JPH02180541A - Corner override method for numerical control device - Google Patents

Abstract

PURPOSE:To simplify the structure of a tool feeding NC device by equipping an override value arithmetic part, a speed adjustment arithmetic part and an interpolation arithmetic part, calculating in order the contact area of the tool approaching to a corner part and making cutting load constant by controlling cutting amt. at constant speed. CONSTITUTION:An override value arithmetic part 1 inputting the override value OVR 1 input from the accumulated movement amt. Xi of by the radius R and cutting allowance L of a tool, corner angle theta and block movement amt. X and the current block, and a machine pendant and outputting the override value OVR 2 of at the corner part from the ratio of the tool contact angles before and after coming into the corner part, is provided. Moreover, a speed adjusting arithmetic part 2 outputting the speed command Fi of the time when the next block and tool are brought into contact and an interpolation arithmetic part 3 outputting the moving command operated from an interpolation locus and the above speed command Fi are provided. Thus, the feeding speed is controlled so that the cutting amt. becomes constant automatically by finding the aiming position of every moment.

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention provides numerical control (hereinafter N
This invention relates to a control method (referred to as C), and particularly relates to a corner override method in which speed is automatically controlled so that the amount of cutting per unit time is constant at the corner portion of a workpiece.

[Conventional technology] Conventionally, when cutting the inner surface of a workpiece such as pocket machining with an end mill, if cutting is performed at a constant speed, the amount of cutting per unit time, that is, the metal removal rate, increases rapidly at the corners, the cutting load becomes large, and the tool This has a negative effect on the wear and surface roughness of the cut surface. To prevent this, it is possible to reduce the speed at corners, but the movement command of the NC device is given as a single movement such as a straight line or arc, that is, a collection of blocks, and the feed speed command is also given in blocks. Therefore, in order to change the speed command in the middle of a block, it is necessary to predict the load fluctuation of the tool at the corner and give a speed command that matches the cutting conditions, or set the override value in multiple stages in advance so that the cutting progresses. As the process progresses, the override value is changed for each stage (for example, Japanese Patent Laid-Open No. 105870/1983).

[Problems to be Solved by the Invention] However, in order to subdivide and set the movement command for each block near the corner into multiple stages, a large number of setting means are required, and especially when the corner angle is larger than a right angle, the movement command The disadvantages are that it takes time to set up, the structure of the program and arithmetic circuit becomes complicated, and the cutting time increases.

[Means for Solving the Problems] The present invention is based on the tool radius, cutting allowance, corner angle, block movement amount from the origin to the final point of the q-ner of the tool center, and the deceleration point. , the travel distance from the deceleration point, the cumulative travel amount in the current block, and the override value in the current block input from the machine pendant, and calculate the tool contact angle in the current block and the tool contact at the corner. An override value calculation unit that calculates the angle and outputs an override value at the corner from the ratio of the tool contact angle before and after entering the corner, and calculates the next block and tool based on the override value at the corner and the commanded feed rate in the program. It is equipped with a speed acceleration/deceleration calculation unit that outputs a speed command when the contact occurs, and an interpolation calculation unit that outputs a movement command calculated from the interpolation trajectory and the speed command, and calculates the target position moment by moment and calculates the cutting amount. Corner override method of NC device that automatically controls the speed so that it is constant [
] If the cutting dimensions of the tool and workpiece are constant, the cutting load is proportional to the cutting amount per unit time, and the cutting amount is considered to be the contact area between the tool and the workpiece multiplied by the tool feed rate. In addition, as shown in Fig. 2, the contact area S shown by the thick line is expressed as the product of the tool radius R and the tool contact angle Φ, and the cutting depth in the axial direction of the tool T, the cutting allowance L1, and the tool radius R are Considering that it is normally constant, a change in the contact area S is proportional to a change in the contact angle Φ of the tool T. Therefore, when the tool T moves from the center point B to C in the direction of the arrow P, the override value should be changed so that the tool feed rate command is decreased in proportion to the increase in the tool contact angle Φ1 at the corner. For example, the speed is automatically controlled so that the cutting amount becomes constant, and the cutting load becomes constant.

[Example〕 The present invention will be described with reference to embodiments shown in the drawings.

FIG. 1 is a block diagram showing an embodiment of the present invention, and numeral 1 indicates an override value calculation section at a corner portion.

The inputs are the values set in the program, such as the tool radius R of the tool T shown in Fig. 2, the machining allowance, the cutting surfaces H1 and H2 forming the corner part, or the current block Gl currently being machined and the next The corner angle θ formed with the next block G2 to be machined, the block movement amount X from the origin A to the corner final point C of the tool center moving in the direction of the arrow P, and the deceleration point B, that is, the tool T on the cutting surface H2. A deceleration point X6 expressed as the distance to the center point of the tool T in contact, a moving distance X1 from the decelerating point X, and a cumulative moving amount X in the current block Gl.
l and the override value 0VR1 in the current block Gl input from the mechanical pendant. From these input values, calculate the tool contact angle Φ before the corner. and the tool contact angle Φ at the corner part, and the override value 0VR2 at the corner part is determined as 0VR2=OVR1* (Φc
10υ (1) and outputs the override value 0VR2 from the override value calculation unit l.

In addition, Φ0 is Φc=arccO8((RL)/R) −(2)Φ
1 is Φ, :ll r c cos ((R-L+)
/R)+π−θ...(3
) Here, L,=X, S i n (π−θ) −
(4)X1=X+-Xd...
・(5)X, =X −L/ cos (θ−π/
2) ...(6) becomes.

2 is the speed acceleration/deceleration calculation section, and the input is the override value 0VR.
2 and the commanded feed rate F on the program. Then, the command feed rate F1 when the tool T contacts the next block, the cutting surface H2, is calculated and output as F = OVR2*FC = OVR1* (Φc/Φl) *FC-(7).

3 is a known interpolation calculation unit, which calculates the interpolation trajectory and the commanded feed rate F,
The momentary target position is determined from this and output as a movement command. Reference numeral 4 denotes a control unit for the feed motor M, which controls the speed of the feed motor based on the movement command to move the tool.

The conditions for executing automatic corner override are as follows:
(1) The machined surface is cutting the inner surface of the corner, (2) the tool has reached the corner deceleration point, and (3) the corner is commanded by a straight polygonal line.

To determine whether or not the inner surface of a corner is to be cut, the corner angle θ should be determined by turning counterclockwise when the current block Gl is on the left side with respect to the direction of movement P of the tool T, and turning counterclockwise when it is on the right side, as shown in Figure 3. When θ is less than π (180 degrees) when clockwise, it is determined that internal cutting is being performed. The fact that the corner deceleration point X has been reached is determined by comparing the deceleration point X and the cumulative movement amount X in absolute value, and Ix+1>=xdl. The fact that a corner is a straight line is determined by the fact that the next block is a straight line.

When these conditions are met, (1), (3), (5)
, (7) are repeated to perform tool feed control with a constant cutting amount at the corner portion.

FIG. 4 is a flowchart when performing feed control by the apparatus of the above embodiment. First, input conditions (tool radius R
1. Cutting allowance, corner angle θ, commanded feed rate F C% block movement amount X1 deceleration point X4, etc.) are set and input into the cutting program (step 11).

Next, it is determined whether the corner override mode is set (Step 12), and if No, the condition is for machining without corners (Step 13).

If YES, check whether the next block is a straight line (Step 14), then check that the corner angle θ is smaller than π (Step 15), and then Φ. ,X,,X,
, π-θ are initialized (step 16). Next, it is confirmed that the cumulative movement amount X, has passed the deceleration point X, (step 17), L, Φ2. Calculate the corner override value 0VR2 (step 18), then calculate the command feed speed F at the corner (step 19), and perform interpolation calculations together with the interpolation locus information (step 20).
, outputs a movement command. Next, the cumulative movement amount X in block units.

is updated from time to time (Step 21), and it is confirmed whether the tool movement of one block has been completed (Step 2).
2) Complete.

[Effects of the Invention] As described above, according to the present invention, the contact area of the tool, which changes as the tool enters the corner, is calculated sequentially during cutting, and the speed is automatically adjusted to keep the cutting amount constant. Since the cutting load is controlled, the cutting load is always constant, and there is no need to take into consideration such things as providing a sensor to detect cutting load fluctuations at corners in the program. However, it is possible to automatically override the cutting amount to a constant value, so the tool feed NC
This has the effect of simplifying the device structure and programming.

[Brief explanation of the drawing]

FIG. 1 is a block diagram showing an embodiment of the present invention, FIGS. 2 and 3 are explanatory diagrams, and FIG. 4 is a flow chart. l...Override value calculation section, 2...Speed acceleration/deceleration calculation section, 3...Interpolation calculation section Patent applicant: Anyo Electric Manufacturing Co., Ltd. Boiled soup, ht>h

Claims (1)

[Claims] 1. The radius of the tool and the cutting allowance set by the program,
The corner angle, the amount of block movement from the origin to the final corner point of the tool center, the deceleration point, the movement distance from the deceleration point, the cumulative amount of movement in the current block, and the current block input from the machine pendant. In a numerical control device whose input value is the override value of An override value calculation unit that outputs a value, a speed acceleration/deceleration calculation unit that outputs a speed command when the next block and tool come into contact based on the override value at the corner and the commanded feed rate on the program, and an interpolation trajectory and the speed A corner override method for a numerical control device characterized by comprising an interpolation calculation unit that outputs a movement command calculated from a command. 2. Speed command F_1 when the next block and tool come into contact
is the override value OVR1 in the current block,
The method according to claim 1, which is calculated from the tool contact angle Φ_c before the corner, the tool contact angle Φ_1 at the corner, and the commanded feed rate F_c on the program using the formula: F_1=OVR1*(Φ_c/Φ_1)*F_c. Corner override method for numerical control equipment.