CN103302162B - Mould positioning method based on feature distance - Google Patents

Abstract

The invention discloses a mould positioning method based on a feature distance. The method comprises the following five steps: 1, initially putting a mould, namely (1) putting a cushion block and (2) putting the mould; 2, moving equipment, namely (1) determining a coordinate, (2) reversing the equipment and (3) driving the equipment; 3, measuring and calculating, namely (1) measuring the distance and (2) geometrically calculating; 4, carrying out positioning calculation on the mould; and 5, correcting a digital control code for stretch forming. According to the method, the equipment is driven to move by motion parameters of a clamp position reversing stretch-forming machine according to equipment features of a ACB FET series digital control horizontal drawing machine, the coordinate and the space position of a mould feature point are calculated by the distance between a clamp feature point and the mould feature point, and the digital control code for the stretch forming is redesigned according to a mould position, thereby achieving accurate skin stretch forming; and due to a mould putting process in the method, the mould putting error redundancy can be increased, the mould putting time can be shortened, the use of a positioning tool can be reduced, and the production efficiency of aircraft skin stretch forming can be improved.

Description

A kind of mould localization method of feature based distance

(1) technical field

The present invention relates to the localization method that die layout position determined by a kind of aircraft skin part in stretch forming process.In particular to using the numerical control stretch former of ACB FET series at the localization method carrying out cross directional stretch shaping front mold putting position.Belong to space shuttle manufacturing technology field.

(2) background technology

Skin part is the appearance part forming and maintain Aerodynamic Configuration of Aireraft.Stretch forming (being called for short pull-shaped) is a kind of process having the coated shaping of mould, is one of main forming mode of aircraft skin class part forming.Pull-shapedly the both sides of woollen to be clamped by equipment clamp, utilize the motion of mould and clamp, make that woollen produces uneven stretcher strain and coating mould makes woollen and mould fit.

Pull-shaped technological parameter mainly contains the percentage elongation of woollen and the coated angle of clamp, by the true form of technological parameter and pull-shaped mould, calculates the movement locus (as Fig. 1) of clamp.ACB FET series numerical controlled stretch forming machine is the horizontal stretching machine, stretching former that French ACB GEC ALSTHOM company produces, and the structure of this serial stretching machine, stretching former is similar, is divided into FET400, FET600, FET1200 etc. according to tonnage.Adopt numerical controlled stretch forming machine to carry out skinning surface, utilize equipment to the accurate control of clamp movement locus, realize accurate forming process.The size of aircraft skin stretch-forming mould is from tens centimetres to tens meters, and the pull-shaped mold weight of large-scale skin part also reaches hundred tons.Large-scale pull-shaped mould is installed, normally hangs with row and mould is sling, then assisted by many people simultaneously and mould is installed to pull-shaped equipment assigned address produces.Mould to be placed into the position pre-set usually to need repeatedly to place and finely tune, install and also often continue a few hours, and final putting position also exist relatively large deviation.The uncertainty of die layout position, becomes the uncertain factor affecting covering forming quality, thus affects the forming accuracy of skinning surface.Therefore a kind of method of quick position mould is needed to carry out the actual putting position of jig, and for die layout position at that time, revise technological parameter and numerical control code, clamp movement locus is tallied with the actual situation, make Stretch Forming Process more accurate, ensure part forming quality.

(3) summary of the invention

1, object:

The object of this invention is to provide a kind of mould localization method of feature based distance.The method is according to the feature of numerical controlled stretch forming equipment, utilize the accurate coordinates of characteristic point on clamp, measure the relative distance with characteristic point on mould, determine the site error of die layout, equipment processing numerical control code is revised, improves the quality of accuracy and the part be shaped.

2, technical scheme:

The mould localization method of a kind of feature based distance of the present invention, its step is as follows:

Step one: mould is initially put

Initially putting of skin part stretch forming mold is placed in the coordinate system of pull-shaped equipment by actual mould, is the preparation of carrying out mould location survey and Stretch Forming Process, as shown in Figure 2;

In the actual production process of factory, die layout, on standard cushion block, is together placed in the coordinate system of pull-shaped equipment with cushion block.Standard cushion block is the homemade standard component of factory, and the mold weight that can hold by height and cushion block is distinguished.Mould is initially put first according to skinning surface die boundary dimensions and quality, choice criteria cushion block; Then put cushion block and mould according to factory technics code, measure cushion block end face levelness, guarantee cushion block placement level.Record cushion block height H and mold feature point are apart from mould floor height h.

Step 2: sports equipment

Sports equipment is that the equipment clamp of ACB FET series transverse stretching machine is moved to assigned address, and it is in same level that clamp characteristic point and mold feature point are in, and is convenient to range measurement.

(1) coordinate is determined

Determining the coordinate position at clamp characteristic point place when measuring, by the height of cushion block and the distance of mold feature point distance mould bottom surface, determining the height (Z coordinate) of mold feature point place horizontal plane; By appearance and size and the theoretical locus of putting of mould, determine the position of clamp characteristic point in X-axis (X-coordinate); According to the position of clamp characteristic point on clamp, the Y-coordinate of clamp characteristic point can be obtained, as shown in Figure 3;

(2) equipment is counter separates

The anti-solution of motion of ACB FET series transverse stretching machine is the coordinate position by clamp characteristic point, solves the length of each pressurized strut on parallel institution, i.e. the kinematic parameter of equipment according to the mechanical feature of pull-shaped equipment.The digital control horizontal machine drawing of ACB FET series is mainly used in that aircraft skin part is horizontal pulls into shape, and the profile of stretching machine, stretching former as shown in Figure 4; The symmetrical structure of this equipment, the straight jaw clamp in one, every side, two horizontal pressurized struts, two longitudinal pressurized struts, composition two is to four bar parallel institutions, and schematic diagram of mechanism is as shown in Figure 5; The locus of clamp and attitude are determined jointly by the elongation of four pressurized struts; When positioning measurement, in order to simplify the anti-computational process of separating of motion, setting clamp axis is parallel with Y-axis, therefore only need calculate the position of clamp in ZX plane, namely only need calculate the elongation of Z pressurized strut and A pressurized strut, as shown in Figure 6;

(3) driving arrangement

By the elongation of each pressurized strut of stretching machine, stretching former that the anti-solution of ACB FET series transverse stretching machine obtains, the driving arrangement motion of input digital control horizontal machine drawing control system interface, makes clamp move to assigned address, for carrying out range measurement.

Step 3: survey calculation

Measuring process measures the distance of each characteristic point of clamp to each characteristic point of mould, then calculates through geometry, obtain the coordinate of characteristic point.

(1) range measurement

Left side (X is negative side), right side (X is positive side) two clamps mark two characteristic points respectively, is designated as P _l1, P _l2and P _r1, P _r2; Mould marks two characteristic points, is designated as T _land T _r.Measure P respectively _l1, P _l2to T _ldistance geometry P _r1, P _r2to T _rdistance, as shown in Figure 7.Due to common measuring method, as tape measure, long rope etc., error is comparatively large, takes more high-precision measurement means to measure, as three-coordinates measuring machine, laser tracker etc., can improve mould positioning precision;

(2) geometry calculates

After the motion of step 2 driving arrangement, on clamp, characteristic point and mold feature point are in the horizontal plane of sustained height, and therefore mould location Calculation can utilize the method for solving of plane geometry, calculate the coordinate of mold feature point, as shown in Figure 8.

Found out by Fig. 8, for left side, mold feature point T _lconcrete coordinate can by with P _l1for the center of circle, L _l1for the circle of radius and with P _l2for the center of circle, L _l2for the intersection point of the circle of radius is determined, in like manner right side mold characteristic point T can be determined _rconcrete coordinate.

Step 4: mould location Calculation

The concrete coordinate of the mold feature point obtained by survey calculation, is compared calculating with mold feature point theoretical coordinate, draws the translation vector in die top cushion block holding plane and rotational angle, as shown in Figure 9.

Step 5: revise numerical control code and carry out pull-shaped

The conversion parameter calculated by step 4, transforms to actual mould putting position by theoretical mould, and with new die location for benchmark, technique for applying parameter generates the equipment numerical control code conformed to actual mould position.By the horizontal stretching machine, stretching former of pull-shaped equipment numerical control code input ACB FET, carry out no-load running to stretching machine, stretching former, whether checkout facility motion conforms to designed technological parameter.Check errorless after, carry out skinning surface.

By above-mentioned five steps, realize the quick position of pull-shaped die space position.The method of forming trajectory is revised by mould physical location, the stretch forming process of skin part is allowed to tally with the actual situation, make, because the impact of die layout position deviation on part forming precision is able to little, to decrease the use of positioning tool, ensure the precision that aircraft skin part is produced.

Wherein, the method being solved equipment moving parameter by the coordinate of clamp characteristic point described in step 2, utilize the precision controllability of equipment mechanism feature and numerical controlled stretch forming equipment, achieve by clamp trace generator numerical control code, Stretch Forming Process is accurately controlled.

Wherein, the measurement characteristic point spacing described in step 3 determines the method for mold feature point position, by simply measuring and geometry calculating, realizing die space position and determining.The method is simple and practical, is convenient to implement.

3, advantage and effect:

The present invention is based on a kind of aircraft skin stretch-forming mould localization method of numerical controlled stretch forming equipment, it is the feature according to numerical controlled stretch forming machine, the coordinate of clamp characteristic point is obtained by the kinematic parameter of stretching machine, stretching former, measure the distance of clamp characteristic point and mold feature point, the coordinate calculating mold feature point is revised die layout position, again according to revised die location, redesign pull-shaped numerical control code by technological parameter, to realize accurate skin stretch forming.This method has formulated the die layout flow process in aircraft skin stretch-forming production process, increases the error redundancy of die layout, reduces the use of die layout time and positioning tool, improves aircraft skin stretch-forming production efficiency; And by measuring, die location is revised, make numerical control code more meet present case, the forming quality of skin part can be improved, rate of reducing the number of rejects and seconds, make horizontal pull-shaped being easier to of covering realize digital production.

(4) accompanying drawing explanation

Fig. 1 skinning surface loading procedure sketch

Schematic diagram placed by Fig. 2 mould

Fig. 3 clamp movement position schematic diagram

Fig. 4 ACB FET series digital control horizontal machine drawing appearance schematic diagram

Fig. 5 ACB FET equipment side schematic diagram of mechanism

Fig. 6 ACB FET equipment is counter separates schematic diagram

Fig. 7 characteristic point position and dimensional measurement schematic diagram

Fig. 8 mould location feature point position calculation schematic diagram

Fig. 9 mould location transformation calculations schematic diagram

Figure 10 the method for the invention flow chart

In figure, symbol description is as follows:

O: device coordinate system initial point X: device coordinate system X-axis Y: device coordinate system Y-axis Z: device coordinate system Z axis T _l: mould left feature point (X negative direction side) T _r: mould right feature point (X positive direction side) h: mold feature point is to mould bottom surface distance H: cushion block height P _l: left side clamp characteristic point (X negative direction side) P _r: right side clamp characteristic point (X positive direction side) W: die width D: clamp and mold interval A ₀: A ₀artis A _i: A _iartis Y ₀: Y ₀artis Y _i: Y _iartis Z ₀: Z ₀artis Z _i: Z _iartis Z _iI: Z _iIartis X ₀: X ₀artis X _i: X _iartis X _iI: X _iIartis O _zA: pressurized strut Z, A plane and grip finger intersection point O _xY: pressurized strut X, Y plane and grip finger intersection point P _l1: left side clamp characteristic point 1P _l2: left side clamp characteristic point 2P _r1: right side clamp characteristic point 1P _r2: right side clamp characteristic point 2 Dong: equipment angle ∠ O _zAa ₁a _oβ: equipment angle ∠ O _zAa ₁z ₁θ: equipment angle ∠ A _oo _zAa ₁ : mould left feature point theoretical position : mould right feature point theoretical position TO: mold feature point line mid point : mold feature point line mid point theoretical position

(5) detailed description of the invention

As shown in Figure 1, Figure 2, shown in Fig. 3, Fig. 4, Fig. 5, Fig. 6, Fig. 7, Fig. 8, Fig. 9, Figure 10, the mould localization method of feature based distance, the concrete implementation step of the method is as follows:

Step one: mould is initially put

Skin part stretch forming mold initially puts signal as shown in Figure 2, and the process of putting can be divided into sequentially places cushion block and places mould.

1, cushion block is placed

Cushion block is the homemade standard component of factory, divides with the weight that can bear according to height, and its height and top planes meet the required precision of process program.First according to die boundary dimensions, quality and forming trajectory determination cushion block model, cushion block is selected.When placing cushion block, according to technological procedure, cushion block is placed on the assigned address of pull-shaped equipment, makes the symmetrical plane of cushion block parallel with the YZ plane of device coordinate.After placement completes, measure the levelness of cushion block top planes, guarantee cushion block end face level.The height H of record cushion block.

2, mould is placed

Before placing mould, first Measurement die characteristic point is apart from the height h of mould bottom surface, and checks characteristic point position, compare with the theoretical digital-to-analogue of mould, guarantee that actual mould is consistent with digital-to-analogue, prevent mould from changing because of other reason, as mould remodeling, mold stiffness change not.Then mould is placed on cushion block, make the coordinate center being placed on pull-shaped equipment of mould, and mold feature plane is as far as possible parallel with the coordinate plane of equipment as far as possible.Put after mould completes, Measurement die floor height and mould bottom surface levelness, ensure that mold height and levelness meet the requirements.

Step 2: sports equipment

Sports equipment is that the equipment clamp of ACB FET series transverse stretching machine is moved to assigned address, and it is in same level that clamp characteristic point and mold feature point are in, and is convenient to range measurement.First determine stretching machine, stretching former clamp position coordinate, then solve stretching machine, stretching former kinematic parameter according to clamp position is counter, then drive stretching machine, stretching former motion that clamp is moved to assigned address.

1, coordinate is determined

According to the signal of Fig. 3, determine the coordinate position moved to required for the clamp characteristic point of left and right.If the characteristic point of left and right clamp is respectively .By the surveying record of step one, the Z coordinate of known clamp characteristic point is cushion block height and mold feature point distance mould floor height sum, that is:

${Z_P}_L={Z_P}_L=H+h---\left(1\right)$

If die width is W, suppose that mould puts between two parties, clamp position is D apart from mould two lateral extent, namely has:

${x_P}_L=-(\frac{W}{2}+D),{X_P}_R=(\frac{W}{2}+D)---\left(2\right)$

The coordinate of clamp characteristic point is obtained by formula (1), (2).

2, equipment is counter separates

Calculate to simplify and measure, make the attitude of clamp during range measurement for parallel with Y-axis, as shown in Figure 5, i.e. P _l1, O _zA, O _xY, P _l2x with y coordinate identical, pressurized strut Z is identical with X elongation, and pressurized strut A is identical with Y elongation.

Carry out equipment counter separate calculate be according to known O _zApoint coordinates, the equipment of calculating makes the elongation of cylinder, to be X negative direction side on the left of equipment, as shown in Figure 6.Analysis institution's sketch, find out:

(1) known O _zA, A ₀and Z ₀coordinate.

(2) A _iwith O _zAdistance be a constant S _a, A _iwith Z _idistance be a constant S _z.

(3) A _ijoint is coaxial connection, and namely ∠ α and ∠ β immobilizes.

First the elongation making cylinder A is calculated, at △ A ₀a ₁o _zAmiddle application sine is as follows:

${\∠O}_{\mathrm{ZA}}{A}_0{A}_1={\sin }^{-1}\left(\frac{{|O}_{\mathrm{ZA}}{A}_1|}{{|}_{A0}{O}_{\mathrm{ZA}}|}\sin \mathrm{\α}\right)---\left(3\right)$

$\∠\mathrm{\θ}=\mathrm{\π}\∠\mathrm{\α}-{\∠O}_{\mathrm{ZA}}{A}_0{A}_1---\left(4\right)$

The value of ∠ θ in equipment mechanism is obtained by formula (3), (4).

By vector the ∠ θ that turns clockwise can obtain vectorial direction, S again _afor vector length, determine vector an A can be obtained _icoordinate.Specifically be calculated as follows:

$\stackrel{\→}{O_{\mathrm{ZA}}{A}_1}=\left[\begin{array}{cc}\cos \mathrm{\θ}& \sin \mathrm{\θ}\\ -\sin \mathrm{\θ}& \cos \mathrm{\θ}\end{array}\right]\frac{\stackrel{\→}{O_{\mathrm{ZA}}{A}_0}}{\left|O_{\mathrm{ZA}}{A}_0\right|}{S}_A---\left(5\right)$

$\stackrel{\→}{A_1}=\stackrel{\→}{O_{\mathrm{ZA}}}+\stackrel{\→}{O_{\mathrm{ZA}}{A}_1}---\left(6\right)$

In like manner, Z is calculated _icoordinate, as follows:

$\stackrel{\→}{A_1{Z}_1}=\left[\begin{array}{cc}\cos \mathrm{\β}& -\sin \mathrm{\β}\\ \sin \mathrm{\β}& \cos \mathrm{\β}\end{array}\right]\frac{\stackrel{\→}{A_1{O}_{\mathrm{ZA}}}}{S_A}{S}_Z---\left(7\right)$

$\stackrel{\→}{Z_1}=\stackrel{\→}{A_1}+\stackrel{\→}{A_1{Z}_1}---\left(8\right)$

Equipment mechanism artis A is calculated by formula (5), (6), (7), (8) _iand Z _icoordinate.

By the symmetry of equipment, in like manner solve the body joint point coordinate of equipment opposite side.So far all body joint point coordinate of ACB FET equipment solve, complete that mechanism is counter to separate.Make cylinder elongation to be calculated by the difference of artis to the length when distance of pressurized strut hinge support and pressurized strut zero-bit.

3, driving arrangement

To calculate ACB FET series transverse stretching machine each pressurized strut elongation input ACB FET stretching machine, stretching former control panel, driving arrangement moves, and makes clamp move to assigned address, and checks clamp position, determines to coincide with Theoretical Design position.

Step 3: survey calculation

1, range measurement

After checking that clamp and die location are errorless, the distance of measurement clamp characteristic point and mold feature point, as shown in Figure 7.Mould and clamp be divided into left side and X negative direction side and right side and X positive direction side according to X-direction.Measure left side clamp two characteristic point P respectively _l1, P _l2the characteristic point T of one end on the left of mould _ldistance and right side clamp two characteristic point P _r1, P _r2the characteristic point T of one end on the right side of mould _rdistance, and will measuring distance be recorded.

2, geometry calculates

As shown in Figure 8, according to the distance that coordinate and the measurement of known clamp characteristic point obtain, calculate the coordinate of mold feature point, computational methods are as follows:

Mould left feature point $T_L{({x_T}_L,{y_T}_L,{Z_T}_L)}^T:$

With $P_{L1}{({x_P}_{L1},{y_P}_{L1},{Z_P}_{L1})}^T$ For the center of circle, L _l1for the equation of the circle of radius is

${(T_L-P_{L1})}^T(T_L-P_{L1})={L_{L1}}^2---\left(9\right)$

With $P_{L2}{({X_P}_{L2},{y_P}_{L2},{Z_P}_{L2})}^T$ For the center of circle, L _l1for the equation of the circle of radius is

Due to a P _l1, P _l2, T _lbe in sustained height plane, that is:

${Z_T}_L={Z_P}_{L1}={Z_P}_{L2}---\left(11\right)$

Simultaneous equations, obtain about point two solutions, get larger solution is true solution, i.e. the solution of mould left feature point.

In like manner solve the solution of mould right feature point $T_R{({x_T}_R,{y_T}_R,{Z_T}_R)}^T.$

Step 4: mould location Calculation

Mold feature point coordinates is obtained by previous step $T_L{({X_T}_L,{y_T}_L,{Z_T}_L)}^T$ With $T_R{({x_T}_R,{y_T}_R,{Z_T}_R)}^T,$ By comparing with the theoretical value of mold feature point, calculate the transformation relation between theoretical die location to actual mould position, as shown in Figure 9.Die location conversion is planar realized by a translation and a rotation transformation, and conversion parameter is calculated as follows:

T _lwith T _rline mid point T _ocoordinate:

${({x_T}_O,{y_T}_O,{Z_T}_O)}^T=[{({x_T}_L,{y_T}_L,{Z_T}_L)}^T+{({x_T}_R,{y_T}_R,{Z_T}_R)}^T]/2$

with line mid point coordinate:

${({x_T^0}_O,{y_T^0}_O,{Z_T^0}_O)}^T=[{({x_T^0}_L,{y_T^0}_L,{Z_T^0}_L)}^T+{({x_T^0}_R,{y_T^0}_R,{Z_T^0}_R)}^T]/2$

Translation vector

$\stackrel{\→}{T}=\stackrel{\→}{T_O{T}_O^0}---\left(14\right)$

Anglec of rotation θ:

$\mathrm{\θ}={\cos }^{-1}\left(\frac{\stackrel{\→}{T_L{T}_R.}\stackrel{\→}{T_L^O{T}_R^O}}{|\stackrel{\→}{T_L{T}_R|}*|\stackrel{\→}{T_L^O{T}_R^O}|}\right)---\left(15\right)$

Rotating shaft vector

$\stackrel{\→}{R}=\stackrel{\→}{T_L^O{T}_R^O}\×\stackrel{\→}{T_L{T}_R}---\left(16\right)$

Step 5: revise numerical control code and carry out pull-shaped

The conversion parameter calculated by previous step, transforms to actual mould putting position by theoretical mould, and with new die location for benchmark, technique for applying parameter generates the equipment numerical control code conformed to actual mould position.By the horizontal stretching machine, stretching former of pull-shaped equipment numerical control code input ACB FET, carry out no-load running to stretching machine, stretching former, whether checkout facility motion conforms to designed technological parameter.Check errorless after, carry out skinning surface.

Claims (1)

1. a mould localization method for feature based distance, its step is as follows:

Step one: mould is initially put

Initially putting of skin part stretch forming mold is placed in the coordinate system of pull-shaped equipment by actual mould, is the preparation of carrying out mould location survey and Stretch Forming Process;

Die layout, on standard cushion block, is together placed in the coordinate system of pull-shaped equipment with cushion block, and standard cushion block is the homemade standard component of factory, and the mold weight that can bear by height and cushion block is distinguished; Mould is initially put first according to skinning surface die boundary dimensions and quality, choice criteria cushion block; Then put cushion block and mould according to factory technics code, measure cushion block end face levelness, guarantee cushion block placement level, record cushion block height H and mold feature point are apart from mould floor height h;

Step 2: sports equipment

Sports equipment is that the equipment clamp of ACB FET series transverse stretching machine is moved to assigned address, makes clamp characteristic point and mold feature point be in same level, is convenient to range measurement;

(1) coordinate is determined

Determining the coordinate position at clamp characteristic point place when measuring, by the height of cushion block and the distance of mold feature point distance mould bottom surface, determining height and the Z coordinate of mold feature point place horizontal plane; By the appearance and size of mould and theoretical locus of putting, determine the position of clamp characteristic point in X-axis and X-coordinate; According to the position of clamp characteristic point on clamp, the Y-coordinate of clamp characteristic point can be obtained;

(2) equipment is counter separates

The anti-solution of motion of ACB FET series transverse stretching machine is the coordinate position by clamp characteristic point, solves the length of each pressurized strut on parallel institution, i.e. the kinematic parameter of equipment according to the mechanical feature of pull-shaped equipment; The machine drawing of ACBFET series digital control horizontal pulls into shape for aircraft skin part is horizontal; This equipment left and right sides symmetrically structure, every side is equipped with a straight jaw clamp, two horizontal pressurized struts and two longitudinal pressurized struts; Composition two is to four bar parallel institutions; The locus of clamp and attitude are determined jointly by the elongation of four pressurized struts; When positioning measurement, in order to simplify the anti-computational process of separating of motion, setting clamp axis is parallel with Y-axis, therefore only need calculate the position of clamp in ZX plane, namely only need calculate the elongation of Z pressurized strut and A pressurized strut; Z pressurized strut refers to horizontal pressurized strut; A pressurized strut refers to longitudinal pressurized strut;

(3) driving arrangement

By the elongation of each pressurized strut of stretching machine, stretching former that the anti-solution of ACB FET series transverse stretching machine obtains, the driving arrangement motion of input digital control horizontal machine drawing control system interface, makes clamp move to assigned address, for carrying out range measurement;

Step 3: survey calculation

Measuring process measures the distance of each characteristic point of clamp to each characteristic point of mould, then calculates through geometry, obtain the coordinate of characteristic point;

(1) range measurement

Left side, two, right side clamp mark two characteristic points respectively, is designated as P _l1, P _l2and P _r1, P _r2; Mould marks two characteristic points, is designated as T _land T _r; Measure P respectively _l1, P _l2to T _ldistance geometry P _r1, P _r2to T _rdistance; Wherein, L _l1for left side clamp characteristic point P _l1to left side mold feature point T _lmeasuring distance; L _l2for left side clamp characteristic point P _l2to left side mold feature point T _lmeasuring distance;

(2) geometry calculates

After the motion of step 2 driving arrangement, on clamp, characteristic point and mold feature point are in the horizontal plane of sustained height, and therefore mould location Calculation can utilize the method for solving of plane geometry, calculate the coordinate of mold feature point;

For left side, mold feature point T _lconcrete coordinate can by with P _l1for the center of circle, L _l1for the circle of radius and with P _l2for the center of circle, L _l2for the intersection point of the circle of radius is determined, in like manner right side mold characteristic point T can be determined _rconcrete coordinate;

Step 4: mould location Calculation

The concrete coordinate of the mold feature point obtained by survey calculation, is compared calculating with mold feature point theoretical coordinate, draws the translation vector in die top cushion block holding plane and rotational angle;

Step 5: revise numerical control code and carry out pull-shaped

The translation vector calculated by step 4 and rotational angle, theoretical mould is transformed to actual mould putting position, with new die location for benchmark, technique for applying parameter generates the equipment numerical control code conformed to actual mould position, by the horizontal stretching machine, stretching former of pull-shaped equipment numerical control code input ACB FET, carry out no-load running to stretching machine, stretching former, whether checkout facility motion conforms to designed technological parameter, check errorless after, carry out skinning surface;

By above-mentioned five steps, realize the quick position of pull-shaped die space position, the method of forming trajectory is revised by mould physical location, the stretch forming process of skin part is allowed to tally with the actual situation, make because the impact of die layout position deviation on part forming precision is reduced, decrease the use of positioning tool, ensure the precision that aircraft skin part is produced.