Claims:WE CLAIM:
1. A die set and core box set for manufacturing aluminum alloy blower for turbo generator exciter, the die set and core box set comprising:
a die having a top half and a bottom half;
a sand core placed inside the top half and the bottom half of the die, wherein the top half and the bottom half of the die along with the sand core makes the required cavity for molten metal to fill and make a blower casting;
a core box set having top and bottom halves; and
a core box ring used in core box assembly to make the sand core.
2. The die set and core box set as claimed in claim 1, wherein the die defines proper cooling circuits allowing the solidification path of alloy.
3. The die set and core box set as claimed in claim 1, wherein core sand is blown into the core box and then hardened by passing an amine catalyst in a carrier gas.
4. The die set and core box set as claimed in claim 1, wherein the sand core includes a first refractory coating, such as of silica, with an inorganic binding agent of colloidal silica and a clay such as kaolin, and a second or top coating of a refractory material containing zircon and an organic binding agent.
5. The die set and core box set as claimed in claim 1, wherein the core box ring holds the sand in the core shooter while formation of hardened sand core.
6. The die set and core box set as claimed in claim 3, wherein the core sand is silica sand mixed with a two-part binder consisting of a phenol formaldehyde resin and a reactive isocyanate.
7. The die set and core box set as claimed in claim 2, wherein the allow is Aluminium-silicon Alloy Grade EN AC-AlSi9MgWa (EN AC-43300).
8. The die set and core box set as claimed in claim 1, wherein the blower is made through achievement of elongation > 4%, yield strength > 180MPa, tensile strength > 200 MPa, radiography level I, and Globular micro-structure in the casting.
, Description:DIE SET AND CORE BOX SET FOR MANUFACTURING ALUMINUM ALLOY BLOWER FOR TURBO GENERATOR EXCITER
FIELD OF INVENTION
[001] The present invention relates to a Die set and core box set for manufacturing of Aluminum alloy Blower for turbo generator exciter using low pressure die casting method. The invention specifically relates to manufacturing of the Aluminum alloy blower as per the drawing and to meet stringent quality requirements.

BACKGROUND OF THE INVENTION

[002] Blower in the turbo generator is used for cooling of exciter and rotates with generator shaft. Blowers are made of Aluminium alloy and repeated failure of the blower has been reported during operation as well as plant testing. Earlier the blowers used to be made by sand casting. To improve the quality of the blower and achieve the required microstructure, radiographic quality and mechanical strength, low pressure die casting method is used for manufacturing of the blower. Accordingly, the die set and core box set is developed for casting of the blower in accordance with an embodiment of the present disclosure.

[003] Among the innovative and conventional foundry processes for Aluminium alloys, low pressure die casting is characterised by several advantages, including high yield, excellent control of operative parameters, good metallurgical and technological quality. This process is often (and incorrectly) associated only to the production of automotive wheels, while it is improving its potential both towards other automotive components and non-automotive parts.

[004] The increasing number of applications and of products is the best proof of the success of Aluminium alloys foundry. This is probably one of the most dynamic fields inside manufacturing and engineering. The well-known advantages associated to the use of Aluminium alloys (light weight, good mechanical behaviour, good corrosion resistance, etc.) constitute the driving force for the introduction, on one hand, of new applications and design and, on the other hand, for the development of new processing solutions. Various processes are now competing, to achieve both economically and technologically advantageous production of Aluminium alloys castings.

[005] Among the most interesting processes, low pressure die casting is certainly worth mentioning, thanks to its peculiarities, allowing, in several cases, an excellent compromise between quality, costs, productivity, geometrical feasibility. The principle of this process is quite simple: the permanent die and the filling system are placed over the furnace containing the molten alloy (Refer Fig. 1). The filling of the cavity is obtained by forcing (by means of a pressurized gas, typically ranging from 0.3 to 1.5 bars) the molten metal to rise into a ceramic tube (which is called stalk), which connects the die to the furnace. The pressure used is roughly equivalent to 2 meters of an Aluminum column.

[006] The advantages of low pressure die casting process are several:
- the high yield achievable (typically over 90%)
- the reduction of machining costs, thanks to the absence of feeders, - the excellent control of process parameters which can be obtained, with a high degree of automation,
- the good metallurgical quality, thanks to a homogeneous filling and a controlled solidification dynamic, resulting in good mechanical and technological properties of the castings.

[007] The applications of low pressure die casting in the automotive field are several, even if this process is often (and reductively) associated only to the production of wheels. Some examples of low pressure die casting products are provided in Fig. 2.

[008] United States Patent publication US6146094A provides - Reduction of air resistance which acts on the conventional motor-driven blower is limited because crushed protrusions are formed on the surface of the plate of the impeller of the conventional motor-driven blower, and this air resistance is a significant impediment to an increase of the operating speed of the motor-driven blower. Thus, an impeller is provided which comprises a front plate having a suction opening, a back plate disposed opposite to the front plate, and a plurality of blades disposed between the front plate and the back plate. At least either the front plate or the back plate is formed integrally with the blades.

[009] According to a first aspect of the US6146094A invention, a motor-driven blower comprises an electric motor enclosed in a housing, an impeller fixedly mounted on a rotating shaft included in the electric motor, stationary guide blades disposed downstream of the impeller, and a fan casing covering the impeller and the stationary guide blades; wherein the impeller comprises a front plate having a suction opening, a back plate disposed opposite to the front plate, and a plurality of blades disposed between the front plate and the back plate, with at least either the front plate or the back plate being formed integrally with the blades.

[0010] According to a second aspect of the US6146094A invention, an impeller comprises a front plate, a back plate disposed opposite to the front plate, and a plurality of blades disposed between the front plate and the back plate; wherein at least either the front plate or the back plate is formed integrally with the blades, a brazing metal layer is formed on a surface of the other plate not formed integrally with the blades, and the other plate is brazed to the blades by way of the brazing metal layer.

[0011] According to the US6146094A invention, the impeller is formed as a monolithic structure and does not have any crushed projections. Therefore, the impeller of the present invention is not subject to air resistance that may be produced if the impeller has crushed projections and does not generate any noise which may be generated if the impeller has crushed projections. A motor-driven blower provided with the impeller of the present invention is able to operate at an increased operating speed and to improve the efficiency of suction of a vacuum cleaner.

[0012] However, in accordance with an embodiment of the present disclosure, in the present application / invention brazing or any sort of joining is avoided and fully integral blower has been made using the critically designed die cavities and sand core boxes.

OBJECTS OF THE INVENTION

[0013] The principal object of the present invention is to provide a Die set and core box set for manufacturing of high quality Aluminum alloy Blower for turbo-generator exciter using low pressure die casting method.

SUMMARY OF THE INVENTION

[0014] The present invention relates to a die set and core box set for manufacturing aluminum alloy blower for turbo generator exciter. The die set and core box set including a die having a top half and a bottom half; a sand core placed inside the top half and the bottom half of the die, wherein the top half and the bottom half of the die along with the sand core makes the required cavity for molten metal to fill and make a blower casting; a core box set having top and bottom halves; and a core box ring used in core box assembly to make the sand core.

BRIEF DESCRIPTION OF THE ACCOMPANYING DRAWINGS

[0015] Further objects and advantages of this invention will be more apparent from the ensuing description when read in conjunction with the accompanying drawings of the exemplary embodiments and wherein:

Fig.1 shows: a typical permanent die and the filling system, placed over the furnace containing the molten alloy.
Fig.2 shows: some examples of low pressure die casting products.
Fig.3 shows: the drawing of Blower
Fig.4 shows: the 3d model of Blower
Fig.5 shows: top die cavity
Fig.6 shows: bottom die cavity
Fig. 7 shows: Core box ring
Fig.8 shows: the bottom half of the core box
Fig.9 shows: the top half of the core box
Fig.10 shows: the core box set assembly view
Fig.11 shows: the sand core made using the core box set assembly
Fig.12 shows: the die and core box assembly for casting
Fig.13 shows: sectional view of Die and core assembly for casting

DETAIL DESCRIPTION OF THE PREFERRED EMBODIMENTS OF THE PRESENT INVENTION WITH REFERENCE TO THE ACCOMPANYING DRAWINGS

[0016] The present invention now be described more specifically with reference to the following specification.

[0017] It should be noted that the description and figures merely illustrate the principles of the present subject matter. It should be appreciated by those skilled in the art that conception and specific embodiment disclosed may be readily utilized as a basis for modifying or designing other structures for carrying out the same purposes of the present subject matter. It should also be appreciated by those skilled in the art that by devising various arrangements that, although not explicitly described or shown herein, embody the principles of the present subject matter and are included within its spirit and scope. Furthermore, all examples recited herein are principally intended expressly to be for pedagogical purposes to aid the reader in understanding the principles of the present subject matter and the concepts contributed by the inventor(s) to furthering the art and are to be construed as being without limitation to such specifically recited examples and conditions. The novel features which are believed to be characteristic of the present subject matter, both as to its organization and method of operation, together with further objects and advantages will be better understood from the following description when considered in connection with the accompanying figures.

[0018] In accordance with an embodiment of the present disclosure, reference is made to the following figures and associated components.

[0019] Blower in the turbo generator is used for cooling of exciter and rotates with generator shaft. Blowers are made of Aluminium alloy and repeated failure of the blower has been reported during operation as well as plant testing. Earlier the blowers used to be made by sand casting. In order to improve the quality of the blower and achieve the required microstructure, radiographic quality and mechanical strength, low pressure die casting method is used for manufacturing of the Blower. Accordingly, a die set and core box set in accordance with an embodiment of the present disclosure is developed for casting of the blower. The invention specifically relates to manufacturing of the blowers as per the drawing and to meet stringent quality requirements.

[0020] Fig. 3 shows the drawing of the blower and die and core boxes are made with reference to this drawing. The Die and core box are developed to make high quality casting of aluminum alloy blower using low pressure die casting as per the drawing given in the fig.3. In an embodiment, the die is designed to control by means of proper cooling circuits allowing the solidification path of the alloy. The massive region of the casting has to be the last one to solidify and must be placed near to the stalk, which acts as a “virtual” feeder and allows to avoid the use of conventional feeders, thus improving the yield of the process, which becomes significantly high. Casting simulation software is used for design of die and gating system. The top and bottom halves of the die are shown in fig.5 and fig.6. The Die has two components without envelope of the blower and sand core is placed inside the dies. Dies along with sand core makes the required cavity for molten metal to fill and make the blower casting.

[0021] Once the die cavity is filled, the overpressure in the furnace (Refer Fig. 1) is removed, and the residual molten metal in the tube flows again towards the furnace. The various parts of the die are then separated, and the casting is finally extracted Specific attention must be paid to the design of the die, to control by means of proper cooling circuits, the solidification path of the alloy. The massive region of the casting has to be the last one to solidify and must be placed near to the stalk, which acts as a “virtual” feeder and allows to avoid the use of conventional feeders, thus improving the yield of the process, which becomes significantly high. The low injection velocity and the relatively high cycle time lead to a good control of the fluid-dynamics of the process, avoiding the defects originated by turbulence phenomena. Castings up to 70 kg weight can be produced, with tolerances of 0.3-0.6 %.

[0022] The die can be design for the production of a single casting or for multiple castings, according to the size required and to the characteristics of the machine.

[0023] However, it should be remembered that the hollow inside part of a casting is formed by a core, analogous with an apple core. Such shapes in sand are formed in a special sort of pattern called a core box. Specific attention has to be paid to the design of the core box.

[0024] Core sand (silica sand mixed with a two-part binder consisting of a phenol formaldehyde resin and a reactive isocyanate) to be blown into a core box and then hardened by passing an amine catalyst in a carrier gas through it. Thus the core is more-or-less fully hardened by the time it is ejected from the box. This provides high productivity and high accuracy.

[0025] A resin-bonded sand core for pressure die casting methods having a first refractory coating, such as of silica, with an inorganic binding agent of colloidal silica and a clay such as kaolin, and a second or top coating of a refractory material containing zircon and an organic binding agent, which combination of these two different coatings enables the bonded sand core to have high pressure and temperature resistance, good washout resistance, freedom from surface penetration, and good shake-out properties.

[0026] Specific attention also paid to the design of the core box - Core box components includes two half. Core box two half along with core box ring around them creates cavity for filling of sand core in core shooter. Core box ring is used in core box assembly to make the sand core. The core box ring holds the sand in the core shooter while formation of hardened sand core. And the hardened sand core is formed. Core box set is used for making of core for the hollow inside part of the fan/casting. The top and bottom halves of the core box are shown in fig.8 and fig.9. Core sand (silica sand mixed with a two-part binder consisting of a phenol formaldehyde resin and a reactive isocyanate) is blown into a core box and then hardened by passing an amine catalyst in a carrier gas through it. Thus, the core is more-or-less fully hardened by the time it is ejected from the box. This provides high productivity and high accuracy.

[0027] The core is placed in the die. The permanent die and the filling system are placed over the furnace containing the molten alloy (Fig. 1). Once the die cavity is filled, the overpressure in the furnace is removed, and the residual molten metal in the tube flows again towards the furnace. The various parts of the die are then separated, and the casting is finally extracted.

[0028] The castings are suitably stress relieved and heat treated to get the required microstructure and mechanical strength. In an example, Die and core box set is used for casting of 11 numbers of blowers for turbo-generator exciter.

[0029] Die and core box set for low pressure die casting of Aluminium-silicon Alloy Grade EN AC-AlSi9MgWa (EN AC-43300) blower. Low pressure die casting of blower while achieving the Component Geometry and Dimensions as per drawing. Achievement of elongation > 4% in the casting. Achievement of yield strength > 180MPa in the casting. Achievement of tensile strength > 200 MPa in the casting. Achievement of radiography level I in the casting. Achievement of Globular micro-structure in the casting.

[0030] It is to be noted that the present invention is susceptible to modifications, adaptations and changes by those skilled in the art. Such variant embodiments employing the concepts and features of this invention are intended to be within the scope of the present invention, which is further set forth under the following claims.