AU2011242313A1

AU2011242313A1 - Molding method for patternless casting assembly based on bumpy ridge structure

Info

Publication number: AU2011242313A1
Application number: AU2011242313A
Authority: AU
Inventors: Xiaoli Dong; Feng Liu; Zhongde Shan
Original assignee: Advanced Manufacture Technology Center China Academy of Machinery Science and Technology
Current assignee: Advanced Manufacture Technology Center China Academy of Machinery Science and Technology
Priority date: 2010-04-20
Filing date: 2011-03-25
Publication date: 2012-11-29
Anticipated expiration: 2031-03-25
Also published as: DE112011101382T5; ZA201208509B; DE112011101382B4; CN102198487B; CN102198487A; AU2011242313B2; WO2011131074A1

Abstract

A molding method for patternless casting assembly based on bumpy ridge structure is disclosed. A CAD model is subdivided into blocks according to features of a sand mold. A concave-convex bumpy ridge structure is designed on assembly surfaces of subdivided blocks of sand，and an assembly manner of the entire sand mold is determined. The blocks of sand are prepared and machined individually. The blocks of sand with bumpy ridge structure assembly surfaces are assembled. Exterior of the entire sand mold is fastened and prestressed, and the assembly of the sand mold is finished. The method can realize rapid assembly of the blocks of sand and prevent displacement between the blocks of sand.

Description

Unitalen ref.: OP1211-08-0155 PCT original MOLDING METHOD FOR PATTERNLESS CASTING ASSEMBLY BASED ON BUMPY RIDGE STRUCTURE [0001] The present application claims the benefit of priority to Chinese patent application 5 No. 201010150602.7 titled "MOLDING METHOD FOR PATTERNLESS CASTING ASSEMBLY BASED ON BUMPY RIDGE STRUCTURE", filed with the Chinese State Intellectual Property Office on April 20, 2010. The entire disclosure thereof is incorporated herein by reference. FIELD OF THE INVENTION 10 [0002] The present application relates to a mold forming method for large sand mold castings, and belongs to the technical fields of casting and numerical control cutting. BACKGROUND OF THE INVENTION [0003] The manufacturing industry has already become an important part of the national economy, and the industrial added value of the manufacturing industry is 36% of the gross 15 domestic product and is the fourth in the world. The foundry industry is an important part of the manufacturing industry, and especially, the manufacture of large castings is a basis for many mainstay industries, for example, the automobile industry, petrochemical industry, iron and steel industry, electrical industry, shipbuilding industry, textile industry, equipment manufacturing industry and the like, and the developmental level of the foundry industry is a 20 significant symbol for evaluating the comprehensive national strength of a nation. With the diversification and individuation of the product, the needs for single piece or small batch of castings are continuously increasing, particularly at the stage of the design and development of a product for a short production cycle and a fast updating speed. However, the conventional method for producing the mold is hard to satisfy the rapid manufacture of single piece or 25 small batch of parts. [0004] In our country, a conventional manufacturing technology is still used to manufacture single piece or small batch of large castings; and key castings of high quality, particularly the 1 Unitalen ref.: OP1211-08-0155 PCT.original large castings having a complicated production process and high quality requirement, are mainly dependent on import. Compared with industrial developed countries, the production process of large castings in our country has following disadvantages, many production processes, a long production cycle, a high labor intensity due to the manual operation, a huge 5 consumption of raw materials due to a large machining allowance, a low rate of finished products due to the backward mold manufacturing technology, a lot of defects such as shrinkage porosities, shrinkage cavities or cracks, and a large welding repair work. The uncertainty and complexity of the conventional method of producing mold restricts the production of castings, particularly the large castings. 10 [0005] In the molding method of large castings in our country, wood patterns are widely used to perform pit molding. This molding method has a long molding time, in which the wood pattern has a high cost and a low recycle rate. Besides, the molding method has a low casting precision and a poor mechanical performance, thus can not be used in the molding of a complicated molded surface. Generally, a molding cycle of the wood patterns is one month, 15 and the service life of one set of wood patterns is most enough for manufacturing eight pieces of castings (one pattern repair is required in its service life). Even when it only needs to manufacture one piece or two pieces of castings, one set of wood patterns has to be made, which may not only prolong the manufacturing cycle of the castings, but also cause a huge waste of high quality wood. After a pouring process and a cooling process, a lot of finishing 20 work has to be done to the castings produced by the wood pattern molding, which increases the cost and prolongs the manufacturing cycle of the castings. Therefore, there is an urgent need for a new molding method to improve the current situation. [00061 A core assembly molding method can also be used for molding of large castings. In this method, sand cores are made manually or by a core making machine, and then are 25 assembled to be placed in a sandpit for performing a sand core embedding molding. This molding method can reduce the work load for manufacturing the wood pattern tooling, improve the safe reliability and significantly reduce the difficulty in opening mold and shaking sands out for the castings. However, this method has a low molding efficiency, needs a large area, is adapted for the manufacture of large batch of castings, and has a high 30 requirement on the quality of the molding sand, needs a lot of fresh sand, which causes a 2 Unitalen ref.: OP1211-08-0155 PCT original relatively high molding cost, thus is not adapted for the manufacture of singe piece or small batch of large castings. In addition, in the existing core assembly molding technology, the assembling of the sand cores is realized by locating the sand cores via locating points between the sand cores and binding the sand cores via binder, which may cause an inaccurate location 5 and an unstable binding. The sand blocks are assembled via sand matches, i.e. being simply located via a concave-convex structure, and thus may be easily dislocated. SUMMARY OF THE INVENTION [0007] In view of the disadvantages and defects in the prior art, an object of the present application is to provide a rapid method for manufacturing mold of single piece or small batch 10 of large castings, which is a molding method for patternless casting assembly based on a bumpy ridge structure, so as to improve the manufacturing speed and precision of the mold of the large castings, prevent the dislocation of the sand blocks, shorten the production cycle of the castings, save the cost and realize the patternless casting assembling process of large castings. 15 [0008] The technical solutions of the present application are as follows. [0009] A molding method for patternless casting assembly based on a bumpy ridge structure, includes the following steps: a) designing a CAD model in blocks according to features of a mold; b) designing a concave-convex bumpy ridge structure on fitting surfaces of the 20 blocks and an assembly way in relation to locating features of the sand blocks; c) preparing the sand blocks to be machined, with a fastening member being pre-embedded in the sand blocks; d) shaping the sand blocks and machining a bumpy ridge structure on a surface of each of the sand blocks; 25 e) assembling the sand blocks, with the sand blocks being fixed relative to each other by means of the machined bumpy ridge structures; and f) fixing and exerting a pre-tightening force at a periphery of an overall sand mold, and completing the assembly of the sand mold. 3 Unitalen ref.: OP1211-08-0155 PCT-original [00101 Preferably, the sand blocks may be further connected via a mold core binder. [0011] Preferably, the bumpy ridge structure is of a saw-tooth structure with multiple peaks, with a single saw tooth being ranged in width from 5mm to 10mm, and has an error within ±0.5mm in machining precision. s [0012] Preferably, the saw tooth may be a rectangular saw tooth or a triangular saw tooth. [0013] Preferably, the step of fixing and exerting the pre-tightening force at the periphery includes pressing tightly from a plurality of sides by using flat plates. A pressing force may be adjusted by a bolt between the plates, or a bolt pre-embedded in the sand mold. Alternatively, a pressing force is applied to the flat plates by a cylinder additionally provided. 10 [0014] Preferably, a sand core and the sand mold are designed as a whole. [0015] Preferably, a mold joint between the sand blocks may be a horizontal surface, a vertical surface, a stepped surface or an arc surface. [0016] Compared with the prior art, the present application has the following advantages. [0017] 1) The integration of digital design and manufacture of the mold are realized, and a 15 precision of the mold is improved. [0018]2) In the method of the present application, the mold is directly machined by a numerical control machine tool, thereby omitting a process for manufacturing patterns, shortening a production cycle of the whole casting, improving the production efficiency and saving a large amount of wood for manufacturing the patterns. 20 [0019] 3) Compared with the design of the conventional foundry technology, the mold is designed in blocks so as to be more flexible, to have a small machining allowance and to save a large amount of molten metal. BRIEF DESCRIPTION OF THE DRAWINGS [0020] Specific embodiments of the present application will be described in detail in 25 conjunction with drawings hereinafter. [0021] Figure 1 is a clamping device for fixing and assembling a sand mold; 4 Unitalen ref.: OP1211-08-0155 PCT original [0022] Figure 2 is a bumpy ridge structure of a triangular saw-tooth shape; [00231 Figure 3 is a bumpy ridge structure of a rectangular shape; and [00241 Figure 4 is a schematic view of the assembly of the sand mold. [00251 Reference Numerals in Drawings: 5 [002611 exterior clamping bolt 2 exterior locking nut 3 adjustable locating block 4 locking nut of the locating block 5 first adjusting pressure plate 6 second adjusting pressure plate DETAILED DESCRIPTION OF THE EMBODIMENTS [0027] Based on structural features of a casting, a CAD model of a mold is constructed after 10 designing the casting process, such as a gating system, a riser, a venting hole and an iron chill, and a blocking design, and the CAD model is designed into blocks based on features of the mold, for example, determining the number of sand blocks and blocked fashion. A joint surface between the sand blocks may be horizontal or vertical. [0028] Based on the locating feature of the sand blocks, the whole sand mold is divided into 15 four parts (as shown in Fig. 4). As shown in enlarged views of parts "I" and "II" in Fig. 4, the sand blocks are connected by a concave-convex bumpy ridge structure; and the other two joint surfaces are assembled by an inclined surface structure and a stepped structure, respectively. [0029] A virtual assembly is performed to the sand blocks. Specifically, perform a 20 three-dimensional design is performed in relation to the whole mold, and a virtual assembly is performed in a mold assembling process and a core setting process. If an interference phenomenon occurs in the virtual assembly, the blocks of the mold and the assembling way of the blocks have to be readjusted. The CAE simulated experiments of the casting process is then repeatedly performed till appropriate blocking mode and locating way of the mold, as 25 well as the structure of the mold and the mold core are finally determined. [0030] Based on the features of the casting, a single piece of sand block is manufactured by a sand mix forming process, and a fastening member may be pre-embedded in the sand mix 5 Unitalen ref.: OP1211-08-0155 PCT original forming process for assembling of the single piece of sand block. [0031] Depending on the structural features of the sand blocks, a sand mold having a simple contour structure may be machined via a specialized numerical control cutting apparatus, and a sand mold (core) having a complicated shape may be manufactured by a rapid prototyping 5 method or by the combination of the rapid prototyping method and the specialized numerical control cutting apparatus. [0032] During the process of assembling the sand blocks as one unity, the manufactured sand blocks are assembled according to the preceding blocking design of CAD model and are fixed relative to each other via the bumpy ridge structure between the fitting surfaces. At the 10 same time, a pre-tightening force, as shown by an arrow in Fig. 4, is exerted on the periphery of the assembled sand mold as one unity via the clamping device, so as to further prevent the relative dislocation between the sand blocks, and then the assembly of the whole mold is finished. Depending on the features of the assembled mold, partial positions of some fitting portions or the bumpy ridge surfaces may be bonded via binder. 15 [0033] The above description of the present application and the embodiments thereof is illustrative, and is not intend to limit the present application. Other embodiments, made by the person skilled in the art based on the present application without departing from the principle of the present application, are also deemed to fall into the protection scope of the present application. 20 [0034] First additional embodiment: A molding method for patternless assembly based on a bumpy ridge structure, includes the following steps: designing a CAD model in blocks depending on features of a mold; designing a concave-convex bumpy ridge structure on fitting surfaces of the 25 blocks and an assembling way between the blocks, based on locating features of the sand blocks; preparing sand blocks to be machined and pre-embedding a fastening member in the sand blocks; shaping the sand blocks and machining a bumpy ridge structure on a surface 6 Unitalen ref.: OP1211-08-0155 PCT original of each of the sand blocks; assembling the sand blocks, with the sand blocks being fixed relative to each other via the machined bumpy ridge structure, and being connected via a mold core binder as needed; and 5 fixing and exerting a pre-tightening force at a periphery of an overall sand mold, and completing the assembly of the sand mold. [0035] Second additional embodiment: In the molding method for patternless assembly based on the bumpy ridge structure according to the first additional embodiment, the bumpy ridge structure is directed to a 10 multi-peak structure, including but not limited to, a rectangular saw-tooth shape and a triangular saw-tooth shape. A single peak has a width ranged from 5mm to 10mm, and the bumpy ridge structure has an error within ±0.5mm in machining precision. [0036] Third additional embodiment: In the molding method for patternless assembly based on the bumpy ridge structure 15 according to the second additional embodiment, fixing and exerting the pre-tightening force at the periphery may be implemented by pressing tightly from a plurality of sides with flat plates. A pressing force may be adjusted by a bolt between the plates, or a bolt pre-embedded in the sand mold. Alternatively, a pressing force is applied to the flat plates by a cylinder additionally provided. 20 [0037] Fourth additional embodiment: In the molding method for patternless assembly based on the bumpy ridge structure according to the third additional embodiment, the blocking design of the CAD mold is different from the conventional design of the casting process in that, for example, simplifying the design of a sand core because the sand core and the sand mold as a whole 25 are designed; and a mold joint between the sand blocks may be a horizontal surface, a vertical surface, a stepped surface, or an arc surface, etc. 7

Claims

1. A molding method for patternless assembly based on a bumpy ridge structure, comprising the following steps: a) designing a CAD model in blocks depending on features of a mold; 5 b) designing a concave-convex bumpy ridge structure on fitting surfaces of the blocks and an assembling way between the blocks based on locating features of the sand blocks; c) preparing sand blocks to be machined and pre-embedding a fastening member in the sand blocks; 10 d) shaping the sand blocks and machining a bumpy ridge structure on a surface of each of the sand blocks; e) assembling the sand blocks, with the sand blocks being fixed relative to each other by means of the machined bumpy ridge structure; and f) fixing and exerting a pre-tightening force at a periphery of an overall sand 15 mold, and completing the assembly of the sand mold.

2. The molding method for patternless assembly based on the bumpy ridge structure according to claim 1, wherein the sand blocks are further connected via a mold core binder.

3. The molding method for patternless assembly based on the bumpy ridge structure according to claim 2, wherein, the bumpy ridge structure is a saw-tooth structure having 20 multiple peaks, with a single saw tooth being ranged in width from 5mm to 10mm, and has an error within ±0.5mm in machining precision.

4. The molding method for patternless assembly based on the bumpy ridge structure according to claim 3, wherein, the saw-tooth is rectangular or triangular in shape.

5. The molding method for patternless assembly based on the bumpy ridge structure 25 according to claim 1, wherein, the step of fixing and exerting the pre-tightening force at the periphery comprises pressing tightly from a plurality of sides by using flat plates; and a 8 Unitalen ref.: OP1211-08-0155 PCT original pressing force is adjustable by a bolt between the plates or a bolt pre-embedded in the sand mold, or is applied to the flat plates by a cylinder additionally provided.

6. The molding method for patternless assembly based on the bumpy ridge structure according to claim 1, wherein, a sand core and the sand mold are designed as a whole. 5

7. The molding method for patternless assembly based on the bumpy ridge structure according to claim 1, wherein, a mold joint between the sand blocks is a horizontal surface, a vertical surface, a stepped surface or an arc surface. 9