A kind of five axis ball-end milling geometric error compensation methods
Technical field
The present invention relates to NC Machining Error compensation field more particularly to Milling Process geometric error compensation technologies.
Background technology
Five-axis milling has unique advantage in complex surface machining manufacture view, is widely used for space flight, aviation, boat
The processing of complex parts in the every field such as sea, automobile, national defence.Five-axis milling high-precision manufacture, which also becomes, weighs a country
The one of the important signs that of advanced manufacture level.The machining accuracy of five-axis milling is affected by many factors, wherein geometric error and heat
Error is one of main error source, accounts for 60% or so of total foozle.Since geometric error has systematicness high, repeated
The characteristics of stablizing and easily measure in good, long-time, geometric error compensation becomes a kind of economical and effective for improving five-axis milling precision
Important means.
Existing geometric error compensation technology is made by means of different adjustment location attitude of the cutter under the influence of lathe geometric error
Practical location attitude of the cutter be as closely as possible to design location attitude of the cutter, to improve five-axis robot precision.Many error compensation skills
Art is resonable to refer to simulating, verifying stage effectiveness it is obvious that still due to having ignored Tool in Cutting mechanism in practical milling, reality adds
Work efficiency fruit is far smaller than expected.Theoretically, error compensation should first ensure that the original cutter-contact point trace of curved surface is constant, need in cutter
Pose must be using original cutter-contact point as pivot point when adjusting.
Surface texture pattern is one of the important indicator for weighing workpiece surface quality.Surface texture directly influences workpiece
Physical property, mechanical performance and service life etc., abrasion, lubrication shape such as the contact condition, friction surface of part junction
State, vibration, noise, sealing, coating quality, corrosion resistance, electric conductivity, thermal conductivity and reflectivity.In error compensation procedure, no
Addition of constraints arbitrarily adjustment machining code or location attitude of the cutter may cause Machining of Curved Surface texture it is irregular change may also can make
At the wide-angle variations of rotary shaft so that cutter leaves hollow trace in workpiece surface when actual cut.At present to five-axis milling
The research for causing surface texture to change because of correction motion axis amount of exercise in error compensation is seldom, also lacks corresponding reply and arranges
It applies.
Invention content
The object of the present invention is to provide a kind of five axis ball-end milling geometric error compensation methods, it can be efficiently solved from generation
Table workpiece
The technical issues of knife rail-engaging mark of texture sets out, the compensation geometric error of realization workpiece texture constraint.
The purpose of the present invention is achieved through the following technical solutions:A kind of five axis ball-end milling geometric error compensation sides
Method includes the following steps:
Step 1 considers five-axle number control machine tool structural parameters, establishes five-axle number control machine tool direct kinematics equation and post-processing
Program;
Step 2 obtains workpiece ideal knife according to work pieces process code in conjunction with five-axle number control machine tool direct kinematics equation
Has posture file;
Step 3, in conjunction with workpiece coordinate system bottom tool attitude angle, establish rose cutter location attitude of the cutter and represent workpiece texture
Transformational relation between cutter-contact point;
Step 4, according to exponent product theory, introduce ideal location attitude of the cutter, establish five axis ball-end milling synthetic geometry error solutions
Analyse model;
Step 5 according to rose cutter location attitude of the cutter and represents the transformational relation and five axis between the cutter-contact point of workpiece texture
Numerically-controlled machine tool direct kinematics establish cutter-contact point safeguard in five axis ball-end milling geometric error compensations;
Step 6, application group's intelligent optimization algorithm, establish five axis ball-end milling geometric error compensations fitness function,
Population Initialization strategy, the rotation shaft angle being compensated;
Step 7, according to cutter-contact point safeguard, calculate the translation shaft amount of exercise of the rotation shaft angle of compensation, be compensated
Machining code;
Step 8 reads workpiece ideal location attitude of the cutter file, and the compensation of each location attitude of the cutter is calculated according to step 4 to step 7
Machining code.
Preferably, five-axle number control machine tool structural parameters are two rotating shaft axis in lathe coordinate system in the step 1
Location parameter;The five axis post processors established include the bilingual resolution policy of rotary shaft amount of exercise, obtain all kinematic axis phases
For the real motion amount of its zero position;
Preferably, in the step 3 combine workpiece coordinate system bottom tool attitude angle, establish rose cutter location attitude of the cutter with
The transformational relation between the cutter-contact point of workpiece texture is represented, specific steps include:
Step 3.1 establishes cutter-contact point local coordinate system on workpiece, and coordinate origin is cutter-contact point, and x-axis is knife at cutter-contact point
Rail-engaging mark tangent line rector f, z-axis are workpiece normal vector n at cutter-contact point, and y-axis vector b is established by right hand rule;
Step 3.2 defines cutter-contact point coordinate system bottom tool attitude angle, establishes cutter rotation angle θ and phase around z-axis rotation
For the cutter inclination angle phi of z-axis;
Step 3.3, in conjunction on workpiece cutter-contact point local coordinate system definition and cutter-orientation angle, according to rose cutter geometry knot
Structure parameter establishes rose cutter location attitude of the cutter and represents turn between the cutter-contact point of workpiece texture according to coordinate system transformational relation
Relationship is changed, obtaining rose cutter cutter-orientation vector sum rose cutter center cutter L-expression is:
Wherein T indicates that rose cutter cutter-orientation vector, P indicate rose cutter center cutter position, R2Indicate bulb milling
Knife radius, C indicate to represent the cutter-contact point coordinate of workpiece texture.
Preferably, introducing ideal location attitude of the cutter according to exponent product theory in the step 4, establishing five axis ball-end millings
Synthetic geometry error exciting model, specific steps include:
Step 4.1 establishes each kinematic axis geometric error spinor and exponential matrix according to exponent product theory, in conjunction with five number of axle
Lathe topological structure is controlled, real index product matrix of the geometric error effect bottom tool relative to workpiece is established, it is opposite to obtain cutter
In the practical location attitude of the cutter of workpiece;
Step 4.2, according to five-axle number control machine tool direct kinematics equation, introduce ideal location attitude of the cutter, five axis ball-end millings
Synthetic geometry error model is expressed as cutter and subtracts ideal location attitude of the cutter relative to the practical location attitude of the cutter of workpiece;
Step 4.3, in conjunction with five-axle number control machine tool geometric error mathematic(al) representation, establish five axis ball-end milling synthetic geometries mistake
Poor analytic modell analytical model.
Preferably, according to rose cutter location attitude of the cutter and being represented between the cutter-contact point of workpiece texture in the step 5
Transformational relation and five-axle number control machine tool direct kinematics are established cutter-contact point guarantee in five axis ball-end milling geometric error compensations and are arranged
It applies, specific steps include:
Step 5.1 according to rose cutter location attitude of the cutter and represents the transformational relation between the cutter-contact point of workpiece texture, analysis
Rose cutter center cutter L-expression converts cutter-contact point guarantee to rose cutter center cutter position assurance;
Step 5.2 reads rose cutter center cutter position in location attitude of the cutter;
Step 5.3, foundation five-axle number control machine tool direct kinematics, input rotation shaft angle, calculate in rose cutter cutter
The corresponding translation shaft amount of exercise of rotation shaft angle at heart position.
Preferably, the step 6 application group intelligent optimization algorithm, establishes five axis ball-end milling geometric error compensations
Fitness function, Population Initialization strategy, the rotary shaft amount of exercise being compensated, specific steps include:
Step 6.1, according to five axis ball-end milling synthetic geometry error exciting models, using comprehensive ball head knife center cutter position
Error is set, the fitness function of five axis ball-end milling geometric error compensations is established;
Step 6.2, using rotation shaft angle as group;
Step 6.3 defines group's rectangle's feasible region centered on ideal rotation shaft angle, and establishes Population Initialization strategy
For:
Wherein p indicates group, (αo,γo) indicate ideal rotation shaft angle, αlAnd γlGroup's rectangle's feasible region is indicated respectively
Long and wide half, r1And r2∈ [0,1] indicates two random numbers.
Step 6.5, according to cutter-contact point safeguard in five axis ball-end milling geometric error compensations, calculate the translation shaft of group
Amount of exercise, the fitness function for substituting into five axis ball-end milling geometric error compensations calculate group's fitness.
Step 6.6, setting group's fitness required precision and group position update maximum times, are optimized according to swarm intelligence
Algorithm, the rotation shaft angle being compensated.
Preferably, Swarm Intelligent Algorithm is in the step 6:Particle swarm optimization algorithm, chicken group algorithm, ant colony are calculated
Method.
The present invention is a kind of five axis ball-end milling geometric error compensation methods, and specific advantageous effect is:The present invention is several
The constraint that workpiece texture is considered in what error compensation procedure, passes through rose cutter location attitude of the cutter and the cutter-contact point for representing workpiece texture
Between transformational relation, establish cutter-contact point guarantee strategies, reduce geometric error influence while ensure workpiece texture quality.It should
Method can further improve five-axis machine tool machining accuracy and workpiece surface quality.
Description of the drawings
Fig. 1 is flow chart of the present invention;
Fig. 2 is mouse-type workpiece figure;
Fig. 3 is the general transformational relation signal between milling cutter tool pose and the cutter-contact point for representing workpiece texture of the present invention
Figure;
Fig. 4 a are that population initializes schematic diagram;
Fig. 4 b are population location updating schematic diagram;
Fig. 5 is not compensate and work pieces process code after compensation;
Fig. 6 a are the front and back workpiece application condition figure of compensation;
Fig. 6 b are that the front and back workpiece error of compensation promotes degree figure.
Specific implementation mode
The present invention will be further described in the following with reference to the drawings and specific embodiments.
Attached drawing 1 show a kind of five axis ball-end milling geometric error compensation method flow diagrams of the invention, and attached drawing 2 show mouse
Mark type workpiece illustrates five axis ball-end millings so that SmartCNC500_DRTD five-axle number control machine tool ball-end millings process this workpiece as an example
Geometric error compensation method.
Step 1 considers that five-axle number control machine tool structural parameters, SmartCNC500_DRTD five-axle number control machine tool structural parameters are
The position of A axis and C axis rotation axis in lathe coordinate system;Establish five-axle number control machine tool direct kinematics equation and post-processing journey
Sequence, five axis post processors propose the bilingual resolution policy of rotary shaft amount of exercise, have obtained all kinematic axis relative to its zero position
Real motion amount;
Step 2, with reference to the accompanying drawings mouse-type workpiece ideal machining code shown in 5a, in conjunction with five-axle number control machine tool positive movement
Equation is learned, the workpiece ideal location attitude of the cutter file is obtained;
Step 3, in conjunction with workpiece coordinate system bottom tool attitude angle, establish rose cutter location attitude of the cutter and represent workpiece texture
Transformational relation between cutter-contact point, specific steps include:
Step 3.1 establishes cutter-contact point local coordinate system on workpiece, and coordinate origin is cutter-contact point, and x-axis is knife at cutter-contact point
Rail-engaging mark tangent line rector f, z-axis are workpiece normal vector n at cutter-contact point, and y-axis vector b is established by right hand rule, shown in attached drawing 3
For the transformational relation schematic diagram between general milling cutter tool pose and the cutter-contact point for representing workpiece texture;
Step 3.2 defines cutter-contact point coordinate system bottom tool attitude angle, establishes cutter rotation angle θ and phase around z-axis rotation
For the cutter inclination angle phi of z-axis;
Step 3.3, in conjunction on workpiece cutter-contact point local coordinate system definition and cutter-orientation angle, according to rose cutter without flat
Part only has the characteristics of bulb blade, according to relationship shown in coordinate system transformational relation combination attached drawing 3, establishes rose cutter cutter position
Transformational relation between appearance and the cutter-contact point for representing workpiece texture obtains rose cutter cutter-orientation vector sum rose cutter cutter
Center expression formula is:
Wherein T indicates that rose cutter cutter-orientation vector, P indicate rose cutter center cutter position, R2Indicate bulb milling
Knife radius.Expansion formula obtains rose cutter cutter-orientation vector sum rose cutter center cutter position:
Step 4, according to exponent product theory, introduce ideal location attitude of the cutter, establish five axis ball-end milling synthetic geometry error solutions
Model is analysed, specific steps include:
Step 4.1 establishes each kinematic axis geometric error spinor and exponential matrix according to exponent product theory, in conjunction with five number of axle
Lathe topological structure is controlled, real index product matrix of the geometric error effect bottom tool relative to workpiece is established, it is opposite to obtain cutter
In the practical location attitude of the cutter of workpiece;
Step 4.2, according to five-axle number control machine tool direct kinematics equation, introduce ideal location attitude of the cutter, five axis ball-end millings
Synthetic geometry error model is expressed as cutter and subtracts ideal location attitude of the cutter relative to the practical location attitude of the cutter of workpiece, is expressed as:
Wherein [pex,pey,pez]TIndicate five axis ball-end milling center cutter position Synthesis geometric errors, [tex,tey,tez]T
Indicate five axis ball-end milling cutter-orientation synthetic geometry errors, PrIndicate practical center cutter position of the cutter relative to workpiece, Pi
Indicate ideal center cutter position of the cutter relative to workpiece, TrIndicate practical cutter-orientation of the cutter relative to workpiece, TiIt indicates
Ideal cutter-orientation of the cutter relative to workpiece.
Step 4.3, in conjunction with five-axle number control machine tool geometric error mathematic(al) representation, establish five axis ball-end milling synthetic geometries mistake
Poor analytic modell analytical model, is expressed as:
Step 5 according to rose cutter location attitude of the cutter and represents the transformational relation and five axis between the cutter-contact point of workpiece texture
Numerically-controlled machine tool direct kinematics, establish cutter-contact point safeguard in five axis ball-end milling geometric error compensations, and specific steps include:
Step 5.1 according to rose cutter location attitude of the cutter and represents the transformational relation between the cutter-contact point of workpiece texture, analysis
Rose cutter center cutter L-expression finds rose cutter center cutter position and cutter-contact point correlation and and cutter-orientation
Etc. unrelated, as long as ensureing that rose cutter center cutter position is constant, cutter-orientation variation will not impact cutter-contact point.According to
This finds to convert cutter-contact point guarantee to rose cutter center cutter position assurance;
Step 5.2 reads rose cutter center cutter position in location attitude of the cutter;
Step 5.3, foundation five-axle number control machine tool direct kinematics, input rotation shaft angle, calculate in rose cutter cutter
The corresponding translation shaft amount of exercise of rotation shaft angle at heart position.
Step 6, application group's intelligent optimization algorithm, establish five axis ball-end milling geometric error compensations fitness function,
Population Initialization strategy, the rotation shaft angle being compensated.This example uses particle swarm optimization algorithm, and specific steps include:
Step 6.1, according to five axis ball-end milling synthetic geometry error exciting models, using comprehensive ball head knife center cutter position
Error is set, the fitness function for establishing five axis ball-end milling geometric error compensations is:
Step 6.2, using rotation shaft angle as population;
Step 6.3 defines population rectangle's feasible region centered on ideal rotation shaft angle, and attached drawing 4a show population
Rectangle's feasible region, and establish Population Initialization strategy and be:
Wherein p indicates population, (αo,γo) indicate ideal rotation shaft angle, αlAnd γlIndicate that population rectangle can respectively
Row domain is grown and wide half, r1And r2∈ [0,1] indicates two random numbers.And population location Update Strategy is established, such as attached drawing 4
It is shown.
Step 6.5, according to cutter-contact point safeguard in five axis ball-end milling geometric error compensations, calculate the translation shaft of particle
Amount of exercise, the fitness function for substituting into five axis ball-end milling geometric error compensations calculate population fitness.
Step 6.6, setting population fitness required precision and location updating maximum times, according to particle swarm optimization algorithm
Step calculates population fitness and carries out location updating, finally obtains the rotation shaft angle of compensation.
Step 7, according to ideal cutter-contact point safeguard, calculate the translation shaft amount of exercise of the rotation shaft angle of compensation, obtain
Compensate machining code;
Step 8 reads workpiece ideal location attitude of the cutter file, inputs C shaft positions in the five-axle number control machine tool structural parameters
[244.5247,105.9248,0]TMm and A shaft positions [0,105.9232, -237.154]TMm is counted according to step 4 to step 7
Calculate the compensation machining code of each location attitude of the cutter, rose cutter radius R in step 42For 3mm, α in step 6lAnd γlIt is respectively set
It it is 10 °, population fitness required precision is 0.0005mm, and location updating maximum times are set as 50, read each cutter position
Compensation machining code, the compensation machining code that attached drawing 5b is shown is calculated in appearance information.
In order to verify a kind of validity of five axis ball-end milling geometric error compensation method of the present invention, ideal add is respectively adopted
Work code and compensation machining code use rose cutter workpieces processing in the five-axle number control machine tool, then with two workpiece of measurement
Error, attached drawing 6a show the front and back application condition figure of compensation, and workpiece error reduces degree after attached drawing 6b show compensation, by attached drawing
6 it is found that method using the present invention reduces geometric error, and workpiece surface finds workpiece table texture and planning knife after observation compensation
Rail-engaging mark is identical, shows the constraint of the achievable workpiece texture of the present invention.In summary, a kind of five axis ball-end milling geometry of the present invention
Error compensating method, which may be implemented in, can guarantee workpiece texture features while greatly improving machining accuracy.