A precision grinding method for multi-start lead screws with a large aspect ratio

Abstract

The present invention discloses a method for precision grinding of a multi-start lead screw with an ultra-large aspect ratio, specifically comprising the following steps: constant temperature treatment, cleaning parts, precision self-inspection, rough grinding marking, rough grinding and shaping, cleaning parts, residual self-inspection, preliminary fine grinding, cleaning parts, multiple fine grindings, final precision inspection, and thread polishing. Rough grinding and fine grinding tools are specifically designed, and rough grinding abrasives, fine grinding abrasives, and polishing agents of different components are formulated. Precision grinding of the multi-start lead screw with an ultra-large aspect ratio is achieved, the tooth profile of the multi-start lead screw with an ultra-large aspect ratio is corrected, the thread engagement and load-bearing state are improved, the surface quality of the thread bearing surface is enhanced, and the lead error in the thread transition area is corrected. This effectively ensures that the tooth surface profile tolerance grade of the multi-start lead screw with an ultra-large aspect ratio is above IT1, the nominal diameter and tooth top circle runout tolerance grade is above IT2, and the tooth surface finish requirement is less than Rz0.2.

Description

Technical Field

[0001] The invention belongs to the technical field of precision machinery manufacturing, and in particular relates to a precision grinding method for a multi-start lead screw with an ultra-large aspect ratio. Background Art

[0002] As the main transmission component, multi-start lead screws with a large aspect ratio are widely used in heavy machinery with high load requirements. Due to the large dimensions of such parts, with a length of about 4.8m, they can usually only be processed using large special machine tools. However, when using large lathes that are several meters long to process the multi-start lead screw thread features of such parts, since the part material is nickel-based high-temperature alloy GH4169, which has high hardness and is prone to work hardening, the tool wear is severe, and the part has a very large aspect ratio and insufficient rigidity. As a result, the multi-start lead screw threads after turning still have processing defects such as large ovality, many burrs, large shape and dimensional errors, and low tooth surface profile accuracy to varying degrees, making it difficult to meet the use requirements. Therefore, after fine processing on a special lathe, the multi-start lead screw threads must be deburred, reshaped, and polished with the help of precision grinding technology to ensure the shape and dimensional tolerances, tooth surface profile accuracy and other technical indicators of the multi-start lead screw with a large aspect ratio. After extensive research, it was found that there is little public reference material available for technical solutions for the precision machining of this type of ultra-large aspect ratio multi-start lead screws. Summary of the Invention

[0003] The technical problem to be solved by the present invention is to provide a precision grinding method for super-large aspect ratio multi-start screw parts, so as to trim the tooth shape of the super-large aspect ratio multi-start screw parts, improve the meshing and load-bearing state of the super-large aspect ratio multi-start screw thread, improve the surface quality of the super-large aspect ratio multi-start screw thread bearing surface and correct the lead error of the super-large aspect ratio multi-start screw thread transition area.

[0004] To achieve the above object, the present invention proposes a method for precision grinding of a multi-start lead screw with a large aspect ratio, which specifically comprises the following steps:

[0005] S1 Constant temperature treatment: Place the ultra-large aspect ratio multi-start lead screw in the processing environment for constant temperature treatment for more than 3 hours to ensure that the processing environment temperature is stable within the range of 20℃±2℃;

[0006] S2 cleaning parts: first, the super-large aspect ratio multi-start screw part is hoisted and clamped on a special grinding table, and then the super-large aspect ratio multi-start screw thread is thoroughly cleaned with detergent or anhydrous ethanol and non-woven silk cloth to remove surface impurities;

[0007] S3 precision self-inspection: Lever micrometers are set up at both ends of the super-large aspect ratio multi-start screw part, and the reference outer circle of the super-large aspect ratio multi-start screw part is aligned within 0.005mm. The threads of the super-large aspect ratio multi-start screw are precision turned, and grinding allowances are evenly reserved at all locations on the super-large aspect ratio multi-start screw thread profile surface. Then, the super-large aspect ratio screw thread is inspected with special inspection equipment to determine the size and shape error, profile and surface allowance of the super-large aspect ratio screw thread;

[0008] S4 Rough Grinding Mark: The rough grinding tool is used in combination with the prepared rough grinding abrasive to preliminarily grind the ultra-large aspect ratio multi-start screw thread. Based on the color distribution of the rough grinding tool and the surface of the ultra-large aspect ratio multi-start screw thread, the contact between the tool thread and the ultra-large aspect ratio multi-start screw thread is preliminarily determined, and then the distribution of the high and low points of the ellipse of the ultra-large aspect ratio multi-start screw thread is determined, and compared with the test results after precision turning;

[0009] S5 rough grinding and repair type: according to the mark made in step S4, the rough grinding abrasive is evenly applied to the surface of the super-large aspect ratio screw thread, and the high point of the super-large aspect ratio screw thread is focused on grinding with a rough grinding tool. The grinding pressure and residence time are appropriately increased at the high point of the super-large aspect ratio screw thread, and the low point of the super-large aspect ratio screw thread is lightly passed over to remove burrs; the rough grinding is repeated several times, and the color distribution of the surface of the super-large aspect ratio screw thread is observed until the super-large aspect ratio screw thread and the contour surface of the screw thread of the rough grinding tool can be fully fitted; during the rough grinding process, multiple sets of rough grinding tools must be prepared, and the rough grinding tools must be replaced every 20 minutes to 30 minutes to ensure uniform wear of the rough grinding tools and avoid large tooth profile errors of the super-large aspect ratio screw thread due to excessive wear of the rough grinding tools; during the rough grinding process, the grinding linear speed is controlled within the range of 40 to 45 m / min;

[0010] S6 cleaning parts: use detergent or anhydrous ethanol and non-woven silk cloth to thoroughly clean the threads of the large aspect ratio multi-start screw to remove abrasives and chips;

[0011] S7 allowance self-test: Use special testing equipment to test the super-large aspect ratio screw thread to determine the grinding allowance, size, form and position error, tooth surface profile, etc. of the super-large aspect ratio screw thread. The grinding allowance of the super-large aspect ratio screw thread is required to be 0.01-0.02mm, and the size, form and position error, and tooth surface profile must meet more than 75% of the final technical requirements.

[0012] S8 Preliminary Lapping: Evenly apply the prepared lapping agent to the surface of the super-large aspect ratio lead screw thread, and use a lapping tool to perform preliminary lapping on the entire super-large aspect ratio lead screw thread; according to the resistance of the lapping tool at different positions of the super-large aspect ratio lead screw thread, determine the positions of the super-large aspect ratio lead screw thread with large shape and dimensional errors, and focus on lapping the positions with large grinding resistance by increasing the grinding pressure and dwell time until the resistance is uniform and smooth; before the preliminary lapping, add a copper sheet to the rectangular adjustment groove of the lapping tool, and properly tighten the adjustment screw of the lapping tool to adapt to the grinding allowance at various positions of the tooth surface profile of the super-large aspect ratio lead screw thread;

[0013] S9 cleaning parts: Use detergent or anhydrous ethanol and non-woven silk cloth to thoroughly clean the threads of the large aspect ratio multi-start screw to remove abrasives and chips;

[0014] S10 multiple lapping: evenly apply the prepared lapping agent to the surface of the super-large aspect ratio lead screw thread, and again use the lapping tool to perform multiple final precision lapping on the super-large aspect ratio lead screw thread throughout the entire process; remove the copper scale, and appropriately adjust the adjustment screws of the lapping tool according to the resistance during the precision lapping process, and gradually tighten the lapping tool to adapt to the change in the size of the super-large aspect ratio multi-start lead screw thread during the precision lapping process; during the precision lapping process, control the grinding line speed within the range of 30 to 35 m / min; during the precision lapping process, multiple sets of lapping tooling must be prepared, and the lapping tooling must be replaced after each precision lapping is completed, so as to ensure uniform wear of the lapping tooling and avoid large processing errors of the super-large aspect ratio lead screw thread due to excessive wear of the lapping tooling;

[0015] S11 final precision inspection: the threads of the super-large aspect ratio multi-start lead screw are thoroughly cleaned, and a special inspection device is used to conduct a final precision inspection on the threads of the super-large aspect ratio lead screw to determine whether the various technical indicators of the super-large aspect ratio lead screw, such as the size and shape tolerance, profile, circular runout, pitch and surface quality, meet the requirements of the drawing; if so, proceed to step S12; otherwise, repeat steps S9 and S10;

[0016] S12 thread polishing: Use a silk cloth tape soaked in a modulated polishing agent to polish the super-large aspect ratio multi-start screw thread multiple times throughout the entire process until the finish of all tooth surfaces of the super-large aspect ratio multi-start screw thread meets the requirements of the drawing; the silk cloth tape soaked in the modulated polishing agent must be continuously replaced during the polishing process, and the operator must wear anti-toxic protective gear and protective gloves.

[0017] Furthermore, a final precision turning is performed before precision grinding. During turning, a grinding allowance of 0.05 to 0.07 mm must be evenly reserved at various locations on the thread profile surface of the ultra-large aspect ratio multi-start lead screw according to the drawing requirements.

[0018] Furthermore, the rough grinding tooling in the S4 rough grinding mark and the S5 rough grinding repair type is made of gray cast iron, has a half-moon shape of 1 / 3 circle, an axial length of 300mm, a radial thickness of 20mm, and an inner diameter processed into a 1:1 multi-start screw thread structure according to the design parameters of the ultra-large aspect ratio multi-start screw. The tooth profile accuracy of the rough grinding tooling inner diameter multi-start screw thread should be the same as the design accuracy of the ultra-large aspect ratio multi-start screw thread. The bottom diameter position of the rough grinding tooling inner diameter multi-start screw thread is opened with a depth of about 0.1mm. The chip groove is used to accommodate grinding chips and excess abrasives; the sharp edges of the inner diameter multi-start screw thread of the rough grinding tool are chamfered to prevent scratches on the screw thread surface; the rough grinding tool is mainly used to preliminarily correct the shape error of the multi-start screw thread and remove burrs distributed on the thread. Since the ultra-large aspect ratio screw still has ovality errors to varying degrees after precision turning, in order to prevent the rough grinding tool and the ultra-large aspect ratio screw from locking during the grinding process and scratching the thread surface, the rough grinding tool is specially designed to be half-moon shaped.

[0019] Furthermore, the rough grinding abrasive in the S4 rough grinding mark and the S5 rough grinding repair type is blended with white corundum (WA), kerosene, and paraffin oil in a mass ratio of 2:17:1; the particle size of the white corundum (WA) is 10 μm; since a lot of heat is easily generated during the rough grinding process, the mass proportion of kerosene in the rough grinding abrasive is relatively high, and part of the heat is taken away by the volatilization of the kerosene, thereby reducing the influence of the heat generated during the rough grinding process on the processing accuracy of the ultra-large aspect ratio screw.

[0020] Furthermore, the grinding tooling in the S8 preliminary grinding and the S10 multiple grinding consists of an adjusting screw, a spring washer, an adjusting flat washer and a cast iron grinding sleeve; the adjusting screw, spring washer and adjusting flat washer are all standard parts; the cast iron grinding sleeve is made of gray cast iron, has a round shape, an axial length of 300mm, a radial thickness of 20mm, and an inner diameter processed into a 1:1 multi-start screw thread structure according to the design parameters of the super-large aspect ratio multi-start screw thread. The tooth profile accuracy of the multi-start screw thread of the inner diameter of the grinding tooling should be higher than the design accuracy of the multi-start screw thread of the super-large aspect ratio. The bottom diameter position of the multi-start screw thread of the inner diameter of the grinding tooling is provided with a chip groove with a depth of about 0.05mm for accommodating grinding chips and excess abrasive; the outer diameter of the grinding tooling There is a rectangular adjustment groove with a width of 2.5mm and five evenly distributed circular process grooves with a width of 0.8mm on the circumference. One side of the rectangular adjustment groove is a light hole and the other side is a threaded hole. The adjustment screw is inserted from the light hole side and cooperates with the threaded hole on the other side through a spring washer and an adjustment flat washer; the rectangular adjustment groove is used to adjust the tightness of the fine-grinding tooling, and the five evenly distributed circular process grooves with a width of 0.8mm are used to ensure that when the fine-grinding tooling is adjusted, the fine-grinding tooling as a whole undergoes uniform elastic deformation, thereby avoiding large ovality of the inner diameter multi-start screw thread of the fine-grinding tooling; the fine-grinding tooling is mainly used to further improve the shape, size and precision of the super-large aspect ratio screw thread, and improve the profile and surface quality of the load-bearing contact surface of the super-large aspect ratio screw thread.

[0021] Furthermore, the lapping abrasives in the S8 preliminary lapping and the S10 multiple lapping are blended with white corundum (WA), kerosene, paraffin oil and lard in a mass ratio of 1:6:2:1; the particle size of the white corundum (WA) is 5 μm; since the main purpose of the lapping process is to improve the shape and dimensional accuracy of the ultra-large aspect ratio lead screw thread, and to improve the profile and surface quality of the load-bearing contact surface of the ultra-large aspect ratio lead screw thread, paraffin oil and lard are added to increase the lubricating properties of the lapping abrasive. In addition, since the precision lapping speed is relatively low, the amount of material removed in a single precision lapping is relatively small, the friction force is also greatly reduced accordingly, and the heat generated during the lapping process is also relatively small, so the mass proportion of kerosene is appropriately reduced.

[0022] Furthermore, the modulated polishing agent in the S12 thread polishing is prepared by blending chromium trioxide and oleic acid in a mass ratio of 1:1. Since chromium trioxide has certain toxicity, the operator must wear anti-toxic protective gear when polishing the ultra-large aspect ratio multi-start screw thread.

[0023] The present invention has the following beneficial effects: the present invention provides a precision grinding process method and special tooling design for ultra-large aspect ratio multi-start lead screw parts, which corrects the ovality of the ultra-large aspect ratio lead screw thread through the rough grinding process, improves the dimensional accuracy and tooth surface profile of the ultra-large aspect ratio lead screw thread through the fine grinding process, and improves the tooth surface finish of the ultra-large aspect ratio lead screw thread through the polishing process. In combination with the processing characteristics of the rough grinding process, fine grinding process and polishing process, the corresponding rough grinding tooling and fine grinding tooling are designed in a targeted manner, and rough grinding abrasives, fine grinding abrasives and polishing agents of different components are prepared, thereby achieving the ultra-large aspect ratio multi-start lead screw part. The precision grinding of screw parts corrects the tooth profile accuracy of the super-large aspect ratio screw thread, improves the meshing and load-bearing state of the super-large aspect ratio screw thread, improves the surface quality of the load-bearing surface of the super-large aspect ratio screw thread, and corrects the lead error in the transition area of ​​the super-large aspect ratio multi-start screw thread, effectively ensuring that the tooth surface profile of the super-large aspect ratio screw thread is less than 0.003mm, its tolerance grade is higher than IT1, the nominal diameter and tooth top circle runout is less than 0.006mm / 300mm, the tolerance grade is higher than IT2, and the tooth surface finish requirement is less than Rz0.2, which meets the final accuracy requirements of the drawing. BRIEF DESCRIPTION OF THE DRAWINGS

[0024] Figure 1 This is a flow chart of a method for precision grinding a multi-start lead screw with an ultra-large aspect ratio according to the present invention;

[0025] Figure 2 This is a schematic diagram of the rough grinding tool structure of the present invention;

[0026] Figure 3 It is a schematic diagram of the lapping tooling structure of the present invention.

[0027] The numbers in the figure represent: 1-1 inner diameter multi-start screw thread of rough grinding tool, 1-2 chip groove of rough grinding tool, 2-1 adjustment screw, 2-2 spring washer, 2-3 adjustment flat washer, 2-4 cast iron grinding sleeve, 2-5 inner diameter multi-start screw thread of fine grinding tool, 2-6 chip groove of fine grinding tool, 2-7 rectangular adjustment groove, 2-8 circular process groove. DETAILED DESCRIPTION

[0028] The specific embodiments of the present invention are described below with reference to the accompanying drawings.

[0029] Take the precision grinding process of a nickel-based high-temperature alloy multi-start screw part with a large aspect ratio as an example. Figure 1As shown, it is described as a specific embodiment of the present invention. The outer dimensions of the nickel-based high-temperature alloy ultra-large aspect ratio multi-start screw part are Φ152mm×4876mm, and the aspect ratio is greater than 30; the number of thread heads of the nickel-based high-temperature alloy ultra-large aspect ratio multi-start screw is 7, the lead is 35mm, the tooth shape is triangular, the tooth angle is 90°, the tooth surface hardness is 40~43HRC, the tooth surface profile requirement is less than 0.003mm, the tooth surface runout is less than 0.004mm, the normal thread pitch tolerance is less than 0.002mm, and the tooth surface roughness is less than Rz0.2. The precision grinding method proposed by the present invention for the nickel-based high-temperature alloy ultra-large aspect ratio multi-start screw part includes the following steps:

[0030] S1 Constant temperature treatment: Place the ultra-large aspect ratio multi-start lead screw in the processing environment for constant temperature treatment for more than 3 hours to ensure that the processing environment temperature is stable within the range of 20℃±2℃;

[0031] S2 cleaning parts: first, the super-large aspect ratio multi-start screw part is hoisted and clamped on a special grinding table, and then the super-large aspect ratio multi-start screw thread is thoroughly cleaned with detergent or anhydrous ethanol and non-woven silk cloth to remove surface impurities;

[0032] S3 precision self-inspection: Lever micrometers are set up at both ends of the super-large aspect ratio multi-start screw part, and the reference outer circle of the super-large aspect ratio multi-start screw part is aligned within 0.005mm. The threads of the super-large aspect ratio multi-start screw are precision turned, and grinding allowances are evenly reserved at all locations on the super-large aspect ratio multi-start screw thread profile surface. Then, the super-large aspect ratio screw thread is inspected with special inspection equipment to determine the size and shape error, profile and surface allowance of the super-large aspect ratio screw thread;

[0033] S4 Rough Grinding Mark: The rough grinding tool is used in combination with the prepared rough grinding abrasive to preliminarily grind the ultra-large aspect ratio multi-start screw thread. Based on the color distribution of the rough grinding tool and the surface of the ultra-large aspect ratio multi-start screw thread, the contact between the tool thread and the ultra-large aspect ratio multi-start screw thread is preliminarily determined, and then the distribution of the high and low points of the ellipse of the ultra-large aspect ratio multi-start screw thread is determined, and compared with the test results after precision turning;

[0034] S5 rough grinding and repair type: according to the mark made in step S4, the rough grinding abrasive is evenly applied to the surface of the super-large aspect ratio screw thread, and the high point of the super-large aspect ratio screw thread is focused on grinding with a rough grinding tool. The grinding pressure and residence time are appropriately increased at the high point of the super-large aspect ratio screw thread, and the low point of the super-large aspect ratio screw thread is lightly passed over to remove burrs; the rough grinding is repeated several times, and the color distribution of the surface of the super-large aspect ratio screw thread is observed until the super-large aspect ratio screw thread and the contour surface of the screw thread of the rough grinding tool can be fully fitted; during the rough grinding process, multiple sets of rough grinding tools must be prepared, and the rough grinding tools must be replaced every 20 minutes to 30 minutes to ensure uniform wear of the rough grinding tools and avoid large tooth profile errors of the super-large aspect ratio screw thread due to excessive wear of the rough grinding tools; during the rough grinding process, the grinding linear speed is controlled within the range of 40 to 45 m / min;

[0035] S6 cleaning parts: use detergent or anhydrous ethanol and non-woven silk cloth to thoroughly clean the threads of the large aspect ratio multi-start screw to remove abrasives and chips;

[0036] S7 allowance self-test: Use special testing equipment to test the super-large aspect ratio screw thread to determine the grinding allowance, size, form and position error, tooth surface profile, etc. of the super-large aspect ratio screw thread. The grinding allowance of the super-large aspect ratio screw thread is required to be 0.01-0.02mm, and the size, form and position error, and tooth surface profile must meet more than 75% of the final technical requirements.

[0037] S8 preliminary lapping: evenly apply the prepared lapping abrasive to the surface of the super-large aspect ratio lead screw thread, and use a lapping tool to perform preliminary lapping on the entire super-large aspect ratio lead screw thread; according to the resistance of the lapping tool at different positions of the super-large aspect ratio lead screw thread, determine the positions of the super-large aspect ratio lead screw thread with larger shape and dimensional errors, and focus on lapping the positions with larger lapping resistance by increasing the lapping pressure and dwell time until the resistance is uniform and smooth; before the preliminary lapping, add a copper sheet to the rectangular adjustment slot 2-7 of the lapping tool, and properly tighten the adjustment screw 2-1 of the lapping tool to adapt to the lapping allowance at various positions of the tooth surface profile of the super-large aspect ratio lead screw thread;

[0038] S9 cleaning parts: use detergent or anhydrous ethanol and non-woven silk cloth to thoroughly clean the threads of the large aspect ratio multi-start screw to remove abrasives and chips;

[0039] S10 multiple lapping: evenly apply the prepared lapping agent to the surface of the super-large aspect ratio lead screw thread, and again use the lapping tool to perform multiple final precision lapping on the super-large aspect ratio lead screw thread throughout the entire process; remove the copper scale, and appropriately adjust the adjustment screw 2-1 of the lapping tool according to the resistance during the precision lapping process, and gradually tighten the lapping tool to adapt to the change in the size of the super-large aspect ratio multi-start lead screw thread during the precision lapping process; during the precision lapping process, control the grinding line speed within the range of 30 to 35 m / min; during the precision lapping process, multiple sets of lapping tooling must be prepared, and the lapping tooling must be replaced after each precision lapping is completed, so as to ensure uniform wear of the lapping tooling and avoid large processing errors of the super-large aspect ratio lead screw thread due to excessive wear of the lapping tooling;

[0040] S11 final precision inspection: the threads of the super-large aspect ratio multi-start lead screw are thoroughly cleaned, and a special inspection device is used to conduct a final precision inspection on the threads of the super-large aspect ratio lead screw to determine whether the various technical indicators of the super-large aspect ratio lead screw, such as the size and shape tolerance, profile, circular runout, pitch and surface quality, meet the requirements of the drawing; if so, proceed to step S12; otherwise, repeat steps S9 and S10;

[0041] S12 thread polishing: Use a silk cloth tape soaked in a modulated polishing agent to polish the super-large aspect ratio multi-start screw thread multiple times throughout the entire process until the finish of all tooth surfaces of the super-large aspect ratio multi-start screw thread meets the requirements of the drawing; the silk cloth tape soaked in the modulated polishing agent must be continuously replaced during the polishing process, and the operator must wear anti-toxic protective gear and protective gloves.

[0042] Preferably, the ultra-large aspect ratio multi-start screw thread in the S1 constant temperature treatment, S2 parts cleaning, S3 precision self-inspection, and S4 rough grinding marks must reserve a grinding allowance of 0.05 to 0.07 mm uniformly on the contour surface of the ultra-large aspect ratio multi-start screw thread in the last precision turning before precision grinding according to the drawing requirements.

[0043] Preferably, the rough grinding tooling in the S4 rough grinding mark and the S5 rough grinding repair type is as follows: Figure 2As shown, it is mainly used to preliminarily correct the shape error of the screw thread and remove the burrs distributed on the thread; since the nickel-based high-temperature alloy ultra-large aspect ratio multi-start screw still has ovality errors to varying degrees after precision turning, in order to prevent the rough grinding tooling from locking with the nickel-based high-temperature alloy ultra-large aspect ratio multi-start screw during the grinding process and scratching the thread surface, the rough grinding tooling is specially designed to be half-moon shaped. The material of the rough grinding tool is gray cast iron, and its shape is a half-moon of 1 / 3 circle, with an axial length of 300mm and a radial thickness of 20mm. The inner diameter is processed into a 1:1 multi-start screw thread structure 1-1 according to the design parameters of the super-large aspect ratio multi-start screw. The tooth profile accuracy of the inner diameter multi-start screw thread of the rough grinding tool should be the same as the design accuracy of the super-large aspect ratio multi-start screw thread. The bottom diameter position of the inner diameter multi-start screw thread of the rough grinding tool is provided with a rough grinding tool chip groove 1-2 with a depth of about 0.1mm to accommodate grinding chips and excess abrasives; the sharp edges of the inner diameter multi-start screw thread of the rough grinding tool are chamfered to prevent scratches on the screw thread surface.

[0044] Preferably, the rough grinding abrasive in the S4 rough grinding mark and the S5 rough grinding repair type is blended with white corundum (WA), kerosene and paraffin oil in a mass ratio of 2:17:1; the particle size of the white corundum (WA) is 10 μm; since a lot of heat is easily generated during the rough grinding process, the mass proportion of kerosene in the rough grinding abrasive is relatively high, and part of the heat is taken away by the volatilization of the kerosene, thereby reducing the influence of the heat generated during the rough grinding process on the processing accuracy of the ultra-large aspect ratio screw.

[0045] Preferably, the grinding tooling in the preliminary grinding in S8 and the multiple grinding in S10 is as follows: Figure 3As shown, it is mainly used to further improve the shape and dimensional accuracy of the multi-start lead screw thread of a certain nickel-based high-temperature alloy with a large aspect ratio, and improve the contour and surface quality of the load-bearing contact surface of the multi-start lead screw thread of a certain nickel-based high-temperature alloy with a large aspect ratio; the fine grinding tool consists of an adjusting screw 2-1, a spring washer 2-2, an adjusting flat washer 2-3 and a cast iron grinding sleeve 2-4; the adjusting screw 2-1, the spring washer 2-2 and the adjusting flat washer 2-3 are all standard parts; the material of the cast iron grinding sleeve 2-4 is gray cast iron, the shape is round, the axial length is 300mm, the radial thickness is 20mm, and the inner diameter is processed into a 1:1 multi-start lead screw thread structure 2-5 according to the design parameters of the multi-start lead screw of a certain nickel-based high-temperature alloy with a large aspect ratio. The tooth profile accuracy of the inner diameter multi-start lead screw thread 2-5 of the fine grinding tool should be higher than that of the multi-start lead screw thread of a certain nickel-based high-temperature alloy with a large aspect ratio. The design accuracy of the multi-start screw is better than the diameter ratio. The bottom diameter position of the inner diameter multi-start screw thread 2-5 of the precision grinding tool is provided with a precision grinding tool chip groove 2-6 with a depth of about 0.03mm to accommodate chips and excess abrasives. The outer circumference is provided with a rectangular adjustment groove 2-7 with a width of 2.5mm and five uniformly distributed circular process grooves 2-8 with a width of 0.8mm. One side of the rectangular adjustment groove is a light hole and the other side is a threaded hole. The adjustment screw is inserted from the light hole side and cooperates with the threaded hole on the other side through the spring washer 2-2 and the adjustment flat washer 2-3; the rectangular adjustment groove 2-7 is used to adjust the tightness of the precision grinding tool, and the five uniformly distributed circular process grooves 2-8 with a width of 0.8mm are used to ensure that when the precision grinding tool is adjusted, the precision grinding tool as a whole undergoes uniform elastic deformation to avoid large ovality of the inner diameter multi-start screw thread 2-5 of the precision grinding tool.

[0046] Preferably, the lapping abrasives in the S8 preliminary lapping and the S10 multiple lapping are blended with white corundum (WA), kerosene, paraffin oil and lard in a mass ratio of 1:6:2:1; the particle size of the white corundum (WA) is 5 μm; since the main purpose of the lapping process is to improve the shape and dimensional accuracy of the ultra-large aspect ratio lead screw thread and improve the profile and surface quality of the load-bearing contact surface of the ultra-large aspect ratio lead screw thread, paraffin oil and lard are added to increase the lubricating properties of the lapping abrasive. In addition, since the precision lapping speed is relatively low, the amount of material removed in a single precision lapping is relatively small, the friction force is also greatly reduced accordingly, and the heat generated during the lapping process is also relatively small, so the mass proportion of kerosene is appropriately reduced.

[0047] Preferably, the modulated polishing agent in the S12 thread polishing is prepared by blending chromium trioxide and oleic acid in a mass ratio of 1:1. Since chromium trioxide has certain toxicity, the operator must wear anti-toxic protective gear when polishing the ultra-large aspect ratio multi-start screw thread.

[0048] Parts not described in detail in the present invention belong to the well-known technology in the field.

[0049] The above-described specific embodiments are only preferred embodiments of the present invention and are not exhaustive of feasible embodiments of the present invention. For those skilled in the art, any obvious modifications made thereto without departing from the principles and spirit of the present invention should be considered to be included within the scope of protection of the claims of the present invention.

Claims

1. A method for precision grinding of multi-start lead screws with a large aspect ratio, characterized in that: The specific steps include: S1 constant temperature treatment: placing the ultra-large aspect ratio multi-start lead screw in a processing environment for constant temperature treatment for more than 3 hours, ensuring that the processing environment temperature is stable within the range of 20°C ± 2°C; S2 cleaning parts: first, the super-large aspect ratio multi-start lead screw is hoisted and clamped on a special grinding table, and then the threads of the super-large aspect ratio multi-start lead screw are thoroughly cleaned with detergent or anhydrous ethanol and non-woven silk cloth to remove surface impurities; S3 precision self-test: Lever micrometers are set up at both ends of the super-large aspect ratio multi-start lead screw to align the reference outer circle of the super-large aspect ratio multi-start lead screw to within 0.005mm, and the threads of the super-large aspect ratio multi-start lead screw are precision turned. Grinding allowances are evenly reserved at all locations on the contour surface of the super-large aspect ratio multi-start lead screw thread. Then, the super-large aspect ratio lead screw thread is tested with special testing equipment to determine the size and shape error, profile and surface allowance of the super-large aspect ratio lead screw thread; S4 Rough Grinding Marking: Preliminary grinding of the super-large aspect ratio multi-start lead screw thread using a rough grinding tool and a prepared rough grinding abrasive. Based on the color distribution of the rough grinding tool and the surface of the super-large aspect ratio multi-start lead screw thread, the contact between the tool thread and the super-large aspect ratio multi-start lead screw thread is preliminarily determined. The distribution of the high and low points of the ellipse of the super-large aspect ratio multi-start lead screw thread is then determined and marked, and compared with the test results after precision turning. S5 rough grinding and repair type: according to the mark made in step S4, the rough grinding abrasive is evenly applied to the surface of the super-large aspect ratio screw thread, and the high point of the super-large aspect ratio screw thread is focused on grinding with a rough grinding tool. The grinding pressure and residence time are appropriately increased at the high point of the super-large aspect ratio screw thread, and the low point of the super-large aspect ratio screw thread is lightly passed over to remove burrs; the rough grinding is repeated several times, and the color distribution of the surface of the super-large aspect ratio screw thread is observed until the super-large aspect ratio screw thread and the contour surface of the screw thread of the rough grinding tool can be fully fitted; during the rough grinding process, multiple sets of rough grinding tools must be prepared, and the rough grinding tools must be replaced every 20 minutes to 30 minutes to ensure that the rough grinding tools are evenly worn and avoid excessive wear or uneven wear of the rough grinding tools causing large processing errors; during the rough grinding process, the grinding linear speed is controlled within the range of 40 to 45 m / min; S6 cleaning parts: use detergent or anhydrous ethanol and non-woven silk cloth to thoroughly clean the threads of the large aspect ratio multi-start screw to remove abrasives and chips; S7 allowance self-inspection: Use special inspection equipment to inspect the super-large aspect ratio screw thread to determine the grinding allowance, size, form and position error, and tooth surface profile of the super-large aspect ratio screw thread, so that the grinding allowance of the super-large aspect ratio screw thread is 0.01-0.02mm, and the size, form and position error, and tooth surface profile meet more than 75% of the technical index requirements; S8 Preliminary Lapping: Evenly apply the prepared lapping agent to the surface of the super-large aspect ratio lead screw thread, and use a lapping tool to perform preliminary lapping on the entire super-large aspect ratio lead screw thread; according to the resistance of the lapping tool at different positions of the super-large aspect ratio lead screw thread, determine the positions of the super-large aspect ratio lead screw thread with large shape and dimensional errors, and focus on lapping the positions with large grinding resistance by increasing the grinding pressure and dwell time until the resistance is uniform and smooth; before the preliminary lapping, add a copper sheet to the rectangular adjustment groove of the lapping tool, and properly tighten the adjustment screw of the lapping tool to adapt to the grinding allowance at various positions of the tooth surface profile of the super-large aspect ratio lead screw thread; S9 cleaning parts: use detergent or anhydrous ethanol and non-woven silk cloth to thoroughly clean the threads of the large aspect ratio multi-start screw to remove abrasives and chips; S10 multiple lapping: evenly applying the prepared lapping abrasive to the surface of the thread of the super-large aspect ratio lead screw, and again using a lapping tool to perform multiple precision lapping on the thread of the super-large aspect ratio lead screw; Remove the copper scale, and according to the resistance during the precision grinding process, appropriately adjust the adjustment screw of the precision grinding tool, and gradually tighten the precision grinding tool to adapt to the change in the thread size of the large aspect ratio multi-start screw during the precision grinding process; During the precision grinding process, the grinding line speed is controlled within the range of 30 to 35 m / min. During the precision grinding process, multiple sets of precision grinding tools must be prepared. Each time a precision grinding is completed, the precision grinding tool is replaced to ensure uniform wear of the precision grinding tool and avoid excessive wear or uneven wear of the precision grinding tool, which may cause large processing errors. S11 final precision inspection: the threads of the super-large aspect ratio multi-start lead screw are thoroughly cleaned, and a special inspection device is used to conduct a final precision inspection on the threads of the super-large aspect ratio lead screw to determine whether the technical indicators of the size and shape tolerance, profile, circular runout, pitch and surface quality of the threads of the super-large aspect ratio lead screw meet the requirements of the drawing; if so, proceed to step S12; otherwise, repeat steps S9 and S10; S12 thread polishing: Use a silk cloth tape soaked in a modulated polishing agent to polish the super-large aspect ratio multi-start screw thread multiple times throughout the entire process until the finish of all tooth surfaces of the super-large aspect ratio multi-start screw thread meets the requirements of the drawing; the silk cloth tape soaked in the modulated polishing agent must be continuously replaced during the polishing process, and the operator must wear anti-toxic protective gear and protective gloves.

2. The grinding method according to claim 1, wherein The last precision turning is performed before the precision grinding process. During turning, a grinding allowance of 0.05 to 0.07 mm is evenly reserved at various locations on the thread profile surface of the super-large aspect ratio multi-start lead screw according to the requirements of the drawing.

3. The grinding method according to claim 1, wherein The rough grinding tool is made of gray cast iron and has a half-moon shape of 1 / 3 circle, an axial length of 300mm, a radial thickness of 20mm, and an inner diameter processed into a 1:1 multi-start screw thread structure according to the design parameters of the super-large aspect ratio multi-start screw; the tooth profile accuracy of the inner diameter multi-start screw thread of the rough grinding tool should be the same as the design accuracy of the super-large aspect ratio multi-start screw thread, and a chip groove with a depth of about 0.1mm is provided at the bottom diameter position of the inner diameter multi-start screw thread of the rough grinding tool to accommodate grinding chips and excess abrasive; the sharp edges of the inner diameter multi-start screw thread of the rough grinding tool are chamfered to prevent scratches on the screw thread surface.

4. The grinding method according to claim 1, wherein The rough grinding abrasive is blended with white corundum, kerosene, and paraffin oil in a mass ratio of 2:17:1; the particle size of the white corundum is 10 μm; the kerosene in the rough grinding abrasive can remove the heat generated during the rough grinding process through volatilization, thereby reducing the impact of the heat generated during the rough grinding process on the processing accuracy of the ultra-large aspect ratio lead screw.

5. The grinding method according to claim 1, wherein The lapping tool consists of an adjusting screw, a spring washer, an adjusting flat washer and a cast iron grinding sleeve; the adjusting screw, spring washer and adjusting flat washer are all standard parts; the cast iron grinding sleeve is made of gray cast iron, has a round shape, an axial length of 300mm, a radial thickness of 20mm, and an inner diameter processed into a 1:1 multi-start screw thread structure according to the design parameters of the super-large aspect ratio multi-start screw thread. The tooth profile accuracy of the inner diameter multi-start screw thread of the lapping tool should be higher than the design accuracy of the super-large aspect ratio multi-start screw thread. The bottom diameter position of the inner diameter multi-start screw thread of the lapping tool is provided with a chip groove with a depth of about 0.05mm, which is used for To accommodate grinding chips and excess abrasives; the outer circumference of the lapping tool is provided with a rectangular adjustment groove with a width of 2.5mm and five evenly distributed circular process grooves with a width of 0.8mm. One side of the rectangular adjustment groove is a light hole and the other side is a threaded hole. The adjustment screw is inserted from the light hole side and cooperates with the threaded hole on the other side through a spring washer and an adjustment flat washer; the rectangular adjustment groove is used to adjust the tightness of the lapping tool, and the five evenly distributed circular process grooves with a width of 0.8mm are used to ensure that when the lapping tool is adjusted, the lapping tool as a whole undergoes uniform elastic deformation to avoid large ovality of the inner diameter multi-start screw thread of the lapping tool.

6. The grinding method according to claim 1, wherein: The lapping agent is prepared by blending white corundum, kerosene, paraffin oil and lard in a mass ratio of 1:6:2:1; the particle size of the white corundum is 5 μm; and the lubricating properties of the lapping agent are improved by increasing the mass ratio of paraffin oil and lard in the lapping agent.

7. The grinding method according to claim 1, wherein: The prepared polishing agent in the S12 thread polishing is prepared by blending chromium trioxide and oleic acid in a mass ratio of 1:1.

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