KR100383425B1 - Method and device for fabricating mold insert by three-dimensional welding and milling - Google Patents

Abstract

The method for manufacturing a starting mold insert according to the present invention comprises the steps of cutting the three-dimensional computer model of the starting mold insert to be manufactured to a predetermined thickness to obtain respective cross-sectional data, and generating NC data from the data, and melting the material on the base material. Overlapping a plurality of beads having a width and a height according to the NC data of the corresponding cross section to form the corresponding cross section, and cutting the upper surface according to the NC data to make the height of the cross section constant; The step of forming the cross section and the step of cutting are repeated sequentially until all cross sections are laminated.

Description

TECHNICAL AND DEVICE FOR FABRICATING MOLD INSERT BY THREE-DIMENSIONAL WELDING AND MILLING}

TECHNICAL FIELD The present invention relates to a method and apparatus for manufacturing a starting mold insert, and more particularly, to a method and apparatus for manufacturing a starting mold insert required for testing when manufacturing an injection molded product.

In general, after the design is completed during product development, several kinds of prototypes are manufactured. There are many kinds of prototypes, such as prototypes that are manufactured to test only designs and prototypes that are required to test functionality.

Conventionally, three-axis NC (numerical control) machining has been used to produce prototype mold inserts for prototyping. In machining, the milling tool is numerically controlled to produce the final contours according to a series of machining sequences of roughing, finishing and finishing.

Such a method has a disadvantage in that it takes a lot of cutting time or complicated shape depending on the shape. Since a lot of time is required to manufacture the starting mold insert, the overall product development time is extended.

When machining a mold insert core for injection molding only with a three-axis mill, there is a need to process a narrow (2-3 mm) and deep (40 mm or more) shape. Such shapes are mainly seen in the cores needed to mold injection molded parts with thin ribs. In order to cut such a shape, the diameter of the milling tool must be small and long, which causes a problem of bending or shaking the tool during machining. In order to solve this problem, the electric discharge machining was used when processing a narrow and deep mold insert core. However, for the electric discharge machining, the work must be processed separately and a new setting must be made in the electric discharger. As such, there is a disadvantage in that total manufacturing time is extended because unnecessary time is consumed for transporting the workpiece and for new setting.

In the cavity machining, which is the opposite shape of the core, the tool must be lengthened as the height of the insert increases, as in the core. Therefore, the cutting depth should be set as the cutting depth is reduced when cutting. The machining time is increased. In addition, according to the shape of the cavity may be more parts to be removed than the remaining part after the cutting process, a lot of processing time is consumed to process unnecessary parts and waste materials.

Therefore, in order to solve this problem, the rapid prototyping method using the lamination method was started. Representative methods used for the purpose of tooling among the rapid molding methods are, for example, rapidtool of DTM corporation. However, Rapid Toul of DTM Corporation is an indirect method, which has a problem of sintering metal powder mixed with binder to manufacture mold insert, and then removing binder and post-treatment for strength. have. Moreover, the current technical level has the economic disadvantage that expensive equipment and materials are required due to the poor precision and surface quality of manufactured starting mold inserts.

Therefore, in order to overcome this problem, the present invention proposes a 3D welding and milling method that is a combination of a cutting method and a lamination method, not a pure cutting method when manufacturing a starting mold insert for injection molding. .

It is an object of the present invention to rapidly produce a starting mold insert, which is required for testing in product development, with high precision.

According to the present invention, the insert having a deep and narrow shape in the manufacture of the starting mold can be processed with a short milling tool without electric discharge machining. Also. If the number of parts to be cut according to the shape is larger than the remaining parts, the total manufacturing time can be shortened than the conventional machining method.

1 is a block diagram of a start mold insert manufacturing apparatus of the present invention.

Figure 2 shows the principle of the three-dimensional welding and milling process of the present invention.

3 is a perspective view of a deep and narrow shaped part made in accordance with the present invention;

4 illustrates a method for protecting a machined inner surface of a cross section formed in accordance with the present invention.

5 is a cross-sectional view of a cavity produced in accordance with the present invention.

Figure 6 is a cross-sectional view of the coolant passage formed therein and the cross-section stacked in accordance with the present invention.

<Explanation of symbols for the main parts of the drawings>

1: processing chamber

10: base material

20: cross section

30: heat resistant material

50: cavity

53: coolant passage

100: welding machine

110: welding gun

115: welding nozzle

120: metal wire feeder

130: metal wire

200: 3-axis NC milling machine

210: axis

300: pneumatic supply device

400: reducer

500: base material preheating device

The method for manufacturing a starting mold insert according to the present invention comprises the steps of cutting the three-dimensional computer model of the starting mold insert to be manufactured to a predetermined thickness to obtain respective cross-sectional data, and generating NC data from the data, and melting the material on the base material. Overlapping a plurality of beads having a width and a height according to the NC data of the corresponding cross section to form the corresponding cross section, and cutting the upper surface according to the NC data to make the height of the cross section constant; The cross-section forming step and the cutting processing step may be sequentially repeated until all cross-sections are laminated.

In addition, the starting mold insert manufacturing method of the present invention is characterized in that it further comprises the step of cutting the outer surface to improve the precision and surface quality after all the cross-section is formed.

In addition, the method of manufacturing a starting mold insert of the present invention further comprises the step of cutting the inner surface after the one or more cross sections are laminated, and the step of filling the inner surface space of the cut cross section with a heat resistant material. It is done.

In addition, the starting mold insert manufacturing method of the present invention is characterized by using a heat-resistant material as a support when forming a cooling water passage therein.

In addition, the starting mold insert manufacturing method of the present invention is characterized by using a different material as the material of each cross section in the stacking of the cross sections.

The apparatus for manufacturing a starting mold insert according to the present invention comprises means for cutting out a three-dimensional computer model of a starting mold insert to be manufactured to a predetermined thickness to obtain respective cross-sectional data, and generating NC data from the data; A metal wire supply device for continuously supplying a wire, a welder drive device for driving the welder according to the NC data, and a device for cutting a cross section formed on a base material by a metal wire bead melted by the welder. Characterized in that.

In addition, the starting mold insert manufacturing apparatus of the present invention is characterized in that it further comprises a base material preheating device for preheating the base material to 200 ℃.

Hereinafter, embodiments of the present invention will be described with reference to the drawings.

Referring to Fig. 1, the start mold insert manufacturing apparatus of the present invention is an NC data generating software (not shown), a welding machine 100, a metal wire supply device 120, and a welding machine driving device as means for generating NC data. (Not shown) and a three-axis NC mill 200. In addition, the starting mold insert manufacturing apparatus additionally includes a pneumatic supply device 300, a reducer 400 and a base material preheating device 500.

Although not shown, the NC data generation software cuts a three-dimensional computer model of the starting mold to be manufactured into 0.1 to 1 mm in thickness, obtains each section data, and then generates machining NC data necessary for three-dimensional welding and milling from the data. .

The welder 100 is a general arc welder, and generally used CO ₂ / MAG or MIG welders, plasma or TIG welders. The welding gun 110 is connected to a wire supply device 120 for supplying the metal wire 130. In addition, the gas mixer 140 and the welding protective gas cylinder 170 are connected to the welder body 150, and the protective gas is supplied from the welder body 150 to the welding gun 110 through the gas supply pipe 160. The metal wire 130 is melted through the welding nozzle 115 together with the welding protective gas. As a metal wire used as a raw material of a mold insert, general mild steel (AWS 5.18) can be used, for example. As the welding protection gas, for example, a mixed gas of argon and carbon dioxide (ratio 80:20) can be used. The wire supply device 120, the gas mixer 140, the welder body 150, and the welding protective gas cylinder 170 are installed outside the processing chamber 1.

The three-axis NC mill 200 is a shaft 210 driven by a driving apparatus (not shown), a face milling tool 220 supported by the shaft, and a cutting oil nozzle 230 for spraying cutting oil to a milling tool during cutting. ). The vertical welding gun 110 is vertically attached next to the axis 210 of the existing three-axis NC mill 200. Therefore, the driving device and the controller for driving the shaft 210 of the existing three-axis NC milling machine 200 can be used as a driving device required for welding, there is no need to install a separate welding machine driving device. In FIG. 1, a driving device and a controller for driving the shaft 210 are not shown.

The pneumatic supply device 300 and the reducer 400 are also installed outside the processing chamber 1, which is compressed to remove spatters that adhere to the welding nozzle 115 after welding. Air is supplied into the nozzle through the supply pipe 310, the reducer 400 serves to suck the smoke generated during welding.

Since the base metal 10 tends to bend a lot due to rapid heating when welding the first cross section, it is necessary to preheat the base material to 200 ° C. by the base material preheating device 500 to prevent this. Such a base material preheating device can be implemented simply by connecting a heating device in the form of a tube to a temperature controller in a copper or iron plate. As the base material 10, a circular metal material with little heat deformation is used.

Referring to Figure 2, the steps of a method of manufacturing a starting mold insert using the manufacturing apparatus described above are shown. Unlike the cutting method of processing a shape from a block, the starting mold insert manufacturing method of the present invention uses a mixed method of stacking closest to a final shape through a lamination method and then performing cutting to obtain a final product.

First, create a three-dimensional computer model of the starting mold to be manufactured using three-dimensional CAD. Then, using NC-only software, thin slices are cut between 0.1 and 1 mm in thickness to obtain each cross-sectional data and then NC data is generated from the data. In addition, process variables directly related to welding and cutting, such as the welding speed for filling the cross section, the spacing between the weld bead and the bead, the cutting speed during cutting to uniformly adjust the height of the cross section, the method for filling the cross section, and The strategy when performing the process such as the welding lamination direction of the process is included in the machining NC data.

After the NC data is generated in this way, as shown in FIG. 2 (a), the material supplied in the form of a metal wire 130 on the base metal 10 is melted by the welding gun 110 to have a predetermined width and height. Excited beads are overlapped in accordance with the NC data of the cross section to form the cross section 20.

Next, in order to make the height of the cross section constant, as shown in Fig. 2 (b), the face milling tool supported on the shaft 210 of the 3-axis NC milling machine 200 according to the NC data thereof 220) for cutting.

After the height of the cross section is precisely adjusted, as shown in FIG. 2C, the next cross section is laminated using the welding gun 110 again.

This lamination and cutting process is repeatedly performed sequentially until all cross sections are laminated to produce the final shape. The outer surface of the laminated section can be processed every time, but it takes a long time, so it is not processed every time, but after all sections have been laminated, i.e., after the final shape is completed, it is cut using an appropriate tool.

In machining, the rough face is first machined using a milling tool with a diameter of 10 mm or more, and then finished again with a pitch tool of about 0.1 mm in order to improve the surface quality.

Referring to FIG. 3, when manufacturing a starting mold insert having a narrow width and a deep shape by conventional pure cutting, a tool having a small diameter and a long diameter should be used, and this may cause the shaking or bending of the tool. In order to solve this problem, after the one or more end faces 20 'are laminated, the inner side is cut using a short tool, and the inner side space of the cut end is filled with the heat resistant material 30. This is a big advantage of the developed process.

That is, when one cross section is completed, the inner surface is processed by selecting a tool suitable for the width of the portion where the empty space is formed. If the shape of the width does not change and repeats with a constant cross section, the inner side may be processed after stacking more cross sections. Since the laminated section has a thickness of 0.1 to 1 mm, it can be processed with a short tool instead of a long tool, thereby reducing bending or shaking of the tool during processing. If the inner surface of the end face 20 'is processed and the new surface is laminated again, molten metal flows down or the spatter splashes to cover the processed part, and thus a method of protecting the same is required. To this end, as shown in FIG. 4A, the inner surface space of the cut end surface is filled with the heat resistant material 30 to protect the cut inner surface. Gypsum, ceramic powder, or the like may be used as the heat resistant material 30.

After the heat-resistant material 30 is solidified, as shown in FIG. 4B, the face milling tool 220 is used to simultaneously process the upper surface of the welded cross section and the heat-resistant material layer to a desired height. At this time, since the heat-resistant material remains in the space of the inner side to protect the inner side already processed when the next layer is laminated. This method is repeated until the final shape is completed.

Thus, the process of dividing and manufacturing can be used when manufacturing the insert cavity of a metal mold | die. If the cavity is large, it can be stacked in half and then machined on the inner side of the welded section using a short tool, protected with a heat-resistant material, and welded back to its final height. In this case, it is possible to manufacture the mold using only the existing cutting tool without electric discharge machining.

The heat resistant material not only protects the machined inner surface, but can also be used as a support when an internal shape is formed in the mold insert. When the mold is manufactured by using three-dimensional welding and milling, a circular or triangular coolant passage is formed freely inside, and when a heat-resistant material is used as a support, a rectangular conformal cooling channel is manufactured. can do. The hollow cooling channel is a cooling water passage required for cooling, which is best suited to the shape of the mold, which can shorten the cooling time during injection molding and reduce the warpage of the parts.

For example, referring to FIG. 5 showing a cross section of the cavity, the cooling water passage 53 may be most suitable for the shape of the cavity 50 to shorten the cooling time during cooling and to minimize the warpage of the injection molded product. It can be seen that.

FIG. 6 shows the laminated section and the cooling water passage formed therein, and the cooling water passage 53 is filled with the heat-resistant material 30. Heat-resistant material is also used as a support when the cooling water passage is formed, in particular, when the cross-section (a) and the cross-section (b) is formed to support from below. In particular, in the configuration of such a cross section, the starting mold insert may be made of a composite material by varying the material for each cross section. For example, the cross section adjacent to the cooling water passage may be laminated with a material having high thermal conductivity such as copper (Cu) to enhance the cooling effect.

According to the machining method combining the existing welding and cutting process according to the present invention, it is possible to produce a shape impossible or difficult to process by the existing pure machining, it is possible to shorten the processing time during manufacturing according to the shape. When cutting inserts with a small width and deep shape, the insert core can be stacked and processed using a combination of the lamination and cutting methods of the present invention. There is an advantage to that. In addition, in the case of the cavity, if the cutting process is performed after lamination close to the final shape, when the amount to be removed is large, the machining time is shorter than that of pure cutting. In addition, when using the lamination method, it is possible to freely create a cooling water passage that is impossible by pure machining, and thus has an effect of efficiently cooling during injection molding.

Claims (7)

Cutting the three-dimensional computer model of the starting mold insert to be manufactured to a predetermined thickness, obtaining each section data, and generating NC data from the data; Melting the material on the base material to overlap a plurality of beads having a constant width and height according to the NC data of the corresponding cross section to form the corresponding cross section; Cutting the upper surface according to the NC data to make the height of the cross section constant; And the step forming step and the cutting step are sequentially repeated until all the sections are laminated. The method of claim 1, further comprising the step of cutting the outer surface after all of the cross sections are laminated. The start mold insert according to claim 1, further comprising: cutting the inner side after the at least one cross section is laminated, and filling the inner side space of the cut end face with a heat resistant material. Manufacturing method. The method of claim 1, wherein a heat resistant material is used as a support when forming a cooling water passage therein. The method according to any one of claims 1 to 4, wherein different materials are used as the material of each cross section in the stacking of the cross sections. delete The method according to any one of claims 1 to 4, further comprising a base material preheating step of preheating the base material to 200 ° C after the NC data generation step.