CN114888342A - Method for machining blisk blades by using drum-shaped cutter - Google Patents
Method for machining blisk blades by using drum-shaped cutter 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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Abstract
The invention discloses a method for processing a blade of a blisk by adopting a drum-shaped cutter, which defines the drum-shaped cutter structure used for processing according to the minimum blade 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, and obtains the contact cutting track of the blade by combining the step length between contact cutting points and the step length between cutting lines according to the contact cutting relationship between a cutter and the blade profile; then, cutter shaft vectors at characteristic points on an appointed cutting line are set, cutter shaft vectors corresponding to all cutting contact points are solved by combining a quaternion interpolation method, interference-free iterative inspection of a main blade and adjacent blades is carried out on a cutter shaft, and interference-free smooth straight cutter shaft vectors are obtained; and finally, calculating the corresponding cutter location point of the drum-shaped cutter through the contact point, the cutter axis vector and the curved surface normal vector. The invention utilizes the special structure advantage of the drum-shaped knife, can greatly improve the processing efficiency while ensuring the surface quality of the blade, and reduces the production cost.
Description
Technical Field
The invention relates to the technical field of numerical control milling, and mainly aims at a method and a system for machining a drum-shaped cutter of a blisk blade.
Background
The low-pressure compressor fan and the high-pressure compressor of the aircraft engine generally adopt an integral blade disc structure. Compared with the traditional structure of assembling the blades and the wheel disc, the integral blade disc greatly simplifies the structure of the engine and reduces the weight. The existing cambered surface of the blade of the blisk is mainly processed in a ball-end cutter point milling mode, time is sacrificed in point milling, and efficiency is low. And the channels among the blades are narrower and longer, a slender weak-rigidity cutter is required to be adopted for processing, and cutter yielding is obvious due to insufficient structural rigidity of the cutter.
In modern numerical control machining, the use of drum cutters is increasingly being mentioned in addition to the usual type of milling cutters. When parts such as the side wall surface of a deep cavity die are machined, compared with other cutters, the drum-shaped cutter can achieve better surface quality under high machining efficiency, and machined parts are small in surface roughness and high in smoothness. Compare in ball head sword point and mill the mode, the machining efficiency of drum-shaped sword can obtain very big promotion. Compared with a side milling mode, the side milling mode has the advantages that an angle can be formed between the side milling mode and a milled surface during machining, so that the contact area of a 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 conclusion, the drum-shaped cutter has the advantages of both ball head cutter point milling and side milling, and particularly, when the effective cutting radius of the cutter is large enough, the surface quality and the processing efficiency can be obviously improved. The use of a drum knife is still in the trial phase for the machining of blisk blades.
Disclosure of Invention
The invention aims to overcome the defects in the prior art and provides a method for machining a blisk blade by using a drum-shaped cutter, which can realize better surface milling quality under the condition of improving the machining efficiency, thereby reducing the machining cost of the blade.
In order to achieve the purpose, the invention adopts the technical scheme that: a method of machining blisk blades using a drum cutter, comprising the steps of:
determining the diameter of a tool bar of a drum-shaped tool 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 tool according to the minimum curvature radius of a blade profile curved surface and the drum-shaped tool structure to obtain the drum-shaped tool structure suitable for machining the blades of the blisk;
step two, calculating the contact cutting track of the blade of the blisk machined by the drum-shaped cutter: creating a segmented 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, establishing four blade curved surfaces of the blade by taking a boundary line of the blade back curved surface and the front edge curved surface as a boundary, mapping the four blade curved surfaces in a u-v plane coordinate system of a blade curve, calculating to obtain the number of contact points on the four blade curved surfaces, designating the minimum step length between two adjacent contact points, sequentially connecting the contact points on the four blade curved surfaces to obtain a row of contact lines, and determining the row distance of the contact lines by combining the residual knife line height of a drum-shaped knife and a spiral cutting feed so as to generate a blade contact point track;
the residual height of the lines of the drum-shaped cutter refers to the residual height of the cutter on a material left between two adjacent cutting lines, the height is 0.003-0.01mm during finish milling, if the value is small, the distance between the cutting lines is very short, the cutter path rows are dense, and if the value is large, the cutter path rows are sparse;
step three, calculating the non-interference smooth drum-shaped cutter shaft vector: designating a cutting contact point as four cutter shaft characteristic points at the boundary line of four edges between a front edge curved surface, a rear edge curved surface, a blade basin curved surface and a blade back curved surface on any cutting line on the blade cutting contact point track, defining an initial non-interference cutter shaft vector for a drum cutter cutting forward-leaning angle and a side leaning angle corresponding to the four cutter shaft characteristic points, calculating the drum cutter shaft vector corresponding to each cutting contact point by combining a quaternion interpolation method, and obtaining the non-interference smooth drum cutter shaft vector after carrying out non-interference iterative inspection on a main blade and an adjacent blade on the cutter shaft vector interpolated by the quaternion;
step four, calculating the knife position of the drum-shaped knife: and C, calculating drum-shaped cutter positions of all the cutting contacts on the curved surface according to the normal vector of the curved surface corresponding to any cutting contact of the drum-shaped cutter and the drum-shaped cutter shaft vector obtained in the third step, thereby obtaining the path track of the blade machined by the drum-shaped cutter.
Further, the specific calculation steps of the diameter of the tool bar of the drum-shaped tool and the maximum equivalent radius of the cutting edge part of the drum-shaped tool in the step one are as follows:
the cutting edge of the drum-shaped knife is formed by a radian with radius of R 1 The point and a radian radius of R 2 The side edge of (1); the diameter of the drum-shaped cutter bar is D, and O is respectively arranged on the rotation central line of the drum-shaped cutter 1 、O 3 、O 4 Three points, said O 1 The point is the central point of the arc of the tool nose, and the point is O 3 The point is the radian radius R 2 Point of intersection with the tool centerline, O 4 The point is the central point of the interface of the cutting edge and the straight shank of the drum-shaped knife; any blade cutting contact point P on the drum-shaped knife 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 surface normal vector N and the cutter shaft vector T is arranged in the N-T plane 3 The curved surface normal vector of each cutting contact point on the cutting edge of the drum-shaped knife always passes through the point O3, and any cutting edge cutting contact point P c To the intersection point O 3 A distance of R 3 Then, there 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 the selected drum-shaped cutter bar is always smaller than the swinging cutter distance, and simultaneously, in order to avoid self-interference of the selected drum-shaped cutter when the selected drum-shaped cutter cuts the curved surface of the blade, the radian radius R 2 The maximum equivalent radius of the blade profile is the minimum curvature radius of the blade profile curved surface.
Further, the specific calculation steps of the number of cutting contacts on the spiral cutting line for machining on the curved surface of the four-segment blade in the second step are as follows:
taking the initial cutting position as P under the u-v plane coordinate system start And a cutting-end position P end According to the last discrete point on the curved surface of the previous blade as the first discrete point on the curved surface of the next bladeDiscrete points for avoiding the superposition of boundary points of two adjacent curved surfaces on the same spiral cutting line, planning the contact points of the four-section blade curved surfaces, and obtaining:
a 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 number of cutting contacts of one cutting line on the curved surface of the four-section blade is respectively; n is 1 、n 2 、n 3 And n 4 The distance between adjacent contact points is the minimum step length, and n is connected in sequence 1 、n 2 、n 3 And n 4 Thus obtaining a cutting and touching line.
Further, the second step further includes: and re-parameterizing the u-v coordinate system of the complete blade curved surface damaged in uniformity during boundary line segmentation, and mapping to obtain the u-v plane coordinate system of the blade curve.
Further, the third step is specifically: regarding the cutting part of the drum-shaped cutter as a ball-end cutter cutting edge with the radius same as the maximum equivalent radius of the drum-shaped cutter cutting edge, and thus calculating the cutter axis vectors corresponding to all the contact points on any feed track comprises the following specific steps:
31) designating four cutter shaft characteristic points as cutting contact points at the boundary lines of four edges among a front edge curved surface, a rear edge curved surface, a blade basin curved surface and a blade back curved surface on any cutting line on the blade cutting contact point track, and defining an initial non-interference cutter shaft vector for a drum cutter cutting forward rake angle and a drum cutter cutting side drift angle corresponding to the four cutter shaft characteristic points;
32) according to the cutter-blade space distance of the cutter-shaft characteristic point corresponding to the cutter-shaft vector, interference judgment of a main blade of a blisk and two adjacent blades is carried out on the cutter-shaft vector, the cutter-shaft vector smaller than the safety inspection allowance is regarded as an interference cutter shaft, if the safety inspection allowance is not smaller than 0.3mm, the initial slip angle and the forward rake angle are modified, and iteration is modified until all the cutter-shaft vectors pass interference inspection;
33) calculating the cutter shaft vectors corresponding to the tangent contact points except the characteristic points at the boundary line of the front edge and the rear edge by a quaternion interpolation algorithm to obtain the cutter shaft vector corresponding to any tangent contact point between the two characteristic points;
34) extracting a cutter shaft vector interpolated by quaternions in the cutting line to carry out interference inspection on a main blade and two adjacent blades, wherein 20-30 points are respectively selected on the basin surface of the blade back, and 10-15 points are respectively selected on the front edge head and the rear edge head; when interference occurs, optimizing the initial slip angle and the anteversion angle of the feature cutter shaft vector of two boundaries of the feature region where the interference point is located, updating, and then performing interpolation calculation and interference inspection again until all cutter shafts pass through interference inspection.
Further, the quaternion interpolation algorithm connects two specified vectors by using an interpolation vector on the maximum circular arc of the spherical surface, and specifically comprises the following steps:
given two designated arbor vectors q 1 (q 1x ,q 1y ,q 1z )、q n (q nx ,q ny ,q nz ) Interpolating between these two vectors to obtain q i The calculation formula of (2) is as follows:
wherein θ ═ arccos (q) 1 ·q n )，
Let a starting point P 1 And a termination point P n The feature vector of (a) is T 1 、T 2 The contact cutting point track between the two is obtained according to the previously planned mode { P } i I is 1, …, n (n is the total number of contact points), in the contact point track generation method, the arc length of the curve between two adjacent contact points on the same cutting line is changed, the distance between two adjacent points is in direct proportion to the corresponding vector corner, and P is the sum of the distance between two adjacent points 1 And P n The total length of the contact point trace between is S 1n Namely:
from a starting point P 1 To the current contact point P i The track length of (a) is:
the parameter t is therefore expressed as:
while theta is arccos (T) 1 ·T 2 ) The resulting cut contact P i The arbor vector of (a) is:
thus obtaining the corresponding cutter axis vector of any contact point between the two characteristic points.
Further, the fourth step is specifically:
the known drum-shaped cutter has a unique cutter position point P under the conditions of a curved surface normal vector of a curved surface contact point and a cutter shaft vector obtained by planning the contact point t Then at a certain contact point P c Where the arbor vector T is known, the drum tool location P t The solution is as follows:
1) selecting a cutting contact point 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 R 2 Cutting side edge center point P of O2 The center point of the edge:
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 a vector T n To obtain a distance R 2 -R tool Point P of O3 Then, then
P O3 ＝P O2 +(R 2 -R tool )·T n
5) Obtaining the knife position point P of the drum-shaped knife t The coordinate calculation formula of (2) is:
P t ＝P O3 -L dis ·T
l in the formula dis Is P O3 To the knife tip P t Is constant.
The invention has the beneficial effects that: the method fully utilizes the structural characteristics of the drum-shaped cutter to calculate the cutter position track of the drum-shaped cutter for milling the blisk blade, and effectively improves the surface quality and milling efficiency of processing the blisk blade.
Drawings
FIG. 1 is a schematic view of a u-v plane coordinate system for curved surface expansion and mapping of four blade sections according to the present invention;
FIG. 2 is a schematic diagram of the trace of the contact points of the four-segment blade curved surface according to the present invention;
FIG. 3 is a schematic view of the geometry of the drum knife of the present invention;
FIG. 4 is a schematic diagram of quaternion interpolation according to the present invention;
FIG. 5 is a schematic view of a non-interference fairing drum knife axis vector of the present invention;
FIG. 6 is a schematic diagram of a solution for the location of the drum knife in accordance with the present invention;
FIG. 7 is a diagram showing the effect of the ball nose cutter and the drum cutter on the surface quality of the finish-milled blade with the same cutting parameters;
FIG. 8 is a schematic view of a blisk blade configuration for use in accordance with an exemplary embodiment of the present invention;
FIG. 9 is a structural schematic view of the radius of curvature of a blisk blade according to an exemplary embodiment of the present invention;
FIG. 10 is a schematic diagram of a spiral path trajectory for a drum knife tool in accordance with an exemplary embodiment of the present invention.
Detailed Description
The principles and features of this invention are described below in conjunction with the following drawings, which are set forth by way of illustration only and are not intended to limit 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 of machining a blisk blade with a drum cutter includes the steps of:
determining the diameter of a tool bar of a drum-shaped tool 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 tool according to the minimum curvature radius of a blade profile curved surface and the drum-shaped tool structure to obtain the drum-shaped tool structure suitable for machining the blades of the blisk;
in the step one, the specific calculation steps of the diameter of the tool bar of the drum-shaped tool and the maximum equivalent radius of the cutting edge part of the drum-shaped tool are as follows:
as shown in FIG. 3, the cutting edge of the drum knife has a curvature radius R 1 The point and a radian radius of R 2 The side edge of (1); the diameter of the drum-shaped cutter bar is D, and O is respectively arranged on the rotation central line of the drum-shaped cutter 1 、O 3 、O 4 Three points, said O 1 The point is the central point of the arc of the tool nose, and the point is O 3 The point is the radian radius R 2 Point of intersection with the tool centerline, O 4 The point is the central point of the interface of the cutting edge and the straight shank of the drum-shaped knife; any blade cutting contact point P on the drum-shaped knife 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 surface normal vector N and the cutter shaft vector T is arranged in the N-T plane 3 The curved surface normal vector of each cutting contact point on the cutting edge of the drum-shaped knife always passes through the point O3, and any cutting edge cutting contact point P c To the intersection point O 3 A distance of R 3 Then, there 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 the selected drum-shaped cutter bar is always smaller than the swinging cutter distance, and simultaneously, in order to avoid self-interference of the selected drum-shaped cutter when the selected drum-shaped cutter cuts the curved surface of the blade, the radian radius R 2 The maximum equivalent radius of the blade profile is 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 blade of the blisk machined by the drum cutter: creating a segmented 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, establishing four blade curved surfaces of the blade by taking a boundary line of the blade back curved surface and the front edge curved surface as a boundary, mapping the four blade curved surfaces in a u-v plane coordinate system of a blade curve, calculating to obtain the number of contact points on the four blade curved surfaces, designating the minimum step length between two adjacent contact points, sequentially connecting the contact points on the four blade curved surfaces to obtain a row of contact lines, and determining the row distance of the contact lines by combining the residual knife line height of a drum-shaped knife and a spiral cutting feed so as to generate a blade contact point track;
the specific calculation steps of the number of cutting contacts on the spiral cutting line for processing on the curved surface of the four-section blade in the second step are as follows:
as shown in FIG. 2, the initial cutting position is taken as P in the u-v plane coordinate system start And a cutting-end position P end And taking the last discrete point on the curved surface of the previous blade as a first discrete point on the curved surface of the next blade, and planning the contact points on the curved surfaces of the four segments of blades to obtain the following steps:
a cutting contact point on the cutting spiral lineA 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 number of cutting contacts of one cutting line on the curved surface of the four-section blade is respectively; n is 1 、n 2 、n 3 And n 4 The distance between adjacent contact points is the minimum step length, and n is connected in sequence 1 、n 2 、n 3 And n 4 Thus obtaining a cutting and touching line.
The second step further comprises: and re-parameterizing the u-v coordinate system of the complete blade curved surface damaged in uniformity during boundary line segmentation, and mapping to obtain the u-v plane coordinate system of the blade curve.
Step three, calculating the non-interference smooth drum-shaped cutter shaft vector: designating a cutting contact point as four cutter shaft characteristic points at the boundary line of four edges between a front edge curved surface, a rear edge curved surface, a blade basin curved surface and a blade back curved surface on any cutting line on the blade cutting contact point track, defining an initial non-interference cutter shaft vector for a drum cutter cutting forward-leaning angle and a side leaning angle corresponding to the four cutter shaft characteristic points, calculating the drum cutter shaft vector corresponding to each cutting contact point by combining a quaternion interpolation method, and obtaining the non-interference smooth drum cutter shaft vector after carrying out non-interference iterative inspection on a main blade and an adjacent blade on the cutter shaft vector interpolated by the quaternion;
as shown in fig. 3, the third step specifically includes: regarding the cutting part of the drum-shaped cutter as a ball-end cutter cutting edge with the radius same as the maximum equivalent radius of the drum-shaped cutter cutting edge, and thus calculating the cutter axis vectors corresponding to all the contact points on any feed track comprises the following specific steps:
31) designating four cutter shaft characteristic points as cutting contact points at the boundary lines of four edges between a front edge curved surface, a rear edge curved surface, a blade basin curved surface and a blade back curved surface on any cutting line on the blade cutting contact point track, and defining initial non-interference cutter shaft vectors for the cutting forward rake angles and the side rake angles of the drum cutters corresponding to the four cutter shaft characteristic points;
32) according to the cutter-blade space distance of the cutter-shaft characteristic point corresponding to the cutter-shaft vector, interference judgment of a main blade of a blisk and two adjacent blades is carried out on the cutter-shaft vector, the cutter-shaft vector smaller than the safety inspection allowance is regarded as an interference cutter shaft, if the safety inspection allowance is not smaller than 0.3mm, the initial slip angle and the forward rake angle are modified, and iteration is modified until all the cutter-shaft vectors pass interference inspection;
33) calculating the cutter shaft vectors corresponding to the tangent contact points except the characteristic points at the boundary line of the front edge and the rear edge by a quaternion interpolation algorithm to obtain the cutter shaft vector corresponding to any tangent contact point between the two characteristic points;
34) extracting a cutter shaft vector interpolated by quaternions in the cutting line to carry out interference inspection on a main blade and two adjacent blades, wherein 20-30 points are respectively selected on the basin surface of the blade back, and 10-15 points are respectively selected on the front edge head and the rear edge head; when interference occurs, the initial slip angle and the forward rake angle of the feature cutter axis vector of two boundaries of the feature region where the interference point is located are optimized, interpolation calculation and interference check are carried out again after updating until all cutter axes pass through interference check, and the interference-free smooth drum-shaped cutter axis vector is obtained through calculation, as shown in fig. 5.
According to the calculation method of the step length between the cutting contacts and the step distance between the adjacent cutting lines, the cutter axis vector of the cutter at any cutting contact position of the blade can be obtained by combining the calculation method of the cutter axis vector corresponding to the cutting contacts, and meanwhile, the optimization is carried out by adopting a variable slip angle mode from the blade tip to the blade root, so that the cutting contact area of the cutting edge of the drum-shaped cutter is gradually transited when the drum-shaped cutter is in different cutting lines, the overuse of the drum-shaped cutter in the same latitude (the latitude change is smaller) of the spherical conical surface of the cutting edge 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 by using an interpolation vector on the maximum circular arc of the spherical surface, and specifically includes:
given two designated arbor vectors q 1 (q 1x ,q 1y ,q 1z )、q n (q nx ,q ny ,q nz ) Interpolating between these two vectors to obtain q i The calculation formula of (2) is as follows:
wherein θ ═ arccos (q) 1 ·q n )，
Let a starting point P 1 And a termination point P n The feature vector of (a) is T 1 、T 2 The contact cutting point track between the two is obtained according to the previously planned mode { P } i I is 1, …, n (n is the total number of contact points), in the contact point track generation method, the arc length of the curve between two adjacent contact points on the same cutting line is changed, the distance between two adjacent points is in direct proportion to the corresponding vector corner, and P is the sum of the distance between two adjacent points 1 And P n The total length of the contact point trace between is S 1n Namely:
from a starting point P 1 To the current contact point P i The track length of (a) is:
the parameter t is therefore expressed as:
while theta＝arccos(T 1 ·T 2 ) The resulting cutting contact point P i The arbor vector of (a) is:
thus obtaining the corresponding cutter axis vector of any contact point between the two characteristic points.
Step four, calculating the knife position of the drum-shaped knife: and C, calculating drum-shaped cutter positions of all the cutting contacts on the curved surface according to the normal vector of the curved surface of the drum-shaped cutter at any cutting contact and the drum-shaped cutter shaft vector obtained in the step three, so as to obtain the path track of the blade machined by the drum-shaped cutter.
Specifically, as shown in fig. 6, it is known that the drum cutter has a unique cutter location point P under the conditions of the normal vector of the curved surface contact point and the cutter axis vector obtained by planning the contact point t Then at a certain contact point P c Where the arbor vector T is known, the drum tool location P t The solution is as follows:
1) selecting a cutting contact point 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 R 2 Cutting side edge center point P of O2 The center point of the edge:
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 a vector T n To obtain a distance R 2 -R tool Point P of O3 Then, then
P O3 ＝P O2 +(R 2 -R tool )·T n
5) Obtaining the knife position point P of the drum-shaped knife t The coordinate calculation formula of (2) is:
P t ＝P O3 -L dis ·T
l in the formula dis Is P O3 To the knife tip P t Is constant.
And generating a milling path track of a drum-shaped cutter of the blade according to the parameters obtained by the method, and after post-processing, realizing finish machining milling of the part on a five-axis machining center.
Calculation example: as shown in fig. 8-10, for a blisk blade, the calculation using the drum cutter machining method according to the present invention is as follows:
the measured minimum blade tip distance H1 is 21.04mm, the minimum channel distance H2 is 17.23mm, the blade length L is 65mm, as shown in fig. 8 and 9, only the curved surface on the side of the blade basin is a concave curved surface, the minimum curvature radius of the blade is 94.75mm through calculation, the cutter bar diameter D of the drum cutter is smaller than the swing 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 curved surface model of the blade is combined, and the arc radius R of the cutting edge part of the drum-shaped knife 2 80mm is selected, and the arc radius R1 of the tool nose is 3 mm. The blade length is 65mm, considering that the drum knife handle will clamp about 40mm, the total drum knife tool length is 110 mm.
By using the drum cutter with the selected structural parameters and combining the processing method of the drum cutter of the blisk blade, a spiral path track of the cutter shown in fig. 10 can be generated, so that the finish milling of the blade is completed, the quality and tolerance of the blade surface meet the requirements through actual tests and detection, and the processing time is greatly shortened compared with that of a ball head cutter.
The invention solves the difficulty of milling the blades of the blisk by the drum-shaped cutter. The quality of the processed surface of the curved surface processed by the method is opposite to that of the processed surface of the ball-end cutter under the condition of the same cutting parameters, for example, as shown in fig. 7, the surface of the curved surface processed by the method has neat tool marks, clear lines and high surface quality, and the generated processed surface is smoother mainly because the drum-shaped cutter is in line contact during cutting. The same cutting residual height is controlled, and when the same curved surface characteristic is cut by using a drum-shaped cutter with the same diameter and the same feeding speed and a ball-end cutter, the actual cutting time comparison shows that the finishing efficiency of the drum-shaped cutter is far higher than that of a common ball-end structure cutter, and the processing time is about 45 percent of that of the ball-end cutter.
According to the experimental result, the method can effectively improve the quality of the machined surface of the blisk blade and the milling efficiency, thereby reducing the machining cost of the blade.
The above description is only for the purpose of illustrating the preferred embodiments of the present invention and is not to be construed as limiting the invention, and any modifications, equivalents, improvements and the like that fall within the spirit and principle of the present invention are intended to be included therein.
Claims (7)
1. A method for machining a blisk blade with a drum cutter, comprising the steps of:
determining the diameter of a tool bar of a drum-shaped tool 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 tool according to the minimum curvature radius of a blade profile curved surface and the drum-shaped tool structure to obtain the drum-shaped tool structure suitable for machining the blades of the blisk;
step two, calculating the contact cutting track of the blade of the blisk machined by the drum-shaped cutter: creating a segmented 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, establishing four blade curved surfaces of the blade by taking a boundary line of the blade back curved surface and the front edge curved surface as a boundary, mapping the four blade curved surfaces in a u-v plane coordinate system of a blade curve, calculating to obtain the number of contact points on the four blade curved surfaces, designating the minimum step length between two adjacent contact points, sequentially connecting the contact points on the four blade curved surfaces to obtain a row of contact lines, and determining the row distance of the contact lines by combining the residual knife line height of a drum-shaped knife and a spiral cutting feed so as to generate a blade contact point track;
step three, calculating the non-interference smooth drum-shaped cutter shaft vector: designating a cutting contact point as four cutter shaft characteristic points at the boundary line of four edges between a front edge curved surface, a rear edge curved surface, a blade basin curved surface and a blade back curved surface on any cutting line on the blade cutting contact point track, defining an initial non-interference cutter shaft vector for a drum cutter cutting forward-leaning angle and a side leaning angle corresponding to the four cutter shaft characteristic points, calculating the drum cutter shaft vector corresponding to each cutting contact point by combining a quaternion interpolation method, and obtaining the non-interference smooth drum cutter shaft vector after carrying out non-interference iterative inspection on a main blade and an adjacent blade on the cutter shaft vector interpolated by the quaternion;
step four, calculating the knife position of the drum-shaped knife: and C, calculating drum-shaped cutter positions of all the cutting contacts on the curved surface according to the normal vector of the curved surface of the drum-shaped cutter at any cutting contact and the drum-shaped cutter shaft vector obtained in the step three, so as to obtain the path track of the blade machined by the drum-shaped cutter.
2. The method of claim 1, wherein the step one of calculating the drum cutter bar diameter and the drum cutter cutting edge portion maximum equivalent radius specifically comprises the steps of:
the cutting edge of the drum-shaped knife is formed by a radian with the radius of R 1 The point and a radian radius of R 2 The side edge of (1); the diameter of the drum-shaped cutter bar is D, and O is respectively arranged on the rotation central line of the drum-shaped cutter 1 、O 3 、O 4 Three points, said O 1 The point is the central point of the arc of the tool nose, and the point is O 3 The point is the radian radius R 2 Point of intersection with the tool centerline, O 4 The point is the central point of the interface of the cutting edge and the straight shank of the drum-shaped knife; any blade cutting contact point P on the drum-shaped knife 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 surface normal vector N and the cutter shaft vector T is arranged in the N-T plane 3 The curved surface normal vector of each cutting contact point on the cutting edge of the drum-shaped knife always passes through the point O3, and any cutting edge cutting contact point P c To the intersection point O 3 A distance of R 3 Then, there 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 the selected drum-shaped cutter bar is always smaller than the swinging cutter distance, and simultaneously, in order to avoid self-interference of the selected drum-shaped cutter when the selected drum-shaped cutter cuts the curved surface of the blade, the radian radius R 2 The maximum equivalent radius of the blade profile is the minimum curvature radius of the blade profile curved surface.
3. The method of claim 1, wherein the step two of calculating the number of cutting contacts in the spiral cutting line on the curved surface of the four-segment blade is as follows:
taking the initial cutting position as P under the u-v plane coordinate system start And a cutting-end position P end And taking the last discrete point on the curved surface of the previous blade as a first discrete point on the curved surface of the next blade, and planning the contact points on the curved surfaces of the four segments of blades to obtain the following steps:
a 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 number of cutting contacts of one cutting line on the curved surface of the four-section blade is respectively; n is 1 、n 2 、n 3 And n 4 The distance between adjacent contact points is the minimum step length, and n is connected in sequence 1 、n 2 、n 3 And n 4 One row of contact cutting lines is obtained by cutting the contacts.
4. The method of claim 1, further comprising in step two: and re-parameterizing the u-v coordinate system of the complete blade curved surface damaged in uniformity during boundary line segmentation, and mapping to obtain the u-v plane coordinate system of the blade curve.
5. The method of claim 1, wherein step three is embodied as: regarding the cutting part of the drum-shaped cutter as a ball-end cutter cutting edge with the radius same as the maximum equivalent radius of the drum-shaped cutter cutting edge, and calculating cutter axis vectors corresponding to all contact points on any feed track in the following specific steps:
31) designating four cutter shaft characteristic points as cutting contact points at the boundary lines of four edges among a front edge curved surface, a rear edge curved surface, a blade basin curved surface and a blade back curved surface on any cutting line on the blade cutting contact point track, and defining an initial non-interference cutter shaft vector for a drum cutter cutting forward rake angle and a drum cutter cutting side drift angle corresponding to the four cutter shaft characteristic points;
32) according to the cutter-blade space distance of the cutter-shaft characteristic point corresponding to the cutter-shaft vector, interference judgment of a main blade of a blisk and two adjacent blades is carried out on the cutter-shaft vector, the cutter-shaft vector smaller than the safety inspection allowance is regarded as an interference cutter shaft, if the safety inspection allowance is not smaller than 0.3mm, the initial slip angle and the forward rake angle are modified, and iteration is modified until all the cutter-shaft vectors pass interference inspection;
33) calculating the cutter shaft vectors corresponding to the tangent contact points except the characteristic points at the boundary line of the front edge and the rear edge by a quaternion interpolation algorithm to obtain the cutter shaft vector corresponding to any tangent contact point between the two characteristic points;
34) extracting a cutter shaft vector interpolated by quaternions in the cutting line to carry out interference inspection on a main blade and two adjacent blades, wherein 20-30 points are respectively selected on the basin surface of the blade back, and 10-15 points are respectively selected on the front edge head and the rear edge head; when interference occurs, optimizing the initial slip angle and the anteversion angle of the feature cutter shaft vector of two boundaries of the feature region where the interference point is located, updating, and then performing interpolation calculation and interference inspection again until all cutter shafts pass through interference inspection.
6. The method of claim 5, wherein the quaternion interpolation algorithm connects two designated vectors using an interpolation vector on the maximum circular arc of the sphere, specifically:
given two designated arbor vectors q 1 (q 1x ,q 1y ,q 1z )、q n (q nx ,q ny ,q nz ) Interpolating between these two vectors to obtain q i The calculation formula of (2) is as follows:
wherein θ ═ arccos (q) 1 ·q n )，
Let a starting point P 1 And a termination point P n The feature vector of (a) is T 1 、T 2 The contact cutting point track between the two is obtained according to the previously planned mode { P } i I is 1, …, n (n is the total number of contact points), in the contact point track generation method, the arc length of the curve between two adjacent contact points on the same cutting line is changed, the distance between two adjacent points is in direct proportion to the corresponding vector corner, and P is the sum of the distance between two adjacent points 1 And P n The total length of the contact point trace between is S 1n Namely:
from a starting point P 1 To the current contact point P i Rail (A)The trace length is:
the parameter t is therefore expressed as:
while theta is arccos (T) 1 ·T 2 ) The resulting cutting contact point P i The arbor vector of (a) is:
thus obtaining the corresponding cutter axis vector of any contact point between the two characteristic points.
7. The method of machining a blisk blade with a drum cutter as set forth in claim 1, wherein said step four is embodied by:
the known drum-shaped cutter has a unique cutter position point P under the conditions of a curved surface normal vector of a curved surface contact point and a cutter shaft vector obtained by planning the contact point t Then at a certain contact point P c Where the arbor vector T is known, the drum tool location P t The solution is as follows:
1) selecting a cutting contact point 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 R 2 Cutting side edge center point P of O2 The center point of the edge:
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 a vector T n To obtain a distance R 2 -R tool Point P of O3 Then, then
P O3 ＝P O2 +(R 2 -R tool )·T n
5) Obtaining the knife position point P of the drum-shaped knife t The coordinate calculation formula of (2) is:
P t ＝P O3 -L dis ·T
l in the formula dis Is P O3 To the knife tip P t Is constant.
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