JPH03239448A - Machining burr preventing method in computer numerical control (cnc) machine tool - Google Patents

Abstract

PURPOSE:To prevent the occurrence of burr at both machining start and end points of a workpiece by adding such a circular arc as smoothly contacting before or after the final machining form in order to compensate a nose radius R of a machine tool used with a computer numberical control (CNC) device. CONSTITUTION:In order to compensate a nose R in a computer numerical con trol device (hereinafter referred to as a CNC device) with a cutting tool with this nose R at the cutting edge, when the first block R0-R1 inclusive of a starting point R0 of the final machining from is a straight line as well as when the block R0-R1 is a concave circle, such a proper radial convex circle as smoothly contacting with the block R0-R1 is inserted thereinto before the first block R0-R1. Then, each of blocks Q0-P0, P0-P1 that offset the insert circular arc and the first block R0-R1 as far as a portion of nose value (r1) are formed into the offset form to the starting point R0. Likewise, the circular arc smoothly contacting with it is inserted thereinto after the last block inclusive of an end point of the final machining form. Thus, the nose R is compensated, and burr at machining a workpiece is prevented from occurring.

Description

[Detailed Description of the Invention] [Industrial Application Field] This invention relates to a computer numerical control device (hereinafter referred to as CNC).
The present invention relates to a method for correcting nose radius in a machine tool using a device (referred to as a device).

[Conventional technology]

A machine tool using a CNC device dynamically generates and compensates the machining bus of the cutting tool by inputting the final machining shape data of the workpiece and the data of the circular arc, or nose radius, of the cutting tool's cutting edge. Machining: Turning a 3° object.

FIG. 7 is a block diagram of a lathe using a conventional CNC device. In the figure, (1) is a CNC device, (2) is a central processing unit (hereinafter referred to as CPU), (31 is a memory in which control programs and machine programs are stored, (4)
is a keyboard which is an input means, (5) is a CRT, (6)
is a servo drive means consisting of an axis movement control section, a servo amplifier, etc.

(7) is a lathe controlled by CNC device "1". (8) is a workpiece, (9) is a chuck that grips the workpiece (8), and flol is a lathe that is controlled by the CNC device (1). The spindle motor rotates the object (8), (11) is a cutting tool as shown in Fig. 8 for turning the rotating workpiece (8), and f121 is a tool holder that holds the cutting tool (11). (13) is a control signal from the servo drive means (6) to move the cutting tool (11) in the Z-axis direction, which is the rotational axis direction of the workpiece (8), and in the X-axis direction, which is perpendicular to the rotational axis direction. This drive unit has two servo motors that move independently.

In addition, in the figure showing the tip of the cutting edge in Fig. 8, 3 [1: iH
i indicates the nose R circle, (CI) ii the center of the nose R (141), (r, H the nose R value indicating the radius of the nose R (14), (16) when machining the workpiece (8i) This is a virtual cutting edge point which is a point that controls the cutting edge of the cutting tool (11).

In the CNC device lathe configured as above, CP
The U (21) accesses the control program stored in the memory (3) in advance and executes the IIN instructions one by one to perform a series of processing. The cutting tool (1N) is accessed by accessing the cutting tool (1N) on the X-Z coordinates, and the difference between the current position and the calculated position, that is, the distance traveled by the cutting tool (11), is calculated. is input to the servo drive means (6).

The servo drive means (6) connects the drive unit (13) of the lathe (7).
): This pulse control signal is sent to move the cutting tool (11) in the X-axis direction and the Z-axis direction using two servo motors to turn the workpiece (8).

When machining this workpiece (8), the CNC machine (1
) can only control the -4 point position of the cutting tool (51), so as shown in the explanatory diagram of Fig. 9 fa) and (bl), cutting is performed at the position of the final machined shape (16). When the cutting tool (11) is controlled by matching the virtual cutting edge point (16) of the tool (11), the actual cutting with the cutting tool (11) becomes if![17]. Therefore, Fig. 9 (
As shown in a), when the virtual cutting edge point (16) moves in two axes and the X-axis coordinate value increases, there will be uncut material in the area between the final machined shape (18) and the line (17). occurs. Also, as shown in Figure 9 (bl), the virtual cutting edge point (1
6) moves in two axial directions and the X-axis coordinate value decreases, excessive cutting occurs in the range between the final machined shape (18) and the line (17).

For this purpose, the final processed shape (
18), find a shape (one) through which the nose R center (cI) offset by the nose R value (r,) passes through, and from this shape (19), the nose R center (CI) and the virtual cutting edge point (
By subtracting the X-axis component and Z-axis component of the vector (A) connecting When the core (C1) is the point at which the cutting tool (16) descends (
=, nose R value fr+l for final processed shape (18)
The nose R center (C1
) can be controlled together.

That is, in any case 6, the cutting tool ( 11) The offset shape considering the cutting edge nose R value (rl) is determined and the workpiece (
By processing 8), it is possible to prevent uncut parts or excessive cutting from occurring in the final machined shape.

Figure 11 shows the center of the nose R (C,) and the cutting tool (11).
FIG. 3 is an explanatory diagram showing a machining state when the point is set as a control point. As shown in the figure, the final processed shape (Xδ
), find the offset shape (19) corrected by the nose R value (r-). After that, find the tool bus (21) cut horizontally at a certain depth, and find the offset shape (19)
7) Cutting tool (11) by sequentially moving the nose R center (C1) from the -th layer of the tool bus (21)
can be controlled. In addition, in Figure 11 (22
) indicates the program origin.

Next, a description will be given of means for determining the offset shape (17) at the start and end points of the final machined shape when the center of the nose R (C1) is taken as the control point of the cutting tool (11).

As shown in Fig. 12, if the shape connecting the starting point (R,1) of the final machining shape and the next point (R3) is a straight line, the block (
A line segment (Q, -P,) is added in front of the block (p, -p,) in which Ro-R11 is shifted by the nose R value (rI), and (Q.

Pa-Pl) is the offset shape at the starting point (Ro).

As shown in FIGS. 13(a) and fb), when the shape connecting the starting point (Ro) and the next point (R3) of the final machining shape is a circular arc, the following procedure is performed. When the block (R, -R, l is a concave circle, the block (Ro-
R, l are divided into blocks fpo-p by the nose R value (rl) toward the center (c) of block (tto-R11)
Add line molecule Q,'-P,) in front of +l, foe
-po-p++ is the offset shape at the starting point (Ro). If the block (R, -R, l is a convex circle, the first
As shown in Figure 3 (b), the flock (RO-R11 is placed in front of the block fP, -P, l, which is widened by the center of the block (R, -R, l) by the outward nose R value (rl) when viewed from C1. Add the line segment (Q, -P, l, and let (Q, -P, -P,) be the offset shape at the starting point (Ro).

In either case of Figures 12 and 13 (a) and fb, the X coordinate of the point (qo) and the X coordinate of the two points (P,) (Oo
) 2 coordinates = Z coordinate of starting point (Ro) + cutting tool (11)
The required movement value (αZ) during the approach of

Next, we will describe how to obtain the offset shape at the end point of the final machined shape.

As shown in Fig. 14, if the shape connecting the end point (R,) of the final processed shape and the previous point (R, -, l is a straight line, the block '(R,, -t-Rs) is A line segment (P
, -0,) and let (P, , -I-Pn-ro, ,) be the offset shape at the end point (R,, l).

As shown in FIG. 15(a) and (bl), if the shape connecting the end point (Rnl) of the final processed shape and the previous point (R, -1) is a circular arc, do as follows.

First, if the block [R,, -R,,) is a concave circle, the block fR,, -, -R,
, l are divided into blocks (p, +-
Add the line segment (P, , -Q, l after p, l, and (
P, , -, -P, , -Q, , ) is the offset shape at the end point (R7). Block (R,, -, -R,,
1 is a convex circle, the block fRn-+-Rn) is changed to the block (R,, -1-R,
, the center of l (as seen from cl, the outer nose R (r, block (p, -P,) expanded by 1 minute, and then the line molecules P, -Q, l
, and let (P, -, -P, -Q,) be the offset shape at the end point fRnl.

14 and 15 (a), < bl In either case, X coordinate of point (Q, l = X coordinate of end point (R,) + allowable movement value (αX ) Z coordinate of point (Q7) = Z coordinate of point fP, ).

[Problems to be Solved by the Invention] Conventionally, creating an offset shape involves adding a line segment parallel to the Z-axis at the beginning of the offset shape with respect to the final processed shape, and finally adding a line segment parallel to the X-axis. This is the method,
The shapes of the first block containing the start point and the last block containing the end point of the final machining shape are ignored. For this reason, when the final machined shape is actually machined, there is a problem in that burrs occur at the starting point, end point, and point.

The present invention was made to solve the above problems, and its object is to prevent burrs from forming during machining using a CNC machine tool at the start and end points of a final machined shape.

[Means to solve the problem]

A method for correcting a nose R in a CNC machine tool according to the present invention uses a cutting tool having a nose R at the cutting edge, and a method for correcting a nose R for obtaining an offset shape with respect to a final machined shape. Insert a circular arc that smoothly contacts the forendum of the first block, and insert a block in which the inserted circular arc is offset by the nose R value ("l") and the first block that includes the starting point of the final machining shape by the nose R value (" The two blocks offset by l) are set as an offset shape to the start h of the final machining shape, ■ Insert a smoothly touching circular arc after the last block that includes the end point of the final machining shape, ■ The end point of the final machining shape Nose R the last block containing
A feature is that an offset shape is created so that two blocks, a block offset by a value (r,) and a block offset by an inserted circular arc by a nose R value (r, 1 minute), are offset shapes with respect to the end point of the final machining shape. shall be.

[Effect]

In a CNC machine tool, a cutting tool having a nose radius at the cutting edge can be used to machine a workpiece without generating burrs.

[Embodiments of the invention]

FIG. 1 is a block diagram of a lathe using a CNC device showing one embodiment of the present invention, and in the figure, (1) to (13)
) indicates exactly the same as the conventional diagram shown in FIG.

The operation of the above embodiment will be explained below.

Refer to Figures 2 to 5, and see the final processed shape (18)
The operating principle for finding the offset shape (19) with respect to the starting and ending points will be explained.

As shown in Figure 2, the first block including the starting point (Ro) of the final machining shape (when RQ-R11 is a straight line and the third
As shown in the figure (bl), if the block (R, -R,) is a concave circle, set an appropriate radius before the first block (Ro-R1) so that it smoothly touches the block fRo-R,l. Insert a convex circle of , and insert the inserted arc and the first block fR
o-R1) offset by the nose R value (r,), the flock (QQ-POI), (po-pi is set as the starting point (R)
The shape is offset from o).

As shown in Figure 3 (al), the first block (R, -
If R, ) is a convex circle, insert a bi-circle with an appropriate radius that smoothly touches block (R, -R1) before block tRO-R11, and connect the inserted arc and the first block (RoR
, l) offset by the nose R value tr + 1 minutes (Q, , -Pol , (Po-P, l starting from 61
It has an offset shape with respect to Ra+.

In both cases, Z coordinate of point (Qo) = Z coordinate of starting point (Ro) + cutting tool (
11) is the allowable movement value (αZ) during approach. (Once the Z coordinate is determined, the X coordinate of the point (Qo) can be determined.) As shown in Figure 4, the last block containing the end point (R7) of the final machining shape (if Rゎ1, -R, l are straight lines) and,
As shown in FIG. 5(b), the block (R, -, -RI,
) is a concave circle, insert a convex arc of an appropriate radius that smoothly touches 5 blocks (R-1-R-1) after the block (R,, -, -R,), and connect the powerful arc and the last block(
R.

Let the blocks CP, , -P, , ), fP, -Q, , l which are obtained by offsetting R, , ) by the nose R value (rl) be offset shapes with respect to the end point (R, , ).

As shown in Figure 5 (al), the last block (R, -
-R7) is a convex circle, 5 blocks (R, -, -R,)
After , insert a concave arc of an appropriate radius that smoothly touches the block (R,, -, -R,, l, and set the strong arc and the last block (R,, -R,, l to the nose R value (rl )
Block offset by minutes (p, -, -p, l,
Let ip,-o,) be the offset shape with respect to the end point (R,).

Figures 4 and 5 [a] (b) In both cases, the point [Q,
, X coordinate of l = end point (R, X coordinate of l + cutting tool (11
) is the allowable movement value (αX) during approach. (Once the As a point to control the center (C1).

The case of cutting the final machined shape (18) will be explained with reference to the flowchart of FIG.

First, it is determined whether the block with the final machining shape is the starting point block, and (step Sl) if it is the starting point block,
Depending on the shape, insert a concave arc or a convex arc.Step S2
), an offset block is created for the insertion arc and the starting point block (step S3). The offset block is added to the offset shape film (Ste Tsubu S
4). If it is not the starting block, it is determined whether it is the final block (step S5); if it is the final block, a concave or convex arc is inserted depending on its shape (step S6).
, the final block and the offset/soto block of the insertion arc are created, and the created offset pro/c is added to the offset shape film (step S7). If it is not the final block, an offset block is created for that block (step S3), and an addition is added to the offset shape film (step S4). After creating the offset shape up to the final block, if there is a closed loop in the continuous offset shape film, delete the closed loop (step S8), and final offset shape (18)
Create.

Burrs can also be prevented during machining using a cutting tool that has nose radii on both sides of the cutting edge.

〔Effect of the invention〕

As described above, in a CNC machine that uses a cutting tool with a nose radius on the cutting edge, by adding circular arcs that touch smoothly before and after the start and end points of the final machining shape,
Since the cutting tool moves smoothly between the machining start point and the machining end point, it is possible to prevent the occurrence of burrs at the machining start point and machining end point.

[Brief explanation of drawings]

Figures 1 to 5 relate to an embodiment of the present invention, in which Figure 1 is a configuration diagram of a CNC machine tool, and Figures 2 to 5 are explanatory diagrams showing the operating principle when determining an offset shape. , 6th
15 to 15 relate to a conventional device, FIG. 6 is a flowchart showing the operating state, FIG. 7 is a configuration diagram showing the tip of the cutting tool, and FIGS. 8, 9, and 10. 11 to 15 are explanatory diagrams showing the processing state, and FIGS. 11 to 15 are explanatory diagrams showing the operating principle when determining the conventional offset shape. Tl)...-CNC device, (2)...CPU, (3)
...Memory, (4)...Keyboard, (5)...
・CRT, (6) ... Servo mechanism, (7) ... Lathe, (8) ... Workpiece, (9) ... Chuck, (
lO)... Spindle motor, (11)... Cutting tool,
f12)...Tool holder, (131...Drive unit. In addition, the same line numbers in the figure are the same,

Claims (1)

[Claims] In the nose radius correction method that uses a cutting tool with a nose radius on the cutting edge and obtains an offset shape from the final machined shape, the generation of burrs can be avoided by adding circular arcs before and after the final machined shape and then correcting the nose radius. A method for preventing burrs during machining in a CNC machine tool, which is characterized by preventing burrs.