A positioning and clamping method for turning a thin-walled metal shell

Abstract

A positioning and clamping method for turning a thin-walled metal shell, wherein a process ring is fixed on a lathe center frame and is not removed, so that the process ring always maintains a coaxial state with the center axis of the lathe, and the workpiece is self-centered at both ends by using a lathe three-jaw self-centering chuck and a tail top tooling of the lathe, so that the axis of the workpiece and the center axis of the lathe are also in a coaxial state, and the workpiece is fixed by the process ring to complete the positioning and clamping of the workpiece, thereby changing the process of using a four-jaw chuck to align the two ends of the workpiece, align the process ring, turn the process ring and support the center frame in each clamping, and using the tail top tooling, the three-jaw self-centering chuck and the process ring to realize rapid positioning and clamping of the workpiece, and the clamping time is reduced from more than 30 minutes to 5 minutes, thereby effectively simplifying the product clamping and alignment process, reducing auxiliary time such as clamping and alignment in the process of group turning of workpieces, and improving equipment utilization.

Description

Technical Field

[0001] The invention relates to the mechanical processing industry, in particular to a rapid positioning clamping method and a tooling for machining a thin-walled metal shell. Background Art

[0002] With the continuous development of my country's aviation and aerospace industries, the demand for military products is increasing. Improving production efficiency has become a common goal pursued by all military industries. Taking a thin-walled metal shell as an example, Figure 1 As shown in the figure, the workpiece is welded by the front joint, the rear joint and the thin-walled cylinder. The axes of the front joint, the rear joint and the thin-walled cylinder are in the same straight line. The turning process of this workpiece mainly includes two clamping and alignment of the front and rear ends of the workpiece and two lathe processes. The inner and outer surfaces of the front joint and the rear joint of the workpiece are respectively lathe-machined. During the processing, the spindle chuck is used to clamp the joint at one end of the workpiece, and the joint at the other end of the workpiece is machined. In order to avoid machining interference, the thin-walled cylinder near the workpiece joint needs to be clamped and supported. Since the wall thickness of the workpiece cylinder is thin and the rigidity is poor, it cannot directly support the lathe center frame. It is necessary to install a process ring on the thin-walled cylinder of the workpiece, and then use the lathe center frame to indirectly support the thin-walled cylinder of the workpiece. However, one of the most important factors affecting the machining efficiency of the workpiece is that the clamping and alignment process of the workpiece before each lathe process (including the process of installing and adjusting the process ring) is relatively cumbersome. Each clamping and alignment of the workpiece takes more than 30 minutes, which seriously affects the utilization rate of production equipment and the machining efficiency of the workpiece.

[0003] The existing clamping and alignment method of the workpiece is as follows Figure 2 As shown, take the joint after machining as an example:

[0004] The first step is to prepare the tooling. First, put the process ring on the workpiece, and use the process ring clamping screws to initially fix the process ring tooling on the workpiece;

[0005] The second step is to preliminarily clamp the workpiece. The workpiece with the process ring fixture is hoisted between the lathe spindle and the tailstock by the overhead crane, and the workpiece is placed within the range of the lathe center frame. The four-jaw chuck of the lathe spindle is used to lightly clamp the outer circle of the front joint of the workpiece, and the four-jaw chuck of the lathe tailstock is used to lightly tighten the inner hole of the rear joint;

[0006] The third step is to roughly align the circular runout of the front joint of the workpiece. Place a dial indicator near the spindle, align the probe with the outer circle of the front joint of the workpiece, manually rotate the workpiece and adjust the four jaws of the spindle four-jaw chuck until the circular runout of the dial indicator is less than 0.5mm;

[0007] Step 4: Roughly align the circular jump of the rear joint of the workpiece. Place a dial indicator near the tailstock, align the probe with the outer circle of the rear joint of the workpiece, manually rotate the workpiece and adjust the four jaws of the tailstock four-jaw chuck until the circular jump of the dial indicator is less than 0.5mm;

[0008] Step 5: Accurately find the circular jump of the front joint of the workpiece. Manually rotate the workpiece and adjust the four jaws of the manual four-jaw chuck of the spindle until the circular jump of the dial indicator is less than 0.05mm;

[0009] Step 6: Precisely find the circular jump of the rear joint of the workpiece. Manually rotate the workpiece and adjust the four jaws of the tailstock four-jaw chuck until the circular jump of the dial indicator is less than 0.05mm;

[0010] Step 7: Clamp both ends of the workpiece. Manually clamp the four-jaw chuck at the spindle end and the four-jaw chuck at the tailstock end in sequence;

[0011] Step 8: Adjust the process ring. Place the dial indicator so that the probe is aligned with the maximum outer circle of the process ring, manually rotate the workpiece, and manually adjust the clamping screws of the process ring one by one and multiple times until the runout of the maximum outer circle of the process ring is less than 0.1mm;

[0012] The ninth step is to turn the largest outer circle of the processing ring to light.

[0013] Step 10: Support the center frame. Push the center frame to the process ring and adjust the three support rods of the center frame to support the largest outer circle of the process ring.

[0014] The eleventh step is to loosen the four-jaw chuck of the tailstock that holds the rear joint of the workpiece and move the tailstock away. The clamping and alignment of the workpiece is now completed and the turning of the rear joint of the workpiece can begin.

[0015] Step 12: After the processing is completed, the four-jaw chuck of the main spindle and the center frame support rod need to be loosened, the workpiece is removed, and then the process ring on the workpiece is removed. When clamping the next workpiece, the first to eleventh steps need to be repeated.

[0016] There are three main disadvantages of the existing clamping and alignment methods: 1. The process of workpiece clamping and alignment is relatively cumbersome. Each clamping requires not only repeated calibration of the circular runout at both ends of the workpiece, but also calibration of all the top blocks of the process ring. The entire clamping and alignment process is time-consuming, which seriously affects the processing efficiency of the workpiece and the utilization rate of the equipment; 2. The four jaws of the four-jaw chuck installed on the spindle and the tailstock are movable separately. When adjusted manually, it is easy to cause uneven force on the workpiece, causing deformation of the workpiece, thereby affecting the processing quality; 3. The maximum outer circle of the process ring must be machined once for each clamping. After processing multiple workpieces, the clamping ribs of the outer circle of the process ring will be consumed and cannot be used any longer. A new process ring needs to be replaced, and the production cost is high.

[0017] The process ring is disclosed in the invention with publication number CN107414519A, which is a combined tooling for clamping thin-walled shells. A plurality of top blocks are respectively installed at both ends of the process ring. The inner and outer surfaces of the top blocks are both cambered surfaces. When the clamping ribs are consumed to the point that the tooling cannot be used normally, the remaining parts of the original clamping ribs are turned off and replaced with new clamping ribs to achieve the repair of the combined tooling for clamping thin-walled shells.

[0018] When the process ring is used according to the prior art, all the top blocks of the process ring need to be adjusted each time it is clamped, and the maximum outer circle of the process ring needs to be turned once each time. This not only makes the clamping and alignment process of the workpiece cumbersome and time-consuming, affecting the workpiece processing efficiency, but the processing process will also cause consumption to the process ring. Summary of the invention

[0019] In order to overcome the shortcomings of the prior art, such as complicated operation, long time consumption, influence on processing efficiency and tooling consumption, the present invention proposes a positioning and clamping method for turning a thin-walled metal shell.

[0020] The specific process of the present invention is:

[0021] Step 1, prepare the tooling:

[0022] A three-jaw self-centering chuck and an external support jaw are installed at the spindle end of the lathe; a tail top tooling is installed in a tapered sleeve of the tailstock of the lathe, and the tail top tooling is installed and positioned by the cooperation between the inner and outer surfaces of the tapered sleeve and the outer surface of the tapered handle of the tail top tooling.

[0023] A process ring is mounted on the cylinder of the rear joint of the workpiece; the clamping screw of the process ring is adjusted so that more than three pressure blocks on the process ring are respectively fitted with the outer circumferential surface of the workpiece to achieve preliminary fixation of the process ring and the workpiece.

[0024] Step 2: Positioning and clamping of the workpiece:

[0025] The workpiece is hoisted between the three-jaw self-centering chuck and the tail top tooling of the lathe. The large conical surface of the tail top tooling is used to press the inner hole of the rear joint of the workpiece; the outer claw surface of the outer support claw of the three-jaw self-centering chuck of the lathe spindle is used to press the inner surface of the front joint of the workpiece.

[0026] Step 3, adjust the process ring:

[0027] The specific process of adjusting the process ring is:

[0028] Use the dial indicator to find the highest point and the lowest point on the outer circumferential surface of the process ring; calculate the height difference h between the highest point and the lowest point. Adjust the two clamping screws on both sides of the highest point of the process ring to reduce the pressing amount of each top block by 0.5h; at the same time, adjust the two clamping screws on both sides of the lowest point of the process ring to increase the pressing amount by 0.5h; complete the first adjustment of the outer circumferential surface of the process ring.

[0029] Use the dial indicator to find the highest point and the lowest point of the outer circumferential surface of the adjusted process ring; obtain the new highest point and the new lowest point; calculate the height difference h1 between the new highest point and the new lowest point. Adjust the clamping screws on both sides of the highest point of the process ring to reduce the pressing amount of each clamping screw by 0.5h1; adjust the two clamping screws on both sides of the lowest point of the process ring to increase the pressing amount by 0.5h1; complete the second adjustment of the outer circumferential surface of the process ring.

[0030] Repeat the second adjustment process of the outer circumferential surface of the process ring until the difference between the highest point and the lowest point is n ≤0.1mm, so that all the top blocks of the process ring are pressed tightly against the outer surface of the workpiece.

[0031] Step 4, turning the process ring:

[0032] The lathe process makes the largest outer circle of the process ring visible.

[0033] Step 5, Support the center frame:

[0034] The center frame is moved to the process ring, and the three support rods of the center frame are respectively supported against the largest outer circle of the process ring to fix the process ring on the center frame.

[0035] Step 6, remove the workpiece and keep the process ring on the center frame of the lathe:

[0036] Loosen the clamping screws and the top block of the process ring; loosen the outer support claws of the spindle three-jaw self-centering chuck, and move the lathe tailstock backward, and drive the tailstock tooling to move backward; remove the workpiece, keep the process ring on the lathe center frame, and keep the process ring in the aligned state so that the axis center of the outer circle of the process ring will always be coaxial with the axis center of the lathe.

[0037] This completes the adjustment of the tooling.

[0038] There is no need to perform the above tooling adjustment operations during the subsequent clamping and processing of the same workpiece.

[0039] Step 7: Workpiece lifting, positioning and clamping:

[0040] Lift the workpiece to be processed between the three-jaw self-centering chuck and the tail top fixture of the lathe, and pass the workpiece through the process ring on the center frame of the lathe. Tighten the two ends of the workpiece respectively by the three-jaw self-centering chuck and the tail top fixture. Specifically, control the sleeve of the lathe tailstock to extend forward so that the conical surface of the large flat-top cone of the tail top fixture presses against the rear joint of the workpiece, and the end face of the front joint of the workpiece contacts the end face of the claw self-centering chuck. Twist the three-jaw self-centering chuck so that the outer support claws tighten the inner hole of the front joint of the workpiece. Turn all the clamping screws on the process ring clockwise so that all the top blocks of the process ring contact the cylindrical surface of the workpiece, and then turn each clamping screw half a turn clockwise in turn to tighten all the top blocks evenly.

[0041] Step 8, remove the tail top tooling:

[0042] Control the lathe tailstock to move backwards so that the tailstock tooling leaves the end face of the product, thus completing the clamping and alignment of the workpiece. Start turning the rear joint of the workpiece.

[0043] After the workpiece is turned, the clamping screws of the process ring are loosened, the outer support jaws of the three-jaw self-centering chuck of the spindle are loosened, the tail top tooling is retreated, the workpiece is removed, and the process ring continues to remain on the center frame of the lathe.

[0044] When clamping the next workpiece of the same type, it is only necessary to repeat steps 7 and 8.

[0045] The tail top tooling proposed in the present invention comprises a stepped cone, a tapered shank and a ball bearing. The tapered shank is installed at the center of the end face of the large diameter end of the stepped cone through the ball bearing. The ball bearing is installed in the blind hole of the stepped cone in a small interference fit manner, and the outer end face of the ball bearing is flush with the large end face of the stepped cone.

[0046] The step cone is in the shape of a double-layer conical disc, and its appearance is a convex letter shape. The top surface diameter of the small conical disc is smaller than the inner diameter d of the small end portion of the workpiece, and the bottom surface diameter is larger than d. When the small end of the workpiece is pressed tightly with a tail-lift tooling, the inner hole mouth of the small end of the workpiece is clamped on the outer cone surface of the small conical disc to achieve self-centering of the small end of the workpiece; the top surface diameter of the large conical disc is smaller than the inner diameter D of the large end portion of the workpiece, and the bottom surface diameter is larger than D. When the large end of the workpiece is pressed tightly with a tail-lift tooling, the inner hole mouth of the large end of the workpiece is clamped on the outer cone surface of the large conical disc to achieve self-centering of the large end of the workpiece.

[0047] The present invention uses a tail top tooling, a three-jaw self-centering chuck and a process ring to realize rapid positioning and clamping of the workpiece, and the clamping time is reduced from more than 30 minutes to 5 minutes. During the clamping process, there is no need to calibrate the two ends of the workpiece, nor is there any need to turn the outer circle of the process ring, which greatly simplifies the product clamping and alignment process, reduces auxiliary time such as clamping and alignment during the workpiece group turning process, and improves the purpose of equipment utilization.

[0048] The present invention can ensure stable installation of the product and uniform force during clamping and alignment, and small deformation during the processing process, and can ensure the processing accuracy of the thin-walled shell, and can complete the rapid positioning and clamping of the thin-walled shell without damaging the shell.

[0049] In the clamping method of the present invention, after the adjustment of the tooling is completed in the preparation operation, the process ring is fixed on the lathe center frame and is not removed, so that the process ring always remains coaxial with the lathe center axis, and the workpiece uses the lathe three-jaw self-centering chuck and the tail top tooling to achieve self-centering at both ends of the workpiece. At this time, the axis of the workpiece and the lathe center axis are also in a coaxial state, and then only the clamping screw of the process ring needs to be tightened so that the top block of the process ring is pressed on the surface of the workpiece to complete the positioning and clamping of the workpiece. The above operation eliminates the need to use the four-jaw chuck to manually align the two ends of the workpiece, align the process ring, turn the process ring, support the center frame, etc. during each clamping process.

[0050] Compared with the prior art, the present invention has the following beneficial effects:

[0051] 1. Simple clamping and convenient operation. Using the clamping and positioning method and tooling of the present invention, for the same workpiece, only one tooling preparation operation is required, and the subsequent workpiece clamping operation is simple and convenient, without the need for repeated metering and tooling adjustment, thus simplifying the clamping and alignment process.

[0052] 2. Improved production efficiency. When the clamping and positioning method and tooling of the present invention are used, the time spent on clamping and alignment is greatly reduced, which can effectively increase the time the equipment is used for processing, significantly improve equipment utilization and production efficiency, and facilitate group processing of products.

[0053] 3. It is applicable to a variety of products. The clamping and positioning method and tooling of the present invention can be used not only Figure 1 The clamping and positioning of workpieces can also be used for other types of products that require clamping using process rings.

[0054] Comparison table of operation steps and time consumption between the prior art and the present invention

[0055]

[0056] BRIEF DESCRIPTION OF THE DRAWINGS

[0057] Figure 1 Workpiece structure diagram.

[0058] Figure 2 Schematic diagram of the clamping and alignment method of the prior art; wherein, Figure 2 a is the main view, Figure 2 b is Figure 2 AA section view in a.

[0059] Figure 3 is a schematic diagram of a stepped cone; where Figure 3 a is Figure 3 AA section view in b, Figure 3 b is the main view.

[0060] Figure 4 is a schematic diagram of the cone handle; Figure 4 a is the main view, Figure 4 b is Figure 4 Right view of a.

[0061] Figure 5 It is a schematic diagram of the tail top tooling assembly.

[0062] Figure 6 It is a structural schematic diagram of the present invention.

[0063] Figure 7 It is a schematic diagram of the clamping and positioning method of the present invention.

[0064] Figure 8 It is a flow chart of the present invention.

[0065] In the figure: 1. Step cone; 2. Taper shank; 3. Ball bearing; 4. Tail top tooling; 5. Process ring; 6. Three-jaw self-centering chuck; 7. Center frame; 8. Workpiece. DETAILED DESCRIPTION

[0066] This embodiment is a positioning and clamping method for lathe processing of a thin-walled metal shell. The specific process is:

[0067] Step 1, prepare the tooling:

[0068] A three-jaw self-centering chuck 6 and an external support jaw are installed at the spindle end of the lathe, and the external support circle diameter of the three external support jaws is 105 mm. The external support circle is machined to a diameter of 100 mm. A conical tail top tool 4 is installed in the conical sleeve of the lathe tailstock, and the tail top tool is installed and positioned by the cooperation between the inner surface of the conical sleeve of the tailstock and the outer surface of the conical handle of the tail top tool.

[0069] A process ring is mounted on the cylinder at the rear joint of the workpiece 8; the clamping screws on the process ring are adjusted so that the pressure blocks on the process ring fit the outer circumferential surface of the workpiece respectively, thereby achieving preliminary fixation of the process ring and the workpiece.

[0070] Step 2: Positioning and clamping of the workpiece:

[0071] The workpiece 8 is hoisted between the lathe three-jaw self-centering chuck and the tail top fixture. The large conical surface of the tail top fixture 4 is used to press the inner surface of the rear joint of the workpiece; the outer claw surface of the outer support claw of the lathe spindle three-jaw self-centering chuck is used to press the inner hole of the front joint of the workpiece.

[0072] Step 3, adjust the process ring:

[0073] The specific process of adjusting the process ring is:

[0074] Use the dial indicator to align the probe with the maximum outer circle of the process ring, manually rotate the workpiece one circle, find the highest point and the lowest point on the outer circumference of the process ring, and calculate the height difference h between the highest point and the lowest point. Adjust the clamping screws on both sides of the highest point of the process ring to reduce the pressing amount of each clamping screw by 0.5h; at the same time, adjust the two clamping screws near the lowest point of the process ring to increase the pressing amount by 0.5h. Complete the first adjustment of the outer circumference of the process ring.

[0075] Use the dial indicator to find the highest point and the lowest point of the outer circumferential surface of the adjusted process ring; obtain the new highest point and the new lowest point; calculate the height difference h1 between the new highest point and the new lowest point. Adjust the clamping screws on both sides of the highest point of the process ring to reduce the pressing amount of each clamping screw by 0.5h1; adjust the two clamping screws on both sides of the lowest point of the process ring to increase the pressing amount by 0.5h1; complete the second adjustment of the outer circumferential surface of the process ring.

[0076] Repeat the second adjustment process of the outer circumferential surface of the process ring until the difference between the highest point and the lowest point is n ≤0.1mm, and all the top blocks of the process ring are pressed tightly on the workpiece, and all the top blocks of the process ring are pressed tightly on the outer surface of the workpiece.

[0077] Step 4, turning the process ring:

[0078] The lathe process makes the largest outer circle of the process ring visible.

[0079] Step 5, Support the center frame:

[0080] Push the center frame 7 to the process ring, adjust the three support rods of the center frame to support the maximum outer circle of the process ring, and fix the process ring on the center frame;

[0081] Step 6, remove the workpiece, keeping the process ring on the center stand:

[0082] Loosen the clamping screws and top block of the process ring, loosen the outer support claws of the spindle three-jaw self-centering chuck, and operate the lathe tailstock to move back, driving the tailstock tooling 4 to move back; remove the workpiece, but leave the process ring on the center frame of the lathe. From then on, the process ring will always remain in the aligned state, and the axis center of the outer circle of the process ring will always be coaxial with the axis center of the lathe.

[0083] This completes the adjustment of the tooling.

[0084] There is no need to perform the above tooling adjustment operations during the subsequent clamping and processing of the same workpiece.

[0085] Step 7: Workpiece lifting, positioning and clamping:

[0086] Lift the workpiece to be processed between the three-jaw self-centering chuck and the tail top fixture 4 of the lathe, and pass the workpiece through the process ring on the center frame of the lathe. Control the sleeve of the lathe tailstock to extend forward so that the conical surface of the large flat-top cone of the tail top fixture presses against the rear joint of the workpiece, and the end face of the front joint of the workpiece contacts the end face of the claw self-centering chuck. Twist the three-jaw self-centering chuck so that the outer support claws tighten the inner hole of the front joint of the workpiece. Turn all the clamping screws on the process ring clockwise so that all the top blocks of the process ring contact the cylindrical surface of the workpiece, and then turn each clamping screw clockwise half a turn in turn to evenly tighten all the top blocks.

[0087] Step 8, remove the tail top tooling:

[0088] The tailstock moves backwards so that the tailstock tooling leaves the end face of the rear joint of the workpiece. At this point, the clamping and alignment of the workpiece is completed, and the turning of the rear joint of the workpiece begins.

[0089] After the workpiece is turned, loosen the clamping screw of the process ring, loosen the outer support jaws of the spindle three-jaw self-centering chuck, retract the tail top tooling, remove the workpiece, and keep the process ring on the center frame of the lathe.

[0090] When clamping the next workpiece of the same type, it is only necessary to repeat steps 7 and 8.

[0091] In the positioning clamping of the machining of a thin-walled metal shell, this embodiment also proposes a tail top tooling for the machining positioning of a thin-walled metal shell, comprising a step cone 1, a taper shank 2 and a ball bearing 3. The taper shank 2 is installed at the center of the end face of the large diameter end of the step cone through a ball bearing. The ball bearing is installed in the blind hole of the step cone in a small interference fit manner, and the outer end face of the ball bearing 3 is flush with the large end face of the step cone 1.

[0092] The step cone 1 is in the shape of a double-layer conical disc, made of 45# round steel in a quenched and tempered state, and has a convex shape. The top surface diameter of the small conical disc is smaller than the inner diameter d of the small end portion of the workpiece, and the bottom surface diameter is larger than d. When the small end of the workpiece is pressed tightly with a tail-lift tooling, the inner hole mouth of the small end of the workpiece is clamped on the outer cone surface of the small conical disc to achieve self-centering of the small end of the workpiece; the top surface diameter of the large conical disc is smaller than the inner diameter D of the large end portion of the workpiece, and the bottom surface diameter is larger than D. When the large end of the workpiece is pressed tightly with a tail-lift tooling, the inner hole mouth of the large end of the workpiece is clamped on the outer cone surface of the large conical disc to achieve self-centering of the large end of the workpiece.

Claims

1. A positioning and clamping method for machining a thin-walled metal shell, characterized in that: The specific process is: Step 1, prepare the tooling: A process ring is mounted on the cylinder of the rear joint of the workpiece; the clamping screws on the process ring are adjusted so that more than three clamping blocks on the process ring are respectively fitted with the outer circumferential surface of the workpiece, so that the process ring and the workpiece are initially fixed; Step 2: Positioning and clamping of the workpiece: Step 3, adjust the process ring: The specific process of adjusting the process ring is: Find the highest point and the lowest point of the outer circumferential surface of the process ring by using a dial indicator; calculate the height difference h between the highest point and the lowest point; adjust the two clamping screws on both sides of the highest point of the process ring to reduce the pressing amount of each top block by 0.5h; at the same time, adjust the two clamping screws on both sides of the lowest point of the process ring to increase the pressing amount by 0.5h; complete the first adjustment of the outer circumferential surface of the process ring; Use the dial indicator to find the highest point and the lowest point on the outer circumferential surface of the adjusted process ring; obtain the new highest point and the new lowest point; Calculate the height difference h1 between the new highest point and the new lowest point; adjust the clamping screws on both sides of the highest point of the process ring to reduce the pressing amount of each clamping screw by 0.5h1; adjust the two clamping screws on both sides of the lowest point of the process ring to increase the pressing amount by 0.5h1; complete the second adjustment of the outer circumferential surface of the process ring; Repeat the second adjustment process of the outer circumferential surface of the process ring until the difference between the highest point and the lowest point is n ≤0.1mm, so that all top blocks of the process ring are pressed tightly against the outer surface of the workpiece; Step 4, turning the process ring: The lathe process makes the maximum outer circle of the process ring visible; Step 5, Support the center frame: Step 6, remove the workpiece and keep the process ring on the lathe center frame: Remove the workpiece and keep the process ring on the center frame of the lathe so that the axis of the outer circle of the process ring will always be coaxial with the axis of the lathe. At this point, the adjustment of the tooling is completed; Step 7, positioning and clamping of the workpiece: The workpiece to be processed is hoisted between the three-jaw self-centering chuck and the tail top tooling of the lathe, and the workpiece is passed through the process ring on the center frame of the lathe; the two ends of the workpiece are respectively tightened by the three-jaw self-centering chuck and the tail top tooling; specifically, the sleeve of the lathe tailstock is controlled to extend forward so that the conical surface of the large flat-top cone of the tail top tooling presses the rear joint of the workpiece, and the end surface of the front joint of the workpiece contacts the end surface of the three-jaw self-centering chuck; the three-jaw self-centering chuck is twisted so that the outer support jaws tighten the inner hole of the front joint of the workpiece; Turn all the clamping screws on the process ring clockwise to make all the top blocks of the process ring contact the cylindrical surface of the workpiece, and then turn each clamping screw clockwise half a turn to make all the top blocks evenly compressed; Step 8, remove the tail top tooling: Control the lathe tailstock to move backwards so that the tailstock tooling leaves the end face of the product, thus completing the clamping and alignment of the workpiece; start the lathe processing of the rear joint of the workpiece; After the workpiece is machined, the clamping screws of the process ring are loosened, the outer support jaws of the three-jaw self-centering chuck of the main spindle are loosened, the tail top tooling is retreated, the workpiece is removed, and the process ring is kept on the center frame of the lathe; When clamping the next workpiece of the same type, it is only necessary to repeat steps 7 and 8.

2. The positioning and clamping method for machining a thin-walled metal shell according to claim 1, characterized in that: A three-jaw self-centering chuck and an external support jaw are installed at the spindle end of the lathe; a tail top tooling is installed in a tapered sleeve of the tailstock of the lathe, and the tail top tooling is installed and positioned by the cooperation between the inner and outer surfaces of the tapered sleeve and the outer surface of the tapered handle of the tail top tooling.

3. The positioning and clamping method for machining a thin-walled metal shell according to claim 1, characterized in that: The workpiece is lifted between the three-jaw self-centering chuck and the tail top tooling of the lathe; the large conical surface of the tail top tooling is used to press the inner hole mouth of the rear joint of the workpiece; the outer claw surface of the outer support claw of the three-jaw self-centering chuck of the lathe spindle is used to press the inner surface of the front joint of the workpiece.

4. The positioning and clamping method for machining a thin-walled metal shell according to claim 1, characterized in that: The center frame is moved to the process ring, and the three support rods of the center frame are respectively supported against the largest outer circle of the process ring to fix the process ring on the center frame.

5. The positioning and clamping method for machining a thin-walled metal shell according to claim 1, characterized in that: When removing the workpiece in step 6, loosen the clamping screw and the top block of the process ring; loosen the outer support claw of the three-jaw self-centering chuck of the spindle, and move the tailstock of the lathe backward, and drive the tailstock tooling backward; Remove the workpiece, keep the process ring on the center frame of the lathe, and keep the process ring in the state after alignment; There is no need to perform the above tooling adjustment operations during the subsequent clamping and processing of the same workpiece.

6. The positioning and clamping method for machining a thin-walled metal shell according to claim 1, characterized in that: The tail top tooling includes a step cone, a tapered shank and a ball bearing; wherein the tapered shank is installed at the center of the large diameter end face of the step cone through the ball bearing; the ball bearing is installed in the blind hole of the step cone in a small interference fit manner, and the outer end face of the ball bearing is flush with the large end face of the step cone.

7. The positioning and clamping method for machining a thin-walled metal shell according to claim 6, characterized in that: The step cone is in the shape of a double-layer conical disc, and its appearance is a convex shape. The top surface diameter of the small conical disc is smaller than the inner diameter d of the small end portion of the workpiece, and the bottom surface diameter is larger than the inner diameter d of the small end portion. When the small end of the workpiece is pressed tightly with a tail-lift tooling, the inner hole mouth of the small end of the workpiece is clamped on the outer cone surface of the small conical disc to achieve self-centering of the small end of the workpiece; the top surface diameter of the large conical disc is smaller than the inner diameter D of the large end portion of the workpiece, and the bottom surface diameter is larger than the inner diameter D of the large end portion of the workpiece. When the large end of the workpiece is pressed tightly with a tail-lift tooling, the inner hole mouth of the large end of the workpiece is clamped on the outer cone surface of the large conical disc to achieve self-centering of the large end of the workpiece.

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