the dust collector 45 by the dust collector 40 were worn or crushed. For example through a wire mesh of 100 mesh, the crushed and abraded abrasive material that has passed through this is sent to the recovery tank 42 for steel beads, and the reusable abrasive material that does not pass through the strainer in the previous period is Collect in the collection tank 41 of the process. In addition, the dust removal action in the recovery tank 42 in which the crushed and abraded abrasive that has passed through the recovery tank 41 and the 100-mesh wire net is introduced can usually remove almost all of the crushed and abraded abrasive. Then, as a second step, as in the above-described embodiment, a peening treatment is performed with the steel beads in the polishing tank recovery tank 42 of the second step, which is made of steel beads. In the polishing treatment of the die casting mold according to the above-described embodiment of the first invention of the present application, the surface roughness of the work piece was Rmax, 40μ and 150μ at the bottom surface and the side surface of the processing surface, respectively. After 30 to 40 μm and the second step, it could be reduced to 10 μm. Next, the second invention of the present application will be described. In the second invention of the present application, as described in the second embodiment of the first invention described above, what is caused by the abrasion or crushing of the WA particles as the abrasive in the first step is The above-mentioned recovery tank 41 and a 100-mesh wire mesh are crushed, and most of them can be removed normally by the dust removal function of the dust collector in the recovery tank 42 in which the worn abrasive is introduced. When the wear and wear of the WA particles in the first step is remarkable due to the hardness of the altered layer of the above, the WA particles which are inevitably passed through the wire net into the recovery tank 42 and remain there (WA particles). (Including a mixture of attrition and reusable) contaminated therewith). Therefore, if it is possible to transfer the WA particles together with the steel beads to the nozzle of the second step and perform the peening treatment as it is, it is efficient. Therefore, as a result of repeated tests and studies by the applicant, the WA particles About 50% of steel beads are mixed
Based on the knowledge that the peening effect of steel beads is not adversely affected if it is below, and conversely, by adding about 10%, it is possible to reduce the surface roughness to 10 μ or less. In the peening process in the second step, 10% of the steel beads, which are the cleaning and cleaning material, are abraded, crushed or recovered reusable WA particles in the first tank in the recovery tank 42.
The front and rear are used as a guide for positive mixing, and this is used as the injection material in the second step. Other processing conditions and the like are similar to those of the above-described first embodiment of the invention. In the examples of the first invention and the second invention, the hardness of the processed surface after the first step and the second step is
Before the first step: HRC60 or more, after the second step: HRC45 to 50. In the first and second inventions, the first step and the second step
The type, hardness, grain (degree) diameter, etc., of the abrasive material, the abrasive material in the process, are relatively determined by the type, hardness, and surface roughness of the die to be subjected to the abrasive treatment, and the blasting and peening treatments. In this case, in order to prevent so-called corner sag of the die, a mask material is attached to the periphery of the processing surface, or after the cleaning treatment, the surface of the processing material around the processing surface is shaved to a very small depth.

【effect】

As described above, according to the present invention, in addition to automating the conventional complete manual work, removal of the deteriorated layer of the mold and polishing of the processed surface can be performed in a short processing time of 20 minutes in one example to obtain a glossy surface. The surface roughness is processed, and at the same time, due to the effect of shot peening, the life can be made longer than that of a machine engraved mold. Further, it is also possible to perform processing in one blast chamber to carry out this process in a very limited space.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 shows an embodiment of the present invention, FIG. 1 is a front view of the first embodiment, and FIG. 2 is a side view. 10 …… Direct pressure blast chamber, 11 …… Gravity blast chamber, 12,13
...... Door, 14, 15 ...... Motor, 40 ...... Dust collector, 41, 42 ......
Recovery tank, 45 ...... dust collector

Claims (4)

[Claims] 1. A machined surface of a mold is jetted by injecting an irregular shaped abrasive of # 46 to # 80 having a hardness higher than that of an altered layer on the machined surface of the mold by electric discharge machining. A method of blasting a die by electric discharge machining, which comprises a first step and a second step of injecting a peening treatment with a # 80 to # 150 spherical abrasive having a hardness higher than that of the base material of the die. . 2. In the first step, the WA particles are used as an abrasive material.
The method for blasting a mold by electric discharge machining according to claim 1, wherein the step comprises blasting for 5 minutes, and the second step is a step for blasting steel beads as a blasting material for 5 minutes. 3. A first step of injecting an irregular-shaped abrasive having a hardness higher than that of an altered layer on the machining surface of the die by electric discharge machining to grind the machining surface of the die. A spherical abrasive having a hardness higher than that of the base material of the die is mixed with the abrasive in the first step and / or the abrasive worn and crushed in the first step in a weight ratio of 50% or less. A second method of blasting a die by electric discharge machining, comprising: 4. The abrasive in the first step and / or the abraded and crushed abrasive in the second ratio at a weight ratio of 10% or less.
The method of blasting a die by electric discharge machining according to claim 3, wherein the die is mixed with the abrasive in the step.