CN105643362A - Five-axis machine tool measuring method based on AxiSet - Google Patents

Abstract

The invention belongs to the technical field of numerical control, and particularly provides the design of a five-axis machine tool measuring method based on AxiSet. The method includes the steps that according to kinetic models of five-axis machine tools, the influence of structural errors of the five-axis machine tools on cutter location points is determined, and a five-axis machine tool kinetic error model is set up; the error model is analyzed, so that the sources of error terms of the machine tools are determined; the characteristics of the models of the three types of machine tools are analyzed, and measuring schemes for the machine tools are determined; according to hardware equipment adopting an AxiSet<TM> Check-up assembly, a touch trigger probe is used for collecting data of a master ball; and the collected data are substituted into the error models, and after the error terms are worked out, the kinetic models of the machine tools are corrected. By means of the five-axis machine tool measuring method, machining precision of an existing numerically controlled machine tool can be improved, and measurement bases are provided for measurement of multi-axis machine tools in the future.

Description

A kind of five-axis machine tool measuring method based on AxiSet

Technical field

The invention belongs to fields of numeric control technique, specifically a kind of five-axis machine tool measuring method based on AxiSet.

Background technology

It is well known that there is lathe initial error in lathe assembling manufacturing process, and lathe is long-time, the operation of high capacity, can cause the abrasion of lathe associated components, cause also existing between actual parameter and theoretical parameter certain deviation. Specifically be reflected in kinematics is exactly that lathe also exists certain translation error and rotation error so that turning axle and main shaft deviate original position, thus carries out adding man-hour at use lathe, affects the precision of processing work.

Much equipment can be used for measuring the structure error of five-axis machine tool, such as dial indicator and test rod, two clubs etc. Dial indicator and test rod are applicable to the rotary-type lathe of cutter, are then unfavorable for control for mixed type and worktable rotary type lathe, and are manual measurements, time-consuming and efficiency is low. Two ball bar also can be used to measure machine tool error, and every two-axle interlocking during measurement, therefore needs repeatedly to link to the complete measument of gang tool. Gang tool can be measured by laser interferometer fast accurately, but price is high. And relatively cheap AxiSet^TMCheck-up assembly accurately can be measured in three-dimensional space, high efficiency and time conservation and three class five-axis machine tools are all applicable, and just gang tool is only carried out accurate status checking fast by its Measure macro program, it does not have provide error compensation function.

Summary of the invention

For above shortcomings part in prior art, the technical problem to be solved in the present invention is to provide a kind of five-axis machine tool measuring method based on AxiSet, according to take off data and 5-axis movement error model computer bed structure error, thus realize the demarcation to machine tool structure parameter.

The technical scheme that the present invention adopts for achieving the above object is a kind of five-axis machine tool measuring method based on AxiSet, and its key step has:

Set up kinematics model and the error model of five-axis machine tool, it is determined that four structure errors of five-axis machine tool, that is, two turning axle axial errors and the tool coordinate relevant to two turning axles are tied to the position offset error of turning axle;

Determine measurement scheme: by AxiSet^TMCheck-up assembly is arranged on numerically-controlled machine, surveys, by trigger-type, the centre of sphere that leader determines standard ball;

According to machine tool error model, calculate four structure errors of five-axis machine tool;

Calculate four structure errors are updated in kinematics model, kinematics model is revised, thus realize the error compensation to five-axis machine tool.

The present invention has the following advantages and useful effect:

1. practicality. Compared to multiple survey instrument, such as dial indicator and test rod are applicable to the rotary-type lathe of cutter, are then unfavorable for control for mixed type and worktable rotary type lathe, time-consuming and efficiency is low. Every two-axle interlocking when two ball bar is measured, therefore needs repeatedly to link to the complete measument of gang tool. Laser interferometer price is high. AxiSet^TMCheck-up assembly is relatively cheap, accurately can measure in three-dimensional space, and all kinds of five-axis machine tool is all applicable.

2. high efficiency. To the measurement of five-axis machine tool, generally it is divided into single error direct measurement and overall error measuring parameter method. Direct measurement directly measures the major part affecting machine tool accuracy, it is necessary to step measurement, it is desired to technical professional, and Measuring Time is longer. AxiSet instrument uses overall error measuring parameter method, it is possible to directly measure the integral position error of five-axis machine tool, thus shortens the time of acquisition observed value, it is to increase measuring speed.

3. versatility. All kinds of error models set up are had good consistence by the measuring method adopted, and by the compensation of 5-axis movement error is possible not only to the working accuracy improving existing numerically-controlled machine, and provide unified Fundamentals of Measurement for the measurement of later gang tool.

Accompanying drawing explanation

Fig. 1 is worktable rotary type machine tool structure error schematic diagram;

Fig. 2 is mixed type machine tool structure error schematic diagram;

Fig. 3 is the rotary-type structure error schematic diagram of cutter;

Fig. 4 is AxiSet measurement standard ball sphere center position schematic diagram;

Fig. 5 is circulation measurement procedure figure.

Embodiment

A kind of five-axis machine tool measuring method based on AxiSet, main process has: kinematics model and the error model setting up five-axis machine tool, determine four structure errors of five-axis machine tool, that is, two turning axle axial errors and the tool coordinate relevant to two turning axles are tied to the position offset error of turning axle; Determine measurement scheme: by AxiSet^TMCheck-up assembly is arranged on numerically-controlled machine, surveys, by trigger-type, the centre of sphere that leader determines standard ball; According to machine tool error model, calculate four structure errors of five-axis machine tool; Calculate four structure errors are updated in kinematics model, kinematics model is revised, thus realize the error compensation to five-axis machine tool.

Below in conjunction with drawings and Examples, the present invention is described in further detail.

Described set up five-axis machine tool kinematics model and error model refers to: set up corresponding kinematics model respectively according to three shown in Fig. 1, Fig. 2, Fig. 3 kind lathe. Fig. 1 describes the structure of worktable rotary type lathe coordinate system, and wherein first, second turning axle on worktable is defined as N_s1, N_s2, in X, Y, Z, any diaxon rotates respectively, and angle of rotation is ��_s1����_s2, then^wA_tCan represent and be:

^wA_t=Trans (L_ws2)Rot(N_s2,-��_s2)Trans(L_s2s1)Rot(N_s1,-��_s1)Trans(X₀,Y₀,Z₀)(1)

Workpiece coordinate system w to N wherein_s1The distance offset vector of axle represents for L_ws2, the distance offset vector between two turning axles represents for L_s2s1��

Fig. 2 describes the structure of mixed type lathe coordinate system, and wherein the first rotating shaft in work end is defined as N_s1, spindle end the 2nd turning axle is defined as N_s2, in X, Y, Z, any diaxon rotates respectively, and angle of rotation is ��_s1����_s2, then^wA_tCan represent and be:

^wA_t=Trans (L_ws1)Rot(N_s1,-��_s1)Trans(X₀,Y₀,Z₀)Rot(N_s2,��_s2)Trans(L_s2t)(2)

Workpiece coordinate system w to N wherein_s1Distance offset vector represent for L_ws1, N_s2And the distance offset vector between main shaft end points represents for L_s2t��

Fig. 3 describes the structure of the rotary-type lathe coordinate system of cutter, and first, second turning axle on spindle end is N_s1, N_s2, in X, Y, Z, any diaxon rotates respectively, and angle of rotation is ��_s1����_s2, then^wA_tCan represent and be:

^wA_t=Trans (X₀,Y₀,Z₀)Rot(N_s1,��_s1)Trans(L_s1s2)Rot(N_s2,��_s2)Trans(L_s2t)(3)

Wherein offset vector between two turning axles represents for L_s1s2, N_s2And the distance offset vector between main shaft end points represents for L_s2t��

By AxiSet^TMStandard ball and trigger-type survey head in Check-up assembly are separately fixed on worktable and main axle cutter card seat.Use trigger-type to survey head and standard ball is carried out three contact collections, the sphere center position of standard ball can be determined according to 3, sphere and the radius of a ball; Drive lathe to rotate around a certain axle, repeat said process three times. Three centre of sphere points according to collecting can determine a plane, and the method vector of this plane is the turning axle of lathe.

Described measurement scheme refers to, by AxiSet^TMStandard ball and trigger-type survey head in Check-up assembly are separately fixed on worktable and main axle cutter card seat. Owing to all survey heads before use or all have to pass through demarcation after installing new chaining pin, main shaft is surveyed head and navigates to the position that above standard ball, certain makes survey head can start to move down without collision safely or detour, approaching the centre of sphere along the straight line track parallel with axle is coordinate, obtain three positions of spherome surface, as shown in Figure 4, the sphere position that these three positions produce should form a trilateral big as far as possible, if the trilateral formed is excessively little, it is possible to calculation result can be caused accurate not. After demarcation terminates, survey head and return to standard ball overcentre, can determine that after demarcating the sphere centre coordinate of standard ball is O_b(O_b.x,O_b.y,O_b.z)��

Chaining pin is navigated to reference point r, the first turning axle angle of rotation ��_i(i=1,2,3), the 2nd rotation shaft angle �� is kept_s2Constant, chaining pin approaches the standard ball centre of sphere, and linear axes feeding is P_i(X_i,Y_i,Z_i), recording standard ball surface location is Q_i(Q_i.x,Q_i.y,Q_i.z), for CA turning axle Q_iCan represent and be:

$\left[\begin{array}{c}{Q}_{i.x}\\ Q_{i.y}\\ Q_{i.z}\end{array}\right]=\left[\begin{array}{c}{O}_{b.x}+R\cos {\mathrm{\&phi;}}_{s2}\cos {\mathrm{\&alpha;}}_i\\ O_{b.y}+R\cos {\mathrm{\&phi;}}_{s2}\sin {\mathrm{\&alpha;}}_i\\ O_{b.z}+R\sin {\mathrm{\&phi;}}_{s2}\end{array}\right]$

Bring machine tool structure error model into,

$\left[\begin{array}{c}Q\\ 1\end{array}\right]=\mathrm{Trans}(X_i,Y_i,Z_i)\mathrm{Rot}(N_{s1},{\mathrm{\&alpha;}}_i)\mathrm{Trans}\left(L_{s1s2}\right)\mathrm{Rot}(N_{s2},{\mathrm{\&phi;}}_{s2})\mathrm{Trans}\left(L_{s2t}\right)\left[\begin{array}{c}r\\ 1\end{array}\right],i=\mathrm{1,2,3}---\left(4\right)$

Note $\mathrm{Trans}{(X_i,Y_i,Z_i)}^{-1}\left[\begin{array}{c}Q\\ 1\end{array}\right]=\left[\begin{array}{c}{\mathrm{\&mu;}}_i\\ 1\end{array}\right],$ Trans(L_s1s2)Rot(N_s2,��_s2)Trans(L_s2tAlthough) it is unknown quantity but value is fixing, therefore can regard �� as_iOnly and N_s1Relevant, then ��₁����₂����₃It is positioned at around N_s1Rotate circumferentially, taken advantage of by vectorial difference and can obtain the axial N of the first turning axle_s1��

Chaining pin is navigated to reference point r, keeps the first rotation shaft angle ��_s1Constant, the 2nd turning axle angle of rotation ��_i(i=1,2,3), chaining pin approaches the standard ball centre of sphere, and linear axes feeding is P_i'(X_i,Y_i,Z_i), recording standard ball surface location is Q_i'(Q'_i.x,Q'_i.y,Q'_i.z), for CA turning axle Q_i' can represent and it is:

$\left[\begin{array}{c}{Q^{\&prime;}}_{i.x}\\ {Q^{\&prime;}}_{i.y}\\ {Q^{\&prime;}}_{i.z}\end{array}\right]=\left[\begin{array}{c}{O}_{b.x}+R\cos {\mathrm{\&phi;}}_{s1}\cos {\mathrm{\&alpha;}}_i\\ O_{b.y}+R\cos {\mathrm{\&phi;}}_{s1}\sin {\mathrm{\&beta;}}_i\\ O_{b.z}+R\sin {\mathrm{\&phi;}}_{s1}\end{array}\right]$

Bring machine tool structure error model into,

$\left[\begin{array}{c}{Q}_j^{\&prime;}\\ 1\end{array}\right]=\mathrm{Trans}({X_i}^{\&prime;},{Y_i}^{\&prime;},{Z_i}^{\&prime;})\mathrm{Rot}(N_{s1},{\mathrm{\&phi;}}_{s1})\mathrm{Trans}\left(L_{s1s2}\right)\mathrm{Rot}(N_{s2},{\mathrm{\&beta;}}_j)\mathrm{Trans}\left(L_{s2t}\right)\left[\begin{array}{c}r\\ 1\end{array}\right],i=\mathrm{1,2,3}---\left(5\right)$

Note $\mathrm{Trans}{({X_i}^{\&prime;},{Y_i}^{\&prime;},{Z_i}^{\&prime;})}^{-1}\left[\begin{array}{c}{Q}_j^{\&prime;}\\ 1\end{array}\right]=\left[\begin{array}{c}{v}_i\\ 1\end{array}\right],$ Analyze according to formula (2), v₁,v₂,v₃It is positioned at around N_s2Rotate circumferentially, taken advantage of by vectorial difference and can obtain the axial N of the 2nd turning axle_s2��

Any two group of five axle feeding data getting measurement every time are brought in formula (1), obtain and L_s1s2��L_s2tFirst relevant expression formula:

(R₁-R₂)^-1(P₂-P₁)=R_s2r+R_s2L_s2t+L_s1s2(6)

If Q=Q', get and measure N_s1One group of data with measure N_s2One group of data bring in formula (1), obtain and L_s1s2��L_s2tThe 2nd relevant expression formula:

(R₁+R_s1)^-1(P₁'+P₁)=R₁'r+R₁'L_s2t+L_s1s2(7)

Wherein R₁,R₂With ��₁,��₂Relevant, R_s2WithRelevant, P₁,P₂Relevant with linear axis feeding, R_s1WithRelevant, R₁' and ��₁Relevant, P₁' relevant with linear axis feeding. Connection vertical (6), (7) solving equations can try to achieve L_s2t,L_s1s2. The lathe of other structure types can also be calculated by same mode.

As shown in Figure 5, if process of measurement can read the operating scheme generating and approaching measurement point, it may be achieved automatic measurement function is integrated in process of measurement. Bigger measuring error may be there is in reality is measured, use tolerance confirmatory measurement result whether in a tolerance interval, after one-shot measurement completes, calculate the value of each error term of lathe, if error e rr is not checked by tolerance, then think that this measuring error is bigger, it is not counted in result, again measure, when invalid pendulous frequency e exceedes set-point E, stop measuring and report to the police. In order to increase precision, repetitive measurement capable of circulation, calculation result is averaged. The general sub-routine that can be used as and solve particular measurement task is measured in circulation, is adjusted according to particular problem by parameter.

Claims (4)

1. the five-axis machine tool measuring method based on AxiSet, it is characterised in that, comprise the following steps:

Set up kinematics model and the error model of five-axis machine tool, it is determined that four structure errors of five-axis machine tool, that is, two turning axle axial errors and the tool coordinate relevant to two turning axles are tied to the position offset error of turning axle;

Determine to measure: by AxiSet^TMCheck-up assembly is arranged on numerically-controlled machine, surveys, by trigger-type, the centre of sphere that leader determines standard ball;

According to machine tool error model, calculate four structure errors of five-axis machine tool;

Calculate four structure errors are updated in kinematics model, kinematics model is revised, thus realize the error compensation to five-axis machine tool.

2. a kind of five-axis machine tool measuring method based on AxiSet according to claim 1, it is characterised in that, when five-axis machine tool is worktable rotary type lathe, described kinematics model is:

^wA_t=Trans (L_ws2)Rot(N_s2,-��_s2)Trans(L_s2s1)Rot(N_s1,-��_s1)Trans(X₀,Y₀,Z₀)(1)

Wherein,^wA_tRepresent the module and carriage transformation matrix of cutter to workpiece, L_ws2Represent that workpiece coordinate is tied to N_s2Wheelbase from offset vector, L_s2s1Represent the distance offset vector between two turning axles, Rot (N_s2,-��_s2) represent that worktable is around N_s2Axle rotates ��_s2The homogeneous matrix of angle, Rot (N_s1,-��_s1) represent that worktable is around N_s1Axle rotates ��_s1The homogeneous matrix of angle, Trans (X₀,Y₀,Z₀) represent that translating vector to workpiece coordinate system is L=[X₀,Y₀,Z₀] ' homogeneous matrix;

When five-axis machine tool is mixed type lathe, described kinematics model is:

^wA_t=Trans (L_ws1)Rot(N_s1,-��_s1)Trans(X₀,Y₀,Z₀)Rot(N_s2,��_s2)Trans(L_s2t)(2)

Wherein, implication representated by each letter is identical with formula (1);

When five-axis machine tool is the rotary-type lathe of cutter, described kinematics model is:

^wA_t=Trans (X₀,Y₀,Z₀)Rot(N_s1,��_s1)Trans(L_s1s2)Rot(N_s2,��_s2)Trans(L_s2t)(3)

Wherein, implication representated by each letter is identical with formula (1).

3. a kind of five-axis machine tool measuring method based on AxiSet according to claim 1, it is characterised in that, described determine that measuring method is:

By AxiSet^TMStandard ball and trigger-type survey head in Check-up assembly are separately fixed on worktable and main axle cutter card seat;

Use trigger-type to survey head and standard ball is carried out at least three contact collections, determine the sphere center position of standard ball according to 3, sphere and the radius of a ball;

Drive lathe to rotate around a certain axle, repeat said process at least three times, obtain three sphere center positions;

Determine the plane at standard ball centre of sphere place according to three sphere center positions collected, the method vector of this plane is the turning axle of lathe.

4. a kind of five-axis machine tool measuring method based on AxiSet according to claim 1, it is characterised in that, the method for four structure errors of described calculating five-axis machine tool is:

$\left[\begin{array}{c}Q\\ 1\end{array}\right]=\mathrm{Trans}(X_i,Y_i,Z_i)\mathrm{Rot}(N_{s1},{\mathrm{\&alpha;}}_i)\mathrm{Trans}\left(L_{\mathrm{sls}2}\right)\mathrm{Rot}(N_{s2},{\mathrm{\&phi;}}_{s2})\mathrm{Trans}\left(L_{s2t}\right)\left[\begin{array}{c}r\\ 1\end{array}\right],i=\mathrm{1,2,3}---\left(4\right)$

Wherein in the process of single-shaft-rotation, Trans (X_i,Y_i,Z_i), $\mathrm{Trans}\left(L_{\mathrm{sls}2}\right)\mathrm{Rot}(N_{s2},{\mathrm{\&phi;}}_{s2})\mathrm{Trans}\left(L_{s2t}\right)\left[\begin{array}{c}r\\ 1\end{array}\right],$ All immobilize, calculate N by vector multiplication cross_s1; With reason, calculate N_s2; When (4) formula is got i=1 and i=2, two formulas are subtracted each other,

(R₁+R₂)^-1(P₁+P₂)=R_s2r+R_s2L_s2t+L_s1s2(6)

(R₁+R_s1)^-1(P₁'+P₁)=R₁'r+R₁'L_s2t+L_s1s2(7)

Two distance offset vectors are calculated according to formula (6) (7).