CN114888342B - Method for machining blisk blade by adopting drum-shaped knife - Google Patents
Method for machining blisk blade by adopting drum-shaped knife Download PDFInfo
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- B—PERFORMING OPERATIONS; TRANSPORTING
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- B23C—MILLING
- B23C3/00—Milling particular work; Special milling operations; Machines therefor
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- B23C3/18—Working surfaces curved in two directions for shaping screw-propellers, turbine blades, or impellers
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Abstract
The invention discloses a method for processing a blisk blade by adopting a drum-shaped cutter, which is characterized in that a drum-shaped cutter structure used for processing is defined according to the minimum tip distance and the minimum channel distance between two adjacent blades of the blisk and the minimum curvature radius of a blade profile curved surface of the blade, and the cutting contact track of the blade is obtained by combining the step length between cutting contacts and the step distance between cutting rows according to the cutting contact relation between the cutter and the blade profile; then solving the cutter shaft vector corresponding to each cutting contact by setting the cutter shaft vector at the characteristic point on the appointed cutting line and combining a quaternion interpolation method, and carrying out interference-free iterative inspection on the main blade and the adjacent blade of the cutter shaft to obtain an interference-free smoothing cutter shaft vector; and finally, calculating the corresponding cutter position point of the drum cutter through the cutting contact point, the cutter shaft vector and the curved surface normal vector. The invention can greatly improve the processing efficiency while ensuring the surface quality of the blade by utilizing the special structural advantage of the drum-shaped knife so as to reduce the production cost.
Description
Technical Field
The invention relates to the technical field of numerical control milling, in particular to a method and a system for processing a drum-shaped cutter of a blisk blade.
Background
Low-pressure compressor fans and high-pressure compressors of aero-engines commonly employ blisk structures. Compared with the traditional blade and wheel disk assembled structure, the blisk greatly simplifies the engine structure and reduces the weight. The existing blisk blade curved surface is mainly processed in a ball head cutter point milling mode, time is sacrificed during point milling, and efficiency is low. The channels between the blades are narrower and longer, and the slender weak-rigidity cutter is required to be adopted for processing, so that the cutter has obvious cutter yielding due to insufficient structural rigidity.
In modern numerical control machining, in addition to the usual types of milling cutters, drum cutters are increasingly being mentioned. When parts such as the side wall surface of the deep cavity die are processed, compared with other cutters, the drum-shaped cutter can achieve better surface quality under high processing efficiency, and the processed parts are small in surface roughness and high in smoothness. Compared with the point milling mode of the ball-end cutter, the processing efficiency of the drum-shaped cutter can be greatly improved. Meanwhile, compared with a side milling mode, the angle between the cutter and the milled surface is formed during machining, so that the contact area of the cutter is effectively reduced during cutting of the cutter, the extension length of the cutter is shortened, the rigidity of the cutter is increased, and the cutting vibration of the cutter is reduced.
In summary, the drum cutter has the advantages of point milling and side milling of the ball head cutter, and particularly when the effective cutting radius of the cutter is large enough, the surface quality and the machining efficiency can be obviously improved. However, for the machining of blisk blades, the use of drum knives is still in the experimental stage.
Disclosure of Invention
The invention aims to overcome the defects of the prior art and provide a method for processing blisk blades by adopting a drum-shaped cutter, which can realize better surface milling quality under the condition of improving the processing efficiency, thereby reducing the processing cost of the blades.
In order to achieve the above purpose, the technical scheme adopted by the invention is as follows: a method of machining blisk blades using a drum cutter, comprising the steps of:
determining the diameter of a drum-shaped cutter bar according to the minimum tip distance and the minimum channel distance between two adjacent blades of the blisk, and simultaneously determining the maximum equivalent radius of a cutting edge of the drum-shaped cutter according to the minimum curvature radius of a blade profile curved surface of the blade and the drum-shaped cutter structure to obtain a drum-shaped cutter structure suitable for processing the blisk blade;
step two, calculating the cutting contact track of the drum-shaped cutter for processing the blisk blade: creating a segment model of the blade, dividing a closed curved surface of the complete blade into a front edge curved surface, a rear edge curved surface, a blade basin curved surface and a blade back curved surface, creating four sections of blade curved surfaces unfolded by the blade by taking boundary lines of the blade back curved surface and the front edge curved surface as boundaries, mapping the four sections of blade curved surfaces in a u-v plane coordinate system of the blade curved surfaces, calculating to obtain the number of cutting contacts on the four sections of blade curved surfaces, designating the minimum step length between two adjacent cutting contacts, sequentially connecting the cutting contacts on the four sections of blade curved surfaces to obtain a row of cutting contact, and then determining the row spacing of the cutting contact by combining the height of residual cutter lines of a drum cutter and spiral cutting feed so as to generate a blade cutting contact track;
the height of the residual cutter grain of the drum-shaped cutter refers to the residual height of the cutter on a material left between two adjacent cutting rows, the height is 0.003-0.01mm during finish milling, if the value is small, the distance between the cutting rows is very close, the cutter rows are dense, and the value is large, the sparsity of the cutter rows is indicated;
step three, calculating a non-interference smooth drum-shaped cutter shaft vector: designating cutting points as four cutter shaft characteristic points at four boundary lines among a front edge curved surface, a rear edge curved surface, a leaf basin curved surface and a leaf back curved surface on any cutting line on the blade cutting point track, defining initial non-interference cutter shaft vectors for the cutting front dip angle and the side deflection angle of the drum-shaped cutters corresponding to the four cutter shaft characteristic points, calculating the drum-shaped cutter shaft vectors corresponding to each cutting point by combining a quaternion interpolation method, and carrying out non-interference iterative inspection on the cutter shaft vectors obtained by the quaternion interpolation, so as to obtain non-interference smoothing drum-shaped cutter shaft vectors;
step four, calculating the drum cutter position point: and (3) calculating the drum-shaped cutter sites of each cutting point on the curved surface according to the normal vector of the corresponding curved surface of the drum-shaped cutter at any cutting point and the drum-shaped cutter shaft vector obtained in the step (III), thereby obtaining the path track of the processing blade of the drum-shaped cutter.
Further, in the step one, the specific calculation steps of the diameter of the cutter bar of the drum cutter and the maximum equivalent radius of the cutting edge part of the drum cutter are as follows:
the cutting edge of the drum-shaped knife is formed by a circular arc with the radius R 1 And a radius R of arc 2 Is formed by side edges; the diameter of the cutter bar of the drum cutter is D, O is respectively arranged on the rotation center line of the drum cutter 1 、O 3 、O 4 Three points, said O 1 The point is the center point of the arc of the tool nose, and O 3 The point is the radius R of the radian 2 Intersection point with the central line of the cutter, O 4 The point is the center point of the interface between the cutting edge of the drum-shaped cutter and the straight shankThe method comprises the steps of carrying out a first treatment on the surface of the Any blade cutting contact P on the drum cutter c The normal vector N and the cutter shaft vector T form an N-T plane, and then an intersection point O of the curved normal vector N and the cutter shaft vector T is arranged in the N-T plane 3 The normal vector of the curved surface of each cutting contact point on the cutting edge of the drum-shaped cutter always passes through the O3 point, and any edge cuts the contact point P c To the intersection point O 3 Is R is a distance of 3 The following steps are:
R 1 ≤R 3 ≤D/2；
defining the minimum blade tip distance and the minimum channel distance as a swinging cutter distance, wherein the maximum cutter bar diameter D of a selected drum cutter bar is always smaller than the swinging cutter distance, and the radian radius R is used for avoiding self-interference of the selected drum cutter when cutting the curved surface of the blade 2 The maximum equivalent radius of the cutting edge of the drum-shaped cutter is smaller than the minimum curvature radius of the blade profile curved surface.
Further, the specific calculation steps of the number of cutting contacts on the machining spiral cutting line on the four-section blade curved surface in the second step are as follows:
under the u-v plane coordinate system, taking the initial cutting position as P start And a termination cutting position P end According to the fact that the last discrete point on the curved surface of the previous blade is used as the first discrete point on the curved surface of the next blade, the method is used for avoiding the coincidence of boundary points of two adjacent curved surfaces on the same spiral cutting line, and the tangential points on the curved surfaces of the four sections of blades are planned, so that the method can be used for obtaining:
cutting contact A on the cutting spiral line i,j The parameters in the u direction are:
the cutting contact A i,j The parameters in the v direction are:
wherein n is 1 、n 2 、n 3 And n 4 The cutting contact points of one cutting row on the four-section blade curved surface are respectively; said n 1 、n 2 、n 3 And n 4 The distance between adjacent cutting contacts is the minimum step length, and n is connected in turn 1 、n 2 、n 3 And n 4 A row of cut rows is obtained.
Further, the step two further includes: and re-parameterizing the complete blade curved surface with uniformity destroyed when being segmented by the boundary line in a u-v coordinate system, and then mapping to obtain the u-v plane coordinate system of the blade curved surface.
Further, the third step specifically comprises: the cutting part of the drum cutter is regarded as a ball-end cutter cutting edge with the radius the same as the maximum equivalent radius of the cutting edge of the drum cutter, so that the specific steps of calculating the cutter shaft vector corresponding to all cutting points on any feed track are as follows:
31 Designating cutting points as four cutter shaft characteristic points at four boundary lines between a front edge curved surface and a rear edge curved surface on any cutting row on the blade cutting point track and a blade basin curved surface and a blade back curved surface, and defining an initial interference-free cutter shaft vector for the cutting front inclination angle and the side deflection angle of the drum cutter corresponding to the four cutter shaft characteristic points;
32 According to the space distance between the cutter and the blades of the cutter shaft vector corresponding to the cutter shaft characteristic points, carrying out interference judgment on the cutter shaft vector, namely the main blade and the adjacent two blades of the integral blade disc, wherein the cutter shaft vector smaller than the safety inspection allowance is regarded as an interference cutter shaft, the safety inspection allowance is not smaller than 0.3mm, and then modifying the initial side deflection angle and the forward inclination angle, and modifying and iterating until all cutter shaft vectors pass interference inspection;
33 Dividing the characteristic points at the boundary line of the front edge and the rear edge by the characteristic points to obtain cutter shaft vectors corresponding to the external contact points, and calculating through a quaternion interpolation algorithm to obtain cutter shaft vectors corresponding to any contact point between the two characteristic points;
34 Extracting the cutter shaft vector interpolated by the quaternion in the cutting row to perform interference inspection on the main blade and two adjacent blades, wherein 20-30 points are respectively selected from the back blade basin surface, and 10-15 points are respectively selected from the front edge head and the rear edge head; when interference occurs, the initial side deflection angle and the forward inclination angle of the characteristic cutter shaft vector of the two boundaries of the characteristic region where the interference point is located are optimized, and interpolation calculation and interference inspection are carried out again after updating until all cutter shafts pass interference inspection.
Furthermore, the quaternion interpolation algorithm is to connect two specified vectors on the largest circular arc of the spherical surface by using interpolation vectors, specifically:
given two designated arbor vectors q 1 (q 1x ,q 1y ,q 1z )、q n (q nx ,q ny ,q nz ) From the interpolation between these two vectors, q is obtained i The calculation formula of (2) is as follows:
where θ=arccoss (q 1 ·q n )，
Setting a starting point P 1 And end point P n Is T 1 、T 2 The tangential contact track between the two is obtained { P } according to the previous planning mode i In the method for generating the track of the cutting contact by using the cutting contact, i=1, … and n }, the curve arc length between two adjacent cutting contacts on the same cutting row is changed, the distance between the two adjacent points is in direct proportion to the corresponding vector rotation angle, and P 1 And P n The total length of the contact cutting tracks is S 1n The method comprises the following steps:
from the starting point P 1 To the current cutting contact P i The track length of (2) is:
the parameter t is expressed as:
at the same time θ=arccoss (T 1 ·T 2 ) The finally obtained cutting contact P i The cutter shaft vector of (a) is:
and thus, any contact point between the two characteristic points corresponds to the cutter shaft vector.
Further, the fourth step specifically comprises:
under the condition of a cutter shaft vector obtained by planning a curved surface normal vector of a curved surface cutting point and a cutting point, a known drum cutter has a unique cutter site P t At a certain cutting point P c Where the arbor vector T is known, the drum knife point P t The solution is as follows:
1) Selecting one cutting contact P c The normal vector of the point on the curved surface is N, and the distance P is obtained along the normal vector direction c Length of R 2 Is defined by the cutting side edge center point P O2 Namely the point of the edge center:
P O2 ＝P C +R 2 ·N；
2) The cutter shaft vector T and the curved surface normal vector N are cross multiplied to obtain a vector T multiplied by N, and a plane sigma with the normal vector T multiplied by N is obtained;
3) Obtaining a vector T on a plane sigma by using a plane normal vector T multiplied by N and an arbor vector T n ：
T n ＝(T×N)×T
4) Through the edge point P O2 Along vector T n Obtaining a distance R 2 -R tool Point P of (2) O3 Then
P O3 ＝P O2 +(R 2 -R tool )·T n
5) Obtaining the drum-shaped knife position point P t The coordinate calculation formula of (2) is as follows:
P t ＝P O3 -L dis ·T
l in the formula dis Is P O3 To the tool nose P t Is a constant distance from the bottom of the container.
The beneficial effects of the invention are as follows: according to the method, the structural characteristics of the drum-shaped cutter are fully utilized, the cutter position track of the drum-shaped cutter for milling the blisk blade is calculated, and the surface quality and milling efficiency of blisk blade processing are effectively improved.
Drawings
FIG. 1 is a schematic diagram of a four-section blade curved surface unfolding and mapping u-v plane coordinate system of the blade;
FIG. 2 is a schematic view of the trajectory of the tangential contact on a four-section blade curve according to the present invention;
FIG. 3 is a schematic diagram of the geometry of the drum blade according to the present invention;
FIG. 4 is a schematic diagram of quaternion interpolation according to the present invention;
FIG. 5 is a schematic view of the knife shaft vector of the interference-free fairing drum knife of the present invention;
FIG. 6 is a schematic diagram of a drum cutter position solution according to the present invention;
FIG. 7 is a graph showing the effect of the ball and drum blades finish milling the blade surface quality with the same cutting parameters;
FIG. 8 is a schematic view of a blisk blade configuration for a computing example of the present invention;
FIG. 9 is a schematic view of a blisk blade radius of curvature configuration for a computing example of the present invention;
fig. 10 is a schematic diagram of a helical path trajectory of a drum cutter according to an exemplary embodiment of the present invention.
Detailed Description
The principles and features of the present invention are described below with reference to the drawings, the examples are illustrated for the purpose of illustrating the invention and are not to be construed as limiting the scope of the invention.
In order to achieve the above object, the present invention provides the following embodiments:
example 1: as shown in fig. 1-7, a method for machining blisk blades using a drum cutter includes the steps of:
determining the diameter of a drum-shaped cutter bar according to the minimum tip distance and the minimum channel distance between two adjacent blades of the blisk, and simultaneously determining the maximum equivalent radius of a cutting edge of the drum-shaped cutter according to the minimum curvature radius of a blade profile curved surface of the blade and the drum-shaped cutter structure to obtain a drum-shaped cutter structure suitable for processing the blisk blade;
the specific calculation steps of the maximum equivalent radius of the cutting edge part of the drum cutter in the first step are as follows:
as shown in FIG. 3, the cutting edge of the drum cutter is formed by a circular arc with a radius R 1 And a radius R of arc 2 Is formed by side edges; the diameter of the cutter bar of the drum cutter is D, O is respectively arranged on the rotation center line of the drum cutter 1 、O 3 、O 4 Three points, said O 1 The point is the center point of the arc of the tool nose, and O 3 The point is the radius R of the radian 2 Intersection point with the central line of the cutter, O 4 The point is the center point of the interface between the cutting edge of the drum-shaped cutter and the straight shank; any blade cutting contact P on the drum cutter c The normal vector N and the cutter shaft vector T form an N-T plane, and then an intersection point O of the curved normal vector N and the cutter shaft vector T is arranged in the N-T plane 3 The normal vector of the curved surface of each cutting contact point on the cutting edge of the drum-shaped cutter always passes through the O3 point, and any edge cuts the contact point P c To the intersection point O 3 Is R is a distance of 3 The following steps are:
R 1 ≤R 3 ≤D/2；
defining the minimum blade tip distance and the minimum channel distance as a swinging cutter distance, wherein the maximum cutter bar diameter D of a selected drum cutter bar is always smaller than the swinging cutter distance, and the radian radius R is used for avoiding self-interference of the selected drum cutter when cutting the curved surface of the blade 2 The maximum equivalent radius of the cutting edge of the drum-shaped cutter is smaller than the minimum curvature radius of the blade profile curved surface.
Step two, as shown in fig. 1, calculating the contact point cutting track of the drum-shaped cutter for processing the blisk blade: creating a segment model of the blade, dividing a closed curved surface of the complete blade into a front edge curved surface, a rear edge curved surface, a blade basin curved surface and a blade back curved surface, creating four sections of blade curved surfaces unfolded by the blade by taking boundary lines of the blade back curved surface and the front edge curved surface as boundaries, mapping the four sections of blade curved surfaces in a u-v plane coordinate system of the blade curved surfaces, calculating to obtain the number of cutting contacts on the four sections of blade curved surfaces, designating the minimum step length between two adjacent cutting contacts, sequentially connecting the cutting contacts on the four sections of blade curved surfaces to obtain a row of cutting contact, and then determining the row spacing of the cutting contact by combining the height of residual cutter lines of a drum cutter and spiral cutting feed so as to generate a blade cutting contact track;
the specific calculation steps of the number of cutting contacts on the machining spiral cutting line on the four-section blade curved surface in the second step are as follows:
as shown in FIG. 2, under the u-v plane coordinate system, the initial cutting position is taken as P start And a termination cutting position P end According to the fact that the last discrete point on the curved surface of the previous blade is used as the first discrete point on the curved surface of the next blade, the method is used for avoiding the coincidence of boundary points of two adjacent curved surfaces on the same spiral cutting line, and the tangential points on the curved surfaces of the four sections of blades are planned, so that the method can be used for obtaining:
cutting contact A on the cutting spiral line i,j The parameters in the u direction are:
the cutting contact A i,j The parameters in the v direction are:
wherein n is 1 、n 2 、n 3 And n 4 The cutting contact points of one cutting row on the four-section blade curved surface are respectively; said n 1 、n 2 、n 3 And n 4 The distance between adjacent cutting contacts is the minimum step length, and n is connected in turn 1 、n 2 、n 3 And n 4 A row of cut rows is obtained.
The second step further comprises: and re-parameterizing the complete blade curved surface with uniformity destroyed when being segmented by the boundary line in a u-v coordinate system, and then mapping to obtain the u-v plane coordinate system of the blade curved surface.
Step three, calculating a non-interference smooth drum-shaped cutter shaft vector: designating cutting points as four cutter shaft characteristic points at four boundary lines among a front edge curved surface, a rear edge curved surface, a leaf basin curved surface and a leaf back curved surface on any cutting line on the blade cutting point track, defining initial non-interference cutter shaft vectors for the cutting front dip angle and the side deflection angle of the drum-shaped cutters corresponding to the four cutter shaft characteristic points, calculating the drum-shaped cutter shaft vectors corresponding to each cutting point by combining a quaternion interpolation method, and carrying out non-interference iterative inspection on the cutter shaft vectors obtained by the quaternion interpolation, so as to obtain non-interference smoothing drum-shaped cutter shaft vectors;
as shown in fig. 3, the third step specifically includes: the cutting part of the drum cutter is regarded as a ball-end cutter cutting edge with the radius the same as the maximum equivalent radius of the cutting edge of the drum cutter, so that the specific steps of calculating the cutter shaft vector corresponding to all cutting points on any feed track are as follows:
31 Designating cutting points as four cutter shaft characteristic points at four boundary lines between a front edge curved surface and a rear edge curved surface on any cutting row on the blade cutting point track and a blade basin curved surface and a blade back curved surface, and defining an initial interference-free cutter shaft vector for the cutting front inclination angle and the side deflection angle of the drum cutter corresponding to the four cutter shaft characteristic points;
32 According to the space distance between the cutter and the blades of the cutter shaft vector corresponding to the cutter shaft characteristic points, carrying out interference judgment on the cutter shaft vector, namely the main blade and the adjacent two blades of the integral blade disc, wherein the cutter shaft vector smaller than the safety inspection allowance is regarded as an interference cutter shaft, the safety inspection allowance is not smaller than 0.3mm, and then modifying the initial side deflection angle and the forward inclination angle, and modifying and iterating until all cutter shaft vectors pass interference inspection;
33 Dividing the characteristic points at the boundary line of the front edge and the rear edge by the characteristic points to obtain cutter shaft vectors corresponding to the external contact points, and calculating through a quaternion interpolation algorithm to obtain cutter shaft vectors corresponding to any contact point between the two characteristic points;
34 Extracting the cutter shaft vector interpolated by the quaternion in the cutting row to perform interference inspection on the main blade and two adjacent blades, wherein 20-30 points are respectively selected from the back blade basin surface, and 10-15 points are respectively selected from the front edge head and the rear edge head; when interference occurs, the initial side deflection angle and the forward inclination angle of the characteristic cutter shaft vector of the two boundaries of the characteristic region where the interference point is located are optimized, interpolation calculation and interference detection are carried out again after updating until all cutter shafts pass through interference detection, and the interference-free smooth drum-shaped cutter shaft vector is obtained through calculation, as shown in fig. 5.
According to the calculation method of the step length between cutting contacts and the step distance between adjacent cutting lines, the cutter shaft vector of the cutter at any contact position of the blade can be obtained by combining the calculation method of the cutter shaft vector corresponding to the cutting contacts, and meanwhile, the mode of changing the side deflection angle from the blade tip to the blade root is adopted for optimization, so that the cutting edge contact area of the drum-shaped cutter is gradually transited in different cutting processes, the excessive use of the drum-shaped cutter on the same latitude (the latitude change is smaller) of the conical surface of the cutting edge ball is avoided, and the purpose of prolonging the service life of the cutter is achieved.
As shown in fig. 4, the quaternion interpolation algorithm connects two specified vectors on the maximum circular arc of the sphere by using interpolation vectors, specifically:
given two designated arbor vectors q 1 (q 1x ,q 1y ,q 1z )、q n (q nx ,q ny ,q nz ) From the interpolation between these two vectors, q is obtained i The calculation formula of (2) is as follows:
where θ=arccoss (q 1 ·q n )，
Setting a starting point P 1 And end point P n Is T 1 、T 2 The tangential contact track between the two is obtained { P } according to the previous planning mode i In the method for generating the track of the cutting contact by using the cutting contact, i=1, … and n }, the curve arc length between two adjacent cutting contacts on the same cutting row is changed, the distance between the two adjacent points is in direct proportion to the corresponding vector rotation angle, and P 1 And P n The total length of the contact cutting tracks is S 1n The method comprises the following steps:
from the starting point P 1 To the current cutting contact P i The track length of (2) is:
the parameter t is expressed as:
at the same time θ=arccoss (T 1 ·T 2 ) The finally obtained cutting contact P i The cutter shaft vector of (a) is:
and thus, any contact point between the two characteristic points corresponds to the cutter shaft vector.
Step four, calculating the drum cutter position point: and (3) calculating the drum-shaped cutter sites of each cutting point on the curved surface according to the normal vector of the corresponding curved surface of the drum-shaped cutter at any cutting point and the drum-shaped cutter shaft vector obtained in the step (III), thereby obtaining the path track of the processing blade of the drum-shaped cutter.
Specifically, as shown in fig. 6,under the condition of a cutter shaft vector obtained by planning a curved surface normal vector of a curved surface cutting point and a cutting point, a known drum cutter has a unique cutter site P t At a certain cutting point P c Where the arbor vector T is known, the drum knife point P t The solution is as follows:
1) Selecting one cutting contact P c The normal vector of the point on the curved surface is N, and the distance P is obtained along the normal vector direction c Length of R 2 Is defined by the cutting side edge center point P O2 Namely the point of the edge center:
P O2 ＝P C +R 2 ·N；
2) The cutter shaft vector T and the curved surface normal vector N are cross multiplied to obtain a vector T multiplied by N, and a plane sigma with the normal vector T multiplied by N is obtained;
3) Obtaining a vector T on a plane sigma by using a plane normal vector T multiplied by N and an arbor vector T n ：
T n ＝(T×N)×T
4) Through the edge point P O2 Along vector T n Obtaining a distance R 2 -R tool Point P of (2) O3 Then
P O3 ＝P O2 +(R 2 -R tool )·T n
5) Obtaining the drum-shaped knife position point P t The coordinate calculation formula of (2) is as follows:
P t ＝P O3 -L dis ·T
l in the formula dis Is P O3 To the tool nose P t Is a constant distance from the bottom of the container.
According to the parameters obtained by the method, the milling path track of the drum-shaped blade is generated, and after post-treatment, the finish machining milling of the part is realized on the five-axis machining center.
Calculation example: as shown in fig. 8-10, for a blisk blade, the drum cutter machining method of the present invention is now used to calculate, for example, the following:
after the minimum blade tip distance H1 is measured to be 21.04mm, the minimum channel distance H2 is measured to be 17.23mm, the blade length L is measured to be 65mm, as shown in fig. 8 and 9, only the curved surface of the blade basin side of the blade model is a concave curved surface, the minimum curvature radius of the blade is calculated to be 94.75mm, then the cutter bar diameter D of the drum cutter is selected to be smaller than the cutter distance determined by the minimum blade tip distance and the minimum channel distance, and the cutter bar diameter D is selected to be 16mm in consideration of the structural rigidity factor of the cutter.
According to the method provided by the invention, the minimum curvature radius of the blade curved surface model is combined, and the arc radius R of the cutting edge part of the drum-shaped cutter 2 80mm is selected, and the arc radius R1 of the tool nose is 3mm. The blade length was 65mm and the total length of the drum knife was 110mm considering that about 40mm would be clamped in the drum knife handle.
By utilizing the drum cutter with selected structural parameters and combining the processing method of the drum cutter with the blisk blade disclosed by the invention, the spiral path track of the cutter as shown in fig. 10 can be generated, so that the finish milling processing of the blade is completed, the actual test and detection prove that the surface quality and the tolerance of the blade profile meet the requirements, and the processing time is greatly shortened compared with that of a ball head cutter.
The invention solves the problem of difficult milling of the drum-shaped knife on the blades of the blisk. The quality of the processed surface of the curved surface processed by the method is as shown in figure 7 under the condition of the same cutting parameters as that of the ball head cutter, and the curved surface processed by the method has the advantages of regular tool marks, clear lines and high surface quality, and the processed surface generated by the method is smooth mainly because the drum-shaped cutter is in line contact during cutting. When the drum-shaped cutter and the ball-end cutter with the same diameter cutter bar and feeding speed are used for cutting the same curved surface feature, the actual cutting time comparison shows that the finish machining efficiency of the drum-shaped cutter is far higher than that of a common ball-end structural cutter, and the machining time is about 45% of that of the ball-end cutter.
According to experimental results, the method can effectively improve the machining surface quality and milling efficiency of the blisk blade, thereby reducing the machining cost of the blade.
The foregoing description of the preferred embodiments of the invention is not intended to limit the invention to the precise form disclosed, and any such modifications, equivalents, and alternatives falling within the spirit and scope of the invention are intended to be included within the scope of the invention.
Claims (7)
1. A method of machining blisk blades using a drum cutter, comprising the steps of:
determining the diameter of a drum-shaped cutter bar according to the minimum tip distance and the minimum channel distance between two adjacent blades of the blisk, and simultaneously determining the maximum equivalent radius of a cutting edge of the drum-shaped cutter according to the minimum curvature radius of a blade profile curved surface of the blade and the drum-shaped cutter structure to obtain a drum-shaped cutter structure suitable for processing the blisk blade;
step two, calculating the cutting contact track of the drum-shaped cutter for processing the blisk blade: creating a segment model of the blade, dividing a closed curved surface of the complete blade into a front edge curved surface, a rear edge curved surface, a blade basin curved surface and a blade back curved surface, creating four sections of blade curved surfaces unfolded by the blade by taking boundary lines of the blade back curved surface and the front edge curved surface as boundaries, mapping the four sections of blade curved surfaces in a u-v plane coordinate system of the blade curved surfaces, calculating to obtain the number of cutting contacts on the four sections of blade curved surfaces, designating the minimum step length between two adjacent cutting contacts, sequentially connecting the cutting contacts on the four sections of blade curved surfaces to obtain a row of cutting contact, and then determining the row spacing of the cutting contact by combining the height of residual cutter lines of a drum cutter and spiral cutting feed so as to generate a blade cutting contact track;
step three, calculating a non-interference smooth drum-shaped cutter shaft vector: designating cutting points as four cutter shaft characteristic points at four boundary lines among a front edge curved surface, a rear edge curved surface, a leaf basin curved surface and a leaf back curved surface on any cutting line on the blade cutting point track, defining initial non-interference cutter shaft vectors for the cutting front dip angle and the side deflection angle of the drum-shaped cutters corresponding to the four cutter shaft characteristic points, calculating the drum-shaped cutter shaft vectors corresponding to each cutting point by combining a quaternion interpolation method, and carrying out non-interference iterative inspection on the cutter shaft vectors obtained by the quaternion interpolation, so as to obtain non-interference smoothing drum-shaped cutter shaft vectors;
step four, calculating the drum cutter position point: and (3) calculating the drum-shaped cutter sites of each cutting point on the curved surface according to the normal vector of the corresponding curved surface of the drum-shaped cutter at any cutting point and the drum-shaped cutter shaft vector obtained in the step (III), thereby obtaining the path track of the processing blade of the drum-shaped cutter.
2. The method for machining blisk blades using a drum cutter according to claim 1, wherein the step one of calculating the diameter of the shank of the drum cutter and the maximum equivalent radius of the cutting edge portion of the drum cutter comprises the steps of:
the cutting edge of the drum-shaped knife is formed by a circular arc with the radius R 1 And a radius R of arc 2 Is formed by side edges; the diameter of the cutter bar of the drum cutter is D, O is respectively arranged on the rotation center line of the drum cutter 1 、O 3 、O 4 Three points, said O 1 The point is the center point of the arc of the tool nose, and O 3 The point is the radius R of the radian 2 Intersection point with the central line of the cutter, O 4 The point is the center point of the interface between the cutting edge of the drum-shaped cutter and the straight shank; any blade cutting contact P on the drum cutter c The normal vector N and the cutter shaft vector T form an N-T plane, and then an intersection point O of the curved normal vector N and the cutter shaft vector T is arranged in the N-T plane 3 The normal vector of the curved surface of each cutting contact point on the cutting edge of the drum-shaped cutter always passes through the O3 point, and any edge cuts the contact point P c To the intersection point O 3 Is R is a distance of 3 The following steps are:
R 1 ≤R 3 ≤D/2；
defining the minimum blade tip distance and the minimum channel distance as a swinging cutter distance, wherein the maximum cutter bar diameter D of a selected drum cutter bar is always smaller than the swinging cutter distance, and the radian radius R is used for avoiding self-interference of the selected drum cutter when cutting the curved surface of the blade 2 The maximum equivalent radius of the cutting edge of the drum-shaped cutter is smaller than the minimum curvature radius of the blade profile curved surface.
3. The method for machining blisk blades by using a drum cutter according to claim 1, wherein the specific calculation step of the number of cutting contacts on the machining spiral cutting line on the four-section blade curved surface in the second step is as follows:
under the u-v plane coordinate system, taking the initial cutting position as P start And a termination cutting position P end According to the fact that the last discrete point on the curved surface of the previous blade is used as the first discrete point on the curved surface of the next blade, the method is used for avoiding the coincidence of boundary points of two adjacent curved surfaces on the same spiral cutting line, and the tangential points on the curved surfaces of the four sections of blades are planned, so that the method can be used for obtaining:
cutting contact A on cutting spiral i,j The parameters in the u direction are:
the cutting contact A i,j The parameters in the v direction are:
(0≤i≤n 1 +n 2 +n 3 +n 4 -4,0≤j＜m)
wherein n is 1 、n 2 、n 3 And n 4 The cutting contact points of one cutting row on the four-section blade curved surface are respectively; said n 1 、n 2 、n 3 And n 4 The distance between adjacent cutting contacts is the minimum step length, and n is connected in turn 1 、n 2 、n 3 And n 4 The cutting contacts obtain a row of cutting contact rows.
4. The method of machining blisk blades using a drum cutter as in claim 1, further comprising, in step two: and re-parameterizing the complete blade curved surface with uniformity destroyed when being segmented by the boundary line in a u-v coordinate system, and then mapping to obtain the u-v plane coordinate system of the blade curved surface.
5. The method for machining blisk blades using a drum blade as defined in claim 1, wherein the step three is specifically: the cutting part of the drum cutter is regarded as a ball-end cutter cutting edge with the radius the same as the maximum equivalent radius of the cutting edge of the drum cutter, so that the specific steps of calculating the cutter shaft vector corresponding to all cutting points on any feed track are as follows:
31 Designating cutting points as four cutter shaft characteristic points at four boundary lines between a front edge curved surface and a rear edge curved surface on any cutting row on the blade cutting point track and a blade basin curved surface and a blade back curved surface, and defining an initial interference-free cutter shaft vector for the cutting front inclination angle and the side deflection angle of the drum cutter corresponding to the four cutter shaft characteristic points;
32 According to the space distance between the cutter and the blades of the cutter shaft vector corresponding to the cutter shaft characteristic points, carrying out interference judgment on the cutter shaft vector, namely the main blade and the adjacent two blades of the integral blade disc, wherein the cutter shaft vector smaller than the safety inspection allowance is regarded as an interference cutter shaft, the safety inspection allowance is not smaller than 0.3mm, and then modifying the initial side deflection angle and the forward inclination angle, and modifying and iterating until all cutter shaft vectors pass interference inspection;
33 Dividing the four cutter shaft characteristic points in the step 31) and calculating the cutter shaft vector corresponding to the external contact point through a quaternion interpolation algorithm to obtain any cutter shaft vector corresponding to any contact point between the two characteristic points;
34 Extracting the cutter shaft vector interpolated by the quaternion in the cutting row to perform interference inspection on the main blade and two adjacent blades, wherein 20-30 points are respectively selected from the back blade basin surface, and 10-15 points are respectively selected from the front edge head and the rear edge head; when interference occurs, the initial side deflection angle and the forward inclination angle of the characteristic cutter shaft vector of the two boundaries of the characteristic region where the interference point is located are optimized, and interpolation calculation and interference inspection are carried out again after updating until all cutter shafts pass interference inspection.
6. The method for processing blisk blades by using a drum cutter according to claim 5, wherein the quaternion interpolation algorithm is to connect two specified vectors on the largest circular arc of the sphere by using interpolation vectors, specifically:
given two designated arbor vectors q 1 (q 1x ,q 1y ,q 1z )、q n (q nx ,q ny ,q nz ) From the interpolation between these two vectors, q is obtained i The calculation formula of (2) is as follows:
where θ=arccoss (q 1 ·q n )，
Setting a starting point P 1 And end point P n Is T 1 、T 2 The tangential contact track between the two is obtained by P according to the previous planning mode i I=1..n, where n is the total number of cut contacts, in the method of generating a track of cut contacts using the above method, the arc length of the curve between two adjacent cut contacts on the same cutting line is changed, and the distance between two adjacent points is proportional to the corresponding vector rotation angle, P 1 And P n The total length of the contact cutting tracks is S 1n The method comprises the following steps:
from the starting point P 1 To the current cutting contact P i The track length of (2) is:
the parameter t is expressed as:
at the same time θ=arccoss (T 1 ·T 2 ) The finally obtained cutting contact P i The cutter shaft vector of (a) is:
and thus, any contact point between the two characteristic points corresponds to the cutter shaft vector.
7. The method for machining blisk blades using a drum blade as defined in claim 1, wherein the fourth step is specifically:
under the condition of a cutter shaft vector obtained by planning a curved surface normal vector of a curved surface cutting point and a cutting point, a known drum cutter has a unique cutter site P t At a certain cutting point P c Where the arbor vector T is known, the drum knife point P t The solution is as follows:
1) Selecting one cutting contact P c The normal vector of the point on the curved surface is N, and the distance P is obtained along the normal vector direction c Length of R 2 Is defined by the cutting side edge center point P O2 Namely the point of the edge center:
P O2 ＝P C +R 2 ·N；
2) The cutter shaft vector T and the curved surface normal vector N are cross multiplied to obtain a vector T multiplied by N, and a plane sigma with the normal vector T multiplied by N is obtained;
3) Obtaining a vector T on a plane sigma by using a plane normal vector T multiplied by N and an arbor vector T n ：
T n ＝(T×N)×T
4) Through the edge point P O2 Along vector T n Obtaining a distance R 2 -R tool Point P of (2) O3 Then
P O3 ＝P O2 +(R 2 -R tool )·T n
5) Obtaining the drum-shaped knife position point P t The coordinate calculation formula of (2) is as follows:
P t ＝P O3 -L dis ·T
l in the formula dis Is P O3 To the tool nose P t Is a constant distance from the bottom of the container.
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