Note: Descriptions are shown in the official language in which they were submitted.
FORMING METHOD FOR AEROSPACE COVER
TECHNICAL FIELD
[01] The disclosure is mainly applied to the technical field of forming of
various
covers for aerospace equipment, and particularly relates to a common numerical
control
spin forming process for an aluminum cover having a thickness of 1.2 mm or 1.5
mm, a
diameter of a cylinder wall of 150 mm-230 mm, a height of 60 mm-110 mm and a
width
of a flange of 10 mm-15 mm.
BACKGROUND ART
[02] In the field of aerospace equipment, a cover is one of the important
structural
parts of a rocket body. For a long time, covers are produced through manual
spinning,
correction, shape correction and turning. Manual spinning is seriously
affected by
technical levels and working states of producers, and a thinning rate of a
wall thickness
is 25%-40% (which is required to be not greater than 34.5%), such that product
quality
consistency is poor, a qualified rate is often 50%-90%, and high time
consumption and
labor intensity are caused.
[03] At present, no institution or individual in China has disclosed a forming
method
for a pure aluminum cover part. Similarly, in the prior art, there is an
article entitled
"Research on Influence of Spinning Trace and Process Parameters on Multi-pass
Drawing Spin Fonning Quality" published by Zeng Chao et al. in the journal
"Forging
Technology". In this article, the influences of pass curves and process
parameters of
different traces on multi-pass drawing spin forming quality of AL6061 and SPCC
sheets
having thicknesses of 2 mm and 1 mm respectively were studied. Their minimum
thinning rates under optimal parameters were 9% and 7% respectively; but a
formed
product is a cylindrical part having a diameter (I) of 68 mm and an
unspecified height,
and the blank used has a diameter (1) of 140 mm. The disclosure is designed
for a
cylindrical part having a diameter cp of 150 mm-230 mm and a height of 60 mm-
110
mm and having a flange with a width of about 15 mm, and uses a blank having a
diameter (1) of 250 mm-380 mm. There is a significant difference in difficulty
of
controlling a thinning rate between them.
[04] In order to solve problems of time-consuming and labor-consuming, poor
stability
and a low qualified rate in manual spin forming, the disclosure provides a
forming
method for a cover, which is mainly characterized in that manual spin forming
is
improved into fonning through a common numerical control spinning process, and
a
drawing method for a trace through a numerical control spinning process and
selections
of process parameters are given. Through the disclosure, a labor intensity can
be
effectively reduced, processing efficiency can be improved, a thinning rate
can be
controlled within 25%, and a qualified rate of parts can be ensured to reach
99% or
above.
SUMMARY
[05] In order to overcome defects of existing technologies, the disclosure
provides a
forming method for an aerospace cover.
1
Date Recue/Date Received 2023-06-29
[06] A technical solution used for solving the technical problems of the
disclosure
is as follows: a forming method for an aerospace cover includes the following
steps:
[07] step one, forming preparation:
[08] 1.1 generally estimating a spinning blank size 0;
[09] 1.2 selecting a fillet radius R of a spinning roller;
[10] 1.3 cutting a blank by laser, a size being the spinning blank size 0 +
(5
mm-10 mm); and
[11] 1.4 mounting a spinning die and the spinning roller on a numerical
control
spinning machine;
[12] step two, trace drawing:
[13] 2.1 determining inner and outer outlines of a trace; and
[14] 2.2 drawing a plurality of passes of spinning traces;
[15] step three, spin forming:
[16] 3.1 setting a rotation speed of the spinning roller to be 500 r/min-
600 r/min
and a feed ratio to be 0.5 mm/r-3 mm/r;
[17] 3.2 compiling a numerical control program according to the plurality
of passes
of spinning traces, and parameters of the rotation speed of the spinning
roller and the
feed ratio;
[18] 3.3 setting wear values of a spinning roller cutter in X and Z
directions;
[19] 3.4 clamping the blank on the numerical control spinning machine,
turning the
blank into a required diameter 0, deburring the blank, and applying
lubricating oil to
the blank; and
[20] 3.5 adjusting a spindle and a feed rate to 100% so as to form a part
through
spinning;
[21] step four, shape correction:
[22] 4.1 correcting a flange of the part to a horizontal state; and
[23] 4.2 forming a fillet Ri of the flange by means of a shape correction
tool; and
[24] step five, turning:
[25] 5.1 clamping the spinning die, an upper cushion block and the part on
a lathe,
and turning the flange and an inner hole of the part into Do and Oh
respectively; and
[26] 5.2 using abrasive paper and polishing cloth to polish a surface of
the part to
be smooth and bright.
[27] Compared with the prior art, the disclosure has the beneficial effects:
[28] 1, compared with an existing forming technology, the disclosure records
all
information of a spinning process of qualified parts by means of a numerical
control
program, thus realizing solidification of process parameters, greatly
improving a
qualified rate of parts, and ensuring that forming quality of parts is stable
and reliable
and a qualified rate of products >99%; and
[29] 2, compared with an existing common spinning technology, according to a
spin
forming mechanism that compared with reverse pressure stress, forward spinning
tensile
2
Date Recue/Date Received 2023-06-29
stress can make a wall thickness of a part thinner, the disclosure greatly
reduces contact
with a blank at a forward stage of a spinning process, and provides detailed
reverse
parameters that can effectively reduce crinkling risks, thus effectively
controlling a
thinning rate of parts, and realizing a thinning rate of a wall thickness of a
cover
processed through a common numerical control spinning process <25%.
BRIEF DESCRIPTION OF THE DRAWINGS
[30] The disclosure will be explained in examples and with reference to the
accompanying drawings. In the drawings:
[31] FIG. 1 is a schematic diagram of a cover part;
[32] FIG. 2 is a schematic diagram of a spinning roller;
[33] FIG. 3 shows a method for determining an inner outline;
[34] FIG. 4 is diagram of a single pass of spinning trace;
[35] FIG. 5 shows a plurality of passes of spinning traces and inner and
outer
outlines;
[36] FIG. 6 is a schematic diagram of a forming process
(blank-spinning-correction-shape correction and turning); and
[37] FIG. 7 is a schematic diagram of a shape correction tool.
[38] In the drawings, the reference numerals include: die surface 1,
spinning roller
2, die end face 3, inner outline of trace 4, single pass of reciprocating
trace 5, outer
outline 6, spinning roller trace base point 7, spinning die 8, upper cushion
block 9,
lower cushion block 10, and general backing ring 11.
DETAILED DESCRIPTION OF THE EMBODIMENTS
[39] A main technical solution of a forming method for an aerospace cover
is as
follows:
[40] 1. Forming preparation
[41] 1.1 A spinning blank size 0 is generally estimated according to a
product
drawing and the following formula:
0 = 11412 2dt1 HI- 2D t) t2D02 - D2)1145 d2
[42]
[43] In the foitnula, t1 is an actual average thickness of a straight wall
after spin
forming, an actual average thickness of a straight wall of an aluminum plate
having a
nominal thickness of 1.5 mm is 1.2, and an actual average thickness of a
straight wall of
an aluminum plate having a nominal thickness of 1.2 mm is 0.9.
[44] tz is an actual average thickness of a flange after spin forming, an
actual
average thickness of a flange of an aluminum plate having a nominal thickness
of 1.5
mm is 1.5, and an actual average thickness of a flange of an aluminum plate
having a
nominal thickness of 1.2 mm is 1.2.
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Date Recue/Date Received 2023-06-29
[45] 6 is an actual thickness of a blank.
[46] H is a height of a part.
[47] d is a diameter of a bottom of the part.
[48] D is a diameter of a mouth of the part.
[49] Do is a diameter of a flange of the part.
[50] As shown in FIG. 1.
[51] 1.2 A fillet radius R of a spinning roller is selected according to a
size of the
part: for a part having a size of d of 150 mm-250 mm and H of 50 mm-110 mm, a
radius
R of the spinning roller is 8 mm-14 mm.
[52] 1.3 The blank is cut by laser, a size being the spinning blank size 0
+ (5
mm-10 mm), a material being A1035 M.
[53] 1.4 A spinning die (8 in FIG. 7) and the spinning roller 2 (having a
structure as
shown in FIG. 2) are mounted on a numerical control spinning machine, and a
radial
circle run-out tolerance value is measured by a dial gauge. The spinning die
is required
to have a circle run-out tolerance value <0.1 mm, the spinning roller is
required to have
a circle run-out tolerance value <0.02 mm, and a mounting attack angle of the
spinning
roller is 45 .
[54] 2 Trace drawing
[55] 2.1 Inner and outer outlines of a trace are determined: it is
necessary to
consider compensation of the fillet radius of the spinning roller for the
inner outline, a
determination method is as shown in FIG. 3, a circle having a radius being S
is drawn at
an end point by taking an offset distance S (equal to the fillet radius R of
the spinning
roller) of an outline of a die surface 1, an intersection point of vertical
and horizontal
lines of the circle is taken, a perpendicular line of the outline of the die
surface 1 is
made by passing the intersection point, the outline of the die offsets by a
length AS of
the perpendicular line, and horizontal extension is conducted to a die end
line by taking
an intersection point of an offset line and the vertical line of the circle,
the offset line
and a horizontal extension line forming the inner outline 4. The outer outline
6 is an
elliptical line, a center of an ellipse is located at an intersection point of
the inner outline
and the die end line, and values a and b of a short axis and a long axis are
computed
according to the following formula:
a = (D0-- D)I Pt
[56]
b= (0 ¨ d)/2 _ R
[57]
[58] 2.2 A plurality of passes of spinning traces are drawn (FIG. 5): an
initial
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Date Recue/Date Received 2023-06-29
rotation angle a of 13 -16 is taken; as shown in FIG. 4, a line shape of a
forward
process of a single pass of reciprocating trace 5 is a "straight" line, a
"concave" arc is
used for a reverse process, a reverse process end point and a forward process
start point
have a horizontal distance AX and a distance from the inner outline of 1 mm-2
mm,
AX gradually increases from 0.3 mm to 5 mm, and a linear distance AT between a
high point of a reverse process "concave" line and the forward process is 2 mm-
3 mm; a
start point of a next pass is an end point of an immediately preceding pass of
reverse
process, an end point of the forward process is determined according to a
pressing
amount of each pass AY and an intersection position of a forward process line
and an
immediately preceding pass of reverse process line, AY gradually decreases
from 4 mm
to 1.5 mm, and a distance of the intersection position is kept to be (1/4-
1/3)L from an
end point of a forward process length L; and repeating is conducted in this
way until a Z
value is equal to about 0.95 time of a height H of the part and an X value is
0.8 time of a
width of the flange, so as to complete drawing of the plurality of passes of
reciprocating
spinning traces. A one-way spinning trace is used for a final pass, the inner
outline and a
die end face 3 are taken as start points of the trace, a position, that is
0.95H away from
the die end line, of a path along the inner outline is taken as a midpoint, an
arc is drawn
with the midpoint as a start point, an end point of the arc is outside an end
point of a
final pass of forward process of the reciprocating traces, and a radius of the
arc is
slightly smaller than a radius of a final pass of reverse process, with 1.1
times
preferably.
[59] 3 Spin forming
[60] 3.1 A rotation speed of the spinning roller is 500 r/min-600 r/min and
a feed
ratio is 0.5 mm/r-3 mm/r. A low feed ratio of a first pass is selected, a high
multi-pass
reciprocating spinning feed ratio is selected, and a low feed ratio of a final
pass is
selected.
[61] 3.2 A numerical control program is compiled according the trace in 2.2
and the
parameters in 3.1.
[62] 3.3 Wear values of a spinning roller cutter in X and Z directions are
set, that is,
a gap between the spinning roller and the die is set to be 90% of an actual
thickness of a
material.
[63] 3.4 The blank is clamped on the numerical control spinning machine,
the
blank is turned into a required diameter 0, the blank is deburred, and
lubricating oil is
applied to the blank.
[64] 3.5 A spindle and a feed rate are adjusted to 100% so as to form a
part through
spinning.
[65] 4 Shape correction
[66] 4.1 The flange of the part is corrected to a horizontal state (FIG.
6).
[67] 4.2 A fillet RI of the flange is formed by means of a shape correction
tool. A
structure of the shape correction tool is as shown in FIG. 7 and includes: the
spinning
die 8, an upper cushion block 9, a lower cushion block 10 and a general
backing ring 11.
[68] 5 Turning
[69] 5.1 The spinning die, the upper cushion block and the part are clamped
on a
Date Recue/Date Received 2023-06-29
lathe, and the flange and an inner hole of the part are turned into Do and Oh
respectively.
[70] 5.2 Abrasive paper is used to polish a surface of the part.
[71] The disclosure is described in detail below in conjunction with the
accompanying drawings and specific embodiments.
[72] The disclosure mainly manufactures various covers for aerospace
equipment
through common numerical control spinning, correction, shape correction and
turning.
[73] An aluminum cover having sizes of Do = 248, D = 218, d = 213,
Oh = 190 and R = 2 and a nominal thickness of a blank of 1.5 mm is formed
mainly
through the following steps:
[74] 1 Forming preparation
[75] 1.1 A spinning blank size 0 is generally estimated according to a
product
drawing and the following formula:
2dt1 2Dt1) + t3(D02 - 132)]+ d2 $tt 372mat
-
[76] 6
[77] In the formula, t is 1.2, t2 is 1.5, S is an actual thickness 1.38 of
the blank,
and other parameters are according to sizes in a drawing.
[78] 1.2 A spinning roller (FIG. 2) has sizes of R=10, R1=122.2, R2=188.5,
B=45
and L=160. R1 is a spinning roller forward process compound surface fillet, R2
is a
spinning roller reverse process compound surface fillet, B is a width of the
spinning
roller, and L is a diameter of the spinning roller, with a unit of mm.
[79] 1.3 The blank is cut by laser, a size 0 being 380, and a material
being A1035
M.
[80] 1.4 A spinning die (FIG. 7) and the spinning roller (FIG. 2) are
mounted on a
numerical control spinning machine, and a radial circle run-out tolerance
value is
measured by a dial gauge. The spinning die is required to have a circle run-
out tolerance
value <0.1 mm, the spinning roller is required to have a circle run-out
tolerance value
<0.02 mm, and a mounting attack angle of the spinning roller is 450
.
[81] 2 Trace drawing
[82] 2.1 Inner and outer outlines of a trace are determined: it is
necessary to
consider compensation of the fillet radius of the spinning roller for the
inner outline, a
determination method is as shown in FIG. 3, a circle having a radius being
S=10 mm is
drawn at an end point by taking an offset distance S=10 mm (equal to a fillet
radius R10
of the spinning roller) of an outline of a die surface 1, an intersection
point of vertical
and horizontal lines of the circle is taken, a perpendicular line of the
outline of the die
surface 1 is made by passing the intersection point, the outline of the die
offsets by a
6
Date Recue/Date Received 2023-06-29
length AS=2.5 mm of the perpendicular line, and horizontal extension is
conducted to a
die end line by taking an intersection point of an offset line and the
vertical line of the
circle, the offset line and a horizontal extension line foiining the inner
outline. The outer
outline is an elliptical line, a center of an ellipse is located at an
intersection point of the
inner outline and the die end line, and values a and b of a short axis and a
long axis are
computed according to the following formula:
= (13 D3/2 H = 69.5mm
[83]
b = (14 R =11Smni
[84]
[85] 2.2 A plurality of passes of spinning traces are drawn (FIG. 5): an
initial
rotation angle a of 14 is taken; as shown in FIG. 4, each pass is a
reciprocating path, a
line shape of a forward process is a "straight" line, a "concave" arc is used
for a reverse
process, a reverse process end point and a forward process start point have a
horizontal
distance AX and a distance from the inner outline of 1 mm, AX gradually
increases
from 0.2 mm to 5 mm, and a linear distance AT between a high point of a
reverse
process "concave" line and the forward process is about 3 mm; a start point of
a next
pass is an end point of an immediately preceding pass of reverse process, an
end point
of the forward process is determined according to a pressing amount of each
pass AY
and an intersection position of a forward process line and an immediately
preceding
pass of reverse process line, AY gradually decreases from 4 mm to 1.5 mm, and
a
distance of the intersection position is kept to be (1/4-1/3)L from an end
point of a
forward process length L; and repeating is conducted in this way until a Z
value is equal
to about 96 and an X value is equal to about 12, so as to complete drawing of
the
plurality of passes of reciprocating spinning traces. A one-way spinning trace
is used for
a final pass, the inner outline and a die end face 3 are taken as start points
of the trace, a
position, that is 96 mm away from the die end line, of a path along the inner
outline is
taken as a midpoint, an arc is drawn with the midpoint as a start point, an
end point of
the arc is outside an end point of a final pass of forward process of the
reciprocating
traces, and a radius of the arc is R77.
[86] 3 Spin forming
[87] 3.1 A rotation speed of the spinning roller is 600 r/min, a feed ratio
of a first
pass is 2 mm/r, a multi-pass reciprocating spinning feed ratio is 3 mm/r, and
a feed ratio
of a final pass is 0.5 mm/r.
[88] 3.2 A numerical control program is compiled according the trace in 2.2
and the
parameters in 3.1.
[89] 3.3 Wear values of a spinning roller cutter in X and Z directions are
set, that is,
a gap between the spinning roller and the die is 1.25.
[90] 3.4 The blank is clamped on the numerical control spinning machine,
the
blank is turned into a required diameter 0 of 372 mm, the blank is deburred,
and
lubricating oil is applied to the blank.
7
Date Recue/Date Received 2023-06-29
[91] 3.5 A spindle and a feed rate are adjusted to 100% so as to form a
part through
spinning.
[92] 4 Shape correction
[93] 4.1 The flange of the part is corrected to a horizontal state (FIG.
6).
[94] 4.2 A fillet R1=2 of the flange of the part is formed by means of a
shape
correction die (FIG. 7).
[95] 5 Turning
[96] 5.1 The spinning die, the upper cushion block and the part are clamped
on a
lathe, and the flange and an inner hole the part are turned into a diameter
D0=248 mm
and a diameter i=190 mm respectively.
[97] 5.2 Abrasive paper and polishing cloth are used to polish a surface of
the part
to be smooth and bright.
8
Date Recue/Date Received 2023-06-29
