Machining method for reducing allowance of bottom hole of seat ring

Abstract

The invention relates to the technical field of engine cylinder cover machining, in particular to a machining method for reducing the allowance of a seat ring bottom hole. The method is suitable for engine cylinder cover seat ring bottom hole machining in a drilling and tapping center and comprises the steps that after a workpiece is fixed, blank allowance distribution data are obtained through laser detection, a large allowance area and a conventional allowance area are divided, a graded rough machining path is planned, graded rough machining is executed through differential cutting parameters, and a high-pressure cooling system is started synchronously to be matched with chip breaking. And finally, reinspection is conducted through laser detection, and if the product is not qualified, path planning is conducted again for machining. According to the method, precise workpiece allowance area division is achieved, then the workpiece allowance is controlled, the tool damage risk can be reduced, chip breaking is stabilized, and the machining efficiency and the workpiece qualification rate can be remarkably improved; the problems that due to the fact that the allowance of a gravity casting engine cylinder cover blank is irregular and too large, the allowance of a seat ring bottom hole is large, a cutter is prone to being damaged, and aluminum scraps cannot be effectively broken are solved.

Description

Technical Field

[0001] This invention relates to the field of engine cylinder head machining technology, and in particular to a machining method for reducing the allowance of the bottom hole of the cylinder head bearing. Background Technology

[0002] The valve seat bottom hole is a key assembly part of the engine cylinder head. Its machining accuracy directly affects the assembly quality of the valve seat and the running stability of the engine. Therefore, the machining of the valve seat bottom hole usually requires two core processes: roughing and finishing, to be completed on a drilling and tapping center. In order to avoid insufficient machining due to blank size deviation, the existing process usually reserves a large machining allowance, and uniform cutting parameters are often used to complete the machining of the entire area during the roughing process. However, existing machining methods have significant inherent defects in machining the bottom hole of the cylinder head seat ring in gravity casting, making it difficult to meet the needs of efficient and stable production. On the one hand, the gravity casting process itself easily leads to irregular distribution of allowance and excessive overall allowance in the cylinder head blank. Existing processes do not address these blank characteristics specifically, still using a uniform "one-cut" machining method, resulting in a generally large allowance in the machining area of ​​the bottom hole of the seat ring. Excessive machining allowance significantly increases the cutting load on the roughing reamer, accelerates tool wear, and may even cause chipping, breakage, and other damage, which not only increases tool usage costs but also leads to machining interruptions and reduces production efficiency. On the other hand, the cutting parameters and cooling methods of existing processes are not optimized for the cutting characteristics of aluminum (engine cylinder heads are mostly made of aluminum alloys). When machining large-allowance aluminum parts, aluminum chips tend to be continuous and long, making effective chip breaking impossible. Continuous aluminum chips can easily entangle the tool or workpiece, affecting the smoothness of the cutting process and potentially scratching the surface of the bottom hole of the seat ring, leading to a decrease in machining quality. At the same time, frequent manual cleaning of aluminum chips is required, further reducing machining efficiency. Summary of the Invention

[0003] This application discloses a machining method for reducing the machining allowance of the bottom hole of the cylinder head seat ring, in order to solve the technical problem of severe tool wear caused by the large machining allowance in the machining of the bottom hole of the cylinder head seat ring in the related art.

[0004] To solve the above problems, the present invention adopts the following technical solution: This invention provides a machining method for reducing the allowance of the bottom hole of a cylinder head seat ring, applied to a drilling and tapping center for machining the bottom hole of an engine cylinder head seat ring. The method includes the following steps: S1, fixing the gravity-cast engine cylinder head to the worktable of the drilling and tapping center using a fixture, and using a laser detection probe to perform a full-range scan of the machining area of ​​the bottom hole of the seat ring to obtain the blank allowance distribution data; S2, based on the blank allowance distribution data, dividing the machining area of ​​the bottom hole of the seat ring into a large allowance area and a normal allowance area, and planning a graded roughing path; S3, installing a roughing reamer, and driving the roughing reamer along the planned path to perform graded roughing: for the large allowance area, according to the... S1. Machining with a set of cutting parameters; For the area with the usual allowance, machining with a second set of cutting parameters to remove most of the allowance; S4. During roughing, the high-pressure cooling system is turned on simultaneously, and the coolant is sprayed evenly along the circumference of the roughing reamer to the cutting area, which, together with the cutting parameters, achieves chip breaking; S5. After roughing is completed, the finishing reamer is replaced, and the drilling and tapping center spindle drives the finishing reamer to perform finishing of the seat ring bottom hole, controlling the final allowance to be ≤0.15mm; S6. After finishing is completed, a laser inspection probe is used to inspect the allowance and surface quality of the seat ring bottom hole. If it is qualified, the machining is completed. If it is not qualified, return to step S2, replan the roughing path, and machine again.

[0005] Preferably, in step S1, the detection accuracy of the laser detection probe is 0.003mm, and five detection points are evenly selected along the axial and circumferential directions of the bottom hole of the seat ring during scanning to form a margin distribution data matrix.

[0006] Preferably, in step S2, the criterion for determining the large allowance area is that the blank allowance is >0.5mm, and the criterion for determining the conventional allowance area is that the blank allowance is ≤0.5mm.

[0007] Preferably, in step S3, the first set of cutting parameters is: rotational speed 4000-5000 r / min, feed rate 0.08-0.1 mm / r; the second set of cutting parameters is: rotational speed 6000-7000 r / min, feed rate 0.12-0.15 mm / r.

[0008] Preferably, in step S4, the coolant in the high-pressure cooling system is an emulsion, the injection pressure is 0.6-0.8 MPa, the injection flow rate is 15-20 L / min, and the coolant temperature is controlled at 20℃-30℃.

[0009] Preferably, in step S4, the shank of the roughing reamer is provided with a spiral chip removal groove, the width of which is 8-10mm.

[0010] Preferably, in step S5, the cutting parameters of the finishing reamer are: rotational speed 10000-12000 r / min, feed rate 0.05-0.08 mm / r, and the cutting edge of the finishing reamer is provided with a chamfer of 0.02-0.03 mm.

[0011] Preferably, in step S1, the clamping pressure of the fixture is 0.5-0.7 MPa, and a rubber buffer pad is provided on the contact surface between the fixture and the engine cylinder head blank.

[0012] Preferably, in step S6, the qualification criteria are: the allowance of each detection point of the seat ring bottom hole is ≤0.15mm, and the surface roughness Ra is ≤0.4um.

[0013] Preferably, in step S3, during the graded rough machining, the runout of the drill-tapping center spindle is controlled within 0.005 mm.

[0014] The technical solution adopted in this invention can achieve the following beneficial effects: 1. By setting a laser detection probe, full-range scanning is used to obtain the allowance distribution data, which can accurately identify the differences in allowance distribution in the machining area of ​​the seat ring bottom hole. By combining zonal planning of rough machining paths and graded cutting parameters, differentiated processing of large allowance areas and regular allowance areas can be achieved, avoiding excessive local allowance residue or over-cutting caused by one-cut machining. Ultimately, the final allowance of the seat ring bottom hole is stably controlled within 0.15mm, fundamentally solving the machining adaptability problem caused by the irregular allowance of gravity casting blanks.

[0015] 2. This solution employs a tiered roughing strategy. For areas with large allowances, a first set of cutting parameters with low speed and low feed rate is used, which can significantly reduce the cutting load per unit time and prevent tool damage due to excessive instantaneous force. For areas with normal allowances, a second set of appropriate cutting parameters is used, which ensures machining efficiency while avoiding excessive tool wear. Compared with existing uniform parameter machining, the tool wear rate is significantly reduced, thus reducing the frequency of tool replacement and tool usage costs.

[0016] 3. This solution uses a high-pressure cooling system to uniformly spray coolant along the circumference of the reamer, which is coordinated with the graded cutting parameters. The high-pressure coolant can cool the cutting area in time and flush away the chips. With the appropriate cutting parameters, the continuous forming conditions of aluminum chips are disrupted, causing the aluminum chips to break into broken chips. This avoids aluminum chips wrapping around the tool and causing machining interruption. At the same time, it prevents aluminum chips from scratching the surface of the bottom hole of the seat ring, thus ensuring the basic surface quality for subsequent finishing.

[0017] 4. After finishing, a laser inspection and re-inspection process is added. For unqualified workpieces, a new path is planned for secondary processing, forming a quality closed loop of inspection-processing-re-inspection. This can correct processing deviations in a timely manner, avoid workpiece scrap due to improper allowance control, and greatly improve the processing pass rate. At the same time, stable chip breaking eliminates the need for frequent manual cleaning of aluminum chips, and graded processing avoids ineffective cutting. The number of processing interruptions is reduced. Compared with the existing process, the processing time of the bottom hole of the seat ring of a single part is significantly shortened, improving production efficiency.

[0018] 5. After obtaining the allowance data through laser detection, the machining path is dynamically planned. There is no need to adjust the fixture or replace the special tool for gravity casting blanks with different allowance distributions. It can be adapted by simply optimizing parameters and paths, which reduces the process adjustment cost for irregular blanks and improves the versatility of the process. Attached Figure Description

[0019] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0020] Figure 1 This is a flowchart of a machining method for reducing the allowance of the bottom hole of a seat ring, as disclosed in some embodiments of this application. Figure 2 This is a schematic diagram of a roughing reamer in some embodiments of this application.

[0021] In the picture: 10. Rough machining reamer; 100. Spiral chip conveyor. Detailed Implementation

[0022] To make the objectives, technical solutions, and advantages of this invention clearer, the technical solutions of this invention will be described in detail below. Obviously, the described embodiments are merely some embodiments of this invention, and not all embodiments. Based on the embodiments of this invention, all other implementation methods obtained by those skilled in the art without creative effort are within the scope of protection of this invention.

[0023] The terms "first," "second," etc., used in the specification and claims of this application are used to distinguish similar objects and not to describe a specific order or sequence. It should be understood that such use of data can be interchanged where appropriate so that embodiments of this application can be implemented in orders other than those illustrated or described herein, and the objects distinguished by "first," "second," etc., are generally of the same class and the number of objects is not limited; for example, a first object can be one or more. Furthermore, in the specification and claims, "and / or" indicates at least one of the connected objects, and the character " / " generally indicates that the preceding and following objects are in an "or" relationship.

[0024] Existing methods for machining the bottom hole of the cylinder head seat ring of gravity-cast engine are not adapted to the irregular and excessive blank allowance. Using uniform cutting parameters results in a large allowance for the bottom hole of the seat ring, easy damage to the cutting tool, and ineffective chip breaking of aluminum chips, which affects both machining efficiency and quality.

[0025] The following is in conjunction with the appendix Figures 1 to 2 The present application provides a detailed description of a processing method for reducing the allowance of the bottom hole of the seat ring through specific embodiments and application scenarios.

[0026] This invention provides a machining method for reducing the allowance of the bottom hole of a cylinder head seat ring, applied to a drilling and tapping center for machining the bottom hole of an engine cylinder head seat ring. The method includes the following steps: S1, fixing the gravity-cast engine cylinder head to the drilling and tapping center worktable using a fixture, and using a laser detection probe to perform a full-range scan of the machining area of ​​the bottom hole of the seat ring to obtain the blank allowance distribution data; S2, based on the blank allowance distribution data, dividing the machining area of ​​the bottom hole of the seat ring into a large allowance area and a normal allowance area, and planning a graded roughing path; S3, installing a roughing reamer, and driving the roughing reamer along the planned path to perform graded roughing: for the large allowance area, according to the... S1. Machining with a set of cutting parameters; For the area with the usual allowance, machining with a second set of cutting parameters to remove most of the allowance; S4. During roughing, the high-pressure cooling system is turned on simultaneously, and the coolant is sprayed evenly along the circumference of the roughing reamer to the cutting area, which, together with the cutting parameters, achieves chip breaking; S5. After roughing is completed, the finishing reamer is replaced, and the drilling and tapping center spindle drives the finishing reamer to perform finishing of the seat ring bottom hole, controlling the final allowance to be ≤0.15mm; S6. After finishing is completed, a laser inspection probe is used to inspect the allowance and surface quality of the seat ring bottom hole. If it is qualified, the machining is completed. If it is not qualified, return to step S2, replan the roughing path, and machine again.

[0027] Specifically, in this embodiment, the engine cylinder head is made of gravity-cast aluminum alloy, and the fixture is a hydraulic three-jaw flat fixture, which is fixed to the drilling and tapping center worktable by T-bolts. The laser detection probe is a Keyence LK-G5000 series laser displacement sensor with a detection accuracy of 0.001mm and a scanning range of 0-50mm. This model has high detection accuracy and fast response speed, and can quickly complete the full range scan. In practical applications, other models can also be selected for this component, which are not limited here. The roughing reamer is made of cemented carbide with 4 teeth and a shank diameter of 20mm. The finishing reamer is made of PCD polycrystalline diamond with 6 teeth to ensure the surface quality of the finishing. The high-pressure cooling system includes a reservoir, a high-pressure pump, and an annular nozzle. The annular nozzle is sleeved on the outside of the roughing reamer shank, with 8 spray holes evenly distributed around the circumference, and the hole diameter is 0.8mm.

[0028] Understandably, the process begins by accurately obtaining the blank allowance distribution using a laser detection probe to identify the differences in allowance across different areas. Based on these differences, areas are divided and appropriate roughing paths are planned. Differentiated cutting parameters are used to reduce the cutting load in areas with large allowances, and high-pressure circumferential cooling is employed to break chips and prevent aluminum chips from entangled. Finally, finishing is used to control the final allowance, and a quality loop is formed through re-inspection to ensure that the machining is qualified.

[0029] Understandably, this solution effectively solves the problems of irregular and excessive blank allowances in gravity casting by achieving precise identification and differentiated processing of blank allowances. It stably controls the final allowance of the seat ring bottom hole within 0.15mm. Differentiated cutting parameters can reduce tool load, reduce the risk of tool damage, and extend tool life. High-pressure circumferential cooling and differentiated cutting parameters work together to achieve stable chip breaking, avoid aluminum chip entanglement and surface scratches, and the closed-loop re-inspection process can effectively improve the machining pass rate.

[0030] Furthermore, in step S1, the detection accuracy of the laser detection probe is 0.003mm. During scanning, five detection points are evenly selected along the axial and circumferential directions of the bottom hole of the seat ring to form a margin distribution data matrix.

[0031] Specifically, five axial inspection points are evenly distributed along the depth direction of the seat ring bottom hole, with a spacing of 5mm, covering the hole opening, middle of the hole, and bottom area; five circumferential inspection points are evenly distributed along the circumference of the seat ring bottom hole, with an included angle of 72° between adjacent inspection points; the allowance distribution data matrix is ​​stored in Excel format, with row coordinates representing axial inspection positions (in mm), column coordinates representing circumferential inspection angles (in °), and matrix values ​​representing the blank allowance (in mm) at the corresponding positions.

[0032] Specifically, precise calibration ensures the detection accuracy of the laser detection probe. Five detection points evenly distributed in the circumferential and axial directions form a scanning network that covers the entire area, ensuring that the acquired blank allowance data is comprehensive and accurate. Based on this data matrix, the allowance differences in different areas can be intuitively distinguished.

[0033] Understandably, this solution significantly improves the accuracy and comprehensiveness of the detection data, avoiding misjudgments of margin due to missing or insufficient scanning points, providing reliable data support for the subsequent division of large margin areas and regular margin areas, and effectively improving the zoning accuracy.

[0034] Furthermore, in step S2, the criterion for determining the large allowance area is that the blank allowance is >0.5mm, and the criterion for determining the normal allowance area is that the blank allowance is ≤0.5mm.

[0035] Specifically, the judgment criteria are determined based on the blank characteristics of gravity-cast engine cylinder heads. In their work, the inventors statistically analyzed the blank allowance of the seat ring bottom hole of 100 gravity-cast engine cylinder heads of the same model and found that the blank allowance of more than 95% of the workpieces was concentrated in the range of 0.3-0.8mm. Setting 0.5mm as the dividing value can ensure that the cutting load in the large allowance area is controlled within the tool's bearing range. The judgment process is automatically completed by the drilling and tapping center control system. After reading the allowance distribution data matrix, the system compares the allowance of each detection point with the 0.5mm threshold and automatically marks the boundary between the large allowance area and the normal allowance area.

[0036] Understandably, based on statistical data of the allowance distribution of gravity-cast blanks, scientific boundary thresholds are set, and the control system automatically completes the area determination, clarifying the range of large allowance areas and regular allowance areas, providing a clear basis for graded roughing path planning; clear zoning boundaries avoid inappropriate cutting parameter adaptation due to ambiguity in zoning, ensuring that low-load cutting parameters are used in large allowance areas and high-efficiency cutting parameters are used in regular allowance areas, taking into account both machining stability and efficiency.

[0037] Further, in step S3, the first set of cutting parameters is: rotational speed 4000-5000 r / min, feed rate 0.08-0.1 mm / r; the second set of cutting parameters is: rotational speed 6000-7000 r / min, feed rate 0.12-0.15 mm / r.

[0038] Specifically, the first set of cutting parameters uses a rotational speed of 4500 r / min and a feed rate of 0.09 mm / r, suitable for large blank allowances of 0.5-0.8 mm. These parameters were determined through tool cutting tests and can control the cutting force within 150-200 N, avoiding tool overload. The second set of cutting parameters uses a rotational speed of 6500 r / min and a feed rate of 0.13 mm / r, suitable for conventional blank allowances of 0.3-0.5 mm, with the cutting force controlled within 80-120 N, improving machining efficiency while ensuring tool life. The cutting parameters are preset and called up through the CNC system of the drilling and tapping center. The system model is Siemens 828D, which can realize automatic switching of cutting parameters for different areas.

[0039] Understandably, for the high-load characteristics of the large allowance area, the first set of parameters, low speed and low feed rate, is used to reduce the amount of cutting per unit time and reduce tool wear; for the low-load characteristics of the conventional allowance area, the second set of parameters, high speed and high feed rate, is used to improve machining efficiency. The parameters are automatically switched by the CNC system to ensure smooth execution of the staged machining.

[0040] Furthermore, in step S4, the coolant in the high-pressure cooling system is an emulsion, the injection pressure is 0.6-0.8 MPa, the injection flow rate is 15-20 L / min, and the coolant temperature is controlled at 20℃-30℃.

[0041] Specifically, in this embodiment, a 5% concentration water-based emulsion is selected as the emulsifier, which has good cooling, lubrication and rust prevention properties and is suitable for aluminum alloy cutting; the maximum output pressure of the high-pressure pump of the high-pressure cooling system is 1.0 MPa, the flow rate adjustment range is 10-30 L / min, and the coolant temperature is controlled by the constant temperature device of the cooling water tank; in this embodiment, the injection pressure is specifically selected as 0.7 MPa, and the injection flow rate is specifically selected as 18 L / min.

[0042] Understandably, the emulsion is sprayed evenly into the cutting area through the annular nozzle, forming a continuous cooling and lubricating film to reduce the cutting temperature. At the same time, the high-pressure jet force can wash and break the chips, and the graded cutting parameters disrupt the continuous forming conditions of aluminum chips, resulting in stable chip breaking.

[0043] Further, please refer to Figure 2 In step S4, a spiral chip removal groove 100 is provided on the tool holder of the roughing reamer 10, and the width of the spiral chip removal groove 100 is 8-10mm.

[0044] Understandably, during the cutting process, aluminum chips rise spirally along the chip removal groove 100 under the guidance of the cutting force and the spiral chip removal groove 100 and are discharged from the cutting area. Combined with the flushing effect of the high-pressure coolant, the chip removal efficiency can be further improved, and the problems of increased cutting resistance and hole wall scratches caused by the accumulation of aluminum chips in the cutting area can be avoided, thus ensuring the stability of the roughing process.

[0045] Furthermore, in step S5, the cutting parameters of the finishing reamer are: rotational speed 10000-12000 r / min, feed rate 0.05-0.08 mm / r, and the cutting edge of the finishing reamer is chamfered with a thickness of 0.02-0.03 mm.

[0046] Specifically, the finishing reamer is made of PCD (polycrystalline diamond), has 6 teeth, a shank diameter of 20mm, and a chamfer of 0.025mm with a chamfer angle of 15°. It is formed by grinding with a diamond wheel to ensure a chamfer accuracy of ±0.002mm. The cutting parameters are a spindle speed of 11000 r / min and a feed rate of 0.06 mm / r.

[0047] Understandably, high-speed, low-feed cutting parameters can reduce cutting forces and prevent workpiece deformation, while the chamfered edge design can enhance the edge strength, prevent edge chipping, reduce built-up edge formation during cutting, ensure surface quality, and facilitate precise control of the final allowance.

[0048] Furthermore, in step S1, the clamping pressure of the fixture is 0.5-0.7MPa, preferably 0.6MPa, and a rubber buffer pad is provided on the contact surface between the fixture and the engine cylinder head blank.

[0049] Specifically, a clamping pressure of 0.5-0.7MPa ensures that the engine cylinder head blank is firmly fixed, while avoiding blank deformation caused by excessive pressure; the rubber buffer pad can buffer the clamping force, reduce indentations and scratches on the blank surface, and the anti-slip texture improves clamping stability.

[0050] Furthermore, in step S6, the qualification criteria are: the allowance at each detection point of the seat ring bottom hole is ≤0.15mm, and the surface roughness Ra is ≤0.4um.

[0051] Specifically, the detection points are consistent with the scanning detection point positions in step S1 (5 axial and 5 circumferential). The remaining amounts of each point are detected by a laser detection probe, and the surface roughness is detected by a surface roughness meter, specifically the MarSurf M300C. The detection accuracy of this roughness meter is 0.001 μm. The advantage of selecting this model is its high detection accuracy and convenient operation. In actual applications, other models can also be selected for this component, and the embodiments of this application do not limit this. The detection data is transmitted to the control system of the drilling and tapping center in real time, and the system automatically compares and determines the criteria. If the remaining amount of all detection points ≤ 0.15 mm and the surface roughness Ra ≤ 0.4 μm, it is determined to be qualified; if any detection point does not meet the requirements, it is determined to be unqualified.

[0052] It can be understood that by having the same detection point layout as before rough machining, the comprehensiveness of the remaining amount detection can be ensured. The clear dual determination criteria are conducive to the quantitative control of the machining quality. The determination is automatically completed by the control system during detection, which can improve the detection efficiency and accuracy.

[0053] Further, in step S3, during the staged rough machining, the runout of the spindle of the drilling and tapping center is controlled within 0.005 mm.

[0054] Specifically, the spindle runout is detected by a dial indicator. During detection, the dial indicator is fixed on the workbench of the drilling and tapping center, and the measuring head abuts against the end face of the shank of the rough machining reamer. The spindle rotates at a low speed (100 r / min), and the difference between the maximum reading and the minimum reading of the dial indicator is recorded, which is the spindle runout; by regularly calibrating the spindle bearings (specifically, the calibration period is once a month) and optimizing the clamping accuracy of the chuck, the spindle runout is ensured to be controlled within 0.005 mm.

[0055] Specifically, through precise detection and regular calibration, the spindle runout can be controlled, ensuring that the rotation center of the rough machining reamer coincides with the axis of the seat ring bottom hole, reducing the radial vibration during the cutting process, and thus reducing the wear of the tool caused by vibration and extending the working life of the tool.

[0056] It should be noted that in this article, the term "comprising", "including" or any other variant thereof is intended to cover non-exclusive inclusion, so that a process, method, article or device including a series of elements not only includes those elements, but also includes other elements not expressly listed, or elements inherent to such process, method, article or device. Without further limitation, an element defined by the statement "including a..." does not exclude the existence of additional identical elements in the process, method, article or device including that element.

[0057] Furthermore, it should be noted that the scope of the methods and apparatus in the embodiments of this application is not limited to performing functions in the order shown or discussed, but may also include performing functions substantially simultaneously or in the reverse order, depending on the functions involved. For example, the described methods may be performed in a different order than described, and various steps may be added, omitted, or combined. In addition, features described with reference to certain examples may be combined in other examples.

[0058] The above description is merely a specific embodiment of the present invention, but the scope of protection of the present invention is not limited thereto. Any changes or substitutions that can be easily conceived by those skilled in the art within the scope of the technology disclosed in the present invention should be included within the scope of protection of the present invention.

Claims

1. A machining method for reducing seat bottom hole allowance, applied to a drilling and tapping center, for machining an engine head seat bottom hole, characterized in that, The method comprises the following steps: S1, the gravity casting engine cylinder head is fixed to the drilling and tapping center workbench through a clamp, a laser detection probe is used to scan the whole area of the bottom hole machining area of the seat ring, and blank allowance distribution data is obtained; S2, based on the blank allowance distribution data, the bottom hole machining area of the seat ring is divided into a large allowance area and a conventional allowance area, and a hierarchical rough machining path is planned; S3, a rough machining reamer is installed, the drilling and tapping center spindle drives the rough machining reamer to perform hierarchical rough machining along the planned path: for the large allowance area, machining is performed according to a first group of cutting parameters; for the conventional allowance area, machining is performed according to a second group of cutting parameters, and most of the allowance is removed; S4, the high-pressure cooling system is started synchronously during rough machining, the cooling liquid is uniformly sprayed to the cutting area along the circumference of the rough machining reamer, and aluminum chip breaking is realized in cooperation with the cutting parameters; S5, after rough machining is completed, a finishing reamer is replaced, the drilling and tapping center spindle drives the finishing reamer to perform finishing machining of the bottom hole of the seat ring, and the final allowance is controlled to be less than or equal to 0.15 mm; S6, after finishing machining is completed, the allowance and surface quality of the bottom hole of the seat ring are detected by using the laser detection probe, and if the detection is qualified, the machining is completed, and if the detection is unqualified, the rough machining path is re-planned in step S2 and machining is performed again.

2. The method for reducing the seat ring bottom hole allowance machining according to claim 1, characterized in that, In step S1, the detection accuracy of the laser detection probe is 0.003 mm, five detection points are uniformly selected along the axial direction and the circumferential direction of the bottom hole of the seat ring during scanning, and a matrix of allowance distribution data is formed.

3. The method of claim 1, wherein, In step S2, the determination criterion of the large allowance area is that the blank allowance is greater than 0.5 mm, and the determination criterion of the conventional allowance area is that the blank allowance is less than or equal to 0.5 mm.

4. The method of claim 1, wherein, In step S3, the first group of cutting parameters are: the rotating speed is 4000-5000 r / min, and the feed rate is 0.08-0.1 mm / r; the second group of cutting parameters are: the rotating speed is 6000-7000 r / min, and the feed rate is 0.12-0.15 mm / r.

5. The method of claim 1, wherein, In step S4, the cooling liquid of the high-pressure cooling system is emulsion, the spraying pressure is 0.6-0.8 MPa, the spraying flow rate is 15-20 L / min, and the temperature of the cooling liquid is controlled to be 20-30 DEG C.

6. The method of claim 1, wherein, In step S4, a spiral chip removal groove is arranged on the cutter bar of the rough machining reamer, and the width of the spiral chip removal groove is 8-10 mm.

7. The method of claim 1, wherein, In step S5, the cutting parameters of the finishing reamer are: the rotating speed is 10000-12000 r / min, and the feed rate is 0.05-0.08 mm / r, and the cutting edge of the finishing reamer is provided with a chamfer of 0.02-0.03 mm.

8. The method of claim 1, wherein, In step S1, the clamping pressure of the clamp is 0.5-0.7 MPa, and a rubber buffer pad is arranged on the fitting surface of the clamp and the engine cylinder head blank.

9. The method of claim 2, wherein, In step S6, the qualified determination criterion is that the allowance of each detection point of the bottom hole of the seat ring is less than or equal to 0.15 mm, and the surface roughness Ra is less than or equal to 0.4 um.

10. The method of claim 1, wherein, In step S3, during hierarchical rough machining, the runout of the drilling and tapping center spindle is controlled to be within 0.005 mm.

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