Machining method of deep and long precision step hole in intermediate casing

Abstract

The present invention discloses a method for processing deep and long precision step holes in an intermediate casing. Before the support plate is welded to the intermediate casing, a through hole is first processed on the insert, and then the insert is welded to the support plate. The support plate is then welded to the intermediate casing to complete the processing of each end face of the casing. Next, spiral milling is used to process the step hole with the smallest aperture, and then the remaining step holes are processed by spiral milling. The step holes with high positioning and precision requirements retain processing allowances, and finally a reamer is used to process the step holes with high positioning and precision requirements. The present invention solves the problem of iron chips wrapped around the tool, avoids tool breakage, and reduces processing costs. In addition, the present invention also improves the surface quality of the precision step holes and enhances processing efficiency.

Description

Technical Field

[0001] The invention relates to a method for machining a deep and long precision step hole in an intermediate casing of an aero-engine, and belongs to the technical field of mechanical machining. Background Art

[0002] Currently, the conventional processing methods for high-precision holes mainly include the following two methods:

[0003] The first type: rough drilling, semi-finishing countersinking, and finishing reaming / boring to achieve the required accuracy;

[0004] The second method is rough machining by milling, reaming / boring to achieve the required accuracy.

[0005] However, holes of different depths, sizes, and precisions are affected by many factors such as processing position, processing materials, and processing component structure, and the specific hole processing method still needs specific analysis.

[0006] The intermediate casing is the most important supporting and load-bearing component of the engine. It is precisely combined with the high-pressure compressor, low-pressure compressor, pivot bearing seat and other components to transmit thrust. Its quality directly affects the performance of the aircraft engine, and its quality, dimensional accuracy and other requirements are very strict.

[0007] The supporting casing and the intermediate casing usually have two on the boost support plate ( Figure 1 Deep, long, precision stepped holes (A8 and A9 in the figure) require machining. These precision stepped holes are difficult to machine, resulting in significant tool wear, low efficiency, and tedious processing, influenced by factors such as machining temperature, material, machining location, wall thickness, hole depth, and accuracy. The support plates are mostly titanium alloys, with some being high-temperature alloys. When the material hardness is low, machining chips can easily scratch the hole surface. When the material hardness is high, high tool quality and performance requirements are imposed, resulting in significant tool wear.

[0008] like Figure 1 and Figure 2 As shown, the precision step hole to be processed is located in the insert welded with the support plate ( Figure 2 In the middle S3), it is in a suspended state, with no support around it, thin and uneven wall, easy to vibrate the knife during processing, thus affecting the mechanical properties of the weld, and the processing accuracy is difficult to guarantee. Figure 1 As shown, the diameters of precision stepped holes, from smallest to largest, are D1, D2, and D3. The depth of the precision stepped holes is H, making them deeper. The D2 hole requires high precision and strict positioning. During machining, chips are not discharged smoothly, causing them to entangle the tool, increasing feed resistance and easily causing tool breakage, which is difficult to remove.

[0009] In addition, the inner cavity of the intermediate casing needs to be completely sealed before machining to avoid the influence of excess objects. In order to ensure that the chips can be discharged when milling holes, the sealing materials in the bottom hole of the support plate need to be manually taken out first, which is time-consuming and labor-intensive.

[0010] Considering that existing machining methods are prone to problems such as iron chips and cooling, which can lead to out-of-tolerance hole quality and diameter, often resulting in part scrapping, this not only causes severe direct economic losses but also affects production schedules and delays the delivery of complete machines, it is therefore crucial to improve the machining quality and efficiency of precision step holes while maintaining accuracy. Summary of the Invention

[0011] The present invention aims to provide a method for processing deep and long precision step holes in the intermediate casing, so as to solve the problems of iron chips wrapped around the tool and difficulty in chip removal, avoid tool breakage, and thus reduce processing costs. In addition, the temperature during the processing is reduced, thereby improving the surface quality of the precision step holes, and it can also reduce the pre-processing preparation work and improve processing efficiency.

[0012] In order to achieve the above object, the present invention adopts the following technical solutions:

[0013] A method for machining a deep and long precision step hole in an intermediate casing, wherein the precision step hole penetrates an insert on the upper end of a support plate, and the insert is suspended on the support plate, resulting in the precision step hole having no circumferential support. The precision step hole includes D1 hole, D2 hole and D3 hole with successively increasing apertures, wherein the D2 hole has positional requirements relative to the intermediate casing and has high machining accuracy. The machining method comprises the following steps:

[0014] Step 1: Before welding the insert to the support plate, treat the insert as a single piece and machine a through hole on the insert. The diameter of the through hole is based on the diameter of the D1 hole and a machining allowance is reserved. Then, weld the insert to the support plate.

[0015] Step 2: After welding the support plate to the intermediate casing and machining the end faces of the intermediate casing, select the center of the circle on the upper end face of the intermediate casing as the coordinate origin to establish a machining coordinate system. Use spiral milling to machine the through holes on the insert to form D1, D2, and D3 holes. Leave a machining allowance for D2 hole, and machine D1 and D3 holes to the final diameter.

[0016] Step 3: Measure the hole diameters of D1 and D3. If they meet the requirements, proceed to step 4. If not, repeat the spiral milling in step 2 until the hole diameters meet the requirements.

[0017] Step 4: Use a reamer to process the D2 hole until it meets the final hole diameter requirements.

[0018] As an option, in step 1, a through hole is machined on the insert by drilling first and then reaming.

[0019] As an option, in step 2, down milling is used when spiral milling the D1 hole, the D2 hole, and the D3 hole.

[0020] As an option, in step 2,

[0021] The diameter of the milling cutter used in spiral milling of the D1 hole is smaller than the corresponding final hole diameter of the D1 hole, and the blade length of the milling cutter is greater than the hole depth of the D1 hole;

[0022] The diameter of the milling cutter used in spiral milling of the D2 hole is smaller than the corresponding final hole diameter of the D2 hole, and the blade length of the milling cutter is greater than the hole depth of the D2 hole;

[0023] The diameter of the milling cutter used in spiral milling of the D3 hole is smaller than the corresponding final hole diameter of the D3 hole, and the blade length of the milling cutter is greater than the hole depth of the D3 hole.

[0024] further,

[0025] The diameter of the milling cutter used in the spiral milling of the D1 hole is 2 to 4 mm smaller than the final diameter of the corresponding D1 hole;

[0026] The diameter of the milling cutter used in the spiral milling of the D2 hole is 2 to 4 mm smaller than the final diameter of the corresponding D2 hole;

[0027] The diameter of the milling cutter used in the spiral milling of the D3 hole is 2 to 4 mm smaller than the final diameter of the corresponding D3 hole.

[0028] As an option, in step 2, the milling cutter performs spiral milling downward along the Z axis while moving in a circular motion in the X / Y directions.

[0029] As an option, in step 2, the D1 hole is first spirally milled to the final hole diameter, and then the D2 hole or the D3 hole is spirally milled after the tool is changed.

[0030] As an option, in step three, after completing step two, the intermediate casing is kept clamped on the machine tool, and the apertures of the D1 hole, the D2 hole, and the D3 hole are measured online.

[0031] As an option, in step 4, the blade diameter of the reamer is equal to the final hole diameter of the D2 hole, the shank diameter of the reamer is equal to the final hole diameter of the D2 hole, and the blade length of the reamer is greater than the hole depth of the D2 hole.

[0032] As an option, the milling cutter is available with internal coolant.

[0033] Prior art typically involves a combination of drilling, milling, boring, and reaming to produce deep, long, and precise stepped holes. This process involves selecting multiple milling cutters, along with tool alignment, tool changes, and program compilation, which consumes significant time and effort, resulting in low efficiency. Furthermore, during machining, iron filings can entangle the cutter, leading to poor hole quality, scratches, and increased hole diameter, making quality control difficult. If a cutter breaks during machining, it can be extremely difficult to remove without compromising the quality of other parts.

[0034] The present invention has significant advantages over the prior art. It solves the problems of low machining efficiency, easy tool breakage, poor chip removal, and long machining preparation time in the deep and long precision step holes on the support plate of the intermediate casing. The advantages are as follows:

[0035] (1) The processing quality of deep and long precision step holes is improved. Deep and long precision step holes are processed by spiral milling, which improves the surface quality of the hole and avoids the problem of strip iron chips scratching the hole surface and the problem of iron chips wrapping around the knife causing the knife to break (spiral milling turns strip iron chips into powder or granular chips).

[0036] (2) Sufficient cooling during the processing process avoids the situation where the hole diameter is unqualified due to stress release.

[0037] (3) High economic benefits and low processing costs. The present invention reduces tool consumption, reduces the number of milling cutters, and eliminates the need for boring cutters and large-diameter milling cutters.

[0038] (4) Improved processing efficiency. The present invention reduces the downtime of tool alignment, clamping, and tool changing between the two tools (milling cutter and reamer). The bottom hole of the support plate where the precision step hole is located does not need to remove the blockage, further saving processing time. BRIEF DESCRIPTION OF THE DRAWINGS

[0039] Figure 1 This is a schematic diagram of the deep and long precision step hole in the intermediate receiver;

[0040] Figure 2 yes Figure 1 Schematic diagram of the C3-C3 cross section;

[0041] Figure 3 This is a schematic diagram of the machining process for deep and long precision step holes;

[0042] Figure 4 It is a schematic diagram of spiral milling. DETAILED DESCRIPTION

[0043] The present invention is further described below with reference to the accompanying drawings and specific embodiments. However, it should not be understood that the scope of the subject matter described in the present invention is limited to the following embodiments. Without departing from the above technical ideas of the present invention, various modifications, substitutions and changes made according to common technical knowledge and customary means in the field are included in the scope of the present invention.

[0044] To solve Figure 1 and Figure 2 The present invention solves the problem of processing deep and long precision step holes shown in the figure by adjusting the processing sequence, feed mode, speed, tool, etc. When processing deep and long precision step holes, the processing method is first determined based on the hole diameter, depth, processing position and accuracy requirements. Then, combined with the size requirements of the hole to be processed, the processing tool is selected according to the determined processing method and the part clamping is completed. Next, the processing origin of the part is determined and the processing program is compiled. After the program is proofread and correct, processing begins. During this process, a stop check is performed to reduce or prevent errors. After the program is completed, the hole size is measured to see if it is qualified.

[0045] The solution of the present invention includes the following aspects:

[0046] (1) Selection of processing route. According to the structural shape of the intermediate casing, the position of the processing hole, the clamping state, the hole size accuracy, etc., in order to ensure the final position and accuracy requirements of the precision step hole, improve the processing efficiency and quality, and leave an allowance for welding deformation, when it is a single piece (that is, the insert has not been welded to the support plate, and the support plate has not been welded to the intermediate casing, the insert is regarded as a single piece), first use the aperture of the smallest hole D1 as the basis and leave a processing allowance of 4 to 6 mm (that is, the single-side allowance of the hole is 2 to 3 mm) to drill and ream a through hole on the insert. Then weld the insert to the support plate. After the support plate welding is completed and the processing of each end face of the intermediate casing is completed (such as Figure 2 , at this time the support plate has been welded to the intermediate casing), spiral milling is used to process the D1 hole, D2 hole and D3 hole, among which the D2 hole is precision-reamed with a 0.1mm margin (different margins can be reserved according to the dimensional accuracy requirements), and the D1 hole and D3 hole are directly spiral milled to the final size.

[0047] (2) Selection of the coordinate origin. Based on the structure of the intermediate casing, the clamping method, and the position of the precision step hole to be processed, the center of the circle on the upper end face of the intermediate casing is selected as the coordinate origin (the coordinate origin is very critical and varies depending on the parts, structures, and clamping, so the structure of different parts is different. In the present invention, the center of the circle on the upper end face of the intermediate casing is selected as the coordinate origin based on the characteristics of the intermediate casing structure, clamping method, and the position of the hole to be processed).

[0048] (3) Selection of tools: Considering that the shape of the processing object is a stepped hole, there is a certain distance from the coordinate origin to the end face of the precision stepped hole to be processed, and the processing method is to select a milling cutter and a reamer. Therefore, the diameter of the milling cutter is usually selected to be 2 to 4 mm smaller than the final hole diameter of the D1 hole, the length of the milling cutter blade is greater than the depth of the D1 hole in the precision stepped hole, and the cooling method of the milling cutter is internal cooling (the coolant is sprayed from the center of the tool during the processing process). The diameter of the milling cutter is similar when spiral milling the D2 and D3 holes, and the blade length is also greater than the hole depth of the D2 and D3 holes. The cooling method of the spiral milling cutter is still internal cooling; the diameter of the reamer is the same as the final hole diameter of the reamed hole D2, the blade length of the reamer is greater than the hole depth of the D2 hole, and the shank diameter of the reamer is the same as the final hole diameter of the D2 hole.

[0049] (4) Selection of processing parameters. The processing parameters are selected based on the processing material, cutting tool, etc., and are determined based on the specific situation. For example, in the present invention, the speed of spiral milling for precision step holes is 700 r / min, the spiral feed rate is 0.5, the safety distance is 2 mm, and the processing method is spiral down milling; when reaming, the speed is 200 r / min, the cutting feed rate is 80 mm / min, the safety distance is 2 mm, and the tool retraction is 3000 mm / min.

[0050] (5) The process of spiral milling a hole. The hole depth is machined first, then the hole radius (hole center difference), and the milling cutter mills obliquely into the pre-machined through hole of the part (i.e., milling spirally downward along the Z axis while moving in a circular motion in the X / Y direction).

[0051] (6) Reaming process. After spiral milling completes the three precision step holes D1, D2, and D3 and the dimensions are measured to meet the requirements, the reamer is changed and G01 is executed. The reamer is quickly positioned to a safe position directly above the hole center at a feed rate of 1000 mm / min. The reaming is completed at a feed rate of 80 mm / min. The reamer is then quickly raised to a safe position and retracted.

[0052] according to Figure 3 The process diagram in the middle is to formulate a processing method according to the precision step hole to be processed, then select the processing tool of the hole, determine the processing coordinate origin, and complete the part clamping. The specific steps of the processing method of the present invention are as follows:

[0053] Step 1, program compilation. Take Siemens system five-axis machining center as an example, given the spindle speed S1 of milling processing = 700r / min, each time press Figure 3The spiral milling program is MCALL POCET4 (RTP, RFP, SDIS, hole depth H, PRAD, PA, PO, MID, FAL, FALD, FFP1, FFD, 0, 1002,,,,,). Note that the ",,,,," are built-in instructions for the Siemens system and are provided for the convenience of user addition and editing. In the reaming program, the spindle speed is given, and the feed rate for positioning the reamer to the hole center, reaming, lifting the tool, and returning to the safe plane is given. The reamer uses G01 to complete the reaming. When reaming, the feed rate is very low, and positioning is rapid.

[0054] Step 2: Spiral milling to process the hole. Figure 4 At the beginning of the program, the milling cutter quickly positions (G0) to the safe position just above the machining center of the hole (a through hole drilled in a single piece, i.e., the basic hole), and completes the spiral milling hole processing parameters MCALL POCET4 (RTP, RFP, SDIS, hole depth H, PRAD, PA, PO, MID, FAL, FALD, FFP1, FFD, 0, 1002,,,,,) to mill the D1 hole, D2 hole, and D3 hole; the hole depths of the three holes are set according to the depth of each hole, 0 represents forward milling, 1 represents reverse milling, and forward milling is used in the finishing. First, mill the D1 hole to the final aperture. There is no requirement for the order of spiral milling of the D2 hole and the D3 hole. You can mill the D2 hole first and then the D3 hole, or you can mill the D3 hole first and then the D2 hole.

[0055] Step 3: Measure the hole diameter online. After spiral milling is complete, measure the diameters of holes D1, D2, and D3 online to see if they meet the requirements. If they differ from the program segment, adjust tool wear compensation. Another purpose of measuring the diameter of hole D3 is to prepare the program for reaming hole D2.

[0056] Step 4: Ream. Once the spiral milling process is complete and the hole diameter meets the requirements, replace the reamer with one with a diameter equal to the diameter of hole D2 and ream hole D2. Linear interpolation is used with G01 tool movement, rapidly positioning the tool to the center of hole D2 at a speed of 1000 mm / min. Ream the hole at a speed of 50 mm / min with internal coolant, then move the tool to the center of hole D2 at a speed of 2000 mm / min. Finally, use G01 tool movement at a speed of 3000 mm / min to quickly return to the safe plane.

[0057] Field processing has proven that this invention offers high economic benefits, reducing tool consumption from 10 small-diameter milling cutters per hole to 2 per hole, significantly reducing tool consumption. Furthermore, this invention eliminates the need for boring cutters and large-diameter milling cutters, reducing tool costs. This invention also offers high machining efficiency, reducing the time required for tool alignment and clamping, as well as downtime associated with tool changes. Furthermore, the bottom hole of the support plate, where the precision step hole is located, does not require the removal of obstructions, further saving cleaning time.

[0058] Any content not described in detail in this specification belongs to the prior art known to those skilled in the art. Although the present invention is described in the above specific embodiments, it should be understood that the present invention is not limited to the scope of the specific embodiments. For those skilled in the art, as long as various variations fall within the scope of the claims, they are protected by the present invention.

Claims

1. A method for machining a deep, long, precision stepped hole in an intermediate casing. The precision stepped hole penetrates an insert at the upper end of a support plate, and the insert is suspended on the support plate, resulting in the precision stepped hole having no circumferential support. The precision stepped holes include D1, D2, and D3 holes of successively increasing diameters. The D2 hole has positional requirements relative to the intermediate casing. The method is characterized by: The processing method comprises the following steps, Step 1: Before welding the insert to the support plate, treat the insert as a single piece and machine a through hole on the insert. The diameter of the through hole is based on the diameter of the D1 hole and a machining allowance is reserved. Then, weld the insert to the support plate. Step 2: After welding the support plate to the intermediate casing and machining each end face of the intermediate casing, select the center of the circle on the upper end face of the intermediate casing as the coordinate origin to establish a machining coordinate system. Use spiral milling to machine the through holes on the insert to form D1, D2, and D3 holes. Leave a machining allowance for D2 hole, and machine D1 and D3 holes to the final aperture. The milling cutter used for spiral milling is an internally cooled tool. The milling cutter mills downward along the Z axis while moving in a circular motion in the X / Y directions. Step 3: Measure the hole diameters of D1 and D3. If they meet the requirements, proceed to step 4. If not, repeat the spiral milling in step 2 until the hole diameters meet the requirements. Step 4: Use a reamer to process the D2 hole until it meets the final hole diameter requirements.

2. The method for machining a deep and long precision stepped hole in an intermediate casing according to claim 1, characterized in that: In the step 1, a through hole is machined on the insert by drilling first and then reaming.

3. The method for machining a deep and long precision stepped hole in an intermediate casing according to claim 1, characterized in that: In the step 2, the spiral milling of the D1 hole, the D2 hole and the D3 hole is performed in a down-milling manner.

4. The method for machining a deep and long precision stepped hole in an intermediate casing according to claim 1, characterized in that: In the step 2, The diameter of the milling cutter used in spiral milling of the D1 hole is smaller than the corresponding final hole diameter of the D1 hole, and the blade length of the milling cutter is greater than the hole depth of the D1 hole; The diameter of the milling cutter used in spiral milling of the D2 hole is smaller than the corresponding final hole diameter of the D2 hole, and the blade length of the milling cutter is greater than the hole depth of the D2 hole; The diameter of the milling cutter used in spiral milling of the D3 hole is smaller than the corresponding final hole diameter of the D3 hole, and the blade length of the milling cutter is greater than the hole depth of the D3 hole.

5. The method for machining a deep and long precision stepped hole in an intermediate casing according to claim 4, characterized in that: The diameter of the milling cutter used in the spiral milling of the D1 hole is 2 to 4 mm smaller than the final diameter of the corresponding D1 hole; The diameter of the milling cutter used in the spiral milling of the D2 hole is 2 to 4 mm smaller than the final diameter of the corresponding D2 hole; The diameter of the milling cutter used in the spiral milling of the D3 hole is 2 to 4 mm smaller than the final diameter of the corresponding D3 hole.

6. The method for machining a deep and long precision stepped hole in an intermediate casing according to claim 1, characterized in that: In the step 2, the D1 hole is firstly spiral milled to the final hole diameter, and then the D2 hole or the D3 hole is spiral milled after the tool is changed.

7. The method for machining a deep and long precision stepped hole in an intermediate casing according to claim 1, characterized in that: In the step three, after completing step two, the intermediate casing is kept in a clamped state on the machine tool, and the apertures of the D1 hole, the D2 hole, and the D3 hole are measured online.

8. The method for machining a deep and long precision stepped hole in an intermediate casing according to claim 1, characterized in that: In the step 4, the blade diameter of the reamer is equal to the final hole diameter of the D2 hole, the shank diameter of the reamer is equal to the final hole diameter of the D2 hole, and the blade length of the reamer is greater than the hole depth of the D2 hole.

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