A chip suction turning method and device for polytetrafluoroethylene rods

Abstract

The present invention discloses a chip suction turning method and device for polytetrafluoroethylene rods. The chip suction method first predicts the PTFE chip radius and chip generation rate based on known cutting process parameters, and then determines the optimal chip suction port diameter and negative pressure suitable for the cutting process parameters through a turning experiment based on the TOPSIS method. Under the premise of ensuring sufficient suction force, the problem of unstable air flow velocity and the possibility that chips cannot be effectively attracted into the chip suction device due to an overly large diameter is avoided, and the problem of chip entanglement affecting the surface quality of the workpiece, the tool life and the safety of the operator in the PTFE turning process is solved.

Description

Technical Field

[0001] The invention relates to the field of high-performance cutting of polymer materials, and in particular to a chip suction turning method and device for polytetrafluoroethylene rods. Background Art

[0002] There is a serious problem in the turning process of polytetrafluoroethylene (PTFE) rods, that is, the continuous chips produced have high toughness and are not easy to break, causing the chips to entangle on the tool, workpiece and spindle. The chip accumulation in the cutting zone causes heat to accumulate on the tool and workpiece instead of being removed, which affects the surface quality of the workpiece and the tool life. If the chips continue to accumulate and do not fall off the workpiece, it may even have a negative impact on the safety of the operator. Therefore, the chips need to be removed in a timely manner. The current methods of removing chips are mainly to optimize cutting parameters, tool chip breakers, cutting vibrations and add coolants, but due to the high toughness of PTFE, these methods have little effect. How to remove PTFE chips simply and promptly, and thus optimize processing quality, ensure tool life and operator safety, is particularly important.

[0003] For example, the invention patent of CN 209239626 U discloses a chip suction device including a suction fan, a chip collection box and a chip suction pipe. The chip suction machine provided can replace manual cleaning, save manpower, time and effort, make the cleaning of iron chips on the lathe convenient and quick, and reduce the work intensity of the operator, solving the technical problems of the difficulty in cleaning the iron chips generated by the lathe and the high cleaning intensity in the prior art. For example, the invention patent of CN 212218662 discloses a magnetic chip suction device that uses the magnetic power of a magnet to absorb steel chips, and then moves the magnet a certain distance away from the adsorption bottom surface to reduce the magnetic force of the adsorption bottom surface, so that the steel chips are separated from the adsorption bottom surface due to gravity, so as to achieve the purpose of cleaning the steel chips inside large box-type parts. The CN212218662U patent discloses that it can eliminate static electricity on the material, increase the strength of the chip suction, improve the chip suction effect, and can fully and thoroughly suck up the sawdust, thereby improving the working environment.

[0004] However, the above devices all have fixed chip suction opening sizes or use high air pressure to suck chips. Excessive negative pressure and aperture will increase the energy consumption of the chip suction system. High negative pressure requires greater fan power and compressed air flow, which increases energy consumption and operating costs. At the same time, excessive negative pressure and aperture may reduce the chip suction effect. Although a large negative pressure can produce a strong suction force, if the aperture is too large, it will cause unstable airflow velocity, and the chips may not be effectively attracted into the chip suction device. This will cause excessive accumulation of chips in the cutting area, affecting the cutting quality and the surface finish of the workpiece. In summary, when designing and operating a chip suction device, it is necessary to comprehensively consider the cutting conditions, material properties and the capabilities of the chip suction system, and make reasonable adjustments to the negative pressure size and aperture to achieve the best chip suction effect and energy utilization efficiency of the chip suction device. Summary of the Invention

[0005] The present invention addresses the current problem of continuous chips generated during the turning process of polytetrafluoroethylene (PTFE) bars being highly tough and difficult to break, which can then entangle the tool, workpiece, and spindle, leading to reduced cutting quality and even production safety hazards. The present invention provides a method and device for turning polytetrafluoroethylene bars with chip suction. The present invention provides a chip collection device that can adjust the air pressure and chip suction aperture to control suction force; a method that can predict the chip radius and flow rate based on turning process parameters; a method that uses the TOPSIS method to select the optimal chip suction aperture and air pressure suitable for the current process parameters; and a device for removing negative pressure chips during the turning process of polytetrafluoroethylene, integrating chip prediction, servo drive, and air pressure regulation.

[0006] The present invention provides a chip suction turning method for polytetrafluoroethylene rods, comprising the following steps:

[0007] Step 1: Predict the chip radius and chip generation rate generated by the polytetrafluoroethylene bar workpiece as follows:

[0008] 1 / 3 of L from the tip of the knife f The length of the cutting edge is taken as the equivalent force point of the front cutting edge support force, and the chip radius prediction calculation formula is:

[0009]

[0010] Among them, E is the elastic modulus of the workpiece material, I is the cross-sectional distance of the chip section, F1 is the equivalent force on the tool rake face, L f is the length of the contact part between the tool and the chip, h is the chip thickness, is the shear angle of the chip, γ is the tool rake angle, τ s is the shear strength of the workpiece material.

[0011] For turning, the average cutting speed is:

[0012]

[0013] Among them, d m is the diameter of the machined surface, d w is the diameter of the surface to be machined.

[0014] The chip generation rate prediction formula is:

[0015]

[0016] Among them, A D represents the cutting area, v av represents the average cutting speed, a p is the depth of cut, and f is the feed rate.

[0017] Step 2: Determine the constraints:

[0018]

[0019] Among them, r is the radius of the chip suction port during chip suction, r1 is the chip radius; the minimum negative pressure required inside the chip suction port during chip suction P1 is the ambient atmospheric pressure, ρ is the workpiece material density, t is the processing time; θ is the angle between the central axis of the chip suction port and the horizontal plane, and the chip suction port is set above the workpiece.

[0020] Step 3: Based on the TOPSIS method and turning experiments, the optimal values ​​of the chip suction port radius and the negative pressure inside the chip suction port are determined as follows:

[0021] Set the optional values ​​of the chip suction port radius r1, r2, r3, r4, r5 and the optional values ​​of the negative pressure inside the chip suction port p1, p2, p3, p4, p5, and obtain 25 chip suction port radius and negative pressure configuration schemes, thereby obtaining the chip suction port radius and negative pressure configuration scheme set A={A1, A2, ..., A 25 The chip suction efficiency η and the surface roughness R of the workpiece after turning are used to calculate the chip suction efficiency η and the surface roughness R of the workpiece after turning. a As an indicator, set the average cutting speed v av , feed rate f and back cutting depth a p , under various configuration schemes, the workpiece is turned to conduct experiments; the chip suction efficiency and the surface roughness of the workpiece after turning are recorded, and the attribute set B of the chip suction efficiency and the surface roughness of the workpiece after turning under various configuration schemes is obtained. a Then, the TOPSIS method was used to select the optimal configuration scheme from the 25 configuration schemes, so as to set the average cutting speed v av , feed rate f and back cutting depth a p When the workpiece is actually turned, the chip suction port radius and negative pressure in the optimal configuration scheme are used to suction the chips.

[0022] Preferably, the tool rake face has equal effect:

[0023]

[0024] Among them, τ s is the shear strength of the workpiece material, T is the width of the tool (such as a grooving tool), h is the chip thickness, is the shear angle of the chip, and γ is the tool rake angle.

[0025] Length of the tool in contact with the chip:

[0026]

[0027] The chip cross section is approximated as a rectangle, and the cross-sectional distance of the chip cross section is:

[0028]

[0029] Preferably, the minimum negative pressure P required inside the chip suction port during chip suction is min The solution process is as follows:

[0030] You must ensure that:

[0031] F>G′=mg sinθ

[0032] Among them, F is the suction force of the chip suction port, G' is the component force of the gravity on the chips along the central axis of the chip suction port;

[0033] Chip mass produced per unit time:

[0034] m=Qρt

[0035] Then F=(P1-P)S=(P1-P)πr 2 >Qρtg sinθ

[0036] have to

[0037] Among them, P is the negative pressure inside the chip suction port, and S is the area of ​​the chip suction port.

[0038] Preferably, the process of selecting the optimal configuration scheme from 25 configuration schemes using the TOPSIS method is as follows:

[0039] 1) Establish a decision matrix:

[0040]

[0041] Among them, a i For configuration plan A i Chip suction efficiency recorded in the turning experiment, b i For configuration plan A iSurface roughness of workpiece after turning recorded in the turning experiment, i = 1, 2, ..., 25;

[0042] 2) Construct a normalized matrix

[0043] The chip suction efficiency and surface roughness of the workpiece after turning in the decision matrix are dimensionlessly processed to obtain the normalized decision matrix:

[0044]

[0045] Among them, configuration plan A i Normalized value of chip suction efficiency recorded in the turning experiment Configuration Plan A i Normalized value of workpiece surface roughness after turning recorded in the turning experiment

[0046] 3) Construct a weighted normalized decision matrix:

[0047]

[0048] Among them, configuration plan A i Normalized weighted value z of chip suction efficiency recorded in turning experiment 1i =w1a' i , configuration plan A i The normalized weighted value z of the workpiece surface roughness after turning recorded in the turning experiment 2i =w2b' i w1 and w2 are weights;

[0049] 4) Determine the positive ideal solution and negative ideal solutions After that, calculate configuration plan A i The distance from the normalized weighted value of the chip suction efficiency recorded in the turning experiment and the normalized weighted value of the surface roughness of the workpiece after turning recorded in the turning experiment to the positive and negative ideal solutions

[0050]

[0051] in, is the maximum value of the normalized weighted value of each scrap collection efficiency, is the minimum value of the normalized weighted value of the workpiece surface roughness after each turning process, is the minimum value of the normalized weighted value of each scrap collection efficiency, is the maximum value of the normalized weighted value of the workpiece surface roughness after each turning process;

[0052] 5) Calculate each configuration scheme A i Relative proximity

[0053]

[0054] 6) Based on relative proximity The priority of each configuration scheme is sorted in descending order according to the size of the value, and the The configuration scheme with the largest value is regarded as the optimal configuration scheme.

[0055] The present invention provides a chip suction device for polytetrafluoroethylene rods, comprising a chip suction pipe, a chip suction aperture changing assembly, and a negative pressure generating device. The fluid input port of the negative pressure generating device is connected to the fluid output port of the chip suction pipe, with a screen provided at the connection point. A chip discharge port is provided on the side of the chip suction pipe.

[0056] The chip suction aperture change assembly includes an upper cover, a driving gear, a driven gear, and blades. The upper cover is fixed to the chip suction pipe, the base of the stepper motor is fixed to the upper cover, and the driving gear is fixed to the output shaft of the stepper motor; the driven gear and the upper cover form a rotating pair and mesh with the driving gear; the hub of the driven gear is provided with a center hole, the wall of the center hole is provided with n radial grooves evenly distributed along the circumference, the blades are provided with n blades, the outer edge of the fluid inlet of the chip suction pipe is provided with n branch holes evenly distributed along the circumference, 6≤n≤12; the first branch hole provided at one end of the blade is fixed with a support shaft 1, and the second branch hole provided at the other end is fixed with a support shaft 2, and Support shaft one and support shaft two are located on different sides of the blade; support shaft one on each blade forms a sliding pair with one of the radial grooves, and support shaft two on each blade forms a rotating pair with a branch hole three on the chip suction pipe, and the radial groove and branch hole three connected to the same blade are staggered in the circumferential position; the blades are stacked in sequence along the circumference, and the support shaft one of each blade is placed facing the driven gear, and the end of the last blade fixed with support shaft two is inserted under the first blade stacked in sequence; the blades enclose a chip suction port, and the center hole of the driven gear hub is connected to the center hole of the upper cover and the chip suction port.

[0057] The present invention has the following beneficial effects:

[0058] By providing a variable chip suction port diameter and negative pressure, the present invention ensures sufficient suction while avoiding the problem of unstable airflow velocity and the inability of chips to be effectively drawn into the chip suction device caused by an overly large port diameter. The present invention first predicts the PTFE chip radius and chip generation rate based on known cutting process parameters. Then, through turning experiments based on the TOPSIS method, the optimal chip suction port diameter and negative pressure suitable for these cutting process parameters are determined. This invention addresses the problem of chip entanglement during PTFE turning, which affects workpiece surface quality, tool life, and operator safety. BRIEF DESCRIPTION OF THE DRAWINGS

[0059] Figure 1 Schematic diagram of the process parameters of the tool and chips during cutting.

[0060] Figure 2This is a schematic diagram of a polytetrafluoroethylene rod material chip suction device of the present invention.

[0061] Figure 3 It is a schematic diagram of the chip suction aperture changing component in the present invention.

[0062] Figure 4 It is a schematic diagram of the chip suction pipeline in the present invention.

[0063] Figure 5 This is a schematic diagram of blade stacking in the present invention.

[0064] Figure 6 Schematic diagram of a single blade in the present invention.

[0065] Figure 7 The present invention is a flow chart of a polytetrafluoroethylene bar material chip suction turning method.

[0066] Figure 8 This is a flow chart for determining the optimal values ​​of the chip suction port radius and the negative pressure inside the chip suction port in the present invention. DETAILED DESCRIPTION

[0067] The present invention will be further described below with reference to the accompanying drawings.

[0068] like Figure 7 As shown, a chip suction turning method for polytetrafluoroethylene rod material includes the following steps:

[0069] Step 1: Predict the chip radius and chip generation rate generated by the polytetrafluoroethylene bar workpiece as follows:

[0070] The chip radius prediction process is as follows:

[0071] After being squeezed by the tool, the chips flow out along the rake face, and after being supported by the rake face, they leave the tool at a fixed radius r1, as shown in the following example. Figure 1 As shown, the length of the contact part between the tool and the chip is L f , the shear angle of the chip during turning is The thickness of the uncut layer (the initial thickness of the workpiece cutting area before it comes into contact with the tool) is h w , the chip thickness is h.

[0072] Since the workpiece material reaches the shear stress limit on the shear surface, the equivalent effect on the rake face is:

[0073]

[0074] Among them, τ s is the shear strength of the workpiece material, T is the width of the tool (such as a grooving tool), h is the chip thickness, is the shear angle of the chip, and γ is the tool rake angle.

[0075] According to the tool-chip contact length theory, the length of the contact part between the tool and the chip is:

[0076]

[0077] The chip cross section is approximated as a rectangle, and the cross-sectional distance of the chip cross section is:

[0078]

[0079] 1 / 3 of L from the tip of the knife f The length of the cutting edge is taken as the equivalent force point of the front cutting edge support force, and the chip radius prediction calculation formula is:

[0080]

[0081] Where, E is the elastic modulus of the workpiece material;

[0082] The chip generation rate prediction process is as follows:

[0083] Chip generation rate Q and material removal rate Z w Similarly, it represents the volume of material removed from the workpiece by the tool per unit time, so the chip generation rate is:

[0084] Q=Z w =1000A D v av

[0085] Among them, A D represents the cutting area, v av represents the average cutting speed;

[0086] For turning, the average cutting speed is:

[0087]

[0088] Among them, d m is the diameter of the machined surface, d w is the diameter of the surface to be machined.

[0089] The chip generation rate prediction formula is:

[0090]

[0091] Among them, a p is the depth of cut, and f is the feed rate.

[0092] Step 2: Determine the constraints, as follows:

[0093] When suctioning chips, the suction port needs to generate a suction force F that is sufficient to suck in the generated chips. Assuming that the chip suction port is above the workpiece and the angle between the central axis of the chip suction port and the horizontal plane is θ, it is necessary to ensure that:

[0094] F>G′=mg sinθ

[0095] Among them, G′ is the component of the gravity acting on the chips along the central axis of the chip suction port;

[0096] In addition, when suctioning chips, the radius r of the chip suction port needs to be larger than the chip radius r1, that is, r>r1;

[0097] Chip mass produced per unit time:

[0098] m=Qρt

[0099] Where ρ is the workpiece material density and t is the processing time;

[0100] F=(P1-P)S=(P1-P)πr 2 >Qρtg sinθ

[0101] Right now

[0102] Among them, P1 is the ambient atmospheric pressure, P is the negative pressure inside the suction port, S is the area of ​​the suction port, and P is the pressure of the suction port. min It is the minimum negative pressure required inside the chip suction port when sucking chips.

[0103] The final constraints are determined to be

[0104]

[0105] Step 3: Figure 8 As shown in the figure, based on the TOPSIS method combined with the turning experiment, the optimal values ​​of the chip suction port radius and the negative pressure inside the chip suction port are determined as follows:

[0106] Set the optional values ​​of the chip suction port radius r1, r2, r3, r4, r5 and the optional values ​​of the negative pressure inside the chip suction port p1, p2, p3, p4, p5, and obtain 25 chip suction port radius and negative pressure configuration schemes, thereby obtaining the chip suction port radius and negative pressure configuration scheme set A={A1, A2, ..., A 25 The chip suction efficiency η and the surface roughness R of the workpiece after turning are used to calculate the chip suction efficiency η and the surface roughness R of the workpiece after turning. a As an indicator, set the average cutting speed v av , feed rate f and back cutting depth (cutting depth) a p , under various configuration schemes, the workpiece is turned and the chip suction efficiency and the surface roughness of the workpiece after turning are recorded, and the attribute set B = {η, Ra Then, since the configuration scheme with the highest chip suction efficiency and the best workpiece surface roughness often does not exist, the TOPSIS method is used to select the optimal configuration scheme from 25 configuration schemes, so as to set the average cutting speed v av , feed rate f and back cutting depth a p When the workpiece is actually turned, the chip suction port radius and negative pressure in the optimal configuration scheme are used to suction the chips.

[0107] The process of selecting the optimal configuration scheme from 25 configuration schemes using the TOPSIS method is as follows:

[0108] 1) Establish a decision matrix:

[0109]

[0110] Among them, a i For configuration plan A i Chip suction efficiency recorded in the turning experiment, b i For configuration plan A i The surface roughness of the workpiece after turning recorded in the turning experiment, i = 1, 2, ..., 25; a i 、b i 、A i The corresponding relationship is shown in Table 1;

[0111] Table 1

[0112] η <![CDATA[R a ]]> <![CDATA[A1]]> <![CDATA[a1]]> <![CDATA[b1]]> <![CDATA[A2]]> <![CDATA[a2]]> <![CDATA[b2]]> <![CDATA[A3]]> <![CDATA[a3]]> <![CDATA[b3]]> … … … <![CDATA[A 24 ]]> <![CDATA[a4]]> <![CDATA[b 24 ]]> <![CDATA[A 25 ]]> <![CDATA[a5]]> <![CDATA[b 25 ]]>

[0113] 2) Construct a normalized matrix

[0114] In solving practical problems, since the dimensions and ranges of each indicator are generally different, in order to better reflect the actual changes in the attributes of each indicator, it is necessary to perform dimensionless processing on each indicator. The chip suction efficiency and the surface roughness of the workpiece after turning in the decision matrix are dimensionless, and the standardized decision matrix is ​​obtained:

[0115]

[0116] Among them, configuration plan A i Normalized value of chip suction efficiency recorded in the turning experiment Configuration Plan A i Normalized value of workpiece surface roughness after turning recorded in the turning experiment a' i 、b i '、A i The corresponding relationship is shown in Table 2;

[0117] Table 2

[0118]

[0119]

[0120] 3) Construct a weighted normalized decision matrix:

[0121]

[0122] Among them, configuration plan A i Normalized weighted value z of chip suction efficiency recorded in turning experiment 1i =w1a' i , configuration plan A i The normalized weighted value z of the workpiece surface roughness after turning recorded in the turning experiment 2i =w2b' i w1 and w2 are weights;

[0123] 4) Determine the positive ideal solution and negative ideal solutions After that, calculate configuration plan A i The distance from the normalized weighted value of the chip suction efficiency recorded in the turning experiment and the normalized weighted value of the surface roughness of the workpiece after turning recorded in the turning experiment to the positive and negative ideal solutions

[0124]

[0125] in, is the maximum value of the normalized weighted value of each scrap collection efficiency, is the minimum value of the normalized weighted value of the workpiece surface roughness after each turning process, is the minimum value of the normalized weighted value of each scrap collection efficiency, is the maximum value of the normalized weighted value of the workpiece surface roughness after each turning process;

[0126] 5) Calculate each configuration scheme A i Relative proximity

[0127]

[0128] in, The closer it is to 1, the better the configuration is. i The closer the normalized weighted value of the chip suction efficiency and the normalized weighted value of the workpiece surface roughness after turning are to A + .

[0129] 6) Based on relative proximity The priority of each configuration scheme is arranged in descending order based on the size of the value. The larger the value, the better the configuration scheme, and the optimal configuration scheme is selected.

[0130] like Figure 2 The device, shown in Figure 1, depicts a polytetrafluoroethylene (PTFE) bar material chip suction device, comprising a chip suction pipe 1, a chip suction aperture adjustment assembly 2, and a negative pressure generator. The fluid inlet of the negative pressure generator communicates with the fluid outlet of the chip suction pipe 1, with a screen positioned at the connection point. A chip discharge port is provided on the side of the chip suction pipe 1. The negative pressure generator provides negative pressure, while the chip suction aperture adjustment assembly 2 adjusts the size of the chip suction port, ensuring high-quality and efficient chip suction.

[0131] like Figure 3 、 Figure 4 、 Figure 5 and Figure 6 As shown, the chip suction aperture change component 2 includes an upper cover 202, a driving gear 204, a driven gear 203 and a blade 201. The upper cover 202 is fixed to the chip suction pipe 1, the base of the stepping motor is fixed to the upper cover 202, and the driving gear 204 is fixed to the output shaft of the stepping motor; the driven gear 203 and the upper cover 202 form a rotating pair and mesh with the driving gear 204; a center hole is provided on the hub of the driven gear 203, and the wall of the center hole is provided with n radial grooves uniformly distributed along the circumference. There are n blades 201, and the outer edge of the fluid input port of the chip suction pipe 1 is provided with n branch holes three uniformly distributed along the circumference, where n=12; a support shaft 1 205 is fixed to the branch hole 1 21 provided at one end of the blade 201, and a support shaft 2 is fixed to the branch hole 2 22 provided at the other end, and the support shaft 1 and support shaft 2 are located on different sides of the blade 201; support shaft 1 on each blade and one of the radial grooves form a sliding pair, support shaft 2 on each blade and a branch hole 3 on the chip suction pipe 1 form a rotating pair, and the radial groove and branch hole 3 connected to the same blade are staggered in the circumferential position; the blades 201 are stacked in sequence along the circumferential direction, and the support shaft 1 205 of each blade 201 is placed facing the driven gear 203, and the end of the last blade 201 fixed with support shaft 2 is inserted under the first blade 201 stacked in sequence; the blades 201 enclose a chip suction port, and the center hole of the driven gear 203 hub is connected to the center hole of the upper cover 202 and the chip suction port.

[0132] The working principle of the polytetrafluoroethylene rod material chip suction device is as follows:

[0133] The upper cover 202 is fixed on the machine tool above the workpiece with the chip suction port facing downward; the size of the chip suction port enclosed by each blade 201 is adjusted according to the chip suction port radius and negative pressure in the optimal configuration scheme used during actual turning, and the negative pressure of the negative pressure generating device is set; when adjusting the size of the chip suction port enclosed by each blade 201, the driving gear 204 is driven by a stepping motor to drive the driven gear 203 to rotate, so that the support shaft of each blade 201 slides along the radial groove on the hub of the driven gear 203, and each blade 201 rotates to realize the change in the size of the chip suction port, and the enlargement or reduction of the chip suction port is achieved by changing the direction of the stepping motor.

Claims

1. A chip suction turning method for polytetrafluoroethylene rods, characterized in that: The following steps are involved: Step 1: Predict the chip radius and chip generation rate generated by the polytetrafluoroethylene bar workpiece as follows: 1 / 3 of L from the tip of the knife f The length of the cutting edge is taken as the equivalent force point of the front cutting edge support force, and the chip radius prediction calculation formula is: Among them, E is the elastic modulus of the workpiece material, I is the cross-sectional distance of the chip section, F1 is the equivalent force on the tool rake face, L f is the length of the contact part between the tool and the chip, h is the chip thickness, is the shear angle of the chip, γ is the tool rake angle, τ s is the shear strength of the workpiece material; For turning, the average cutting speed is: Among them, d m is the diameter of the machined surface, d w is the diameter of the surface to be machined; The chip generation rate prediction formula is: Among them, A D represents the cutting area, v av represents the average cutting speed, a p is the depth of cut, f is the feed rate; Step 2: Determine the constraints: Among them, r is the radius of the chip suction port during chip suction, r1 is the chip radius; the minimum negative pressure required inside the chip suction port during chip suction P1 is the ambient atmospheric pressure, ρ is the workpiece material density, and t is the machining time; θ is the angle between the central axis of the chip suction port and the horizontal plane. The chip suction port is located above the workpiece. Step 3: Based on the TOPSIS method and turning experiments, the optimal values ​​of the chip suction port radius and the negative pressure inside the chip suction port are determined as follows: Set the optional values ​​of the chip suction port radius r1, r2, r3, r4, r5 and the optional values ​​of the negative pressure inside the chip suction port p1, p2, p3, p4, p5, and obtain 25 chip suction port radius and negative pressure configuration schemes, thereby obtaining the chip suction port radius and negative pressure configuration scheme set A={A1, A2, ..., A 25 }; Based on the chip suction efficiency η and the surface roughness R of the workpiece after turning a As an indicator, set the average cutting speed v av , feed rate f and back cutting depth a p , under various configuration schemes, the workpiece is turned and the chip suction efficiency and the surface roughness of the workpiece after turning are recorded, and the attribute set B = {η, R a Then, the TOPSIS method was used to select the optimal configuration scheme from the 25 configuration schemes, so as to set the average cutting speed v av , feed rate f and back cutting depth a p When the workpiece is actually turned, the chip suction port radius and negative pressure in the optimal configuration scheme are used to suction the chips.

2. A chip suction turning method for polytetrafluoroethylene rods according to claim 1, characterized in that: Tool rake face equal effect: Among them, τ s is the shear strength of the workpiece material, T is the tool width, h is the chip thickness, is the shear angle of the chip, γ is the tool rake angle; Length of the tool in contact with the chip: The chip cross section is approximated as a rectangle, and the cross-sectional distance of the chip cross section is:

3. The chip suction turning method of polytetrafluoroethylene rod according to claim 1, characterized in that: The minimum negative pressure P required inside the chip suction port when suctioning chips min The solution process is as follows: You must ensure that: F>G′=mgsinθ Among them, F is the suction force of the chip suction port, G' is the component force of the gravity on the chips along the central axis of the chip suction port; Chip mass produced per unit time: m=Qρt Then F=(P1-P)S=(P1-P)πr 2 >Qρtgsinθ have to Among them, P is the negative pressure inside the chip suction port, and S is the area of ​​the chip suction port.

4. A chip suction turning method for polytetrafluoroethylene rods according to claim 1, 2 or 3, characterized in that: The process of selecting the optimal configuration scheme from 25 configuration schemes using the TOPSIS method is as follows: 1) Establish a decision matrix: Among them, a i For configuration plan A i Chip suction efficiency recorded in the turning experiment, b i For configuration plan A i Surface roughness of workpiece after turning recorded in the turning experiment, i = 1, 2, ..., 25; 2) Construct a normalized matrix The chip suction efficiency and surface roughness of the workpiece after turning in the decision matrix are dimensionlessly processed to obtain the normalized decision matrix: Among them, configuration plan A i Normalized value of chip suction efficiency recorded in the turning experiment Configuration Plan A i Normalized value of workpiece surface roughness after turning recorded in the turning experiment 3) Construct a weighted normalized decision matrix: Among them, configuration plan A i Normalized weighted value z of chip suction efficiency recorded in turning experiment 1i =w1a' i , configuration plan A i The normalized weighted value z of the workpiece surface roughness after turning recorded in the turning experiment 2i =w2b′ i w1 and w2 are weights; 4) Determine the positive ideal solution and negative ideal solutions After that, calculate configuration plan A i The distance from the normalized weighted value of the chip suction efficiency recorded in the turning experiment and the normalized weighted value of the surface roughness of the workpiece after turning recorded in the turning experiment to the positive and negative ideal solutions in, is the maximum value of the normalized weighted value of each scrap collection efficiency, is the minimum value of the normalized weighted value of the workpiece surface roughness after each turning process, is the minimum value of the normalized weighted value of each scrap collection efficiency, is the maximum value of the normalized weighted value of the workpiece surface roughness after each turning process; 5) Calculate each configuration scheme A i Relative proximity 6) Based on relative proximity The priority of each configuration scheme is sorted in descending order according to the size of the value, and the The configuration scheme with the largest value is regarded as the optimal configuration scheme.

5. A polytetrafluoroethylene bar chip suction device used in a polytetrafluoroethylene bar chip suction turning method as described in claim 4, comprising a chip suction pipe, a chip suction aperture changing assembly, and a negative pressure generating device; the fluid input port of the negative pressure generating device is connected to the fluid output port of the chip suction pipe, and a screen is provided at the connection point; a chip discharge port is provided on the side of the chip suction pipe; and the characteristics are: The chip suction aperture change component includes an upper cover, a driving gear, a driven gear and a blade; the upper cover is fixed to the chip suction pipe, the base of the stepping motor is fixed to the upper cover, and the driving gear is fixed to the output shaft of the stepping motor; the driven gear and the upper cover form a rotating pair and mesh with the driving gear; a center hole is provided on the hub of the driven gear, and the wall of the center hole is provided with n radial grooves uniformly distributed along the circumferential direction, and n blades are provided, and the outer edge of the fluid inlet of the chip suction pipe is provided with n branch holes uniformly distributed along the circumferential direction, 6≤n≤12; a branch hole at one end of the blade is fixed with a support shaft, and the other end is provided with a support shaft. A support shaft 2 is fixed at the second branch hole, and the support shaft 1 and the support shaft 2 are located on different sides of the blade; the support shaft 1 on each blade and one of the radial grooves form a sliding pair, and the support shaft 2 on each blade and a branch hole 3 on the chip suction pipe form a rotating pair, and the radial groove and branch hole 3 connected to the same blade are staggered in the circumferential position; the blades are stacked in sequence along the circumference, and the support shaft 1 of each blade is placed facing the driven gear, and the end of the last blade fixed with the support shaft 2 is inserted under the first blade stacked in sequence; the blades enclose a chip suction port, and the center hole of the driven gear hub is connected to the center hole of the upper cover and the chip suction port.

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