A grinding tool and grinding method for internal hole grinding of hard and brittle pipe fittings with a large length-diameter ratio

Abstract

A grinding tool and grinding method for the internal hole grinding of hard and brittle pipe fittings with a large length-diameter ratio, belonging to the field of hard and brittle material processing. In order to solve the problems that hard and brittle pipe fittings are prone to damage and difficult to ensure machining accuracy during the processing due to their high hardness and brittle characteristics, as well as the characteristics of an extremely large length-diameter ratio and a relatively thin finished wall thickness. The present invention is a grinding tool with a large length-diameter ratio formed by alternating arrangements of annular grinding heads and annular grooves. Along the length direction of the grinding tool, it is divided into a guiding section, a taper section, and a sizing section. The grinding tool passes through the internal hole of the hard and brittle pipe fitting via the guiding section and is straightened. The grinding tool rotates, and while the hard and brittle pipe fitting advances from the guiding section to the sizing section side, it also makes a reciprocating motion until the hard and brittle pipe fitting moves to the sizing section and is ground, so as to achieve the processing of the internal hole of the hard and brittle pipe fitting. The present invention is mainly used for the processing of hard and brittle pipe fittings.

Description

Technical Field

[0001] The invention belongs to the field of hard and brittle material processing, and in particular relates to a grinding tool and a grinding method for grinding the inner hole of a hard and brittle pipe with a large aspect ratio. Background Art

[0002] Ceramic tubes, with their excellent physical and chemical properties, are widely used in the semiconductor, nuclear energy, and aerospace industries. For example, in the nuclear energy sector, silicon carbide ceramic tubes are used as inner lining tubes, while in the semiconductor field, silicon carbide tubes are used as heat exchange tubes. These tubes are generally over 1000mm long and have an inner diameter of 7-8mm. They not only possess high hardness and brittleness, but also have a large aspect ratio and thin wall thickness. This makes ceramic tubes with large aspect ratios susceptible to damage during machining, making it difficult to perform fine finishing on the inner wall. Summary of the Invention

[0003] In view of this, the present invention provides a grinding tool and grinding method for grinding the inner hole of hard and brittle pipes with a large aspect ratio. The segmented grinding tool is used to reduce the resistance between the grinding tool and the inner wall of the pipe, thereby realizing the processing of hard and brittle pipes with a large aspect ratio.

[0004] The technical solution adopted by the present invention to solve the above technical problems is:

[0005] A grinding tool for grinding the inner bore of hard and brittle pipe fittings with a large aspect ratio is provided. The grinding tool comprises an annular grinding head and annular grooves arranged alternately. The grinding tool is divided into three sections along its length: a guide section, a tapered section, and a sizing section. The guide section is used to penetrate the inner bore of the hard and brittle pipe fitting, the tapered section is used to grind and expand the inner bore of the hard and brittle pipe fitting, and the sizing section is used to grind the inner bore of the hard and brittle pipe fitting.

[0006] The grinding tool passes through the inner hole of the hard and brittle pipe through the guide section and straightens it. The grinding tool rotates, and the hard and brittle pipe moves from the guide section to the sizing section while also making reciprocating motion until the hard and brittle pipe moves to the sizing section and is ground to achieve the processing of the inner hole of the hard and brittle pipe.

[0007] Preferably, the length ratio of the guide section, the tapered section and the sizing section is 1:3:1 to 1:4:1; the length ratio of the hard and brittle pipe to the guide section is 5:6.

[0008] Preferably, the annular grinding head of the guide section is a guide grinding head of equal diameter.

[0009] Preferably, the annular grinding head of the tapered section is an expanding grinding head with a taper, and the outer diameter of the expanding grinding head gradually increases along the advancing direction of the hard and brittle pipe.

[0010] Preferably, the annular grinding head of the sizing section is a sizing grinding head of equal diameter.

[0011] Preferably, a liquid injection channel is formed along the length direction inside the grinding tool, and a liquid discharge hole penetrating the liquid injection channel is formed at the annular groove. Grinding liquid or coolant is injected into the liquid injection channel, and the grinding liquid or coolant is thrown to the annular groove to cool or grind the inner hole of the hard and brittle pipe fitting.

[0012] Preferably, diamond micropowder is electroplated on the surface of the annular grinding head to make a rough machining grinding tool; or the surface of the annular grinding head is textured to make a finish machining grinding tool.

[0013] A method for grinding the inner hole of a hard and brittle pipe fitting with a large length-diameter ratio is as follows:

[0014] S1. Determine the number of machining times of the hard and brittle pipe fitting, the number of grinding tools, and the outer diameter size of each grinding tool:

[0015] Let the target size of the inner hole of the hard and brittle pipe fitting be , the actual minimum inner diameter of the inner hole of the hard and brittle pipe fitting be , the single-pass grinding amount of the hard and brittle pipe fitting be and the taper difference of the taper section of the grinding tool be . The number of grinding tools is m; the number of machining times n of the hard and brittle pipe fitting is expressed as:

[0016]

[0017] The diameter of the sizing grinding head of the i-th grinding tool satisfies the following relationship:

[0018]

[0019] The diameter of the guiding grinding head of the i-th grinding tool satisfies the following relationship:

[0020]

[0021] S2. According to the number of machining times of the hard and brittle pipe fitting, in the order of the 1st to the m-th grinding tools, successively machine the inner hole of the hard and brittle pipe fitting;

[0022] S21 Rough machining stage: The rough machining grinding tool penetrates the inner hole of the hard and brittle pipe fitting and is straightened. While the rough machining grinding tool rotates, keep coolant between the annular groove and the inner wall of the hard and brittle pipe fitting. While the hard and brittle pipe fitting advances from the guiding section to the sizing section, it also reciprocates until the hard and brittle pipe fitting moves to the sizing section and is ground to achieve rough machining of the inner hole of the hard and brittle pipe fitting. <>

[0023] S22, Finishing stage: The finishing grinding tool penetrates through the inner hole of the hard and brittle pipe fitting and straightens it. While the finishing grinding tool rotates, keep the grinding fluid between the annular groove and the inner wall of the hard and brittle pipe fitting. While the hard and brittle pipe fitting advances from the guiding section towards the sizing section, it also reciprocates until the hard and brittle pipe fitting moves to the sizing section and is ground to achieve the finishing of the inner hole of the hard and brittle pipe fitting.

[0024] Preferably, in S1, free-falling coolant is provided on both sides of the roughing grinding tool. The coolant is sucked into the annular groove of the roughing grinding tool, and the hard and brittle pipe fitting moves forward to ensure that there is coolant between the annular groove and the inner wall of the hard and brittle pipe fitting. In S2, free-falling polishing fluid is provided on both sides of the finishing grinding tool. The polishing fluid is sucked into the annular groove of the finishing grinding tool, and the hard and brittle pipe fitting moves forward to ensure that there is polishing fluid between the annular groove and the inner wall of the hard and brittle pipe fitting.

[0025] Preferably, a liquid injection channel is formed along the length direction inside the roughing grinding tool, and a drain hole penetrating through the liquid injection channel is formed at the annular groove. Coolant is injected into the liquid injection channel, and the coolant is thrown to the annular groove to ensure that there is coolant between the annular groove and the inner wall of the hard and brittle pipe fitting. A liquid injection channel is formed along the length direction inside the finishing grinding tool, and a drain hole penetrating through the liquid injection channel is formed at the annular groove. Grinding fluid is injected into the liquid injection channel, and the grinding fluid is thrown to the annular groove to ensure that there is polishing fluid between the annular groove and the inner wall of the hard and brittle pipe fitting.

[0026] The beneficial effects of the present invention compared with the prior art are as follows:

[0027] 1. The grinding tool adopts a segmented structure. During the process of machining the inner hole of the hard and brittle pipe fitting, only the grinding head part contacts the inner wall of the workpiece to achieve the machining of the inner hole, while the part of the annular groove can effectively reduce the contact area between the grinding tool and the inside of the pipe fitting, thereby reducing the resistance during the grinding of the pipe fitting and preventing the phenomenon that the pipe fitting with a large length-diameter ratio is stuck with the grinding tool during the grinding process.

[0028] 2. During the machining process, an annular cavity is formed between the annular groove and the inner wall of the workpiece, which can effectively store the coolant or grinding fluid. If the coolant is stored in the annular cavity, the cooling of the inner hole machining of the workpiece can be achieved. If the grinding fluid is stored in the annular cavity, during the rotation of the grinding tool, the grinding fluid will generate a swirling flow in the annular cavity, which can, to a certain extent, produce a grinding effect on the inner wall of the pipe fitting and improve the machining accuracy of the workpiece. In addition, the chips generated during the grinding of the inner hole of the workpiece can be stored in the coolant or grinding fluid, avoiding scratches on the inner wall of the inner hole of the workpiece and affecting the machining accuracy of the workpiece. And during the reciprocating movement of the workpiece, the grinding fluid or coolant will flow out to clean the chips.

[0029] 3. Due to the high hardness and brittleness characteristics of the hard and brittle pipe fittings, during the rotation of the grinding tool and the large-span reciprocating movement of the workpiece, a tapered expanding grinding head can be used to achieve progressive reaming processing layer by layer, reducing the probability of low damage to the hard and brittle pipe fittings. After reaming processing, the repeated grinding of the sizing grinding head can further ensure the coaxiality of the inner hole of the pipe fitting.

[0030] 4. The length ratio of the guiding section, tapered section, and sizing section of the grinding tool is 1:3:1 to 1:4:1, and the length ratio of the workpiece to the guiding section is 5:6, which can ensure a reasonable proportional length between the workpiece and the tool, achieve fine machining of the workpiece, and will not cause the tool to be too long, which is not conducive to rotation and support.

[0031] 5. The present invention can adopt two methods to evenly distribute the coolant and grinding fluid in the grinding area. One is to open a liquid injection channel in the grinding tool, and inject the grinding fluid or coolant into the liquid injection channel by pumping the coolant or grinding fluid, so as to evenly distribute the coolant and grinding fluid in the grinding area and ensure the grinding quality of the inner hole of the workpiece. Since the grinding tool is relatively long, some grinding fluid or coolant may flow out. The drain holes of the part that does not participate in grinding can be plugged, and the opening position of the drain holes can be manually controlled as the grinding process progresses. The other is to respectively provide free-falling coolant / polishing fluid on both sides of the grinding tool. Based on Bernoulli's principle, during the rotation of the grinding tool, a negative pressure is formed on the surface of the grinding tool, and the coolant or grinding fluid is sucked into the annular groove. During the forward movement of the hard and brittle pipe fitting, the grinding tool wrapped with the coolant or grinding fluid on the surface is covered to ensure that there is coolant / polishing fluid between the annular groove and the inner wall of the hard and brittle pipe fitting. BRIEF DESCRIPTION OF THE DRAWINGS

[0032] The drawings, as a part of this application, are used to provide a further understanding of the present invention.

[0033] Figure 1 It is a schematic structural diagram of the rough machining grinding tool of the present invention.

[0034] Figure 2 It is a schematic structural diagram of the fine machining grinding tool of the present invention.

[0035] Figure 3 It is a processing method for maintaining coolant or grinding fluid between the annular groove and the inner wall of the hard and brittle pipe fitting by adopting the liquid spraying method in Embodiment 3.

[0036] Figure 4 It is a processing method for maintaining coolant or grinding fluid between the annular groove and the inner wall of the hard and brittle pipe fitting by adopting the liquid pumping method in Embodiment 2.

[0037] Figure 5 It is a diagram of the outer diameter size change of the grinding tools from the 1st to the (n + 1)th.

[0038] Explanation of the reference numerals: 1-guide section; 1-1-guide grinding head; 2-taper section; 2-1-diameter-expanding grinding head; 3-sizing section; 3-1-sizing grinding head; 4-annular groove; 5-hard and brittle pipe fitting; 6-plug. DETAILED DESCRIPTION

[0039] The present invention is described in detail below with reference to specific embodiments.

[0040] Example 1:

[0041] See also Figure 1 The embodiment of the present application provides a grinding tool for grinding the inner hole of a hard and brittle pipe with a large aspect ratio. It is a segmented grinding tool with a large aspect ratio formed by alternating annular grinding heads and annular grooves 4. Along the length direction of the grinding tool, it is divided into three sections, namely a guide section 1 with gradually increasing outer diameters, a tapered section 2, and a sizing section 3. The guide section 1 is used to pass through the inner hole of the hard and brittle pipe 5, and the annular grinding head of the guide section 1 is a guide grinding head 1-1 with a constant diameter. The tapered section 2 is used for grinding and expanding the inner hole of the hard and brittle pipe 5. The annular grinding head of the tapered section 2 is an expanding grinding head 2-1 with a taper, and the outer diameter of the expanding grinding head 2-1 gradually increases along the forward direction of the hard and brittle pipe 5. The sizing section 3 is used for grinding the inner hole of the hard and brittle pipe 5, and the annular grinding head of the sizing section 3 is a sizing grinding head 3-1 with a constant diameter. During the machining of the hard and brittle pipe 5, the grinding tool penetrates the inner bore of the hard and brittle pipe 5 via the guide section 1 and straightens it. The grinding tool rotates, and the hard and brittle pipe 5 moves along the length of the grinding tool from the guide section 1 toward the sizing section 3, while also performing reciprocating motion, until the hard and brittle pipe 5 moves to the sizing section 3 and is ground, completing the machining of the inner bore of the hard and brittle pipe 5. The length of the annular groove 4 and the annular grinding head is generally 20 to 40 mm, and the depth of the annular groove 4 is generally 0.4 to 0.6 mm.

[0042] The grinding tool in this embodiment adopts a segmented structure. During the process of machining the inner hole of the hard and brittle pipe fitting 5, only the annular grinding head part, such as the guiding grinding head 1-1, the diameter-expanding grinding head 2-1, and the sizing grinding head 3-1, contacts the inner wall of the hard and brittle pipe fitting 5 to achieve the machining of the inner hole. The part of the annular groove 4 can effectively reduce the contact area between the grinding tool and the inside of the pipe fitting, thereby reducing the resistance during the grinding process of the pipe fitting and preventing the phenomenon of jamming between the pipe fitting with a large length-diameter ratio and the grinding tool during the grinding process. At the same time, during the machining process, an annular cavity is formed between the annular groove 4 and the inner wall of the hard and brittle pipe fitting 5, which can effectively store the coolant or grinding fluid. If the coolant is stored in the annular cavity, the cooling of the inner hole machining of the hard and brittle pipe fitting 5 can be achieved. If the grinding fluid is stored in the annular cavity, during the rotation of the grinding tool, the grinding fluid will generate a swirling flow in the annular cavity, which can, to a certain extent, produce a grinding effect on the inner wall of the pipe fitting and improve the machining accuracy of the hard and brittle pipe fitting 5. In addition, the chips generated during the grinding process of the inner hole of the hard and brittle pipe fitting 5 can be stored in the coolant or grinding fluid to avoid scratches on the inner wall of the inner hole of the hard and brittle pipe fitting 5, which affects the machining accuracy of the hard and brittle pipe fitting 5. And during the reciprocating movement of the hard and brittle pipe fitting 5, the grinding fluid or coolant will flow out to clean the chips. Due to the high hardness and brittle characteristics of the hard and brittle pipe fitting 5, during the rotation of the grinding tool and the reciprocating forward movement of the hard and brittle pipe fitting 5, the tapered diameter-expanding grinding head 2-1 can be used to achieve step-by-step reaming. If the whole grinding tool has an equal-diameter structure, it is easy to cause low damage to the hard and brittle pipe fitting 5. After the reaming process, by repeatedly grinding with the sizing grinding head 3-1, the coaxiality of the inner hole of the pipe fitting can be further ensured.

[0043] Since the grinding tool grinds the inner hole of the hard and brittle pipe fitting 5, it needs to be inserted into the inner hole of the hard and brittle pipe fitting 5 for grinding. However, the hard and brittle pipe fitting 5 has the characteristic of a large length-diameter ratio. The relatively long hard and brittle pipe fitting 5 may reach about 4m. The inner diameter size of the hard and brittle pipe fitting 5 is approximately between 7.5mm and 8.5mm. At the same time, the inner hole of the hard and brittle pipe fitting 5 needs to move back and forth significantly during the grinding process. This requires the length of the grinding tool to be at least 5 times the length of the hard and brittle pipe fitting 5. The grinding tool is prone to bending under such a length and a relatively small outer diameter, thus affecting the machining of the surface of the hard and brittle pipe fitting 5. Therefore, it is necessary to pass through the inner hole of the hard and brittle pipe fitting 5 and straighten it. The starting position of the hard and brittle pipe fitting 5 before grinding is the guiding section 1. Therefore, the length of the guiding section 1 should be greater than the length of the hard and brittle pipe fitting 5. The sizing section 3 ensures the coaxiality of the inner hole of the hard and brittle pipe fitting 5. Therefore, the length of the sizing section 3 should also be greater than the length of the hard and brittle pipe fitting 5. Therefore, the length ratio of the guiding section 1, the taper section 2, and the sizing section 3 in this embodiment is 1:3:1 to 1:4:1, and the length ratio of the hard and brittle pipe fitting 5 to the guiding section 1 is 5:6. This can ensure a reasonable proportional length between the hard and brittle pipe fitting 5 and the tool, achieve fine machining of the hard and brittle pipe fitting 5, and at the same time, it will not cause the tool to be too long, which is not conducive to rotation and support. If the ratio of these three parts of the grinding tool is too large, it will result in an extremely long machining tool. For example, if the length of the processed pipe is 1.2 meters, then the length of the sizing section 3 and the guiding section 1 should be at least 1.2 meters, and the length of the taper section is at least 3 to 3.6 meters. The total length of the grinding tool reaches at least 5 meters. If the ratio of these three parts of the grinding tool is 1:1:1, it will result in too large a taper span in the taper part, and the hard and brittle pipe fitting 5 cannot be ground. If the ratio is 1:5:1, the total length of the tool is too large, which is not conducive to rotation and support.

[0044] Since it is necessary to inject coolant or grinding fluid into the annular groove 4 of the grinding tool, but after the brittle pipe fitting 5 is sleeved on the grinding tool, a nearly closed annular cavity is formed between the brittle pipe fitting 5 and the annular groove 4, and the coolant or grinding fluid cannot be injected from the outside. This makes it impossible to cool the brittle pipe fitting 5 and the tool, and is also not conducive to the discharge of grinding debris. For this reason, in this embodiment, a liquid injection channel is opened along the length direction inside the grinding tool. The inner diameter of the liquid injection channel is 2-4 mm (since the inner diameter of the brittle pipe fitting 5 is only 7.5 mm - 8.5 mm). A drain hole penetrating the liquid injection channel is opened at the annular groove 4. The grinding fluid or coolant is injected into the liquid injection channel by pumping the coolant or grinding fluid. The grinding fluid or coolant is thrown to the annular groove 4 to make the coolant and grinding fluid evenly distributed in the grinding area, ensuring the grinding quality of the inner hole of the brittle pipe fitting 5. Since the grinding tool is relatively long, some grinding fluid or coolant may flow out. The drain holes in the part that does not participate in grinding can be plugged with plugs 6, and the opening position of the drain hole can be manually controlled as the grinding process progresses. Another processing method for the delivery of the coolant or grinding fluid in this embodiment is that free-falling coolant / polishing fluid is respectively arranged on both sides of the grinding tool. Based on Bernoulli's principle, during the rotation of the grinding tool, a negative pressure is formed on the surface of the grinding tool, and the coolant or grinding fluid is sucked into the annular groove 4. During the forward movement of the brittle pipe fitting 5, the grinding tool with coolant or grinding fluid wrapped on its surface is covered to ensure that there is coolant / polishing fluid between the annular groove 4 and the inner wall of the brittle pipe fitting 5. In this way, there is no need to open a liquid injection channel in the grinding tool, nor to drill holes, ensuring the rigidity of the grinding tool. Additionally, it should be noted that in this embodiment, the coolant or grinding fluid is not sprayed onto the grinding tool by spraying, because spraying will generate an impact force on the grinding tool, affecting the stability of the grinding tool during the grinding process, and further affecting the machining accuracy of the inner hole of the brittle pipe fitting 5.

[0045] Since the inner hole of the brittle pipe fitting 5 needs to be processed in two steps, namely rough machining and finish machining, the grinding tools in this embodiment include two types. One is the rough machining tool for the rough machining stage, that is, diamond micropowder is electroplated on the surfaces of the guiding grinding head 1-1, the diameter-expanding grinding head 2-1, and the sizing grinding head 3-1. The particle size of the abrasive grains is 5-10 um, and the diameter change of the taper section 2 is +0.05 mm / m from the guiding section 1 to the sizing section 3 direction. The other is the finish machining tool for the finish machining stage, that is, texturing treatment is performed on the surfaces of the guiding grinding head 1-1, the diameter-expanding grinding head 2-1, and the sizing grinding head 3-1. The texture type is generally cross helical lines, the width of the helical lines is generally 1 mm, and the depth is generally about 100 um. The texturing treatment on the surface of the finish machining tool can improve the circulation of the grinding fluid and the coolant. The diameter change of the taper section 2 is +0.01 mm / m from the guiding section 1 to the sizing section 3 direction.

[0046] Embodiment 2:

[0047] This embodiment provides a method for internal hole grinding of hard and brittle pipe fittings with a large length-diameter ratio, which is realized by using a rough grinding tool and a finish grinding tool. The grinding steps are as follows:

[0048] S1. Determine the number of processing times of the hard and brittle pipe fitting, the number of grinding tools, and the outer diameter size of each grinding tool:

[0049] Let the target size of the inner hole of the hard and brittle pipe fitting be , the actual minimum diameter of the inner hole of the hard and brittle pipe fitting be , the single grinding amount of the hard and brittle pipe fitting and the taper difference of the taper section (the diameter difference from the starting position to the end position of the taper section of the taper section), and the number of grinding tools be m; in order to eliminate the initial size error of the inner hole of the hard and brittle pipe fitting, usually use the first grinding tool to preprocess the inner hole of the hard and brittle pipe fitting. The diameter size of the sizing section of the first grinding tool is the minimum inner circle diameter of the hard and brittle pipe fitting . When the hard and brittle pipe fitting still cannot pass effectively with the minimum inner circle diameter of the hard and brittle pipe fitting as the sizing section of the grinding tool, the number of preprocessing grinding times should be considered increased. Therefore, the number of processing times n of the hard and brittle pipe fitting is expressed as:

[0050]

[0051] The diameter of the sizing grinding head of the i-th grinding tool satisfies the following relationship:

[0052]

[0053] The diameter of the guiding grinding head of the i-th grinding tool satisfies the following relationship:

[0054]

[0055] S2. According to the number of processing times of the hard and brittle pipe fitting, process the inner hole of the hard and brittle pipe fitting in sequence according to the order of the first to the m-th grinding tools;

[0056] S21. Rough machining stage: Use the guiding section 1 of the rough machining grinding tool to penetrate the inner hole of the hard and brittle pipe fitting 5, straighten the rough machining grinding tool and support it by the supporting device. The rough machining grinding tool rotates uniformly at a speed of 100 rpm / min. At the same time, free-falling coolant is provided on both sides of the rough machining grinding tool. The coolant is sucked into the annular groove 4 of the rough machining grinding tool. The hard and brittle pipe fitting 5 moves forward to keep the coolant between the annular groove 4 and the inner wall of the hard and brittle pipe fitting 5. The hard and brittle pipe fitting 5 moves back and forth in a large span along the length direction of the rough machining grinding tool from the guiding section 1 to the sizing section 3 side until the hard and brittle pipe fitting 5 moves to the sizing section 3 and is ground to realize the rough machining of the inner hole of the hard and brittle pipe fitting 5;

[0057] S22, Finishing stage: The guiding section 1 of the finishing grinding tool penetrates the inner hole of the hard and brittle pipe fitting 5, straightens the finishing grinding tool and is supported by the supporting device. The finishing grinding tool rotates uniformly at a speed of 100 rpm / min. At the same time, free-falling polishing liquid is provided on both sides of the finishing grinding tool. The polishing liquid is sucked into the annular groove 4 of the finishing grinding tool. The hard and brittle pipe fitting 5 moves forward to ensure that there is polishing liquid between the annular groove 4 and the inner wall of the hard and brittle pipe fitting 5. The hard and brittle pipe fitting 5 reciprocates in a large span from the guiding section 1 to the sizing section 3 side along the length direction of the finishing grinding tool until the hard and brittle pipe fitting 5 moves to the sizing section 3 and is ground to achieve the finishing of the inner hole of the hard and brittle pipe fitting 5.

[0058] Example 3:

[0059] This embodiment provides a method for grinding the inner hole of a hard and brittle pipe fitting with a large length-diameter ratio, which is realized by using a rough grinding tool with a liquid injection channel and a finishing grinding tool with a liquid injection channel. The grinding steps are as follows:

[0060] S1, Determine the number of processing times of the hard and brittle pipe fitting, the number of grinding tools, and the outer diameter size of each grinding tool:

[0061] Let the target size of the inner hole of the hard and brittle pipe fitting be , the actual minimum diameter of the inner hole of the hard and brittle pipe fitting be , the single grinding amount of the hard and brittle pipe fitting and the taper difference of the taper section (the diameter difference from the starting position to the end position of the taper section of the taper section), and the number of grinding tools be m; In order to eliminate the initial size error of the inner hole of the hard and brittle pipe fitting, usually the first grinding tool is used to preprocess the inner hole of the hard and brittle pipe fitting. The diameter size of the sizing section of the first grinding tool is the minimum inner diameter of the hard and brittle pipe fitting , when using the minimum inner diameter of the hard and brittle pipe fitting as the sizing section of the grinding tool and the hard and brittle pipe fitting still cannot pass effectively, the number of preprocessing grinding times should be considered. Therefore, the number of processing times n of the hard and brittle pipe fitting is expressed as:

[0062]

[0063] The diameter of the sizing grinding head of the i-th grinding tool satisfies the following relationship:

[0064]

[0065] The diameter of the guiding grinding head of the i-th grinding tool satisfies the following relationship:

[0066]

[0067] S2. According to the number of processing times of the hard and brittle pipe fittings, in the order of the grinding tools from the 1st to the mth, the inner holes of the hard and brittle pipe fittings are processed in sequence.

[0068] S21. Rough machining stage: Use the guiding section 1 of the rough machining grinding tool to penetrate the inner hole of the hard and brittle pipe fitting 5, and straighten the rough machining grinding tool. The rough machining grinding tool rotates uniformly at a speed of 100 rpm / min. At the same time, coolant is injected into the liquid injection channel by pumping the coolant. The coolant is thrown to the annular groove 4 to keep coolant between the annular groove 4 and the inner wall of the hard and brittle pipe fitting 5. The hard and brittle pipe fitting 5 reciprocates along the length direction of the rough machining grinding tool from the guiding section 1 to the sizing section 3 side until the hard and brittle pipe fitting 5 moves to the sizing section 3 and is ground to achieve rough machining of the inner hole of the hard and brittle pipe fitting 5.

[0069] S22. Finishing machining stage: Use the guiding section 1 of the finishing machining grinding tool to penetrate the inner hole of the hard and brittle pipe fitting 5, and straighten the finishing machining grinding tool. The finishing machining grinding tool rotates uniformly at a speed of 100 rpm / min. At the same time, grinding fluid is injected into the liquid injection channel by pumping the grinding fluid. The grinding fluid is thrown to the annular groove 4 to ensure that polishing fluid is between the annular groove 4 and the inner wall of the hard and brittle pipe fitting 5. The hard and brittle pipe fitting 5 reciprocates along the length direction of the finishing machining grinding tool to the sizing section 3 side until the hard and brittle pipe fitting 5 moves to the sizing section 3 and is ground to achieve finishing machining of the inner hole of the hard and brittle pipe fitting 5.

[0070] Example 2 and Example 3 are the same in all steps except for the liquid passing method. Using multiple grinding tools with proportionally increasing sizes to process the same hard and brittle pipe fitting in batches can not only ensure the grinding accuracy of the workpiece but also reduce the probability of low damage to the hard and brittle pipe fitting. The number of rough machining grinding tools used in the rough machining stage and the number of finishing machining grinding tools used in the finishing machining stage are determined according to the actual situation.

[0071] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, rather than limiting the protection scope of the present invention. Although the present invention has been described in detail with reference to the preferred embodiments, those of ordinary skill in the art should understand that the technical solutions of the present invention can be modified or equivalently replaced without departing from the essence and scope of the technical solutions of the present invention.

Claims

1. An internal hole grinding method for hard and brittle pipe fittings with a large length-diameter ratio, characterized in that It is realized by using a grinding tool for internal hole grinding of hard and brittle pipe fittings with a large length-diameter ratio. The grinding tool is a grinding tool with a large length-diameter ratio formed by alternating arrangement of annular grinding heads and annular grooves. Along the length direction of the grinding tool, it is divided into three sections, namely a guiding section, a taper section, and a sizing section. The guiding section is used to penetrate the internal hole of the hard and brittle pipe fitting. The taper section is used for grinding and reaming the internal hole of the hard and brittle pipe fitting. The sizing section is used for sizing grinding of the internal hole of the hard and brittle pipe fitting. The grinding tool penetrates through the internal hole of the hard and brittle pipe fitting via the guiding section and is straightened. The grinding tool rotates, and while the hard and brittle pipe fitting advances from the guiding section to the sizing section side, it also makes a reciprocating motion until the hard and brittle pipe fitting moves to the sizing section and is ground to realize the processing of the internal hole of the hard and brittle pipe fitting. Electroplating diamond micropowder on the surface of the annular grinding head to make a rough machining grinding tool; or performing texturing treatment on the surface of the annular grinding head to make a finishing grinding tool. The specific grinding process is as follows: S1. Determine the number of processing times of the hard and brittle pipe fitting, the number of grinding tools, and the outer diameter size of each grinding tool: Let the target size of the inner hole of the hard and brittle pipe fitting be D n , the actual minimum inner diameter of the inner hole of the hard and brittle pipe fitting is D nmin , the single grinding amount Δd of the hard and brittle pipe fitting and the taper difference Δa of the taper section of the grinding tool, and the number of grinding tools is m; the number of processing times n of the hard and brittle pipe fitting is expressed as: The diameter D of the sizing grinding head of the i-th grinding tool i+1 satisfies the following relationship: D i+1 = Δd + D i , i ∈ (0, n) The diameter D' of the guiding grinding head of the i-th grinding tool satisfies the following relationship: D' = D i+1 -Δa, i ∈ (0, n) S2. According to the number of processing times of the hard and brittle pipe fitting, in the order of the 1st to the m-th grinding tools, process the internal hole of the hard and brittle pipe fitting in sequence. S21. Rough machining stage: The rough machining grinding tool penetrates through the internal hole of the hard and brittle pipe fitting and is straightened. While the rough machining grinding tool rotates, keep the coolant in the annular groove between the inner wall of the hard and brittle pipe fitting. While the hard and brittle pipe fitting advances from the guiding section to the sizing section direction, it also makes a reciprocating motion until the hard and brittle pipe fitting moves to the sizing section and is ground to realize the rough machining of the internal hole of the hard and brittle pipe fitting. S22. Finishing stage: The finishing grinding tool penetrates through the internal hole of the hard and brittle pipe fitting and is straightened. While the finishing grinding tool rotates, keep the grinding fluid in the annular groove between the inner wall of the hard and brittle pipe fitting. While the hard and brittle pipe fitting advances from the guiding section to the sizing section direction, it also makes a reciprocating motion until the hard and brittle pipe fitting moves to the sizing section and is ground to realize the finishing of the internal hole of the hard and brittle pipe fitting.

2. The internal hole grinding method for a hard and brittle pipe fitting with a large length-diameter ratio according to claim 1, characterized in that, In S1, free-falling coolant is provided on both sides of the rough machining grinding tool. The coolant is sucked into the annular groove of the rough machining grinding tool. The hard and brittle pipe fitting moves forward to ensure that there is coolant between the annular groove and the inner wall of the hard and brittle pipe fitting. In S2, free-falling polishing fluid is provided on both sides of the finishing grinding tool. The polishing fluid is sucked into the annular groove of the finishing grinding tool. The hard and brittle pipe fitting moves forward to ensure that there is polishing fluid between the annular groove and the inner wall of the hard and brittle pipe fitting.

3. A method for internal hole grinding of a hard and brittle pipe fitting with a large length-diameter ratio according to claim 1, characterized in that A liquid injection channel is opened along the length direction inside the rough machining grinding tool, and a drain hole penetrating through the liquid injection channel is opened at the annular groove. Coolant is injected into the liquid injection channel, and the coolant is thrown to the annular groove to ensure that there is coolant between the annular groove and the inner wall of the hard and brittle pipe fitting. A liquid injection channel is opened along the length direction inside the finishing grinding tool, and a drain hole penetrating through the liquid injection channel is opened at the annular groove. Grinding fluid is injected into the liquid injection channel, and the grinding fluid is thrown to the annular groove to ensure that there is polishing fluid between the annular groove and the inner wall of the hard and brittle pipe fitting.

4. A method for internal hole grinding of a hard and brittle pipe fitting with a large length-diameter ratio according to claim 1, characterized in that, The length ratio of the guiding section, the taper section and the sizing section in S1 is 1:3:1 to 1:4:1; the length ratio of the hard and brittle pipe fitting to the guiding section is 5:

6.

5. A method for inner hole grinding of a hard and brittle pipe fitting with a large length-diameter ratio according to claim 1, characterized in that The annular grinding head of the guiding section in S1 is an equal-diameter guiding grinding head.

6. A method for internal hole grinding of a hard and brittle pipe fitting with a large length-diameter ratio according to claim 1, characterized in that The annular grinding head of the taper section in S1 is a diameter-expanding grinding head with a taper, and the outer diameter of the diameter-expanding grinding head gradually increases along the advancing direction of the hard and brittle pipe fitting.

7. A method for internal hole grinding of a hard and brittle pipe fitting with a large length-diameter ratio according to claim 1, characterized in that, The annular grinding head of the sizing section in S1 is an equal-diameter sizing grinding head.

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