Method for Preventing Chip Coiling during the Turning Process of PTFE Bellows

Abstract

The present invention discloses a method for preventing chip curling during the turning process of PTFE bellows. When a lathe turns a PTFE rod, the generated chips are difficult to break. If the flow of continuous chips is not effectively controlled, it will cause chip curling, thereby affecting the quality of the machined surface and accelerating the wear of the tool. The chip curling prevention device of the present invention includes a vision detection camera, an air nozzle, an air supply machine, a V-shaped cover, a vacuum generator, a linear module, and a chip suction and pressure module. The present invention adopts a mode of high-pressure chip blowing, negative-pressure chip suction combined with double-roller brush chip pressing to solve the problem of difficult processing of PTFE bellows caused by chip curling, and constructs a chip flow model to describe the change form of the chip outflow state, providing a reference for the setting of the device working parameters.

Description

Technical Field

[0001] The present invention relates to the field of machining of polymer materials, and particularly to a chip curling prevention device and a chip curling prevention method during the turning process of a PTFE bellows. Background Art

[0002] Polytetrafluoroethylene (PTFE) is a high molecular compound obtained by polymerizing monomer tetrafluoroethylene, and has excellent physical and chemical properties. It has a low coefficient of friction, is not easy to adhere to other substances, and has high lubricity. It is often used to make pump parts, pipes, valves, etc., and is widely used.

[0003] As a typical representative of PTFE ultra-clean fluid control components, the PTFE bellows is the core component of the ultra-clean immersion system. In daily machining, due to the high hardness and strength of metal materials, it is suitable to promote chip breaking by setting chip breaking grooves on the tool, regulating the feed rate and cutting speed, spraying cutting fluid, etc. However, due to the large elastic-plasticity and weak rigidity of PTFE materials, when turning PTFE rod materials on a lathe, the generated chips are difficult to break, resulting in continuous chips; and if the flow of continuous chips is not effectively controlled during the turning process, chip curling will occur due to factors such as the interaction of chips and the micro-perturbation of the workpiece, which will affect the quality of the machined surface and accelerate the wear of the tool. At present, the processing method of manually pulling chips not only has low efficiency, but also is easy to cause harm to the personal safety of workers. Therefore, it is necessary to design a chip curling prevention cutting system to solve the above problems. Among them, in order to ensure the cleanliness of the processing environment and the cleanliness of the recycled PTFE waste chips, cutting fluid should not be used in the cutting system. Summary of the Invention

[0004] In order to solve the problem of chip curling during the turning process of PTFE bellows, the present invention designs a chip curling prevention device and a chip curling prevention method during the turning process of PTFE bellows. The present invention is a device based on dynamic vision to detect the generation of chips, a device based on risk control to change the flow trajectory of chips, a device based on a chip suction and pressure module to realize the stable flow of chips during continuous cutting, and a method based on model construction to accurately analyze the flow trajectory of chips and then design the risk control wind speed.

[0005] The anti-chip curling method for the PTFE bellows turning process of the present invention uses an anti-chip curling device for the PTFE bellows turning process, which includes a PTFE cutting detection system and a PTFE chip recovery system. The PTFE cutting detection system includes a vision detection camera, an air nozzle, and an air supply machine. The vision detection camera, the air supply machine, and the air nozzle are all fixed on the support plate, and the air inlet of the air nozzle is connected to the air supply machine. The PTFE chip recovery system includes a V-shaped cover, a vacuum generator, a linear module, and a chip suction and pressure module; there are two linear modules and two chip suction and pressure modules; the linear module is driven by a motor; a support frame is fixed on the slider of the linear module; the chip suction and pressure module includes a roller brush seat, a roller brush, and a pneumatic motor; the roller brush is hinged on the roller brush seat; the roller brush is driven by the pneumatic motor; the pneumatic motor is fixed on the roller brush seat and is supplied with air by an air pump; the roller brushes of the two chip suction and pressure modules are arranged opposite to each other; the roller brush seats of the two chip suction and pressure modules are respectively fixed to the tops of the two support frames. The top of the V-shaped cover is a V-shaped groove, and a chip inlet is opened at the bottom of the V-shaped groove; a chip flow port is opened at the bottom of the V-shaped cover; the V-shaped cover covers the roller brushes of the two chip suction and pressure modules, and the bottom is fixed on the roller brush seat, and the chip inlet of the V-shaped cover is directly above the gap between the roller brushes of the two chip suction and pressure modules. The vacuum generator is fixed on the inner wall of the V-shaped cover.

[0006] The anti-chip curling method for the PTFE bellows turning process is as follows:

[0007] Step 1: Clamp the PTFE rod on the three-jaw chuck of the lathe and hold it with a center drill; fix the support plate of the PTFE cutting detection system to the tool rest of the lathe; fix the bases of the two linear modules to the lathe bed, and make the V-shaped cover located below the processing starting point of the PTFE rod; then, perform tool setting.

[0008] Step 2: After tool setting is completed, start the lathe to drive the PTFE rod to rotate by the three-jaw chuck, and move the turning tool to the machining starting point; then, the turning tool processes the PTFE rod according to the set machining parameters, and at the same time start the air pump, vacuum generator and motor. The air pump drives the pneumatic motors of the two chip suction and pressure modules to work, so that the roller brushes of the two chip suction and pressure modules rotate towards each other at the same set speed; the vacuum generator generates negative pressure in the V-shaped cover; the motor drives the linear module, and the slider of the linear module drives the support frame, chip suction and pressure module, V-shaped cover and vacuum generator to move synchronously along the axial direction of the PTFE rod following the turning tool; the power supply module 1 continuously supplies power to the vision detection camera, and the vision detection camera feeds the captured chip image back to the controller. When the controller determines that chips are generated or broken, it controls the power supply module 2 to supply power to the air supply machine for a set time and then cut off the power, so that the air nozzle blows the chips towards the chip inlet of the V-shaped cover, and the chips enter the chip inlet of the V-shaped cover under the action of negative pressure in the V-shaped cover, and then enter the gap between the roller brushes of the two chip suction and pressure modules; the roller brushes of the two chip suction and pressure modules convey the chips downward and flow out from the chip outlet of the V-shaped cover. Among them, the air nozzle can also blow off the chips attached to the surface of the turning tool and reduce the temperature of the cutting area.

[0009] The air flow velocity of the air nozzle is designed as follows:

[0010] ① Build a chip flow model: Define the chip starting point as the point where the chip flows out from the secondary cutting edge, the chip contact point as the point where the chip contacts the V-shaped groove of the V-shaped cover, and the chip landing point as the point where the chip reaches the chip inlet of the V-shaped cover; Define the part of the chip between the chip starting point and the chip contact point as the chip unit, and set the length of the chip unit as l 0 , divide the chip unit into n segments to obtain n chip micro-elements, then the length of each chip micro-element is l 0 / n, and each chip micro-element in the chip unit experiences n bending states during the process of moving from the chip starting point to the chip contact point.

[0011] ② The initial velocity V sp of the chip micro-element flowing out from the PTFE rod is calculated as follows:

[0012] V sp = V c / λ h (1)

[0013] λ h = h 1 / h(2)

[0014] h = f·sinκ(3)

[0015] Among them, V c is the cutting speed, λ h is the chip micro-element thickness compression ratio; h 1is the thickness of the compressed chip micro-element; h is the set cutting thickness that has not yet deformed, f is the feed rate, and κ is the main cutting edge angle.

[0016] Then the time t occupied by each bending state of the chip micro-element is: 0 as follows:

[0017] t 0 = l 0 / (n·V sp )(4)

[0018] And the volume Q and mass m of the chip micro-element are respectively:

[0019] Q = b·h 1 ·l 0 / n(5)

[0020] b = a p / sinκ(6)

[0021] m = ρ·Q(7)

[0022] Where, b is the width of the chip micro-element, a p is the radial cutting depth, and ρ is the density of the PTFE material.

[0023] Let the angle between the moment when the chip micro-element flows out from the auxiliary cutting edge and the horizontal plane be θ 0 = 0°, and the vertical velocity of the chip micro-element at the moment when it flows out from the auxiliary cutting edge Let the air flow velocity flowing out from the air nozzle be V w , then at the moment p·t 0 , p = 2,..., n, there is:

[0024] S p = cosθ p-1 ·b·l 0 / n(8)

[0025] F p = 0.5·ρ 0 ·V w 2 ·S p (9)

[0026]

[0027] Where, ρ 0 is the density of the compressed air, S p is the windward area of the chip micro-element at the moment p·t 0 , F p is the wind force received by the chip micro-element at the moment p·t 0 , is the chip micro-element at the moment p·t 0Vertical velocity at time θ p is the angle between the chip micro-element and the horizontal plane at time p·t 0

[0028] Let the angle between the chip micro-element and the horizontal plane at time n·t be θ 0 n ∈(80°, 85°), select the value of n, and according to the iterative formula of formula (11), solve the flow velocity V of the air flow flowing out of the air nozzle w design interval, and select a value from the design interval of V w as the final flow velocity of the air flow flowing out of the air nozzle.

[0029] Preferably, a plurality of the air nozzles are arranged in an array.

[0030] Preferably, a plurality of protrusions are evenly distributed on the surface of the drum brush.

[0031] Preferably, the width of the chip inlet of the V-shaped cover is 10 mm, the length of the chip outlet of the V-shaped cover is less than the length of the chip inlet; the height difference between the chip inlet and the highest position of the drum brush is less than 10 mm.

[0032] Preferably, a vacuum generator is fixed at both ends of the inner wall of the V-shaped cover.

[0033] More preferably, cuboid protrusions are integrally formed at both ends of the chip outlet of the V-shaped cover; the cuboid protrusions are hollow inside, and a plurality of ventilation slots are provided on the side to communicate with the inside; the vacuum generator is fixed inside the cuboid protrusions.

[0034] Preferably, a trolley is provided directly below the chip outlet of the V-shaped cover.

[0035] Preferably, ensure that the speed of the chip flowing through the drum brush is equal to the initial speed V of the chip flowing out of the PTFE rod, then the rotational speed n of the drum brush sp satisfies: 2

[0036] n 2 =[V sp / (π·d 2 )] / 60(12)

[0037] where d 2 is the diameter of the drum brush;

[0038] And the rotational speed n of the lathe spindle 1 satisfies:

[0039] n 1 =[V c / (π·d 1 )] / 60(13)

[0040] where d​​​1 is the diameter of the PTFE rod stock;

[0041] Then, combining with Equation (1), we have:

[0042] n 2 = [d 1 / (d 2 ·λ h )]·n 1 (14)

[0043] Multiply the calculated value of n 2 by the coefficient a as the set value of the roller brush rotation speed, where a ranges from 0.95 to 0.98.

[0044] The beneficial effects of the present invention are as follows:

[0045] 1. The present invention adopts a "blowing - sucking - pressing" mode of high - pressure chip blowing, negative - pressure chip sucking combined with double - roller brush chip pressing to solve the problem of difficult processing of PTFE bellows caused by chip curling. A chip flow model is constructed to describe the change form of the chip outflow state, providing a reference for setting the working parameters of the device, and achieving the purpose of preventing chip curling during turning better. By controlling the chip movement trajectory and keeping the chips continuously and smoothly generated, the present invention has higher economy than chip breaking and can better reduce the uncertain and unstable factors in the cutting process.

[0046] 2. The present invention precisely coordinates the dynamic vision, air - flow - controlled chip flow and chip suction - pressing module. When the chips are generated or broken, the outflow state of the chips is controlled by blowing air, and the chip suction - pressing module ensures that the chips maintain a stable outflow state during the turning of the PTFE bellows and are not prone to chip - curling problems. Further, the present invention designs the relationship between the rotation speed of the roller brush and the rotation speed of the lathe spindle to ensure that the speed of the chips flowing through the roller brush is equal to the initial speed of the chips flowing out of the PTFE rod stock. And to avoid easy chip breaking caused by the machining, assembly errors of each part and other factors, the calculated value of the roller brush rotation speed is multiplied by a coefficient less than 1 as the final set value of the roller brush rotation speed, avoiding the chips being broken due to excessive tension from the PTFE rod stock and the roller brush at both ends or being significantly bent due to too small tension; furthermore, the present invention uses a linear module to follow the movement of the turning tool to avoid the chips being broken due to excessive tension from the PTFE rod stock and the roller brush at both ends or being significantly bent due to too small tension. It can be seen that the present application can well avoid the chip - curling problem during the turning of PTFE bellows, improve the surface machining quality of PTFE bellows, and at the same time reduce the wear of the cutting tool.

[0047] 3. The present invention does not use cutting fluid throughout the turning process of the PTFE bellows, and the chips stably fall into the wheelbarrow for collecting chips after passing through the chip suction and pressing module, ensuring the cleanliness of the processing environment and saving the cleaning and maintenance costs of the machine tool. Moreover, the structure of the present invention is simple and the cost is low. It can be seen that the present invention provides a new idea for improving the processing quality and processing environment of PTFE bellows. BRIEF DESCRIPTION OF THE DRAWINGS

[0048] Figure 1 is a schematic diagram of the overall structure of the present invention;

[0049] Figure 2 is a schematic diagram of a PTFE cutting detection system in the present invention;

[0050] Figure 3 is another schematic diagram of the PTFE cutting detection system in the present invention;

[0051] Figure 4 is an assembly schematic diagram of a vacuum generator, a linear module and a chip suction and pressing module in the present invention;

[0052] Figure 5 is a perspective view and a sectional view of a V-shaped cover in the present invention.

[0053] Figure 6 is a schematic diagram of a chip flow model in the present invention. DETAILED DESCRIPTION OF THE EMBODIMENTS

[0054] The present invention will be further described below with reference to the accompanying drawings.

[0055] As Figure 1 shown, the anti-chip curling device for the turning process of the PTFE bellows includes a PTFE cutting detection system 2 and a PTFE chip recovery system 3.

[0056] As Figure 2 and Figure 3 shown, the PTFE cutting detection system 2 includes a vision detection camera 211, an air nozzle 222 and an air supply machine 221. The vision detection camera 211, the air supply machine 221 and the air nozzle 222 are all fixed on a support plate 23. The air inlet of the air nozzle 222 is connected to the air supply machine 221, and the air supply machine 221 releases compressed air through the air nozzle 222.

[0057] As Figure 4 and Figure 5As shown in the figure, the PTFE chip recycling system 3 includes a V-shaped cover 325, a vacuum generator 323, a linear module, and a chip suction and pressure module; there are two linear modules and two chip suction and pressure modules; the linear module is driven by a motor 312, and the motor 312 is controlled by a controller; a support frame 313 is fixed on the slider of the linear module 311; the chip suction and pressure module includes a roller brush seat 321, a roller brush 322, and a pneumatic motor 324; the roller brush 322 is hinged to the roller brush seat 321; the roller brush 322 is driven by the pneumatic motor 324; the pneumatic motor 324 is fixed on the roller brush seat 321 and is supplied with air by an air pump; the air pump is controlled by the controller; by using the pneumatic motor 324, it can ensure that the roller brush 322 starts and stops quickly, and the pneumatic motor 324 can achieve stepless adjustment of the rotation speed of the roller brush 322; the roller brushes 322 of the two chip suction and pressure modules are arranged opposite to each other; the roller brushes 322 of the two chip suction and pressure modules rotate at the same speed and in opposite directions; the roller brush seats 321 of the two chip suction and pressure modules are respectively fixed to the tops of the two support frames 313. The top of the V-shaped cover 325 is a V-shaped groove with two side walls at 120°, and a chip inlet is provided at the bottom of the V-shaped groove; a chip flow outlet is provided at the bottom of the V-shaped cover 325; the V-shaped cover 325 covers the roller brushes 322 of the two chip suction and pressure modules, and the bottom is fixed on the roller brush seat 321, and the chip inlet of the V-shaped cover 325 is directly above the gap between the roller brushes 322 of the two chip suction and pressure modules, which can ensure that the chips are accurately "pressed" towards the chip flow outlet, avoiding the chips from winding around the roller brush 322 and affecting the normal outflow of the chips; the working area of the roller brush is only connected to the outside through the chip inlet and the chip flow outlet; a vacuum generator 323 is fixed on the inner wall of the V-shaped cover 325, and the vacuum generator 323 discharges the air inside the V-shaped cover 325 from the chip flow outlet, making the air pressure inside the V-shaped cover 325 less than the external atmospheric pressure.

[0058] Among them, the vision detection camera 211 is powered by the first power supply module 212, and the air supply machine 221 is powered by the second power supply module 223; the controller 24 is connected to both the first power supply module 212 and the second power supply module 223 at the same time, and is used to control the on-off states of the two. The signal output end of the vision detection camera 211 is connected to the controller. The vacuum generator 323, the motor 312, the air pump, and the pneumatic motor 324 are all powered by a third power supply module (not shown in the figure). The vacuum generator 323, the motor 312, and the air pump are all controlled by the controller.

[0059] As a preferred embodiment, a plurality of air nozzles 222 are arranged in an array.

[0060] As a preferred embodiment, a plurality of protrusions are evenly distributed on the surface of the roller brush 322, which increases the contact area with the chips during the chip pressing process, enables the chips to receive a relatively uniform frictional force, ensures a relatively stable state of the chips between the cutting tool tip and the roller brush, and thus reduces the uncertainty during the turning process.

[0061] As a preferred embodiment, the chip inlet width of the V-shaped cover 325 is 10 mm, the chip flow outlet length of the V-shaped cover 325 is less than the chip inlet length; the height difference between the chip inlet and the highest position of the drum brush is less than 10 mm.

[0062] As a preferred embodiment, a vacuum generator 323 is fixed at both ends of the inner wall of the V-shaped cover 325.

[0063] More preferably, integrally formed rectangular protrusions are provided at both ends of the chip flow outlet of the V-shaped cover 325; the inside of the rectangular protrusion is hollow, and a plurality of ventilation slots are provided on the side to communicate with the inside; the vacuum generator 323 is fixed inside the rectangular protrusion.

[0064] As a preferred embodiment, a trolley 5 is provided directly below the chip flow outlet of the V-shaped cover 325 for collecting chips.

[0065] The chip anti-rolling method of the chip anti-rolling device for the PTFE corrugated pipe turning process is as follows:

[0066] Step 1: Clamp the PTFE rod 4 on the three-jaw chuck of the lathe and hold it with a center; fix the support plate 23 of the PTFE cutting detection system 2 to the tool rest of the lathe; fix the bases of the two linear modules 311 to the lathe bed, and make the V-shaped cover 325 located below the processing starting point of the PTFE rod 4; then, perform tool setting.

[0067] Step 2: After the tool setting is completed, the lathe 1 is started, the three-jaw chuck drives the PTFE rod 4 to rotate, and the turning tool is moved to the processing starting point; then, the turning tool processes the PTFE rod according to the set processing parameters, and the air pump, vacuum generator 323 and motor 312 are started at the same time. The air pump drives the pneumatic motors 324 of the two chip suction and pressure modules to work, so that the roller brushes 322 of the two chip suction and pressure modules rotate in opposite directions at the same set speed; the vacuum generator 323 generates a vacuum in the V-shaped cover 325. The motor 312 drives the linear module 311, and the slider of the linear module 311 drives the support frame 313, the chip suction and pressure module, the V-shaped cover 325 and the vacuum generator 323 to move synchronously along the axial direction of the PTFE rod 4 with the turning tool to prevent the ends of the chips from breaking due to excessive tension of the PTFE rod 4 and the roller brush 322 or obvious bending due to insufficient tension; the power supply module 212 continuously supplies power to the visual inspection camera 211, and the visual inspection camera 211 captures the chip image. The image is fed back to the controller 24. When the controller 24 determines that chips are generated or broken, it controls the power supply module 223 to supply power to the air supply machine 221 for a set time and then cuts off the power, so that the air nozzle 222 blows the chips to the chip inlet of the V-shaped cover 325. The chips enter the chip inlet of the V-shaped cover 325 under the negative pressure in the V-shaped cover 325, and then enter the gap between the roller brushes 322 of the two chip suction and pressure modules; wherein the V-shaped groove on the top of the V-shaped cover 325 plays a guiding role; and, moreover, ensure that the air supply machine 22 1 works only for a short time. After the chips enter the working area of ​​the roller brush, there is no airflow to disrupt the stable chip flow state. At the same time, the air supply machine 221 only works for a short time, which can save electricity and reduce production costs. Among them, the air supply machine 221 can steplessly adjust the flow rate of the air flow out of the air nozzle 222. The air supply machine 221 and the air nozzle 222 not only provide wind power for changing the chip trajectory, but also blow away the tiny debris attached to the tool surface and reduce the temperature of the cutting area, thereby increasing the service life of the tool. The roller brushes 322 of the two chip suction and pressure modules transport the chips downward and flow out from the chip flow port of the V-shaped cover 325.

[0068] The visual inspection camera 211 detects chip generation or chip breaking in real time. When chip breaking occurs at any time during the processing of the PTFE rod 4, the present invention can blow the newly generated chips into the chip inlet of the V-shaped cover 325 again, and drive the roller brushes 322 of the two chip suction and pressure modules to flow out from the chip flow port of the V-shaped cover 325, thereby realizing the chip prevention effect of the entire processing process of the PTFE rod 4.

[0069] like Figure 6 As shown, as a preferred embodiment, in order to allow the chips to smoothly enter the chip inlet of the V-shaped cover 325, the air flow rate of the air nozzle 222 is designed as follows:

[0070] ①Construct a chip flow model: When a turning tool turns a PTFE rod, chips are generated. After flowing through the secondary cutting edge of the turning tool, the chips leave the turning tool and bend downward under the action of the air flow of the air nozzle 222. Define the point where the chips flow out from the secondary cutting edge as the chip starting point, the point where the chips contact the V-shaped groove of the V-shaped cover 325 as the chip contact point, the point where the chips reach the chip inlet of the V-shaped cover 325 as the chip landing point, and define the flow trajectory of the chips before entering the chip inlet of the V-shaped cover 325 as the trajectory from the chip starting point to the chip contact point and then from the chip contact point to the chip landing point; among them, the connection line between the chip starting point and the chip contact point is defined as side Ⅰ (the trajectory of the chips from the chip starting point to the chip contact point is not a straight line, and side Ⅰ is defined here for the intuitive expression of the flow trajectory of the chips before reaching the V-shaped groove of the V-shaped cover 325), the connection line between the chip contact point and the chip landing point is defined as side Ⅱ, and the connection line between the chip starting point and the chip landing point is defined as side Ⅲ. Define the part of the chips between the chip starting point and the chip contact point as the chip unit, and set the length of the chip unit as l 0 , divide the chip unit into n segments to obtain n chip micro-elements, and the length of each chip micro-element is l 0 / n. Correspondingly, each chip micro-element in the chip unit experiences n bending states during the process of moving from the chip starting point to the chip contact point.

[0071] ②The initial velocity V of the chip micro-element flowing out from the PTFE rod sp is calculated as follows:

[0072] V sp = V c / λ h (1)

[0073] λ h = h 1 / h(2)

[0074] h = f·sinκ(3)

[0075] Among them, V c is the cutting speed, λ h is the thickness compression ratio of the chip micro-element; h 1 is the thickness of the compressed chip micro-element, which can be measured by a vernier caliper after trial cutting of the PTFE rod; h is the set cutting thickness before deformation, f is the feed rate, and κ is the main cutting edge angle.

[0076] Then the time t occupied by each bending state of the chip micro-element is: 0 as follows:

[0077] t 0 = l 0 / (n·V sp )(4)

[0078] The volume Q and mass m of the chip element are respectively as follows:

[0079] Q = b·h 1 ·l 0 / n(5)

[0080] b = a p / sinκ(6)

[0081] m = ρ·Q(7)

[0082] Among them, b is the width of the chip element, a p is the radial depth of cut, and ρ is the density of the PTFE material.

[0083] Since the chip element flows out from the secondary cutting edge close to the horizontal state, the angle between the moment when the chip element flows out from the secondary cutting edge and the horizontal plane can be set as θ 0 = 0°, then the vertical velocity of the chip element at the moment when it flows out from the secondary cutting edge Let the air flow velocity flowing out of the air nozzle be V w , since the chip element is mainly affected by the air flow force flowing out of the air nozzle after flowing out from the secondary cutting edge (the gravity and air resistance of the chip element can be ignored), and the chip element is in a bent-down state after time t 0 (at this time, the horizontal velocity of the chip element is much smaller than the vertical velocity and can be ignored), then at time p·t 0 , p = 2,..., n, there is:

[0084] S p = cosθ p-1 ·b·l 0 / n(8)

[0085] F p = 0.5·ρ 0 ·V w 2 ·S p (9)

[0086]

[0087] Among them, ρ 0 is the density of the compressed air, S p is the windward area of the chip element at time p·t 0 (it can also be understood as the windward area of the p-th chip element, because the chip element has become the p-th chip element at time p·t 0 since it was generated), F p is the wind force received by the chip element at time p·t 0 , is the chip element at time p·t 0Vertical velocity at time θ p is the chip element at time pgt 0 the angle with the horizontal plane.

[0088] To effectively achieve the outflow of the chip from the secondary cutting edge t 0 After the moment, it changes from horizontal to a state tending to be vertical. It is necessary to satisfy that the angle θ of the chip element with the horizontal plane at time n·t 0 ∈(80°, 85°). At this time, the chip element contacts the V-shaped groove of the V-shaped cover 325. Select the value of n, and according to the iterative formula of formula (11), solve the flow velocity V of the air flow flowing out of the air nozzle n Design interval, and select a value from the design interval of V w as the final air flow velocity flowing out of the air nozzle. In this embodiment, n = 50 is selected. Then in the interval of θ w ∈(80°, 85°), the obtained design interval of V n is (5m / s, 50m / s). w As a preferred embodiment, since the chip enters the chip inlet of the V-shaped cover 325 and is in the gap between the roller brushes 322 of the two chip suction and pressure modules, the angle between the chip and the horizontal plane no longer changes. At this time, it should be ensured that the speed of the chip flowing through the roller brush (i.e., the speed of the outer circumferential surface of the roller brush) is equal to the initial speed V of the chip flowing out of the PTFE rod

[0089] Then the rotational speed n of the roller brush sp satisfies: 2 Satisfy:

[0090] n 2 =[V sp / (π·d 2 )] / 60(12)

[0091] where d 2 is the diameter of the roller brush;

[0092] And the rotational speed n of the lathe spindle 1 satisfies:

[0093] n 1 =[V c / (π·d 1 )] / 60(13)

[0094] where d 1 is the diameter of the PTFE rod;

[0095] Then combined with formula (1), there is:

[0096] n 2 =[d 1 / (d 2 ·λ h )]·n1 (14)

[0097] Finally, to avoid easy chip breaking caused by the machining and assembly errors of each part and the influence of other factors, multiply the calculated value of n 2 by the coefficient a as the set value of the roller brush rotation speed, and a takes values between 0.95 and 0.98. In this embodiment, the designed lathe spindle rotation speed n 1 = 600 r / min, and the roller brush rotation speed n 2 = 200 r / min.

Claims

1. Method for preventing chip curling during the turning process of PTFE corrugated pipes, and the chip curling prevention device for the turning process of PTFE corrugated pipes, which includes a PTFE cutting detection system and a PTFE chip recovery system. It is characterized in that: The PTFE cutting detection system includes a vision detection camera, an air nozzle, and an air supply machine; the vision detection camera, the air supply machine, and the air nozzle are all fixed on the support plate, and the air inlet of the air nozzle is connected to the air supply machine; the PTFE chip recovery system includes a V-shaped cover, a vacuum generator, a linear module, and a chip suction and pressure module; there are two linear modules and two chip suction and pressure modules; the linear module is driven by a motor; a support frame is fixed on the slider of the linear module; the chip suction and pressure module includes a roller brush seat, a roller brush, and a pneumatic motor; the roller brush is hinged on the roller brush seat; the roller brush is driven by the pneumatic motor; the pneumatic motor is fixed on the roller brush seat and is supplied with air by an air pump; the roller brushes of the two chip suction and pressure modules are arranged opposite to each other; the roller brush seats of the two chip suction and pressure modules are respectively fixed to the tops of the two support frames; the top of the V-shaped cover is a V-shaped groove, and a chip inlet is opened at the bottom of the V-shaped groove; a chip flow outlet is opened at the bottom of the V-shaped cover; the V-shaped cover covers the roller brushes of the two chip suction and pressure modules, and the bottom is fixed on the roller brush seat, and the chip inlet of the V-shaped cover is directly above the gap between the roller brushes of the two chip suction and pressure modules; a vacuum generator is fixed on the inner wall of the V-shaped cover. The specific method is as follows: Step 1: Clamp the PTFE rod on the three-jaw chuck of the lathe and hold it with a center; fix the support plate of the PTFE cutting detection system to the tool rest of the lathe; fix the bases of the two linear modules to the lathe bed, and make the V-shaped cover located below the processing starting point of the PTFE rod; then, perform tool setting. Step 2: After completing tool setting, start the lathe to make the three-jaw chuck drive the PTFE rod to rotate, and move the turning tool to the processing starting point; then, the turning tool processes the PTFE rod according to the set processing parameters. At the same time, start the air pump, the vacuum generator, and the motor. The air pump drives the pneumatic motors of the two chip suction and pressure modules to work, so that the roller brushes of the two chip suction and pressure modules rotate towards each other at the same set speed; the vacuum generator generates negative pressure in the V-shaped cover; the motor drives the linear module, and the slider of the linear module drives the support frame, the chip suction and pressure module, the V-shaped cover, and the vacuum generator to move synchronously along the axial direction of the PTFE rod following the turning tool; the power supply module 1 continuously supplies power to the vision detection camera, and the vision detection camera feeds back the captured chip image to the controller. When the controller determines that chips are generated or broken, it controls the power supply module 2 to supply power to the air supply machine for a set time and then cut off the power, so that the air nozzle blows the chips towards the chip inlet of the V-shaped cover, and the chips enter the chip inlet of the V-shaped cover under the action of the negative pressure in the V-shaped cover, and then enter the gap between the roller brushes of the two chip suction and pressure modules; the roller brushes of the two chip suction and pressure modules convey the chips downward and flow out from the chip flow outlet of the V-shaped cover; among them, the air nozzle can also blow away the chips attached to the surface of the turning tool and reduce the temperature of the cutting area. The air flow velocity of the air nozzle is designed as follows: ①Construct a chip flow model: Define the point where the chip flows out from the secondary cutting edge as the chip starting point, the point where the chip contacts the V-shaped groove of the V-shaped cover as the chip contact point, and the point where the chip reaches the chip inlet of the V-shaped cover as the chip landing point; Define the part of the chip between the chip starting point and the chip contact point as the chip unit, and set the length of the chip unit as l 0 , Divide the chip unit into n segments to obtain n chip micro-elements, then the length of each chip micro-element is l 0 / n. During the process of each chip micro-element in the chip unit moving from the chip starting point to the chip contact point, it experiences n bending states; ② The initial velocity V of the chip element flowing out of the PTFE rod sp is calculated as follows: V sp = V c / λ h (1) λ h = h 1 / h (2) h = f·sinκ (3) Among them, V c is the cutting speed, and λ h is the chip micro-element thickness compression ratio; h 1 is the thickness of the compressed chip micro-element; h is the set cutting thickness that has not yet deformed, f is the feed rate, and κ is the main cutting edge angle; Then the time t occupied by each bending state of the chip microelement 0 is as follows: t 0 = l 0 / (n·V sp ) (4) And the volume Q and mass m of the chip microelement are respectively: Q = b·h 1 ·l 0 / n (5) b = a p / sinκ (6) m = ρ·Q (7) Among them, b is the width of the chip microelement, a p is the radial depth of cut, and ρ is the density of the PTFE material; Let the angle between the moment when the chip element flows out from the auxiliary cutting edge and the horizontal plane be θ 0 = 0°, and the vertical velocity V of the chip element at the moment when it flows out from the auxiliary cutting edge y0 = 0; Let the flow velocity of the air flow flowing out from the air nozzle be V w , then at the moment p·t 0 , where p = 2,..., n, there is: S p = cosθ p-1 ·b·l 0 / n (8) F p = 0.5·ρ 0 ·V w 2 ·S p (9) where ρ 0 is the density of the compressed air, S p is the frontal area of the chip microelement at time p·t 0 , F p is the wind force acting on the chip microelement at time p·t 0 , is the vertical velocity of the chip microelement at time p·t 0 , θ p is the angle between the chip microelement and the horizontal plane at time p·t 0 ; Let the chip microelement be at the moment n·t 0 The angle θ with the horizontal plane n ∈(80°, 85°), select the value of n, and solve the air flow velocity V flowing out of the air nozzle according to the iterative formula of Equation (11) w Design interval of w Select a value from the design interval of V as the final air flow velocity flowing out of the air nozzle.

2. The method for preventing chip curling during the turning process of PTFE bellows according to claim 1, wherein: a plurality of the air nozzles are arranged in an array.

3. The method for preventing chip curling during the turning process of PTFE bellows according to claim 1, wherein: a plurality of protrusions are evenly distributed on the surface of the roller brush.

4. The method for preventing chip curling during the turning process of PTFE bellows according to claim 1, wherein: the width of the chip inlet of the V-shaped cover is 10 mm, the length of the chip outlet of the V-shaped cover is less than the length of the chip inlet; the height difference between the chip inlet and the highest position of the roller brush is less than 10 mm.

5. The method for preventing chip curling during the turning process of PTFE bellows according to claim 1, wherein: a vacuum generator is fixed at both ends of the inner wall of the V-shaped cover.

6. The method for preventing chip curling during the turning process of PTFE bellows according to claim 5, wherein: rectangular protrusions are integrally formed at both ends of the chip outlet of the V-shaped cover; the inside of the rectangular protrusion is hollow, and a plurality of ventilation slots are formed on the side and communicated with the inside; the vacuum generator is fixed inside the rectangular protrusion.

7. The method for preventing chip curling during the turning process of PTFE bellows according to claim 1, wherein: a trolley is arranged directly below the chip outlet of the V-shaped cover.

8. The method for preventing chip curling during the turning process of PTFE bellows according to claim 1, wherein: Ensure that the speed of the chip flowing through the drum brush is equal to the initial speed V of the chip flowing out of the PTFE rod sp Then the rotational speed n of the drum brush 2 Satisfies: n 2 = [V sp / (π · d 2 )] / 60(12) Among them, d 2 is the diameter of the drum brush; The spindle speed n of the lathe 1 satisfies: n 1 = [V c / (π·d 1 )] / 60 (13) where d 1 is the diameter of the PTFE rod stock; then combined with formula (1), there is: Multiply the calculated value of n 2 by the coefficient a to obtain the set value of the rotating speed of the drum brush, where a ranges from 0.95 to 0.98.

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