CN114161095A

CN114161095A - Clamping method for engineering plastic long pipe thin-wall part

Info

Publication number: CN114161095A
Application number: CN202111614315.1A
Authority: CN
Inventors: 刘宏; 于峰; 冯靖华; 杨景捷; 岳菊; 雷勇; 张菊亚
Original assignee: Csic Xi'an Dong Yi Science Technology & Industry Group Co ltd
Current assignee: Csic Xi'an Dong Yi Science Technology & Industry Group Co ltd
Priority date: 2021-12-27
Filing date: 2021-12-27
Publication date: 2022-03-11

Abstract

The invention provides a clamping method for an engineering plastic long pipe thin-wall part, which comprises the following steps: firstly, carrying out rough machining on an engineering plastic bar to obtain a rough blank; step two, carrying out aging treatment on the rough blank to obtain a blank piece; step three, loading the blank into an elastic self-centering mould, and finely boring an inner hole; and (3) taking the friction mandrel to be assembled in the inner hole of the blank, clamping the friction mandrel, and turning the outer circle of the blank. In the production of long-tube thin-wall parts, a friction mandrel and an elastic self-centering clamping fixture are adopted, and reasonable processes, tools, cutting parameters and material stabilizing treatment measures are adopted, so that the problems of poor rigidity and easy deformation of the engineering plastic long-tube thin-wall parts are well solved; the parts produced by the clamping method have stable geometric shape and linear dimension, and the production efficiency and the product percent of pass are greatly improved.

Description

Clamping method for engineering plastic long pipe thin-wall part

Technical Field

The invention belongs to the field of machining processes, and particularly relates to a clamping method for an engineering plastic long pipe thin-wall part.

Background

The engineering plastic has high rigidity, small creep deformation, high mechanical strength, high temperature resistance, high impact resistance and high insulating property, can be used in harsh chemical and physical environments for a long time, and can be widely applied to military products and civil products more and more as the preparation technology of the engineering plastic is developed and matured on the basis, the high-performance high-polymer engineering plastic such as nylon, ABS, polytetrafluoroethylene, polyformaldehyde, hard polyvinyl chloride and the like replaces metal materials.

Compared with the radial and axial dimensions, the wall thickness of the engineering plastic long-pipe thin-wall part has great difference, so the rigidity is poor, particularly under the action of cutting force, clamping force and residual stress, vibration ripple, vibration deformation and thermal deformation are easy to generate, and the size precision, the form and position precision and the surface roughness of the part are influenced, wherein the deformation caused by the clamping force is mainly caused by a clamping mode, and the clamping deformation of the long-pipe thin-wall part mainly comprises the following steps:

a. deformation of cross section at the clamping position

The excircle of the long tube thin-wall part is clamped by a three-jaw chuck, a copper three-jaw chuck and an elastic chuck, the part is unloaded after turning, and the clamped part of the clamped part is expanded due to elastic deformation, so that the section of the clamped part of the part is deformed in a triangular shape. The primary direction of deformation is deformation normal to the work surface. The inner hole is measured by the plug gauge, the gap between the measuring tool and the inner hole is obviously enlarged from the through end to the deformation part, and the errors of the actual size, the surface roughness, the roundness, the straightness, the jumping and the like of the part are larger.

b. The inner hole processing surface is a vibration ripple

Under the action of cutting force, especially radial cutting force, the long-tube thin-wall part is easy to vibrate and deform due to insufficient rigidity of the thin-wall part, and meanwhile, the inner hole is machined to have annular ripple defects; in addition, due to the long-tube deep hole, the length-diameter ratio of the tool for boring the inner hole is too large, and the tool is always shaken during the deep hole boring, so that the deep hole taper error is large.

c. Is deformed by heat

The long pipe thin-wall part has poor heat dissipation performance and large linear expansion coefficient of engineering plastics, and continuous turning after one-time clamping tends to generate a large amount of cutting heat, so that the part generates thermal deformation and the dimensional precision of the part is reduced; especially, in order to solve the problem of rigid support, the clamping surface of the clamp is large, and parts deformed by heating are clamped on the clamp even because of serious deformation.

d. Non-uniform wall thickness

If the long-pipe thin-wall part is rigidly positioned, the relative position of the part, the clamp, the cutter and the rotation center of the machine tool spindle is easily adjusted inaccurately, the error is large, and the geometric shape change and the uneven wall thickness of the part are easily caused.

Disclosure of Invention

The invention aims to provide a method for clamping an engineering plastic long pipe thin-wall part, which overcomes the technical defects.

In order to solve the technical problem, the invention provides a clamping method of an engineering plastic long pipe thin-wall part, which comprises the following steps:

firstly, carrying out rough machining on an engineering plastic bar to obtain a rough blank;

step two, carrying out aging treatment on the rough blank to obtain a blank piece;

step three, loading the blank into an elastic self-centering mould, and finely boring an inner hole;

and (3) taking the friction mandrel to be assembled in the inner hole of the blank, clamping the friction mandrel, and turning the outer circle of the blank.

Further, the first step is to rough process the engineering plastic bar to obtain a rough blank, which comprises the following steps:

step 101, the incoming materials of engineering plastic bars are regular, and the outer circle is used as a reference for machining a roughly bored inner hole;

102, turning a flat end face, and centering by using a center drill;

103, drilling and reaming, wherein the hole depth exceeds the total cutting length by at least 2mm, and forming a through hole after cutting;

104, roughly boring an inner hole to a depth size, and assembling a positioning mandrel, wherein the clearance between the positioning mandrel and the boring hole is 0-0.02 mm;

105, clamping a positioning mandrel, installing a tip on a tailstock of a machine tool, shaking out the tip, and tightly pushing the end face of the part;

and step 106, turning the outer circle to a rough turning size to obtain a rough blank.

Further, the aging treatment is carried out on the two pairs of rough blanks to obtain blank pieces, and the method comprises the following steps:

and vertically placing the rough blank on a turnover box or a flat plate for not less than 48 hours.

Further, step three, the blank piece is loaded into an elastic self-centering clamping fixture, and an inner hole is finely bored, and the method comprises the following steps:

step 301, assembling a blank in an elastic self-centering mould, and clamping the elastic self-centering mould by a copper three-jaw or three-jaw chuck;

302, finely boring an inner hole of the blank to a depth size of less than 0.2mm and an inner diameter size of the inner hole;

and 303, turning the working end surface of the blank piece, and reversely cutting the bottom of the inner hole by using a cutter after the turning is finished.

Furthermore, the elastic self-centering mould is a revolving body part made of brass and comprises a hollow columnar supporting sleeve, a hollow inner cavity of the supporting sleeve is used as a matching hole for assembling a blank piece, and the outer wall of the supporting sleeve is divided into a large-diameter end and a small-diameter section according to the outer diameter;

four equal parallel to axial centerline's slots are seted up to the outer wall of support cover, and four slots are evenly spaced along circumference, and wherein two slots are 180 and distribute and all extend to little diameter section until cooperation hole depth 2/3 department from major diameter end, and two other slots are 180 and distribute and equally distribute in little diameter section until cooperation hole depth 1/3 department.

Further, step three is got the friction dabber and is assembled in the blank downthehole, centre gripping friction dabber, turning blank excircle, includes:

step 304, taking the finely bored inner hole of the step 302 as a reference for finely turning an outer circle, and assembling a friction mandrel;

305, clamping one end surface of the friction mandrel by a copper three-jaw or three-jaw chuck, and tightly pushing the other end surface by a tailstock center of a machine tool;

and step 306, turning the outer circle to obtain the engineering plastic long pipe thin-wall part.

Furthermore, the friction mandrel is divided into two sections, namely a first diameter section and a second diameter section, wherein the diameter of the first diameter section is larger than that of the second diameter section, the first diameter section consists of a knurled section and a polished rod section, and the first diameter section has a taper;

the end surface of the second diameter section is provided with a tip hole.

Further, in the rough machining stage of the first step, after the end face is turned, the outer circle is roughly turned, the allowance of the inner hole is remained by 0.5mm, then an annular groove is turned on the outer circle, the bottom diameter of the annular groove is larger than the diameter of the inner hole, then the outer circle and the inner hole are semi-finished to the rough turning size, and finally cutting is carried out along the annular groove.

Furthermore, all turning procedures in all steps need to be brushed with cold water for cooling, cooling water is increased in the fine machining stage in the step three, and chips are pulled out by a hook in time;

and the aging treatment of the second step is to vertically place the parts in a turnover box filled with purified water, wherein the purified water submerges the parts.

The invention has the following beneficial effects:

(1) in the fine machining stage, a part is arranged in an elastic self-centering clamping fixture, a copper three-jaw or high-precision elastic chuck clamps the outer circle of the elastic self-centering clamping fixture, the clamping fixture is uniformly contracted by a fan-shaped clamping jaw, the part is completely clamped, the part and the copper clamping fixture are wrapped into a whole, the clamping force is uniformly distributed on the part, and the problems of poor rigidity and large deformation of the engineering plastic long-pipe thin-wall part are solved.

(2) When smart car excircle, conventional dabber often receives axial pressure, and elastic deformation easily appears in the part, and the friction dabber that this application provided is used for the clamping part, and the part does not receive axial clamping force during the turning, only leans on the frictional force between friction dabber and the part hole to provide clamping force, and excircle and hole follow type processing do not have axial deformation, and the shaping back wall thickness is even, stable in size, axiality precision is high.

(3) In the production of the long-tube thin-wall part, the friction mandrel and the elastic self-centering clamping fixture are adopted, and reasonable processes, tools, cutting parameters and material stabilizing treatment measures are combined, so that the problems of poor rigidity and easy deformation of the engineering plastic long-tube thin-wall part are well solved, the geometric shape and linear size of the produced long-tube thin-wall part are stable, and the production efficiency and the product percent of pass are greatly improved.

In order to make the aforementioned and other objects of the present invention comprehensible, preferred embodiments accompanied with figures are described in detail below.

Drawings

Fig. 1 is a front view of a resilient self-centering tire.

Fig. 2 is a half sectional view of the elastic self-centering positioner.

Fig. 3 is a schematic structural view of the friction mandrel.

Fig. 4 is a schematic view of the structure of the launch tube.

Fig. 5 is a schematic view of the launch tube at the rough turn stage.

Fig. 6 is a schematic view of the launch tube at the finishing stage.

Description of reference numerals:

1. a support sleeve; 2. slotting; 3. a large diameter end; 4. a small diameter section; 5. a knurling section; 6. a light pillar segment; 7. a tip hole; 8. positioning the mandrel; 9. a tailstock center.

Detailed Description

The following description of the embodiments of the present invention is provided for illustrative purposes, and other advantages and effects of the present invention will become apparent to those skilled in the art from the present disclosure.

In the invention, the upper, lower, left and right in the drawings are regarded as the upper, lower, left and right of the clamping method for the engineering plastic long pipe thin-wall part described in the specification.

The exemplary embodiments of the present invention will now be described with reference to the accompanying drawings, however, the present invention may be embodied in many different forms and is not limited to the embodiments described herein, which are provided for complete and complete disclosure of the present invention and to fully convey the scope of the present invention to those skilled in the art. The terminology used in the exemplary embodiments illustrated in the accompanying drawings is not intended to be limiting of the invention. In the drawings, the same units/elements are denoted by the same reference numerals.

Unless otherwise defined, terms (including technical and scientific terms) used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this invention belongs. Further, it will be understood that terms, such as those defined in commonly used dictionaries, should be interpreted as having a meaning that is consistent with their meaning in the context of the relevant art and will not be interpreted in an idealized or overly formal sense.

The long-tube thin-wall part can be a part with the length-diameter ratio of more than or equal to 10, and can also be defined by other definitions without limitation.

Part clamping conditions are as follows: because the rigidity of the long-pipe thin-wall part is poor, additional stress is caused if the action points of the clamping force and the supporting force are not proper during processing, and therefore the elastic deformation of clamping and pressing affects the size precision and the position precision of the surface of the part to a certain extent, and deformation is caused.

Processing residual stress: in the machining process of the part, new residual stress appears in the surface layer of the part due to the combined action of extrusion of a cutter on a machined surface, friction between a front cutter surface and chips of the cutter, friction between a rear cutter surface and the machined surface and the like. Due to the existence of unstable residual stress, once the part is subjected to external force, local plastic deformation is generated under the action of the external force and the residual stress, and the stress in the section is redistributed. After the external force is removed, the part can deform under the action of internal residual stress, so that the processing quality is seriously influenced.

Cutting force, cutting heat, and cutting vibration: elastic deformation and plastic deformation of the part and friction between the part and a cutter and cutting chips, cutting force and cutting heat are generated in the cutting process, and under the action of the elastic deformation and the plastic deformation and the friction between the part and the cutter and the cutting chips, the vibration and the deformation of the part are easily caused, and the quality of the part is further influenced.

On the basis of the factors and the principle which influence the processing quality of the engineering plastic long pipe thin-wall part, the embodiment provides a clamping method of the engineering plastic long pipe thin-wall part, which comprises the following steps:

The rigidity of the long-tube thin-wall part is poor, and the part is easily deformed under the influence of cutting force, clamping force, cutting force and residual stress in the turning process, so that the whole clamping rigidity of the part in the machining process is improved by clamps such as a friction core shaft, an elastic self-centering clamping fixture and the like.

The triangular deformation of the thin-walled part is mainly caused by radial clamping force, and the drum deformation is mainly caused by axial force. When the outer circle of the finished automobile is formed, the conventional mandrel usually bears axial pressure, and elastic deformation easily occurs to parts. Friction dabber clamping part, the part does not receive axial clamping-force during the turning, only provides clamping-force by the frictional force between friction dabber and the part hole, and excircle and hole are along with the type processing, and no axial deformation, wall thickness is even after the shaping, stable in size, axiality precision are high, and the structure of friction dabber is as follows:

referring to fig. 3, the friction mandrel is divided into two sections, namely a first diameter section and a second diameter section, wherein the diameter of the first diameter section is larger than that of the second diameter section, the first diameter section is composed of a knurled section 5 and a polished rod section 6, the first diameter section has a taper, and a tip hole 7 is formed in the end face of the second diameter section.

In fig. 3, a triangle symbol indicates a taper direction of the first diameter section, and a symbol like a v-shape indicates that the clamping is performed.

Specifically, the friction mandrel is a small-taper step mandrel, a tip hole 7 is reserved on the end face of the small end (the end face of the second diameter section), and the diameter difference between the large end and the small end of the part matched with the deep hole is 0.02-0.03 mm; the matching part (the first diameter section) consists of a knurled section 5 and a light beam section 6, and the length of the knurled section is about 40% of the length of the matching part (the first diameter section); when the excircle is turned, the friction mandrel is clamped by the copper three-jaw or high-precision elastic chuck, after the mandrel is aligned by the dial indicator, the part is arranged in the friction mandrel, the smooth column section 6 of the friction mandrel is in small clearance fit with the deep hole to play a role in positioning and supporting, the knurled section 5 is in transition fit with the deep hole, and the rough knurled surface and the inner hole are extruded to generate friction force during cutting, so that the position of the part relative to the mandrel is kept unchanged.

According to the part of actual processing, the structure of friction dabber can be diversified, is equipped with annular boss in the middle section of friction dabber for example, and the purpose is convenient for dabber axial positioning.

When the deep hole is finely bored, the common soft claw is used for clamping, the clamping surface can generate slight elastic deformation, after the deep hole is bored and formed, the part is not disassembled, the measurement is carried out on a machine tool, the diameter and the roundness meet the requirements, the part is disassembled to be measured in a free state, the radial dimension of the clamping surface is obviously larger, and the clamping surface is drum-shaped, the elastic self-centering clamping fixture of the embodiment can solve the problem, and the structure of the elastic self-centering clamping fixture is as follows:

referring to fig. 1 and 2, the rotary body part made of brass comprises a hollow columnar support sleeve 1, a hollow inner cavity of the support sleeve 1 is used as a matching hole for assembling a blank, and the outer wall of the support sleeve 1 is divided into a large-diameter end 3 (the end face of a peripheral step is used as a clamped axial positioning face) and a small-diameter section 4 (the inner cavity is used for assembling a part to be processed) according to the outer diameter; four equal parallel to axial centerline's slots 2 are seted up to the outer wall of support cover 1, and four slots 2 are along circumference evenly spaced, and wherein two slots 2 are 180 and distribute and all extend to little diameter section 4 until cooperation hole depth 2/3 department from big diameter end 3, and two other slots 2 are 180 and distribute and equally distribute in little diameter section 4 until cooperation hole depth 1/3 department.

Specifically, in the finish machining stage, because the part wall is thin, can't exert the clamp force at the terminal surface during processing hole, can only the centre gripping excircle, the clamping face should be as big as possible during consequently processing hole, and clamping-force is even, on this basis, elasticity is from the hole of centering mould and the little clearance fit of part, and the degree of depth slightly is less than part length, adopts wear-resisting and the good brass material of elasticity, and wall thickness 2mm guarantees existing enough rigidity, again can elastic deformation.

Referring to fig. 1 and 2, one end of the elastic self-centering clamping fixture is axially cut through the center by using a wire cutting machine to reach the depth 2/3 of the matching hole; the other end of the fixture is axially split over the center at 90 deg. to the mating hole depth 1/3. When the clamping fixture is used, parts are arranged in the clamping fixture, the copper three-jaw or high-precision elastic chuck clamps the excircle of the clamping fixture, and the clamping length is 1/2 which is greater than the length of the clamping fixture. Four slots 2 on the mould (extend to the little diameter section 4 from big diameter end 3 and reach cooperation hole depth 2/3 department to and extend to cooperation hole depth 1/3 department from the little diameter end) are evenly contracted after being centre gripping by fan-shaped clamping jaw, and the whole section holomorphic clamping part, part and copper mould parcel are integrative, and the clamp force evenly distributed has solved poor, the big problem of deformation of rigidity on the part.

The emission tube is a typical long tube thin-wall part, the material is polyformaldehyde, the emission tube (see fig. 4) is used as a target part to be processed, the processing technology is to perform rough turning and fine turning separately, and the processing steps are as follows:

step one, rough machining is carried out on an engineering plastic bar to obtain a rough blank, and the method comprises the following steps:

102, turning a flat end face, and centering by using a center drill;

The supplied materials of the polyformaldehyde rod are regular, and the outer circle can be directly used as the reference for machining the rough boring inner hole; after the end face is turned, centering by a central drill, drilling a hole with the diameter phi 5, reaming to the diameter phi 10 (a hole at the right end in the figure 5), wherein the hole depth exceeds the total cutting length by at least 2mm, and forming a through hole after cutting; boring a hole with phi 16 to a depth dimension (a left end hole in the figure 5) with a tolerance H12, paying attention to the fact that the consistency of radial dimension errors of the phi 16 is not more than 0.04mm, facilitating rough turning reference of a subsequent outer circle, assembling a positioning mandrel 8, positioning with an orifice end face and an inner hole face of the phi 16 as shown in the figure 5, and matching the positioning mandrel 8, wherein the gap between the positioning mandrel 8 and the phi 16 inner hole is 0-0.02 mm; a tailstock of the machine tool is provided with a centre, and a tailstock centre 9 is shaken out to tightly push a phi 10 hole; the outer circle is turned to the rough turning size phi 24, the consistency of the radial size error of phi 24 is not more than 0.03mm, and the finish turning reference of the subsequent inner hole processing is facilitated.

And in the rough machining stage, finishing allowance of 1mm is left on the single side in the radial direction of the inner hole and the outer circle.

And in the rough turning stage, after the end face is turned, roughly turning the outer circle and the inner hole with the allowance of 0.5mm, turning an annular groove on the outer circle according to the length of the part, paying attention to the fact that the bottom diameter of the annular groove is larger than the diameter of the inner hole, then semi-finishing the outer circle and the inner hole to the rough turning size, and finally cutting along the annular groove. The ring groove is pre-cut, so that external stress generated by uneven clamping force is released, and the stress deformation of parts is small and close to a free state during semi-finish turning; after the vehicle is broken, the elastic deformation of the parts is small, and the size and shape precision is ensured.

And step two, carrying out aging treatment on the rough blank to obtain a blank piece, wherein the aging treatment comprises the following steps:

polyformaldehyde aging treatment mainly aims at removing material residual stress to stabilize dimensional accuracy, and the transmitting tube adopts natural aging treatment, namely, the roughly machined parts are vertically placed on a turnover box or a flat plate and are placed for not less than 48 hours. The launching tube is a thin-wall part, and in the aging treatment process, if the launching tube is horizontally placed or randomly placed, the part can deform due to the fact that the part is weak in rigidity, self weight or slight external force, and internal stress caused by nonuniformity of thermal expansion and cold contraction. Therefore, the direction of heat treatment deformation needs to be paid attention to in the aging process of the long-tube thin-wall part so as to reduce the placing mode of heat treatment deformation. The natural aging stress is released slowly, the production period needs to be reasonably arranged in production, the aging time is ensured, and the aging time is prolonged as far as possible.

In addition, the polyformaldehyde part is not easy to dissipate heat in the machining process, the size of the part is changed greatly when the part is heated, and not only elastic deformation but also plastic deformation is generated when the part is overheated. In order to reduce the cutting heat generated in the machining process, cold water is sprayed and brushed on the part for cooling during the turning process, especially in the finish machining stage, the cooling water is increased, chips are pulled out by a hook in time, and the winding and the friction on the inner wall of the part are avoided. Stress should be released in the process, and the parts can be vertically placed in a plastic turnover box filled with purified water, wherein the purified water passes through the parts. The material tissue can be stabilized by adopting cold water soaking, and the size change is reduced.

Step three, loading the blank into an elastic self-centering mould, finely boring an inner hole, taking a friction mandrel to be assembled in the inner hole of the blank, clamping the friction mandrel, and turning the excircle of the blank, wherein the method comprises the following steps of:

During finish machining, the rigidity of the part is reduced along with the gradual reduction of the wall thickness of the part, and before final finish turning, the three claws can be loosened to restore the deformation of the part and then slightly clamp and turn the part to the final size.

When the launching tube is machined, the wall thickness of a part is 2mm in a finish machining stage, the part is poor in rigidity and extremely easy to deform, and ripples and uneven sizes are easy to occur in turning. In order to enhance the rigidity of the part, when an inner hole is finely bored, the part is clamped by using an elastic self-centering clamping fixture, and the radial run-out error of a copper three-jaw or three-jaw chuck is not more than 0.02 mm; when the polyformaldehyde thin wall is turned, under the action of turning force, a material extends along the feeding direction of a cutter, namely, the material axially, so that the depth of a boring inner hole can not reach a drawing (meaning that the drawing size can not be reached), and is less than 0.2mm of the drawing size, namely, the depth allowance is required to be reserved for 0.2mm in actual turning shown in figure 6, namely, the depth of the inner hole is supposed to be Xmm according to the drawing size, the machining depth is only required to be (X-0.2) mm in actual machining, and after a size chain is converted, the machining is reserved for the next procedure, and the thickness of a sealing surface (particularly a transmitting tube) is ensured.

Turning the deep hole to phi 18mm, clamping the part by using an elastic self-centering clamping fixture, turning the part of the sealing surface, and reversely cutting the bottom of the phi 18mm hole by using a cutter after the part is turned, so as to ensure the thickness of the sealing surface; and (3) taking a deep hole with the diameter of 18mm as the reference of the finish turning excircle, and assembling a friction mandrel. The three-jaw chuck or the copper three-jaw clamps one end of the friction mandrel, and the tailstock center 9 tightly pushes the other end. The clamping is carried out by taking the friction force of the mandrel and the deep hole as the clamping force, the radial and axial clamping force is not generated, the outer circle and the inner hole of the part are in a coaxial state, and the wall thickness is uniform after the outer circle is turned.

The long pipe thin-wall part has high requirements on the size precision and the roundness, the machining size range of the machine tool is adapted to the overall size of the part, and the angle of the machine tool, which is adapted to the working precision and the working procedure requirements, is selected by the lathe. And (3) processing by using a high-precision instrument lathe or a high-precision small numerical control lathe. The clamping force needs to be strictly controlled during turning, so that the spindle clamping device adopts manual clamping and does not use pneumatic clamping or hydraulic clamping; when the part is manually clamped, an operator needs to loosen and clamp the part for many times and grope the hand feeling experience, so that the part can be reliably turned, the clamping force can be reduced as much as possible, and the balance between clamping and turning is achieved.

Preferably, a lathe with a tailstock center is selected, and in order to ensure that the wall thickness is uniform, the coaxiality error of the inner hole and the outer circle and the coaxiality error of the lathe center and the main shaft are not more than 0.02 mm.

The long pipe and the deep hole are measured by using a plug gauge matched with the tolerance of the aperture size, and the long pipe and the deep hole are not measured by using a caliper. The length of the measuring jaw of the caliper is limited, the whole section of the aperture cannot be measured, and the cylindricity and the straightness of the inner hole are difficult to accurately measure; the plug gauge can measure the diameter of the deep hole in a full-scale manner, and whether an inner hole is in a bell mouth shape or not can be easily found.

Sealed face thickness dimension is because being in the deep hole bottom, can't directly use slide caliper rule or scale measurement, should use and measure dabber auxiliary measurement, specifically is: measuring the clearance fit between the mandrel and a phi 18mm deep hole, wherein the mandrel is slightly longer than the hole, and the parallelism of two end surfaces of the mandrel is not more than 0.01 mm; and (3) placing the measuring mandrel into a part, abutting against a 90-degree working surface of the V-shaped iron, calculating a size block gauge according to a theory of the total length from the end surface of the measuring mandrel to the end surface of the part, measuring the height by using a dial indicator to obtain the actual measurement size of the total length L, and subtracting the length size L1 of the measuring mandrel to obtain the thickness size delta of the sealing surface.

The production efficiency and the dimensional stability can be improved by reasonably selecting the geometric angle and the cutting amount of the cutter. In the rough machining stage, the back tool feeding amount and the feed amount can be larger; in the finishing stage, the back cutting depth is generally 0.1-0.3 mm, the feed rate is generally 0.1-0.2 mm/r, and if necessary, the feed rate can be smaller, and finishing processing is performed. The cutting speed is moderate during rough cutting, and the cutting speed is matched with the diameter of a part, the material of a cutter and the angle. And the cutting speed is increased as much as possible during finish turning, and the surface roughness of the part is improved. The cutting depth and the feed amount are not too large, otherwise, the parts are easy to generate the phenomenon of 'knife binding' due to slight vibration. The sharp turning tool with a larger main deflection angle, a slightly larger front angle and a smaller arc radius of the tool tip is adopted, so that the cutting force during turning can be reduced, and the deformation of parts is reduced.

The parts refer to engineering plastic long pipe thin-wall parts in different processing stages.

It will be understood by those of ordinary skill in the art that the foregoing embodiments are specific examples for carrying out the invention, and that various changes in form and details may be made therein without departing from the spirit and scope of the invention in practice.

Claims

1. A clamping method for an engineering plastic long pipe thin-wall part is characterized by comprising the following steps:

2. The method for clamping the engineering plastic long pipe thin-wall part as claimed in claim 1, wherein the step one of rough machining the engineering plastic bar to obtain a rough blank comprises:

102, turning a flat end face, and centering by using a center drill;

3. The method for clamping the engineering plastic long pipe thin-wall part as claimed in claim 1, wherein the aging treatment of the rough blank in the second step to obtain the rough blank comprises the following steps: and vertically placing the rough blank on a turnover box or a flat plate for not less than 48 hours.

4. The method for clamping the engineering plastic long pipe thin-wall part as claimed in claim 1, wherein the step three of loading the blank into the elastic self-centering clamping fixture and finely boring the inner hole comprises the following steps:

5. The method for clamping the engineering plastic long pipe thin-wall part as claimed in claim 1 or 4, wherein the elastic self-centering mold is a rotary part made of brass and comprises a hollow columnar supporting sleeve (1), the hollow inner cavity of the supporting sleeve (1) is used as a matching hole for assembling a blank piece, and the outer wall of the supporting sleeve (1) is divided into a large-diameter end (3) and a small-diameter section (4) according to the outer diameter;

four equal parallel to axial centerline's slots (2) are seted up to the outer wall of supporting cover (1), and four slots (2) are along circumference evenly spaced, and wherein two slots (2) are 180 and distribute and all extend to little diameter section (4) until cooperation hole depth 2/3 department from big diameter end (3), and two other slots (2) are 180 and distribute and equally distribute in little diameter section (4) until cooperation hole depth 1/3 department.

6. The method for clamping the engineering plastic long pipe thin-wall part as claimed in claim 4, wherein the step three of taking the friction mandrel to fit in the inner hole of the blank, clamping the friction mandrel, and turning the outer circle of the blank comprises:

7. The method for clamping the engineering plastic long pipe thin-wall part as claimed in claim 1 or 6, wherein the friction mandrel is divided into two sections, namely a first diameter section and a second diameter section, wherein the diameter of the first diameter section is larger than that of the second diameter section, the first diameter section is composed of a knurled section (5) and a smooth column section (6), and the first diameter section has a taper;

the end surface of the second diameter section is provided with a tip hole (7).

8. The method for clamping the engineering plastic long pipe thin-wall part as claimed in claim 2, wherein in the rough machining stage of the step one, after the end face is turned, the outer circle is roughly turned and the inner hole is roughly bored with a margin of 0.5mm, then an annular groove is turned on the outer circle, the bottom diameter of the annular groove is larger than the diameter of the inner hole, then the outer circle and the inner hole are semi-finished to the rough turning size, and finally the part is cut along the annular groove.

9. The method for clamping the engineering plastic long pipe thin-wall part as claimed in claim 3, wherein the turning process of all the steps is to brush cold water on the part for cooling, the cooling water is increased in the finishing stage of the third step, and the chips are pulled out by a hook in time;