A motorcycle engine cylinder head machining process

Abstract

The present application relates to a kind of motorcycle engine cylinder head machining process, including with the combustion chamber plane of cylinder head and two positioning pin hole as benchmark, by and by parallel positioning tooling, cylinder head is clamped on machine tool, and establishes workpiece coordinate system;First, rough machining and semi-finishing are carried out to combustion chamber spherical surface using disc milling cutter and ball head milling cutter;Grid scanning measurement is carried out to combustion chamber spherical surface, obtains the actual coordinate data of each point of spherical surface, reconstructs spherical surface model and calculates the deviation Δ of current spherical surface depth and target depth value;According to deviation Δ, dynamically optimize finishing tool path;Finishing is carried out using ball head milling cutter according to optimized track;Whether spherical surface depth satisfies tolerance requirement is verified by measurement.The beneficial effects of the present application are that: while strictly controlling positioning and processing error by and by parallel positioning tooling, the high-precision control of combustion chamber spherical surface depth is realized by combining "measurement-compensation-processing" closed-loop control, and then the processing efficiency and processing quality are improved.

Description

Technical Field

[0001] This invention relates to the field of machining technology, specifically to a machining process for a motorcycle engine cylinder head. Background Technology

[0002] The cylinder head is one of the core components of a motorcycle engine. Its structure mainly includes intake and exhaust valve seats, oil catch ports, combustion chamber cover, spark plug threaded holes, cooling fins, rocker arm holes, and a noise reduction chamber during engine operation. The machining precision of the cylinder head combustion chamber spherical surface directly determines the engine's combustion chamber volume, thus affecting the engine's power, economy, and emissions performance. The combustion chamber spherical surface is usually a dome-shaped structure, which, together with the piston crown, forms the combustion chamber space, and its depth dimensional tolerances are subject to extremely strict requirements.

[0003] Currently, the machining of the spherical surface of the combustion chamber in motorcycle cylinder heads mainly adopts the following two methods:

[0004] (1) Form milling: Form milling with a form milling cutter with the same radius as the sphere is used. The advantage of this method is that it can form the sphere in one step and has high efficiency; the disadvantage is that the tool manufacturing cost is high and the tool is difficult to repair after wear. The machining accuracy decreases with tool wear and it is difficult to consistently meet the IT8 level accuracy requirements.

[0005] (2) CNC milling: ball end mills are used to machine on a CNC machine tool according to a predetermined trajectory. This method has good flexibility, but traditional machining processes do not consider online measurement and compensation. The machining accuracy is affected by factors such as uneven blank allowance, tool wear, and cutting thermal deformation, resulting in large fluctuations in machining quality.

[0006] Furthermore, during the machining of the cylinder head combustion chamber spherical surface and various holes, for multiple workpieces with different machining surfaces or holes, the workpieces need to be moved back and forth between different machine tools, resulting in high machine tool usage and low work efficiency. Existing tooling fixtures mostly use bolt-plate type, which cannot fully restrict the workpiece's degree of freedom, easily leading to under-positioning phenomena and large positioning and machining errors. These positioning and machining errors are affected by factors such as the size of the positioning pin hole, the installation size of the positioning element, and the mating size between the positioning element and the positioning pin hole. If these factors are not controlled, it will be difficult to meet the traditional requirement of ±0.05mm for the depth machining error of the combustion chamber spherical surface, thus affecting the machining quality. Summary of the Invention

[0007] The purpose of this invention is to overcome the shortcomings of the prior art and provide a machining process for motorcycle engine cylinder heads. By strictly controlling the positioning and machining errors through parallel positioning fixtures, and combining closed-loop control of "measurement-compensation-machining" to achieve high-precision control of the spherical depth of the combustion chamber, the machining efficiency and machining quality are improved.

[0008] The objective of this invention is achieved through the following technical solution:

[0009] A machining process for a motorcycle engine cylinder head includes the following steps:

[0010] S1. Using the combustion chamber plane and two locating pin holes of the cylinder head as a reference, the cylinder head is clamped on the machine tool using a parallel locating fixture, and a workpiece coordinate system is established.

[0011] S2. Use a disc milling cutter to rough machine the spherical surface of the combustion chamber, leaving a finishing allowance of 0.3mm~0.5mm;

[0012] S3. Use a ball end mill to perform semi-finishing on the spherical surface of the combustion chamber, leaving a finishing allowance of 0.1mm~0.15mm;

[0013] S4. Use a contact or non-contact high-precision probe to perform gridded scanning measurement on the spherical surface of the combustion chamber, obtain the actual coordinate data of each point on the spherical surface, reconstruct the spherical model based on the actual coordinate data, and calculate the deviation Δ between the current spherical surface depth and the target depth value.

[0014] S5. Based on the deviation Δ obtained in step S4, dynamically optimize the finishing tool path;

[0015] S6. Use a ball end mill to perform finishing along the optimized trajectory;

[0016] S7. After finishing, the depth of the sphere is measured to verify whether it meets the tolerance requirements. If it does not meet the requirements, repeat steps S5 and S6 for micro-compensation machining.

[0017] Furthermore, the side-by-side positioning fixture includes a worktable, positioning components, and pneumatic clamps. The worktable is fixed to the machining center of the machine tool. The top surface of the worktable has multiple rectangular positioning surfaces arranged side by side along the center line of the worktable. Positioning components are correspondingly located on the rectangular positioning surfaces on the worktable. Pneumatic clamps are located on both sides of the positioning components. The positioning components include two cylindrical positioning pins and two cylindrical support pins. The two cylindrical positioning pins are respectively located on a set of diagonals of the corresponding rectangular positioning surfaces, and the two cylindrical positioning pins are respectively located on both sides of the center line of the worktable. The two cylindrical support pins are respectively located on another set of diagonals of the corresponding rectangular positioning surfaces. Support blocks are fixedly fitted on both the cylindrical positioning pins and the cylindrical support pins. The cylinder head is supported on the support blocks. The top of the cylindrical positioning pin passes through the support block and is inserted into the positioning pin hole on the cylinder head. The two pneumatic clamps correspond to the air ports on both sides of the cylinder head. The air ports include an intake port and an exhaust port.

[0018] Furthermore, the pneumatic clamp includes a clamping table, a cylinder, and a clamping rod. The clamping table is set on the workbench, the cylinder is vertically set at the center of the clamping table, one end of the clamping rod is connected to the output end of the cylinder, and the other end of the clamping rod is inserted into the corresponding air port.

[0019] Furthermore, the distance between the center of the cylindrical locating pin and the centerline of the worktable. Satisfy the formula In the formula, The distance between the center of the locating pin hole corresponding to the cylindrical locating pin and the center line of the worktable, in mm; The limit deviation of the distance between the center of the cylindrical locating pin and the center line of the worktable and ,in This represents the limit deviation of the locating pin hole diameter, in mm.

[0020] Furthermore, the maximum limiting diameter of the cylindrical locating pin Satisfy the formula In the formula, This is the minimum limit diameter of the locating pin hole, in mm; The minimum clearance between the cylindrical locating pin and the locating pin hole. ,in denoted by , where is the diameter tolerance of the cylindrical locating pin in mm, and 'b' is a compensation coefficient obtained by consulting a mechanical design manual and considering lubrication conditions.

[0021] Furthermore, when the cylindrical locating pin is inserted into the locating pin hole, the actual positioning error of the cylinder head in the X and Y machining directions... Satisfy the formula In the formula The upper deviation of the locating pin hole diameter is expressed in mm. This represents the lower deviation of the cylindrical locating pin diameter, in mm.

[0022] Furthermore, the measurement path of the contact or non-contact high-precision probe adopts a spiral scanning method, expanding from the center of the sphere to the outer periphery during scanning, with a measurement point density of not less than 10 points / mm².

[0023] Furthermore, when optimizing the tool path, if Δ > 0, the original path is maintained; if Δ < 0, the tool path is raised as a whole according to the deviation value, and the compensation amount is |Δ|; if the local deviation exceeds the preset threshold, the tool position density in the corresponding area is increased.

[0024] Furthermore, the radius R of the ball end mill and the radius SR of the sphere satisfy the relationship R ≤ SR / 2.

[0025] Furthermore, when the blank allowance is unevenly distributed after rough machining and the obtained deviation Δ is greater than the preset threshold, the finishing process is carried out in multiple cuts, and the tool path is optimized successively based on the measurement results after the previous cut.

[0026] Compared with the prior art, the present invention has the following beneficial effects:

[0027] 1. This invention combines online measurement with dynamic compensation to achieve closed-loop control of "measurement-compensation-processing". It can control the spherical depth error of the combustion chamber within ±0.03mm, which is better than the traditional ±0.05mm requirement. This ensures the accuracy of the combustion chamber volume, and the closed-loop control eliminates random errors in the processing, ensuring good consistency of processing quality. It is suitable for mass production.

[0028] 2. The roughing process of this invention uses a large cutting amount to quickly remove excess material, and the finishing process uses an optimized trajectory to complete the process in one go, without the need for repeated trial cuts and adjustments. The overall efficiency can be improved by more than 20%, and the finishing process does not require special forming tools. It can be completed using a standard ball end mill, which can reduce tool costs by more than 50%.

[0029] 3. Based on the principle of side-by-side positioning, this invention uses multiple side-by-side positioning components, which facilitates the side-by-side processing of multiple workpieces, reduces the workpiece transfer process on different machine tools, and thus reduces the number of machine tools used. In addition, the two cylindrical positioning pins and two cylindrical support pins in the positioning components are distributed in a diagonal cross pattern, which can ensure that the six degrees of freedom of the workpiece are completely restricted during the processing, thereby avoiding the occurrence of under-positioning.

[0030] 4. By strictly designing and controlling the installation dimensions of the cylindrical locating pin and the mating dimensions between the cylindrical locating pin and the locating pin hole, this invention reduces the positioning and processing errors of the workpiece and further improves the processing quality. Attached Figure Description

[0031] Figure 1 This is a schematic diagram of the cylinder head clamping process in this invention;

[0032] Figure 2 This is a schematic diagram showing the distance between the center of the positioning pin hole and the center line of the worktable in this invention;

[0033] Figure 3 This is a schematic diagram showing the distribution of the cylindrical positioning pins and cylindrical support nails in this invention.

[0034] In the diagram: 1. Workbench; 2. Cylindrical locating pin; 3. Cylindrical support pin; 4. Support block; 5. Locating pin hole; 6. Air inlet; 7. Exhaust outlet; 8. Fixture table; 9. Cylinder; 10. Clamping rod. Detailed Implementation

[0035] The present invention will be further described below with reference to the accompanying drawings, but the scope of protection of the present invention is not limited to the following description.

[0036] Example 1

[0037] like Figure 1 As shown, a machining process for a motorcycle engine cylinder head includes the following steps S1-S7:

[0038] S1. Using the combustion chamber plane of the cylinder head and the two locating pin holes 5 as references, clamp the cylinder head onto the machine tool using a parallel locating fixture, and establish the workpiece coordinate system. When establishing the workpiece coordinate system, set the center point of the combustion chamber spherical surface as the origin of the coordinate system, and the axial direction of the spherical surface as the Z-axis direction.

[0039] S2. Use a disc milling cutter to rough machine the spherical surface of the combustion chamber, leaving a finishing allowance of 0.3mm~0.5mm. The cutting parameters for rough machining are: spindle speed 2000r / min~3000r / min, feed rate 400mm / min~600mm / min, and depth of cut 1.5mm~2.5mm.

[0040] S3. Use a ball end mill to perform semi-finishing on the spherical surface of the combustion chamber, leaving a finishing allowance of 0.1mm~0.15mm. The semi-finishing cutting parameters are: spindle speed 3000r / min~4000r / min, feed rate 300mm / min~500mm / min, and depth of cut 0.2mm~0.3mm.

[0041] S4. Use a contact or non-contact high-precision probe to perform gridded scanning measurement on the spherical surface of the combustion chamber, obtain the actual coordinate data of each point on the spherical surface, reconstruct the spherical model based on the actual coordinate data, and calculate the deviation Δ between the current spherical surface depth and the target depth value.

[0042] The contact or non-contact high-precision probe is mounted on the machine tool spindle. The measurement path of the contact or non-contact high-precision probe adopts a spiral scanning method, which expands from the center of the sphere to the outer periphery during scanning, and the measurement point density is not less than 10 points / mm².

[0043] S5. Based on the deviation Δ obtained in step S4, dynamically optimize the finishing tool path.

[0044] Specifically, when optimizing the toolpath, if Δ > 0, the original path is maintained; if Δ < 0, the toolpath is raised overall according to the deviation value, with a compensation amount of |Δ|; if the local deviation exceeds a preset threshold, the tool position density in the corresponding area is increased. Since the machining allowance at the junction of the sphere and the sidewall varies significantly, the areas where the local path is densified are mainly the junction area of ​​the sphere and the sidewall.

[0045] S6. Perform finishing using a ball end mill along the optimized trajectory. The finishing cutting parameters are: spindle speed 4000 r / min~5000 r / min, feed rate 200 mm / min~300 mm / min, depth of cut 0.05 mm~0.1 mm. Maintain adequate coolant spray during finishing. The radius R of the ball end mill and the radius SR of the sphere must satisfy the relationship R ≤ SR / 2 to ensure surface finish quality.

[0046] S7. After finishing, the depth of the sphere is measured to verify whether it meets the tolerance requirements. If it does not meet the requirements, repeat steps S5 and S6 for micro-compensation machining.

[0047] like Figure 1 As shown, the side-by-side positioning fixture includes a worktable 1, positioning components, and pneumatic clamps. The worktable 1 is fixed to the machining center of the machine tool. Multiple rectangular positioning surfaces are arranged side-by-side along the center line of the worktable 1 on its top surface. Positioning components are positioned at the corresponding rectangular positioning surfaces on the worktable 1, and pneumatic clamps are located on both sides of the positioning components. The positioning components are used for workpiece positioning. After positioning, the workpiece is clamped and fixed by the pneumatic clamps. Two pneumatic clamps correspond to the air ports on both sides of the cylinder head, including an air inlet 6 and an exhaust port 7. That is, the two pneumatic clamps clamp the air inlet 6 and exhaust port 7 of the cylinder head respectively. By positioning multiple workpieces on the same worktable 1 using multiple positioning components, multiple workpieces can be processed side-by-side, thereby reducing the number of workpieces needing to be transferred between different machine tools, reducing the number of machine tools used, and improving processing efficiency.

[0048] like Figure 1 As shown, the positioning assembly includes two cylindrical positioning pins 2 and two cylindrical support pins 3. The two cylindrical positioning pins 2 are fixed to one set of opposite corners of the corresponding rectangular positioning surface, and are located on either side of the center line of the worktable 1. The two cylindrical support pins 3 are fixed to the other set of opposite corners of the corresponding rectangular positioning surface, so that the cylindrical positioning pins 2 and cylindrical support pins 3 are distributed in a diagonal cross pattern. Support blocks 4 are integrally molded and fixed onto both the cylindrical positioning pins 2 and the cylindrical support pins 3, with the top of the cylindrical positioning pins 2 passing through the support blocks 4. During workpiece positioning, the cylinder head is placed on the worktable 1 and supported by the support blocks 4. Simultaneously, the portion of the cylindrical positioning pin 2 passing through the support blocks 4 engages with the positioning pin hole 5 on the cylinder head, thereby achieving workpiece positioning. The machine tool adopts a drilling and milling composite four-axis machine tool. The locating pin holes 5 are preferably cast holes left from the previous casting process during the machining of the cylinder head combustion chamber. Two cylindrical locating pins 2 and two cylindrical support pins 3 are distributed diagonally, allowing the workpiece to move in the X, Y, and Z directions (X...) during machining. Y Z The rotations (X̂, Ŷ, Ẑ) in the X, Y, and Z directions are completely restricted, thereby avoiding under-positioning by restricting the six degrees of freedom of the workpiece and improving positioning stability.

[0049] As one specific implementation scheme, the present invention provides two sets of positioning components, such as... Figure 2 , 3As shown, based on the casting holes left by the previous casting process of the cylinder head, the workpiece is positioned by the positioning component on the left, and then clamped by a pneumatic fixture. Then, the combustion chamber surface of the cylinder head 9 can be rough milled to machine the AB positioning pin holes 5 on the combustion chamber surface. Next, the workpiece is positioned again by the positioning component on the right and clamped by a pneumatic fixture. Then, the machine tool's Y-axis is rotated in the positive direction. Machining the rocker arm hole involves rotating in the negative direction (clockwise). The process includes environmentally friendly machining and secondary air intake surface fabrication. Apart from the spark plug process, all other processes can be successfully completed by adjusting the position and distance of the cylindrical locating pin 2.

[0050] like Figure 1 As shown, the pneumatic fixture includes a fixture platform 8, a cylinder 9, and clamping rods 10. The fixture platform 8 is fixed on the worktable 1. The cylinder 9 is vertically installed at the center of the fixture platform 8. One end of the clamping rod 10 is fixedly connected to the output end of the cylinder 9, and the other end of the clamping rod 10 is inserted into the corresponding air port. During the workpiece positioning process, the two clamping rods 10 are inserted into the air inlet 6 and exhaust port 7 on both sides of the cylinder head, respectively. Then, the cylinder 9 drives the clamping rods to press down, causing the clamping rods to press firmly against the hole wall, thereby clamping the cylinder head through the two clamping rods.

[0051] To reduce positioning and machining errors and improve machining quality, the installation dimensions of the cylindrical locating pins and the mating dimensions between the cylindrical locating pins and their holes need to be designed and controlled. Specifically, the vertical distance between the centers of the two cylindrical locating pins 2... Satisfy the formula In the formula, The distance between the center of the positioning pin hole 5 corresponding to the cylindrical positioning pin 2 and the center line of the worktable 1, in mm; The limit deviation of the distance between the center of cylindrical locating pin 2 and the center line of worktable 1 and ,in This represents the limit deviation of the diameter of the locating pin hole 5, in mm.

[0052] Maximum limit diameter of cylindrical locating pin 2 Satisfy the formula In the formula, This is the minimum limit diameter of the locating pin hole 5, in mm; The minimum clearance between the cylindrical locating pin 2 and the locating pin hole 5 and ,in denoted by 2, representing the diameter tolerance of the cylindrical locating pin 2 in mm, and b, representing the compensation coefficient obtained by consulting the mechanical design manual and considering lubrication conditions.

[0053] The maximum clearance between the cylindrical locating pin 2 and the locating pin hole 5 directly affects the workpiece's displacement in the X and Y directions, thus affecting the workpiece's symmetry and consequently the actual positioning error of the cylinder head in the X and Y machining directions. Satisfy the formula In the formula, The upper deviation of the diameter of the locating pin hole 5 is in mm; The lower deviation of the diameter of cylindrical locating pin 2 (absolute value), in mm.

[0054] like Figure 2 As shown, in one specific embodiment, the present invention leaves two [unclear] left by the previous casting process. 5.2 cast holes serve as locating pin holes. dimensional tolerances of casting holes It shall be performed in accordance with grade m of GB / T1804-2000, that is, the diameter of the locating pin hole 5 is 9mm. 0.2m, limit deviation for mm, minimum limit diameter of locating pin hole 5 =8.8mm, the distances between the centers of the two locating pin holes 5 and the center line of the worktable 1 are 29mm and 32mm respectively, so the distances between the centers of the two cylindrical locating pins 2 and the center line of the worktable 1 can be obtained. The tolerances are 29mm ± 0.05mm and 32mm ± 0.05mm respectively. The workpiece's positioning reference surface is the cast hole, and the surface accuracy of the inner circular surface of the cast hole and the support platform is... 6.3, the surface finish affects the workpiece's height direction error. The machining errors in the width and length directions are affected by the fit of the cylindrical locating pins and casting holes, as well as the workpiece's own precision. The workpiece... The hole axis is positioned such that its positioning datum coincides with the process datum. That is, when the positioning datum and the process datum do not coincide, the machining error caused by the dimensional tolerance between the positioning datum and the process datum (datum non-coincidence error) occurs. Because the reference datums coincide, the positional movement (displacement error) is caused by gaps, dimensional deviations, and shape errors between the positioning reference and the positioning elements (cylindrical positioning pins, support surfaces, etc.). The impact is negligible and can be disregarded. This leads to the maximum range of positional variation (total positioning error) of the process datum in the machining dimension direction after the workpiece is positioned. .

[0055] The diameter tolerance of cylindrical locating pin 2 is as follows: The value of the stage is taken as 0.022mm. After consulting the mechanical design manual and considering lubrication conditions, b=2.8 is selected. Then the minimum clearance between the cylindrical locating pin 2 and the locating pin hole 5 is determined. =0.014mm, the maximum limit diameter of cylindrical locating pin 2 Finally, the working diameter of the cylindrical locating pin 2 (i.e., the diameter of the part of the cylindrical locating pin 2 that is inserted into the locating pin hole 5) is obtained. Therefore, the cylindrical locating pin 2 and the locating pin hole Actual positioning error after mating .

[0056] Since positioning errors have a significant impact on machining accuracy during the machining process, corresponding measures should be taken to reduce them. Positioning error. The positioning error that may exist during actual machining is approximately [percentage missing] of the calculated value. Half of the error can be offset by clamping the workpiece. Therefore, if there is a large error in the actual machining process, the influence of the positioning error on the symmetry of the workpiece can be reduced by increasing the diameter of the cylindrical positioning pin 2, thereby reducing the machining error of the workpiece, ensuring the stability of the machining coordinates, and thus meeting the machining requirements of milling and drilling / reaming.

[0057] According to the above-mentioned motorcycle engine cylinder head processing technology, this invention takes the spherical processing of the combustion chamber of a certain model of motorcycle cylinder head as an example. The spherical radius is SR33.5mm, the depth requirement is 13.5±0.05mm, and the material is ZL111 aluminum alloy.

[0058] Using the combustion chamber plane and two φ9 locating pin holes 5 as references, the cylinder head is clamped onto the machining center of a four-axis drilling and milling machine using a parallel positioning assembly. A workpiece coordinate system is established, with the center of the sphere as the origin and the spherical axis as the Z-axis.

[0059] Roughing was performed using an 80mm diameter disc milling cutter with 4 teeth, a spindle speed of N=2500r / min, a feed rate of F=500mm / min, and a depth of cut ap=2.0mm. After roughing, the spherical depth was measured to be approximately 14.2mm, leaving a allowance of 0.3mm.

[0060] The semi-finishing process used a 16mm diameter ball end mill, with a spindle speed of N=3500r / min, a feed rate of F=400mm / min, and a depth of cut ap=0.25mm. After semi-finishing, the spherical depth was measured to be approximately 13.65mm, leaving a allowance of 0.15mm.

[0061] Before finishing, a Renishaw OMP60 probe was used to measure the spherical surface using a helical scanning method. The scanning radius ranged from 0 to 33.5 mm, the pitch was 1 mm, and the measurement point density was approximately 12 points / mm². After processing the measurement data, the average depth of the current spherical surface was found to be 13.62 mm, which deviated from the target depth of 13.5 mm by Δ = 0.12 mm, indicating that the allowance was too large.

[0062] Based on the deviation value Δ=0.12mm, the finishing tool path was shifted by 0.12mm in the negative Z-axis direction. Simultaneously, the measurement data of the area where the sphere meets the sidewall were examined, revealing uneven allowance distribution in this area, with a maximum local deviation of 0.18mm. The tool path in this area was then refined, with the tool position spacing reduced from 0.5mm to 0.2mm.

[0063] Finishing was performed using a 12mm diameter ball end mill, with a spindle speed of N=4500r / min, a feed rate of F=250mm / min, and a depth of cut ap=0.08mm, following an optimized trajectory. Emulsion was used for thorough cooling during the machining process.

[0064] After finishing, the spherical surface was scanned and measured again using a probe. The average depth of the spherical surface was measured to be 13.485 mm, with a deviation Δ = 0.015 mm, meeting the tolerance requirement of ±0.05 mm. Subsequent combustion chamber volume testing showed an average volume of 14.50 mL, achieving a 100% pass rate.

[0065] Example 2

[0066] Based on Example 1, this embodiment further optimizes the finishing process to address the issue of uneven blank allowance distribution and deviation Δ exceeding a preset threshold after rough machining. Specifically, the finishing process is divided into multiple passes, and the tool path is optimized sequentially based on the measurement results after the previous pass.

[0067] During the specific machining process, after rough machining, inspection revealed that the allowance on one side of the spherical surface was 0.4mm, while the allowance on the other side was only 0.2mm, with a maximum deviation of 0.2mm. Based on the measurement results from step S4, the average depth of the spherical surface was 13.70mm, but the depth in some local areas reached 13.82mm. When optimizing the toolpath, in addition to the overall offset, a layered compensation strategy was adopted for areas with large allowances. Specifically, the finishing process was divided into two passes: the first pass had a cutting depth of 0.12mm, and the second pass had a cutting depth of 0.05mm. The toolpath was further optimized based on the measurement results after the first pass. The optimized final machining result was a spherical surface depth of 13.48mm~13.53mm, with a maximum deviation of 0.025mm, which met the requirements.

[0068] Based on the above-mentioned motorcycle engine cylinder head processing technology, this invention strictly controls positioning and processing errors through parallel positioning fixtures, while combining online measurement and dynamic compensation to achieve closed-loop control of "measurement-compensation-processing". This can control the combustion chamber spherical depth error within ±0.03mm, which is better than the traditional ±0.05mm requirement, ensuring the accuracy of combustion chamber volume. Moreover, the closed-loop control eliminates random errors in the processing, ensuring good consistency of processing quality, and is suitable for mass production.

[0069] Although embodiments of the invention have been shown and described, it will be understood by those skilled in the art that various changes, modifications, substitutions and alterations can be made to these embodiments without departing from the principles and spirit of the invention, the scope of which is defined by the appended claims and their equivalents.

Claims

1. A machining process for a motorcycle engine cylinder head, characterized in that, Includes the following steps: S1. Using the combustion chamber plane of the cylinder head and the two locating pin holes (5) as a reference, the cylinder head is clamped on the machine tool by parallel locating fixtures, and the workpiece coordinate system is established. S2. Use a disc milling cutter to rough machine the spherical surface of the combustion chamber, leaving a finishing allowance of 0.3mm~0.5mm; S3. Use a ball end mill to perform semi-finishing on the spherical surface of the combustion chamber, leaving a finishing allowance of 0.1mm~0.15mm; S4. Use a contact or non-contact high-precision probe to perform gridded scanning measurement on the spherical surface of the combustion chamber, obtain the actual coordinate data of each point on the spherical surface, reconstruct the spherical surface model based on the actual coordinate data, and calculate the deviation Δ between the current spherical surface depth and the target depth value. S5. Based on the deviation Δ obtained in step S4, dynamically optimize the finishing tool path; S6. Use a ball end mill to perform finishing along the optimized trajectory; S7. After finishing, the depth of the sphere is measured to verify whether it meets the tolerance requirements. If it does not meet the requirements, repeat steps S5 and S6 for micro-compensation machining.

2. The motorcycle engine cylinder head processing technology according to claim 1, characterized in that: The parallel positioning fixture includes a worktable (1), positioning components, and pneumatic clamps. The worktable (1) is fixed to the machining center of the machine tool. The top surface of the worktable (1) has multiple rectangular positioning surfaces arranged in parallel along the center line of the worktable (1). Positioning components are correspondingly provided on the worktable (1) at the rectangular positioning surfaces. Pneumatic clamps are provided on both sides of the positioning components. The positioning components include two cylindrical positioning pins (2) and two cylindrical support pins (3). The two cylindrical positioning pins (2) are respectively located on a set of opposite corners of the corresponding rectangular positioning surfaces, and the two cylindrical support pins (3) are positioned on the opposite corners of the rectangular positioning surfaces. The column positioning pins (2) are located on both sides of the center line of the workbench (1). Two cylindrical support pins (3) are respectively located on the other set of opposite corners of the corresponding rectangular positioning surface. Support blocks (4) are fixedly sleeved on both the cylindrical positioning pins (2) and the cylindrical support pins (3). The cylinder head is supported on the support blocks (4). The top of the cylindrical positioning pins (2) passes through the support blocks (4) and is inserted into the positioning pin holes (5) on the cylinder head. Two pneumatic clamps correspond to the air ports on both sides of the cylinder head. The air ports include the air inlet (6) and the exhaust port (7).

3. The motorcycle engine cylinder head processing technology according to claim 2, characterized in that: The pneumatic clamp includes a clamping table (8), a cylinder (9), and a clamping rod (10). The clamping table (8) is set on the workbench (1), the cylinder (9) is set vertically at the center of the clamping table (8), one end of the clamping rod (10) is connected to the output end of the cylinder (9), and the other end of the clamping rod (10) is inserted into the corresponding air port.

4. The motorcycle engine cylinder head processing technology according to claim 3, characterized in that: The distance between the center of the cylindrical locating pin (2) and the centerline of the worktable (1) Satisfy the formula In the formula, The distance between the center of the positioning pin hole (5) corresponding to the cylindrical positioning pin (2) and the center line of the worktable (1), in mm; The limit deviation of the distance between the center of the cylindrical locating pin (2) and the center line of the worktable (1) is... ,in The limit deviation of the diameter of the positioning pin hole (5) is in mm.

5. The motorcycle engine cylinder head processing technology according to claim 4, characterized in that: Maximum limit diameter of cylindrical locating pin (2) Satisfy the formula In the formula, The minimum limit diameter of the locating pin hole (5) is in mm; The minimum clearance between the cylindrical locating pin (2) and the locating pin hole (5) and ,in denoted as the diameter tolerance of the cylindrical locating pin (2), in mm, and b is the compensation coefficient obtained by consulting the mechanical design manual and considering lubrication conditions.

6. The machining fixture for a motorcycle engine cylinder head according to claim 5, characterized in that: When the cylindrical locating pin (2) is inserted into the locating pin hole (5), the actual positioning error of the cylinder head in the X and Y machining directions is as follows: Satisfy the formula In the formula The upper deviation of the diameter of the locating pin hole (5) is in mm; The lower deviation of the diameter of the cylindrical locating pin (2) is in mm.

7. The motorcycle engine cylinder head processing technology according to claim 1, characterized in that: The measurement path of the contact or non-contact high-precision probe adopts a spiral scanning method, which expands from the center of the sphere to the outer periphery during scanning, and the measurement point density is not less than 10 points / mm².

8. The machining process for a motorcycle engine cylinder head according to claim 1, characterized in that: When optimizing the tool path, if Δ > 0, the original path is maintained; if Δ < 0, the tool path is raised as a whole according to the deviation value, and the compensation amount is |Δ|; if the local deviation exceeds the preset threshold, the tool position density in the corresponding area is increased.

9. The machining process for a motorcycle engine cylinder head according to claim 1, characterized in that: The radius R of the ball end mill and the radius SR of the sphere satisfy the relationship R ≤ SR / 2.

10. The machining process for a motorcycle engine cylinder head according to claim 1, characterized in that: When the blank allowance is unevenly distributed after rough machining and the obtained deviation Δ is greater than the preset threshold, the finishing process is carried out in multiple cuts, and the tool path is optimized step by step based on the measurement results after the previous cut.

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