A positioning device for grinding of large bore diameter parts

Abstract

The utility model discloses a positioning device for big aperture part excircle grinding belongs to machining technical field. Aiming at big aperture special-shaped part excircle grinding, the traditional integral type positioning mandrel is too heavy to cause operator's high labor intensity, and there is mechanical injury risk, and the problem of influencing processing efficiency and accuracy, and the positioning solution of light weight and high accuracy is provided. The device is combined by welding from positioning cover, cover and positioning shaft, and the positioning cover adopts small taper 1:2000 design, and forms small gap cooperation with part inner hole, the cover is equipped with the heat dissipation hole, and the both ends of positioning shaft are equipped with the center hole for double top clamping, and the whole adopts 20 number steel and eliminates stress after welding heat treatment. The weight is reduced through split type welding structure, and reliable positioning is realized in combination with conical surface static friction, the accuracy requirement of part outer diameter to inner hole runout and tolerance is satisfied, the difficulty of assembly and disassembly is reduced, the security hidden danger is reduced, the batch production efficiency is improved, and is applicable to the excircle grinding of big aperture special-shaped part.

Description

Technical Field

[0001] This utility model relates to the field of machining technology, and in particular to a positioning device for grinding the outer diameter of large-diameter parts. Background Technology

[0002] In the field of machining technology, for the external cylindrical grinding of large-diameter irregularly shaped parts, positioning devices are often required to ensure machining accuracy. For a certain type of large-diameter part (such as an intermediate flange), the runout of the outer diameter at one end relative to the inner hole is required to be no more than 0.02 mm, and the outer diameter tolerance must be controlled within 0.022 mm. Therefore, a cylindrical grinding machine is required for precision grinding.

[0003] In existing machining processes, external cylindrical grinding typically employs an internal mandrel for positioning and two centers for clamping. However, due to the large inner diameter of these parts (e.g., φ80), traditional positioning devices (mandrels) often use an integral structure design to ensure positioning stability, resulting in excessively heavy fixtures. During mass production, operators must load and unload the parts and mandrel together on the external cylindrical grinding machine, significantly increasing labor intensity. Furthermore, the heavy fixtures are prone to collisions during handling and clamping, posing a safety hazard of mechanical injury. Simultaneously, the bulky structure affects clamping efficiency, indirectly restricting the stability of machining accuracy and failing to meet the demands of efficient and safe production. Therefore, it is urgent to optimize the structure of traditional positioning mandrels to solve the series of problems caused by excessive weight. Utility Model Content

[0004] To address the shortcomings of existing technologies, this utility model provides a positioning device for grinding the outer diameter of large-diameter parts. It solves the technical problems of traditional integral positioning mandrels causing high labor intensity for operators, mechanical injury safety hazards, and affecting processing efficiency and accuracy when grinding the outer diameter of large-diameter irregular-shaped parts.

[0005] To achieve the above objectives, this utility model provides the following technical solution:

[0006] A positioning device for grinding the outer diameter of large-diameter parts includes a positioning shaft, a cover, and a positioning sleeve;

[0007] Two covers are provided, which are respectively fitted onto both ends of the positioning shaft and welded to the positioning shaft for fixation;

[0008] The positioning sleeve is fitted onto the outer periphery of the two covers and welded to the covers to form an integrated mandrel structure;

[0009] The outer circle of the positioning sleeve has a small taper structure, which is used to mate with the inner hole of large-diameter parts for positioning.

[0010] The cover has multiple ventilation holes for heat dissipation during the grinding process.

[0011] Preferably, the outer taper of the positioning sleeve is 1:2000, and its small end outer diameter is fitted with the inner hole of the large diameter part with a small clearance, the clearance being 0.01-0.03mm.

[0012] Preferably, the positioning shaft, cover and positioning sleeve are all made of No. 20 steel, and are formed into one piece by welding and then heat-treated to eliminate welding stress.

[0013] Preferably, the cover is an annular plate structure, with its inner diameter interfering with the outer diameter of the positioning shaft and its outer diameter interfering with the inner diameter of the positioning sleeve, forming an axial positioning step after welding.

[0014] Preferably, each of the covers has four heat dissipation holes, which are evenly distributed along the circumference of the cover and have a diameter of 10-15mm, in order to reduce heat accumulation during grinding.

[0015] Preferably, the positioning shaft has a center hole at both ends. The center hole is a 60° conical hole with a protective cone, which is used to cooperate with the center of the external cylindrical grinding machine to achieve axial positioning.

[0016] Preferably, the length of the positioning sleeve is not less than 2 / 3 of the length of the inner hole of the large-diameter part, and the surface roughness of its outer circle is Ra0.8μm to ensure the fitting accuracy with the inner hole of the part.

[0017] Preferably, the outer diameter of the middle part of the positioning shaft is smaller than the outer diameters of both ends, forming a stepped shaft structure to reduce the overall weight. The total length of the positioning shaft is 100-150mm longer than the length of the positioning sleeve to accommodate the heart-shaped chuck.

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

[0019] This invention, through its split-welded structure design, significantly reduces the overall weight of the positioning mandrel, solving the operational difficulties caused by the excessive weight of traditional integral mandrels. In mass production, the lightweight mandrel makes it easier and less strenuous for operators to clamp and disassemble parts, greatly reducing labor intensity and the risk of mechanical injury caused by handling heavy objects, thus improving the safety of the production process.

[0020] Furthermore, through the welding assembly of the positioning sleeve, cover, and positioning shaft, followed by grinding, this device forms a high-precision small-tapered positioning structure. This ensures the fitting accuracy between the inner hole of the part and the mandrel, meeting the runout and tolerance requirements during the grinding of the outer diameter of large-diameter parts, effectively guaranteeing product processing quality. Simultaneously, the heat dissipation hole design on the cover prevents overheating of the parts during grinding. The rationality of the fitting structure further improves processing efficiency and the durability of the device, making it suitable for large-scale production applications. Attached Figure Description

[0021] The above description is only an overview of the technical solution of this utility model. In order to better understand the technical means of this utility model and to implement it in accordance with the contents of the specification, the preferred embodiments of this utility model are described in detail below with reference to the accompanying drawings.

[0022] Figure 1 This is a structural diagram of the present invention.

[0023] Illustration: 1. Positioning shaft; 2. Cover; 3. Positioning sleeve. Detailed Implementation

[0024] This application provides a positioning device for grinding the outer diameter of large-diameter parts, which effectively solves the technical problems of traditional integral positioning mandrels causing high labor intensity for operators, mechanical injury safety hazards, and affecting processing efficiency and accuracy when grinding the outer diameter of large-diameter irregular-shaped parts.

[0025] Example

[0026] like Figure 1 As shown, the overall technical solution in this application embodiment is as follows:

[0027] To address the problems existing in the prior art, this utility model discloses a positioning device for grinding the outer diameter of large-diameter parts. The core components include a positioning shaft 1, a cover 2, and a positioning sleeve 3, which are welded together to form an integrated mandrel structure suitable for machining an intermediate flange with an inner diameter of φ80mm. The parameters and material properties of each component are as follows:

[0028] Positioning axis 1:

[0029] It is machined from No. 20 low-carbon steel bar. The center hole is ground to a surface roughness Ra≤0.8μm, ensuring that the coaxiality error with the grinding machine center is ≤0.005mm. A stepped surface is provided in the middle of the shaft to define the welding position of cover 2.

[0030] Cover 2:

[0031] It is made of No. 20 steel plate by stamping and is interference-fitted with positioning shaft 1. Four φ12mm heat dissipation holes are evenly distributed around the circumference, with the center of the hole 15mm from the outer edge and the included angle between adjacent holes 90°. There are two covers 2, located at both ends of positioning shaft 1.

[0032] Positioning sleeve 3:

[0033] It is machined from No. 20 seamless steel pipe, with the inner hole transition fit with the outer diameter of the cover 2. After grinding, the outer circle is formed with a taper of 1:2000, with a small end diameter of φ79.95mm and a large end diameter of φ80.05mm. The surface roughness Ra≤0.4μm, forming a small clearance fit of 0.01-0.03mm with the inner hole of the middle flange.

[0034] Parts pretreatment:

[0035] Positioning shaft 1: After rough turning, it is heat treated, the outer diameter is precision turned, and the center holes at both ends are drilled and ground.

[0036] Cover 2: After stamping, remove burrs and ream the inner hole to an interference fit of 0.005-0.01mm with the positioning shaft 1.

[0037] Positioning sleeve 3: After the steel pipe is cut, rough machine the inner and outer diameters, leaving a 0.5mm grinding allowance for the inner hole and a 1mm grinding allowance for the outer diameter.

[0038] Welding assembly:

[0039] Heat the two covers 2 to 200℃ (heat fitting), insert them into the positioning shaft 1, and after correcting the perpendicularity of the end face with a dial indicator, perform circumferential welding using argon arc welding.

[0040] Positioning sleeve 3 is fitted into the outer circle of cover 2 to ensure that both end faces are flush with cover 2. Symmetrical segmented welding is used to avoid welding deformation. After welding, it is allowed to cool naturally to room temperature.

[0041] Post-welding treatment:

[0042] Stress relief heat treatment: Place the mandrel as a whole into a box furnace, heat it to 600℃±10℃, hold it for 2 hours, and then cool it down to below 200℃ in the furnace to ensure that the welding stress relief rate is ≥80%.

[0043] Calibration and finishing: Check the straightness of the mandrel (≤0.02mm / m). If it exceeds the tolerance, use pressure correction; grind the center holes at both ends to remove oxide scale.

[0044] Final grinding:

[0045] Using the center holes at both ends as a reference, clamp the two centers on the cylindrical grinding machine and grind the outer circle of the positioning sleeve 3 to a taper of 1:2000.

[0046] The grinding process consists of three feeds: rough grinding (leaving a 0.1mm allowance), semi-finish grinding (leaving a 0.03mm allowance), and finish grinding (to reach the final size). During finish grinding, emulsion cooling (5% concentration) is used, the grinding wheel linear speed is 35m / s, and the feed rate is 0.01mm / revolution.

[0047] Final inspection: Use a taper gauge to check taper compliance (contact rate ≥80%), a micrometer to measure diameter error (≤0.005mm), and a dial indicator to check radial runout (≤0.003mm).

[0048] Parts grinding operation procedure:

[0049] Clamping preparation:

[0050] Clean the inner hole of the intermediate flange, remove burrs and iron filings, and wipe it clean with a cotton cloth soaked in alcohol.

[0051] Apply a thin layer of machine oil to the outer circle of the mandrel. Hold the large end of the mandrel and align the small end with the inner hole of the flange. Gently tap the large end face of the mandrel with a nylon rod until the length of the mandrel that fits against the flange is about 75% of the total length of the positioning sleeve 3.

[0052] Check the tightness of the fit: rotate the flange with both hands and feel for any looseness; use a dial indicator to check the perpendicularity of the flange end face to the mandrel axis.

[0053] Grinding machine clamping:

[0054] Install the self-made chicken heart chuck on the left end of positioning shaft 1, tighten the M8 fastening bolt, and ensure that there is no relative rotation between the chuck and the mandrel.

[0055] Place the center hole at the left end of the mandrel on the center of the grinding machine spindle, and the center hole at the right end on the center of the tailstock. Adjust the tailstock sleeve extension (≤100mm).

[0056] Rotate the mandrel so that the chuck jaws engage with the grinding machine spindle chuck lever. Manually rotate the spindle to confirm that there is no jamming. At this point, the axial positioning of the mandrel is complete.

[0057] This positioning device achieves high-precision positioning and lightweight operation in the external cylindrical grinding of large-diameter parts through the synergistic effect of a split-type welded structure design and small-tapered static friction positioning. The specific principle is as follows:

[0058] The locating sleeve 3 has a tapered fit with the inner hole of the part: the outer diameter of the locating sleeve 3 is designed with a small taper of 1:2000, which allows for a small clearance fit with the inner hole of large-diameter parts (such as intermediate flanges). When the inner hole of the part is fitted into the locating sleeve 3, the end face of the part is tapped with a nylon rod to gradually bring the tapered surfaces into contact. The static friction generated by the contact of the tapered surfaces achieves radial self-locking, ensuring that there is no relative sliding between the part and the locating sleeve 3. This structure replaces the traditional interference fit, avoiding part deformation caused by hard contact, and automatically aligning through tapered guidance, ensuring that the coaxiality between the inner hole of the part and the locating sleeve 3 is ≤0.01mm.

[0059] Positioning shaft 1 is located by two centers: Standard center holes are machined at both ends of positioning shaft 1. During assembly, it is tightened by the two centers of the grinding machine, so that the axis of positioning shaft 1 is completely aligned with the axis of the grinding machine spindle. Since positioning sleeve 3, cover 2 and positioning shaft 1 are fixed together by welding, the coaxiality error between the axis of positioning sleeve 3 and the axis of positioning shaft 1 is ≤0.005mm, thereby ensuring that the inner hole of the part is indirectly coaxial with the grinding machine spindle through positioning sleeve 3, meeting the accuracy requirements.

[0060] Traditional integral mandrels use a solid structure and weigh approximately 15kg. This device disassembles the mandrel into positioning sleeve 3, cover 2, and positioning shaft 1, and reduces the overall weight after welding assembly. The split design reduces material redundancy, and the choice of No. 20 steel ensures strength while reducing the overall weight, allowing the operator to lift and unload with one hand.

[0061] Welding stress control: Argon arc welding is used to weld the positioning sleeve 3 to the cover 2 and the cover 2 to the positioning shaft 1. After welding, stress relief annealing is performed to avoid deformation of the outer diameter of the positioning sleeve 3 due to stress release and to ensure the accuracy of the conical surface fit.

[0062] Heat dissipation function of cover 2: Cover 2 has 4 through holes around its circumference. During grinding, the high-speed rotating parts drive air to flow through the through holes, forming convection heat dissipation and avoiding dimensional accuracy deviations caused by thermal deformation.

[0063] Finally, it should be noted that the above embodiments are merely examples for clearly illustrating the present invention and are not intended to limit the implementation. Those skilled in the art can make other variations or modifications based on the above description. It is neither necessary nor possible to exhaustively list all possible implementations. However, obvious variations or modifications derived therefrom are still within the protection scope of this invention.

Claims

1. A positioning device for external cylindrical grinding of large-diameter parts, characterized in that, It includes a positioning shaft (1), a cover (2), and a positioning sleeve (3); There are two covers (2), which are respectively fitted onto the two ends of the positioning shaft (1) and welded to the positioning shaft (1); The positioning sleeve (3) is fitted onto the outer periphery of the two covers (2) and welded to the covers (2) to form an integrated mandrel structure; The outer circle of the positioning sleeve (3) has a small taper structure, which is used to mate with the inner hole of a large-diameter part for positioning. The cover (2) has multiple heat dissipation holes for heat dissipation during the grinding process.

2. The positioning device for external cylindrical grinding of large-diameter parts as described in claim 1, characterized in that: The outer taper of the positioning sleeve (3) is 1:2000. Its small end outer diameter and the inner hole of the large diameter part are fitted with a small clearance, with a fit clearance of 0.01-0.03mm.

3. The positioning device for external cylindrical grinding of large-diameter parts as described in claim 1, characterized in that: The positioning shaft (1), cover (2) and positioning sleeve (3) are all made of No. 20 steel. They are welded together and then heat-treated to eliminate welding stress.

4. A positioning device for external cylindrical grinding of large-diameter parts as described in claim 1, characterized in that: The cover (2) is an annular plate structure. Its inner diameter is interference-fitted with the outer diameter of the positioning shaft (1), and its outer diameter is interference-fitted with the inner diameter of the positioning sleeve (3). After welding, it forms an axial positioning step.

5. A positioning device for external cylindrical grinding of large-diameter parts as described in claim 1, characterized in that: Each of the covers (2) has four heat dissipation holes, which are evenly distributed along the circumference of the cover (2) and have a diameter of 10-15 mm, in order to reduce heat accumulation during grinding.

6. A positioning device for external cylindrical grinding of large-diameter parts as described in claim 1, characterized in that: The positioning shaft (1) has a center hole at both ends. The center hole is a 60° conical hole with a protective cone, which is used to cooperate with the center of the external cylindrical grinding machine to achieve axial positioning.

7. A positioning device for external cylindrical grinding of large-diameter parts as described in claim 1, characterized in that: The length of the positioning sleeve (3) is not less than 2 / 3 of the length of the inner hole of the large-diameter part, and the surface roughness of its outer circle is Ra0.8μm to ensure the fitting accuracy with the inner hole of the part.

8. A positioning device for external cylindrical grinding of large-diameter parts as described in claim 1, characterized in that: The outer diameter of the middle part of the positioning shaft (1) is smaller than the outer diameters at both ends, forming a stepped shaft structure to reduce the overall weight. The total length of the positioning shaft (1) is 100-150mm longer than the length of the positioning sleeve (3) so as to clamp the heart-shaped chuck.

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