CN104550393B - A kind of high-fineness ratio band concave bottom thin-wall tube-shaped element accurate forming method - Google Patents

Abstract

The open a kind of high-fineness ratio band concave bottom thin-wall tube-shaped element accurate forming method of the present invention.The method first calculates the size of slab, carries out concave bottom part shaping the most successively, draw spinning becomes cylindrical blank, spinning to be thinned to given size；Follow-up general processing, meets accessory size requirement；Wherein draw spinning becomes cylindrical blank to be the blank upset after being shaped by concave bottom, it is fixed between tail top and core, general rotation track is worked out according to conventional spinning track preparation method, main shaft drives blank to rotate, spinning roller, under the driving of digital control system, carries out feeding by the track worked out, and front 68 passages of spinning track are simple spinning toward open end, it is followed by the spinning track that roundtrip combines, blank draw spinning is become cylindrical member；The present invention utilizes multi-process draw-spinning to obtain tubular blank, then uses spinning to be thinned to given size, utilizes the high-precision feature of shear spinning simultaneously, and product uniform wall thickness, surface quality height, good compactness, defect are few.

Description

A kind of high-fineness ratio band concave bottom thin-wall tube-shaped element accurate forming method

Technical field

The present invention relates to a kind of machine parts'precise manufacturing process, be specifically related to the accurate forming method of Thin Walled Curved mother's shape part of a kind of band concave bottom, belong to mechanical plastic processing method.

Background technology

Concave bottom refers to feature bottom, and some is similar to the bottom of " volcanic crater " shape less than peripheral region, formation.High-fineness ratio cylindrical member refers to that the length-to-diameter of cylindrical member is more than or equal to 1.5.Owing to tradition deep-drawing technique forming limit is limited；All the time, the manufacturing process of the thin-wall tube-shaped element of high-fineness ratio band concave bottom is: the bent bus part of band concave bottom uses mould drawing and forming, direct tube section part uses volume weldering, carries out assembly welding after sectional forming again, but owing to the existence of welding residual stress makes the dimensional accuracy of part be difficult to meet requirement；Additionally, due to the easy embrittlement of weld seam and stress concentrate the source often becoming cracks can spread, have a strong impact on the quality of product.Volume postwelding is because of the existence of weld seam and welding deformation simultaneously, needs to carry out substantial amounts of artificial follow-up polishing and school shape, the most seriously reduces production efficiency, adds production cost, and have influence on dimensional accuracy and the form and position tolerance of drip molding.

Spinning is by mean of the feed motion of spinning roller, stresses on the metal blank rotated with core along same axis so that it is produces the deformation of continuous print partial mold and becomes a kind of near net precision plastic forming method of required hollow parts.The most only change blank shape and do not change the referred to as conventional spinning of wall thickness, not only change the shape of blank, and significantly change the referred to as shear spinning of its wall thickness.Traditional spin forming technique, as limited in conventional spinning forming limit, and due to resilience, forming accuracy is the highest；Shear spinning can only shape Tapered Cup and cylindrical member, but forming accuracy is higher.

Summary of the invention

It is an object of the invention to the shortcoming overcoming above-mentioned prior art, it is provided that a kind of high accuracy, high-performance, the high-fineness ratio band concave bottom thin-wall tube-shaped element spin forming method of low cost.

The combined shaping method that conventional spinning and two kinds of spin forming methods of shear spinning are combined by the present invention, solves high-fineness ratio band concave bottom thin-wall tube-shaped element high accuracy, high-performance, a difficult problem for low cost manufacture.

For realizing above-mentioned target, the present invention adopts the following technical scheme that

A kind of high-fineness ratio band concave bottom thin-wall tube-shaped element accurate forming method, comprises the steps:

1) size of slab is calculated

Shape according to part, size, deformation distribution principle in shaping according to constancy of volume principle and composite spinning, determine the size of blank, including diameter and the thickness of blank；Wherein the diameter control of blank is at cut off diameter D_tIn；D_t=d/m_t；m_tFor limit drawing coefficient, d is core diameter；

2) concave bottom part shapes

Being clamped in by blank between core and tail top, determine the spinning track shaping concave bottom cylindrical portion according to the preparation method of conventional spinning track, during concave bottom part mould pressing, front 13 passages are conventional spinning, and Roller locus is circular arc track；Thereafter every time comprises conventional spinning and shear spinning, and its Roller locus comprises two parts, and front portion is the track during shear spinning being parallel to bottom concave bottom axis, and making every time reduction is 10 25%, and rear portion is circular arc track during conventional spinning；Every time starting point revolving by force track is blank end face, and terminal is the starting point of the general rotation track according to the establishment of conventional spinning track, and the terminal of conventional spinning track is determined by formula (9), and last passage spinning track is the contour line of concave bottom part；

D'=D₀{1-[1-(d/D₀)²]X²/h²}^1/2 (9)

In formula: D₀For blank diameter, d is core diameter, and h is workpiece height；

3) draw spinning becomes cylindrical blank

Blank upset after concave bottom is shaped, it is fixed between tail top and core, general rotation track is worked out according to conventional spinning track preparation method, main shaft drives blank to rotate, spinning roller, under the driving of digital control system, carries out feeding by the track worked out, and front 68 passages of spinning track are simple spinning toward open end, it is followed by the spinning track that roundtrip combines, blank draw spinning is become cylindrical member；

4) spinning is thinned to given size

Bottom circular arc shaped portion uses circular arc spinning roller drawing attenuated, it is ensured that every time reduction is 20% 25%；Straight drum part uses double tapered roller, it is ensured that every time reduction is 20% 35%；

5) following process, meets accessory size requirement.

Further, described limit drawing coefficient is by diameter wrinkle resistant and blank when not rupturing during test blank draw spinning.

3, high-fineness ratio band concave bottom thin-wall tube-shaped element accurate forming method according to claim 1, it is characterised in that described simple spinning toward open end is that spinning roller stresses on blank, along the direction feeding away from rotation centerline.

The spinning track that described roundtrip combines is that spinning roller stresses on blank, first along the direction feeding away from rotation centerline, feeding the most in opposite direction.

Described step 2) and 3) in the preparation method of conventional spinning track: first determine suitable involute path during conventional spinning, subsequently involute path fitted to the circular arc line curve through Roller locus beginning and end.

Described involute base radius a determines according to core diameter d: d/a >=0.3 (3)

Step 1) in the explanation of deformation distribution principle: when using composite spinning to shape, after concave bottom mould pressing, need to first use multi-process draw-spinning operation that slab is made cylindrical member, then shear spinning operation is used to make its wall thickness reduction to given size, in multi-process draw-spinning, core diameter d and blank diameter D₀Ratio be referred to as spinning Coefficient m, for each material, its plastic deformation degree all can have certain limit, thus the spinning coefficient of each material necessarily has a minimum limit value, referred to as limit drawing coefficient (m_t).By test, it is thus achieved that aluminum and aluminium alloy, the limit spinning coefficient of 3mm and 4mm slab is 0.45 and 0.5.

During multi-process draw-spinning, for given core diameter, the carrying out that spinning to be made is stable, not producing the defects such as flange wrinkle, its blank diameter has a critical maximum (D_t)。

$D_t=\frac{d}{m_t}$

During multi-process draw-spinning, the diameter (D of blank₀) should meet following relation:

D₀≤D_tOr m₀≥m_t (1)

During multi-process draw-spinning, blank has a certain degree of thinning, uses Ψ₁Represent the wall thickness reduction of blank after draw spinning.For mild steel, aluminum and aluminium alloy, wall thickness reduction Ψ during multi-process draw-spinning₁=10%～15%.

Total reduction Ψ during shear spinning_tFollowing relation: Ψ should be met_t≥Ψ₁ (2)

Formula (1), formula (2) combine deformation distribution principle when volume invariance principle is composite spinning.

Step 2) and 3) in the preparation method of conventional spinning track: first determine suitable involute path during conventional spinning, subsequently involute path fitted to the circular arc line curve through Roller locus beginning and end.

Involute base radius a determines according to core diameter d: d/a >=0.3 (3)

As shown in Figure 8, the position of the involute centre of gyration is determined by following formula:

$x_0={\stackrel{\‾}{x}}_m+{\stackrel{\‾}{\mathrm{\ρ}}}_m(1-{\mathrm{sin\θ}}_0)---\left(4\right)$

$y_0={\stackrel{\‾}{y}}_m-{\stackrel{\‾}{\mathrm{\ρ}}}_m(1-{\mathrm{cos\θ}}_0)---\left(5\right)$

${\stackrel{\‾}{y}}_m/a=0.085---\left(6\right)$

${\mathrm{\θ}}_0^{\′}=0.485{\[{(x_0/a)}^2+{(y_0/a)}^2\]}^{0.2569}+{\mathrm{tg}}^{-1}(y_0/x_0)---\left(7\right)$

${\stackrel{\‾}{\mathrm{\ρ}}}_m={\mathrm{\ρ}}_m+t_0,{\stackrel{\‾}{x}}_m=x_m-t_0,{\stackrel{\‾}{y}}_m=y_m+t_0---\left(8\right)$

In formula: x_mFor the distance of centre of gyration P Yu core end face, y_mFor the distance of centre of gyration P Yu core side, θ₀Headed by the passage elevation angle.ρ m is core radius of corner, and t0 is sotck thinkness, as shown in Figure 8.θ′₀For passage elevation angle angular referenced, it is to determine x₀And y₀The value that back-pushed-type (7) calculates, by θ '₀Value θ with the selected first passage elevation angle₀Compare, if θ '₀≠θ₀, then x is adjusted_mIterative computation again, until as θ '₀=θ₀Time till；Calculated by formula (8)；x₀, y₀For intermediate computations value, byAnd θ₀Determine.

First base radius a is substituted into formula (6) to obtainConvolution (8), willValue substitution formula (5), obtains y₀；Suitably chooseValue, substitute into formula (4) obtain x₀；Next by x₀、y₀Substitution formula (7) obtains θ '₀；If θ '₀≠θ₀, then x is adjusted_mIterative computation again, until as θ '₀=θ₀Time till；Therefore, first passage elevation angle theta need to only be determined₀After, it is possible to determine the centre of gyration of Roller locus.Then make involute rotate around the centre of gyration of track, select suitable passage spacing p just to can determine that circular arc spinning toward open end track.The wherein first passage elevation angle theta of spinning roller₀Choose workpiece should be prevented wrinkling, typically take 50 ° 60 °, passage spacing p is typically obtained by test, is ensureing that workpiece wall portion does not cracks and take large values on the premise of excessive thinning as far as possible to improve production efficiency.

The determination of return track is as shown in Figure 9: figure midpoint A is the starting point (terminal of front a time spinning toward open end track) of return Roller locus, point B is the terminal (starting point of rear a time spinning toward open end) of return Roller locus, connect A, B 2 and form line segment AB, make the perpendicular bisector of line segment AB, 1 C is selected wherein on vertical line, it is made to meet h=0.04～0.05L, wherein h is the distance of C a to AB, L is the length of line segment AB, cross A, B, C 3 point, determining a circular curve (red curve in figure), this curve is return Roller locus.

The determination of transition outer rim (conventional spinning final on trajectory) in draw spinning:

D'=D₀{1-[1-(d/D₀)²]X²/h²}^1/2 (9)

In formula: D₀For blank diameter, d is core diameter, and h is workpiece height.

Relative to prior art, present invention have the advantage that

1) present invention utilizes multi-process draw-spinning to obtain tubular blank, then uses spinning to be thinned to given size, utilizes the high-precision feature of shear spinning simultaneously, make product reach the requirement of high dimensional accuracy.Blank is circular plate type blank, and its size determines according to product size, the distribution principle of deflection and spinning process.Owing to have employed shear spinning technique, therefore product uniform wall thickness, surface quality height, good compactness, defect are few.

2) during concave bottom spinning, using composite spinning manufacturing process, in the spinning process of every a time, existing shear spinning has again conventional spinning, so can effectively ensure that forming accuracy and fillet part divide and smoothly transits.

3), during wall thickness reduction, circular arc shaped portion uses circular arc spinning roller drawing attenuated；For preventing anti-phenomenon of squeezing, straight drum part employing double tapered roller mould pressing.

4) owing to being monolithic molding, eliminate drawing repeatedly, weld, operation of polishing, reduce production cost, improve production efficiency, improve the quality of product simultaneously, be suitable for produce in enormous quantities.

5) present invention is especially suited for the overall precision form of the high-fineness ratio cylindrical member of band concave bottom, only need to omit step 2 for other band bottomless drum shape parts (non-concave bottom), therefore the present invention also has universal adaptability to other band bottomless drum shape parts.

Accompanying drawing explanation

Fig. 1 is the design of part schematic diagram of the first radome；

Fig. 2 is the design of part schematic diagram of secondary shielding cover；

Fig. 31 is the first radome concave bottom part spinning schematic diagram；

Fig. 32 is the spinning track enlarged drawing of the first radome concave bottom part；

Fig. 4 is that draw spinning becomes cylindrical blank schematic diagram；

Fig. 5 is the thinning schematic diagram of arc section spinning；

Fig. 61 is direct tube section shear spinning schematic diagram；

Fig. 62 is direct tube section double tapered roller profile enlarged drawing；

Fig. 71 is secondary shielding cover concave bottom part spinning schematic diagram；

Fig. 72 is and secondary shielding cover concave bottom part spinning track enlarged drawing；

Fig. 8 is that conventional spinning track works out schematic diagram；

Fig. 9 is the determination mode figure of spinning reverse's track.

Detailed description of the invention

For being more fully understood that the present invention, the present invention is further illustrated with embodiment below in conjunction with the accompanying drawings, but embodiments of the present invention are not limited to this.

As shown in Figure 1, 2, for aluminum and aluminum alloy thin cornice concave bottom cylindrical member, in Fig. 1, part A is direct tube section to present invention External Shape to be processed, and part B is concave bottom section.Using the wheeled spinning machine of bispin to carry out mould pressing, two spinning rollers are symmetrical along main-shaft axis, when spinning concave bottom and spinning are thinned to given size, for improving stability and the precision of spinning part of spinning, use double rotary wheel spinning, radial spinning power so can be made to cancel out each other, prevent core unbalance loading.

As shown in Fig. 31 and Fig. 32, when shaping concave bottom, if the change of existing face shaping, have again wall thickness change, then in spinning process, existing conventional spinning has again shear spinning.If only face shaping change, wall thickness is not changed in, then only have conventional spinning in spinning process.

As shown in Figure 4, when draw spinning becomes cylindrical blank, in order to prevent, blank is wrinkling need to use anti-push roller, after anti-push roller 4 is arranged on blank, anti-push roller 4 uses air pressure to drive, when spinning starts, anti-push roller 4 extends blank rear under the driving of air pressure, spinning roller 3 stresses on blank during feeding, makes the blank 2 of core 1 periphery deform, and the blank one side of deformation contacts with spinning roller, another side contacts with the anti-rod that pushes away, anti-push roller 4, along with the feeding of spinning roller 3, retreats with identical speed, provides to blank and supports.Only support blank in blank side due to anti-push roller, so time only with single spinning roller spinning.

When making slab be configured to cylindrical blank and concave bottom shaping, it is the forming technology making blank diameter reduce based on radial direction drawing, therefore claims draw spinning；Owing to when shaping cylindrical blank, during single pass draw spinning, forming limit is limited, therefore in most cases needs to carry out mutiprogramming design, so also referred to as multi-process draw-spinning.When draw spinning becomes cylindrical blank, it is simple spinning toward open end, the i.e. spinning roller conventional spinning method to blank opening end feeding in the spinning of former passages；In spinning pass behind, spinning roller in mould pressing i.e. to blank opening end feeding, the most reverse blank opening end feeding, the mould pressing that this spinning is the most past, return combines, use roundtrip spinning track to be possible to prevent blank wall portion excessive thinning, improve the evenness of wall thickness after blank draw spinning.

Such as Fig. 5, shown in 61 and 62, when spinning is thinned to given size, first blank 2 is enclosed within core 1, then spinning roller is adjusted to required drafts and reduction, spinning roller, under the driving of digital control system, stresses on blank along the track feeding being parallel to core profile and makes its wall thickness reduction.When direct tube section is thinning, use double tapered roller (as shown in Fig. 6-1 and Fig. 6-2), owing to spinning roller two ends are the conical surface, therefore referred to as double tapered roller, be so possible to prevent to occur anti-to squeeze phenomenon.

Embodiment 1

A kind of high-voltage appliance switch radome, material is 1060 aluminum, shape is as shown in Figure 1, wherein direct tube section (part A in Fig. 1) diameter D=190 ± 1mm, length L=400mm, concave bottom diameter d=56 ± 0.5mm, wall thickness t=2mm, this part is used for shielding external magnetic field and electric field, it is ensured that high-voltage appliance switch steady operation.Specifically comprising the following steps that of its mould pressing

1, Blank calculation: the wall thickness of part is 2mm, it is contemplated that in the course of processing, wall thickness has the most thinning, therefore sotck thinkness should be greater than 2mm, on existing market, 1060 aluminium sheets of supply mainly have 3mm and 4mm equal-specification.

Calculate the diameter of blank when using 3mm and 4mm slab according to constancy of volume principle and be respectively 450mm and 405mm, spinning coefficient during 3mm slab is used to be respectively 0.418<0.5 (192/150=0.418), it is unsatisfactory for deformation distribution principle (formula 1), spinning coefficient when using 4mm slab is that 0.464>0.45 (192/405=0.464) meets deformation distribution principle (formula 1), the most total reduction is 50%>10% (i.e. 2mm/4mm=50%), meet deformation distribution principle (formula 2), therefore select diameter 405mm, the aluminum slab of wall thickness 4mm.

2, concave bottom mould pressing

As it is shown on figure 3, one core 1 for spinning identical with concave bottom profile of design, it is arranged on machine tool chief axis, by specification isAluminum slab be fixed between core and tail top.By the preparation method of general rotation track, choosing involute base radius 185mm, the first passage elevation angle is 60 °, and passage spacing 5mm works out general rotation track.The circular arc spinning roller selecting radius of corner to be 6mm, main shaft drives blank to rotate, and spinning roller is along the track feeding set under the control of digital control system, and the speed of mainshaft is 800r/min.Roller locus is the track (as shown in Figure 3) that general rounding arching trajectory combines with strong rotation linear type track, and the most front two passages are that conventional spinning shapes, and feed ratio is 2mm/r；The first half of the 3rd to the 6th passage is shear spinning, Roller locus is linear type, reduction is respectively 12.5%, 14.3%, 16.7%, 20%, and feed ratio is 0.6mm/r, along with the increase of passage, shear spinning track gradually increases, its length is respectively 5mm, 10mm, 15mm, 20mm, and latter half is conventional spinning, and Roller locus is circular arc, concave bottom portion inner surface after using this kind of track can make spinning is close to spinning mandrel, it is ensured that dimensional accuracy and surface quality.It is 56 ± 0.5mm that the internal diameter of concave bottom part requires, after using composite spinning to shape, the internal diameter of concave bottom part is 56 ± 0.2mm, meets dimensional requirement.

3, draw spinning becomes cylindrical blank

As shown in Figure 4, designing an a diameter of 188mm, a length of 450mm, bottom concave bottom internal diameter is the spinning mandrel of 56mm, the blank reverses direction after being shaped by concave station, uses the tail top of a diameter of 102mm by blank clamping.By the preparation method of general rotation track, choosing involute base radius 620mm, the first passage elevation angle is 50 °, and passage spacing 12mm works out general rotation track.Main shaft drives blank to rotate, and spinning roller according to setting orbiting motion, becomes cylindrical member through multi-process draw-spinning under the control of digital control system.Selecting radius of corner is the spinning roller of 17mm, and the speed of mainshaft is 800r/min, and feed ratio is 2mm/r.Owing to blank diameter is relatively big, for preventing flange wrinkle in spinning process, use anti-push roller.As shown in Figure 4, front 4 passages are simple spinning toward open end to draw spinning track；Spinning track subsequently is the spinning track that past, return combines.

4, wall thickness reduction is to given size

Use the tail top (for clamping blank the device rotated with main shaft) of a diameter of 70mm instead, by blank clamping, wall thickness reduction is divided into two steps, as shown in Figure 5, the circular arc spinning roller that the first step uses radius of corner to be 17mm divides three passage drawing attenuated bottoms circular arc shaped portion (B section in Fig. 1), i.e. main shaft drives blank to rotate, spinning roller edge under the driving of digital control system is parallel to the profile of arc section, it is fed into d point (as shown in Figure 1) from c point, first passage spinning roller and core gap are 3.2mm, second passage gap is 2.6mm, and the 3rd passage gap is 2mm；Second step uses double tapered roller (as shown in Figure 6), double rotary wheel divides the straight drum part (as shown in Figure 6) of two passage shear spinning formation of parts, i.e. main shaft drives blank to rotate, spinning roller is fed to blank opening from c point vertically, first passage reduction is 30%, second passage reduction is 28.6%, speed of mainshaft 200r/min, feed ratio 0.6mm/r.

Opening is cut away surplus, carries out follow-up Milling Process, i.e. can obtain the product meeted the requirements.Using outside micrometer, inside meter to measure part, result shows that using the radome direct tube section external diameter after composite spinning shapes is 192 ± 0.2mm, concave bottom section internal diameter 56 ± 0.1mm, meets product size required precision.Forming process is reduced to 3 roads by 6 original roads, and production efficiency improves nearly 50%.

Embodiment 2

A kind of high-voltage appliance switch radome, material is aluminium alloy, and shape is as shown in Figure 1, wherein direct tube section (part A in Fig. 1) diameter D=240 ± 1mm, length L=300mm, concave bottom diameter d=53 ± 0.5mm, length l=12mm, part entirety wall thickness is t=2mm, specifically comprises the following steps that

1, Blank calculation: calculate the diameter of blank when using 3mm slab according to constancy of volume principle and be respectively 500mm, now spinning coefficient is 0.48 > 0.45, reduction during shear spinning is 33% > 10% (1mm/3mm=33%), meets deformation distribution principle.

2, concave bottom mould pressing:

Manufacturing process is same as in Example 1, designs a spinning mandrel identical with concave bottom profile, is arranged on machine tool chief axis, by specification isAluminum slab be fixed between core and tail top, a diameter of 53mm in tail top.By the preparation method of general rotation track, choosing involute base radius 175mm, the first passage elevation angle is 60 °, and passage spacing 5mm works out general rotation track.The circular arc spinning roller selecting radius of corner to be 6mm, main shaft drives blank to rotate, and spinning roller is along the track feeding set under the control of digital control system, and the speed of mainshaft is 800r/min.Roller locus is the track that general rounding arching trajectory combines with strong rotation linear type track, and front two passages are that conventional spinning shapes, and feed ratio is 2mm/r, and Roller locus is circular arc；The first half of the 3rd to the 4th passage is shear spinning, Roller locus is linear type, reduction is respectively 16.7%, 20%, feed ratio is 0.6mm/r, along with the increase of passage, strong rotation spinning track gradually increases, and its length is respectively 5mm, 10mm, latter half is conventional spinning, and Roller locus is circular arc.

3, draw spinning becomes cylindrical blank

Designing an a diameter of 240mm, a length of 350mm, bottom concave bottom internal diameter is the spinning mandrel of 53mm, the blank reverses direction after being shaped by concave station, uses the tail top of a diameter of 100mm by blank clamping.By the preparation method of general rotation track, choosing involute base radius 792mm, the first passage elevation angle is 50 °, and passage spacing 10mm works out general rotation track.The speed of mainshaft is 800r/min, and feed ratio is 2mm/r, and selecting radius of corner is the spinning roller of 17mm, becomes cylindrical member through mutiprogramming design.Before draw spinning track, 6 passages are simple spinning toward open end；Spinning track subsequently is the spinning track that past, return combines, and uses anti-push roller in spinning process.

4, wall thickness reduction is to given size

The circular arc spinning roller using R17 divides two passages to shape circular arc shaped portion, and the first passage spinning roller is 2.4mm with the gap of core, and the second passage gap is 2.0mm；Using double tapered roller to shape straight drum part subsequently, a time mould pressing, reduction is 33%.

Opening is cut away surplus, carries out follow-up Milling Process, i.e. can obtain the product meeted the requirements.Employing radome direct tube section external diameter after composite spinning shapes is 240 ± 0.2mm, concave bottom section internal diameter 53 ± 0.1mm, meets product size required precision.

Embodiment 3

A kind of high-voltage appliance switch radome, material is aluminium alloy, and shape is as in figure 2 it is shown, straight drum part diameter D=250 ± 1mm, length L=400mm, wall thickness t1=2mm, concave bottom diameter d=60 ± 0.5mm, length l=20mm, wall thickness is t2=4mm, specifically comprises the following steps that

1, Blank calculation: calculate the diameter of blank when using 4mm slab according to constancy of volume principle and be respectively 512mm, now spinning coefficient is 0.49 > 0.45, reduction during shear spinning is 50% > 15% (2mm/4mm=50%), meets deformation distribution principle.

2, concave bottom mould pressing:

Design a spinning mandrel identical with concave bottom profile, be arranged on machine tool chief axis, by specification beAluminum slab be fixed between core and tail top, a diameter of 60mm in tail top.By the preparation method of general rotation track, choosing involute base radius 200mm, the first passage elevation angle is 60 °, and passage spacing 5mm works out general rotation track.The circular arc spinning roller selecting radius of corner to be 6mm, main shaft drives blank to rotate, and spinning roller is along the track feeding set under the control of digital control system, and the speed of mainshaft is 800r/min.Different from embodiment 12, the most only change of shape, wall thickness is constant, and therefore Roller locus is general rounding arching trajectory, 5 passage mould pressings, and feed ratio is 2mm/r, and Roller locus is circular arc (as shown in Figure 7).

3, draw spinning becomes cylindrical blank

Designing an a diameter of 250mm, a length of 450mm, bottom concave bottom internal diameter is the spinning mandrel of 60mm, the blank reverses direction after being shaped by concave station, uses the tail top of a diameter of 105mm by blank clamping.By the preparation method of general rotation track, choosing involute base radius 830mm, the first passage elevation angle is 50 °, and passage spacing 12mm works out general rotation track.The speed of mainshaft is 800r/min, and feed ratio is 2mm/r, and selecting radius of corner is the spinning roller of 17mm, becomes cylindrical member through mutiprogramming design.Before draw spinning track, 7 passages are simple spinning toward open end；Spinning track subsequently is the spinning track that past, return combines, and uses anti-push roller in spinning process.

4, wall thickness reduction is to given size

Different from embodiment 12, now bottom has met dimensional requirement, therefore only direct tube section wall portion need to be carried out shear spinning and be thinned to given size.Using double tapered roller shear spinning to shape straight drum part, two passage mould pressings, reduction is respectively 30%, and 28.6%.

Opening is cut away surplus, i.e. can obtain the product meeted the requirements.Employing radome direct tube section external diameter after composite spinning shapes is 250 ± 0.2mm, concave bottom section internal diameter 60 ± 0.2mm, meets product size required precision.

The blank of appropriate size is selected at the present invention by volume invariance principle and deformation distribution principle；When shaping concave bottom, as different from sotck thinkness in bottom wall thickness, conventional spinning and shear spinning are combined by every a time spinning, the spinning track of the most every a time combines with general rounding arching trajectory for strong rotation linear type track, as identical with sotck thinkness in bottom wall thickness, the most only need conventional spinning to shape；When formation of parts main part, first slab draw spinning being become cylindrical blank, then spinning is thinned to given size.Shear spinning and conventional spinning have been organically combined the complete near-net-shape of band concave bottom Thin Walled Curved bus part.

Claims (6)

1. a high-fineness ratio band concave bottom thin-wall tube-shaped element accurate forming method, it is characterised in that comprise the steps:

1) size of slab is calculated

Shape according to part, size, deformation distribution principle in shaping according to constancy of volume principle and composite spinning, determine the size of blank, including diameter and the thickness of blank；Wherein the diameter control of blank is at cut off diameter D_tIn；D_t=d/m_t；m_tFor limit drawing coefficient, d is core diameter；

2) concave bottom part shapes

Being clamped in by blank between core and tail top, determine the spinning track shaping concave bottom cylindrical portion according to the preparation method of conventional spinning track, during concave bottom part mould pressing, front 13 passages are conventional spinning, and Roller locus is circular arc track；Thereafter every time comprises conventional spinning and shear spinning, and its Roller locus comprises two parts, and front portion is the track during shear spinning being parallel to bottom concave bottom axis, and making every time reduction is 10 25%, and rear portion is circular arc track during conventional spinning；Every time starting point revolving by force track is blank end face, and terminal is the starting point of the general rotation track according to the establishment of conventional spinning track, and the terminal of conventional spinning track is determined by formula (9), and last passage spinning track is the contour line of concave bottom part；

D'=D₀{1-[1-(d/D₀)²]X²/h²}^1/2 (9)

In formula: D₀For blank diameter, d is core diameter, and h is workpiece height；

3) draw spinning becomes cylindrical blank

Blank upset after concave bottom is shaped, it is fixed between tail top and core, general rotation track is worked out according to conventional spinning track preparation method, main shaft drives blank to rotate, spinning roller, under the driving of digital control system, carries out feeding by the track worked out, and front 68 passages of spinning track are simple spinning toward open end, it is followed by the spinning track that roundtrip combines, blank draw spinning is become cylindrical member；

4) spinning is thinned to given size

Bottom circular arc shaped portion uses circular arc spinning roller drawing attenuated, it is ensured that every time reduction is 20% 25%；Straight drum part uses double tapered roller, it is ensured that every time reduction is 20% 35%；

5) follow-up general processing, meets accessory size requirement.

High-fineness ratio band concave bottom thin-wall tube-shaped element accurate forming method the most according to claim 1, it is characterised in that described limit drawing coefficient is by diameter wrinkle resistant and blank when not rupturing during test blank draw spinning.

High-fineness ratio band concave bottom thin-wall tube-shaped element accurate forming method the most according to claim 1, it is characterised in that described simple spinning toward open end is that spinning roller stresses on blank, along the direction feeding away from rotation centerline.

High-fineness ratio band concave bottom thin-wall tube-shaped element accurate forming method the most according to claim 1, it is characterized in that, the spinning track that described roundtrip combines is that spinning roller stresses on blank, first along the direction feeding away from rotation centerline, feeding the most in opposite direction.

High-fineness ratio band concave bottom thin-wall tube-shaped element accurate forming method the most according to claim 1, it is characterized in that, described step 2) and 3) in the preparation method of conventional spinning track: first determine suitable involute path during conventional spinning, subsequently involute path fitted to the circular arc line curve through Roller locus beginning and end.

High-fineness ratio band concave bottom thin-wall tube-shaped element accurate forming method the most according to claim 5, it is characterised in that described involute base radius a determines according to core diameter d: d/a >=0.3 (3)

The position of the involute centre of gyration is determined by following formula:

In formula: x_mFor the distance of centre of gyration P Yu core end face, y_mFor the distance of centre of gyration P Yu core side, θ₀Headed by the passage elevation angle；ρ_mFor core radius of corner, t₀For sotck thinkness；θ′₀For passage elevation angle angular referenced；It is calculated by formula (8)；x₀, y₀For intermediate computations value, byAnd θ₀Determine；First base radius a is substituted into formula (6) to obtainConvolution (8), willValue substitution formula (5), obtains y₀；Suitably chooseValue, substitute into formula (4) obtain x₀；By x₀、y₀Substitution formula (7) obtains θ '₀；If θ '₀≠θ₀, then x is adjusted_mIterative computation again, until as θ '₀=θ₀Time till；Then make involute rotate around the centre of gyration of track, select suitable passage spacing p to determine circular arc spinning toward open end track；The wherein first passage elevation angle theta of spinning roller₀Taking 50 ° 60 °, passage spacing p is obtained by test.