Surface machining method for hard inner hole of wear-resistant bushing of supporting type casing

Abstract

The invention discloses a method for machining the surface of a hard inner hole of a wear-resistant bushing of a bearing type casing. The method comprises the following steps of: 1, controlling the allowance and cylindricity before the wear-resistant bushing is assembled; step 2, assembling the wear-resistant bushing; step 3, grinding, polishing, clamping and aligning the support type casing, firstly roughly aligning a reference circle for the hard inner hole of the wear-resistant bushing, and then finely aligning the reference circle for the hard inner hole of the wear-resistant bushing; fourthly, rough grinding, fine grinding and accurate grinding are sequentially adopted for grinding machining, the grinding mode is spiral grinding and polishing, and the shape tolerance of the hard inner hole of the wear-resisting bush of the bearing type casing is guaranteed; and fifthly, rough polishing, fine polishing and fine polishing are sequentially adopted for polishing machining, the polishing mode is spiral polishing, and the surface covering roughness of the hard inner hole of the wear-resisting bush of the bearing type case is guaranteed. According to the method, the problem that the surface shape tolerance and the surface roughness of the hard inner hole of the wear-resistant bushing of the bearing type casing are difficult to guarantee is solved, the machining efficiency is improved, and the machining cost is reduced.

Description

Technical Field

[0001] This invention belongs to the field of aero-engine manufacturing technology, specifically relating to a method for machining the hard inner hole surface of a wear-resistant bushing for a support-type casing. Background Technology

[0002] like Figure 1 As shown, the support casing of aero-engines has high-precision wear-resistant bushings for mounting engine pivots. These bushings undergo special treatments such as nitriding, phosphating, chrome plating, and copper plating, with a hardness of around 40 HRC. However, the surface roughness of the inner hole of the wear-resistant bushing in the support casing is required to be within Ra0.1, the cylindricity within 0.008mm, and the total runout within 0.03mm, which makes the machining process difficult.

[0003] Given the complex structure and large size of support casings, current machining methods involve using a CNC lathe to remove large allowances while ensuring shape tolerances, followed by clamping on a conventional horizontal lathe and manual polishing with sandpaper to ensure surface roughness. Due to the high hardness of the bushings, carbide cutting tools are used, resulting in significant tool wear, high machining costs, and difficulty in guaranteeing the shape tolerances of the wear-resistant bushing's inner bore. Manual polishing with sandpaper takes 12 hours, is inefficient, cannot guarantee surface roughness, and poses a safety risk to operators when manually polishing large casings.

[0004] Therefore, it is necessary to design a method for machining the hard inner hole surface of the wear-resistant bushing of the support type casing, so that the cylindricity can be controlled at about 0.006mm, the total runout at about 0.02mm, the roughness at about Ra0.06, and the tool wear is low, and the grinding and polishing time is reduced to half an hour. Summary of the Invention

[0005] The present invention aims to provide a method for machining the hard inner hole surface of the wear-resistant bushing of the support casing, which solves the problem of difficulty in ensuring the surface shape tolerance and surface roughness of the hard inner hole of the wear-resistant bushing of the support casing, improves machining efficiency and reduces machining cost.

[0006] To achieve the above objectives, the present invention adopts the following technical solution: A method for machining the hardened inner hole surface of a wear-resistant bushing for a support-type casing, comprising: Step 1: Controlling the allowance and cylindricity before assembling the wear-resistant bushing. Before installing the hard inner hole of the wear-resistant bushing into the support type casing, allowance should be left on one side, and the cylindricity should be controlled within 0.01mm to provide allowance for grinding adjustment. Step 2, assembly of wear-resistant bushings. During the assembly of wear-resistant bushings into the support housing, they should be subjected to uniform force. All areas of the wear-resistant bushing should enter the support housing hole axially at the same time. They should not be rotated or twisted during installation. Step 3: Grind, polish, clamp and align the support casing. First, roughly align the reference circle of the hard inner hole of the wear-resistant bushing, and then finely align the reference circle to eliminate the influence of the flatness and cylindricity of the wear-resistant bushing itself. Step four: Grinding is carried out in sequence using coarse grinding, fine grinding, and precision grinding. The grinding method is spiral grinding and polishing to ensure the shape tolerance of the hard inner hole of the wear-resistant bushing of the support casing. Step 5: Polishing is carried out sequentially using coarse polishing, fine polishing, and precision polishing. The polishing method is spiral polishing to ensure the surface roughness of the hard inner hole of the wear-resistant bushing of the support casing.

[0007] As one possible approach, in step three: The rough alignment reference circle is within 0.05mm of the inner hole of the wear-resistant bushing, and the runout of the end face of the wear-resistant bushing is within 0.04mm. The precise alignment reference circle is within 0.008mm of the inner hole of the wear-resistant bushing, and the runout of the end face of the wear-resistant bushing is within 0.008mm.

[0008] Furthermore, in step three: When precisely aligning the reference circle, use T-blocks, screws, shoulder nuts, pads, or pressure plates to fix and tighten the support housing. During the tightening process, press a dial indicator against the surface of the wear-resistant bushing and observe whether the dial indicator reading changes. If the dial indicator reading changes, it indicates that the support housing at the tightened part has shifted or is deformed. It must be realigned and tightened until the change in the dial indicator reading at the alignment point is within 0.008mm after tightening.

[0009] As one solution: In step one, the hard inner hole of the wear-resistant bushing is left with a 0.1mm margin on one side before it is installed into the support-type casing; In step four: The grinding depth for rough grinding is 0.05 mm, the machine tool spindle speed is 300 r / min, the grinding head speed is 1800 r / min, and the axial feed is 30 mm / min. The grinding depth of fine grinding is 0.03 mm, the spindle speed of the machine tool is 300 r / min, the grinding head speed is 1900 r / min, and the axial feed is 28 mm / min; The grinding depth of the fine grinding is 0.02 mm, the spindle speed of the machine tool is 300 r / min, the grinding head speed is 2000 r / min, and the axial feed is 24 mm / min.

[0010] Alternatively, in step four, the grinding tool is made of silicon carbide.

[0011] As one possible approach, in step five: Rough polishing uses an 800-mesh polishing wheel, with a machine tool spindle speed of 300 r / min, a polishing wheel speed of 1600 r / min, and an axial feed of 28 mm / min, ensuring a surface roughness of Ra0.4; Fine polishing uses a 1000-grit polishing wheel, with a machine tool spindle speed of 300 r / min, a polishing wheel speed of 1800 r / min, and an axial feed of 26 mm / min, ensuring a surface roughness of Ra0.2; Fine polishing uses a 1200-grit polishing wheel, with a machine spindle speed of 300 r / min, a polishing wheel speed of 2000 r / min, and an axial feed of 24 mm / min, ensuring a surface roughness of Ra0.08.

[0012] Alternatively, in step five, the polishing tool is a chamois polishing wheel.

[0013] The wear-resistant bushing of this invention is uniformly loaded and assembled into the support casing, achieving a good assembly condition. Using spiral grinding instead of turning reduces tool wear and machining costs. Selecting appropriate grinding steps and parameters ensures the shape tolerance of the hardened inner hole of the wear-resistant bushing in the support casing. Spiral polishing using a chamois polishing wheel, along with appropriate polishing steps and parameters, not only controls the surface roughness to within Ra0.1 but also reduces polishing time from 12 hours to 30 minutes. Attached Figure Description

[0014] Figure 1 This is a view of the wear-resistant bushing of the support-type casing of the present invention; Figure 2 This is a schematic diagram of the abrasive used in this invention; Figure 3 This is the intention behind the polishing wheel used in this invention. Detailed Implementation

[0015] The present invention will be further described below with reference to specific embodiments, but it should not be construed as limiting the scope of the subject matter of the present invention to the following embodiments. All modifications, substitutions and alterations made based on ordinary technical knowledge and common practices in the art without departing from the above-described technical concept of the present invention are included within the scope of the present invention.

[0016] See Figure 1 , Figure 2 and Figure 3 This invention provides a method for machining the hard inner hole surface of a wear-resistant bushing for a support-type casing. The specific method is as follows: Step 1: Allowance and cylindricity control before fitting the wear-resistant bushing. Before installing the hard inner hole of the wear-resistant bushing into the support casing, 0.1mm should be left on one side, and the cylindricity should be controlled within 0.01mm to provide sufficient allowance for grinding and machining adjustment.

[0017] Step two, the assembly of the wear-resistant bushing and the support casing. During the assembly of the wear-resistant bushing into the support casing, the wear-resistant bushing must be subjected to uniform force, and each area must enter the support casing hole axially at the same time. It cannot be rotated or twisted during installation. Special tooling can be used for this assembly process.

[0018] Step 3: Clamping and alignment during grinding and polishing of support-type casings. When clamping and aligning support-type casings during grinding and polishing, the hard inner hole of the wear-resistant bushing needs to be roughly aligned to the reference circle first, and then the reference circle needs to be finely aligned to eliminate the influence of the flatness and cylindricity of the wear-resistant bushing itself.

[0019] The rough alignment reference circle is used to align the wear-resistant bushing's hard inner hole within a range of 0.05mm, and the runout of the hard bushing end face is within a range of 0.04mm.

[0020] The precise alignment reference circle is within 0.008mm of the hard inner hole of the wear-resistant bushing, and the runout of the hard bushing end face is within 0.008mm. This involves using appropriate T-blocks, screws, shoulder nuts, washers, pressure plates, and other auxiliary tooling to fix and tighten the support casing. During tightening, a dial indicator should be pressed against the surface of the wear-resistant bushing. Observe whether the dial indicator reading changes. If the reading changes, it indicates that the support casing at that tightening point has shifted or is deformed. In this case, realignment (physical compensation, replacement of pressure plates, etc.) is necessary, followed by re-tightening until the dial indicator reading changes within 0.008mm after tightening. This indicates that the error and deformation of the support casing caused during installation, alignment, and tightening are minimal.

[0021] Step 5, grinding, is carried out in three steps: rough grinding, fine grinding and precision grinding. The grinding method is spiral polishing to ensure the shape tolerance of the hard inner hole of the wear-resistant bushing of the support casing. The grinding tool used is made of silicon carbide.

[0022] The rough grinding depth is 0.05 mm, the machine tool spindle speed is 300 r / min, the grinding head speed is 1800 r / min, and the axial feed is 30 mm / min.

[0023] The fine grinding depth is 0.03 mm, the machine tool spindle speed is 300 r / min, the grinding head speed is 1900 r / min, and the axial feed is 28 mm / min.

[0024] The grinding depth of the fine grinding is 0.02 mm, the spindle speed of the machine tool is 300 r / min, the grinding head speed is 2000 r / min, and the axial feed is 24 mm / min.

[0025] Step six, polishing, is carried out in three steps: rough polishing, fine polishing and precision polishing. The polishing method is spiral polishing to ensure the surface roughness of the hard inner hole of the wear-resistant bushing of the support casing. The grinding tool used is a chamois polishing wheel.

[0026] For rough polishing, an 800-mesh polishing wheel is used, the machine tool spindle speed is 300 r / min, the polishing wheel speed is 1600 r / min, and the axial feed is 28 mm / min, ensuring a surface roughness of approximately Ra0.4.

[0027] Fine polishing uses a 1000-grit polishing wheel, with a machine spindle speed of 300 r / min, a polishing wheel speed of 1800 r / min, and an axial feed of 26 mm / min, ensuring a surface roughness of approximately Ra0.2.

[0028] Fine polishing uses a 1200-grit polishing wheel, with a machine spindle speed of 300 r / min, a polishing wheel speed of 2000 r / min, and an axial feed of 24 mm / min, ensuring a surface roughness of approximately Ra0.08.

[0029] Contents not described in detail in this specification are prior art known to those skilled in the art. Although illustrative specific embodiments of the invention have been described above to facilitate understanding by those skilled in the art, it should be understood that the invention is not limited to the scope of the specific embodiments. Various modifications are readily apparent to those skilled in the art as long as they fall within the spirit and scope of the invention as defined and determined by the appended claims, and all inventions utilizing the concept of this invention are protected.

Claims

1. A method for machining the hard inner hole surface of a wear-resistant bushing for a support-type casing, characterized in that, include: Step 1: Controlling the allowance and cylindricity before assembling the wear-resistant bushing. Before installing the hard inner hole of the wear-resistant bushing into the support type casing, allowance should be left on one side, and the cylindricity should be controlled within 0.01mm to provide allowance for grinding adjustment. Step 2, assembly of wear-resistant bushings. During the assembly of wear-resistant bushings into the support housing, they should be subjected to uniform force. All areas of the wear-resistant bushing should enter the support housing hole axially at the same time. They should not be rotated or twisted during installation. Step 3: Grind, polish, clamp and align the support casing. First, roughly align the reference circle of the hard inner hole of the wear-resistant bushing, and then finely align the reference circle to eliminate the influence of the flatness and cylindricity of the wear-resistant bushing itself. Step four: Grinding is carried out in sequence using coarse grinding, fine grinding, and precision grinding. The grinding method is spiral grinding and polishing to ensure the shape tolerance of the hard inner hole of the wear-resistant bushing of the support casing. Step 5: Polishing is carried out sequentially using coarse polishing, fine polishing, and precision polishing. The polishing method is spiral polishing to ensure the surface roughness of the hard inner hole of the wear-resistant bushing of the support casing.

2. The method for machining the hard inner hole surface of a support-type casing wear-resistant bushing according to claim 1, characterized in that, In step three: The rough alignment reference circle is within 0.05mm of the inner hole of the wear-resistant bushing, and the runout of the end face of the wear-resistant bushing is within 0.04mm. The precise alignment reference circle is within 0.008mm of the inner hole of the wear-resistant bushing, and the runout of the end face of the wear-resistant bushing is within 0.008mm.

3. The method for machining the hard inner hole surface of a support-type casing wear-resistant bushing according to claim 2, characterized in that, In step three: When precisely aligning the reference circle, use T-blocks, screws, shoulder nuts, pads, or pressure plates to fix and tighten the support housing. During the tightening process, press a dial indicator against the surface of the wear-resistant bushing and observe whether the dial indicator reading changes. If the dial indicator reading changes, it indicates that the support housing at the tightened part has shifted or is deformed. It must be realigned and tightened until the change in the dial indicator reading at the alignment point is within 0.008mm after tightening.

4. The method for machining the hard inner hole surface of a support-type casing wear-resistant bushing according to claim 1, characterized in that: In step one, the hard inner hole of the wear-resistant bushing is left with a 0.1mm margin on one side before it is installed into the support-type casing; In step four: The grinding depth for rough grinding is 0.05 mm, the machine tool spindle speed is 300 r / min, the grinding head speed is 1800 r / min, and the axial feed is 30 mm / min. The grinding depth of fine grinding is 0.03 mm, the spindle speed of the machine tool is 300 r / min, the grinding head speed is 1900 r / min, and the axial feed is 28 mm / min; The grinding depth of the fine grinding is 0.02 mm, the spindle speed of the machine tool is 300 r / min, the grinding head speed is 2000 r / min, and the axial feed is 24 mm / min.

5. The method for machining the hard inner hole surface of a wear-resistant bushing for a support-type casing according to claim 1, characterized in that: In step four, the grinding tool is made of silicon carbide.

6. The method for machining the hard inner hole surface of a wear-resistant bushing for a support-type casing according to claim 1, characterized in that, In step five: Rough polishing uses an 800-mesh polishing wheel, with a machine tool spindle speed of 300 r / min, a polishing wheel speed of 1600 r / min, and an axial feed of 28 mm / min, ensuring a surface roughness of Ra0.4; Fine polishing uses a 1000-grit polishing wheel, with a machine tool spindle speed of 300 r / min, a polishing wheel speed of 1800 r / min, and an axial feed of 26 mm / min, ensuring a surface roughness of Ra0.2; Fine polishing uses a 1200-grit polishing wheel, with a machine tool spindle speed of 300 r / min, a polishing wheel speed of 2000 r / min, and an axial feed of 24 mm / min, ensuring a surface roughness of Ra0.

08.

7. The method for machining the hard inner hole surface of a support-type casing wear-resistant bushing according to claim 1, characterized in that: In step five, the polishing tool is a chamois polishing wheel.

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