A method for machining a compressor front cover

Abstract

The application discloses a compressor front cover processing method, comprising the following steps: a, front cover processing: the complete shape of the front cover is processed, and the pin hole and the shaft head pump mounting hole are coarsely processed to reserve a finishing allowance; b, machine body processing; c, front cover installation; d, pin hole processing; e, pin installation; f, mounting hole finishing processing: taking the bearing position center coordinates of the machine body as a reference, the shaft head pump mounting holes on the front cover and the machine body are synchronously finished on the numerical control boring machine by using a long blade boring cutter. Through the above steps, the coaxiality of the mounting holes on the front cover and the machine body is higher, and the front cover is conveniently installed.

Description

Technical Field

[0001] This invention relates to the field of compressor technology, and in particular to a method for processing a compressor front cover. Background Technology

[0002] The existing compressor body and front cover are processed separately. The body is first roughed and finely machined, and then the body is removed from the machine tool. The front cover is then roughed and finely machined, and then the front cover is disassembled and reassembled to complete the production of the compressor housing.

[0003] However, the main component of a compressor is the compression pump. During installation, the shaft of the pump needs to pass through the mounting holes on the body and the front cover. The above processing method will cause the coaxiality of the pump mounting holes on the body and the front cover to be inaccurate. During the assembly of the compressor, experienced workers need to manually correct it, and after disassembly and inspection, the coaxiality needs to be recalibrated, which will affect the use of the compressor. Summary of the Invention

[0004] This application provides a method for processing a compressor front cover, using the following technical solution:

[0005] A method for processing a compressor front cover includes the following steps:

[0006] a. Front cover machining: Machining the complete shape of the front cover, and rough machining the pin hole and the mounting hole of the shaft pump, leaving allowance for finishing; wherein, at least one process boss or positioning groove is machined on the mating surface of the front cover and the machine body; a guide hole is pre-drilled in the center of the pin hole, and the diameter of the guide hole is 30% to 40% of the final pin hole diameter;

[0007] b. Machine body machining: The rough blank of the machine body is machined on a CNC boring machine to complete the machining of the front cover mounting surface, and a corresponding structure matching the process boss or positioning groove is machined on the mounting surface; the mounting holes of the machine body are rough machined and allowance is reserved, but the positioning pin holes are not machined; the machining coordinate system of the machine body is recorded during the machining process, and a temporary coordinate system model is generated;

[0008] c. Front cover installation: The front cover is pre-positioned with the corresponding structure on the machine body through the process boss or positioning groove, and the front cover is fixed to the machine body with bolts on the CNC boring machine, so that the front cover and the machine body are combined into one piece;

[0009] d. Pin hole machining: On the CNC boring machine, the same boring tool is used to simultaneously finish machine the pin holes on the front cover and the machine body;

[0010] e. Pin installation: Insert the pin into the precision-machined pin hole;

[0011] f. Precision machining of mounting holes: Using the center coordinates of the bearing position of the machine body as a reference, the mounting holes of the shaft pump on the front cover and the machine body are precision machined simultaneously using a long-bladed boring tool on the CNC boring machine.

[0012] By adopting the above technical solution, the front cover and the machine body are easy to process. However, the mounting holes of the shaft pump on the front cover and the machine body are rough-machined. Then, the machine body is not removed for boring. Therefore, while keeping the coordinate system of the machine body itself unchanged, the front cover is installed on the machine body. Then, the mounting holes of the shaft pump are precision-machined. This ensures the coaxiality of the mounting holes on the front cover and the machine body. Therefore, during the subsequent assembly of the compressor, it is not necessary to repeatedly adjust the coaxiality, thus improving work efficiency.

[0013] Optionally, in step a, the fit tolerance between the aforementioned process boss or positioning groove and the corresponding structure on the machine body is H7 / g6.

[0014] By adopting the above technical solution, by setting auxiliary positioning structures on the front cover and the machine body, and by combining the CNC system to record and call the machine body coordinates in real time, "physical + digital" dual positioning is achieved, which greatly reduces random errors in the installation process and ensures the consistency of the combined machining coordinate system.

[0015] Optionally, in step d, tooling bolts with torque limiting are used for fixing to ensure that the gap between the front cover and the machine body is ≤0.02mm; after installation, the temporary coordinate system model is called in the CNC system, and the front cover is incorporated into the same coordinate system.

[0016] By adopting the above technical solution, the consistency of the coordinate system can be further guaranteed, thereby ensuring coaxiality during processing.

[0017] Optionally, in step d, a double-edged stepped boring tool is used for machining. First, its short cutting edge is used to perform semi-finishing on the pin hole of the front cover, and then its long cutting edge is used to simultaneously perform one-time precision boring on the pin holes of the front cover and the machine body. During machining, the spindle speed and feed rate are adaptively adjusted according to the laminate thickness of the materials of the front cover and the machine body.

[0018] By adopting the above technical solution, the double-edged stepped boring tool does not require tool changing during the machining process, which means it does not need to find the coordinate system origin again, thus further ensuring coaxiality during the machining process.

[0019] Optionally, in step e, the pin is a segmented pin, with the middle segment being a positioning segment and both ends being guide segments, the diameter of which is smaller than the hole diameter.

[0020] By adopting the above technical solution, the segmented pins facilitate pin insertion and ensure their secure fastening, preventing misalignment between the front cover and the body.

[0021] Optionally, in step f, during finishing, an online probe is integrated on the boring bar to detect the hole diameter and roundness in real time and provide feedback for tool compensation adjustment; the boring bar is a vibration suppression boring bar with an internally integrated damping unit; after machining, a laser interferometer or pneumatic gauge is used on the machine tool to detect the coaxiality of the mounting holes on the front cover and the machine body.

[0022] By adopting the above technical solutions, coaxiality can be better monitored, thereby improving the accuracy of machining.

[0023] Optionally, the boring bar is inclined to the horizontal plane, and the included angle between the boring bar and the horizontal plane is α1, where 50°<α1<60°.

[0024] By adopting the above technical solution, from this angle, the cooling water can better flush and cool the cutting area, and can also better carry away the cooling water.

[0025] Optionally, the front end of the boring bar is provided with a cooling pipe, which faces the cutting edge of the boring bar, and the angle between the cooling pipe and the vertical direction of the boring bar is β, where 40° < β < 60°.

[0026] By adopting the above technical solution, the boring bar can divide the cooling water, so that the cooling water falls on the two surfaces of the boring bar, thereby improving working efficiency. At the same time, it can also prevent the cooling water from exerting an impact force on the boring bar that would cause it to move.

[0027] In summary,

[0028] 1. The mounting holes on the front cover and the body are rough machined separately. Then, without disassembling the body and without changing the coordinate system, the front cover is installed on the body. Then, the mounting holes are finely machined. This ensures the coaxiality of the mounting holes on the front cover and the body. Therefore, it is not necessary to search for coaxiality multiple times during assembly, which can improve the assembly efficiency.

[0029] 2. Cooling water flows from the inside out, and there is an angle between the cooling pipe and the boring tool. This not only improves cooling efficiency but also cleans up debris, reducing the impact of debris on the finishing of the mounting holes. Attached Figure Description

[0030] Figure 1 This is a schematic diagram of the angle between the cooling pipe and the boring tool in Embodiment 2.

[0031] Figure 2 This is a schematic diagram of the angle between the cooling pipe and the boring tool in Example 3.

[0032] Figure 3 This is a schematic diagram of the angle between the cooling pipe and the boring tool in Example 4.

[0033] Explanation of reference numerals in the attached figures:

[0034] 1. Cooling pipe; 2. Boring tool. Detailed Implementation

[0035] This application discloses a method for processing a compressor front cover. The processing method includes the following steps:

[0036] a. Front cover machining: First, the front cover is machined to obtain its complete shape; the pin hole and the mounting hole of the shaft pump are rough machined, leaving a finishing allowance; except for the pin hole and the mounting hole, all other parts are machined.

[0037] b. Machine body machining: The rough blank of the machine body is machined using a CNC boring machine; in particular, the installation position of the front cover must be machined, but the positioning pin holes are not machined; after the rough blank of the machine body is machined, it should be noted that the machine body cannot be removed from the CNC boring machine, and the machining positioning must be maintained and cannot be changed.

[0038] c. Front cover installation: The front cover and the machine body are assembled on a CNC boring machine. After the front cover is aligned and installed on the machine body, it is fixed with bolts. After the front cover and the machine body are assembled together, proceed to the next step.

[0039] d. Pin hole machining: While precision machining the pin holes on the front cover, the pin holes on the machine body are machined simultaneously.

[0040] e. Pin installation: Insert the pin into the pin hole for positioning;

[0041] f. Hole Finishing: Finally, the mounting holes on the front cover and machine body are precision machined. Using the bearing center coordinates as a reference, the shaft head pump mounting hole is precision machined to ensure coaxiality between the machined hole on the front cover and the bearing mounting position. Simultaneous finishing of the mounting holes during the machining process ensures coaxiality, facilitates the installation of the front cover, and guarantees the coaxial accuracy between the front cover shaft head pump mounting hole and the machine body bearing mounting position when both are disassembled and reinstalled.

[0042] In step b, the machine body machining will utilize a CNC boring machine to bore holes in the rough blank of the machine body and machine the mounting position of the front cover. During the machining process, the shape of the machine body and various holes other than mounting holes and pin holes will be machined, including preliminary roughing and finishing. This allows for more precise machining without adjusting the machining coordinates. However, the pin holes will not be machined and will be machined in a later step to ensure accurate positioning. The mounting holes will also only be roughed, leaving machining allowance to facilitate subsequent finishing.

[0043] The machining of the machine body is completed on a CNC boring machine. During the machining process, the machine tool coordinate system coordinates of each key surface are recorded in real time, and a "temporary coordinate system model" of the machine body in this clamping state is generated.

[0044] A corresponding structure matching the front cover's process boss / groove is machined near the front cover mounting surface to assist in installation and positioning.

[0045] When roughing the mounting holes, stepped boring is used, and uneven allowances are reserved (such as slightly larger allowances near the front cover and slightly smaller allowances away from the front cover) to compensate for possible deformations during subsequent assembly machining.

[0046] In step c, in order to improve the precision of machining, the front cover is directly installed on the machine body of the boring machine. During the installation process, the machine body will not be removed from the boring machine, so the coordinate system will not change. Therefore, the re-machining of the front cover is also based on the coordinate system of the machine body, which will make the subsequent installation of the front cover more precise with the machine body, thereby improving the efficiency of assembly.

[0047] When installing the front cover, first use the process boss / groove to achieve initial fit, and then use tooling bolts with torque limiting to pre-tighten evenly to ensure that the gap between the mating surfaces is ≤0.02mm.

[0048] After installation, the temporary coordinate system model recorded in step b is called in the CNC system, and the front cover is regarded as an extension of the machine body and incorporated into the same machining coordinate system to achieve coordinate system unification.

[0049] In step d, the boring bar first processes the pin holes on the machine body through the pin holes on the front cover. After the rough machining of the pin holes on the machine body is completed, the pin holes on both the front cover and the machine body are simultaneously precision machined to ensure the coaxiality of the pin holes. Step f involves inserting the pins, primarily for precise positioning. Bolt fixing installation has a certain degree of error; the precise positioning function of the pins facilitates the subsequent disassembly and reassembly of the front cover without repeatedly searching for coaxiality.

[0050] Using a double-edged stepped boring tool, the short cutting edge is first used to semi-finish the pin hole of the front cover (removing most of the excess material), and then the long cutting edge is used to simultaneously perform one-time precision boring of the pin holes of the front cover and the body.

[0051] During machining, the spindle speed and feed rate are adaptively adjusted according to the thickness of the material layers to maintain stable cutting force.

[0052] In step e, the pin is made of a low-temperature expansion alloy material. After being cooled and shrunk in liquid nitrogen, it is inserted into the pin hole. After returning to room temperature, it forms an interference fit with the hole wall to achieve gapless positioning.

[0053] Alternatively, a segmented pin can be used, with the middle section serving as a positioning section and both ends as guide sections. The diameter of the guide sections is slightly smaller than the hole diameter, which facilitates assembly and ensures positioning accuracy.

[0054] In step f, after ensuring the front cover is stably installed, the boring bar begins machining the mounting holes of the shaft head pump. Since the diameter of the mounting holes on the machine body is 2-4mm smaller than that on the front cover, the mounting holes on the machine body are machined first during finishing, allowing for better monitoring of the machining progress. A long-bladed boring bar is used, allowing for simultaneous machining of the mounting holes on both the front cover and the machine body after finishing begins. During machining, the coordinate system of the machine body remains unchanged, ensuring that the coordinate system of the mounting holes on the front cover is identical to that of the machine body. This results in higher coaxiality between the mounting holes on the front cover and the machine body, facilitating the installation of the shaft head pump. Furthermore, repeated disassembly and reassembly of the front cover eliminates the need to repeatedly search for coaxiality, improving installation efficiency.

[0055] When finishing the mounting holes, an online probe is integrated on the boring bar. After each cut, the hole diameter and roundness are detected in real time, and the tool compensation is dynamically adjusted based on the feedback data.

[0056] The vibration suppression boring bar, with an integrated damping unit, can suppress chatter generated by boring tools with a large length-to-diameter ratio during synchronous machining.

[0057] After processing, the workpiece is not immediately disassembled. Instead, a laser interferometer or pneumatic gauge is used on the machine tool to check the coaxiality of the front cover and the mounting hole of the machine body. Only after it passes the test can it be removed. Example

[0058] In this embodiment, in step a, after the rough machining of the front cover is completed, one or more process bosses or positioning grooves are reserved on the mating surface between the front cover and the body. The bosses / grooves are used to assist in pre-positioning during subsequent assembly with the body, avoiding micro-movement deviations caused by relying entirely on bolt tightening.

[0059] The rough machining allowance for the pin hole is still 2-3mm, but a guide hole is pre-drilled in the center of the pin hole. The diameter of the hole is 30% to 40% of the final pin hole diameter, and the depth penetrates the thickness of the front cover. This is to facilitate the centering of the boring tool during subsequent finishing, which is convenient for the boring tool and can also improve the machining efficiency. It avoids excessive allowance, which would require multiple adjustments to the feed size and affect work efficiency.

[0060] Fit clearance data: The boss and groove adopt an H7 / g6 tolerance fit. Calculations and tests show that this fit can be assembled under light pressure (<100N), and the average fit clearance is 0.01-0.025mm. This clearance is sufficient to eliminate macroscopic misalignment before bolt tightening without affecting assembly efficiency due to interference.

[0061] Positioning contribution: Through comparison with a coordinate measuring machine, the solution of pre-positioning the process boss + bolt fastening, compared with the solution of blindly fastening the bolts alone, reduced the average deviation of the initial surface profile of the front cover and the mounting surface of the body by 75% (from an average of 0.08mm to less than 0.02mm). Example

[0062] Reference Figure 1 In step f, during the machining of the mounting holes, cooling water needs to be added. It's important to note that the cooling water should first be flushed from the outside of the machine body to facilitate its distribution and to flush away debris. The flushing force of the cooling water should be maintained at 30-45 MPa, so that the water flow not only has a cooling function but also flushes away and removes machining debris.

[0063] Cooling pipe 1 is located behind boring tool 2, forming an angle of 25°–35° with the axis of boring tool (see 1, the optimization basis of cooling pipe angle α (30°<α<50°)). The coolant is a biodegradable, high-penetration cutting fluid with a pressure of 35–50 MPa (see section 2, "Determination of Coolant Pressure (30–45 MPa)"). A trace amount of solid lubricating particles (such as nano-graphite) are added to form a lubricating film on the hole wall during cooling, reducing boring tool wear. The angle between the axis of the cooling pipe 1 and the axis of the boring tool 2 is α (30° < α < 50°). Within this angle range, the cooling water sprayed from the cooling pipe 1 can better flush away debris and reduce wear. Furthermore, the cooling pipe 1 is positioned on the opposite side of the boring tool 2's travel direction, reducing the impact of cooling water on the boring tool 2's displacement and its impact on machining progress. The inclined setting of the cooling pipe 1 causes the water jets to impact the boring tool 2 and the machining surface of the mounting hole, generating splashes that are better sprayed onto the machining surface and the boring tool 2. These splashed water droplets are better evaporated, resulting in a better cooling effect.

[0064] The coolant spray path has been optimized through simulation to ensure that it covers the cutting area and does not directly impact the tool tip, thus avoiding thermal shock that could cause micro-chipping of the cutting tool.

[0065] 1. Optimization basis for the included angle α of the cooling pipes (30° < α < 50°):

[0066] Theoretical simulation (CFD analysis): The coolant impingement flow field was simulated using computational fluid dynamics software. Results show:

[0067] When α < 30°, the coolant jet is too straight, resulting in insufficient coverage of the cutting area at the rear of the boring tool (< 60%), and a weak backward pushing force on the chips.

[0068] When α=40°, the jet can form the optimal vortex, which extends the residence time of the coolant in the cutting zone by about 35%, increases the effective cooling coverage to more than 85%, and achieves the highest chip removal efficiency.

[0069] When α > 50°, the vertical component of the jet is too large, resulting in severe liquid splashing, reduced utilization, and a large radial force acting on the boring bar, which may introduce micro-vibration (simulation shows that the radial force increases by about 15%).

[0070] Experimental data: When machining the assembly of a cast iron body and an aluminum alloy front cover, the tool life and hole wall roughness (Ra) at different α angles were compared:

[0071] Therefore, 35°-45° is the optimal range that balances tool life, machining quality, and cleanliness.

[0072] 2. Determination of coolant pressure (30-45 MPa)

[0073] Chip size analysis: The average length of cast iron chips produced during finishing is approximately 2-5 mm, and the curling diameter is approximately 0.3 mm. Fluid dynamic calculations show that the minimum dynamic pressure required to stably propel such chips backward along the hole wall is approximately 25 MPa.

[0074] Experimental verification: With α=40° fixed, tests were conducted by changing the pressure:

[0075] Orifice temperature difference: refers to the temperature difference between the orifice opening and the bottom area immediately after processing, reflecting the uniformity of cooling.

[0076] Therefore, chip removal is incomplete when the pressure is below 30 MPa; above 45 MPa, energy consumption increases dramatically while the marginal effect of cooling benefits diminishes significantly, and the working environment deteriorates. 35-40 MPa is the optimal economic and technical balance point. Example

[0077] The difference between this embodiment and Embodiment 1 is that the cooling pipe 1 is located on one side of the boring bar 2's travel direction, and the boring bar 2 is also inclined. The angle between the boring bar 2 and the plane is α1 (50° < α1 < 60°). At this angle, it is possible to process the mounting hole and also to mitigate the impact of the cooling water, preventing the boring bar 2 from shifting under the impact of the cooling water. At the same time, because the cooling water is directed towards the boring bar 2, the debris is directly washed away by the cooling water after being cut off, which makes the debris cleaner.

[0078] The mechanical analysis of the boring tool tilt angle (α1: 50°<α1<60°) is as follows:

[0079] Cutting force decomposition: The main cutting force Fc is decomposed into axial force Fa and radial force Fr. When α1 increases, Fa increases and Fr decreases. Actual measurements using a force gauge show that during the machining of the material:

[0080] When α1=55°, the radial force Fr is reduced by about 30% compared to when α1=45°, which is extremely beneficial for suppressing the tool deformation of the long boring bar and ensuring the straightness of the hole.

[0081] The increase in axial force can be easily borne by the rigidity of the machine tool's Z-axis.

[0082] Coolant impact mitigation: When the cooling pipe is located on the same side as the direction of travel, the inclined rake face of the boring bar can convert part of the coolant impact force into a sliding force along the tool face backward, rather than a direct radial disturbance force. Simulations show that at a 55° inclination angle, the potential radial displacement caused by cooling impact can be reduced by about 60% compared to the 90° vertical state. Example

[0083] The difference between this embodiment and the two embodiments mentioned above is that: the cooling pipe 1 is located at the front end of the boring bar 2, parallel to the forward direction of the boring bar 2, and the angle between the axis of the cooling pipe 1 and the vertical direction of the boring bar 2 is β (40° < β < 60°). Under the action of the cooling pipe 2 set in this way, the cooling water can impact the cutting surface to achieve the purpose of cooling, and can also wash away the chips. At the same time, the cutting edge of the boring bar 2 will cut the flow of cooling water, so that the cooling water falls on the two surfaces of the boring bar 2, thereby achieving better cooling. Example

[0084] It adopts a dual-channel cooling system: one channel is high-pressure clean water cooling, which is mainly used for cooling and chip removal; the other channel is a micro-lubrication system (MQL), which atomizes a very small amount of lubricating oil and sprays it onto the tool-chip contact area to reduce cutting resistance.

[0085] The cooling pipe outlet is located on the side of the boring tool and is equipped with an ultrasonic vibration device to generate a cavitation effect in the coolant, thereby enhancing the chip removal and hole wall cleaning effect.

[0086] The above are all preferred embodiments of this application, and are not intended to limit the scope of protection of this application. Therefore, all equivalent changes made in accordance with the structure, shape and principle of this application should be covered within the scope of protection of this application.

Claims

1. A method for processing a compressor front cover, characterized in that: Includes the following steps: a. Front cover machining: Machining the complete shape of the front cover, and rough machining the pin hole and the mounting hole of the shaft pump, leaving allowance for finishing; wherein, at least one process boss or positioning groove is machined on the mating surface of the front cover and the machine body; a guide hole is pre-drilled in the center of the pin hole, and the diameter of the guide hole is 30% to 40% of the final pin hole diameter; b. Machine body machining: The rough blank of the machine body is machined on a CNC boring machine to complete the machining of the front cover mounting surface, and a corresponding structure matching the process boss or positioning groove is machined on the front cover mounting surface; the mounting holes of the machine body are rough machined and allowance is reserved, but the positioning pin holes are not machined; the machining coordinate system of the machine body is recorded during the machining process, and a temporary coordinate system model is generated; c. Front cover installation: The front cover is pre-positioned with the corresponding structure on the machine body through the process boss or positioning groove, and the front cover is fixed to the machine body with bolts on the CNC boring machine, so that the front cover and the machine body are combined into one piece; d. Pin hole machining: On the CNC boring machine, the same boring tool is used to simultaneously finish machine the pin holes on the front cover and the machine body; e. Pin installation: Insert the pin into the precision-machined pin hole; f. Precision machining of mounting holes: Using the center coordinates of the bearing position of the machine body as a reference, the mounting holes of the shaft pump on the front cover and the machine body are simultaneously precision machined using a long-bladed boring tool on the CNC boring machine. In step d, a double-edged stepped boring tool is used for machining. First, the short cutting edge is used to perform semi-finishing of the front cover pin hole, and then the long cutting edge is used to simultaneously perform one-time precision boring of the pin holes of the front cover and the machine body. During machining, the spindle speed and feed rate are adaptively adjusted according to the laminate thickness of the front cover and the machine body materials. In step e, the pin is a segmented pin, with the middle section being a positioning section and both ends being guide sections, the diameter of which is smaller than the hole diameter; In step f, during finishing, an online probe is integrated on the boring bar to detect the hole diameter and roundness in real time and provide feedback to adjust the tool compensation; the boring bar is a vibration suppression boring bar with an internally integrated damping unit; after machining, a laser interferometer or pneumatic gauge is used on the machine tool to detect the coaxiality of the front cover and the mounting hole on the machine body; The boring bar is inclined to the horizontal plane, and the angle between the boring bar and the horizontal plane is α1, where 50°<α1<60°.

2. The method for processing a compressor front cover according to claim 1, characterized in that: In step a, the fit tolerance between the aforementioned process boss or positioning groove and the corresponding structure on the machine body is H7 / g6.

3. The method for processing a compressor front cover according to claim 1, characterized in that: In step d, tooling bolts with torque limiting are used for fixing to ensure that the gap between the front cover and the machine body is ≤0.02mm; after installation, the temporary coordinate system model is called in the CNC system to incorporate the front cover into the same coordinate system.

4. A method for processing a compressor front cover according to claim 1, characterized in that: The front end of the boring bar is provided with a cooling pipe, which faces the cutting edge of the boring bar. The angle between the cooling pipe and the vertical direction of the boring bar is β, where 40° < β < 60°.

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