JP2007200121A - Tool path generation method and tool path generation program - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To generate a tool path without confirming overshaven parts or undershaven parts by an NC simulator. <P>SOLUTION: In a tool path generation method in a CAM device for generating data of a tool path along which a tool should move during curved surface cutting, the CAM device calculates a first curve P<SP>A</SP>(t) and a second curve P(t) which are curves resulting from offsetting shape data of an external shape of an object to be worked by different offset amounts, calculates a first point P<SP>A</SP><SB>0</SB>being an arbitrary point on the first curve P<SP>A</SP>(t), calculates a line 502 tangent to the second curve P(t) from the first point P<SP>A</SP><SB>0</SB>, calculates a second point P<SP>A</SP><SB>1</SB>where the line 502 intersects with the first curve P<SP>A</SP>(t), and calculates the line 502 connecting the first point P<SP>A</SP><SB>0</SB>and the second point P<SP>A</SP><SB>1</SB>, whereby the tool path is generated. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to a CAM (Computer Aided Manufacturing) device for creating data for a numerical control (NC) device, and in particular, a technique for creating a tool path for moving a tool along a target path. About.

Conventionally, NC machining is generally performed by the following procedure.
First, the CAM device reads machining shape data created by CAD (Computer Aided Design). Then, the CAM device designates the machining target portion for the machining shape data, sets the parameters such as the tool, the uncut amount, and the machining speed, and then creates a tool path based on these design conditions. Next, the CAM device converts this tool path into NC data in a format executable by the numerical control device. Subsequently, after the numerical control device reads this NC data and converts it into a command to the table and the rotation axis of the processing machine, the curved surface processing device operates the table and the rotation axis of the processing machine according to this command, NC machining is performed.

  Here, the tool path represents the moving position of the tool, and in the case of a processing machine that moves only the table, it is expressed by broken line data that connects the rotation center position of the tool tip in order and rotates in addition to the table. In the case of a processing machine in which the shaft rotates, the rotation center position of the tool tip and the direction of the tool axis are represented by broken line data in order.

In addition, since the tool path is reference data for creating NC data for operating the table and the rotation axis of the processing machine, the shape after processing becomes the target dimension without considering the relationship with the shape representing the workpiece. In contrast, it becomes smaller (shaved) or larger (uncut).
Uncut material can be dealt with by cutting or polishing in the next process, but it is difficult to deal with shaving in the next process, so it is necessary to remove it with great care.

FIGS. 11A and 11B are diagrams for explaining cutting and uncut portions when a ball end mill is used for a tool. FIG. 11A shows a state in which the processing surface is in a convex state, and FIG. Indicates the state.
First, a procedure for creating a tool path will be described with reference to FIG.
(1) First, the CAM device calculates a point 1102a and a point 1103a on the surface (processed surface) 1101a of the workpiece. Points 1102a and 1103a are points where the tool contacts the workpiece, and are referred to as tool contact points.
(2) Next, the CAM device calculates the normal line 1104a and the normal line 1105a at the tool contact point 1102a and the tool contact point 1103a, and the point 1107a and the point offset by the radius of the tool (ball end mill) 1106a in the normal direction 1108a is made.
Here, the point 1107a and the point 1108a are the rotation center of the tool blade edge and are referred to as the tool center point.
In actual machining, the tool 1106a moves along a straight line 1109a connecting the tool center point 1107a and the tool center point 1108a created in the procedures (1) and (2). In this case, the straight line 1109a becomes the tool path.

  As shown in FIG. 11B, even when the machining surface 1101b is concave, the tool path 1109b is calculated in the same manner as in FIG.

Therefore, the part that scrapes off the workpiece when the tools 1106a and 1106b move becomes an envelope surface when the tools 1106a and 1106b move along the straight lines 1109a and 1109b. In FIG. 11A, the envelope surface is illustrated by a straight line 1110a representing the contour of the envelope surface. In addition, as shown in FIG. 11B, the envelope surface when the machining surface 1101b is concave represents the outline of the envelope surface by a straight line 1110b.
As shown in FIGS. 11A and 11B, when the machining surface is convex, the envelope surface 1110a, that is, the tool path 1109a is a straight line with respect to the machining surface 1101a, so that cutting occurs and the machining surface becomes concave. In this case, since the envelope surface 1110b, that is, the tool path 1109b is a straight line with respect to the processing surface 1101b, uncut portions are generated.
The amount of cutting or uncut material varies depending on the radius of the tools 1106a and 1106b and the size of the unevenness between the tool contact points 1102a, 1103a, 1102b, and 1103b. In cutting, the only way to change the radius of the tools 1106a and 1106b is to replace the tools 1106a and 1106b, but even if an automatic tool changer is prepared, it takes time to change the tool, so it is efficient to change the tool frequently. Not right.

  As a technique for reducing the amount of such cutting or uncut material, a method of coping with a method of reducing the distance between two tool contact points according to the uneven state of the processed surface has been proposed (see, for example, Patent Document 1). .

FIGS. 12A and 12B are diagrams for explaining a tool path when a conventional machining surface is offset. FIG. 12A shows a case where the machining surface is in a convex state, and FIG. 12B shows a case where the machining surface is in a concave state. Indicates.
In addition, since the cutting position and the cutting amount change depending on the size of the unevenness between the tool contact points, the NC data inspection system (NC simulator) is used to deal with such changes. Confirm. As a result of confirmation, if cutting occurs, as shown in FIG. 12, the machining surface is offset by the cutting amount, and tool paths 1202a and 1202b are created again from the offset shapes 1201a and 1201b to which this offset is applied. Then, by repeating the process of confirming the cutting again with the NC simulator, the tool path without the cutting was completed. Note that the offset amount at the time of confirmation of cutting is often obtained empirically.
Further, the check of uncut material is performed by the same method as the check of cutting.
Edited by Nikkei CG, Basic knowledge of CAD, Nikkei Business Publications, August 1994, p. 271-275, FIG. 7.26-7.31 JP-A-10-69311 (pages 2 to 3, FIG. 24)

By the way, as described in Patent Document 1, by reducing the distance between the tool contact points, the amount of cutting and the amount of uncut material can be reduced, but the amount of cutting and uncut material is not eliminated, This does not mean that the offset process and the confirmation of uncut or uncut material by the NC simulator will be eliminated.
Furthermore, if the distance between the tool contact points is reduced, the number of tool center points used in the tool path increases, so the number of tool acceleration / deceleration points during tool movement increases, resulting in an increase in machining time. is there. In addition, since the amount of NC data increases, the time for transferring NC data to the numerical controller increases, and as a result, the time during which the processing machine actually cuts is reduced.

  In addition, when the tool center point increases by narrowing the interval between the tool contact points, the NC simulation time, shape offset time, and tool path creation time in the NC simulator increase, so that cutting or uncut material is minimized. The time until is increased. As a result, since the time until NC data creation increases, problems such as an increase in waiting time until operation of the machining apparatus and an increase in the work time of the NC data creation worker occur.

  In view of the above-described problems, an object of the present invention is to create a tool path without confirming cutting or uncut material by an NC simulator.

  In order to solve the above-mentioned problems, the present invention provides a tool path creation method in a CAM device that creates tool path data that is a path along which a tool moves during curved surface cutting. The shape data of the outer shape of the object is read from the storage device in which the shape data is stored, and a curve along the shape specified by the shape data is calculated based on the read shape data, and the curve is different. A first curve and a second curve that are offset by an offset amount are calculated, a first point that is an arbitrary point on the first curve is calculated, and the second curve is calculated from the first point. By calculating a straight line tangent to the first line, calculating a second point where the straight line intersects the first curve, and calculating a straight line connecting the first point and the second point. , Create the tool path I am characterized in.

  According to the present invention, it is possible to create a tool path without confirming the cutting or the uncut portion by the NC simulator.

  Next, embodiments of the present invention will be described in detail with reference to the drawings as appropriate.

[Configuration of CAM system]
FIG. 1 is a block diagram illustrating a configuration example of a CAM system according to the present embodiment.
The CAM system in the present embodiment creates and creates a CAD device 2 that creates curved surface data that is CAD data, a storage device 3 that stores curved surface data, and a path (tool path) through which the tool moves based on the curved surface data. The CAM device 1 for converting the tool path into NC data, the curved surface machining device 5 for performing curved surface machining such as cutting, etc. are composed of a numerical control device 4 and a curved surface machining device 5 for numerical control according to the NC data.

The CAD device 2 operates on a host computer (for example, a PC (Personal Computer)), creates curved surface data that is finished shape data (CAD data), and stores the curved surface data in the storage device 3.
In the present embodiment, curved surface data and offset curved surface data described later are referred to as “curved surface”. Similarly, curve data calculated based on a curved surface, offset curve data described later, and the like are referred to as “curve”.

  In the numerical control device 4, the coordinate system for determining the tool position of the curved surface processing device 5 has at least three basic axes of X, Y, and Z that are orthogonal to each other.

[Configuration of CAM device 1]
The CAM device 1 includes a processing unit 11 that processes data.
The processing unit 11 includes a curved surface data reading unit 112 that reads curved surface data from the storage device 3, a machining part setting unit 113 that sets a machining part in curved surface data, a tool type setting unit 114 that selects and sets a tool type, a tool A route pattern setting unit 115 that sets a route pattern that is a route pattern, a specification such as the number of rotations of a tool used for cutting, a tool moving speed, and a specification setting / remaining amount setting unit 116 that sets an uncut amount. The tool path creation unit 111 that creates a tool path based on the setting conditions set by each setting unit and the curved surface data. When correction is necessary for the created tool path, path correction processing is performed on the tool path. A path correction unit 117 to perform, and an NC data conversion unit 118 to convert the created tool path or the tool path subjected to the path correction process into NC data. It is.

[Configuration of tool path creation unit]
Further, the tool path creation unit 111 calculates a curvature direction vector representing the magnitude and direction of the curvature of the curve, a curve calculation unit 1111 for calculating a curve on the curved surface, and the unevenness of the curve is inverted based on the curvature direction vector. Curvature reversal search / determination unit 1112 that performs a search / calculation of a part (unevenness inversion part) and further determines whether the corresponding curve is convex or concave based on the positional relationship between the curve and the curved surface, a part where the curvature is reversed Is determined to be present, the curve dividing unit 1113 that divides the curve at the concave / convex reversing part, which is the place where the curvature is reversed, in the tool setting unit, whether or not the set tool is a flat end mill, etc. A tool determining unit 1114 for determining, a margin offset unit 1115 for creating a curve obtained by offsetting the curve in the normal direction of the curved surface and offset by a remaining amount (reservoir), and between the curve and the offset curve A polygonal line creation unit 1116 that creates a polygonal line by searching for a vertex of a polygonal line that becomes a tool path, a path interpolation unit 1117 that interpolates a broken line break generated when the polygonal line created by the polygonal line creation unit 1116 is offset by the tool radius, and a curve If the curve is concave, the end mill contact search unit 1118 searches for a contact point that is a position where the end mill touches the curve at two points. If the curve is a concave shape, the curve is offset by the tool radius of the end mill. And an offset unit 1119.

  Each unit in the CAM device 1 is stored in, for example, an HDD or a ROM in a computer having a central processing unit (CPU), a random access memory (RAM), a read only memory (ROM), a hard disk drive (HDD), and an input / output interface. The program is developed in the RAM, and the program executed in the RAM is executed by the CPU.

(Overall processing)
Next, the flow of NC data creation processing in the CAM system will be described with reference to FIG.
FIG. 2 is a flowchart showing a flow of processing for creating NC data in the CAM system according to the present embodiment.
First, the CAD device 2 performs curved surface data creation processing for creating curved surface data that is CAD data necessary for curved surface processing (S101). Then, the CAD device 2 sends the created curved surface data to the storage device 3, and the storage device 3 stores the curved surface data to perform curved surface data storage processing (S102).
The curved surface data includes, for example, a B-spline curved surface format including a rank, a knot number, a control point number, a knot sequence, and a control point sequence. In the B-spline curved surface format, since there is a relationship of the number of control points = the number of knots−the rank between the number of control points and the number of knots, either the number of control points or the number of knots may be stored in the curved surface data. In this specification, the curved surface data is described centering on the B-spline curved surface format, but may be in other formats such as a spherical surface or a cylindrical surface.

Next, the curved surface data reading unit 112 of the CAM device 1 performs curved surface data reading processing for reading curved surface data from the storage device 3 (S103).
Then, a processing part setting process is performed in which the processing part setting unit 113 sets a processing part to be processed by the curved surface processing apparatus 5 to curved surface data via an input unit (not shown) (S104). Subsequently, a tool type selection / setting process is performed in which the tool type setting unit 114 selects / sets the type of tool used for machining (S105), and the path pattern setting unit 115 moves the tool in one direction / reciprocation. A path pattern setting process for setting a path pattern, which is a tool path pattern, is performed by performing selection / setting such as moving with / moving in a spiral (S106).
Next, the specification setting / uncut amount setting unit 116 maximizes the specifications such as the rotational speed and tool moving speed of the tool used for cutting, and the uncut amount on the processing surface, that is, the processing portion and the tool path. A specification setting / remaining amount setting process for setting an unremoved amount at a point where the difference between the two values becomes the maximum is performed (S107). Here, the uncut amount may be set separately depending on whether the processed surface is concave or convex.

The tool path creation unit 111 acquires the setting conditions set in step S104, step S105, step S106, and step S107, acquires curved surface data from the curved surface data reading unit 112 according to the acquired setting conditions, and acquires the curved surface data. The tool path creation process for creating a tool path is performed in accordance with the set tool type, path pattern, and uncut remaining amount (S108). In addition to the setting conditions described above, the tool path is created using the tool rotation speed and the tool movement speed specified by the specification setting / remaining amount setting unit 116.
Next, when correction is necessary for the created tool path, the path correction unit 117 performs path correction processing for correcting the generated tool path (S109).
The tool path that needs to be corrected is a case where the tool path is closed. In such a case, the start point and end point of the tool path do not match. Therefore, the tool path is corrected so as to coincide with the start point.
By performing the path correction process as described above, it is possible to create a tool path in which no cutting occurs even when the tool path is closed, or the uncut residue is minimized.

Next, the NC data conversion unit 118 converts the data into NC data that can be read by the numerical control device 4 in accordance with the tool path, the tool rotation speed, and the tool movement speed created by the tool path creation unit 111 (S110). As the NC data, for example, a G code is used.
Then, the CAM device 1 sends the converted NC data to the numerical control device 4, and the numerical control device 4 performs the curved surface machining by numerically controlling the curved surface machining device 5 according to the NC data (S111).

[Tool path creation]
Next, details of the tool path creation process (step S108 in FIG. 2) will be described with reference to FIG. 3 and FIG.
FIG. 3 is a flowchart showing the flow of the tool path creation process.
First, the curve calculation unit 1111 of the tool path creation unit 111 performs a curve calculation process for calculating a curve on the curved surface of the curved surface data (S201). The curve is created according to the route pattern set in step S106 on the curved surface limited according to the processing site. Details of the curve calculation process will be described later.
Next, the curvature reversal search / determination unit 1112 calculates a curvature direction vector at each position on the curve created in step S201, and a position where the curvature direction vector is reversed, that is, a position where the unevenness of the curve is reversed (unevenness reversal). The curvature inversion search process for searching / calculating (part) is performed (S202). Details of the curvature inversion search process will be described later with reference to FIG.
Then, the curvature inversion search / determination unit 1112 determines whether or not there is an uneven inversion unit on the curve as a result of step S202 (S203).
As a result of step S203, when the concave / convex inversion portion exists on the curve (S203 → Yes), the calculated coordinates of the concave / convex inversion portion are sent to the curve dividing portion 1113 in step S202. Then, the curve dividing unit 1113 divides the curve by the concave / convex inverting unit (S204), and returns to the process of step S202.

  As a result of step S203, when the unevenness inversion part does not exist on the curve (S203 → No), the curvature inversion search / determination part 1112 is based on the positional relationship between the curve and the curved surface divided in step S202, step S203, and step S204. Then, it is determined whether the corresponding curve is convex or concave (S205). The method for obtaining the positional relationship between the divided curve and the curved surface is, for example, that a straight line connecting the start point and the end point of the divided curve is created, and a point that does not include the start point and the end point (for example, the midpoint of the straight line) is a curved surface. A method is known in which it is determined whether the point is above / below and is convex when the point is below the curved surface and concave when the point is above.

(When the curve is convex)
As a result of the determination in step S205, if it is determined that the corresponding curve is convex (S205 → convex), the process proceeds to step S206.
In step S206, the machining allowance offset unit 1115 performs a convex machining allowance offset process for creating a curve obtained by offsetting the curve in the normal direction of the curved surface and offset by the remaining amount (S206). Details of the offset allowance offset processing will be described later with reference to FIG.
Next, the machining allowance offset unit 1115 sends the offset curve to the broken line creation unit 1116, and the broken line creation unit 1116 searches for the vertex of the broken line constituting the tool path between the curve and the offset curve, and the vertex Convex fold line creation processing is performed to create a fold line by connecting (S207). Details of the process for creating the convex folding line will be described later with reference to FIG.

Then, the tool determination unit 1114 acquires the tool type selected / set in step S105 of FIG. 2 from the tool type setting unit 114, and determines whether the tool type is a flat end mill (S208).
As a result of step S208, when it is determined that the type of tool selected / set in step S105 is not a flat end mill (S208 → No), the broken line creation unit 1116 offsets the created broken line by the tool radius, The broken line is sent to the path interpolation unit 1117. Then, the path interpolation unit 1117 performs path interpolation processing in the ball end mill (S209). Details of the path interpolation processing in the ball end mill will be described later with reference to FIGS.

As a result of step S208, when it is determined that the type of tool selected / set in step S105 is a flat end mill (S208 → Yes), the broken line creation unit 1116 offsets the created broken line by the tool radius, The broken line is sent to the path interpolation unit 1117.
Then, the path interpolation unit 1117 performs path interpolation processing in the flat end mill (S210). Details of the tool path interpolation processing in the flat end mill will be described later with reference to FIGS. 5 and 6.

(When the curve is concave)
Returning to the process of step S205, if it is determined that the corresponding curve is concave (S205 → concave) as a result of the determination in step S205, the process proceeds to step S211.
In step S211, the tool determination unit 1114 acquires the tool type selected / set in step S105 from the tool type setting unit 114, and determines whether the tool type is a flat end mill.

(Curve is concave: Ball end mill)
As a result of step S211, when it is determined that the tool type selected / set in step S105 is not a flat end mill (step S211 → No), the process proceeds to step S212.
In step S212, the end mill contact search unit 1118 performs an end mill contact search process in the ball end mill that calculates positions (overlapping contact points) where the ball end mill contacts the curve at two or more points (S212). Details of the end mill contact search process in the ball end mill will be described later with reference to FIG.
Then, a concave tool-specific offset process is performed to create a curve in which the curve is offset by the tool radius of the ball end mill (S213). When there is an overlapping contact point in the ball end mill as a result of step S212, the end mill contact searching unit 1118 sends the calculated overlapping contact point to the concave tool specific offset unit 1119, and the concave tool specific offset unit 1119 transmits After using the overlapped contact points, the offset processing for each concave tool is performed to create a curve in which the curve is offset by the tool radius of the ball end mill. Details of the offset processing for each concave tool will be described later with reference to FIG.

Next, the offset part 1119 for each concave tool sends the offset curve to the allowance offset part 1115, and the allowance offset part 1115 cuts the curve obtained by offsetting the sent offset curve in the normal direction of the curved surface by the remaining amount. The recess allowance offset process created for the end mill is performed (S214). The details of the recess allowance offset process will be described later with reference to FIG.
Then, the machining allowance offset unit 1115 sends the curve created by itself to the crease line creation unit 1116 together with the curve created by the curve calculation unit 1111 and the curve created by the offset tool-specific offset unit 1119, and the crease line creation unit 1116 Concave line creation processing for searching a vertex of a broken line constituting a tool path in a ball end mill based on a curve created by another offset portion and a curve created by a machining allowance offset portion 1115 and creating a broken line by connecting the vertexes (S215). Then, the broken line creation unit 1116 creates a tool path by connecting the vertices of the created broken lines. The details of the process for creating the concave line in the ball end mill will be described later with reference to FIG.

(Curve is concave: flat end mill)
As a result of step S211, when it is determined that the tool type selected / set in step S105 is a flat end mill (step S211 → Yes), the process proceeds to step S216.
Here, the procedure for creating the tool path when the curve is concave and the tool is a flat end mill (S216 to S219) is almost the same as that for the ball end mill. This will be described later with reference to FIG.

  Hereinafter, a detailed description of each process will be described with reference to the drawings as appropriate.

(Curve calculation process)
Here, the process of curve calculation (step S201 in FIG. 3) performed by the curve calculation unit 1111 will be described.
The curve is created, for example, by the method described in Non-Patent Document 1, pages 269 to 271 and FIG. 7.25, and the description is omitted in this specification. Here, a method of making the curve P (t) a curve on the curved surface S (u, v) (hereinafter referred to as a curved curve on the curved surface: the second curve in the claims) will be described.
Note that P (t), S (u, v), and the like are curves and curves, respectively. Other P ^A (t), N (t), and the like to be described later are similarly equations.

First, the curved surface format will be described.
The curved surface is expressed by Equation 1 so that one curved surface S (u, v) is determined when two parameters (u, v) are given. The storage device 3 (see FIG. 1) requires u-direction rank k, u-direction control points Z, v-direction rank l, v-direction control points M, (u-direction control points + u-direction rank) necessary to calculate Equation 1. U-direction knot sequence consisting of a single scalar quantity, v-direction knot sequence consisting of (v-direction control points + v-direction rank) scalar quantities, and control points consisting of (u-direction control points × v-direction control points) vector quantities Q _ij , which is stored as data of weight w _ij consisting of (u-direction control points × v-direction control points) scalar quantities.

In Equation 1, B-spline functions N _{i, k} (u) and N _{j, l} (v) in the u direction and v direction are calculated by the recursive equation of Equation 2.

  A curved line on a curved surface is described by creating a point on a curved line defined in space and projecting the point onto the curved surface. More specifically, when the curve P (t) is determined when the parameter t is given, the relationship between P (t) and the curved surface S (u, v) is constrained by Equation 3, and P (t) The parameter (u, v) of S (u, v) corresponding to the parameter t of

To implement using a computer, approximate equations shown in Equation 3 to Equation 4 are made. Since Equation 4 is a vector having three components (x, y, z), there are two variables and there are three equations that cannot be solved. Therefore, the update amount (δu, δv) is calculated by decomposing Equation 4 into each partial differential direction component as shown in Equation 5. Thereafter, (δu, δv) is added to the initial value (u ₀ , v ₀ ) of the convergence calculation, and Expression 5 is repeated. In this way, (u, v) corresponding to the variable t is calculated.

In Equations 4 and 5, S _u (u, v) is a single derivative with respect to the parameter u of the surface S (u, v), and S _v (u, v) is the parameter v of the surface S (u, v). Is the first derivative.
Using Equation 5, (u (t), v (t)) is obtained from P (t). As will be described later, since convergence calculation is also performed in the convex folding line creation process (S207), the end mill contact search process (S212, S216), the concave folding line creation process (S215, S219), etc., (u (t), v (t) t 1 times on the derivative _{of) (u t (t),} v t (t)), differentiated twice on _{t (u tt (t),} v tt (t)) it is also necessary to seek.
First, a method of calculating a single derivative with respect to t will be described using Expression 6.

When the curve P (t) is on the curved surface S (u, v), the first derivative P _t (t) in the parameter t of the curve P (t) is obtained by differentiating both sides of Equation 3 by t. It becomes like 6.
In Equation 6, u _t is a one-time differentiation of u (t) in the parameter t of (u (t), v (t)) representing the curve P (t) with the parameters u and v of the curved surface, v _t is a one-time derivative of v (t) in the parameter t.
To implement using a computer, Equation 7 is obtained by decomposing each partial differential direction component in the same manner as Equation 5.

By solving the simultaneous linear equations of Equation 7, a single derivative (u _t (t), v _t (t)) with respect to t is calculated.

Next, a method of calculating the second derivative with respect to t will be described using Expression 8.
When the curve P (t) is on the curved surface S (u, v), the second derivative P _tt (t) of the curve P (t) in the parameter t is obtained by differentiating both sides of Equation 6 by t, Equation 8 is obtained.

In Equation 8, u _tt is the second derivative of the parameter (u (t), v (t)) of the curved surface (u (t), v (t) in the parameter t, and v _tt is 2 in the parameter t of v (t). It is a time derivative. S _uu (u, v) is differentiated twice with respect to the parameter u of the curved surface S (u, v), and S _uv (u, v) is differentiated once with respect to the parameter u of the curved surface S (u, v). The quantity S _vv (u, v) later differentiated once with respect to the parameter v is a second derivative with respect to the parameter v of the curved surface S (u, v).

  To implement using a computer, Equation 9 is obtained by decomposing each partial differential direction component in the same manner as Equation 5.

By solving the simultaneous linear equations of Equation 9, the second derivative (u _tt (t), v _tt (t)) with respect to t is calculated.
By implementing a program that executes Equation 5, Equation 7, and Equation 9 in a computer, the curve calculation unit 1111 on the curved surface can obtain a curve (u (t), v (t) on the curved surface corresponding to the curve P (t). ), A one-time derivative ( _t (t), v _t (t)) with respect to t in the curved line on the curved surface, and a second derivative (u _tt (t), v _tt (t)) with respect to t in the curved line on the curved surface. Ask.

(Curvature reversal search process)
Next, the curvature inversion search process (step S202 in FIG. 3) by the curvature inversion search / determination unit 1112 will be described with reference to FIG.
FIG. 4 is a diagram for explaining the curvature inversion search process.
In the curvature inversion search process, when the curve P (t) is a combination of concave and convex as shown in FIG. 4, the curvature inversion search / determination unit 1112 uses the curve P (t) as a basis. This is a process of calculating a curvature direction vector and searching for the concave / convex inversion portion 401 that is a boundary between the concave portion and the convex portion based on the calculated curvature direction vector.

Hereinafter, the curvature inversion search process will be specifically described.
When the curve P (t) changes smoothly, the curvature direction vector becomes 0 at the boundary where the curvature direction vector is inverted. Also, when the curve P (t) changes non-smoothly, for example, when two arcs are connected, the curvature direction vectors of the previous arc and the previous arc have opposite directions at the boundary where the curvature direction vector is inverted. Turn to.
Using this property, the search for the concave / convex inversion unit 401 calculates the point where the curvature direction vector becomes 0, or calculates the curvature direction vector of the preceding and following curves at the connection point of the curve P (t), The point where the inner product of the curvature direction vector is negative may be calculated.
Expression 10 is a calculation formula for the curvature direction vector used in the search of the unevenness inversion unit 401.

(When the curve is convex)
Next, the processing of steps S206 to S210 in FIG. 3 (hereinafter referred to as convex and occasional line forming processing) will be described with reference to FIGS.
FIGS. 5A and 5B are diagrams for explaining the convex time-varying line processing. FIG. 5A is a convex offset allowance process, FIG. 5B is a convex line creation process, and FIG. It is a figure for demonstrating the process to offset.

(Protruding allowance offset processing)
First, the convex allowance offset processing by the allowance offset unit 1115 will be described along FIG. 5A with reference to FIG.
Allowance offset section 1115, the curve P (t) of the curved surface normal direction N (t) to the amount of uncut set at step S107 in FIG. 2 d offset by curve ^P A (t) (first in the claims Curve). The curve P ^A (t) is described by Equation 11.

(Convex fold line creation process)
Next, with reference to FIG. 1, the convex folding line creation processing (step S <b> 207 in FIG. 3) by the folding line creation unit 1116 will be described along FIG. 5B.
Polygonal line creation section 1116, between the curve P (t) (second curve) and the curve ^P A (t) (first curve), a straight line which contacts the curve P (t) curve ^P A (t ) And a point P ^A _n (n is a positive integer) are searched in order.
Specifically, the broken line creation unit 1116 first determines an arbitrary point P ₀ on the curve P (t). Next, the broken line creation unit 1116 calculates a tangent line 501 in contact with the curve P (t) at the point P ₀ . Next, the broken line creation unit 1116 calculates a point P ^A ₀ (first point in the claims) where the tangent line 501 intersects the curve P ^A (t) (first curve). Then, the broken line creation unit 1116 calculates a tangent line 502 (straight line that touches the second curve in the claims) that passes through the point P ^A ₀ and touches the curve P (t) (second curve). Then, the broken line creation unit 1116 calculates a point P ^A ₁ (second point in the claims) where the tangent line 502 intersects the curve P ^A (t). Thereafter, a similar process is performed to search for points P ^A _n by calculating points P ^A ₂ , P ^A ₃ . These points P ^A ₀ , P ^A ₁ , P ^A ₂ ... Are the vertices of the polygonal line to be created.
Then, the broken line creation unit 1116 creates a broken line by connecting the calculated points P ^A ₀ , P ^A ₁ , P ^A ₂ .
In the present embodiment, the point P ₀ specified first is the point on the curve P (t), but is not limited thereto, and may be an arbitrary point on the curve P ^A (t).

  Hereinafter, a method of calculating and searching the vertex of a broken line using mathematical formulas will be described.

Expression 12 is an expression for searching for a point where a tangent line on the curve P (t) intersects the curve P ^A (t).
In Equation ^12, t 1 time through the derivative of _{P A} t (t) is _{^{P A (t), P A}} tt (t) is differentiated twice about t of ^{P A (t), A1,} B1, C1 is the description This is a variable that has been replaced for clarity.
In Expression 12, up to two candidate points to be searched can be calculated by approximating the calculation expression up to twice differentiation in order to obtain the update amount δt. By this method, when there are a plurality of points where the tangent line on the curve P (t) intersects the curve P ^A (t), it is possible to search in detail.
Expression 13 is an expression for searching for a point where a straight line starting from a point intersecting with the curve P ^A (t) touches the curve P (t).

In Equation 13, P ^A ₀ is a point where tangents intersect on P ^A (t), and ^A 2, B 2, and C 2 are variables that are replaced for easy understanding.
In Expression 13, up to two point candidates to be searched can be calculated by approximating the calculation expression up to twice differentiation in order to obtain the update amount δt. By this method, it is possible to search in more detail when there are a plurality of contact points.

(Process to offset the created broken line by the tool radius)
Next, referring to FIG. 1, a process in which the broken line creation unit offsets the created broken line by the tool radius will be described along FIG.
Since the movement path of the tool in the actual NC machining is expressed as a locus of the center of the tool, it is necessary to offset the broken line created by the broken line creating unit 1116 by the tool radius.
Therefore, the broken line creation unit 1116 performs offset of the broken line as shown in FIG. However, if the created broken line is simply offset, a broken line break 503 occurs as shown in FIG. Therefore, in order to interpolate the disconnection unit 503, a route interpolation process by the route interpolation unit 1117 is performed.

(Path interpolation processing: Ball end mill)
6A and 6B are diagrams for explaining the path interpolation processing by the path interpolation unit. FIG. 6A is a diagram illustrating a ball end mill, and FIG. 6B is a diagram illustrating a flat end mill.
First, a path interpolation method in the ball end mill will be described with reference to FIG.
In FIG. 6A, P ₁ is a point where a tangent on the curve P (t) passing through P ₀ and the curve P ^A (t) intersect, and P ₀ and P ₂ are tangents of the curve P (t). N ₀ , N ₁ , N ₂ are normals of the curved surface at points P ₀ , P ₁ , P ₂ .
For contacts, the tool center point make the point that is offset by the radius R ₁ of the ball end mill in a direction normal to the curved surface. For example, Formula 14 is used for P ₀ and P ₂ .

In the case of intersecting points, the tool center point is determined in relation to the normal of adjacent points. For example, among the P ₁ in Formula 15, it may be used either.

  A tool path can be created so that the envelope surface created by the movement of the ball end mill is in contact with the machining surface by using the broken line connecting the points created in Formula 14 and Formula 15 as the tool path of the ball end mill. That is, the offset broken line break 503 described in FIG. 5C is interpolated. Therefore, a tool path that can leave the machining surface by the maximum amount d of the uncut material without cutting when the machining surface is convex is created without interruption.

(Route interpolation processing: Flat end mill)
Next, a path interpolation method in the flat end mill will be described with reference to FIG.
In FIG. 6B, P ₀ and P ₂ are contact points with the curve P (t), P ₁ is an intersecting point on the curve P ^A (t), N _{0, L} , N _{1 and L} are points P The reverse cutting direction vectors at ₀ and P ₁ are shown. N _{1, R 2} , N _{2, and R} are vectors of cutting directions at points P ₁ and P ₂ .
The tool path of the flat end mill is based on the directional relationship between the vector from the contact point to the intersecting point and the flat end mill tool axis direction L, or the vector from the intersecting point to the contact point and the directional relationship between the flat end mill tool axis direction L. Change the creation method. If this change is not made, the machined surface will be cut by a flat end mill.

For example, when moving from the contact point P ₀ to the intersecting point P ₁ , an inner product is created between the tool axis direction L of the flat end mill and the vector (P ₁ -P ₀ ), and the inner product is positive as shown in Expression 16. making point parallel translated by a radius R ₁ of a flat end mill tool center point in the opposite cutting direction when.

Further, when moving from the intersecting point P ₁ to the contact point P ₂ , since the inner product is negative as shown in Expression 17, a point offset by the radius R _{1 of the} flat end mill is created in the cutting direction.

  By using the broken line connecting the points created in Equation 16 and Equation 17 as the tool path of the flat end mill, the tool path can be created so that the envelope surface created by the movement of the flat end mill is in contact with the machining surface. Therefore, when the machining surface is convex, the machining surface is not shaved, and the machining surface can be left by the maximum amount of uncut material d.

  In the case of a tool having a small radius R on the outer peripheral portion of the flat end mill (radial end mill), the small radius R is created according to Formula 14 and Formula 15, and then the tool diameter minus the small radius R is equal to Formula 16 and Formula 17. Once created, a radial end mill tool path can be created.

  In this way, by creating a tool path having the machining surface, that is, the tangent of the curve P (t) as the locus of the tool tip, it is possible to create a tool path that does not cause cutting, and the NC simulator can perform cutting. A confirmation process becomes unnecessary.

(Recessed occasional line processing)
Next, the processing of steps S212 to S219 in FIG. 3 (hereinafter referred to as a concave and convex line forming process) will be described with reference to FIGS.
Since the concave time-varying process varies depending on the tool, the concave time-varying process in the ball end mill will be described with reference to FIGS. 7 and 8, and the concave time-lined line in the flat end mill will be described with reference to FIGS. 9 and 10. The conversion process will be described.

(Recessed occasional linearization: ball end mill)
First, along FIG. 7 and FIG. 8, a description will be given of a concave and convex line forming process (from step S212 to step S215 in FIG. 3) in the ball end mill.
FIGS. 7A and 7B are diagrams for explaining the concave and occasional linearization processing in the ball end mill, where FIG. 7A shows the end mill contact search processing, FIG. 7B shows the concave tool-specific offset processing, and FIG. The machining allowance offset process, (d) is a diagram for explaining the concave fold line creation process.

(End mill contact search process)
With reference to Fig.7 (a), the end mill contact search part 1118 by the end mill contact search part 1118 is demonstrated (step S212 of FIG. 3).

  When the tool is a ball end mill, curves 701 and 702 are created by offsetting the curve P (t) by the tool radius in the normal direction of the curved surface, and points (overlapping contact points) 703 at which the offset curves 701 and 702 self-intersect are created. Explore.

Hereinafter, the end mill contact search process in the ball end mill will be described using mathematical expressions.
Expression 18 is an expression indicating the search method and an expression when implemented in a computer.

In Equation 18, N (t) is the normal of the curved surface S (u (t), v (t)) on the curve P (t), and N (u) is the curved surface S (u ( u) and v (u)). N _t (t) is a first derivative of the normal N (t) with respect to the parameter t, N _tt (t) is a second derivative of the normal N (t) with respect to the parameter t, N _u (u ) Is the first derivative of the normal N (u) with respect to the parameter u, N _uu (u) is the second derivative of the normal N (u) with respect to the parameter u, R ₁ is the radius of the ball end mill, A3 B3 and C3 are replaced variables for easy understanding.

An initial value (t ₀ , u ₀ ) is given to the offset curve, and convergence calculation is performed according to Equation 18 to search for a self-intersecting point.
Equation 19 shows the normal N (t) of the curved surface S (u (t), v (t)), the first derivative N _t (t) with the normal parameter t, and the twice with the normal parameter t. It is a formula for _{obtaining the} differential N _tt (t). It should be noted that the two-fold differentiation with the normal parameter u may be performed by replacing t with u in Equation 19.

In Equation 19, A is the outer product of the u-direction derivative S _u (u, v) and the v-direction derivative S _v (u, v) on the curved surface S (u, v), and At is a one-time operation on _t of the outer product A. Differentiation, A _tt is the second derivative of the outer product A with respect to t, S _uu (u, v) is the third derivative with respect to the parameter u of the curved surface S (u, v), and S _uv (u, v) is the curved surface S ( u, v) is a one-time derivative with respect to a parameter v of a two-fold differentiation with respect to the parameter u, S _uvv (u, v) is 2 with respect to a parameter V of a one-time differentiation with respect to the parameter u of the surface S (u, v). The round derivative, S _vvv (u, v), is the third derivative with respect to the parameter v of the curved surface S (u, v).

(Offset processing by concave tool)
Here, the details of the offset method for each tool by the ball end mill will be described with reference to FIG.
FIG. 8 is a diagram for explaining the details of the offset method for each tool in the ball end mill.
In FIG. 8, P (t) is the curve before offset, N (t) is the normal of the curved surface at P (t), and R ₁ is the radius of the ball end mill.
The method of creating a curve offset by the tool radius of the ball end mill is performed according to Equation 20.

In Equation 20, P ^B (t) is a curve after offset (first curve in the claims).
In Expression 20, if the curvature inversion search / determination unit 1112 finds the overlapping contact point 703 (see FIG. 7A), the unevenness inversion unit 401 (see FIG. 4) or the end mill contact search unit 1118 finds the ball The end mill performs processing to make a curve obtained by offsetting a curve excluding the offset line of the part to be machined.

As a result of such processing, a curve P ^B (t) obtained by offsetting the tool by the radius of the tool is calculated in the curve P (t) as shown in FIG. 7B. For convenience of explanation, FIGS. 7B, 7C, and 7D have curves that are looser than those in FIG.

(Recessed offset processing)
Next, the recess allowance offset process by the allowance offset unit 1115 will be described with reference to FIG.
Allowance offset portion 1115, curved ^P B created in the concave tool by the offset process a (t) to the curved surface in the normal direction N (t) by uncut amount d set in step S107 offset curve ^P C (t) ( The second curve in the claims is created.

  Hereinafter, the recess allowance offset process in the ball end mill will be described using mathematical expressions.

In Expression 21, d is an uncut amount.
In this way, the machining allowance offset portion 1115 in the ball end mill offsets the curve P ^B (t) created by the concave tool-specific offset portion 1119 in the normal direction N (t) of the curved surface by the uncut amount d.

(Concave line creation process)
Next, the concave line creation process will be described with reference to FIG.
Tool, in the case of a ball end mill, line creation section 1116, the curve ^P B (t) and with the curve ^P C (t), a straight line which contacts the curve ^P C (t) is the curve ^P B (t) The intersecting points P ^B _n (n is a positive integer) are searched in order.
Specifically, the broken line creation unit 1116 first determines an arbitrary point P ^C ₀ on the curve P ^C (t). Next, the broken line creation unit 1116 calculates a tangent line 704 that contacts the curve P ^C (t) at the point P ^C ₀ . Next, the broken line creating unit 1116 calculates a point P ^B ₀ (first point in the claims) where the tangent 704 intersects the curve P ^B (t) (first curve). Then, the broken line creation unit 1116 calculates a tangent line 705 (straight line that touches the second curve in the claims) that passes through the point P ^B ₀ and touches the curve P ^C (t) (second curve). Then, the broken line creation unit 1116 calculates a point P ^B ₁ (second point in the claims) where the tangent line 705 intersects the curve P ^B (t). Thereafter, the same processing is performed to calculate and search for the points P ^B ₂ , P ^B ₃ . These points P ^B ₀ , P ^B ₁ , P ^B ₂ ... Are the vertices of the broken line to be created.
Then, the broken line creation unit 1116 creates a broken line by connecting the calculated points P ^B ₀ , P ^B ₁ , P ^B ₂ .
Since the determined broken line is a path through which the center of the tool passes, there is no need to perform path interpolation processing as in the case of convexity.
In the present embodiment, the point P ^C ₀ designated first is the point on the curve P ^C (t), but is not limited thereto, and may be an arbitrary point on the curve P ^B (t).

Hereinafter, the process of creating a concave fold line in the ball end mill will be described using mathematical expressions.
Equation 22 is tangent to the curve ^P C (t) is the expression for the search of the point of intersection with the curve ^P B (t). In Equation 22, A4, B4, and C4 are replaced variables for easy understanding. However, Expression 22 describes the curves P ^B (t) and P ^C (t) in an expanded form.

Expression 23 is an expression for searching for a point that passes through the intersecting point and contacts the curve P ^C (t). In Equation 23, A5, B5, and C5 are replaced variables for easy understanding. However, Expression 23 describes the curves P ^B (t) and P ^C (t) in an expanded form.

In this way, by creating the tool path so that the tool center point moves along the tangent line of the curve P ^C (t) offset by the remaining amount of cutting from the curve P ^B (t) offset by the tool radius, It is possible to create a tool path that minimizes uncut material. Thereby, the confirmation process of the uncut material by NC simulator becomes unnecessary.

(Recessed occasional line processing: flat end mill)
Next, along FIG. 9 and FIG. 10, a description will be given of the concave and convex line forming processing (steps S216 to S219 in FIG. 3) in the flat end mill.
FIGS. 9A and 9B are diagrams for explaining a concave and occasional linearization process in a flat end mill. FIG. 9A shows an end mill contact search process, FIG. 9B shows an offset process for each concave tool, and FIG. The machining allowance offset process, (d) is a diagram for explaining the concave fold line creation process.

(End mill contact search process)
First, the end mill contact search process (step S216 in FIG. 3) by the end mill contact search unit 1118 will be described with reference to FIG.
When the tool is a flat end mill, a curve 901 offset by the tool radius in the reverse direction of the curve P (t) and a curve 902 offset by the tool radius in the direction of travel are created, and the two offset curves 901 and 902 intersect. A point (overlapping contact point) 903 is searched.

Hereinafter, the end mill contact search process in the flat end mill will be described using mathematical expressions.
Expression 24 is an expression indicating the search method and an expression when implemented in a computer.

In Expression 24, M (t) is the cutting direction of the curved surface S (u (t), v (t)) on the curve P (t), and M (u) is the curved surface S (u () at the position P (u). The cutting directions of u) and v (u)), R ₁ is the radius of the flat end mill, and A 6, B 6, and C 6 are variables that are replaced for easy understanding.
An initial value (t ₀ , u ₀ ) is given to the curve obtained by offsetting the curve P (t), and the intersection point is searched by executing the convergence calculation according to Equation 24.
Expression 25 is an expression showing a calculation method of the cutting direction M (t) used in Expression 24. For M (u), the parameter t can be used by replacing the parameter t with u.

In Formula 25, B is first derivative _P t of the curve _{P t (t) (t)} , B t is the second derivative _P tt curve _{P t (t) (t)} , B tt curve _P t (t) _Is the third derivative P _ttt (t).

(Offset processing by concave tool)
Here, the offset method by a flat end mill is demonstrated along FIG.
FIG. 10 is a diagram for explaining the details of the offset method for each tool in the flat end mill.
In FIG. 10, P (t) is the curve before offset, M (t) is the cutting direction, and R ₁ is the radius of the flat end mill.
The method of creating a curve offset by the tool radius of the flat end mill is performed according to Equation 26.

In Equation 26, P ^B (t) is a curve after offset (first curve in the claims).
In Expression 26, the sign of the offset direction is determined before and after the overlapping contact point 903. This is to prevent cutting ahead of the overlapping contact point 903. The overlapping contact point 903 uses a point calculated by the end mill contact searching unit 1118 according to Equation 24.

As a result of such processing, a curve P ^B (t) obtained by offsetting the tool by the radius of the tool is calculated in the curve P (t) as shown in FIG. 9B. For convenience of explanation, FIGS. 9B, 9C, and 9D have curves that are looser than those in FIG.

  In the case of a tool having a small radius R on the outer periphery of the flat end mill (radial end mill), it is possible to create a radial end mill by creating a small radius R by Formula 20 and then creating a tool radius minus a small radius R by Formula 26. An offset can be created.

(Recessed offset processing)
Next, the recess allowance offset processing by the allowance offset unit 1115 will be described with reference to FIG.
Allowance offset portion 1115, the amount of uncut curve P ^B created in the concave tool by the offset process a ^(t) to the curved surface in the normal direction N (t) d offset by curve P ^{C (t)} (first in claim 2 Curve).

  Hereinafter, the recess allowance offset process in the flat end mill will be described using mathematical expressions.

By such processing, in the case of a flat end mill, a curve P ^C (t) (second curve in the claims) is created by offsetting the curve P ^B (t) by the uncut amount d.

(Concave line creation process)
Next, the concave line creation process will be described with reference to FIG.
When the tool is a flat end mill, the only difference from the ball end mill is the part that creates the curves P ^B (t) and P ^C (t).
Specifically, the broken line creation unit 1116 first determines an arbitrary point P ^C ₀ on the curve P ^C (t). Next, the broken line creation unit 1116 calculates a tangent 904 that is in contact with the curve P ^C (t) at the point P ^C ₀ . Next, the broken line creation unit 1116 calculates a point P ^B ₀ (first point in the claims) where the tangent 904 intersects the curve P ^B (t) (first curve). Then, the broken line creating unit 1116 calculates a tangent line 905 (straight line that touches the second curve in the claims) that passes through the point P ^B ₀ and touches the curve P ^C (t) (second curve). Then, the broken line creating unit 1116 calculates a point P ^B ₁ (second point in the claims) where the tangent 905 intersects the curve P ^B (t). Thereafter, the same processing is performed to calculate and search for the points P ^B ₂ , P ^B ₃ . These points P ^B ₀ , P ^B ₁ , P ^B ₂ ... Are the vertices of the broken line to be created. However, while doing the treatment was calculated by end mill contact search process, when bumped into overlapping contact point 903 (see FIG. 9 (a)), at which point, newly obtained the P ^C _0, the same Repeat the process.
Then, the broken line creation unit 1116 creates a broken line by connecting the calculated points P ^B ₀ , P ^B ₁ , P ^B ₂ .
In the present embodiment, the point P ^C ₀ designated first is the point on the curve P ^C (t), but is not limited thereto, and may be an arbitrary point on the curve P ^B (t).

Hereinafter, the process of creating a concave fold line in the flat end mill will be described using mathematical expressions.
Formula 28, the contact line of the curve ^P C (t) is an expression for searching for a point which intersects the curve ^P B (t). However, Equation 28 describes the curves P ^B (t) and P ^C (t) in an expanded form. In Expression 28, A7, B7, and C7 are variables replaced for easy understanding.

Expression 29 is an expression for searching for a point that passes through the intersecting point and contacts the curve P ^C (t). However, in Equation 29, the curves P ^B (t) and P ^C (t) are described in an expanded form. In Expression 29, A8, B8, and C8 are replaced variables for easy understanding.

In this way, by creating the tool path so that the tool center point moves along the tangent line of the curve P ^C (t) offset by the remaining amount of cutting from the curve P ^B (t) offset by the tool radius, It is possible to create a tool path that minimizes uncut material. Thereby, the confirmation process of the uncut material by NC simulator becomes unnecessary.

(effect)
According to the present invention, since it is possible to eliminate the cutting of the machining shape by moving the tool without reducing the interval between the contact points, the number of points used for the tool path is reduced, resulting in acceleration / deceleration during tool movement. Since the time is reduced, the machining time can be shortened. Further, since the amount of NC data decreases, the NC data transfer time can be reduced. As a result, the actual cutting time by the curved surface processing apparatus 5 (see FIG. 1) can be increased. In addition, since it is possible to eliminate the confirmation process of cutting or uncut material using the NC simulator, the NC simulator can be omitted, the time until NC data creation is reduced, and the waiting time until the curved surface processing apparatus 5 operates is reduced. It is possible to reduce the work time of the NC data creation worker. As a result, the number of processing steps can be reduced.

It is a block diagram which shows the structural example of the CAM system which concerns on this embodiment. It is a flow which shows the flow of a process of NC data creation in the CAM system which concerns on this embodiment. It is a flow which shows the flow of a process of tool path creation. It is a figure for demonstrating a curvature inversion search process. It is a figure explaining a convex time-varying process, (a) is a convex margin allowance offset process, (b) is a convex crease line creation process, (c) is a process which offsets the created crease line by the tool radius. It is a figure for demonstrating. It is a figure for demonstrating the path | route interpolation process by a path | route interpolation part, (a) is a figure in the case of a ball end mill, (b) is a figure which shows the case of a flat end mill. It is a figure for demonstrating the concave occasional linearization process in a ball end mill, (a) is an end mill contact search process, (b) is an offset process classified by concave tool, (c) is a concave allowance offset process. (D) is a figure for demonstrating a concave folding line creation process. It is a figure explaining the detail of the offset method classified by tool in a ball end mill. It is a figure for demonstrating the concave and occasional linearization process in a flat end mill, (a) is an end mill contact search process, (b) is an offset process according to a concave tool, (c) is a concave allowance offset process. (D) is a figure explaining a concave crease line creation process. It is a figure explaining the detail of the offset method classified by tool in a flat end mill. It is a figure for demonstrating the cutting and uncut part when a ball end mill is used for a tool, (a) shows the time of a processing surface being a convex state, (b) shows the time of a processing surface being a concave state. . It is a figure for demonstrating the tool path | route at the time of offsetting the processing surface in the past, (a) shows the time of a processing surface being a convex state, (b) shows the time of a processing surface being a concave state.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 CAM apparatus 2 CAD apparatus 3 Memory | storage device 4 Numerical control apparatus 5 Curved surface processing apparatus 11 Processing part 111 Tool path | route preparation part 112 Curved surface data reading part 113 Processing site | part setting part 114 Tool type setting part 115 Path | route pattern setting part 116 Specification / Uncut amount setting unit 117 Path correction unit 118 NC data conversion unit 1111 Curve calculation unit 1112 Curvature reversal search / determination unit 1113 Curve division unit 1114 Tool determination unit 1115 Stock allowance offset unit 1116 Polygonal line creation unit 1117 Path interpolation unit 1118 End mill contact search unit 1119 Offset by concave tool

Claims (7)

A tool path creation method in a CAM device for creating tool path data, which is a path along which a tool moves during curved surface cutting,
The CAM device is
Read the shape data of the outer shape of the object to be processed from the storage device holding the shape data,
Based on the read shape data, calculate a curve along the shape specified by the shape data,
Calculating a first curve and a second curve obtained by offsetting the curve by different offset amounts;
Calculating a first point which is an arbitrary point on the first curve;
From the first point, calculate a straight line in contact with the second curve,
Calculating a second point where the straight line intersects the first curve;
A tool path creating method, wherein the tool path is created by calculating a straight line connecting the first point and the second point. The second curve is a curve in which the offset amount is 0,
The tool path creation method according to claim 1, wherein the first curve is a curve obtained by offsetting the shape data by an offset amount different from that of the second curve. The CAM device is
The tool path creation method according to claim 2, wherein a straight line obtained by offsetting the created tool path by a radius of the tool is calculated. The CAM device is
Calculation of the first point, calculation of the second point, calculation of the straight line connecting the first point and the second point, and calculation of a straight line obtained by offsetting the tool path by the radius of the tool Repeat at least twice,
4. The tool path creation method according to claim 3, wherein straight lines offset by a radius of the plurality of tools are connected by performing interpolation processing between straight lines offset by a radius of the plurality of tools. The first curve is a curve obtained by offsetting the shape data by an offset amount that is a value of a radius of the tool,
2. The tool path creation method according to claim 1, wherein the second curve is a curve obtained by offsetting the first curve by an offset amount larger than a radius value of the tool. The CAM device is
Before calculating the first curve and the second curve, calculate a curvature direction vector of the curve in the shape data,
The tool path creation method according to claim 1, wherein a boundary between a concave and a convex of the shape data is detected based on the curvature direction vector.   A tool path creation program that causes a computer to execute the tool path creation method according to claim 1.

Images