FIELD OF THE INVENTION

[0001] The present invention relates to the field of manufacturing of aerospace components. Particularly, the present invention relates to the field of additive manufacturing of aerospace components. More particularly, the present invention relates to integral fuel supply micro tubes used in a jet engine and its method of manufacturing .

BACKGROUND OF THE INVENTION

[0002] A micro tube plays an important role in an aero engine fuel system. These tubes supply fuel into a combustion chamber as per demand of the engine thrust management and control unit, where it is burned and releases heat energy. These tubes also supply lubricants into bearings. Traditionally, these tubes are made by a process of extrusion followed by the processes of sinking, drawing, and ironing. [0003] These traditionally manufactured parts have the following drawbacks:

- The traditional method requires that the parts be made separately and then joined using precise joining processes.

- The manufacturing processes demand mass quantity for economic production of these parts.

- Enormous initial investments are required for these processes. - It requires precise post processing before it fits into the engine fuel system.

[0004] To overcome the above drawbacks, an additive manufacturing method has been proposed in the present invention.

OBJECTS OF THE INVENTION

[0005] Some of the objects of the present disclosure, which at least one embodiment herein satisfies, are as follows:

[0006] It is an object of the present invention to provide an integral (single piece) fuel supply micro tube. [0007] It is another object of the present invention to provide an additive manufacturing method for the integral fuel supply micro tube which result in elimination of drawbacks of existing manufacturing methods. [0008] It is yet another object of the present invention to provide an additive manufacturing process which can produce desired shaped integral fuel supply micro tube with precision and less material waste.

[0009] It is still another object of the present invention to design integral fuel supply micro tube in a single building block and in a single printing cycle, thereby eliminating excessive inventory which results in cost saving. [00010] It is a further object of the present invention to provide an optimised support for holding the integral fuel supply micro tube being printed and dissipating heat to surrounding. [00011] Other objects and advantages of the present disclosure will be more apparent from the following description which is not intended to limit the scope of the present disclosure.

BRIEF DESCRIPTION OF THE ACCOMPANYING DRAWINGS:

[00012] The invention will now be described in relation to the accompanying drawings, in which:

[00013] Figure 1 illustrates the flow chart of the conventional process of micro tube manufacturing;

[00014] Figure 2 illustrates an integral fuel supply micro tube printed by an additive manufacturing method of the present invention; and

[00015] Figure 3 illustrates the flow chart of an invented process for integral fuel supply micro tube manufacturing.

SUMMARY OF THE INVENTION

[00016] According to this invention, an additive manufacturing process is used for manufacturing an integral fuel supply micro tube. The additive manufacturing is a novel manufacturing method in which micro tubes are produced in integral form. In this manufacturing method micro tubes are made by using digital model and layer by layer material build-up approach. This tool-less manufacturing method can produce uniform integral (one piece) micro tubes in a short time with high precision. In one embodiment, the additive manufacturing process for manufacturing an integral fuel supply micro tube comprising a micro tube and a hollow screw; said method comprises the following steps:

- providing metal powder as a raw material wherein the metal powder is selected from a group consisting of Nickel based alloy, Titanium alloys and Steel;

- providing a 3D printing device;

- spreading said metal powder layer by layer on a predetermined platform;

- selectively fusing said metal powder using at least one energy source at predetermined conditions to perform a printing operation to obtain a micro tube with a build platform;

- heat treating said integral fuel supply micro tube with a build platform in a furnace at a predetermined temperature followed by cooling to room temperature to obtain heat treated integral fuel supply micro tube with a build platform;

- subjecting said heat treated integral fuel supply micro tube with a build platform to wire cutting operation to separate the integral fuel supply micro tube from the build platform, followed by shot blasting to generate compressive residual stresses on the surfaces of the integral fuel supply micro tube, and buffing operation to obtain the integral fuel supply micro tube with pre-determined surface finish; and - finishing the threads on the hollow screw.

[00017] In one preferred embodiment, the process comprises a pre-step of printing a support having predetermined configuration meant for holding said integral fuel supply micro tube and transferring heat from the part/s being 3D printed to the platform during printing operation, wherein said printing operation comprises spreading metal powder layer by layer on a predetermined platform followed by fusing said powder using at least one energy source at predetermined conditions. Increased productivity and reduced cost of production is achieved by the reducing the number of steps in manufacturing process. The additive manufacturing approach eliminates the processes of extrusion, sinking, drawing, ironing and precision joining for a micro tube manufacturing, as shown in fig. 1.

[00018] In another aspect of the present invention, there is provided an integral fuel supply micro tube (100) for a jet engine; said (100) integral fuel supply micro tube comprises 3D printed micro tube (10) and a 3D printed hollow screw (20). According to one embodiment of the present invention, a micro tube (10) and a hollow screw (20) are manufactured in a single print by additive manufacturing. [00019] The present invention describes a reduction in tooling for tube bending and welding of thin wall micro tubes to make an integral part. [00020] It also eliminates the problem of maintaining the exact shape of the curve due to spring back effect.

DETAILED DESCRIPTION

[00021] 3D printing, also known as additive manufacturing, refers to a process used to create a three-dimensional object in which layers of material are formed under computer control to create an object. Parts that are to be manufactured are made so by this process directly from digital model by using layer by layer material build-up approach. This tool-less manufacturing method can produce fully dense metallic parts in a short time period with high precision.

[00022] According to this invention, there is provided an integral (one piece) fuel supply micro tube and manufacturing method for the same.

[00023] Specifically, the present invention relates to the manufacturing of an integral fuel supply micro tube for jet engines using a selective laser sintering process. The inventive feature of this invention is the design and development of the integral fuel supply micro tube and the manufacturing process to make the same. In an illustrative embodiment, the method for manufacturing an integral fuel supply micro tube is illustrated in figure 3 of the accompanying drawings. The obtained integral fuel supply micro tube printed by additive manufacturing method of the present invention is illustrated in Figure 2 of the accompanying drawing. The integral fuel supply micro tube (100) for a jet engine, comprises a 3D printed micro tube (10) and a 3D printed hollow screw (20). According to one embodiment of the present invention, a micro tube (10) and a hollow screw (20) are manufactured in a single print by an additive manufacturing method. The present invention describes a reduction in tooling for tube bending and welding of thin wall micro tubes to make an integral part. It also eliminates the problem of maintaining the exact shape of the curve due which gets disturbed to spring back effect. Increased productivity and reduced cost of production is achieved by reducing the number of steps in manufacturing processes. The additive manufacturing approach eliminates the processes of extrusion, sinking, drawing, ironing and precision joining for a micro tube manufacturing, as shown in fig. 1.

[00024] In at least an embodiment of this invention, the integral fuel supply micro tube comprising these above-mentioned features is designed and rendered using a rendering software which is then used as an input for the additive manufacturing process.

[00025] In accordance with one embodiment, the additive manufacturing of integral fuel supply micro tube comprising a micro tube and a hollow screw, involves the following steps:

[00026] In the first step, metal powder as a raw material and a 3D printing device is provided or kept ready. In the second step, the metal powder is spread layer by layer on a predetermined platform of 3D printing device. Typically, the temperature of said platform is set in the range of 80 to 160 °C. In one preferred embodiment, the temperature is set at 80 °C.

[00027] Typically, the layer has a thickness in the range of 0.02 to 0.08 mm and a laser strip width in the range of 5 to 10 mm. Typically, the overlap between the layers is in the range of 0.10 to 0.15 mm. In one preferred embodiment, the layer has a thickness of 0.02 mm, a laser strip width 5 mm and the overlap between the layers is 0.12 mm.

[00028] In one embodiment, the spreading comprises controlled deposition of the layers of metal powder to form integral fuel supply micro tube. In one embodiment, the spreading comprises depositing layers of a metal powder sequentially one upon the other to form features.

[00029] After spreading, the powder is selectively fused using at least one energy source at predetermined conditions to perform a printing operation to obtain an integral fuel supply micro tube with a build platform. Typically, the energy source is selected from the group consisting of laser beam and electron beam. The energy source has a scanning speed of about 800 to 1400 mm/second and has power of 80 to 400 watt. In one preferred embodiment, the energy source has a scanning speed of about 1000 mm/second and, has power of 195 watt.

[00030] In the third step, the integral fuel supply micro tube with a build platform is heated in a furnace at a predetermined temperature followed by cooling to room temperature to obtain heat treated integral fuel supply micro tube.

[00031] In one preferred embodiment, the heat treatment step involves the following steps:

Step A: annealing the integral fuel supply micro tube with a build platform at a temperature ranging from 900 to 1200 °C for a period ranging from 30 minutes to 120 minutes in an inert Argon atmosphere followed by cooling to room temperature to obtain annealed integral fuel supply micro tube with a build platform.

Step B: ageing the integral fuel supply micro tube with a build platform by holding the part at a temperature ranging from 700 to 800° C for a time period ranging from 5 to 10 hours in an inert Argon atmosphere followed by cooling to a temperature ranging from 625 to 675°C in 1 to 3 hours and holding at a temperature ranging from 625 to 675 °C for 6 to 10 hours to obtain aged integral fuel supply micro tube with a build platform.. Step C: air cooling said parts with a build platform to room temperature to obtain heat treated integral fuel supply micro tube with a build platform.

[00032] In fourth step, the heat treated integral fuel supply micro tube with a build platform is subjected to wire cutting operation to separate the integral fuel supply micro tube from the build platform to obtain separated integral fuel supply micro tube.

[00033] In the fifth step, the integral fuel supply micro tube is subjected to shot blasting to generate compressive residual stresses on the surfaces of the integral fuel supply micro tube to obtain shot blasted integral fuel supply micro tube.

[00034] In the sixth step, a buffing operation is performed to obtain the integral fuel supply micro tube with pre-determined surface finish to obtain buffed integral fuel supply micro tube.

[00035] In the final step, the threads on the hollow screw threads are finished by using threading dies to obtain integral fuel supply micro tube and then, integral fuel supply micro tube is tested for leakage at 15 bar pressure.

[00036] In accordance with a preferred embodiment of the present invention the process comprises a pre-step of printing a support having predetermined configuration meant for holding said integral fuel supply micro tube and transferring heat from the part/s being 3D printed to the platform during printing operation, wherein said printing operation comprises spreading metal powder layer by layer on a predetermined platform followed by fusing said powder using at least one energy source at predetermined conditions. [00037] The 3D printing or additive manufacturing process consists of making a part layer by layer. The required amount of a layer of powder is fused using an energy source. Each new layer of fused powder requires support from layer beneath it (formed previously). An integral fuel supply micro tube has overhang or bridge thus needs use of 3D printed support structures to ensure a successful print. The support structures are found to have both positive as well as negative effects on the 3D printing process. On the one hand the support structures help in transfer of heat, prevent extreme powder inclusion, support the overhanging part of the product and secures the part against detachment during the building process. On the other hand the support structure leads to waste of material, may affect the surface finish of the product and leads to requirement of post processing operations to remove it. Hence, it is found that the selection of type and geometry of support structure is critical for defect less manufacturing, ease of manufacturing and economic manufacturing.

[00038] According to the present invention several types of supports which can be used during the 3D printing are tried. The type of support to be used is decided based on the quantity of material required for supports, heat dissipation of product to surrounding, geometry of model etc. Different types of supports which are tried include Block type, Line type, Point type, Web Type, Contour type, Gusset type, Hybrid type and Volume type etc. The support structure with different features like hatching, hatching teeth, fragmentation, borders, border teeth, perforations, gusset borders etc. are experimented.

[00039] Based on the considerations and experimentations, during the manufacturing of the integral fuel supply micro tube, the preferred type of support used is combination of block support with hatching teeth and perforation type support, volume support and hybrid support. According to the invented process, the manufacturing process starts with a metal powder as a raw material. The metal material includes but is not limited to Nickel based alloy, Steel, Titanium based alloys and the like. In one of the embodiments, the metal powder used is IN718. This metal powder is spread on a bed (which is its build platform), layer by layer, and selectively fused by using an energy source like a laser or an electron beam. After completion of the print, the part is transferred to a furnace, where heat treatment is conducted, according to pre-determined parameters, and required properties are achieved. Then, final heat-processed parts are separated from the build platform by using a wire cutting operation. Finally, a buffing operation is conducted on the micro tubes (i.e. the heat processed parts after its removal from the build platform) and it is then tested for leakage.

[00040] The integral fuel supply micro tube manufacturing process is described, in detail, as below.

[00041] Figure 3 illustrates the manufacturing process in accordance with one exemplary embodiment of the present invention. The process typically, involves the following steps: [00042] CAD Model generation:

Producing a digital model of the part (i. e. the microtube) is the first step in the additive manufacturing process. A digital model is produced by using computer aided design, refer fig. 2. Then, this CAD model is converted into a Stereo lithography / Surface Tesselation Language / Standard Triangulation Language file (STL) which is used by further portions and processes of this invention.

[00043] Additive Manufacturing program generation:

Once an STL file has been generated, the file is imported into a MAGICS MATERIALISE software. MAGICS is used for defining part orientation and generating support. Then, STL file is sent to the slicer software for slicing. After slicing, the file is imported in EOSPRINT software. EOSPRINT software is used for assigning the build parameters and these further are optimized for CAD data. Then after-parameters like laser power, scanning speed, hatch distance and layer thickness are designed. Finally, the file is exported to the 3D printing machine for producing the part. [00044] Additive Manufacturing or 3D printing:

Different types of materials can be used for manufacturing integral fuel supply micro tube which include but are not limited to Nickel based alloys (IN718, IN713C, IN625, etc.), Steel, titanium alloy and the like. In one embodiment, the material used is IN718. Then powder is spread on the build platform layer by layer with a layer thickness of 0.020 mm. During this activity platform temperature is maintained in range of 80 to 160 °C throughout the process. In one embodiment, a platform temperature of 80 °C is used. After spreading each layer, powder is selectively fused by using a laser with a scanning speed of 1000 mm/Sec for parts and 400 mm/Sec for support in an Argon environment. The output of this process is an integral fuel supply micro tube with a build platform. The summary of parameters used to produce the integral fuel supply micro tubes in additive manufacturing are mentioned in table 1.

Table 1

[00045] Heat treatment:

Heat treatment is carried out on the integral fuel supply micro tube with build platform to achieve the mechanical properties and de-stress the integral fuel supply micro tubes. Firstly, integral fuel supply micro tubes with build platform are solution annealed. The integral fuel supply micro tubes with build platform are solution treated at 1065 °C for one hour in an inert Argon atmosphere, followed by air cooling to room temperature. The second heat treatment is ageing. In this treatment, integral fuel supply micro tubes with build platform are held at 760 °C for ten hours in an inert Argon atmosphere, after that it is furnace cooled to 650 °C in two hours and then held at 650 °C for eight hours in an inert Argon atmosphere. Finally, the integral fuel supply micro tube with build platform is air cooled to the room temperature. The above heat treatment is performed for IN718. The various materials can be utilized to manufacture the integral fuel supply micro tubes which include but are not limited to Steel, Nickel based alloys, titanium based alloys and the like. The mechanical properties achieved after heat treatment are summarised in table 2. (Material used is IN718). The below provided properties and values are illustrative and not considered as limitation to scope of the present invention. Table 2

[00046] Wire cutting and support removal:

The heat treated integral fuel supply micro tube is separated from the build platform by using wire cutting operation. Next, the supports formed during the 3D printing operation are machined off.

[00047] Polishing and thread finishing:

After that, buffing operation is performed to obtain the desired finish on integral fuel supply micro tubes. Then, the threads are finished by using threading dies.

[00048] Leak test:

Finally, integral fuel supply micro tubes are tested for leakage at 15 bar pressure. [00049] In accordance with another aspect of the present invention there is also provided integral fuel supply micro tubes made by the 3D printing method of the present invention. Said micro tubes characterized by predetermined structural configuration and characteristics.

[00050] In accordance with still another aspect of the present invention there is also provided a system for manufacturing integral fuel supply micro tubes by 3D printing method, said system comprises 3D printing device and support. It is critical to design an optimized support which can be suitable for printing integral fuel supply micro tubes, as other type of support makes marks on surface of parts. In one embodiment, the support comprises teeth/grooves. The teeth/grooves enable easy removal of supports. Support height is optimised for better heat transfer (heat dissipation) between build platform and job at the time of part building. It also avoids distortion in the part. The amount of support required to build the part is based on the orientation of part. The optimized orientation is selected based on least amount of material required for support generation, minimum laser travel time for generating the support, support free critical areas of the component and height of support that dissipates better heat transfer to build platform from job. Based on above factors for optimized orientation of integral micro tube, the height of supports is selected from the range of 2.16 mm to 2 mm. [00051] While this detailed description has disclosed certain specific embodiments for illustrative purposes, various modifications will be apparent to those skilled in the art which do not constitute departures from the spirit and scope of the invention as defined in the following claims, and it is to be distinctly understood that the foregoing descriptive matter is to be interpreted merely as illustrative of the invention and not as a limitation.