JPS62169210A - System for generating tool locus in nc data generating device - Google Patents

Abstract

PURPOSE:To generate tool locus data in a short time by generating divisionally the locus of the center of a tool for a work shape as free curves expressed within a prescribed precision on an offset surface which is a free curved surface. CONSTITUTION:An NC data generating device consists of a keyboard 1 of an input device, a shape surface data storage part 2, an offset surface data generating part 3, an offset surface data storage part 4, a route storage part 5, a locus generating part 6, and a locus dividing part 7, and coordinate values of the center of the tool in every divided unit work length are outputted as NC data indicating the objective locus of the center of the tool. When the locus of the tool for the work having a three-dimensional shape like a free curved surface is generated, a reference route element on the X-Y plane is divided by such length that divided elements can be projected on the offset surface while keeping a prescribed precision, and individual divided reference route elements are projected on the offset surface to obtain the curve of the locus of the center of the tool, thereby generating the locus of the tool in a short time.

Description

[Detailed Description of the Invention] (Technical Field of the Invention) The present invention is based on the NCC numerical system! 1) This invention relates to a tool trajectory 11C data generation method for machining a workpiece with a complex three-dimensional shape having a free-form surface or the like in a data creation device.

(Technical background of the invention and its problems) Conventionally, when creating Nσ data for machining a three-dimensional workpiece with a complex free-form surface, such as a mold, using an NC data creation device, this Generate an offset surface that is separated by the radius of the tool from the workpiece shape surface, which is the surface on which the L center of a pole end mill, etc. that processes the workpiece shape surface moves. Based on this offset surface data, one A method of generating coordinate values of a center locus is generally used.

FIG. 5 is a diagram for explaining such a conventional tool trajectory generation method, in which a tool center trajectory for a workpiece having a complex three-dimensional shape is generated as described below.

(2) First, the offset surface So is generated with respect to the workpiece shape surface Sv.

() Current point P on the reference route element statement eO on the X-Y plane
Offset surface S where el is projected onto the offset surface So
Find the current point PI at QJ: Next, find a point Pe2 that is a predetermined distance de# determined in advance by +iQ from the current point Pal on the reference path element statement eO, and calculate this point Pe2.
2 is projected onto the offset surface So to obtain a point P2.

0) l: Find the distance 111d between the distribution point PI and point P2, compare it with a predetermined unit machining length set in advance, and if this distance d is within the above unit machining length, use the tool to find this point P2. NC data is generated as a point indicating the center locus fLO.

If the distance fad calculated in ■ written in ■ is equal to or greater than the unit machining length above, then on the reference path JleO shown in F as in Kitakami ■, a distance ill that is a predetermined amount Δ shorter than the north distance de from the above point Pal. d e 'Recalculate the distant point Pe2° and project this point Pe2' onto the offset surface SO, which is the point P2.
Find °. Then, in the same manner as above (■), find the distance ad' between L point P1 and point P2° and compare it with the unit machining length. If this distance d' is within the unit machining length, then this point Generate NC data as a point on the tool center locus intersection 0 to obtain ρ2゛, and if this distance d'' is greater than or equal to the unit machining length, repeat the operations from ■ to ■ above until convergence, and sequentially calculate the tool center locus. The NO data is generated by finding a point that indicates .

Here, as an example of a method for creating data for a free-form surface such as the offset surface SO corresponding to the workpiece shape surface Sw as described above, we will use a conventionally used bicubic Bezier surface shown in FIG. 4(^). I will explain using

In the same figure (A), the free-form surface S has control points Qij (ij
= 0 to 3), it can be expressed by the following formula (1).

Here, U and Ma are parameters and each is 0
≦(u, ma)≦1.

- a conventional offset surface S as described above;

In the data-based tool center trajectory generation method, points PI, P2 . In order to find..., the above double 3
Equation (1) showing the next Bezier equation is
There was a problem in that the following equation had to be solved, which took a long time to process. In particular, point P2. projected onto the offset plane So as described above. P3. . . does not converge, there is a problem that the processing time becomes even longer.

(Objective of the Invention) The present invention was made in view of the above-mentioned circumstances, and an object of the present invention is to process a workpiece having a complex three-dimensional shape such as a free-form surface while maintaining a predetermined accuracy in a short time. An object of the present invention is to provide a tool path generation method in an NC data creation device.

(Summary of the Invention) The present invention relates to a tool path generation method in an NC data creation device that creates NC data for a tool path for machining a three-dimensional workpiece having a free-form surface, etc. using the NC data creation device. The tool path reference path element set on the X-Y plane of A tool trajectory is generated by projecting each path element onto an offset plane that is a predetermined distance away from the workpiece shape surface, and the generated tool trajectory is further divided into predetermined intermediate machining lengths by dividing points on the tool trajectory. The NC data for the tool trajectory is created by determining the coordinate values.

(Embodiment of the Invention) The present invention is advantageous in that when generating a tool trajectory for a workpiece having a complex three-dimensional shape such as a free-form surface, the tool position is not determined sequentially based on free-form surface data of an offset surface as in the past. Instead, the reference path element on the X-Y plane is divided into lengths that can be projected onto the offset surface while maintaining a predetermined accuracy, and each divided reference path element is projected onto the offset surface to create a tool center trajectory curve. By determining , the tool trajectory can be generated in a short time.

FIG. 4(B) shows a cubic Bezier curve showing the free curve R used in the method of the present invention. It can be expressed as

Here, w is a parameter and 0≦W≦l.

Therefore, in order to indicate the tool center locus on the offset surface SO by the cubic Bezier curve i1H, the cubic 8ezier curve R must exist on the offset surface SO without any error. 3
) formula must be satisfied.

R(w) = S (u, ma)...
... (3) However, in equation (3), R(w
) is a cubic equation with one element, and S (u, ma) is a cubic equation with two elements.

This equation (3) only holds true when either one of the parameters U and Ma is a constant, but generally the trajectory curve to be generated is at the offset surface So, and the parameters U and Ma are both not constant. Therefore, since the above equation (3) is not satisfied, the trajectory curve R cannot be defined on the offset surface SoJ:, and this trajectory curve R will cause an error with respect to the offset surface So.

Therefore, in the present invention, the trajectory curve 10 can be approximated by this cubic eezier curve R and expressed on the offset surface So, that is, so as to be within a predetermined error range set in advance. Further, the reference path element is divided into elements of a predetermined length, and each of the divided reference path elements is projected onto the offset surface So to generate a tool center trajectory curve.

FIG. 1 is a block diagram showing an example of an NC data device that implements the method of the present invention. In the same figure, a keyboard l is used to input the radius of a tool such as a pole end mill to be used when creating NC data. The shape surface data storage unit 2 is an input device, and shape surface data such as control points of a free-form surface indicating the shape surface of the workpiece to be machined is stored in advance. The offset surface data generation section 3 is the shape surface data storage section 2.
Retrieve the shape surface data stored in the keyboard 1.
The control point Q+j of the free-form surface So, which is the offset surface offset by the input tool radius, is determined, and the offset surface data storage unit 4 stores the control point Qij data of the free-form surface So, which is the water-filled offset surface. do.

The route storage unit 5 stores control point (described later) data of a free curve representing a locus of the L center seen from above the two wheels, that is, a reference route element on the XY plane. The trajectory generation unit 6 divides the reference path element into a plurality of elements according to its length and curvature so that the generated trajectory curve falls within a predetermined precision range with respect to the offset surface So, and each of the divided reference Each path element is projected onto the offset So to generate a curve along which the tool center moves, that is, a ball J4 center trajectory curve. The trajectory dividing unit 7 sequentially divides the tool center trajectory curve generated by the trajectory generating unit 6 into each set unit machining length, and calculates the coordinates of the 1-marked tool center for each divided unit machining length. The value is output as NC data indicating the desired tool center trajectory.

The operation of the tool trajectory generation method of the present invention using the NC data device having such a configuration will be described below using the flowchart of FIG. 2 with reference to FIG. 3.

First, when the tool radius of the ball end mill for machining the workpiece shape surface Sw as shown in FIG. Offset surface SO data is generated from the pre-stored shape surface data and the input tool radius and stored in the offset surface data storage section 4 (step S2). The reference path view el data stored in the unit 5 is read out, and the points Pe1f, Pe12 . P
e13. Set Pe14 and set the reference path element intersection e1 to multiple elements (three elements in Fig. 3) l ell to Me13
(step S3), where this point P
Reference path element 1el divided by e1f to Pe14
Each segmented element 1 ell~, 1e13 is projected onto the offset plane SO as will be described later.
are free curves that can be shown by the cubic Bezier curves, so each of these loci 11 to 13 is set within a predetermined accuracy range preset for the offset surface SO. , the reference path element J
The dividing point Pe1 based on the length and curvature of lel
l”Pe14 is set.

Then, the trajectory generation unit 6 projects each of the divided reference path elements fell-1e13 onto the offset plane So stored in the offset plane data storage unit 4, and generates a tool center trajectory J11 (step SO0 That is, the tool center trajectory 11 generated in the present invention is a tool center trajectory curve 11 that is a free curve divided into a plurality of parts.
~113. Therefore, the trajectory dividing section 7 divides the generated tool center trajectory 1 into every predetermined unit machining length D at points pH, P12. ...,
That is, each point pH, PI3. . . . and output it as the NO data of the tool trajectory for machining this workpiece shape surface Sw (step S5), and the step 5l-35 described above.
By repeating this, it is possible to create NO data for all tool trajectories for machining this workpiece shape surface Sw.

(Effects of the Invention) As described above, according to the tool trajectory generation force formula in the NC data creation device of the present invention, even if the workpiece shape has a complex three-dimensional shape such as a free-form surface, the tool center trajectory can be converted to a free-form surface. By dividing and generating free curves that can be expressed within a predetermined accuracy on an offset surface, tool trajectory data having a predetermined accuracy can be generated in a short time.

[Brief explanation of drawings]

Fig. m1 is a block configuration diagram showing an example of an NC data creation device that implements the method of the present invention, Fig. 2 is a flowchart for explaining the present invention in detail, Fig. 3 is a diagram for explaining the present invention in detail, 4(A) and (11) are diagrams for explaining a bicubic Bezier curve representing a free-form surface and a cubic Bezier curve representing a free curve used in the present invention, and FIG. 5 is a diagram showing a conventional tool. FIG. 3 is a diagram for explaining a trajectory generation method. l... Keyboard, 2... Shape surface data storage unit, 3
...Offset surface data generation section, 4.Offset surface data storage section, 5.Route storage section, 6.Trajectory generation section, 7.Trajectory division section, Sv.. Work shape surface ,
SO...Offset surface, no, ILL...Tool center locus, l eO, l el・-ya? l! l path element. Leather 2 Figure &/33 (,4) (E) 4th Meyu 3rd Vintage 5 Figure

Claims (1)

[Claims] When creating NC data for a tool trajectory for machining a three-dimensional workpiece having a free-form surface, etc. using an NC data creation device, the reference path element for the tool trajectory set on the X-Y plane of the workpiece is The tool path reference path element is divided into predetermined lengths according to the length and curvature, and each of the divided tool path reference path elements is placed on an offset surface a predetermined distance away from the workpiece shape surface. The NC data for the tool path is created by projecting the tool path to generate a tool path, and further dividing the generated tool path into predetermined unit machining lengths by determining the coordinate values of points on the tool path. A tool trajectory generation method in an NC data creation device characterized by the following.