CN103412514B - Paths planning method in a kind of multi-shaft interlocked belt sanding processing - Google Patents

Abstract

The invention discloses the paths planning method of a kind of belt sanding processing, for realizing the tool-path planning in processed curved surface, it is characterized in that, the method specifically comprises: S1 extracts the parameter line such as grade of processed curved surface; S2 is in parameter field, and plan the migration path between adjacent parameter line such as grade, each parameter line such as grade and described migration path form the initial Path in parameter field; The discrete point cooked up in parameter field by discrete for the initial tool track in parameter field, and according to the point correspondence of parameter field and curved surface to be processed, be mapped on curved surface to be processed, obtain cutter-contact point by S3; S4 calculates cutter location corresponding to each cutter-contact point, generating tool axis vector and contact wheel axis vector, obtains the cutting location data of belt sanding processing, can realize tool-path planning.Method of the present invention can effectively reduce the mistake caused due to velocity jump between adjacent parameter line and cut, and obtains good speed change curves, improves complex-curved profile grinding quality.

Description

Paths planning method in a kind of multi-shaft interlocked belt sanding processing

Technical field

The invention belongs to CNC processing technology field, be specifically related to the paths planning method of a kind of belt sanding processing, can be used for processing the rubbing down of complex profile in multi-axis linkage numerical control belt sanding lathe.

Background technology

The complex thin-wall class part profile of such as blade and so on is Space Free-Form Surface, and Curvature varying is large, easily deforms, cause grinding allowance maldistribution after NC milling.Usually grinding is used in the industry to ensure the homogeneity of process redundancy.But, along with the continuous increase of blade dimensions and volume, employing hand polishing is more and more difficult, inefficiency, crudy is difficult to ensure---traditional hand polishing has become the bottleneck of restriction blade Industry Quick Development gradually, and active demand adopts multi-axis linkage numerical control rubbing down to solve blade profile finishing problem.Blade belt sanding programming refers to according to machining area characteristic, merges blade belt sanding process planning, then generates grinding track and export the cutter location file controlling lathe attitude.Usually in multiaxis abrasive belt grinding machine, claim abrasive belt wheel to be Z-direction away from the direction of workpiece, the turning axle corresponding with Z axis is C axle.Belt sanding technological requirement controls the direction of abrasive band contact wheel axis along with surface to be machined Curvature varying, and ensures that the normal direction of the C axle centre of gyration and machined surface overlaps.Therefore, blade digital control belt sanding must adopt at least six-coordinate linkage mode, just can reach good ground effect.

In existing six-axis linkage belt sanding machining software, the planning of cutter path is the planning mode of the parameter lines such as employing mostly: in the parameter field that curved surface to be processed is corresponding, the U parameter lines such as selection or etc. V parameter line mode cook up a series of initial point, and adjacent two parameter line starting points are connected with straight line, the cutter path of a continuous print parameter field can be obtained thus.Parameter field cutter path is projected to the model space and just obtain actual machining locus.This method simple practical based on waiting parameter line to generate cutter path, is widely used in various NC Machining Program software.

But there is a shortcoming in this path, namely during adjacent two parameter line transition, starting point from the end point of Article 1 parameter line to Article 2 parameter line, speed of feed direction has twice sudden change, digital control system has to reduce speed of feed herein, makes the duration of contact of abrasive band and profile elongated.During belt sanding, stock removal was directly proportional to the duration of contact of abrasive band and profile, and under same machining condition, duration of contact is longer, and stock removal is larger.Therefore, the method for this path planning, the stock removal being easily greater than other positions when transition due to stock removal occurred to cut, and occurred to cut and can affect surface quality, damages, affect the performance of blade to blade profile streamline.

Summary of the invention

The present invention proposes a kind of multi-axis linkage numerical control belt sanding paths planning method, object is the parameter field cutter path by cooking up " Z " font, again track is projected to the model space, obtain final process tool track, thus effectively reduce the mistake caused due to velocity jump between adjacent parameter line and cut, obtain good speed change curves, to improve complex-curved profile grinding quality.

For achieving the above object, concrete technical scheme proposed by the invention is as follows:

A kind of multi-shaft interlocked belt sanding method for planning track, comprises following calculation procedure:

(1) that extracts processed curved surface waits parameter line

Some according to theory of graphics acquisition processed curved surface meeting technological requirement are waited parameter line, obtain the starting point of every bar parameter line and (U, V) coordinate of end point.

(2) migration path is planned

Between two adjacent parameter lines, according to the end point of Article 1 parameter line and the (U of Article 2 parameter line starting point, V) coordinate draws a straight line in parameter field, then obtain discrete cutter-contact point by machine direction order interpolation on this line according to processing step pitch, namely obtain the excess path between two adjacent parameter lines.Between every two parameter lines, insert the excess path planned, obtain cutter path complete in parameter field.

(3) the initial cutter-contact point in parameter field is projected on curved surface to be processed

By discrete for the cutter path in parameter field.According to the point correspondence of parameter field and curved surface to be processed, the initial cutter-contact point cooked up is mapped on curved surface to be processed, obtains cutter-contact point in parameter field.

(4) cutter location corresponding to each cutter-contact point, generating tool axis vector and contact wheel axis vector is calculated

According to the process requirements of belt sanding, calculate cutter location corresponding to each cutter-contact point, generating tool axis vector and contact wheel axis vector, obtain all cutting location data of multi-axis linkage numerical control belt sanding.

The method for planning track of belt sanding of the present invention, in the path planning stage, build the initial path of " Z " font, and path is discrete after project on curved surface to be processed, again according to the size of curved surface characteristic and contact wheel, calculate the cutter location, normal vector and the contact wheel axis vector that control belt sanding.

The present invention adopts the initial path of " Z " font, and only needs velocity jump changes the track of direction of feed, thus the mistake reducing to cause because speed of feed is uneven is cut, and improves blade surface grinding quality.In addition, the method can be integrated in the path planning of multi-axis linkage numerical control belt sanding automatic programming system easily, and computing velocity is fast, and algorithmic stability is reliable, can be used for six-axis linked numerical control belt sanding lathe, reduce the mistake caused due to velocity jump in numerical control belt sanding process and cut.

Accompanying drawing explanation

Fig. 1 is the initial tool path schematic diagram planned in parameter field when carrying out path planning of the prior art;

Fig. 2 is the initial tool path schematic diagram planned in parameter field when adopting method of the present invention to carry out path planning.

Embodiment

In order to make object of the present invention, technical scheme and advantage clearly understand, below in conjunction with drawings and Examples, the present invention is further elaborated.Should be appreciated that specific embodiment described herein only in order to explain the present invention, be not intended to limit the present invention.

For six-axis linked numerical control belt sanding, the present invention is introduced in the present embodiment, be used for six-axis linked numerical control belt sanding lathe by the method, but the present invention is not limited to lathe or the structure of the above-mentioned type.

The paths planning method of the belt sanding processing in the present embodiment specifically comprises the following steps.

(1) that extracts processing curve waits parameter line

The parameter line such as grade extracting processing curve belongs to method ripe in the industry, such as, can obtain the parameter line such as grade in processed curved surface according to theory of graphics.

In the present embodiment, with U, V parameter field scope corresponding to processing curve all for (0,1) be example, the starting point of the parameter line such as U such as grade of U=u is (u, 0), end point is (u, 1), till the starting point of the parameter line such as V such as grade of V=v be (0, v), end point be (1, v).If initial manufacture direction be U to, need on V direction, to extract the parameter lines such as N bar as cutter path according to technique, the V value of i-th parameter line is i/ (N-1) (i=0,1,2 ... N-1).If initial manufacture direction be V to, then plan stage property path in the u-direction, the U value of i-th parameter line is i/ (N-1) (i=0,1,2 ... N-1).

(2) path planning in parameter field

As shown in Figure 1, when general grinding or Milling Process trajectory planning, cutter path can be planned as a series of parallel lines, and the end of every two adjacent flat lines to be connected to come transition, i.e. Zigzag tool path pattern with straight line.But the method weak point is: from a parameter line to another parameter line time, there is twice sudden change in speed of feed direction.This can cause actual feed to be considerably slower than design feeding herein, can cause and cut.

The present embodiment is path optimizing on the basis of Zigzag in the following way: as shown in Figure 2, if when machine direction is U, in parameter field with straight line as migration path connect (1, i) and (0, i+1) (i=0,1,2 ... N-2) forming complete initial tool track, so just achieve the edge at machining area, only there is the sudden change of primary feed direction in actual machining locus, optimize local velocity's distribution, decrease the local over-cutting in actual processing.

(3) discreet paths be mapped to the model space

Parameter line and transition line by maximum step-length requirement and direction of feed order discrete, obtain cutter-contact point at point corresponding to parameter space.

Sequential Mapping will be pressed to the model space in parameter field, obtain the cutter-contact point that the model space is discrete.Mapping process is the mode of this area maturation, and general graphics basis can realize.

(4) generating tool axis vector and contact wheel axis vector is obtained

The cutting location data such as cutter location, generating tool axis vector and contact wheel axis vector can be calculated according to above-mentioned cutter-contact point, thus obtain Path.

Calculate cutting location data according to cutter-contact point and have ripe algorithm in the art, specifically describe as follows in the present embodiment:

First, cutter location coordinate is calculated according to cutter-contact point.Movement locus in the processing of numerical control abrasive band is actually central track of cutter curve, therefore must calculate the center cutter coordinate of blade processing point.The cutter heart point coordinate of emery wheel (or contact wheel) is that the radius r that contact point is taken turns along normal bias tool contact obtains.If P point is point to be processed, coordinate is P (Px, Py, Pz), O point is the central point of cutter, and coordinate is set to O (Ox, Oy, Oz), and N is the unit normal vector N (Ni, Nj, Nk) of this point, then the coordinate of O point is:

$\left\{\begin{array}{c}\mathrm{Ox}=\mathrm{Px}+r\·\mathrm{Ni}\\ \mathrm{Oy}=\mathrm{Py}+r\·\mathrm{Nj}\\ \mathrm{Oz}=\mathrm{Pz}+r\·\mathrm{Nk}\end{array}\right.$

For grinding wheel spindle line vector, by infinitesimal geometry knowledge, in order to make abrasive band and machined surface the highest in the degree of closeness at contact point place, interfere minimum, its generating tool axis vector should be positioned at the minimum curvature direction of contact point place curved surface.P point is contact point (point to be processed), and O point is center cutter, O ₁o ₂for contact wheel axis, O ₁o ₂parallel with the minimum principal direction of curvature of this point.

The parametric equation of blade profile is: Σ: r=r (u, v), (u, v) ∈ R

The principal curvatures of processing curve at its contact point place can be tried to achieve by following formula:

K ²(EG-F ²)-K(LG-2MF+NE)+(LN-N ²)=0

K is separated for two of K in formula ₁and K ₂respectively two principals direction of curvature of corresponding curved surface, E, F, G, L, M, N are curved surface at the first kind of contact point and Equations of The Second Kind fundamental quantity:

$\left\{\begin{array}{c}E=r_u^2\\ F=r_u{r}_v\\ G=r_v^2\\ L=n\·r_{\mathrm{uu}}\\ M=n\·r_{\mathrm{uv}}\\ N=n\·r_{\mathrm{vv}}\end{array}\right.$

In above formula, n is the unit normal vector at contact point place.

The principal direction of processing curve at contact point place is:

$\left\{\begin{array}{c}{d}_{\mathrm{ui}}=N-K_{i}G\\ d_{\mathrm{vi}}=K_{i}F-M\end{array}\right.,i=\mathrm{1,2}$

According to surface equation, calculate unit normal vector n, the single order local derviation r at cutter location place _uand r _v, second order local derviation r _uuand r _vv, principal curvatures K ₁and K ₂, substitute into the first kind and Equations of The Second Kind fundamental quantity formula, can E, F, G, L, N be obtained.Also must ask for the value of M to calculate principal direction, the relation according to quadratic equation root and coefficient has:

$K_1+K_2=\frac{\mathrm{LG}-2\mathrm{MF}+\mathrm{NE}}{\mathrm{EG}-F^2}$

Only have parameter M unknown in above formula, after trying to achieve M, principal direction computing formula can determine two principal directions, and K value determined du, dv of taking absolute value little are as cutter axis orientation.When du, dv are zero entirely, this contact point is the omphalion on processing curve, and cutter axis orientation can choose the r of curved surface _vdirection.

Complete above step can obtain complete planning after cutter location file.The NC code for processing can be obtained after the corresponding postpositive disposal of lathe.

Those skilled in the art will readily understand; the foregoing is only preferred embodiment of the present invention; not in order to limit the present invention, all any amendments done within the spirit and principles in the present invention, equivalent replacement and improvement etc., all should be included within protection scope of the present invention.

Claims (3)

1. a tool-path planning method for belt sanding processing, for realizing the tool-path planning in processed curved surface, it is characterized in that, the method specifically comprises:

S1: that extracts processed curved surface waits parameter line;

S2: in parameter field, plan the adjacent migration path waited between parameter line, each parameter line such as grade and described migration path form the initial Path in parameter field, wherein, the starting point coordinate of the end point of front first-class parameter line and adjacent rear first-class parameter line is drawn a straight line in parameter field, any two adjacent migration paths such as parameter line such as grade can be obtained;

S3: the initial tool track in parameter field is carried out discrete according to maximum step-length and direction of feed order, and according to the point correspondence of parameter field and curved surface to be processed, the discrete point cooked up is mapped on curved surface to be processed, acquisition cutter-contact point in parameter field;

S4: calculate cutter location corresponding to each cutter-contact point, generating tool axis vector and contact wheel axis vector, obtains the cutting location data of belt sanding processing, can realize tool-path planning.

2. the tool-path planning method of a kind of belt sanding processing according to claim 1, is characterized in that, the discrete of described initial tool track carries out according to maximum step-length and direction of feed order.

3. an application rights requires the aerial blade part that the method described in 1 or 2 obtains.