Method of manufacturing die

Abstract: A method of manufacturing a die having batch supply holes (2) arranged at a batch supply side thereof, slits (3) arranged at a batch discharge side thereof for forming the batch, and batch hold portions made of lateral holes (4), which are arranged at least at intersecting portions between the batch supply holes (2) and the slits (3) and are arranged corresponding to the slits (3), is disclosed. The improvement includes the steps of: preparing a die main body (11); (A) performing a batch supply hole (2) machining with respect to one principle plane of the die main body (11) so as to form the batch supply holes (2) and a slit machining with respect to the other principle plane of the die main body (11) so as to form the slits (3); and performing a lateral hole machining so as to form the batch hold portions (4), which are arranged at least at intersecting portions in the die main body (11) between the batch supply holes (2) and the slits (3) and are arranged corresponding to the slits (3); or (B) performing a slit machining with respect to one principle plane of the die main body and a lateral hole machining so as to form the batch hold portions (4) arranged corresponding to the slits (3) in the die main body (11); and performing a batch supply hole (2) machining with respect to the other principle plane of the die main body (11) so as to form the batch supply holes (2); thereby forming an integral die.

Description: 1. Field of the Invention The present invention relates to a method of manufacturing a die according to the preambles of claims 1 and 2, the die having batch supply holes arranged at a batch supply side thereof, slits arranged at a batch discharge side for forming the batch, and batch hold portions made of lateral holes, which are arranged at least at intersecting portions between the batch supply holes and the slits and are arranged corresponding to the slits, and particularly relates to a method of manufacturing a dir for extruding honeycomb structural bodies having thin walls. 2. Description of the Related Art As a die for extruding honeycomb structural bodies, there is a die comprising batch supply holes arranged at a batch supply side thereof, slits arranged at a batch discharge side for forming the batch, and batch hold portions made of lateral holes, which are arranged at least at intersecting portions between the batch supply holes and the slits and are arranged corresponding to the slits. Fig. 1 is a schematic view showing one embodiment of a die for forming honeycomb structural bodies disclosed in JP-A-53-137210, as one example of the known die which is also an object of the present invention to be manufactured. In the embodiment shown in Fig. 1, a die 1 comprises batch supply holes 2 arranged at a batch supply side of the die 1, slits 3 arranged at a batch discharge side of the die 1 for forming the batch, and batch hold portions made of lateral holes 4, which are arranged at least at intersecting portions between the batch supply holes 2 and the slits 3 and are arranged corresponding to the slits 3. In the die 1 having the construction mentioned above, a dimension of the lateral hole 4 forming the batch hold portion is larger than that of the slit 3. Therefore, in order to manufacture the die 1 having the construction mentioned above, there is one technique, as disclosed in JP-A-56-40510, such that, a metal plate is connected by brazing to a metal block to which the batch supply holes 2 and the lateral holes 4 are preliminarily worked, and then a slit machining is performed with respect to the metal plate. Moreover, there is another technique, as disclosed in JP-A-56-119335, such that, in the die manufacturing method in which a metal plate is connected by brazing to a metal block to which the batch supply holes 2 and the lateral holes 4 are preliminary worked, and then a slit machining is performed with respect to the metal plate, a depression portion is formed to the metal plate and the depression portion of the metal plate is fitted by brazing to the metal block. In the method of manufacturing the die 1 mentioned above, since the metal plate to which the slits are formed is connected by , brazing to the metal block, a brazing portion becomes a weak point, and thus it is not possible to make stronger the slits to which a large load is applied during a batch extruding operation. Moreover, in an extreme case, the brazing portion is peeled off and the die does not function for extruding. Further, in the case that the depression portion of the metal plate is fitted to the metal block, it is difficult that all of the depression portions are fitted to a plurality of projections of the metal block at one operation, and thus a high precision die cannot be manufactured. A generic method of manufacturing a die is known from US-A-3 038 201. The die has batch supply holes arranged at a batch supply side thereof, slits arranged at a batch discharge side thereof for forming the batch, and batch hold portions made of lateral holes, which are arranged at intersecting portions between the batch supply holes and the slits and are arranged corresponding to the slits. The method comprises the steps of preparing a die main body and performing a lateral hole machining so as to form the batch hold portions, which are arranged at intersecting portions in the die main body between the batch supply holes and the slits and are arranged corresponding to the slits; thereby forming an integral die. A slit machining is performed with respect to one principle plane of the die main body and lateral holes are machined so as to form the batch hold portions arranged corresponding to the slits in the die main body. A batch supply hole machining is performed with respect to the other principle plane of the die main body so as to form the batch supply holes; thereby forming an integral die, SUMMARY OF THE INVENTION It is an object of the present invention to further develop a method of manufacturing a die according to the preambles of claims 1 or 2 such that the manufactured die has sufficient strength an a high precision. This object is achieved by a method having the features of claims 1 or 2, respectively. In the present invention, an order of the machining operations can be different. However, in both cases, the batch supply hole machining, the slit machining and the lateral hole machining are performed with respect to the die main body in a predetermined order, and the die is manufactured integrally. Therefore, no brazing portion is existent in the die as compared with the known die, and thus it is possible to obtain the die having a sufficient strength and a high precision. In addition, the slit machining and the lateral hole machining are performed continuously by wire electric-discharge machining. Moreover, the manufactured die is used for extruding a thin wall honeycomb structural body having a rib thickness of not larger than 150 µm. Further, a width of the slit is not larger than 250 µm. Furthermore, the manufactured die is used for extruding a honeycomb structural body having a cell open rate of not smaller than 75%. Moreover, the manufactured die is used for extruding a honeycomb structural body having a cell density of not larger than 1800 cell/inch 2 . In all the preferred embodiments mentioned above, a die having improved properties can be manufactured easily. BRIEF DESCRIPTION OF THE DRAWINGS The present invention will be further explained in detail hereinafter with reference to the accompanying drawings, in which: Fig. 1 is a schematic view showing one embodiment of a known die having batch hole portions, which is an object of the present invention to be manufactured; Figs. 2a to 2d are schematic views respectively illustrating one embodiment of a method of manufacturing a die according to the invention in a processing order; Fig. 3 is a schematic view depicting one embodiment of a piano wire used when a lateral hole is machined by wire lap machining as a preferred embodiment; Fig. 4a is a schematic view showing one embodiment of a visual model and Fig. 4b is a schematic view for explaining an investigation method of a batch flow; Figs. 5a and 5b are schematic views respectively illustrating an investigation result of the batch flow using a die construction having one batch supply hole; Figs. 6a and 6b are schematic views respectively depicting an investigation result of the batch flow using a die construction having two batch supply holes; Figs. 7a to 7c are schematic views respectively showing an investigation result of the batch flow under the condition such that the lateral holes are varied; and Figs. 8a to 8c are schematic views respectively illustrating an investigation result of the batch flow under the condition such that shapes of the lateral holes are varied. DESCRIPTION OF THE PREFERRED EMBODIMENT A die which is an object of the present invention to be manufactured has the same construction as that of the die 1 shown in Fig.1 as a known one. That is to say, the die 1 comprises the batch supply holes 2 arranged at the batch supply side of the die 1, the slits 3 arranged at the batch discharge side of the die 1 for forming the batch, and the batch hold portions made of the lateral holes 4, which are arranged at least at the intersecting portions between the batch supply holes 2 and the slits 3 and are arranged corresponding to the slits 3. Here, it is defined that the lateral holes 4 are arranged at least at the intersecting portions between the batch supply holes 2 and the slits 3 and are arranged corresponding the slits 3. This definition means as follows. As a construction of the die 1, there are (1) all hole type in which the batch supply holes 2 are existent at all the intersecting portions between the batch supply holes 2 and the slits 3, (2) alternate hole type in which the batch supply holes 2 are existent at alternate intersecting portions between the batch supply holes 2 and the slits 3, and (3) few hole type in which the batch supply holes 2 are existent at a few intersecting portions between the batch supply holes 2 and the slits 3. Under such a condition, this definition makes clear that the lateral holes 4 are existent at all the positions where the slits 3 are arranged. Particularly, in the die having the batch hold portions according to the invention, if the number of the batch supply holes 2 is decreased, there is an effect such that a uniform batch extrusion can be achieved. The feature of the invention is how to manufacture such a die 1. Figs. 2a-2d are schematic views respectively showing one embodiment of the method of manufacturing a die according to the invention in a processing order. Hereinafter, the method of manufacturing a die according to the invention will be explained with reference to the Figs. 2a-2d. At first, as shown in Fig. 2a partly, a die main body 11 having two principle planes 11a and 11b are prepared. Materials of the die main body 11 are not limited particularly, and all the materials used generally for the die can be used. Generally, use is made of stainless steel. A plate having a dimension of, for example, 200 mm × 200 mm × 20 mm is cut out by using whetstone from stainless steel so as to form the die main body 11. Then, as shown in Fig. 2b partly, batch supply holes 2 are formed to one principle plane 11b of the thus prepared die main body 11. Machining methods of the batch supply holes 2 are not limited particularly, and all the machining methods used generally for the batch supply hole machining can be used. Generally, use is made of wire electric-discharge machining or electrochemical machining. A necessary number of the batch supply holes 2 having a dimension of, for example, diameter: 1.5 mm and depth: 150 mm are formed by drill machining to the principle plane 11b of the die main body 11. Then, as shown in Fig. 2c partly, slits 3 are formed to the other principle plane 11a of the die main body 11 after the batch supply hole machining. Generally, use is made of wire electric-discharge machining. Conditions of the wire electric-discharge machining are the same as those of wire electric-discharge machining for a lateral hole machining mentioned below. A necessary number of the slits 3 having a dimension of, for example, width: 0.23 mm and depth: 60 mm are formed to the principle plane 11a of the die main body 11. Then, as shown in Fig. 2d, lateral holes constituting batch hold portions are formed at least at intersecting portions between the batch supply holes 2 and the slits 3 and corresponding to the slits 3 in the die 1. Use is made of wire electric-discharge machining. One example of the wire electric-discharge machining is as follows: diameter of used wire: 0.08 mm; transfer speed: 1.2 mm/sec.; wire tension: 400 gf; discharge condition/ voltage of 200 V, peak current of 4 A, discharge time of 2 µs, idle time of 400 µs; resistivity of deionized water: 10 5 Ωmm (insertion method); and wire property: high strength wire. When the machining of the slits 3 and the lateral holes 4 are performed by the wire electric-discharge machining in this embodiment, the machining of the slits 3 and the lateral holes 4 can be performed at once, i.e., the machining of the lateral holes 4 can be performed continuously after the machining of the slits 3. In this case, it is possible to perform the machining process easily. Finally, the die main body 11 is machined to a predetermined shape such as a circular shape so as to obtain the die 1. Further, in the wire lap machining, as shown in Fig. 3, a piano wire 21 comprising a portion 21-1 having a constant diameter of 0.08 mm (for example 1 m length), a portion 21-2 in which a diameter thereof is gradually increased from 0.08 mm to 0.4 mm, and a portion 21-3 having a constant diameter of 0.4 mm (necessary length) is prepared. Then, the thus prepared piano wire 21 is set in the spit 3. Under such a condition, the piano wire 21 is moved back and forth in the slit 3 while alumina having a particle size of about 20 µm and solvent are supplied in the slit 3, so that the lateral hole 4 can be formed. In the case that the lateral holes 4 are machined by the wire lap machining as mentioned above, the piano wire 21 shown in Fig. 3 can be formed by etching and a diameter of the piano wire 21 can be made smaller. Therefore, the lateral holes 4 having smaller diameters can be formed. Moreover, even if the slits 3 are bended slightly, the lateral holes 4 can be preferably formed. In this manner, by utilizing at least one of the machining methods mentioned above, the necessary number of the lateral holes 4 having a dimension of, for example, diameter: 0.5 mm and length: 200 mm can be formed at the intersecting portions between the batch supply holes 2 and the lateral holes 4 in the die main body 11. In the manufacturing method according to the invention, the lateral holes 4 are formed by directly machining the die main body 11. Preferably, in view of a situation such that the lateral holes 4 are existent corresponding to the slits 3, the lateral holes 4 are formed by machining the die main body 11 by utilizing the preliminarily formed slits 3. Therefore, the batch supply holes 2, the slits 3 and the lateral holes 4 can be formed integrally in the die main body 11. In order to machine the die main body 11 by utilizing the slits 3, it is preferred to use the wire electric-discharge machining mentioned above. Further, the die manufactured according to the manufacturing method of the invention can be freely used for forming anything, but it is particularly preferred to use for forming honeycomb structural bodies such as the thin honeycomb structural body in which a rib thickness is not larger than 150 µm, the honeycomb structural body in which a cell open rate is not smaller than 75 %, and the honeycomb structural body in which a cell density is not larger than 279 cell/cm 2 (1800 cell/inch 2 ). Such honeycomb structural bodies mentioned above are thought to be difficult to form by the known die, since the rib thickness is thin. Particularly, in the case that the cell density is larger than 279 cell/cm 2 (1800 cell/inch 2 ), if the lateral hole is machined according to the known manufacturing method, the slits of the die are deformed, since the lateral hole-slit portions are weak due to the lateral holes during an actual batch extrusion. In the embodiment mentioned above, the processing order is batch supply hole machining → slit machining → lateral hole machining, but it is a matter of course that the present invention can be applied to the processing orders of, slit machining → batch supply hole machining → lateral hole machining, and, slit machining → lateral hole machining → batch supply hole machining. Also in the embodiments mentioned above, various kinds of machining methods mentioned above can be utilized as respective machining. Then, batch flow investigations by utilizing a visual model were performed with respect to the die having the batch holed portions obtained according to the manufacturing method of the invention and the die as a comparison having no lateral holes. The aim of the batch flow investigation is to investigate an effectiveness of the die having the lateral holes and to investigate effects of lateral hole shape, lateral hole shape, lateral hole variation, and so on, by simulating or visualizing the batch flow during the honeycomb extrusion. At first, as shown in Fig. 4a as one example, a batch supply hole portion, a lateral hole portion and a slit portion were constructed by acrylic to prepare the visual model. Then, as shown in Fig. 4b a batch prepared by mixing an oil clay and a tracer (chaff) was extruded by the visual model. During the batch extrusion, a movement of the tracer was followed after t seconds so as to investigate a batch flow direction and a flow speed at respective positions. Figs. 5a and 5b show respectively an investigation result of the batch flow in the die model having one batch supply hole. Figs. 6a and 6b illustrate respectively an investigation result of the batch flow in the die model having two batch supply holes. From the investigation results shown in Figs. 5a, 5b and Figs. 6a, 6b, it is understood that a uniform batch extrusion can be achieved in the die having the lateral hole as compared with the general die having no lateral holes, since tracers are aligned parallel in a lengthwise direction. Moreover, it is understood that a uniform batch extrusion can be achieved regardless of the number of the batch supply holes. Then, the same investigation was performed with respect to the die model in which the lateral hole diameter is not varied and the die model in which the lateral hole diameter is varied. Figs. 7a-7c are schematic views showing respectively the investigation result of the die mentioned above. That is to say, Fig. 7a shows the investigation result of the die model in which the lateral hole diameter is not varied, and Figs. 7b and 7c illustrate respectively the result of the die model in which the lateral hole diameter is varied. From the investigation results shown in Figs. 7a-7c, it is understood that the variation of the lateral hole diameter is not affected so much. Then, Figs. 8a-8c show respectively the investigation result of the batch flow in the die model in which a cross section of the lateral hole is varied. Here, Fig. 8a shows the investigation result of the die model in which the cross section of the lateral hole is a circular shape. Fig. 8b illustrates the investigation result of the die model in which the cross section of the lateral hole is a diamond shape. Fig. 8c depicts the investigation result of the die model in which the cross section of the lateral hole is a triangular shape. From the results shown in Figs. 8a-8c, it is understood that the cross section of the lateral hole is not affected so much. As clearly understood from the explanations mentioned above, according to the invention, the batch supply hole machining, the slit machining and the lateral hole machining are performed with respect to the die main body in a predetermined order, and the die is manufactured integrally. Therefore, no brazing portion is existent in the die as compared with the known die, and thus it is possible to obtain the die having a sufficient strength and a high precision.

Claims: A method of manufacturing a die (11) having.batch supply holes (2) arranged at a batch supply side (11b) thereof, slits (3) arranged at a batch discharge side (11a) thereof for forming the batch, and batch hold portions (4) made of lateral holes, which are arranged at least at intersecting portions between the batch supply holes (2) and the slits (3) and are arranged corresponding to the slits (3), comprising the steps of: preparing a die main body (11); performing a slit machining with respect to the other principle plane of the die main body so as to form the slits (3); and performing a lateral hole machining so as to form the batch hold portions (4), which are arranged at least at intersecting portions in the die main body (11) between the batch supply holes (2) and the slits (3) and are arranged corresponding to the slits (3); thereby forming an integral die (11), characterized by performing a batch supply hole machining with respect to one principle plane of the die main body (11) before the slit machining and the lateral hole machining so as to form the batch supply holes (2) wherein the slit machining and the lateral hole machining are performed continuously by wire electric-discharge machining with removing a cutting apparatus in between. A method of manufacturing a die (11) having batch supply holes (2) arranged at a batch supply side (11b) thereof, slits (3) arranged at a batch discharge side (11a) thereof for forming the batch, and batch hold portions (4) made of lateral holes, which are arranged at least at intersecting portions between the batch supply holes (2) and the slits (3) and are arranged corresponding to the slits (3), comprising the steps of: preparing a die main body (11); performing a slit machining with respect to one principle plane of the die main body (11) and a lateral hole machining so as to form the batch hold portions (4) arranged corresponding to the slits (3) in the die main body (11); and performing a batch supply hole machining with respect to the other principle plane of the die main body (11) so as to form the batch supply holes (2); thereby forming an integral die, characterized in that the slit machining and the lateral hole machining are performed continuously by wire electric-discharge machining with removing a cutting apparatus in between. The method of manufacturing a die according to claim 1 or 2, wherein the manufactured die (11) is used for extruding a thin wall honeycomb structural body having a rib thickness of not larger than 150 µm. The method of manufacturing a die according to claim 1 or 2, wherein a width of the slit (3) is not larger than 250 µm. The method of manufacturing a die according to claim 1 or 2, wherein the manufactured die is used for extruding a honeycomb structural body having a cell open rate of not smaller than 75 %. The method of manufacturing a die according to claim 1 or 2, wherein the manufactured die is used for extruding a honeycomb structural body having a cell density of not larger than 279 cell/cm 2 (1800 cell/inch 2 ).

Inventors: ISHII TAKEYUKI, KONDO YOSHIMASA, SHIBAGAKI YUKINARI, ISHII, TAKEYUKI, KONDO, YOSHIMASA, SHIBAGAKI, YUKINARI
Applicants: NGK INSULATORS LTD, NGK INSULATORS, LTD.
Application year: 2000
Main classification: B23P15
IPC codes: B28B3, B23P15, B29C47