FIELD OF THE INVENTION
00001. The present invention discloses a process to fabricate the impeller by
using 3D printing and flexible moulding technique, or more particularly to a
method for fabrication of impeller with complex blade profiles which provides
high dimensional accuracy.
BACKGROUND OF THE INVENTION
2. An impeller is a rotating component of a centrifugal pump and is composed of vanes (or blades), shroud and a hub. As the impeller rotates, the fluid is drawn into the blade passage at the impeller eye, the centre of the impeller. The inlet pipe is axial and therefore fluid enters the impeller with very little whirl or tangential component of velocity and flows outwards in the direction of the blades. The fluid receives energy from the impeller while flowing through it and is discharged with increased pressure and velocity into the casing.
3. Impellers are available in open, semi- open and closed designs. In case of open impeller, the vanes are attached to the hub. There is no shroud to support the vanes. For semi-open impeller, the vanes are attached to the hub with a shroud on one side of the impeller. However, in case of closed impeller the vanes are attached to the hub with a shroud on either side of the impeller. These designs maintain pump efficiency by the use of close clearance wear rings. A properly designed impeller minimizes turbulence and maximizes efficiency. In all above designs, the closed impeller is a more complicated and expensive to design and difficult to fabricate with dimensional accuracy.
4. For any impeller, blade wrap angle is very crucial parameter. An increase in blade wrap angle would lead to a longer flow passage between the

blades and thus a significant rise in friction loss. On the contrary, a small blade angle will generate a short flow passage but result in a poor control on the flow in impeller arousing separation loss probably. Therefore, the blade wrap angle is a key parameter for flow pattern in impeller and hence performance of pump.
5. Impellers can be fabricated by variety of methods, conventional sand casting process is widely used in foundry practice. In this process, to produce the desired profile of vanes (blade), first wood pattern is made through skilled drafting /machining process. After that sand is packed around the wood patterns to make the sand core of blade profile. The fabricated sand core having desired blade profiles is assembled together and kept inside the mould cavity. The molten metal is poured in to the mold cavity and allowed for solidification to get the final product. However, complex blade profile with dimensional accuracy cannot be produced with this method. In addition to this, assembling of sand core of blade profile may also lead to dimensional variation which may lead to rejection of casting.
6. To fabricate the complex profile impeller with dimensional accuracy, hub, vanes and shroud can be made separately by machining process. After that vanes can be welded /bonded to hub and shroud to get the final component with dimensional accuracy. However, for this kind of impellers a high stress occurs at part of the joints between the blades and the shroud when the shrouded impeller is rotated, the developed stress could break the joints between the blades and the shroud, thus possibly impairing the reliability of the shrouded impeller.
7. In another manufacturing method, the impeller parts (i.e. hub, vanes and shroud) cast separately and then these pieces are placed in appropriate position relative to one another by means of a five-axis machine. Once in proper position, the pieces are then electron-beam welded together. However, use of a five-axis machine, and the process of electron-beam welding are quite expensive

and require long lead times for production. In addition to this, fabricated impeller may lead to crevice erosion, since electron beam welding does not make a complete joint from one side of each vane to the other.
8. Document U.S. Pat. No. 5,438,755 describes a method of making a shrouded impeller using three-dimensional Computer Numerical Control (CNC) milling. The method of the patent involves fabricating a shrouded impeller from a single blank using four machining steps. These steps include: turning and boring a rough forging to an impeller profile; removing material from the passageways of the impeller using a three-dimensional CNC milling machine; removing material in direct line of sight from the outside diameter of the impeller, and forming a hole through a central zone of each impeller passageway. However, three-dimensional CNC milling cannot produce the complex blade profiles.
9. Another method to produced impellers with dimensional accuracy is lost wax (or investment casting) method. In this method, first of all an aluminum mold is prepared, which is the negative of the piece that has to be produced, then it is injected with wax at about 130°C to produce a piece which is identical to metallic one. After this the wax model is coated with ceramic layers and allowed to dry for a few days. Finally this "ceramic" container is opened on one side to get the negative cast of the item to be produced. Finally metal is poured inside ceramic container to get the desired component.
10. Impellers also can be manufactured by metal subtractive (machining), or metal additive (3D printing, laser sintering) methods with precise dimensional accuracy. The subtractive route implies removal of material, but limited to simple shapes. However, this limitation is overcome by additive manufacturing, which allows a complex shape to be produced directly and automatically from its 3D Computer Aided Design (CAD model). In case of metal additive manufacturing a high-power energy source (laser or electron beam), selectively melts metal powder, layer by layer, to create the final part. The high cost of these systems currently

justifies their use only for critical applications like aerospace and defense applications.
11. Generally, shortcomings of the prior art arise from (1) difficulties in maintaining uniformity in mass production and (2) lack of adequate dimensional accuracy in complex patterns for use in current impeller technology. Additionally, modifying the shape of an impeller blade to achieve better impeller performance has many costs associated with the design, testing, and tooling required to arrive at the desired blade configuration. Thus, there is a need for an improved method for fabrication of impeller with complex blade profiles in more efficient and economical way.
12. However, in case of conventional sand casting, the gap among the vanes varies during the assembling of sand core structure, which leads to variation in profile and hence rejection of casting.
13. In the present method, all the vanes are created in a single preform, which helps in maintaining the desired blade profile over the shroud. Present invention also avoids all the complicated steps of conventional sand casting, electron-beam welding, and lost wax (or investment) casting process to fabricate the complex shape impeller.
OBJECTS OF THE INVENTION
14. It is therefore the primary object of the present invention to provide a process for fabrication of impeller, which can provide impellers with complex profile with high dimensional accuracy.
15. Another object of the present invention to provide a process for fabrication of impeller, which avoids Computer Numerical Control (CNC) process to fabricate the impellers.
16. Yet another object of the present invention to provide a process for fabrication of impeller, which produces curved shaped blade or vanes.

17. Further object of the present invention to provide a process for fabrication of impeller, which avoids complicated steps of sand casting on investment casting to fabricate the complex shape impellers.
18. Another object of the present invention to provide a process for fabrication of impeller, which can produce any complex blade profile over the shroud.
19. Yet another object of the present invention to provide a process for fabrication of impeller, where die can be re-used to fabricate the number of impellers.
20. Further object of the present invention to provide a process for fabrication of impeller, which is economic, fast and accurate.
SUMMARY OF THE INVENTION
21. One or more drawbacks of conventional method are overcome, and additional advantages are provided through the composition as claimed in the present disclosure. Additional features and advantages are realized through the technicalities of the present disclosure. Other embodiments and aspects of the disclosure are described in details herein and are considered to be part of the claimed disclosure.
22. A method for fabrication of impeller with complex blade profiles comprises the steps of:
i) generation of 3D molded of impeller by Computer Aided Design (CAD)/ Computer-Aided Manufacturing (CAM process) (step 100); ii) printing of negative impression of blade profile by 3D printing (step 101); iii) creation of flexible mould by using 3D printed negative blade profile (step
102); iv) cement preform is created by using fabricated flexible mould (step 103);
v) assembling of cement preform in mould cavity (step 104); vi) pouring of metal inside the cement preform to get the final product (step 105)

23. Various objects, features, aspects, and advantages of the inventive subject matter will become more apparent from the following detailed description of preferred embodiments, alongwith the accompanying drawing figures.
24. It is to be understood that the aspects and embodiments of the disclosure described above may be used in any combination with each other. Several of the aspects and embodiments may be combined to form a further embodiment of the disclosure.
25. The foregoing summary is illustrative only and is not intended to be in any way limiting. In addition to the illustrative aspects, embodiments, and features described above, further aspects, embodiments, and features will become apparent by reference to the drawings and the following detailed description.
BRIEF DESCRIPTION OF THE ACCOMPANYING DRAWINGS
26. The illustrated embodiments of the subject matter will be best understood by reference to the drawings, wherein like parts are designated by like numerals throughout. The following description is intended only by way of example, and simply illustrates certain selected embodiments of devices, systems, and processes that are consistent with the subject matter as claimed herein, wherein:
27. Figure. 1 Shows the flow chart to fabricate the impeller using 3D printing and flexible moulding technique.

28. Figure. 2 Shows the 3D printed negative impression of blade profile. The printed profile clearly exhibits the negative impression of vanes with high dimensional accuracy.
29. Figure. 3 Shows the flexible silicone rubber mould. To create flexible mould using 3D printed negative blade profile, Silicone rubber is poured inside the 3D printed profile. From the image it is evident that precise profile of vanes can be achieved with the help of 3D printing.

30. Figure. 4 Shows the cement preform having the negative blade profiles. In the present method all vanes are created in single preform, which helps in maintaining the complex blade profiles.
31. Figure. 5 Shows the arrangement to fabricate the impeller using cement preform. To make the desired shape impeller, cement preform is kept inside the mould cavity Fig. 5 (a). Cavity in closed condition is shown in Fig. 5 (b). The liquid metal is poured through a pouring port in the mold, after hardening of the cast metal into the mold the mold is removed to get the impeller.
32. Figure. 6 Shows the fabricated impeller using 3D printing and flexible moulding technique.
000033. The figures depict embodiments of the disclosure for purposes of
illustration only. One skilled in the art will readily recognize from the following
description that alternative embodiments of the methods illustrated herein may
be employed without departing from the principles of the disclosure described
herein.
DETAILED DESCRIPTION OF THE PRESENT INVENTION
34. While the embodiments of the disclosure are subject to various modifications and alternative forms, specific embodiment thereof have been shown by way the figures and will be described below. It should be understood, however, that it is not intended to limit the disclosure to the particular forms disclosed, but on the contrary, the disclosure is to cover all modifications, equivalents and alternative falling within the scope of the disclosure.
35. It is to be noted that a person skilled in the art would be motivated from the present disclosure to arrive at a method of fabrication of impeller with complex blade. However, such modifications should be construed within the scope of the disclosure. Accordingly, the drawings illustrate only those specific details that are pertinent to understand the embodiments of the present

disclosure, so as not to obscure the disclosure with details that will be clear to those of ordinary skill in the art having benefit of the description herein.
36. As used in the description herein and throughout the claims that follow, the meaning of “a”, “an”, and “the” includes plural reference unless the context clearly dictates otherwise. Also, as used in the description herein, the meaning of “in” includes “in” and “on” unless the context clearly dictates otherwise.
37. The terms “comprises”, “comprising”, or any other variations thereof used in the disclosure, are intended to cover a non-exclusive inclusion, such that a method, system, assembly, thermoelectric power, generator, thermal energy that comprises a list of components does not include only those components but may include other components not expressly listed or inherent to such method, or assembly, or method. In other words, one or more elements in a system or device proceeded by “comprises…..a “does not, without more constraints, preclude the existence of other elements or additional elements in the system, apparatus or device.
38. The present subject matter relates to a method of fabrication of impeller with complex blade profiles, which provides high dimensional accuracy and better performance.
39. 3D printing is used to create such flexible mould.
40. Fig 1 shows a flow chart for the fabrication process as claimed hereinafter by using 3D printing and flexible mould technique.
41. The fabrication method comprises the steps of:
i) generation of 3D molded of impeller by CAD/CAM process (step 100);
ii) printing of negative impression of blade profile by 3D printing (step 101); iii) creation of flexible mould by using 3D printed negative blade profile (step
102); iv) cement preform is created by using fabricated flexible mould (step 103);

v) assembling of cement preform in mould cavity (step 104); and vi) pouring of metal inside the cement preform to get the final product (step 105).
42. In step 101, negative impression of blade profile is printed using acrylonitrile butadiene styrene (ABS) polymer. The advantage of ABS is that it is a light and rigid material which is a good shock absorber also. It is a co-polymer made by polymerizing styrene and acrylonitrile in the presence of polybutadiene. Other materials like, polycarbonates, polycaprolactone, and polyphenylsulfones also can be used for 3D printing.
43. Fig 2 illustrates the 3D printed negative impression of blade profile.
44. The printed profile clearly exhibits the negative impression of vanes (blades). The vanes are in curved shape and extended from centre to outer periphery and are equi-spaced from each other. The number of vanes in printed profile may vary, depending on the type of impeller. The angle of vanes over the shroud is similar to all vanes.
45. The flexible mould is created (step 102) by pouring of silicone rubber inside the 3D printed profile and get cured to have the desired profile. Fig 3 shows the fabricated flexible mould.
46. The fabricated mould represents the original blade profile. From the figure, it is evident that precise angled profile of vanes can be achieved with the help of 3D printing. Any complicated shape can be printed and can be converted to get the desired flexible mould.
47. Step 103 provides the formation of cement preform by using flexible mould. Fig 4 illustrates the fabricated cement preform.
48. All blades having same profiles are created in single preform, which helps in maintaining the complex blade profile.
49. After that cement preform is kept inside the mould cavity to give the desired shape (as show in Fig 5a).

50. Fig 5b illustrates the closed cavity.
51. In step 105, the liquid metal is poured through a pouring port in the mold after hardening the cast metal into the mold.
52. After that, the mold got removed. Fig 6 shows the fabricated impeller. Any number of cement preforms can be made by the flexible mould. However, in other technique, the moulds have to be produced again and again and then the 3D printing and flexible moulding techniques is not only accurate but also becomes faster.
53. The non-limiting advantage of the present invention are given below:

> A method of fabrication of impeller, which is fabricated by 3D printing and flexible moulding technique;
> The impeller has curved shape blade (or vanes) profile;
> The curved shape blade profile is created using 3D printing method;
> 3D printing used in this process can create any complex profile with high dimensional accuracy;
> 3D printing/ flexible moulding avoids the complicated steps of conventional sand casting to fabricate the complex shape impellers;
> 3D printing/ flexible moulding avoids the complicated steps of investment casting to fabricate the complex shape impellers;
> 3D printing/ flexible moulding avoids the complicated steps of conventional sand casting to fabricate the complex shape impellers;
> 3D printing/ flexible moulding also avoids the use of CNC to fabricate the complex shape impellers;
> 3D printing/ flexible moulding checks the welding of vanes over the shroud;
> The impeller can be fabricated in single step;
> Any complex shape of vanes with high dimensional accuracy can be created over the shroud;
> The flexible mould can be used repeatedly to fabricate the impellers.

> The method as claimed hereinafter avoids the machining, and wood pattern making to fabricate the impeller; and
> Can fabricate any type of impeller, which is difficult to fabricate by CNC process.

54. Each of the appended claims defines a separate invention, which for infringement purposes is recognized as including equivalents to the various elements or limitations specified in the claims. Depending on the context, all references below to the “invention” may in some cases refer to certain specific embodiments only. In other cases, it will be recognized that references to the “invention” will refer to subject matter recited in one or more, but not necessarily all, of the claims.
55. Groupings of alternative elements or embodiments of the invention disclosed herein are not to be construed as limitations. Each group member can be referred to and claimed individually or in any combination with other members of the group or other elements found herein. One or more members of a group can be included in, or deleted from, a group for reasons of convenience and/or patentability. When any such inclusion or deletion occurs, the specification is herein deemed to contain the group as modified thus fulfilling the written description of all groups used in the appended claims.
000056. The present disclosure provides a method of fabrication of impeller with
complex blade.
Equivalents:
000057. With respect to the use of substantially any plural and/or singular
terms herein, those having skill in the art can translate from the plural to the
singular and/or from the singular to the plural as is appropriate to the context
and/or application. The various singular/plural permutations may be expressly
set forth herein for sake of clarity.

000058. It will be understood by those within the art that, in general, terms
used herein, and especially in the appended claims (e.g., bodies of the appended
claims) are generally intended as “open” terms (e.g., the term “including” should
be interpreted as “including but not limited to”, the term “having” should be
interpreted as “having at least”, the term “includes” should be interpreted as
“includes but is not limited to”, etc.). It will be further understood by those within
the art that if a specific number of an introduced claim recitation is intended,
such an intent will be explicitly recited in the claim, and in the absence of such
recitation no such intent is present. For example, as an aid to understanding, the
following appended claims may contain usage of the introductory phrases “at
least one” and “one or more” to introduce claim recitations. However, the use of
such phrases should not be construed to imply that the introduction of a claim
recitation by the indefinite articles “a” or “an” limits any particular claim
containing such introduced claim recitation to inventions containing only one
such recitation, even when the same claim includes the introductory phrases “one
or more” or “at least one” and indefinite articles such as “a” or “an” (e.g., “a”
and/or “an” should typically be interpreted to mean “at least one” or “one or
more”); the same holds true for the use of definite articles used to introduce claim
recitations. In addition, eve it a specific number of an introduced claim recitation
is explicitly recited, those skilled in the art will recognize that such recitation
should typically be interpreted to mean at least the recited number (e.g., the bare
recitation of “two recitations”, without other modifiers, typically means at least
two recitations, or two or more recitations).
000059. The terminology used herein is for the purpose of describing particular
embodiments only and is not intended to be limiting of the present disclosure. It
will be appreciated that several of the above-disclosed and other features and
functions, or alternatives thereof, may be combined into other systems or
applications. Various presently unforeseen or unanticipated alternatives,
modifications, variations, or improvements therein may subsequently be made by
those skilled in the art without departing from the scope of the present disclosure
as encompassed by the following claims.

60. The claims, as originally presented and as they may be amended, encompass variations, alternatives, modifications, improvements, equivalents, and substantial equivalents of the embodiments and teachings disclosed herein, including those that are presently unforeseen or unappreciated, and that, for example, may arise from applicants/patentees and others.
61. While various aspects and embodiments have been disclosed herein, other aspects and embodiments will be apparent to those skilled in the art. The various aspects and embodiments disclosed herein are for purposes of illustration and are not intended to be limiting, with the true scope and spirit being indicated by the following claims.

WE CLAIM :
1. A method for fabrication of impeller with complex blade profiles comprises the
steps of:
i) generation of 3D molded of impeller by CAD/CAM process (step 100); ii) printing of negative impression of blade profile by 3D printing (step 101); iii) creation of flexible mould by using 3D printed negative blade profile (step
102); iv) cement preform is created by using fabricated flexible mould (step 103);
v) assembling of cement preform in mould cavity (step 104); and vi) pouring of metal inside the cement preform to get the final product (step 105).
2. The method for fabrication of impeller with complex blade profiles as claimed in claim 1, wherein the negative impression of blade profile is printed with the materials selected from acrylonitrile butadiene styrene (ABS) polymer, polycarbonates, polycaprolactone and polyphenylsulfones.
3. The method for fabrication of impeller with complex blade profiles as claimed in claim 1, wherein the most preformed compound for negative impression of blade profile is acrylonitrile butadiene styrene (ABS) polymer.
4. The method for fabrication of impeller with complex blade profiles as claimed in claim 1, wherein the blades or vanes are in curved shape and equi-spaced from each other.
5. The method for fabrication of impeller with complex blade profiles as claimed in claim 1, wherein the flexible mould is created by pouring of silicon rubber inside the 3D printed profile and got cured to have the desired profile.
6. The method for fabrication of impeller with complex blade profiles as claimed in claim 1, wherein the cement preform is fabricated by using flexible mould.

7. The method for fabrication of impeller with complex blade profiles as claimed in claim 1, the liquid metal is poured through a pouring port to get the desired shape impeller.