A method suitable for machining the outer circle of high-precision hollow tubes using a centerless lathe

Abstract

The present invention relates to the technical field of hollow tube outer circle processing, and in particular to a method suitable for centerless lathe processing high-precision hollow tube outer circle. It includes the following steps: Step S1: debugging the machine tool; checking the coaxiality between the center of the cutter disc and the center of the hydraulic roller group at the input end, and controlling the coaxiality between the center of the cutter disc and the center of the hydraulic roller group at the input end to be less than or equal to 0.05-0.10 mm; Step S2: loading / trial verification; pre-detecting the wall thickness difference of the pipe to be processed, marking the thinnest wall thickness position; facing the thinnest part upwards and back to the roller, plugging the pipe mouth with a plug; starting the machine tool to automatically feed, stopping at 50 mm, exiting to perform outer circle and wall thickness detection, confirming whether the process parameters and machine tool tooling are normal; adjusting the tooling if abnormalities are found; Step S3: processing the outer circle. The present invention utilizes the performance of the centerless lathe to efficiently process the outer circle of the hollow tube, and finds a method suitable for hollow tubes with higher processing accuracy requirements through process control.

Description

Technical Field

[0001] The invention relates to the technical field of hollow tube outer circle processing, in particular to a method suitable for processing the outer circle of a high-precision hollow tube using a centerless lathe. Background Art

[0002] The outer circle processing of hollow tubes is usually assisted by a tool rest on a lathe, and the reverse rotation is used for processing with a reverse turning tool. During the turning process, the pipe fittings need to be turned repeatedly and the reference needs to be realigned. During the processing, the pipe fittings are prone to bending due to uneven radial force and uneven wall thickness deviation. The tool is easily stuck, resulting in the scrapping of the pipe fittings. The roughness requirement Ra≤3.2um needs to be met, and the processing speed is very slow, with an average feed speed of about 16.67mm / min.

[0003] The use of centerless lathes is suitable for processing solid round bars, and there is no eccentricity and flattening problem. However, when processing the outer circle of hollow tubes, although it can improve processing efficiency and reduce production costs, it is necessary to overcome the following technical defects to meet the processing quality: 1. It is necessary to correct the eccentricity problem during the processing of hollow tubes; 2. After the outer circle of the hollow tube is processed, the inner hole will be elliptical, and the through gauge cannot pass normally. Summary of the invention

[0004] The purpose of the present invention is to provide a method suitable for processing the outer circle of a high-precision hollow tube by a centerless lathe, utilizing the performance of the centerless lathe in efficiently processing the outer circle of the hollow tube, and finding a method suitable for processing the hollow tube with higher processing accuracy requirements through process control.

[0005] In order to solve the above technical problems, the present invention provides a method suitable for machining the outer circle of a high-precision hollow tube using a centerless lathe, comprising the following steps:

[0006] Step S1: Debugging the machine tool; checking the coaxiality between the center of the cutter head and the center of the hydraulic roller assembly at the input end, and controlling the coaxiality between the center of the cutter head and the center of the hydraulic roller assembly at the input end to be less than or equal to 0.05 to 0.10 mm;

[0007] Step S2: Loading / test run verification; pre-detect the wall thickness difference of the pipe to be processed and mark the thinnest wall thickness position; usually face the thinnest part upwards and away from the roller, plug the pipe mouth with a plug to prevent the entry of cutting fluid; start the machine tool automatic feeding, stop at about 50mm, exit to perform outer circle and wall thickness detection, and confirm whether the process parameters and machine tool tooling are normal; if abnormalities are found, adjust the tooling, adjust the tool processing diameter, and test run verification again until the processing is qualified;

[0008] Step S3: machining the outer circle; after adjusting the tooling and tool status, start the machine tool for automatic machining; observe the pipe transmission path at the outlet end, and perform manual intervention if any abnormality is found, and check whether the outer surface roughness of the pipe meets Ra3.2um. After machining a batch of pipes, stop the machine and replace the blade;

[0009] Step S4: Cutting / inspection; perform a through gauge test on the processed pipe fittings, and at the same time test the wall thickness, outer diameter, straightness and other indicators; production can only continue when the first pipe fitting is of qualified quality, otherwise, analyze the cause and correct it before processing the second pipe fitting, and batch processing will be carried out until it is qualified.

[0010] Preferably, step S1 is specifically as follows: a mandrel having a diameter the same as the outer diameter of the pipe to be processed is clamped by the hydraulic roller assembly at the input end of the centerless lathe, and a dial indicator is fixed on the cutter disc, and the dial indicator head is placed on the mandrel, the cutter disc is moved by hand, and the data displayed on the dial indicator is checked to control the coaxiality of the cutter disc center and the center of the hydraulic roller assembly at the input end to be less than or equal to 0.05-0.10 mm.

[0011] Preferably, in step S2, the thinnest wall thickness position is marked with “-*.*”.

[0012] Preferably, in step S2, after the pipe is withdrawn, it is detected that the wall thickness difference exceeds 0.5 mm or the thinnest wall thickness is less than the minimum specified wall thickness of 5.0 mm, and the wall thickness of the pipe before processing is compared to analyze whether the direction of the eccentricity is up or down eccentricity; according to the direction of the eccentricity, it is determined whether the thinnest side of the pipe is facing up or down, and another pipe is replaced and tested again for a section to measure and verify whether the result is qualified.

[0013] Preferably, if the processing wall thickness difference cannot be satisfied by adjusting the direction of the thinnest position of the pipe wall, the centerless machine tool equipment is required to be re-centered and the reference is adjusted, and the above steps are repeated until the processing quality meets the requirements.

[0014] Preferably, in step S4, when the pipe with an outer diameter of Φ90 mm is tested for through-gauge and it is found that it cannot pass the through-gauge of Φ79 mm smoothly, the roller pressure of the hydraulic roller group at the input end and the output end is adjusted, and the roller pressure is 0.6-0.7 Mpa.

[0015] Preferably, for the pipes that cannot be normally passed by the through gauge, the diameter of the inner hole ellipse is measured; the pipes with tolerance margins are re-bored using a floating knife, and the pipe diameter is controlled to be the maximum allowable size minus 0.1 mm.

[0016] Preferably, the ovality of the outer circle of the processed hollow tube is ≤0.15 mm.

[0017] Preferably, the centerless lathe is an MCT-100B (trolley) type external cylindrical centerless lathe. When it is working, the workpiece does not rotate, but the tool rotates, and four tools are evenly arranged in a circle. The cutting depth of the tool is 1.5-2.3mm, and the rotation speed is 210-230r / min; the feed speed of the centerless lathe is 600-700mm / min.

[0018] Compared with the prior art, the present invention has the following beneficial effects:

[0019] The present invention utilizes the performance of the centerless lathe to efficiently process the outer circle of the hollow tube, and finds a method suitable for processing the hollow tube with higher processing precision through process control. After the outer circle of the hollow tube is processed, all quality indicators are qualified: the wall thickness deviation is less than 0.5mm, the roughness requirement Ra≤3.2um, and there will be no flattening, and the ovality is ≤0.15mm. Through scientific research and judgment, determining the location, method, parameters, and unqualified correction of debugging is the key to the technology of the present invention. BRIEF DESCRIPTION OF THE DRAWINGS

[0020] Figure 1 The present invention is a flow chart of a method suitable for machining the outer circle of a high-precision hollow tube using a centerless lathe.

[0021] Figure 2 It is a structural dimension diagram of a hollow tube with a length of 4200 mm processed by an embodiment of the present invention. DETAILED DESCRIPTION

[0022] The present invention is further described in detail below in conjunction with the accompanying drawings and specific embodiments. The advantages and features of the present invention will become more apparent from the following description. It should be noted that the accompanying drawings are in very simplified form and in non-precise proportions, and are only used to conveniently and clearly assist in explaining the purpose of the embodiments of the present invention.

[0023] like Figures 1-2 As shown, the embodiment of the present invention specifically discloses a method suitable for machining the outer circle of a high-precision hollow tube using a centerless lathe, comprising the following steps:

[0024] Step S1: Debugging the machine tool; checking the coaxiality between the center of the cutter head and the center of the hydraulic roller assembly at the input end, and controlling the coaxiality between the center of the cutter head and the center of the hydraulic roller assembly at the input end to be less than or equal to 0.05 to 0.10 mm;

[0025] Step S2: Loading / test run verification; pre-detect the wall thickness difference of the pipe to be processed and mark the thinnest wall thickness position; usually face the thinnest part upwards and away from the roller, plug the pipe mouth with a plug to prevent the entry of cutting fluid; start the machine tool automatic feeding, stop at about 50mm, exit to perform outer circle and wall thickness detection, and confirm whether the process parameters and machine tool tooling are normal; if abnormalities are found, adjust the tooling, adjust the tool processing diameter, and test run verification again until the processing is qualified;

[0026] Step S3: machining the outer circle; after adjusting the tooling and tool status, start the machine tool for automatic machining; observe the pipe transmission path at the outlet end, and perform manual intervention if any abnormality is found, and check whether the outer surface roughness of the pipe meets Ra3.2um. After machining a batch of pipes, stop the machine and replace the blade;

[0027] Step S4: Cutting / inspection; perform a through gauge test on the processed pipe fittings, and at the same time test the wall thickness, outer diameter, straightness and other indicators; production can only continue when the first pipe fitting is of qualified quality, otherwise, analyze the cause and correct it before processing the second pipe fitting, and batch processing will be carried out until it is qualified.

[0028] In a specific embodiment of the present invention, step S1 is specifically as follows: a mandrel with a diameter the same as the outer diameter of the pipe to be processed is clamped by the hydraulic roller group at the input end of the centerless lathe, and a dial indicator is fixed on the cutter disc, and the dial indicator head is placed on the mandrel, the cutter disc is moved by hand, and the data displayed on the dial indicator is checked to control the coaxiality of the center of the cutter disc and the center of the hydraulic roller group at the input end to be less than or equal to 0.05 to 0.10 mm.

[0029] In a specific embodiment of the present invention, in step S2, the thinnest wall thickness position is marked with “-*.*”.

[0030] In a specific embodiment of the present invention, in step S2, after the pipe is withdrawn, it is detected that the wall thickness difference exceeds 0.5 mm or the thinnest wall thickness is less than the minimum specified wall thickness of 5.0 mm, and the wall thickness of the pipe before processing is compared to analyze whether the direction of the eccentricity is up or down eccentricity; according to the direction of the eccentricity, it is determined whether the thinnest side of the pipe is facing up or down, and a pipe is replaced and tested again for a section to measure and verify whether the result is qualified.

[0031] In a specific embodiment of the present invention, if the processing wall thickness difference cannot be satisfied by adjusting the direction of the thinnest wall thickness of the pipe, the centerless machine tool equipment is required to be re-centered and the reference is adjusted, and the above steps are repeated until the processing quality meets the requirements.

[0032] In a specific embodiment of the present invention, in step S4, when the through gauge test is performed on the pipe fitting with an outer diameter of Φ90 mm, if it is found that it cannot pass the through gauge of Φ79 mm smoothly, the roller pressure of the hydraulic roller group at the input end and the output end is adjusted, and the roller pressure is 0.6-0.7 Mpa.

[0033] In a specific embodiment of the present invention, for pipes that cannot be normally passed through by a through gauge, the diameter of the inner hole ellipse is measured; a floating knife is used to re-bored the pipes with tolerance margins, and the pipe diameter is controlled to the maximum allowable size minus 0.1 mm.

[0034] In a specific embodiment of the present invention, the ellipticity of the outer circle of the processed hollow tube is ≤0.15 mm.

[0035] In a specific embodiment of the present invention, the centerless lathe is an MCT-100B (trolley) type external cylindrical centerless lathe. When it is working, the workpiece does not rotate but the tool rotates. The pipe transmission contact parts are all bearing roller structures of the hydraulic roller group; and 4 circumferentially evenly arranged tools are used. The cutting depth of the tool is 1.5~2.3mm, and the rotation speed is 210~230r / min; the feed speed of the centerless lathe is 600~700mm / min.

[0036] The advantages and effects of processing hollow tubes by the adjusted centerless lathe in the embodiment of the present invention are as follows:

[0037] 1) The workpiece does not rotate, but the tool rotates: Since the process condition of the centerless lathe is that the workpiece does not rotate, the processing process reduces the influence caused by the straightness of the pipe; it overcomes the vibration phenomenon caused by the ordinary lathe processing technology, the workpiece rotates but the tool does not rotate, and the tool holder grinding head wears, which makes it easier to ensure that the wall thickness of the pipe does not deviate.

[0038] 2) The tools are arranged symmetrically and the cutting force is evenly distributed. The centerless lathe uses 4 tools that are evenly arranged on the circumference at the same time, and the radial force and axial force of turning are evenly distributed, overcoming the eccentricity problem that is easily caused by only one tool in the ordinary lathe processing technology.

[0039] 3) Fast turning speed and high production efficiency; the centerless lathe uses 4 tools at the same time, with a cutting depth of about 2mm, which increases the cutting speed and overcomes the shortcoming of low production efficiency of ordinary lathes with only one tool. The efficiency of the centerless lathe is about 30 times that of an ordinary lathe.

[0040] 4) The tooling wears slightly and the quality stability is good. After the tooling is adjusted on the centerless lathe, the transmission contact parts are all bearing roller structures, which have slight wear. No adjustment is required for processing workpieces of the same size. This overcomes the shortcomings of frequent tightening of the top contacts during ordinary lathe processing, which makes them easy to loosen.

[0041] The above description is only a description of the preferred embodiments of the present invention, and is not intended to limit the scope of the present invention. Any changes or modifications made by a person skilled in the art in the field of the present invention based on the above disclosure shall fall within the scope of protection of the claims.

Claims

1. A method suitable for machining the outer circle of a high-precision hollow tube using a centerless lathe, characterized in that: The steps include: Step S1: Debugging the machine tool; checking the coaxiality between the center of the cutter head and the center of the hydraulic roller assembly at the input end, and controlling the coaxiality between the center of the cutter head and the center of the hydraulic roller assembly at the input end to be less than or equal to 0.05 to 0.10 mm; Step S2: Loading / trial run verification; pre-detect the wall thickness difference of the pipe to be processed and mark the thinnest wall thickness position; turn the thinnest part upwards and away from the roller, and plug the pipe mouth with a plug; start the machine tool to automatically feed, stop at 50mm, exit to perform external circle and wall thickness detection, and confirm whether the process parameters and machine tool tooling are normal; if abnormalities are found, adjust the tooling, adjust the tool processing diameter, and conduct trial run verification again until the processing is qualified; Step S3: machining the outer circle; after adjusting the tooling and tool status, start the machine tool for automatic machining; observe the pipe transmission path at the outlet end, and perform manual intervention if any abnormality is found, and check whether the outer surface roughness of the pipe meets Ra3.2um. After machining a batch of pipes, stop the machine and replace the blade; Step S4: Cutting / inspection; Conducting a through gauge inspection on the processed pipe fittings, and at the same time inspecting the wall thickness, outer diameter, and straightness indicators; Production can only be continued if the first pipe fitting is of qualified quality; otherwise, the cause is analyzed and corrected before processing the second pipe fitting, and batch processing is carried out until it is qualified; The step S1 specifically comprises: clamping a mandrel with a diameter the same as the outer diameter of the pipe to be processed by the hydraulic roller group at the input end of the centerless lathe, fixing a dial indicator on the cutter head, and placing the dial indicator head on the mandrel, moving the cutter head by hand, and checking the data displayed on the dial indicator to control the coaxiality between the center of the cutter head and the center of the hydraulic roller group at the input end to be less than or equal to 0.05-0.10 mm; In the step S2, after the pipe is removed, if the wall thickness difference is greater than 0.5 mm or the thinnest wall thickness is less than the minimum specified wall thickness of 5.0 mm, the wall thickness of the pipe before processing is compared to analyze whether the direction of eccentricity is up and down eccentricity; determine whether the thinnest side of the pipe is facing up or down according to the direction of eccentricity, change a pipe and run it again for a section to measure and verify whether the result is qualified; In the step S4, when the pipe with an outer diameter of Φ90 mm is tested for a through gauge and it is found that the pipe cannot pass the through gauge of Φ79 mm smoothly, the roller pressure of the hydraulic roller group at the input end and the output end is adjusted, and the roller pressure is 0.6-0.7 Mpa; For pipes that cannot be passed through the through gauge, measure the diameter of the inner hole ellipse; use a floating knife to re-boring pipes with tolerance margins, and control the pipe diameter to the maximum allowable size minus 0.1mm.

2. A method for machining the outer circle of a high-precision hollow tube using a centerless lathe as claimed in claim 1, characterized in that: In step S2, the thinnest wall thickness position is marked as "-*.*".

3. A method for machining the outer circle of a high-precision hollow tube using a centerless lathe as claimed in claim 1, characterized in that: If the processing wall thickness difference cannot be satisfied by adjusting the direction of the thinnest wall thickness of the pipe, the centerless machine tool equipment must be re-aligned and the benchmark adjusted, and the above steps must be repeated until the processing quality meets the requirements.

4. A method for machining the outer circle of a high-precision hollow tube using a centerless lathe as claimed in claim 1, characterized in that: The ovality of the outer circle of the processed hollow tube is ≤0.15mm.

5. A method for machining the outer circle of a high-precision hollow tube using a centerless lathe as claimed in any one of claims 1 to 4, characterized in that: The centerless lathe is an MCT-100B external cylindrical centerless lathe. When it is working, the workpiece does not rotate, but the tool rotates, and four tools are evenly arranged in a circle. The cutting depth of the tool is 1.5-2.3mm, and the rotation speed is 210-230r / min; the feed speed of the centerless lathe is 600-700mm / min.

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